JP7298657B2 - Optimization analysis method and apparatus for joint position of car body - Google Patents

Description

The present invention relates to an optimization analysis method and apparatus for joint positions of a vehicle body, and more particularly to an optimum position of the joint points that improves the rigidity of the vehicle body and the fatigue life of the joint points that join the assembly of parts in the vehicle body. The present invention relates to an optimization analysis method and apparatus for desired joint positions of a vehicle body.

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.
This CAE analysis is known to improve rigidity and reduce weight by using optimization techniques such as mathematical optimization, plate thickness optimization, shape optimization, and topology optimization. It is often used for structural optimization of castings.

Among the optimization techniques, topology optimization is attracting particular attention.
Topology optimization provides a design space of a certain size in a structure, incorporates three-dimensional elements into the design space, satisfies given conditions, and leaves the minimum number of three-dimensional elements to satisfy the conditions. It is a method of obtaining an optimum shape. Therefore, in topology optimization, a method is used in which the three-dimensional elements forming the design space are directly constrained and the load is applied directly.
As a technology related to such topology optimization, Patent Document 1 discloses a method for topology optimization of components of a complex structure.

JP 2010-250818 A

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 cost, it is desirable to reduce the bonding amount as much as possible.

Therefore, in order to improve the rigidity of the car body and the fatigue life of the joint points, there are methods for determining the joint positions (welding positions such as spot welding points) where parts are joined, such as a method of determining the joint position based on experience and intuition, There is a method of determining the joining position 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 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 determining the joint position where the stress is large by stress analysis, although there is a change in rigidity and fatigue life compared to before determining the joint position by this method, the rigidity and fatigue life only in the vicinity of the joint position are reduced. On the other hand, 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, it is conceivable to obtain the optimum position of the junction point by spot welding by the optimization technique disclosed in Patent Document 1. However, the optimization technique is aimed at improving rigidity, and does not consider improvement in fatigue life of joints due to spot welding. Therefore, there has been a demand for a technique for determining the optimum position of joints that can improve the rigidity of the vehicle body and the fatigue life of the joints.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and provides an optimum position of the joints to improve the rigidity of the vehicle body and the fatigue life of the joints that join the assembly of parts in the vehicle body. It is an object of the present invention to provide an optimization analysis method and apparatus for the joint position of a vehicle body for obtaining .

(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 executes the following steps for all or part of an automobile body model having initial joint points that
an analysis target model setting step of setting all or part of the vehicle body model as an analysis target model;
a load/restraint condition setting step of setting load conditions and restraint conditions applied to the model to be analyzed;
a stress analysis step of applying the load condition and the restraint condition to the model to be analyzed and performing a stress analysis;
a target fatigue life setting step of calculating the fatigue life of each of the initial joint points of the model to be analyzed using the results of the stress analysis, and setting a target fatigue life based on the calculated fatigue life of each of the initial joint points; ,
an optimization analysis model generation step of generating an optimization analysis model by densely setting all candidate connection points that are candidates for the optimum connection points for connecting the assembly of parts to the model to be analyzed;
In order to perform an optimization analysis targeting the joint candidate points for optimization, a condition relating to the fatigue life of the joint candidate points to be retained by the optimization analysis based on the target fatigue life set in the target fatigue life setting step is determined, and the conditions related to the fatigue life of the determined joint candidate points, the conditions related to the stiffness of the optimized analysis model, and the conditions related to the number of remaining joint candidate points are combined into an objective function or an optimization analysis condition setting step to be set as a constraint;
The load conditions based on the constraint conditions set in the load/constraint condition setting step are given to the optimization analysis model, optimization analysis is performed under the optimization analysis conditions, and bonding candidates remaining in the optimization analysis and an optimization analysis step of obtaining a point as an optimum joint point for joining the assembly of parts.

