JP7115613B1 - Optimization analysis method, apparatus and program for joint position of car body - Google Patents

Abstract

A vehicle body joint position optimization analysis method, apparatus, and program for finding the optimum arrangement of joint points that minimizes the number of joint points while improving fatigue life and rigidity under variable load conditions. A vehicle body joint position optimization analysis method according to the present invention sets all or part of a vehicle body model as an analysis target model (S1), and densely sets joint candidate points in the analysis target model. The optimization analysis model 151 is generated (S3), the variable load condition is set (S5), the reciprocal of the predetermined target fatigue life is set as the target cumulative damage degree (S7), and the rigidity of the optimization analysis model 151 is improved. , reduction of the degree of cumulative damage, which is the reciprocal of the fatigue life of the joint candidate point 155, and minimization of the number of joint candidate points 155, are set as optimization analysis conditions (S9), and the fluctuating load conditions are subjected to optimization analysis. It is given to the model 151 and optimized analysis is performed to find the optimum arrangement of the junction points 157 that achieve the optimized analysis conditions (S13). [Selection diagram] Fig. 1

Description

TECHNICAL FIELD The present invention relates to an optimization analysis method, apparatus and program for a joint position of a vehicle body, and more particularly, to an optimum joint point optimization method for improving the rigidity of an automobile body and the fatigue life of joints that join components in the vehicle body. The present invention relates to an optimization analysis method, apparatus, and program for joint positions of a vehicle body for which positions are to be obtained.

In recent years, particularly in the automobile industry, weight reduction of vehicle bodies has been promoted due to environmental problems, and analysis by computer-aided engineering (hereinafter referred to as "CAE analysis") has become an indispensable technology for designing vehicle bodies.
It is known that in this CAE analysis, rigidity improvement and weight reduction can be achieved by using optimization techniques such as mathematical optimization, plate thickness optimization, shape optimization, and topology optimization.

A structure such as a car body is formed by joining a plurality of parts as an assembly by welding or the like. For example), it is known that the rigidity of the car body as a whole and the fatigue life of the joints are improved. However, from the viewpoint of the manufacturing cost of the vehicle body, it is desirable to reduce the amount of bonding as much as possible.

Therefore, in order to improve the rigidity of the car body and the fatigue life of the joints while suppressing the manufacturing cost of the car body, experience and intuition etc. There is a method of determining the bonding position by the method, and a method of setting the bonding position to the part where the stress is large by stress analysis.

However, the method of determining the joint position based on experience and intuition does not determine the position of the joint required to improve both rigidity and fatigue life. In some cases, it must be said that it is inefficient in terms of cost due to repeated trial and error.

In addition, in the method of increasing the number of joint points around the joint position where the stress is large by stress analysis, although there is a change in stiffness and fatigue life compared to before determining the joint position by this method, the stiffness and fatigue life only in the vicinity of the joint position Although the fatigue life is improved, there are many cases where the rigidity and fatigue life of other parts are relatively decreased, and when evaluating the entire vehicle body, the joint position obtained by this method cannot necessarily be said to be optimal.

In addition, when the positions of joints by spot welding are determined by the above method, if the positions of adjacent joints are too close, the current will flow to the adjacent joints welded first (shunt current), and the spot welding will occur next. Not enough current flows through the joint to be welded, resulting in a poor weld.

Therefore, Patent Literature 1 discloses a method of obtaining the optimum position of the junction point by spot welding using an optimization technique.

JP 2013-025593 A

However, the method disclosed in Patent Document 1 aims at improving the rigidity while minimizing the number of joints, and does not consider the improvement of the fatigue life of the joints by spot welding. rice field. Therefore, there has been a demand for a technique for finding an optimum joint position that can minimize the number of joints while improving the rigidity of the vehicle body and the fatigue life of the joints.

In addition, while the automobile is running, a fluctuating load whose amplitude, direction, etc. fluctuates in a complex manner and is not constant over time is input to the vehicle body. Therefore, there has been a demand for a technique for finding an optimum joint position that can improve the rigidity of the car body and the fatigue life of the joint when a complex fluctuating load is applied to the car body.

The present invention has been made to solve the above-mentioned problems. It is an object of the present invention to provide a joint position optimization analysis method, apparatus, and program for a vehicle body for finding the optimum position of joint points that minimizes the number of joint points while improving the number of joint points.

(1) A method for optimizing and analyzing a joint position of a vehicle body according to the present invention comprises a plurality of part models composed of beam elements, planar elements and/or three-dimensional elements, and joining the plurality of part models as a part assembly. A computer performs the following steps for all or part of an automobile body model having initial joints that An optimization analysis is performed to obtain an optimal arrangement of the junction points to achieve either improvement or minimization of the number of junction points,
an analysis target model setting step of setting all or part of the vehicle body model as an analysis target model;
an optimization analysis model generation step of generating an optimization analysis model by densely setting all connection candidate points that are candidates for the connection points of the optimal arrangement for the model to be analyzed;
Variable load condition setting for dividing the variable load applied to the optimization analysis model into load conditions of a plurality of different vibration patterns, and setting the variable load conditions as one sequence by combining the load conditions of the respective vibration patterns for a predetermined number of cycles. a step;
A target fatigue life setting step of setting the target fatigue life of the optimization analysis model by the number of sequences of the variable load condition;
In order to perform an optimization analysis that targets the optimization analysis model for optimization, the number of repetitions of fracture at each joint candidate point is obtained for each load condition of each vibration pattern, and the load condition of each vibration pattern is The sum of the ratio of the number of cycles and the number of repetitions to failure for the number of sequences of the variable load conditions set by the target fatigue life setting step is obtained as the cumulative damage degree of each candidate joint point, and the residual is obtained by optimization analysis. A condition relating to the degree of cumulative damage of the joint candidate points to be allowed, a condition relating to the stiffness of the optimization analysis model, and a condition relating to the number of points of the joint candidate points to be left by the optimization analysis are defined as an objective function or an optimization analysis condition setting step to be set as a constraint;
Giving the variable load condition set in the variable load condition setting step to the optimization analysis model, performing optimization analysis under the optimization analysis condition, reducing the cumulative damage degree of the joint candidate point, and performing the optimization analysis an optimization analysis step of determining the arrangement of the joint candidate points for the purpose of either improving the rigidity of the model or minimizing the number of the remaining joint candidate points as the optimum arrangement of the joint points. It is characterized by

(2) In the above (1),
The optimization analysis step performs topology optimization by a density method, and is characterized by discretizing the topology optimization by setting a penalty coefficient to 4 or more.

(3) A method for optimizing and analyzing joint positions of a vehicle body according to the present invention comprises a plurality of part models composed of beam elements, planar elements and/or three-dimensional elements, and joining the plurality of part models as a part assembly. A computer performs the following steps for all or part of an automobile body model having initial joints that An optimization analysis is performed to obtain an optimal arrangement of the junction points to achieve either improvement or minimization of the number of junction points,
an analysis target model setting step of setting all or part of the vehicle body model as an analysis target model;
an optimization analysis model generation step of generating an optimization analysis model by densely setting all connection candidate points that are candidates for the connection points of the optimal arrangement for the model to be analyzed;
Variable load condition setting for dividing the variable load applied to the optimization analysis model into load conditions of a plurality of different vibration patterns, and setting the variable load conditions as one sequence by combining the load conditions of the respective vibration patterns for a predetermined number of cycles. a step;
A target fatigue life setting step of setting the target fatigue life of the optimization analysis model by the number of sequences of the variable load condition;
In order to perform an optimization analysis that targets the optimization analysis model for optimization, the number of repetitions of fracture at each joint candidate point is obtained for each load condition of each vibration pattern, and the load condition of each vibration pattern is The sum of the ratio of the number of cycles and the number of repetitions to failure for the number of sequences of the variable load conditions set by the target fatigue life setting step is obtained as the cumulative damage degree of each candidate joint point, and the residual is obtained by optimization analysis. A condition relating to the degree of cumulative damage of the joint candidate points to be allowed, a condition relating to the stiffness of the optimization analysis model, and a condition relating to the number of points of the joint candidate points to be left by the optimization analysis are defined as an objective function or an optimization analysis condition setting step to be set as a constraint;
Giving the variable load condition set in the variable load condition setting step to the optimization analysis model, performing optimization analysis under the optimization analysis condition, reducing the cumulative damage degree of the joint candidate point, and performing the optimization analysis an optimization analysis step of retaining the arrangement of the candidate joint points for the purpose of either improving the rigidity of the model or minimizing the number of the remaining candidate joint points as a provisional optimal arrangement of the joint points;
A predetermined number of joint candidate points are selected from the joint candidate points remaining as a provisional optimal arrangement by the optimization analysis, and the selected joint candidate points are set in the analysis target model instead of the initial joint points. a selected junction candidate point setting analysis target model generation step of generating a selected junction candidate point setting analysis target model by
Stress analysis is performed by giving the load condition and constraint condition of each vibration pattern under the variable load condition set in the variable load condition setting step to the selected joint candidate point setting analysis target model, and using the result of the stress analysis a selected joint candidate point performance calculation step of calculating the fatigue life of the selected joint candidate point under the variable load condition and the stiffness of the selected joint candidate point setting analysis target model;
The fatigue life of the joint candidate point in the selected joint candidate point setting analysis target model under the variable load condition and the stiffness of the selected joint candidate point setting analysis target model are the same as the analysis target model in which the initial joint point is set. a determination step of determining whether or not a predetermined performance exceeding is satisfied;
If it is determined in the determination step that the predetermined performance is satisfied, the arrangement of the selected joint candidate points is determined as the optimum layout of the joint points, and in the determination step it is determined that the predetermined performance is not satisfied. If it is, until the predetermined performance is satisfied, the condition regarding the cumulative damage degree of the joint candidate point to remain by the optimization analysis set in the optimization analysis condition setting step, the condition regarding the rigidity of the optimization analysis model, or changing a condition regarding the number of points of the joint candidate points to be left by the optimization analysis, the optimization analysis step, the selected joint candidate setting analysis target model generation step, the selected joint candidate point performance calculation step, and an optimum joint point determination step of repeating the determination step and determining the arrangement of the joint candidate points selected when the predetermined performance is satisfied as the optimum arrangement of the joint points. be.

(4) A vehicle body joint position optimization analysis apparatus according to the present invention comprises a plurality of part models made up of beam elements, planar elements and/or three-dimensional elements, and joins the plurality of part models as a part assembly. For all or part of an automobile body model having initial joint points that An optimization analysis is performed to find the optimum arrangement of the junction points for the purpose of achieving any one of
an analysis target model setting unit that sets all or part of the vehicle body model as an analysis target model;
an optimization analysis model generating unit for generating an optimization analysis model by densely setting all connection candidate points that are candidates for the connection points of the optimal placement for the model to be analyzed;
Variable load condition setting for dividing the variable load applied to the optimization analysis model into load conditions of a plurality of different vibration patterns, and setting the variable load conditions as one sequence by combining the load conditions of the respective vibration patterns for a predetermined number of cycles. Department and
a target fatigue life setting unit that sets the target fatigue life of the optimization analysis model by the number of sequences of the variable load condition;
In order to perform an optimization analysis that targets the optimization analysis model for optimization, the number of repetitions of fracture at each joint candidate point is obtained for each load condition of each vibration pattern, and the load condition of each vibration pattern is The sum of the ratio of the number of cycles and the number of repetitions to failure for the number of sequences of the variable load condition set by the target fatigue life setting unit is obtained as the cumulative damage degree of each candidate joint point, and the residual is obtained by optimization analysis. A condition relating to the degree of cumulative damage of the joint candidate points to be allowed, a condition relating to the stiffness of the optimization analysis model, and a condition relating to the number of points of the joint candidate points to be left by the optimization analysis are defined as an objective function or an optimization analysis condition setting unit that is set as a constraint;
Giving the variable load condition set by the variable load condition setting unit to the optimization analysis model, performing optimization analysis under the optimization analysis condition, reducing the cumulative damage degree of the joint candidate point, and optimizing an optimization analysis unit that obtains the arrangement of the candidate joint points for the purpose of either improving the rigidity of the analysis model or minimizing the number of the candidate joint points to be left as the optimum arrangement of the joint points. It is characterized by

(5) In the above (4),
The optimization analysis unit performs topology optimization by a density method, and is characterized by setting a penalty coefficient to 4 or more in the topology optimization for discretization.

(6) A vehicle body joining position optimization analysis apparatus according to the present invention comprises a plurality of part models composed of beam elements, planar elements and/or three-dimensional elements, and joins the plurality of part models as a part assembly. For all or part of an automobile body model having initial joint points that An optimization analysis is performed to find the optimum arrangement of the junction points for the purpose of achieving any one of
an analysis target model setting unit that sets all or part of the vehicle body model as an analysis target model;
an optimization analysis model generating unit for generating an optimization analysis model by densely setting all connection candidate points that are candidates for the connection points of the optimal placement for the model to be analyzed;
Variable load condition setting for dividing the variable load applied to the optimization analysis model into load conditions of a plurality of different vibration patterns, and setting the variable load conditions as one sequence by combining the load conditions of the respective vibration patterns for a predetermined number of cycles. Department and
a target fatigue life setting unit that sets the target fatigue life of the optimization analysis model by the number of sequences of the variable load condition;
In order to perform an optimization analysis that targets the optimization analysis model for optimization, the number of repetitions of fracture at each joint candidate point is obtained for each load condition of each vibration pattern, and the load condition of each vibration pattern is The sum of the ratio of the number of cycles and the number of repetitions to failure for the number of sequences of the variable load condition set by the target fatigue life setting unit is obtained as the cumulative damage degree of each candidate joint point, and the residual is obtained by optimization analysis. a condition relating to the degree of cumulative damage of the joint candidate points to be allowed, a condition relating to the stiffness of the optimization analysis model, and a condition relating to the number of the joint candidate points to be left in the optimization analysis, as an objective function or an optimization analysis condition setting unit that is set as a constraint;
Giving the variable load condition set by the variable load condition setting unit to the optimization analysis model, performing optimization analysis under the optimization analysis condition, reducing the cumulative damage degree of the joint candidate point, and optimizing an optimization analysis unit that retains, as a provisional optimum arrangement of the joint points, the arrangement of the joint candidate points that is achieved for the purpose of either improving the rigidity of the analysis model or minimizing the number of the remaining joint candidate points; ,
A predetermined number of joint candidate points are selected from the joint candidate points remaining as a provisional optimal arrangement by the optimization analysis, and the selected joint candidate points are set in the analysis target model instead of the initial joint points. a selected junction candidate point setting analysis target model generation unit for generating a selected junction candidate point setting analysis target model by
Stress analysis is performed by giving the load condition and constraint condition of each vibration pattern under the variable load condition set by the variable load condition setting unit to the selected joint candidate point setting analysis target model, and the result of the stress analysis is used. a selected joint candidate point performance calculation unit that calculates the fatigue life of the selected joint candidate point under the variable load condition and the stiffness of the selected joint candidate point setting analysis target model;
The fatigue life of the joint candidate point in the selected joint candidate point setting analysis target model under the variable load condition and the stiffness of the selected joint candidate point setting analysis target model are the same as the analysis target model in which the initial joint point is set. a determination unit that determines whether or not a predetermined performance exceeding is satisfied;
When the determination unit determines that the predetermined performance is satisfied, the arrangement of the selected joining candidate points is determined as the optimal placement of the joining points, and the determination unit determines that the predetermined performance is not satisfied. if it is, until the predetermined performance is satisfied, the condition regarding the cumulative damage degree of the joint candidate point to be left by the optimization analysis set by the optimization analysis condition setting unit, the condition regarding the rigidity of the optimization analysis model, Alternatively, by changing the condition regarding the points of the joint candidate points to be left by the optimization analysis, the optimization analysis unit, the selected joint candidate point setting analysis target model generation unit, the selected joint candidate point performance calculation unit, and an optimum joint point determination unit that repeats the processing by the determination unit and determines the arrangement of the joint candidate points selected when the predetermined performance is satisfied as the optimum arrangement of the joint points. and

(7) A vehicle body joint position optimization analysis program according to the present invention comprises a plurality of part models composed of beam elements, planar elements and/or three-dimensional elements, and joins the plurality of part models as a part assembly. For all or part of an automobile body model having initial joint points that An optimization analysis is performed to find the optimum arrangement of the junction points for the purpose of achieving any one of
the computer,
an analysis target model setting unit that sets all or part of the vehicle body model as an analysis target model;
an optimization analysis model generating unit for generating an optimization analysis model by densely setting all connection candidate points that are candidates for the connection points of the optimal placement for the model to be analyzed;
Variable load condition setting for dividing the variable load applied to the optimization analysis model into load conditions of a plurality of different vibration patterns, and setting the variable load conditions as one sequence by combining the load conditions of the respective vibration patterns for a predetermined number of cycles. Department and
a target fatigue life setting unit that sets the target fatigue life of the optimization analysis model by the number of sequences of the variable load condition;
In order to perform an optimization analysis that targets the optimization analysis model for optimization, the number of repetitions of fracture at each joint candidate point is obtained for each load condition of each vibration pattern, and the load condition of each vibration pattern is The sum of the ratio of the number of cycles and the number of repetitions to failure for the number of sequences of the variable load condition set by the target fatigue life setting unit is obtained as the cumulative damage degree of each candidate joint point, and the residual is obtained by optimization analysis. A condition relating to the degree of cumulative damage of the joint candidate points to be allowed, a condition relating to the stiffness of the optimization analysis model, and a condition relating to the number of points of the joint candidate points to be left by the optimization analysis are defined as an objective function or an optimization analysis condition setting unit that is set as a constraint;
Giving the variable load condition set by the variable load condition setting unit to the optimization analysis model, performing optimization analysis under the optimization analysis condition, reducing the cumulative damage degree of the joint candidate point, and optimizing an optimization analysis unit that obtains the arrangement of the joint candidate points for the purpose of either improving the rigidity of the analysis model or minimizing the number of the remaining joint candidate points as the optimum arrangement of the joint points; It is characterized by having a function to be executed.

(8) In the above (7),
The optimization analysis unit performs topology optimization by a density method, and is characterized by setting a penalty coefficient to 4 or more in the topology optimization for discretization.

(9) A vehicle body joint position optimization analysis program according to the present invention comprises a plurality of part models composed of beam elements, planar elements and/or three-dimensional elements, and joins the plurality of part models as a part assembly. For all or part of an automobile body model having initial joint points that An optimization analysis is performed to find the optimum arrangement of the junction points for the purpose of achieving any one of
the computer,
an analysis target model setting unit that sets all or part of the vehicle body model as an analysis target model;
an optimization analysis model generating unit for generating an optimization analysis model by densely setting all connection candidate points that are candidates for the connection points of the optimal placement for the model to be analyzed;
Variable load condition setting for dividing the variable load applied to the optimization analysis model into load conditions of a plurality of different vibration patterns, and setting the variable load conditions as one sequence by combining the load conditions of the respective vibration patterns for a predetermined number of cycles. Department and
a target fatigue life setting unit that sets the target fatigue life of the optimization analysis model by the number of sequences of the variable load condition;
In order to perform an optimization analysis that targets the optimization analysis model for optimization, the number of repetitions of fracture at each joint candidate point is obtained for each load condition of each vibration pattern, and the load condition of each vibration pattern is The sum of the ratio of the number of cycles and the number of repetitions to failure for the number of sequences of the variable load condition set by the target fatigue life setting unit is obtained as the cumulative damage degree of each candidate joint point, and the residual is obtained by optimization analysis. a condition relating to the degree of cumulative damage of the joint candidate points to be allowed, a condition relating to the stiffness of the optimization analysis model, and a condition relating to the number of the joint candidate points to be left in the optimization analysis, as an objective function or an optimization analysis condition setting unit that is set as a constraint;
Giving the variable load condition set by the variable load condition setting unit to the optimization analysis model, performing optimization analysis under the optimization analysis condition, reducing the cumulative damage degree of the joint candidate point, and optimizing an optimization analysis unit that retains, as a provisional optimum arrangement of the joint points, the arrangement of the joint candidate points that is achieved for the purpose of either improving the rigidity of the analysis model or minimizing the number of the remaining joint candidate points; ,
A predetermined number of joint candidate points are selected from the joint candidate points remaining as a provisional optimal arrangement by the optimization analysis, and the selected joint candidate points are set in the analysis target model instead of the initial joint points. a selected junction candidate point setting analysis target model generation unit for generating a selected junction candidate point setting analysis target model by
Stress analysis is performed by giving the load condition and constraint condition of each vibration pattern under the variable load condition set by the variable load condition setting unit to the selected joint candidate point setting analysis target model, and the result of the stress analysis is used. a selected joint candidate point performance calculation unit that calculates the fatigue life of the selected joint candidate point under the variable load condition and the stiffness of the selected joint candidate point setting analysis target model;
The fatigue life of the joint candidate point in the selected joint candidate point setting analysis target model under the variable load condition and the stiffness of the selected joint candidate point setting analysis target model are the same as the analysis target model in which the initial joint point is set. a determination unit that determines whether or not a predetermined performance exceeding is satisfied;
When the determination unit determines that the predetermined performance is satisfied, the arrangement of the selected joining candidate points is determined as the optimal placement of the joining points, and the determination unit determines that the predetermined performance is not satisfied. if it is, until the predetermined performance is satisfied, the condition regarding the cumulative damage degree of the joint candidate point to be left by the optimization analysis set by the optimization analysis condition setting unit, the condition regarding the rigidity of the optimization analysis model, Alternatively, by changing the condition regarding the points of the joint candidate points to be left by the optimization analysis, the optimization analysis unit, the selected joint candidate point setting analysis target model generation unit, the selected joint candidate point performance calculation unit, an optimum joint point determination unit for repeating the processing by the determination unit and determining the arrangement of the joint candidate points selected when the predetermined performance is satisfied as the optimum arrangement of the joint points; It is characterized by having

In the present invention, all or part of a vehicle body model of an automobile is used as a model to be analyzed, and an optimization analysis model is generated in which joint candidate points for joining parts as a set of parts are set for the model to be analyzed. Optimization analysis of joint candidate points by setting the number of joint candidate points, fatigue life of joint candidate points, stiffness of the optimization analysis model, and optimization analysis conditions (objective function or constraint conditions) related to the number of joint points By doing this, when a variable load that is not constant over time is input to the car body, such as when an actual car is running, the number of joint candidate points can be minimized, the rigidity of the model to be analyzed can be improved, and parts can be assembled. It is possible to determine the optimum position of the joints that can be achieved with the aim of either improving the fatigue life of the joints to be joined.
As a result, it is possible to optimize the placement of spot welding positions in the vehicle body structure, improve the fatigue life of spot welding, and improve the rigidity of the vehicle body, thereby reducing welding costs and increasing the rigidity and weight of the vehicle body.

1 is a block diagram of an optimization analysis device for a joint position of a vehicle body according to Embodiment 1 of the present invention; FIG. FIG. 4 is a diagram showing an example of a floor model as a model to be analyzed, load conditions (moment about FR axis) and constraint conditions of a first vibration pattern given to the floor model in Embodiment 1 of the present invention. . FIG. 2 is a diagram for explaining initial joint points preset in a floor model as an example of a model to be analyzed in Embodiment 1 of the present invention ((a) perspective view, (b) interval between initial joint points); . FIG. 4 is a diagram showing an example of load conditions (moment about the RL axis) and constraint conditions of a second vibration pattern applied to a floor part model, which is a model to be analyzed, in Embodiment 1 of the present invention. A diagram showing an example of an optimization analysis model in which initial junction points preset in an analysis target model and additional junction points densely added to the analysis target model are set as junction candidate points in Embodiment 1 of the present invention. ((a) optimization analysis model, (b) junction candidate points set in optimization analysis model). It is a figure which shows an example of the variable load condition set in Embodiment 1 of this invention. FIG. 4 is a diagram for explaining an S-N diagram used for calculating fatigue life under fluctuating load conditions in Embodiment 1; In Embodiment 1 of the present invention, a diagram showing an example of the fatigue life of the initial joint point under fluctuating load conditions and the position of the initial joint point of the shortest three points of fatigue life (shortest fatigue life). be. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing an example of a spot-welded portion in which an initial joint point is modeled in calculating the fatigue life of the initial joint point in Embodiment 1 of the present invention ((a) top view, (b) perspective view). In Embodiment 1 and Example 1 of the present invention, the floor part model is the analysis object, and the diagram showing an example of the optimum arrangement of the joint points obtained by the optimization analysis in which the optimization analysis conditions regarding rigidity and fatigue life are set. ((a) perspective view, (b) enlarged view of dotted frame). FIG. 4 is a flow chart showing the flow of processing in the method for optimizing and analyzing the joining position of the vehicle body according to Embodiment 1 of the present invention; FIG. 7 is a block diagram of an optimization analysis apparatus for a joint position of a vehicle body according to Embodiment 2 of the present invention; FIG. 10 is a flowchart showing the flow of processing in a method for optimizing and analyzing a joining position of a vehicle body according to Embodiment 2 of the present invention; FIG. 2 is a diagram showing a floor model, which is a part of the vehicle body model to be analyzed in Example 1 ((a) General view, (b) Enlarged view near stiffness evaluation points for evaluating stiffness). FIG. 10 is a diagram showing the optimum arrangement of joint points obtained by the optimization analysis in which the floor model is the analysis object and the optimization analysis conditions related to stiffness are set in the first embodiment. 4 is a graph showing the rigidity improvement rate of the floor model for which the optimum arrangement of joint points determined by the optimization analysis is set in Example 1. FIG. In Example 1, based on the shortest fatigue life of the initial joint points in the floor model in which only the initial joint points are set, the ratio of the shortest fatigue life of the joint points in the floor model in which the optimum arrangement of the joint points is set is calculated. It is a graph showing. In Example 2, it is a diagram for explaining the vehicle body model to be analyzed and the fluctuating load conditions given in the joint point optimization analysis ((a) load conditions and constraint conditions of the first vibration pattern, (b ) load conditions and restraint conditions of the second vibration pattern). In Example 2, (a) the shortest fatigue life ratio of the vehicle body model in which the joint points obtained by the optimization analysis are set for each of the conditions 1 to 3 in which the combination of the objective function and the constraint conditions of the optimization analysis conditions is changed, It is a graph which shows the result of (b) rigidity improvement rate and (c) number of junction points.

Before describing the optimization analysis method, apparatus, and program for the joint position of the vehicle body according to Embodiments 1 and 2 of the present invention, a vehicle body model targeted by the present invention will be described.
In the specification and drawings of the present application, the longitudinal direction of the vehicle body, the lateral direction of the vehicle body, and the vertical direction of the vehicle body are expressed as the X direction, the Y direction, and the Z direction, respectively.
In addition, in the present specification and drawings, elements having substantially the same functions and configurations are denoted by the same reference numerals, thereby omitting redundant description.

<Car body model and model to be analyzed>
The vehicle body model targeted in the present invention is composed of a plurality of part models such as vehicle body frame parts and chassis parts. has been made

In general, body frame parts, chassis parts, and the like are mainly made of thin metal plates, so the part models that make up the body model may be composed only of planar elements.

Furthermore, the vehicle body model has initial joint points for joining a plurality of part models as a part assembly. The initial joint points are modeled by using beam elements and three-dimensional elements for spot welding points where a plurality of automobile parts are joined as an assembly.