(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 executes the following steps for all or part of an automobile body model having initial joint points that
an analysis target model setting step of setting all or part of the vehicle body model as an analysis target model;
a load/restraint condition setting step of setting load conditions and restraint conditions applied to the model to be analyzed;
a stress analysis step of applying the load condition and the restraint condition to the model to be analyzed and performing a stress analysis;
a target fatigue life setting step of calculating the fatigue life of each of the initial joint points of the model to be analyzed using the results of the stress analysis, and setting a target fatigue life based on the calculated fatigue life of each of the initial joint points; ,
an optimization analysis model generation step of generating an optimization analysis model by densely setting all candidate connection points that are candidates for the optimum connection points for connecting the assembly of parts to the model to be analyzed;
In order to perform an optimization analysis targeting the joint candidate points for optimization, a condition relating to the fatigue life of the joint candidate points to be retained by the optimization analysis based on the target fatigue life set in the target fatigue life setting step is determined, and the conditions related to the fatigue life of the determined joint candidate points, the conditions related to the stiffness of the optimized analysis model, and the conditions related to the number of remaining joint candidate points are combined into an objective function or an optimization analysis condition setting step to be set as a constraint;
The load conditions based on the constraint conditions set in the load/constraint condition setting step are given to the optimization analysis model, optimization analysis is performed under the optimization analysis conditions, and bonding candidates remaining in the optimization analysis an optimization analysis step of obtaining a point as an optimal junction point for joining the assembly of parts;
A predetermined number of joint candidate points are selected from the remaining joint candidate points, and the selected joint candidate points are set in the analysis target model in place of the initial joint points to create the selected joint candidate point setting analysis target model. Selected junction candidate point setting analysis target model generation step to be generated;
Stress analysis is performed by applying the load conditions and constraint conditions set in the load/restraint condition setting step to the selected candidate joint point setting analysis target model, and using the results of the stress analysis, fatigue of the selected joint candidate points a selected joint candidate point performance calculation step of calculating the life 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 and the rigidity of the selected joint candidate point setting analysis target model satisfy a predetermined performance exceeding the analysis target model in which the initial joint point is set. a determination step of determining whether
If it is determined in the determining step that the predetermined performance is satisfied, the selected joining candidate point is determined as an optimum bonding point, and if it is determined in the determining step that the predetermined performance is not satisfied, the Until a predetermined performance is satisfied, the conditions regarding the points of the joint candidate points are changed in the optimization analysis condition setting step, and the optimization analysis step, the selected joint candidate point setting analysis target model generation step, and the selected joint and an optimal junction point determination step of repeating the candidate point performance calculation step and the determination step, and determining the junction candidate point selected when the predetermined performance is satisfied as the optimal junction point. It is.

(4) A vehicle body joint 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 analysis target model setting unit that sets all or part of the vehicle body model as an analysis target model;
a load/restraint condition setting unit that sets load conditions and restraint conditions applied to the model to be analyzed;
a stress analysis unit that applies the load condition and the constraint condition to the model to be analyzed and performs a stress analysis;
a target fatigue life setting unit that calculates the fatigue life of each of the initial joint points of the model to be analyzed using the results of the stress analysis, and sets a target fatigue life based on the calculated fatigue life of each of the initial joint points; ,
an optimization analysis model generating unit for generating an optimization analysis model by densely setting all connection candidate points, which are candidates for the optimum connection points for connecting the parts assembly, to the analysis target model;
related to the fatigue life of the joint candidate points to be retained by the optimization analysis based on the target fatigue life set by the target fatigue life setting unit in order to perform the optimization analysis targeting the joint candidate points for optimization; A condition is determined, and an objective function is an optimization analysis condition that includes the determined fatigue life of the joint candidate points, the stiffness of the optimized analysis model, and the number of remaining joint candidate points. Or an optimization analysis condition setting unit that is set as a constraint,
The load conditions based on the constraint conditions set by the load/constraint condition setting unit are given to the optimization analysis model, optimization analysis is performed under the optimization analysis conditions, and the remaining joints in the optimization analysis and an optimization analysis unit that obtains a candidate point as an optimum joint point for joining the assembly of parts.