For example, when two part models composed of plane elements are joined by an initial joint point modeled by a beam element, the beam elements are joined to both plane elements of the two part models.

In addition, when the initial joint point is modeled by a solid element, the planar element of the part model and the solid element of the initial joint point are rigid bodies in order to distribute the translational force acting on the initial joint point to the part model. connected by elements.

Since the present invention analyzes the deformation caused by the application of a fluctuating load to an analysis target model (described later) that is the whole or a part of a vehicle body model, each part model in the vehicle body model is an elastic body or a viscoelastic body. Or it is modeled as an elastic plastic body.
The material properties and element information of each part model that constitutes the vehicle body model, as well as information on the initial joint points of each part set, etc., are stored in the vehicle body model file 101 (see FIGS. 1 and 12).

[Embodiment 1]
<Optimization analysis device for joint position of car body>
The configuration of the vehicle body joining position optimization analysis apparatus (hereinafter simply referred to as "optimization analysis apparatus") according to Embodiment 1 of the present invention will be described below.

The optimization analysis device uses all or part of a vehicle body model as a model to be analyzed, and improves the rigidity of the vehicle body model, improves the fatigue life of joints that join parts in the car body model, and increases the number of joint points. It is a device that performs optimization analysis to find the optimum arrangement of junctions for the purpose of either minimizing .

FIG. 1 shows an example of the configuration of an optimization analysis device 1 according to the first embodiment. The optimization analysis device 1 is configured by a PC (personal computer) or the like, and has a display device 3, an input device 5, a storage device 7, a working data memory 9, and an arithmetic processing unit 11, as shown in FIG. there is
The display device 3, the input device 5, the storage device 7, and the work data memory 9 are connected to the arithmetic processing section 11, and their respective functions are executed by commands from the arithmetic processing section 11. FIG.
The function of each component of the optimization analysis device 1 according to the first embodiment will be described below.

≪Display device≫
The display device 3 is used to display a vehicle body model, a model to be analyzed, analysis results, etc., and is composed of a liquid crystal monitor or the like.

≪Input device≫
The input device 5 is used for inputting instructions by an operator such as reading the vehicle body model file 101 (FIG. 1) and displaying the vehicle body model and the model to be analyzed.

≪Storage device≫
The storage device 7 is used to store various files such as the vehicle body model file 101 (FIG. 1) and the analysis results, and is composed of a hard disk or the like.

≪Work data memory≫
The working data memory 9 is used for temporary storage of data used by the arithmetic processing unit 11 and for arithmetic operations, and is composed of a RAM (Random Access Memory) or the like.

≪Arithmetic processing section≫
As shown in FIG. 1, the arithmetic processing unit 11 includes an analysis target model setting unit 13, an optimization analysis model generation unit 15, a fluctuating load condition setting unit 17, a target fatigue life setting unit 19, and an optimization analysis condition It has a setting unit 21 and an optimization analysis unit 23, and is configured by a CPU (central processing unit) such as a PC. Each of these units functions when the CPU executes a predetermined program.
The function of each section of the arithmetic processing section 11 will be described below.

(Analysis target model setting part)
The analysis target model setting unit 13 acquires a vehicle body model from the vehicle body model file 101, and sets all or part of the acquired vehicle body model as an analysis target model.

An example of processing by the analysis target model setting unit 13 will be described below.
First, the operator instructs the reading of the vehicle body model from the vehicle body model file 101 through the input device 5 , and the vehicle body model is read from the storage device 7 .
Next, the vehicle body model is displayed on the display device 3 according to the operator's instruction.
Then, according to an instruction from the operator, a part of the vehicle body model displayed on the display device 3 is designated as the target of the optimization analysis. The analysis target model setting unit 13 sets the designated part as the analysis target model.

FIG. 2 shows an example in which a floor part model 111, which is a simplified model of the floor part, which is a part of the vehicle body, is set as the model to be analyzed.

The floor section model 111 has, as component models, a floor panel model 113, a tunnel model 115, a locker inner model 117, a rocker outer model 119, a front floor cloth model 121, and a rear floor cloth model 123. It is configured. Both the inner rocker model 117 and the outer rocker model 119 are formed by connecting three members extending in the longitudinal direction of the vehicle body.

As shown in FIG. 3, these part models have initial joint points 131 that are joined as a set of parts at predetermined intervals P in advance. The initial joint point 131 is modeled by, for example, a beam element that connects nodes such as planar elements of a plurality of part models that constitute a part assembly.

2 and 4, the floor panel model 113 and the tunnel model in the floor model 111 are set in order to set the variable load conditions and constraint conditions to be applied to the floor model 111 by the variable load condition setting unit 17, which will be described later. A front end surface and a rear end surface of 115 are respectively connected with a rigid element to generate a front end surface portion 125 and a rear end surface portion 127 .
Here, the center of gravity of the front end face portion 125 is the load input point A, which is coupled to the front end face portion 125 by a rigid element, and the center of gravity of the rear end face portion 127 is the constraint point B.
The axis in the longitudinal direction of the vehicle body (X direction in FIG. 2) passing through the load input point A is defined as the FR axis, and the axis in the lateral direction of the vehicle body (Y direction in FIG. 4) is defined as the RL axis.

(Optimization analysis model generator)
The optimization analysis model generation unit 15 densely sets all candidate connection points, which are candidates for the connection points of the optimal arrangement for connecting the assembly of parts to the model to be analyzed, and generates an optimization analysis model. .

FIG. 5 shows, as an example, an optimization analysis model 151 generated by setting joint candidate points 155 in the floor model 111 .

In the floor section model 111, as shown in FIG. 3, initial joint points 131 are set in advance at predetermined intervals P in a set of parts formed by joining a plurality of parts.

As shown in FIG. 5, the optimization analysis model generation unit 15 densely sets additional joint points 153 at a predetermined interval p (<P) between the initial joint points 131 in each component assembly. Then, both the initial joint point 131 and the additional joint point 153 preset in the floor part model 111 are set as joint candidate points 155 to generate the optimization analysis model 151 .

In addition, as a procedure for setting the joint candidate points by the optimization analysis model generation unit 15, it is necessary to set the intervals at which the additional joint points can actually be increased such that current shunting does not occur at the adjacent joint points. It is preferable to set the additional joint points according to the size of the parts to be joined as a set of parts in the model to be analyzed, such as increasing the density.

Further, the additional joint point may be modeled with a beam element or a three-dimensional element in the same manner as the initial joint point described above.

Hereinafter, in Embodiment 1, as shown in FIG. 5, an optimization analysis model 151 generated by setting additional junction points 153 in the floor section model 111 will be described.

(Variable load condition setting section)
The fluctuating load condition setting unit 17 divides the fluctuating load applied to the optimization analysis model into load conditions of a plurality of different vibration patterns, and combines the load conditions of each vibration pattern for a predetermined number of cycles to form one sequence of fluctuating load conditions. is set.

Fluctuating load is the load input to the model to be analyzed, which is divided into vibration patterns that differ in one or more of the magnitude, position, and direction, and each vibration pattern is combined for a predetermined number of cycles. It simulates the time-varying load that is input to the vehicle body when the vehicle is running. The fluctuating load condition is given in the calculation of the fatigue life of initial joint points and joint candidate points, which will be described later.

The fluctuating load condition setting unit 17 divides the fluctuating load into a plurality of loads with different vibration patterns, and sets a fluctuating load condition that combines these loads and a constraint condition that constrains the model to be analyzed for each fluctuating load condition. You may

In Embodiment 1, the fluctuating load condition is the first vibration in which a load (moment) that twists around the FR axis as shown in FIG. A pattern load condition and a second vibration pattern load condition in which a twisting load (moment) about the RL axis as shown in FIG. 4 is input.

As shown in FIG. 6, the fluctuating load condition is a fluctuating load condition of one sequence by combining the load condition of the first vibration pattern for 1 cycle and the load condition of the second vibration pattern for 20 cycles. Here, the graph shown in FIG. 6 shows the number of cycles of each of the load conditions of the first vibration pattern and the load condition of the second vibration pattern under the variable load condition of one sequence. FIG. 10 is a graph schematically showing a double swinging fluctuating load having an amplitude equal to the magnitude of the load under each of the load condition and the load condition of the second vibration pattern; FIG.

Note that the fluctuating load conditions shown as an example in FIG. 6 have amplitudes of 0.7 kN·m and 1.4 kN corresponding to the load condition of the first vibration pattern and the load condition of the second vibration pattern, respectively.

Further, in the first embodiment, as shown in FIGS. 2 and 4, the constraint condition is that the constraint point B of the floor part model 111 is completely constrained.

(Target fatigue life setting section)
The target fatigue life setting section 19 sets the target fatigue life of the optimization analysis model by the number of sequences of the variable load condition.

As the target fatigue life of the optimized analysis model, stress analysis is performed separately by giving the load condition of the vibration pattern under the variable load condition set by the variable load condition setting unit 17 to the model to be analyzed, and the result of the stress analysis is calculated. is used to calculate the number of sequences leading to fracture (fatigue fracture) under variable load conditions at the initial joint of the model to be analyzed as the fatigue life, and the target fatigue life is set based on the calculated fatigue life of the initial joint. good too. Alternatively, based on conventional empirical rules, a predetermined number of sequences may be set as the target fatigue life of the optimization analysis model.

In general, the load applied to the actual car body is not constant over time, so it can be regarded as a stress state in which stress with various amplitudes is randomly generated even at the initial joint. The cumulative fatigue damage rule is used to evaluate the fatigue life of the initial joint under such stress conditions.

In the cumulative fatigue damage law, first, the state in which stresses with various amplitudes are randomly generated is assumed to be repeated stresses with different _amplitudes such as σ ₁ , σ ₂ , σ ₃ . think.
Next, assuming that _each stress amplitude _{σ 1} , σ ₂ , σ ₃ , . N ₂ , N ₃ . . . N _m are read from the SN diagram as shown in FIG.
The degree of damage when _each of these stress _amplitudes is _{repeated n 1 , n 2 , n 3} . Think _m .

In the cumulative fatigue damage law, as shown in Equation (1), the cumulative damage degree dm, which is the sum of damage degrees at individual stress amplitudes, is obtained. Then, when the cumulative damage degree dm≧1, fatigue fracture occurs.
In addition, under fluctuating load conditions under irregular repeated fluctuating loads, each stress amplitude σ ₁ , σ ₂ , σ ₃ , . . . σ _m and the number of repetitions n ₁ , n ₂ , n ₃ ... _nm may be determined.

A specific procedure for calculating the target cumulative damage degree of the initial joint under fluctuating load conditions by the target fatigue life setting unit 19 is as follows.

First, the stress acting on each initial joint point obtained by performing stress analysis for each load condition of each vibration pattern under variable load conditions is defined as the different stress amplitudes σ ₁ and σ ₂ , σ ₃ ·σ _m .

Next, the target fatigue life setting unit 19 sets the number of repetitions (number of repetitions to fracture) N ₁ , N 2 , N 2 , N 1 , N ₂ , N ₃ , . . . N _m are obtained from the SN diagram (FIG. 7).

そして、累積損傷度DMが1以上となるときのシークエンス回数Kを、変動荷重条件下での初期接合点の疲労寿命として算出する。 Next, the number of repetitions until fracture at each stress amplitude (number of _repetitions to fracture) N ₁ , N ₂ , N ₃ , . ₁ , _{n 2} , n ₃ , . Furthermore, the cumulative damage degree DM when one sequence under the variable load condition is continuously repeated K times (K sequence) is calculated from Equation (2).

Then, the number of times of sequence K when the cumulative damage degree DM becomes 1 or more is calculated as the fatigue life of the initial joint point under fluctuating load conditions.

Based on the fatigue life of each initial joint point 131 thus calculated, the target fatigue life setting unit 19 sets the target fatigue life.
The target fatigue life is the fatigue life that the remaining joint candidate points (described later) should satisfy by the optimization analysis. In Embodiment 1, the target fatigue life is at least the longest fatigue life (shortest fatigue life) among the initial joint points calculated by the target fatigue life setting unit 19 .

FIG. 8 shows the initial fatigue life of the lowest three points among the fatigue life of the initial joint 131 obtained using the results of stress analysis in which the variable load conditions and restraint conditions shown in FIG. 6 are applied to the floor model 111 An example of the location of the joint and its fatigue life results is shown.

The fatigue life of the initial joint point 131 shown in FIG. Calculations were made under a variable load condition (Fig. 4) in which a moment of 1.4 kN·m around the RL axis is combined with 20 cycles in both swings to form one sequence. A specific procedure for calculating the target fatigue life of the initial joint 131 will be described in Example 1 below.

The fatigue life obtained for each initial joint point 131 of the floor part model 111 is, as shown in FIG. and the fatigue life of the initial joint 131 of the site D where the floor panel model 113 and the rear floor cross model 123 are joined is 22900 sequences, and the initial joint of the site E where the tunnel model 115 and the rear floor cross model 123 are joined. The fatigue life of point 131 was 24900 sequences.
Based on this result, the target fatigue life setting unit 19 sets a longer fatigue life than the fatigue life of the initial joint 131 at the site C as the target fatigue life.

In calculating the fatigue life of the initial joint point by the target fatigue life setting unit 19, based on the nugget diameter of the actual spot weld point, like the spot weld 141 illustrated in FIG. It is preferable to set the sites (central portion 147 and peripheral portion 149) to which the beam element 145 is coupled, cut the web-shaped planar element again, and use the stress value of the planar element in the peripheral portion 149. FIG.

Further, for calculating the fatigue life by the target fatigue life setting section 19, it is preferable to use commercially available fatigue life prediction analysis software. For example, when calculating the fatigue life of the initial joint modeled with beam elements using commercially available fatigue life prediction analysis software, the conditions such as the stress of the initial joint must be input into the fatigue life prediction analysis software. can calculate the fatigue life of the initial joint. As the stress at the initial joint point, the stress value of the plane element of each part model to which the beam element is connected, or the nominal structural stress obtained from the force and moment acting on both ends of the beam element can be used.

In addition, the SN diagram may change depending on the loading state of the load, for example, whether the average stress is compressive stress or tensile stress even if the stress amplitude is the same. Experimental values can be referred to. Alternatively, when calculating fatigue life using nominal structural stress, a single SN diagram containing different loading conditions may be used.
Furthermore, as shown in Fig. 7, the SN diagram applies various rules such as Miner's rule, which does not judge fracture below the fatigue limit on the low stress side, and modified Miner's rule, which counts even below the fatigue limit as damage. It may be expressed as

(Optimization analysis condition setting section)
The optimization analysis condition setting unit 21 sets each joint candidate point for each load condition of each vibration pattern set by the fluctuating load condition setting unit 17 in order to perform an optimization analysis targeting the optimization analysis model. and the sum of the ratio of the number of cycles of the load condition of each vibration pattern and the number of repetitions of the fracture to the number of sequences of the fluctuating load conditions set by the target fatigue life setting unit 19 is calculated as the above-mentioned candidate joint points. is obtained as the cumulative damage degree DM of, and the conditions related to the cumulative damage degree of the joint candidate points left by the optimization analysis, the conditions related to the stiffness of the optimization analysis model, the conditions related to the number of joint candidate points left by the optimization analysis, is set as an objective function or constraint condition, which is an optimization analysis condition.

There are two types of optimization analysis conditions: an objective function and constraints.
Only one objective function is set according to the objective of the optimization analysis. In Embodiment 1, the condition regarding the stiffness of the optimization analysis model is set as the objective function.

As a condition regarding stiffness, for example, a predetermined position in the model to be analyzed may be set as a stiffness evaluation point, and displacement or strain at the stiffness evaluation point may be used as an index. Under variable load conditions, for example, the sum of the displacements of the stiffness evaluation point P under the load conditions of each vibration pattern is minimized, or the displacement of the stiffness evaluation point P under the load conditions of each vibration pattern is minimized. can be used as a condition for stiffness.

Constraints are constraints imposed upon performing optimization analysis, and a plurality of constraints are set as necessary.

In Embodiment 1, the condition that the fatigue life of the joint candidate point is longer than the target fatigue life set by the target fatigue life setting unit 19 may be set as a constraint condition.
The number of repetitions of fracture at the joint candidate point can be calculated using the SN diagram shown in FIG.

In addition, the condition regarding fatigue life is not limited to the target fatigue life set by the target fatigue life setting unit 19 as a constraint condition. A constraint condition may be given such that the cumulative damage degree DM for the number of sequences set as the fatigue life is less than 1 so that fatigue failure does not occur.

Here, the cumulative damage degree DM of the joint candidate point is calculated from, for example, the stress of the planar element of the part model to which the beam element modeled as the joint candidate point is connected, and the force and moment acting on both ends of the beam element. Using the nominal structural stress, etc., it can be calculated using the S-N diagram shown in FIG.

Further, as a condition regarding the score of the joining candidate point, the score of the remaining joining candidate point can be set to a predetermined value. In Embodiment 1, a constraint condition is set such that the number of remaining joint candidate points is the same as the number of initial joint points.

Regarding the optimization analysis condition regarding the number of joint candidate points, for example, when the density method is applied in the topology optimization in the optimization analysis by the optimization analysis unit 23, which will be described later, the joint candidate points are modeled. A volume of a joint candidate point calculated based on the density of elements (beam elements, three-dimensional elements, etc.) may be given as a constraint condition.

(optimization analysis part)
The optimization analysis unit 23 applies the variable load conditions set by the variable load condition setting unit 17 to the optimization analysis model, performs optimization analysis under the optimization analysis conditions, and reduces the cumulative damage degree of the joint candidate points. The arrangement of joint candidate points that is achieved for the purpose of either improving the rigidity of the optimized analysis model or minimizing the number of remaining joint candidate points is obtained as the optimal arrangement of the joint points.

Topology optimization can be applied as the optimization analysis by the optimization analysis unit 23 .
When using the density method in topology optimization, a normalized virtual density that takes a value from 0 to 1 is used as a design variable for elements modeled as joint candidate points (beam elements, solid elements, etc.) and calculate the density value that satisfies the optimization analysis conditions.

If the calculated density value is 1, the joint candidate point exists completely, if it is 0, the joint candidate point does not exist, and if it is the intermediate value, the joint candidate point The joining of the parts assembly by is in an intermediate state.

Therefore, when there are many intermediate densities to which the density method is applied in topology optimization, it is preferable to perform discretization using a penalty coefficient as shown in Equation (2).

A penalty coefficient of 2 or more is often used for discretization, but a penalty coefficient of 4 or more is preferable in the optimization analysis of junction positions according to the present invention. Furthermore, the penalty coefficient is more preferably 4 or more for plane elements and three-dimensional elements, and 20 or more for beam elements.

Note that the optimization analysis unit 23 may perform optimization analysis by topology optimization as described above, or may perform optimization analysis by another calculation method.

FIG. 10 shows an example of the optimum arrangement of the junction points 157 obtained by the optimization analysis unit 23 applying the density method in the topology optimization and performing the optimization analysis. Note that the effect of the optimum placement of the junction points obtained in the first embodiment will be described in Example 1, which will be described later.

<Method for optimization analysis of joint position of car body>
The optimization analysis method for the joint position of the vehicle body according to Embodiment 1 of the present invention (hereinafter simply referred to as the "optimization analysis method") is to analyze a plurality of part models composed of beam elements, planar elements and/or three-dimensional elements. A computer executes the following steps for all or part of an automobile body model having an initial joint point for joining a plurality of part models as a set of parts, improving the rigidity of the body model, An optimization analysis is performed to find the optimum arrangement of joints for the purpose of either improving the fatigue life of joints that join parts assembly or minimizing the number of joints, as shown in FIG. , an analysis target model setting step S1, an optimization analysis model generation step S3, a fluctuating load condition setting step S5, a target fatigue life setting step S7, an optimization analysis condition setting step S9, and an optimization analysis step S11. , is included.
Each of these steps will be described below. The following steps are assumed to be performed by the optimization analysis device 1 (FIG. 1) configured by a computer.

<<Analysis target model setting step>>
The analysis target model setting step S1 sets all or part of the vehicle body model as the analysis target model.

In the first embodiment, in the analysis target model setting step S1, the analysis target model setting unit 13 sets the floor model 111, which is a part of the vehicle body model, as the analysis target model.

<<Optimization analysis model generation step>>
In the optimization analysis model generation step S3, an optimization analysis model is generated by densely setting all joint candidate points that are candidates for joint points of optimal arrangement for the model to be analyzed.

In the first embodiment, in the optimization analysis model generation step S3, the optimization analysis model generation unit 15 creates an additional connection point 153 between the initial connection points 131 preset in the floor part model 111. The initial junction is densely generated at a predetermined interval p (p < P, P: interval between initial junction points) that can increase the actual additional junction points 153 such that current shunting does not occur at the time of junction. Both the point 131 and the additional joining point 153 are set as joining candidate points 155 .

<<Fluctuation load condition setting step>>
In the variable load condition setting step S5, the variable load applied to the optimized analysis model is divided into load conditions of a plurality of different vibration patterns, and the load conditions of each vibration pattern are combined for a predetermined number of cycles to form one sequence. is set.

In the first embodiment, in the fluctuating load condition setting step S5, the fluctuating load condition setting unit 17 of the optimization analysis device 1 sets the load condition of the first vibration pattern shown in FIG. The load condition of the second vibration pattern is combined with 20 cycles to set a fluctuating load condition as one sequence (see FIG. 6), and further, as shown in FIGS. set.

<<Target fatigue life setting step>>
The target fatigue life setting step S7 sets the target fatigue life of the optimization analysis model by the number of sequences of the variable load condition set in the variable load condition setting step S5.
As the target fatigue life of the optimized analysis model, stress analysis is performed separately by giving the load condition of the vibration pattern under the variable load condition set in the variable load condition setting step S5 to the model to be analyzed, and the result of the stress analysis is used. , Calculate the number of sequences of variable load conditions that will be the fatigue life of the initial joint point of the model to be analyzed, and the target fatigue life based on the number of sequences of variable load conditions that will be the fatigue life of the initial joint point Alternatively, the target fatigue life may be set to the number of sequences under the variable load condition based on a conventional empirical rule.

Here, the target fatigue life is the fatigue life that should be satisfied by the joint candidate points to be optimized, and is at least the shortest fatigue life (shortest fatigue life) of each initial joint point calculated in the target fatigue life setting step S7. The number of sequences of variable load conditions that is longer than the number of sequences of variable load conditions is set as the target fatigue life.

<<Optimization analysis condition setting step>>
In the optimization analysis condition setting step S9, in order to perform an optimization analysis with the optimization analysis model as the target of optimization, each load condition for each of a plurality of different vibration patterns obtained by dividing the fluctuation load in the fluctuation load condition setting step S5 is performed. , the ratio of the number of cycles of the load condition of each vibration pattern to the number of repetitions of fracture is summed up for the number of sequences of the variable load conditions set in the target fatigue life setting step S7. The condition regarding the cumulative damage degree of the joint candidate point obtained as the cumulative damage degree DM of each joint candidate point and left by the optimization analysis, the condition concerning the rigidity of the optimization analysis model, and the joint candidate point left by the optimization analysis A condition regarding the score is set as an objective function or a constraint condition, which is an optimization analysis condition.

In the first embodiment, in the optimization analysis condition setting step S9, the optimization analysis condition setting unit 21 sets the stiffness maximization of the optimization analysis model (minimization of the displacement of the stiffness evaluation point P) as the objective function, A constraint that the fatigue life of the candidate point 155 is longer than the target fatigue life and a constraint that the number of remaining joint candidate points is the same as the number of initial joint points are set as optimization analysis conditions.

As a condition regarding stiffness, for example, a predetermined position in the model to be analyzed may be set as a stiffness evaluation point, and displacement or strain at the stiffness evaluation point may be used as an index. Then, in the variable load condition, for example, the variable load is divided into each vibration pattern, and the sum of the displacements of the stiffness evaluation point P under the load condition of each vibration pattern is minimized, or the stiffness evaluation point under the variable load condition is minimized. Minimization of the displacement of P may be the condition for stiffness.

In addition, the condition regarding the fatigue life is not limited to the target fatigue life set in the target fatigue life setting step S7 as it is as a constraint condition. A constraint condition may be given that the damage is less than or equal to the degree of damage.

<<Optimization Analysis Step>>
The optimization analysis step S11 applies the variable load conditions set in the variable load condition setting step S5 to the optimization analysis model, performs optimization analysis under the optimization analysis conditions, reduces the cumulative damage degree of the joint candidate points, and optimizes The arrangement of joint candidate points that is achieved for the purpose of either improving the rigidity of the analytical model or minimizing the number of remaining joint candidate points is obtained as the optimal arrangement of the joint points.

In the first embodiment, in the optimization analysis step S11, the optimization analysis unit 23 performs optimization analysis with the joint candidate points set in the floor part model 111 as the optimization target, and as shown in FIG. The arrangement of joint candidate points 155 that satisfy the optimization analysis condition is obtained as the optimum arrangement of joint points 157 .

<Optimization analysis program for joint position of car body>
Embodiment 1 of the present invention can be configured as a vehicle body joint position optimization analysis program that causes each part of the vehicle body joint position optimization analysis apparatus 1 configured by a computer to function.
That is, the vehicle body joint position optimization analysis program according to Embodiment 1 of the present invention uses all or part of a vehicle body model as an analysis target model, improves the rigidity of the vehicle body model for the analysis target model, Optimization analysis is performed to find the optimum arrangement of joints for the purpose of either improving the fatigue life of the joints that join the set or minimizing the number of joints. As shown as an example, an analysis target model setting unit 13, an optimization analysis model generation unit 15, a fluctuating load condition setting unit 17, a target fatigue life setting unit 19, an optimization analysis condition setting unit 21, an optimization It has a function to be executed by the analysis unit 23 .

As described above, according to the optimization analysis method, device, and program for the joint position of the vehicle body according to the first embodiment, the whole or part of the vehicle body model of the automobile is used as the analysis target model, and the parts assembly is performed for the analysis target model. The optimization analysis conditions (objective function or constraint By setting the conditions) and performing optimization analysis on the candidate joint points, when a variable load whose amplitude, direction, etc. fluctuates over time is input to the vehicle body, the number of candidate joint points can be minimized, and the analysis target model It is possible to find the optimum arrangement of the joints for the purpose of either improving the rigidity of the parts or improving the fatigue life of the joints that join the parts assembly.

[Embodiment 2]
In the first embodiment of the present invention described above, the topology optimization based on the density method is applied in the optimization analysis, and the junction candidate points satisfying the optimization analysis conditions are obtained. Whether a junction candidate point remains or disappears in topology optimization is determined based on the value of the density of the junction candidate point.

As mentioned above, the density in topology optimization based on the density method is a normalized virtual density that takes values from 0 to 1. If the density value is 1, the junction candidate points are completely If it is a remaining state, 0 indicates that the joint candidate point has disappeared, and if it is an intermediate value between 0 and 1, it indicates an intermediate state between the survival and disappearance of the joint candidate point.

Therefore, as described above, when there are many intermediate densities to which the density method is applied in topology optimization, it is preferable to perform discretization using a penalty coefficient as shown in Equation (1).

Then, when discretization is performed by giving a penalty coefficient in topology optimization, the fatigue life and All the stiffnesses of the model to be analyzed satisfy the target performance of fatigue life and stiffness.