(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 analysis target model setting unit that sets all or part of the vehicle body model as an analysis target model;
a load/restraint condition setting unit that sets load conditions and restraint conditions applied to the model to be analyzed;
a stress analysis unit that applies the load condition and the constraint condition to the model to be analyzed and performs a stress analysis;
a target fatigue life setting unit that calculates the fatigue life of each of the initial joint points of the model to be analyzed using the results of the stress analysis, and sets a target fatigue life based on the calculated fatigue life of each of the initial joint points; ,
an optimization analysis model generating unit for generating an optimization analysis model by densely setting all connection candidate points, which are candidates for the optimum connection points for connecting the parts assembly, to the analysis target model;
related to the fatigue life of the joint candidate points to be retained by the optimization analysis based on the target fatigue life set by the target fatigue life setting unit in order to perform the optimization analysis targeting the joint candidate points for optimization; A condition is determined, and an objective function is an optimization analysis condition that includes the determined fatigue life of the joint candidate points, the stiffness of the optimized analysis model, and the number of remaining joint candidate points. Or an optimization analysis condition setting unit that is set as a constraint,
The load conditions based on the constraint conditions set by the load/constraint condition setting unit are given to the optimization analysis model, optimization analysis is performed under the optimization analysis conditions, and the remaining joints in the optimization analysis an optimization analysis unit that obtains a candidate point as an optimum joint point for joining the assembly of parts;
A predetermined number of joint candidate points are selected from the remaining joint candidate points, and the selected joint candidate points are set in the analysis target model in place of the initial joint points to create the selected joint candidate point setting analysis target model. a selected joining candidate point setting analysis target model generation unit to generate;
A stress analysis is performed by giving the load conditions and constraint conditions set by the load/restraint condition setting unit to the selected candidate joint point setting analysis target model, and using the results of the stress analysis, the selected joint candidate points are determined. a selected joint candidate point performance calculation unit that calculates the fatigue life and the stiffness of the selected joint candidate point setting analysis object model;
The fatigue life 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 satisfy a predetermined performance exceeding the analysis target model in which the initial joint point is set. a determination unit that determines whether
If the determining unit determines that the predetermined performance is satisfied, the selected joining candidate point is determined as an optimum joining point, and if the determining unit determines that the predetermined performance is not satisfied, the Until a predetermined performance is satisfied, the optimization analysis condition setting unit changes the conditions regarding the points of the joint candidate points, and the optimization analysis unit, the selected joint candidate point setting analysis target model generation unit, and the selected joint an optimal junction point determination unit that repeats the processing by the candidate point performance calculation unit and the determination unit and determines the junction candidate point selected when the predetermined performance is satisfied as the optimal junction point. It is characterized.

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. By setting the optimization analysis conditions (objective function or constraint conditions) related to the number of joint candidate points, the fatigue life of the joint candidate points, and the stiffness of the optimized analysis model, and performing the optimization analysis for the joint candidate points, It is possible to obtain the optimum joint position for the purpose of optimizing the number of joint candidate points, improving the rigidity of the model to be analyzed, and improving the fatigue life of the joints that join the assembly of parts.
This makes it possible to optimize the spot welding points in the vehicle body structure, thereby reducing welding costs and reducing the 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. 1 is a diagram showing a floor model that is a part of a vehicle body model as an example of a model to be analyzed in Embodiment 1 of the present invention ((a) general view, (b) the vicinity of a stiffness evaluation point for evaluating stiffness; ). 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 and constraint conditions applied to a floor model which is a model to be analyzed in Embodiment 1 of the present invention; FIG. 10 is a contour diagram of Z-direction displacement, which is an example of the result of stress analysis of a floor part model, which is a model to be analyzed, in Embodiment 1 of the present invention. 1 is a diagram showing (a) input conditions for calculating fatigue life and (b) an initial joint point with the shortest fatigue life obtained using the result of stress analysis in Embodiment 1 of the present invention. FIG. 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). FIG. 4 is 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 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). In Embodiment 1 and Example of the present invention, the floor part model is the analysis object, and an example of the optimum joint point obtained by the optimization analysis in which the optimization analysis conditions regarding rigidity and fatigue life are set ( (a) perspective view, (b) top view of dotted line 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. 10 is a diagram showing the optimum joint points obtained by the optimization analysis in which the floor part 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 in which the optimum joint points determined by the optimization analysis are set in Example 1. FIG. 5 is a graph showing the shortest fatigue life of the optimum joint points in the floor part model in which the optimum joint points determined by the optimization analysis are set in Example 1. FIG. 10 is a graph showing the number of joint points of a floor model in which optimum joint points determined by optimization analysis are set in Example 2. FIG. 10 is a graph showing the rigidity improvement rate of the floor model in which the optimum joint points determined by the optimization analysis are set in Example 2. FIG. 10 is a graph showing the shortest fatigue life of the floor part model in which the optimum joint points determined by the optimization analysis are set in Example 2. FIG. 10 is a graph showing the shortest fatigue life of the optimum joint points in the floor part model in which the optimum joint points determined by the optimization analysis are set in Example 3. FIG. 10 is a graph showing the rigidity improvement rate of the floor model in which the optimum joint points determined by the optimization analysis are set in Example 3. FIG.

Before describing the optimization analysis method and apparatus 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 this 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. Expressed as the FR axis.
Further, 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 steel plates, so the part models that make up the vehicle 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 element is coupled to the 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 deformation caused by a load acting on 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, a viscoelastic body, or a 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 11).

[Embodiment 1]
<Optimization analysis device for joint position of car body>
The configuration of the vehicle body joint 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 performs an optimization analysis to determine the position of the optimal joint point where a plurality of part models constituting the model to be analyzed are joined as a part assembly. It is a device.

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 composed of 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 and displaying the vehicle body model and the model to be analyzed, and is composed of a keyboard, a mouse, and the like.

≪Storage device≫
The storage device 7 is used for storing various files such as the vehicle body model file 101 and analysis results, and is configured by 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, a load/restraint condition setting unit 15, a stress analysis unit 17, a target fatigue life setting unit 19, and an optimization analysis model generation unit. 21, an optimization analysis condition setting unit 23, and an optimization analysis unit 25, which are 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 the whole or a 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.

In these part models, as shown in FIG. 3, initial joint points 131 to be joined as a part set are set in advance at a predetermined interval D. FIG. 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 form a part assembly.

Hereinafter, in the first embodiment, a case where the floor part model 111 shown in FIG. 2 is used as the model to be analyzed will be described.

(Load/restraint condition setting section)
The load/constraint condition setting unit 15 sets load conditions and constraint conditions applied to the model to be analyzed.

The load conditions and constraint conditions set by the load/constraint condition setting unit 15 are for performing stress analysis by the stress analysis unit 17, and the position, magnitude and direction of the load applied to the analysis target model, , and so on.

FIG. 4 shows load conditions and restraint conditions when a twisting load acts on the floor model 111 about the FR axis.

In setting the load conditions and constraint conditions shown in FIG. 127.
Next, the center of gravity of the front end surface portion 125 is set as the load input point A, and the front end surface portion 125 is coupled with the rigid element. Further, the center of gravity of the rear end surface portion 127 is set as a constraint point B, and the rear end surface portion 127 is coupled with a rigid element.
Then, as the load condition, a moment of 0.1 kN·m is applied to the load input point A around the FR axis, and as the constraint condition, the constraint point B is completely constrained.

(Stress Analysis Department)
The stress analysis unit 17 applies the load conditions and constraint conditions set by the load/constraint condition setting unit 15 to the model to be analyzed to perform stress analysis. Commercially available stress analysis software can be used for stress analysis by the stress analysis unit 17 .

FIG. 5 shows an example of the result of stress analysis by giving the load condition and the restraint condition shown in FIG. 4 to the floor part model 111 . The results shown in FIG. 5 are contour diagrams showing the displacement of the floor model 111 in the Z direction (display magnification of 50 times). Through the stress analysis, in addition to the displacement of the floor model 111, the stress of the planar elements of the part models to which the respective initial joint points 131 of the floor model 111 are connected, the force and moment acting on both ends of each initial joint point 131, etc. can be asked for.

(Target fatigue life setting section)
The target fatigue life setting unit 19 calculates the fatigue life of each initial joint point in the analysis target model using the result of the stress analysis by the stress analysis unit 17, and sets the target fatigue based on the calculated fatigue life of each initial joint point. It sets the lifespan.

For the calculation of the fatigue life of each initial joint point by the target fatigue life setting unit 19, commercially available fatigue life prediction analysis software may be used. For example, when calculating the fatigue life of the initial joint modeled with beam elements using commercially available fatigue life prediction analysis software, the initial The fatigue life of the joint can be calculated. 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.