However, if a penalty coefficient is given in the topology optimization and discretization is not performed, intermediate density junction candidate points remain in the optimization analysis model after the optimization analysis. Then, in order to obtain the optimum arrangement of a predetermined number of junction points based on the result of the optimization analysis, for example, the arrangement of candidate junction points with a density equal to or higher than a certain threshold is selected as the optimum arrangement of junction points, and the intermediate The placement of joint candidate points with reasonable density values is not selected as the optimal placement of joint points.

When the optimal arrangement of joint points obtained in this way is newly set in the model to be analyzed and the fatigue life of the model to be analyzed is calculated, stress concentrates on a specific joint point, resulting in a decrease in fatigue life below the target fatigue life, and the analysis The stiffness of the target model may be degraded and problems may occur such that the fatigue life and/or stiffness do not meet the specified performance.

Therefore, as a result of intensive studies to solve the above problem, it is determined whether the fatigue life and rigidity of the model to be analyzed in which the arrangement of the selected joint candidate points is set instead of the initial joint points satisfies the predetermined performance, If it is determined that the conditions are not met, the optimization analysis conditions (e.g., density threshold) are changed and the optimization analysis is performed again to find the optimal arrangement of joints that satisfies the specified performance in terms of stiffness and fatigue life. was obtained.

The method, apparatus, and program for optimizing the joining position of the vehicle body according to the second embodiment are based on the above findings, and the specific configuration thereof will be described. It should be noted that redundant descriptions of the same components as those of the vehicle body joint position optimization analysis method, apparatus, and program according to the second embodiment will be omitted.

<Optimization analysis device for joint position of car body>
The configuration of a vehicle body joining position optimization analysis apparatus according to Embodiment 2 of the present invention will be described below.

The optimization analysis device 31 uses all or part of a vehicle body model as a model to be analyzed, and has a plurality of part models composed of beam elements, planar elements and/or three-dimensional elements. For all or part of a car body model that has initial joints that are joined as a body model, either increase the rigidity of the car body model, improve the fatigue life of the joints that join the assembly of parts in the car body model, or minimize the number of joints. It is a device for performing optimization analysis for obtaining the optimum arrangement of junction points for the purpose of achieving the above, and is composed of a PC (personal computer) or the like, and as shown in FIG. 7, a working data memory 9 and an arithmetic processing unit 33 . The display device 3, the input device 5, the storage device 7, and the work data memory 9 are connected to the arithmetic processing section 33, and their respective functions are executed by commands from the arithmetic processing section 33. FIG.

≪Arithmetic processing section≫
As shown in FIG. 12, the arithmetic processing unit 33 includes an analysis target model setting unit 13, an optimization analysis model generation unit 15, a fluctuating load condition setting unit 17, a target fatigue life setting unit 19, and an optimization analysis condition It includes a setting unit 21 and an optimization analysis unit 34, and further includes a selected junction candidate setting analysis target model generation unit 35, a selected junction candidate point performance calculation unit 37, a judgment unit 39, and an optimum junction determination unit 41. , and is composed of a CPU (central processing unit) such as a PC. Each of these units functions when the CPU executes a predetermined program.

The analysis target model setting unit 13, the optimization analysis model generation unit 15, the fluctuating load condition setting unit 17, the target fatigue life setting unit 19, and the optimization analysis condition setting unit 21 in the arithmetic processing unit 33 are described above. Since the functions are the same as those of the first embodiment, the optimization analysis unit 34, the selected joint candidate point setting analysis target model generation unit 35, the selected joint candidate point performance calculation unit 37, the determination unit 39, and the optimum The function of the connection point determination unit 41 will be described.

(optimization analysis part)
The optimization analysis unit 34 applies the variable load conditions set by the variable load condition setting unit 17 to the optimization analysis model, performs optimization analysis under the optimization analysis conditions, and reduces the cumulative damage degree of the joint candidate points. The placement of the joint candidate points that is achieved for the purpose of either improving the rigidity of the optimization analysis model or minimizing the number of the remaining joint candidate points is retained as a provisional optimal arrangement of the joint points. .

As the optimization analysis by the optimization analysis unit 34, topology optimization can be applied as in the optimization analysis unit 23 of the first embodiment described above.

(Selected junction candidate point setting analysis target model generation unit)
The selected joint candidate point setting analysis target model generation unit 35 selects a predetermined number of joint candidate points from the joint candidate points remaining as the provisional optimal arrangement by the optimization analysis in the optimization analysis unit 34, and selects the joint candidate points. The point is set in the analysis target model instead of the initial connection point, and the selected connection candidate point setting analysis target model is generated.

In topology optimization based on the density method, the density of elements (for example, beam elements) modeled as joint candidate points is calculated. A predetermined number of points may be selected from joint candidate points having element densities equal to or greater than a predetermined threshold value and set as the model to be analyzed.

(Selected junction candidate point performance calculation unit)
The selected joint candidate point performance calculation unit 37 applies the load conditions and constraint conditions of each vibration pattern under the variable load conditions set by the variable load condition setting unit 17 to the selected joint candidate point setting analysis target model, and performs stress analysis. Using the results of the stress analysis, the fatigue life of the selected joint candidate points under fluctuating load conditions and the stiffness of the selected joint candidate point setting analysis target model are calculated.

The fatigue life under variable load conditions of the candidate joint points set in the selected joint candidate point setting analysis target model is obtained by the stress analysis of the selected joint candidate point setting analysis target model in the same manner as the target fatigue life setting unit 19 described above. The cumulative damage degree DM (see formula (2)) can be calculated based on the accumulated fatigue damage law using the obtained stress at the joint candidate point, and can be obtained using commercially available fatigue life prediction analysis software.

The stress at the joint candidate point used to calculate the cumulative damage degree DM includes, for example, the stress of the planar element of the part model to which the beam element modeled as the joint candidate point is connected, and the force acting on both ends of the beam element. Nominal structural stresses calculated from moments, etc. can be used.

In addition, the stiffness of the selected joint candidate point setting analysis target model can be used, for example, by using a predetermined position as a stiffness evaluation point and using its displacement or strain as an index. By dividing into each vibration pattern, a value obtained by adding up the displacements of the stiffness evaluation points under the load conditions of each vibration pattern may be used as an index.

(Judgment part)
The determination unit 39 determines whether the fatigue life under the variable load condition of the joint candidate point in the selected joint candidate point setting analysis target model and the rigidity of the selected joint candidate point setting analysis target model exceed the analysis target model in which the initial joint point is set. It determines whether or not the specified performance is satisfied.

The predetermined performance related to fatigue life may be within a predetermined range of the target fatigue life set by the target fatigue life setting unit 19, for example.

(Optimal junction point determination part)
When the determination unit 39 determines that the predetermined performance is satisfied, the optimum junction determination unit 41 arranges the candidate junction points selected by the selected junction candidate point setting analysis target model generation unit 35 according to the optimum junction point. If it is determined as an arrangement and the determining unit 39 determines that the predetermined performance is not satisfied, accumulation of joining candidate points to be left by the optimization analysis set by the optimization analysis condition setting unit 21 until the predetermined performance is satisfied. By changing the condition regarding the degree of damage, the condition regarding the rigidity of the optimization analysis model, or the condition regarding the number of joint candidate points left by the optimization analysis, the optimization analysis unit 34 and the selected joint candidate point setting analysis target model generation unit 35, the selected joint candidate point performance calculation unit 37, and the determination unit 39 are repeated, and the arrangement of the joint candidate points selected when predetermined performance is satisfied is determined as the optimum arrangement of the joint points. .

If the determination unit 39 does not determine that the rigidity and fatigue life satisfy the predetermined performance, the optimum joint point determination unit 41 sets the optimization analysis conditions so as to increase the number of joint candidate points to be left in the optimization analysis. For example, the unit 21 may change optimization analysis conditions such as thresholds for selecting joining candidate points.

In the optimization analysis condition setting unit 21, when changing the condition related to the cumulative damage degree of the joint candidate points, the condition related to the stiffness of the optimization analysis model, or the condition related to the number of remaining joint candidate points, one of One condition may be changed, or two or three conditions may be changed at the same time.

<Method for optimization analysis of joint position of car body>
A method for optimizing and analyzing a joint position of a vehicle body according to a second embodiment of the present invention comprises a plurality of part models each composed of a beam element, a plane element and/or a three-dimensional element. For all or part of an automobile body model that has initial joints that are joined as a body model, the computer performs the following steps to improve the rigidity of the car body model and improve the fatigue life of the joints that join the assembly of parts in the car body model. , minimization of the number of joint points, and optimization analysis is performed to find the optimum arrangement of the joint points. As shown in FIG. Analysis model generation step S3, fluctuating load condition setting step S5, target fatigue life setting step S7, optimization analysis condition setting step S9, optimization analysis step S12, selected joint candidate point setting analysis target model generation step S13 , a selected joint candidate performance calculation step S15, a determination step S17, and an optimum joint point determination step S19.

Of the above steps, the analysis target model setting step S1, the optimization analysis model generation step S3, the fluctuating load condition setting step S5, the target fatigue life setting step S7, and the optimization analysis condition setting step S9 is the same as in the first embodiment described above, the optimization analysis step S12, the selected junction candidate setting analysis target model generation step S13, the selected junction candidate point performance calculation step S15, and the judgment step S17 and the optimum junction point determination step S19 will be described. Each step of the optimization analysis method according to the second embodiment is performed by the optimization analysis device 31 (FIG. 12) configured by a computer.

<<Optimization Analysis Step>>
The optimization analysis step S12 applies the variable load conditions set in the variable load condition setting step S5 to the optimization analysis model, performs optimization analysis under the optimization analysis conditions, reduces the cumulative damage degree of the joint candidate points, and optimizes the The joint candidate point arrangement is retained as a provisional optimal joint point arrangement for the purpose of either improving the rigidity of the analytical model or minimizing the number of remaining joint candidate points.

In the second embodiment, in the optimization analysis step S12, the optimization analysis unit 34 performs optimization analysis with the joint candidate points set in the floor part model 111 as the optimization target, and as shown in FIG. The layout of the joint candidate points 155 that satisfy the optimization analysis condition is left as the temporary optimal layout of the joint points 157 .

<<Selected joint candidate point setting analysis target model generation step>>
The selected joint candidate point setting analysis object model generation step S13 selects a predetermined number of joint candidate points from among the joint candidate points remaining as the provisional optimum arrangement by the optimization analysis in the optimization analysis step S12, and selects the joint candidate points. The point is set in the analysis target model instead of the initial connection point, and the selected connection candidate point setting analysis target model is generated.
In the second embodiment, the selected joining candidate point setting analysis target model generation step S13 is performed by the selected joining candidate point setting analysis target model generation unit 35 .

<<Selected joint candidate point performance calculation step>>
In the selected joint candidate point performance calculation step S15, stress analysis is performed by applying the load conditions and constraint conditions of each vibration pattern under the variable load conditions set in the variable load condition setting step S5 to the selected joint candidate point setting analysis target model. Using the results of the analysis, the fatigue life of the selected joint candidate points under fluctuating load conditions and the stiffness of the selected joint candidate point setting analysis target model are calculated.
In the second embodiment, the selected joint candidate point performance calculation step S15 is performed by the selected joint candidate point performance calculator 37 .

≪Judgment step≫
In the determination step S17, the fatigue life under the variable load condition of the joint candidate point in the selected candidate joint point setting analysis target model and the rigidity of the selected joint candidate point setting analysis target model exceed the analysis target model in which the initial joint point is set. It determines whether or not the specified performance is satisfied.
In the second embodiment, determination step S17 is performed by the determination unit 39 .

As described above, the predetermined performance related to fatigue life may be within a predetermined range of the target fatigue life set by the target fatigue life setting unit 19, for example.

≪Optimal junction point determination step≫
If it is determined in the determination step S17 that the predetermined performance is satisfied, the optimal junction point determination step S19 determines the placement of the junction candidate points selected in the selected junction candidate point setting analysis target model generation step S13 as the optimal junction point. If it is determined as an arrangement and it is determined that the predetermined performance is not satisfied in the determination step S17, the cumulative damage of the joint candidate points left by the optimization analysis set in the optimization analysis condition setting step S9 is performed until the predetermined performance is satisfied. The condition regarding the stiffness, the condition regarding the stiffness of the optimization analysis model, or the condition regarding the number of joint candidate points left by the optimization analysis are changed, and the optimization analysis step S12 and the selected joint candidate point setting analysis target model generation step S13 are performed. , the selected joint candidate point performance calculation step S15, and the determination step S17 are repeated, and the arrangement of the joint candidate points selected when the predetermined performance is satisfied is determined as the optimum arrangement of the joint points.
The reason why the predetermined performance may not be satisfied in the determination step S17 is that there are many joining candidate points with intermediate densities, and the combined performance is determined.
In Embodiment 2, the optimal junction determination step S19 is performed by the optimal junction determination unit 41 .

In the optimization analysis condition setting step S9, when changing the condition related to the cumulative damage degree of the joint candidate points, the condition related to the stiffness of the optimized analysis model, or the condition related to the number of remaining joint candidate points, one of One condition may be changed, or two or three conditions may be changed simultaneously.