The target fatigue life is the fatigue life that the remaining joint candidate points (described later) should satisfy by the optimization analysis. The target fatigue life is at least longer than the shortest fatigue life (shortest fatigue life) of each initial joint point calculated by the target fatigue life setting unit 19 .

FIG. 6 shows the input conditions for calculating the fatigue life of the initial joint 131 using the stress analysis results in which the load conditions and constraint conditions shown in FIG. indicates the shortest fatigue life of
In calculating the fatigue life of the initial joint 131, as shown in FIG. given the input conditions.

As shown in FIG. 6(b), the target fatigue life of the initial joint 131 that joins the floor panel model 113 and the front floor cross model 121 or the rear floor cross model 123 is 27,000 times, and the other initial joint 131 The fatigue life was the shortest compared to

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.

(Optimization analysis model generator)
The optimization analysis model generation unit 21 densely sets all candidate connection points that are candidates for the optimum connection points for connecting parts assembly to the model to be analyzed, and generates an optimization analysis model.

FIG. 8 shows, as an example, an optimization analysis model 151 generated by setting joint candidate points 155 in the floor model 111 .

In the floor part model 111, as shown in FIG. 3, initial joint points 131 are set in advance at predetermined intervals D in a set of parts formed by joining a plurality of parts.
In the first embodiment, as shown in FIG. 8, the optimization analysis model generation unit 21 densely creates additional joint points 153 at a predetermined interval d (<D) between the initial joint points 131 in each component assembly. set to 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 joint candidate points by the optimization analysis model generation unit 21, parts to be jointed as a combination of parts in the model to be analyzed, such as making the joint points densest at intervals that can actually increase the additional joint points. Additional junction points may be set according to the size of .

Note that 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.

(Optimization analysis condition setting section)
The optimization analysis condition setting unit 23 determines the joints to be retained by the optimization analysis based on the target fatigue life set by the target fatigue life setting unit 19 in order to perform the optimization analysis targeting the joint candidate points for optimization. The conditions for the fatigue life of the candidate points are determined, and the conditions for the fatigue life of the determined joint candidate points, the conditions for the stiffness of the optimization analysis model, and the conditions for the number of remaining candidate joint points are combined under the optimization analysis conditions. It is set as a certain objective function or constraint.

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. For the condition regarding stiffness, for example, a predetermined position in the model to be analyzed may be used as a stiffness evaluation point, and the displacement or strain at the stiffness evaluation point may be used as an index.

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 is set as a constraint condition.

The condition regarding the fatigue life is not limited to giving the target fatigue life as it is as a constraint condition. For example, a constraint condition may be given in which the stress at the joint candidate point is less than the stress corresponding to the target fatigue life. Here, the stress at the joint candidate point is, for example, the stress of the plane element of the part model to which the beam element modeled as the joint candidate point is connected, or the nominal structural stress calculated from the force and moment acting on both ends of the beam element. , etc. can be used.

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 the first embodiment, the score of the remaining joining candidate point is the score of the initial joining point.

Regarding the optimization analysis condition regarding the number of joint candidate points, for example, when the density method is applied in topology optimization in the optimization analysis by the optimization analysis unit 25 described later, the joint candidate points are modeled. The volume of the joint candidate point calculated based on the density of the elements (beam elements, three-dimensional elements, etc.) may be given as a constraint condition.

(optimization analysis part)
The optimization analysis unit 25 applies load conditions based on the constraint conditions set by the load/constraint condition setting unit 15 to the optimization analysis model, performs optimization analysis under the optimization analysis conditions, and performs optimization analysis. The joint candidate points thus obtained are obtained as the optimum joint points for joining the assembly of parts.

As the optimization analysis by the optimization analysis unit 25, topology optimization can be applied.
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 (1).

A penalty factor of 2 or more is often used for discretization, but a penalty factor 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 planar elements and three-dimensional elements, and 20 or more for beam elements.

The optimization analysis unit 25 may perform optimization analysis by topology optimization as described above, or may perform optimization analysis by another calculation method. As the optimization analysis unit 25, for example, commercially available optimization analysis software using the finite element method can be used.

FIG. 9 shows an example of the optimum junction 157 obtained by the optimization analysis unit 25 applying the density method in the topology optimization and performing the optimization analysis. Note that the effects of the optimum junction points obtained in the first embodiment will be described in Examples described later.