<Optimization analysis program for joint position of car body>
Embodiment 2 of the present invention can be configured as a vehicle body joint position optimization analysis program that causes each part of a vehicle body joint position optimization analysis apparatus 31 configured by a computer to function.
That is, the vehicle body joint position optimization analysis program according to the second embodiment of the present invention uses all or part of a vehicle body model as an analysis target model, and a plurality of parts composed of beam elements, planar elements and/or three-dimensional elements. For all or part of an automobile body model having a model and having an initial joint point for joining a plurality of part models as a part assembly, the rigidity of the body model is improved, and the joint point for joining the part assembly in the body model. The optimization analysis is performed to find the optimum arrangement of joint points for the purpose of either improving the fatigue life of the joint or minimizing the number of joint points. As shown in FIG. Includes an analysis target model setting unit 13, an optimization analysis model generation unit 15, a fluctuating load condition setting unit 17, a target fatigue life setting unit 19, an optimization analysis condition setting unit 21, and an optimization analysis unit 34 Further, it has a function to be executed by a selected joint candidate point setting analysis target model generation unit 35, a selected joint candidate point performance calculation unit 37, a determination unit 39, and an optimum joint point determination unit 41.

As described above, in the optimization analysis method, apparatus, and program for the joint position of the vehicle body according to the second embodiment, even if discretization is not performed in the topology optimization based on the density method, The purpose is to minimize the number of joint candidate points, improve the rigidity of the model to be analyzed, or improve the fatigue life of the joints where parts are joined. can appropriately determine the optimum placement of junction points to be achieved as

In the above description, a vehicle body model obtained by modeling the entire vehicle body is acquired, and the floor section model, which is a part of the vehicle body model, is used as the model to be analyzed. However, in the present invention, the entire vehicle body model may be used as the analysis target model, or a portion of the vehicle body model other than the floor model may be used as the analysis target model. Alternatively, a vehicle body partial model, which is a part of the vehicle body model, may be acquired, and the acquired vehicle body partial model may be used as the model to be analyzed.

In the above description, the case where 352 initial joint points 131 are set in advance at intervals of 60 mm in the floor section model 111 is taken as an example, but the interval and number of the initial joint points 131 are limited to this. not something.

Further, the initial junction points 131 were for the cases where they were preset in the floor section model 111 by an operator or other means. However, in the present invention, the analysis target model setting unit or in the analysis target model setting step, the operator newly sets the initial connection point, or the analysis target model for which the initial connection point has already been set. Additional initial junction points may be set.

In the first embodiment, it is assumed that a constant load (moment) that twists around the FR (front to rear) axis and the RL axis acts on the floor model 111. Although the load conditions and constraint conditions shown in FIGS. 2 and 4 were set, the present invention assumes a variable load acting on the part of the vehicle body to be analyzed and the actual vehicle body, and sets the variable load condition and constraint condition. Constraint conditions may be appropriately set.

Further, in the examples of the first and second embodiments, the target performance of the fatigue life of the joint candidate point is based on the shortest fatigue life (shortest fatigue life) of the initial joint point set in the analysis target model. was to be set.

However, the present invention calculates the fatigue life of the joint candidate points 155 in the optimization analysis model in which the additional joint points 153 are densely set to the initial joint points 131 before performing the optimization analysis (FIG. 5), and the calculated It is preferable to determine the shortest fatigue life among the fatigue lives of the joint candidate points and set the target fatigue life in the optimization analysis so as to satisfy the following relationship.
(shortest fatigue life of initial joint point)≦(target fatigue life of joint candidate point)≦(shortest fatigue life of joint candidate point where joint points are densely set before optimization analysis).

Furthermore, in the above description, the optimization analysis was performed with both the initial junction point and the additional junction point as candidate junction points. It is also possible to seek the optimum arrangement of junction points to be added to the initial junction point without being targeted.

Also, in the explanation of the above example, the optimization analysis conditions were set such that the score of the joint candidate point is the same as the score of the initial joint point. Optimization analysis conditions may be set.

Furthermore, if the initial joint point is set as a joint candidate point and optimization analysis is performed, the joint candidate point to be joined as a part assembly disappears in the optimization analysis, and the parts assembly becomes disjointed, making optimization analysis impossible. Sometimes it becomes impossible. In such cases, each set of parts should have at least one fixed junction that is not included in the optimization analysis.

Here, the fixed joint point may be arbitrarily selected from, for example, initial joint points, or fixed joint candidate points are set as candidates for the fixed joint point, and stress analysis or optimization analysis of the model to be analyzed is performed. separately, and based on the result, a fixed joint point may be selected from the fixed joint candidate points.

In the above description, the objective function is the fatigue life of the joint candidate point or the stiffness of the optimized analysis model. However, the number of joint candidate points may be the objective function, and the fatigue life and stiffness may be the constraint conditions. .

An analysis was conducted to confirm the effect of the present invention, which will now be described.
In the analysis, as shown in FIG. 14, a floor part model 111 that models the floor part of the vehicle body is targeted, and the optimum arrangement of joint points where the part models that make up the floor part model 111 are joined as a part assembly is analyzed for optimization. obtained by

As described in the first embodiment, the floor model 111 includes, as component models, a floor panel model 113, a tunnel model 115, a locker inner model 117, a locker outer model 119, a front floor cross model 121, and a rear floor cross model 123 . Each of these part models is modeled with planar elements.

Further, the floor part model 111 is preset with an initial joining point 131 for joining part models as a part assembly. The initial joint points 131 were modeled by beam elements connecting nodes of plane elements of the part model, the number of initial joint points was 352, and the interval P between the initial joint points 131 was 60 mm.

In Example 1, first, the target fatigue life was set based on the fatigue life of the initial joint 131 under fluctuating load conditions shown in FIG.

The fluctuating load conditions shown in Fig. 6 are the load conditions of the first vibration pattern (Fig. 2) with a moment of 0.7 kN m around the FR axis swinging in both directions for one cycle, and then the load conditions of the second vibration pattern (Fig. 2). As shown in Fig. 4), one sequence is a combination of 20 cycles with a moment of 1.4 kN·m swinging around the RL axis on both sides.

Next, stress analysis of the floor part model 111 is performed for each of the load conditions of the first vibration pattern (FIG. 2) and the load conditions of the second vibration pattern (FIG. 4). The stress generated at 131 was obtained.

Subsequently, the number N ₁ of repetitions until the initial joint 131 breaks when the different stress amplitudes σ ₁ and σ ₂ generated at the initial joint 131 under varying load conditions are independently generated at the initial joint 131 . and N ₂ were obtained from the SN diagram (Fig. 7).

Then, the number of repetitions N ₁ and N ₂ until fracture at each stress amplitude, and the number of cycles n ₁ (= 1 cycle) and n ₂ (=20 cycles) were substituted into the formula (1) to obtain the cumulative degree of damage dm in one sequence.

Furthermore, the number of sequences K when the cumulative damage degree DM calculated using the formula (2) is 1 or more is calculated as the fatigue life of the initial joint 131 under fluctuating load conditions, and the fatigue life of each initial joint is calculated. The target fatigue life was set based on the shortest fatigue life among the lives.

After setting the target fatigue life, an optimization analysis of the optimal layout of the joints in the floor part model 111 was performed.
In the optimization analysis, first, as shown in FIG. 5, an additional joint point 153 is set between the initial joint points 131 in the floor part model 111 at an interval of p=20 mm, and the initial joint point 131 and the additional joint point 153 are set. was densely set as the joint candidate points 155 to generate an optimization analysis model 151 .

Next, the load conditions and constraint conditions shown in FIG. 2 and FIG. 4 were given, and optimization analysis was performed to find the joint candidate points 155 that satisfy the optimization analysis conditions. For the optimization analysis, topology optimization based on the density method was applied, and discretization was performed with a penalty factor of 20 in the topology optimization.

In the first embodiment, the objective function related to the stiffness of the optimization analysis model 151, the constraints related to the cumulative damage degree DM (fatigue life) of the joint candidate points 155 left by the optimization analysis, and the joint candidate points left by the optimization analysis An example of the invention is one in which 155 points of constraints are set as optimization analysis conditions.

The objective function for stiffness is the displacement of the stiffness evaluation point P (see FIG. 14(b)) under the load conditions of the first vibration pattern and the load condition of the second vibration pattern. The displacement is set to be equal to or less than the stiffness evaluation point P when stress analysis is performed on the floor part model 111 .

As for the constraint condition regarding the fatigue life, the cumulative damage degree DM of the joint candidate point 155 under fluctuating load conditions was calculated in the same manner as the initial joint point 131 described above. It is assumed that the fatigue life calculated from the cumulative damage degree DM of each joint candidate point 155 is longer than the target fatigue life.

Furthermore, the constraint condition regarding the points of the joint candidate points 155 is the condition that the points of the joint candidate points left by the optimization analysis are the points of the initial joint points 131 .

In addition, in Example 1, as a comparison target, an optimization analysis in which the stiffness of the optimization analysis model is the objective function and only the number of joint candidate points is the constraint condition without giving a constraint condition regarding the cumulative damage degree DM (fatigue life). Comparative examples were provided with certain conditions. Here, the condition regarding the rigidity and the condition regarding the number of joint candidate points in the comparative example were the same as those in the invention example.

FIG. 10 shows the results of the remaining joining candidate points 155 in the inventive example, and FIG. 15 shows the results of the remaining joining candidate points 155 in the comparative example.
Comparing FIG. 10 and FIG. 15, it can be seen that there is a difference in the arrangement of the joining candidate points 155 between the inventive example and the comparative example, mainly in the region surrounded by the solid ellipse.

Furthermore, regarding the optimal joint point floor model 161 in which the arrangement of the joint candidate points 155 remaining by the optimization analysis is set as the optimum arrangement of the joint points 157, and the optimally arranged joint points 157 are set as shown in FIGS. 10 and 15, The stiffness and fatigue life of the junction 157 were calculated.

In calculating the stiffness and fatigue life, first, the load conditions of the first vibration pattern shown in FIG. 2 and the load conditions and constraint conditions of the second vibration pattern shown in FIG. stress analysis was performed.

Regarding the stiffness of the optimum junction floor part model 161, the stiffness evaluation points P (see FIG. 14(b)) obtained by stress analysis under the load conditions of the first vibration pattern and the load conditions of the second vibration pattern. was used as an index.

Regarding the fatigue life of the joint 157, the shortest fatigue life among the fatigue lives calculated using the stress of the joint 157 obtained by the stress analysis of the optimum joint floor portion model 161 was used as an index. In addition, in calculating the fatigue life of the joint 157, the nugget diameter of the joint 157 was set to 5 mm, and the plane element of the part model to which the beam element modeled as the joint 157 was connected was recut into a spider web shape (Fig. 9). reference).

Furthermore, the floor part model 111 (FIG. 14) in which the initial joint point 131 is set and the optimization analysis model 151 in which the initial joint point 131 and the additional joint point 153 before the optimization analysis are densely set. Rigidity and shortest fatigue life were determined and used as a standard example and a reference example, respectively.

FIG. 16 shows the results of the rigidity improvement rate of the invention examples, the reference examples and the comparative examples, and FIG. 17 shows the results of the shortest fatigue life ratios of the invention examples, the reference examples and the comparative examples. The rigidity improvement rate in the invention example and the comparative example was obtained based on the displacement of the rigidity evaluation point P in the floor section model 111 of the reference example, and the shortest fatigue life ratio was obtained in the floor section model 111 of the reference example. A ratio to the shortest fatigue life of the initial joint 131 was used. In FIG. 16, the black bar graph indicates the rigidity improvement rate under the load condition of the first vibration pattern, and the gray bar graph indicates the rigidity improvement rate under the load condition of the second vibration pattern.

Both the invention examples and the comparative examples had a positive value for the rigidity improvement rate, and the rigidity was improved more than the reference example, and the shortest fatigue life was also improved.
As shown in FIG. 16, the rigidity improvement rate was 1.8% in the invention example, which was slightly lower than 2.0% in the comparative example, but resulted in an improvement in rigidity compared to the reference example.
Furthermore, regarding the shortest fatigue life, as shown in FIG. 17, the shortest fatigue life ratio in the invention example is 2.4, which is larger than the shortest fatigue life ratio (= 1.1) in the comparative example. The result was close to the shortest fatigue life ratio (=3.6).

In the above-described first embodiment, a portion of the vehicle body (floor portion) is targeted and the joint point optimization analysis is performed with the stiffness as the objective function. Shown is a vehicle body model 201 of the entire automobile body (full vehicle), and the condition regarding the cumulative damage degree (fatigue life) of the joint candidate points left by the optimization analysis, the condition regarding the rigidity of the optimization analysis model, and the optimum Conditions relating to the number of joint candidate points to be left in the optimization analysis were set as objective functions or constraint conditions, which are optimization analysis conditions, and optimization analysis of the joint points in the vehicle body model was performed.

The vehicle body model 201 includes a plurality of part models obtained by modeling body frame parts and vehicle body panel parts with plane elements, and initial joint points for joining the part models as a set of parts are set in advance. The number of initial joint points is 4983 points, and it is modeled with beam elements that connect the nodes of the plane elements of the part model.

First, additional joint points are set between the initial joint points in the vehicle body model 201 at a minimum joint interval of 20 mm, and the initial joint points and the additional joint points are densely set as joint candidate points, and the optimization analysis model 211 (Fig. 18 (a)(i) and FIG. 18(b)(i)) were generated. Note that, in the vehicle body model 201, the welding intervals of the initial joint points differ for each set of parts of the part model, so the welding intervals of the additional joint points set in the vehicle body model 201 are not necessarily constant, but are as uniform as possible and have the minimum welding interval. Additional joint points were set so as not to be less than 20mm.

In Example 2, first, a fluctuating load condition was set by combining the load condition of the first vibration pattern shown in FIG. 18(a) and the load condition of the second vibration pattern shown in FIG. 18(b). .

As shown in FIG. 18(a), the load condition of the first vibration pattern is obtained by setting the left and right front suspension mounting positions in the optimization analysis model 211 as load input points (A in FIG. 18(a)(i)). A two-way torsional load of ±2000 N is input in the vertical direction (Z direction) of the vehicle body. B) is a complete constraint.

As shown in FIG. 18(b), the load condition of the second vibration pattern is such that the rear portions 207 of the left and right side sills 203 of the optimized analysis model 211 are the load input points (A in FIG. 18(b)(i)). ), a double-sided lateral bending load of ±1000 N in the vehicle body width direction (Y direction) is input, and the constraint condition is that the mounting positions of the left and right front suspensions of the body model 201 are the constraint points (in FIG. 18(b)(i) (B ₁ ) in ), and translational movement is restricted by using the mounting positions on the left and right of the rear subframe and the body as constraint points (B ₂ in FIG. 18(b)(i)).

Then, as for the fluctuating load conditions, input the load condition of the first vibration pattern for 1 cycle (Fig. 18(a)), followed by the load condition of the second vibration pattern for 30 cycles (Fig. 18(b)). The combination to do was made into 1 sequence.

Next, the stress analysis of the vehicle body model 201 is performed for each of the load conditions and constraint conditions of the first vibration pattern (FIG. 18(a)) and the load conditions and constraint conditions of the second vibration pattern (FIG. 18(b)). , the stress generated at the initial joint point under the load conditions of each vibration pattern was obtained. In calculating the stress generated at the initial joint point, the part where the beam element 145 in the part model 143 is connected is set based on the nugget diameter of the actual spot weld point, such as the spot weld part 141 illustrated in FIG. Then, it was recut into a spider web-shaped planar element, and the stress value of the planar element in the peripheral portion 149 was used.

Subsequently, the number of repetitions N ₁ and N ₂ until the initial joint fractures when different stress amplitudes σ ₁ and σ ₂ generated at the initial joint under fluctuating load conditions are independently generated at the initial joint. was obtained from the SN diagram (Fig. 7).

Then, the number of repetitions N ₁ and N ₂ until fracture at each stress amplitude, the number of cycles n ₁ (= 1 cycle) of the load condition of the first vibration pattern in one sequence of fluctuating load conditions, and the second vibration pattern and the number of cycles n ₂ (=30 cycles) of the load condition were substituted into the equation (1) to obtain the cumulative damage degree dm in one sequence.

Furthermore, the number of sequences K when the cumulative damage degree DM calculated using formula (2) is 1 or more is calculated as the fatigue life of the initial joint point under fluctuating load conditions, and the fatigue life of each initial joint point The target fatigue life was set based on the shortest fatigue life.

18(a) and the second vibration pattern shown in FIG. 18(b) are combined for optimization analysis. The model 211 was applied to the model 211 and optimized analysis was performed to obtain joint candidate points that satisfy the optimization analysis conditions. For the optimization analysis, topology optimization based on the density method was applied, and discretization was performed with a penalty factor of 20 in the topology optimization.

In Example 2, Invention Examples 21, 22, and 23 were obtained by combining the objective function and constraint conditions of the optimization analysis conditions as shown in Table 1.

Invention Example 21 has an objective function related to the fatigue life of the joint candidate points left by the optimization analysis, a constraint condition related to the stiffness of the optimization analysis model 211, a constraint condition related to the number of joint candidate points left by the optimization analysis, was set as the optimization analysis conditions.
The objective function for the fatigue life was a condition under which the fatigue life calculated from the cumulative damage degree DM of the joint candidate points exceeded the target fatigue life and reached the maximum.
In addition, the constraint on stiffness is that the average value of the displacement of the left and right load input points A in the stress analysis in which the load condition of the first vibration pattern and the load condition of the second vibration pattern are given to the optimization analysis model 211 is The condition was set to be equal to or less than the average value of the displacement at the left and right load input points A when stress analysis was performed by applying the same load conditions to the original vehicle body model 201 .
Furthermore, the constraint condition regarding the number of joint candidate points is the number of initial joint points of the original vehicle body model 201 (=4983 points).

Invention Example 22 includes an objective function related to the stiffness of the optimization analysis model 211, a constraint condition related to the fatigue life of the joint candidate points left by the optimization analysis, a constraint condition related to the number of joint candidate points left by the optimization analysis, was set as the optimization analysis conditions.
The objective function related to stiffness is the sum of the strain energy of the optimization analysis model 211 when stress analysis is performed by giving the load condition of the first vibration pattern and the load condition of the second vibration pattern to the optimization analysis model 211. It was set as the minimum condition.
In addition, as a constraint condition regarding the fatigue life, the fatigue life calculated from the cumulative damage degree DM of the joint candidate point exceeds the target fatigue life and is the maximum.
Furthermore, the constraint condition regarding the number of joint candidate points is the number of initial joint points of the original vehicle body model 201 (=4983 points).

Invention Example 23 includes an objective function related to the number of joint candidate points left by the optimization analysis, a constraint condition related to the fatigue life of the joint candidate points left by the optimization analysis, a constraint condition related to the stiffness of the optimization analysis model 211, was set as the optimization analysis conditions.
The condition for minimizing the number of joint candidate points was used as the objective function for the number of joint candidate points. The joint candidate points that do not affect the rigidity performance and fatigue life were not included in the optimization analysis.
In addition, as a constraint condition regarding the fatigue life, the fatigue life calculated from the cumulative damage degree DM of the joint candidate point exceeds the target fatigue life and is the maximum.
Furthermore, the constraint condition regarding stiffness is that the average value of the displacement of the left and right load input points A in the stress analysis in which the load condition of the first vibration pattern and the load condition of the second vibration pattern are given to the optimization analysis model 211 is The condition was set to be less than that of the original vehicle body model 201 .

Furthermore, the arrangement of the joint candidate points remaining by the optimization analysis is regarded as the optimum arrangement of the joint points, and as shown in FIG. was calculated.
In calculating the stiffness and fatigue life, the load conditions and constraint conditions of the first vibration pattern shown in FIG. 18(a) and the load conditions and constraint conditions of the second vibration pattern shown in FIG. 18(b) are used. A stress analysis was performed on the optimum joint point vehicle body model 221 .

Fig. 19 shows the shortest fatigue life ratio (Fig. 19(a)), the rigidity improvement rate (Fig. 19(b)), and the number of remaining joint candidate points (Fig. 19 ( The results of c)) are shown. Furthermore, Table 2 summarizes the results shown in FIG.

In FIG. 19 and Table 2, the shortest fatigue life ratio of the optimal joint point car body model 221 is a ratio to the shortest fatigue life of the initial joint point in the original car body model 201 .
The rigidity improvement rate of the optimum joint point vehicle body model 221 is obtained based on the displacement of the rigidity evaluation point (load input point A) in the original vehicle body model 201. In FIG. 19(b), the black bar graph indicates the rigidity improvement rate under the load condition (torsional load) of the first vibration pattern, and the gray bar graph indicates the result of the rigidity improvement rate under the load condition (lateral bending load) of the second vibration pattern.

Invention Example 21, Invention Example 22, and Invention Example 23 all improve the shortest fatigue life ratio of the optimal joint point car body model 221, and Invention Example 21, which uses fatigue life as the target condition, has the highest shortest fatigue life ratio of 4.1 times. result.

In addition, the rigidity improvement rate of the optimum joint point vehicle body model 221 is a positive value in each of invention examples 21, 22, and 23, and the rigidity is improved compared to the original vehicle body model 201 . In particular, in Invention Example 22 in which the target condition is rigidity, the load condition of the first vibration pattern (torsion load) is 6.3%, and the load condition of the second vibration pattern (horizontal bending load) is 8.3%. The rate of rigidity improvement was higher than that of Invention Examples 21 and 23.

Furthermore, the number of joint points of the optimal joint point car body model 221 is 4893 points, which is the same as the original car body model 201, in Invention Examples 21 and 22, but in Invention Example 23 in which the target condition is the number of joint candidate points, , 359 points (-7.3%) less than the original car body model.

1 optimization analysis device 3 display device 5 input device 7 storage device 9 work data memory 11 arithmetic processing unit 13 analysis target model setting unit 15 optimization analysis model generation unit 17 fluctuating load condition setting unit 19 target fatigue life setting unit 21 optimum optimization analysis condition setting unit 23 optimization analysis unit 31 optimization analysis device 33 arithmetic processing unit 34 optimization analysis unit 35 selected joint candidate point setting analysis target model generation unit 37 selected joint candidate point performance calculation unit 39 determination unit 41 optimum joint point Determining part 101 Vehicle body model file 111 Floor part model 113 Floor panel model 115 Tunnel model 117 Locker inner model 119 Locker outer model 121 Front floor cross model 123 Rear floor cross model 125 Front end surface 127 Rear end surface 131 Initial joint point 141 Spot welding part 143 Part model 145 Beam element 147 Central part 149 Peripheral part 151 Optimization analysis model 153 Additional joint point 155 Joint candidate point 157 Joint point 161 Optimum joint floor model 201 Body model 203 Side sill 211 Optimization analysis model 221 Optimal joint body model

Claims (9)