<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 Embodiment 1 of the present invention (hereinafter simply referred to as "optimization analysis method") uses all or part of a vehicle body model as an analysis target model, and As shown in FIG. 10, an analysis target model setting step S1 and a load/restraint condition setting step S3 , a stress analysis step S5, a target fatigue life setting step S7, an optimization analysis model generation step S9, an optimization analysis condition setting step S11, and an optimization analysis step S13.
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.

≪Load/restraint condition setting step≫
The load/constraint condition setting step S3 sets the load conditions and constraint conditions applied to the analysis object model set in the analysis object model setting step S1.

In the first embodiment, in the load/constraint condition setting step S3, the load/constraint condition setting unit 15 of the optimization analysis device 1 sets the load condition and constraint applied to the floor model 111 as shown in FIG. Set conditions.

≪Stress analysis step≫
The stress analysis step S5 applies the load conditions and the constraint conditions set in the load/constraint condition setting step S3 to the model to be analyzed to perform stress analysis.

In the first embodiment, in the stress analysis step S5, the stress analysis unit 17 of the optimization analysis device 1 applies the load conditions and constraint conditions shown in FIG.

<<Target fatigue life setting step>>
The target fatigue life setting step S7 uses the stress analysis result in the stress analysis step S5 to calculate the fatigue life of the initial joint points of the model to be analyzed, and sets the target fatigue life based on the calculated fatigue life of each initial joint point. is to be set.

The target fatigue life is a fatigue life that should be satisfied by the joint candidate points to be optimized, and is at least longer than the shortest fatigue life (shortest fatigue life) of each initial joint point calculated in the target fatigue life setting step S7. Fatigue life.

In the first embodiment, in the target fatigue life setting step S7, the target fatigue life setting unit 19 of the optimization analysis device 1 calculates the fatigue life for the initial joint point of the floor part model 111, and the calculated initial joint point Set the target fatigue life based on the shortest fatigue life of

<<Optimization analysis model generation step>>
In the optimization analysis model generation step S9, an optimization analysis model is generated by densely setting all the joint candidate points, which are candidates for the optimum joint point for joining the assembly of parts, to the model to be analyzed.

In the first embodiment, in the optimization analysis model generation step S9, the optimization analysis model generation unit 21 inserts the additional connection points 153 between the initial connection points 131 preset in the floor part model 111 at a predetermined interval d. (d<D, D: interval between initial joint points), and both initial joint points 131 and additional joint points 153 are set as joint candidate points 155 .

<<Optimization analysis condition setting step>>
In the optimization analysis condition setting step S11, optimization analysis is performed based on the target fatigue life set in the target fatigue life setting step S7 in order to perform optimization analysis targeting the joint candidate points in the optimization analysis model. Then, the conditions for the fatigue life of the determined joint candidate points, the conditions for the stiffness of the optimized analysis model, and the conditions for the number of remaining candidate joint points are optimized. It is set as an objective function or a constraint condition, which is an analytical analysis condition.

In the first embodiment, in the optimization analysis condition setting step S11, the optimization analysis condition setting unit 23 sets the maximization of the stiffness 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 number of initial joint points are set as optimization analysis conditions.

The condition regarding the fatigue life is not limited to giving the target fatigue life as it is as a constraint condition. For example, a constraint condition may be given such that the stress at the joint candidate point is less than the stress corresponding to the target fatigue life. The stress at the joint candidate point is, for example, the stress of the plane element of the part model that the beam element modeled as the joint candidate point is connected to, the nominal structural stress calculated from the force and moment acting on both ends of the beam element, etc. can be used.

<<Optimization Analysis Step>>
In the optimization analysis step S13, the load conditions based on the constraint conditions set in the load/constraint condition setting step S3 are given to the optimization analysis model, and optimization is performed under the optimization analysis conditions set in the optimization analysis condition setting step S11. Analysis is performed, and the joint candidate points remaining in the optimization analysis are obtained as the optimum joint points for joining the assembly of parts.

In the first embodiment, in the optimization analysis step S13, the optimization analysis unit 25 performs optimization analysis with the joint candidate points set in the floor part model 111 as the optimization target, and as shown in FIG. A joint candidate point 155 that satisfies the optimization analysis condition is obtained as an optimum joint point 157 .

As described above, according to the optimization analysis method and apparatus for the joint position of the vehicle body according to the first embodiment, all or part of the vehicle body model of the automobile is used as the analysis target model, and the parts assembly is joined to the analysis target model. Optimization analysis conditions (objective function or constraint conditions) related to the remaining number of joint candidate points to be optimized, fatigue life, and stiffness of the optimization analysis model Optimal joint for the purpose of optimizing the number of joint candidate points, improving the rigidity of the model to be analyzed, and improving the fatigue life of the joints that join parts assembly It is possible to find the position of a point.

[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 of the joint points in the analysis target model in which the joint candidate points with a predetermined number of remaining points from the optimization analysis are set as the optimum joint points and the fatigue life of the analysis target model Both stiffnesses meet the target performance for 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 a predetermined number of optimal junction points based on the result of the optimization analysis, for example, candidate junction points having a density equal to or greater than a certain threshold are selected as optimal junction points, and intermediate density values less than the threshold are selected as optimal junction points. If a joint candidate point is not selected as an optimum joint point, there may be no optimum joint point to be joined as a part set at the position of the joint candidate point that has not been selected.

If the fatigue life of the model to be analyzed is calculated by newly setting the optimum joint obtained in this way in the model to be analyzed, stress will concentrate on the optimum joint and the fatigue life will be lower than the target fatigue life, or the fatigue life of the model to be analyzed will be reduced. A problem may occur in which the stiffness decreases and the fatigue life and/or stiffness of the model to be analyzed for which the optimum joint point is set does not satisfy the predetermined performance.

Therefore, as a result of intensive study to solve the above problem, it is determined whether the fatigue life and rigidity of the model to be analyzed in which the selected joint candidate point is set instead of the initial joint point satisfies the predetermined performance. If it is determined that this is the case, the optimization analysis conditions are changed and the optimization analysis is performed again. .

The optimization analysis method and apparatus for the joint 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 duplicate descriptions of the same components as those of the vehicle body joint position optimization analysis method and apparatus 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 device 31 (hereinafter simply referred to as "optimization analysis device 31") according to Embodiment 2 of the present invention will be described below.

The optimization analysis device 31 is a device that uses all or part of a vehicle body model as a model to be analyzed, and performs optimization analysis to find an optimum joint point for joining a plurality of parts constituting the model to be analyzed as an assembly of parts. , a PC (personal computer), etc., and includes a display device 3, an input device 5, a storage device 7, a working data memory 9, and an arithmetic processing unit 33, as shown in FIG. The display device 3, the input device 5, the storage device 7, and the working 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. 11, the arithmetic processing unit 33 includes an analysis target model setting unit 13, a load/restraint condition setting unit 15, a stress analysis unit 17, a target fatigue life setting unit 19, and an optimization analysis model generation unit. 21, an optimization analysis condition setting unit 23, an optimization analysis unit 25, a selected junction candidate setting analysis target model generation unit 35, a selected junction candidate point performance calculation unit 37, and a determination unit 39. , and an optimum junction determination unit 41, and are configured by a CPU (central processing unit) such as a PC. Each of these units functions when the CPU executes a predetermined program.

Analysis target model setting unit 13, load/restraint condition setting unit 15, stress analysis unit 17, target fatigue life setting unit 19, optimization analysis model generation unit 21, and optimization analysis condition setting in operation processing unit 33 Since the functions of the unit 23 and the optimization analysis unit 25 are the same as those of the first embodiment described above, the selected joint candidate point setting analysis target model generation unit 35 and the selected joint candidate point performance calculation unit 37 will be described below. , and the functions of the determination unit 39 and the optimum junction determination unit 41 will be described.

(Selected joint 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 by the optimization analysis, and uses the selected joint candidate points as the analysis target model instead of the initial joint points. is set to generate the model to be analyzed for setting the selected joining candidate points.

In topology optimization based on the density method, the density of elements (for example, beam elements) modeled as joint candidate points is calculated. It is preferable to select a predetermined number of joint candidate points having an element density equal to or higher than a predetermined threshold value and set them in the analysis model.