A computer for all or part of an automobile body model comprising a plurality of part models consisting of beam elements, planar elements and/or three-dimensional elements, and having initial joining points for joining the plurality of part models as a set of parts. performs each of the following steps to achieve any of the following purposes: improving the rigidity of the vehicle body model, improving the fatigue life of the joints that join the parts assembly in the vehicle body model, and minimizing the number of the joints. A joint position optimization analysis method for a vehicle body for performing an optimization analysis for determining the optimum arrangement of the joint points,
an analysis target model setting step of setting all or part of the vehicle body model as an analysis target model;
an optimization analysis model generation step of generating an optimization analysis model by densely setting all connection candidate points that are candidates for the connection points of the optimal arrangement for the model to be analyzed;
Variable load condition setting for dividing the variable load applied to the optimization analysis model into load conditions of a plurality of different vibration patterns, and setting the variable load conditions as one sequence by combining the load conditions of the respective vibration patterns for a predetermined number of cycles. a step;
A target fatigue life setting step of setting the target fatigue life of the optimization analysis model by the number of sequences of the variable load condition;
In order to perform an optimization analysis that targets the optimization analysis model for optimization, the number of repetitions of fracture at each joint candidate point is obtained for each load condition of each vibration pattern, and the load condition of each vibration pattern is The sum of the ratio of the number of cycles and the number of repetitions to failure for the number of sequences of the variable load conditions set by the target fatigue life setting step is obtained as the cumulative damage degree of each candidate joint point, and the residual is obtained by optimization analysis. A condition relating to the degree of cumulative damage of the joint candidate points to be allowed, a condition relating to the stiffness of the optimization analysis model, and a condition relating to the number of points of the joint candidate points to be left by the optimization analysis are defined as an objective function or an optimization analysis condition setting step to be set as a constraint;
Giving the variable load condition set in the variable load condition setting step to the optimization analysis model, performing optimization analysis under the optimization analysis condition, reducing the cumulative damage degree of the joint candidate point, and performing the optimization analysis an optimization analysis step of determining the arrangement of the joint candidate points for the purpose of either improving the rigidity of the model or minimizing the number of the remaining joint candidate points as the optimum arrangement of the joint points. An optimization analysis method for joint positions of a vehicle body, characterized by: 2. The joint of the vehicle body according to claim 1, wherein the optimization analysis step is to perform topology optimization by a density method, and discretization is performed by setting a penalty coefficient to 4 or more in the topology optimization. Location optimization analysis method. A computer for all or part of an automobile body model comprising a plurality of part models consisting of beam elements, planar elements and/or three-dimensional elements, and having initial joining points for joining the plurality of part models as a set of parts. performs each of the following steps to achieve any of the following purposes: improving the rigidity of the vehicle body model, improving the fatigue life of the joints that join the parts assembly in the vehicle body model, and minimizing the number of the joints. A joint position optimization analysis method for a vehicle body for performing an optimization analysis for determining the optimum arrangement of the joint points,
an analysis target model setting step of setting all or part of the vehicle body model as an analysis target model;
an optimization analysis model generation step of generating an optimization analysis model by densely setting all connection candidate points that are candidates for the connection points of the optimal arrangement for the model to be analyzed;
Variable load condition setting for dividing the variable load applied to the optimization analysis model into load conditions of a plurality of different vibration patterns, and setting the variable load conditions as one sequence by combining the load conditions of the respective vibration patterns for a predetermined number of cycles. a step;
A target fatigue life setting step of setting the target fatigue life of the optimization analysis model by the number of sequences of the variable load condition;
In order to perform an optimization analysis that targets the optimization analysis model for optimization, the number of repetitions of fracture at each joint candidate point is obtained for each load condition of each vibration pattern, and the load condition of each vibration pattern is The sum of the ratio of the number of cycles and the number of repetitions to failure for the number of sequences of the variable load conditions set by the target fatigue life setting step is obtained as the cumulative damage degree of each candidate joint point, and the residual is obtained by optimization analysis. A condition relating to the degree of cumulative damage of the joint candidate points to be allowed, a condition relating to the stiffness of the optimization analysis model, and a condition relating to the number of points of the joint candidate points to be left by the optimization analysis are defined as an objective function or an optimization analysis condition setting step to be set as a constraint;
Giving the variable load condition set in the variable load condition setting step to the optimization analysis model, performing optimization analysis under the optimization analysis condition, reducing the cumulative damage degree of the joint candidate point, and performing the optimization analysis an optimization analysis step of retaining the arrangement of the candidate joint points for the purpose of either improving the rigidity of the model or minimizing the number of the remaining candidate joint points as a provisional optimal arrangement of the joint points;
A predetermined number of joint candidate points are selected from the joint candidate points remaining as a provisional optimal arrangement by the optimization analysis, and the selected joint candidate points are set in the analysis target model instead of the initial joint points. a selected junction candidate point setting analysis target model generation step of generating a selected junction candidate point setting analysis target model by
Stress analysis is performed by giving the load condition and constraint condition of each vibration pattern under the variable load condition set in the variable load condition setting step to the selected joint candidate point setting analysis target model, and using the result of the stress analysis a selected joint candidate point performance calculation step of calculating the fatigue life of the selected joint candidate point under the variable load condition and the stiffness of the selected joint candidate point setting analysis target model;
The fatigue life of the joint candidate point in the selected joint candidate point setting analysis target model under the variable load condition and the stiffness of the selected joint candidate point setting analysis target model are the same as the analysis target model in which the initial joint point is set. a determination step of determining whether or not a predetermined performance exceeding is satisfied;
If it is determined in the determination step that the predetermined performance is satisfied, the arrangement of the selected joint candidate points is determined as the optimum layout of the joint points, and in the determination step it is determined that the predetermined performance is not satisfied. If it is, until the predetermined performance is satisfied, the condition regarding the cumulative damage degree of the joint candidate point to remain by the optimization analysis set in the optimization analysis condition setting step, the condition regarding the rigidity of the optimization analysis model, or changing a condition regarding the number of points of the joint candidate points to be left by the optimization analysis, the optimization analysis step, the selected joint candidate setting analysis target model generation step, the selected joint candidate point performance calculation step, and an optimum joint point determination step of repeating the determination step and determining the arrangement of the joint candidate points selected when the predetermined performance is satisfied as the optimum arrangement of the joint points. Optimization analysis method of junction position. For all or part of an automobile body model comprising a plurality of part models consisting of beam elements, planar elements and/or three-dimensional elements, and having initial joint points for joining the plurality of part models as an assembly, Optimization for obtaining the optimum arrangement of the joint points for the purpose of improving the rigidity of the car body model, improving the fatigue life of the joint points that join the assembly of parts in the car body model, or minimizing the number of the joint points. An optimization analysis device for a joint position of a vehicle body to be analyzed,
an analysis target model setting unit that sets all or part of the vehicle body model as an analysis target model;
an optimization analysis model generating unit for generating an optimization analysis model by densely setting all connection candidate points that are candidates for the connection points of the optimal placement for the model to be analyzed;
Variable load condition setting for dividing the variable load applied to the optimization analysis model into load conditions of a plurality of different vibration patterns, and setting the variable load conditions as one sequence by combining the load conditions of the respective vibration patterns for a predetermined number of cycles. Department and
a target fatigue life setting unit that sets the target fatigue life of the optimization analysis model by the number of sequences of the variable load condition;
In order to perform an optimization analysis that targets the optimization analysis model for optimization, the number of repetitions of fracture at each joint candidate point is obtained for each load condition of each vibration pattern, and the load condition of each vibration pattern is The sum of the ratio of the number of cycles and the number of repetitions to failure for the number of sequences of the variable load condition set by the target fatigue life setting unit is obtained as the cumulative damage degree of each candidate joint point, and the residual is obtained by optimization analysis. A condition relating to the degree of cumulative damage of the joint candidate points to be allowed, a condition relating to the stiffness of the optimization analysis model, and a condition relating to the number of points of the joint candidate points to be left by the optimization analysis are defined as an objective function or an optimization analysis condition setting unit that is set as a constraint;
Giving the variable load condition set by the variable load condition setting unit to the optimization analysis model, performing optimization analysis under the optimization analysis condition, reducing the cumulative damage degree of the joint candidate point, and optimizing an optimization analysis unit that obtains the arrangement of the candidate joint points for the purpose of either improving the rigidity of the analysis model or minimizing the number of the candidate joint points to be left as the optimum arrangement of the joint points. An optimization analysis device for a joint position of a vehicle body, characterized by: 5. The vehicle body joint according to claim 4, wherein the optimization analysis unit performs topology optimization by a density method, and discretizes the topology optimization by setting a penalty coefficient to 4 or more. Position optimization analysis device. For all or part of an automobile body model comprising a plurality of part models consisting of beam elements, planar elements and/or three-dimensional elements, and having initial joint points for joining the plurality of part models as an assembly, Optimization for obtaining the optimum arrangement of the joint points for the purpose of improving the rigidity of the car body model, improving the fatigue life of the joint points that join the assembly of parts in the car body model, or minimizing the number of the joint points. An optimization analysis device for a joint position of a vehicle body to be analyzed,
an analysis target model setting unit that sets all or part of the vehicle body model as an analysis target model;
an optimization analysis model generating unit for generating an optimization analysis model by densely setting all connection candidate points that are candidates for the connection points of the optimal placement for the model to be analyzed;
Variable load condition setting for dividing the variable load applied to the optimization analysis model into load conditions of a plurality of different vibration patterns, and setting the variable load conditions as one sequence by combining the load conditions of the respective vibration patterns for a predetermined number of cycles. Department and
a target fatigue life setting unit that sets the target fatigue life of the optimization analysis model by the number of sequences of the variable load condition;
In order to perform an optimization analysis that targets the optimization analysis model for optimization, the number of repetitions of fracture at each joint candidate point is obtained for each load condition of each vibration pattern, and the load condition of each vibration pattern is The sum of the ratio of the number of cycles and the number of repetitions to failure for the number of sequences of the variable load condition set by the target fatigue life setting unit is obtained as the cumulative damage degree of each candidate joint point, and the residual is obtained by optimization analysis. a condition relating to the degree of cumulative damage of the joint candidate points to be allowed, a condition relating to the stiffness of the optimization analysis model, and a condition relating to the number of the joint candidate points to be left in the optimization analysis, as an objective function or an optimization analysis condition setting unit that is set as a constraint;
Giving the variable load condition set by the variable load condition setting unit to the optimization analysis model, performing optimization analysis under the optimization analysis condition, reducing the cumulative damage degree of the joint candidate point, and optimizing an optimization analysis unit that retains, as a provisional optimum arrangement of the joint points, the arrangement of the joint candidate points that is achieved for the purpose of either improving the rigidity of the analysis model or minimizing the number of the remaining joint candidate points; ,
A predetermined number of joint candidate points are selected from the joint candidate points remaining as a provisional optimal arrangement by the optimization analysis, and the selected joint candidate points are set in the analysis target model instead of the initial joint points. a selected junction candidate point setting analysis target model generating unit for generating a selected junction candidate point setting analysis target model by
Stress analysis is performed by giving the load condition and constraint condition of each vibration pattern under the variable load condition set by the variable load condition setting unit to the selected joint candidate point setting analysis target model, and the result of the stress analysis is used. a selected joint candidate point performance calculation unit that calculates the fatigue life of the selected joint candidate point under the variable load condition and the stiffness of the selected joint candidate point setting analysis target model;
The fatigue life of the joint candidate point in the selected joint candidate point setting analysis target model under the variable load condition and the stiffness of the selected joint candidate point setting analysis target model are the same as the analysis target model in which the initial joint point is set. a determination unit that determines whether or not a predetermined performance exceeding is satisfied;
When the determination unit determines that the predetermined performance is satisfied, the arrangement of the selected joining candidate points is determined as the optimal placement of the joining points, and the determination unit determines that the predetermined performance is not satisfied. if it is, until the predetermined performance is satisfied, the condition regarding the cumulative damage degree of the joint candidate point to be left by the optimization analysis set by the optimization analysis condition setting unit, the condition regarding the rigidity of the optimization analysis model, Alternatively, by changing the condition regarding the points of the joint candidate points to be left by the optimization analysis, the optimization analysis unit, the selected joint candidate point setting analysis target model generation unit, the selected joint candidate point performance calculation unit, and an optimum joint point determination unit that repeats the processing by the determination unit and determines the arrangement of the joint candidate points selected when the predetermined performance is satisfied as the optimum arrangement of the joint points. Optimization analysis device for the joint position of the car body. For all or part of an automobile body model comprising a plurality of part models consisting of beam elements, planar elements and/or three-dimensional elements, and having initial joint points for joining the plurality of part models as an assembly, Optimization for obtaining the optimum arrangement of the joint points for the purpose of improving the rigidity of the car body model, improving the fatigue life of the joint points that join the assembly of parts in the car body model, or minimizing the number of the joint points. An optimization analysis program for joint positions of a vehicle body to be analyzed,
the computer,
an analysis target model setting unit that sets all or part of the vehicle body model as an analysis target model;
an optimization analysis model generating unit for generating an optimization analysis model by densely setting all connection candidate points that are candidates for the connection points of the optimal placement for the model to be analyzed;
Variable load condition setting for dividing the variable load applied to the optimization analysis model into load conditions of a plurality of different vibration patterns, and setting the variable load conditions as one sequence by combining the load conditions of the respective vibration patterns for a predetermined number of cycles. Department and
a target fatigue life setting unit that sets the target fatigue life of the optimization analysis model by the number of sequences of the variable load condition;
In order to perform an optimization analysis that targets the optimization analysis model for optimization, the number of repetitions of fracture at each joint candidate point is obtained for each load condition of each vibration pattern, and the load condition of each vibration pattern is The sum of the ratio of the number of cycles and the number of repetitions to failure for the number of sequences of the variable load condition set by the target fatigue life setting unit is obtained as the cumulative damage degree of each candidate joint point, and the residual is obtained by optimization analysis. A condition relating to the degree of cumulative damage of the joint candidate points to be allowed, a condition relating to the stiffness of the optimization analysis model, and a condition relating to the number of points of the joint candidate points to be left by the optimization analysis are defined as an objective function or an optimization analysis condition setting unit that is set as a constraint;
Giving the variable load condition set by the variable load condition setting unit to the optimization analysis model, performing optimization analysis under the optimization analysis condition, reducing the cumulative damage degree of the joint candidate point, and optimizing an optimization analysis unit that obtains the arrangement of the joint candidate points for the purpose of either improving the rigidity of the analysis model or minimizing the number of the remaining joint candidate points as the optimum arrangement of the joint points; An optimization analysis program for joint positions of a vehicle body, characterized by having a function to be executed. 8. The vehicle body joint according to claim 7, wherein the optimization analysis unit performs topology optimization by a density method, and discretizes the topology optimization by setting a penalty coefficient to 4 or more. Position optimization analysis program. For all or part of an automobile body model comprising a plurality of part models consisting of beam elements, planar elements and/or three-dimensional elements, and having initial joint points for joining the plurality of part models as an assembly, Optimization for obtaining the optimum arrangement of the joint points for the purpose of improving the rigidity of the car body model, improving the fatigue life of the joint points that join the assembly of parts in the car body model, or minimizing the number of the joint points. An optimization analysis program for joint positions of a vehicle body to be analyzed,
the computer,
an analysis target model setting unit that sets all or part of the vehicle body model as an analysis target model;
an optimization analysis model generating unit for generating an optimization analysis model by densely setting all connection candidate points that are candidates for the connection points of the optimal placement for the model to be analyzed;
Variable load condition setting for dividing the variable load applied to the optimization analysis model into load conditions of a plurality of different vibration patterns, and setting the variable load conditions as one sequence by combining the load conditions of the respective vibration patterns for a predetermined number of cycles. Department and
a target fatigue life setting unit that sets the target fatigue life of the optimization analysis model by the number of sequences of the variable load condition;
In order to perform an optimization analysis that targets the optimization analysis model for optimization, the number of repetitions of fracture at each joint candidate point is obtained for each load condition of each vibration pattern, and the load condition of each vibration pattern is The sum of the ratio of the number of cycles and the number of repetitions to failure for the number of sequences of the variable load condition set by the target fatigue life setting unit is obtained as the cumulative damage degree of each candidate joint point, and the residual is obtained by optimization analysis. a condition relating to the degree of cumulative damage of the joint candidate points to be allowed, a condition relating to the stiffness of the optimization analysis model, and a condition relating to the number of the joint candidate points to be left in the optimization analysis, as an objective function or an optimization analysis condition setting unit that is set as a constraint;
Giving the variable load condition set by the variable load condition setting unit to the optimization analysis model, performing optimization analysis under the optimization analysis condition, reducing the cumulative damage degree of the joint candidate point, and optimizing an optimization analysis unit that retains, as a provisional optimum arrangement of the joint points, the arrangement of the joint candidate points that is achieved for the purpose of either improving the rigidity of the analysis model or minimizing the number of the remaining joint candidate points; ,
A predetermined number of joint candidate points are selected from the joint candidate points remaining as a provisional optimum arrangement by the optimization analysis, and the selected joint candidate points are set in the analysis target model instead of the initial joint points. a selected junction candidate point setting analysis target model generation unit for generating a selected junction candidate point setting analysis target model by
A stress analysis is performed by giving the load condition and the constraint condition of each vibration pattern under the variable load condition set by the variable load condition setting unit to the selected joint candidate point setting analysis target model, and the result of the stress analysis is used. a selected joint candidate point performance calculation unit that calculates the fatigue life of the selected joint candidate point under the variable load condition and the stiffness of the selected joint candidate point setting analysis target model;
The fatigue life of the joint candidate point in the selected joint candidate point setting analysis target model under the variable load condition and the stiffness of the selected joint candidate point setting analysis target model are the same as the analysis target model in which the initial joint point is set. a determination unit that determines whether or not a predetermined performance exceeding is satisfied;
When the determination unit determines that the predetermined performance is satisfied, the arrangement of the selected joining candidate points is determined as the optimum placement of the joining points, and the determination unit determines that the predetermined performance is not satisfied. if it is, until the predetermined performance is satisfied, the condition regarding the cumulative damage degree of the joint candidate point left by the optimization analysis set by the optimization analysis condition setting unit, the condition regarding the rigidity of the optimization analysis model, Alternatively, by changing the condition regarding the points of the joint candidate points to be left by the optimization analysis, the optimization analysis unit, the selected joint candidate point setting analysis target model generation unit, the selected joint candidate point performance calculation unit, an optimum joint point determination unit for repeating the processing by the determination unit and determining the arrangement of the joint candidate points selected when the predetermined performance is satisfied as the optimum arrangement of the joint points; An optimization analysis program for joint positions of a vehicle body, characterized by comprising:

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