(Selected junction candidate point performance calculation unit)
The selected joint candidate point performance calculation unit 37 applies the load conditions and constraint conditions set by the load/constraint condition setting unit 15 to the selected joint candidate point setting analysis target model, performs stress analysis, and uses the results of the stress analysis. The fatigue life of the selected joint candidate points and the stiffness of the selected joint candidate point setting analysis target model are calculated.

The fatigue life of the joint candidate points set in the selected candidate joint point setting analysis target model is the fatigue life of the joint candidate points obtained by the stress analysis of the selected joint candidate point setting analysis target model, similar to the target fatigue life setting unit 19 described above. It can be determined by using stress and commercially available fatigue life analysis software. The stress at the joint candidate point is, for example, the stress of the plane element of the part model that the beam element modeled as the joint candidate point is connected to, the nominal structural stress calculated from the force and moment acting on both ends of the beam element, etc. can be used.

Further, the stiffness of the selected joint candidate point setting analysis target model may be, for example, indexed by the displacement or distortion of the stiffness evaluation point in the selected joint candidate point setting analysis target model.

(Judgment part)
The determination unit 39 determines whether the fatigue life of the candidate joint point set 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 the 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 determining unit 39 determines that the predetermined performance is satisfied, the optimum bonding point determination unit 41 obtains the selected bonding candidate point as the optimal bonding point, and the determining unit 39 determines that the predetermined performance is not satisfied. If the condition is set by the optimization analysis condition setting unit 23 until the fatigue life of the selected candidate joint point and the stiffness of the selected joint candidate point setting analysis object model satisfy the predetermined performance, the condition regarding the number of joint candidate points set by the optimization analysis condition setting unit is changed, and the processing by the optimization analysis unit 25, the selected connection candidate point setting analysis target model generation unit 35, the selected connection candidate point performance calculation unit 37, and the determination unit 39 is repeated, and the predetermined performance is satisfied. The selected joint candidate point is determined as the optimum joint point.

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 increases the number of joint candidate points to be left in the optimization analysis in the optimization analysis condition setting unit 23. It is recommended to change the optimization analysis conditions as follows.

<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 Embodiment 2 of the present invention uses all or part of a vehicle body model as an analysis target model, and a computer executes the following steps to construct the analysis target model. An optimization analysis is performed to determine the position of the optimum joint where a plurality of part models are joined as a part assembly. As shown in FIG. , a stress analysis step S5, a target fatigue life setting step S7, an optimization analysis model generation step S9, an optimization analysis condition setting step S11, an optimization analysis step S13, and a selected joint candidate point setting analysis target model generation step It includes S15, a selected joint candidate performance calculation step S17, a determination step S19, and an optimum joint point determination step S21.

Among the above steps, the analysis target model setting step S1, the load/restraint condition setting step S3, the stress analysis step S5, the target fatigue life setting step S7, the optimization analysis model generation step S9, and the optimization analysis Since the condition setting step S11 and the optimization analysis step S13 are the same as those in the first embodiment described above, the selected junction candidate point setting analysis target model generation step S15 and the selected junction candidate point performance calculation are described below. Step S17, determination step S19, and optimum junction point determination step S21 will be described. Each step of the optimization analysis method according to the second embodiment is performed by the optimization analysis device 31 (FIG. 11) configured by a computer.

<<Selected joint candidate point setting analysis target model generation step>>
The selected joint candidate point setting analysis target model generation step S15 selects a predetermined number of joint candidate points from the joint candidate points remaining by the optimization analysis in the optimization analysis step S13, and converts the selected joint candidate points to initial joint points. is set in the analysis object model instead of to generate the selected joint candidate point setting analysis object model.
In the second embodiment, the selected joining candidate point setting analysis target model generation step S15 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 S17, stress analysis is performed by applying the load conditions and constraint conditions set in the load and constraint condition setting step S3 to the selected joint candidate point setting analysis target model, and using the stress analysis result, The fatigue life of the joint candidate points set in the selected joint candidate point setting analysis target model and the stiffness of the selected joint candidate point setting analysis target model are calculated.
In the second embodiment, the selected joining candidate point performance calculation unit 37 performs the selected joining candidate point performance calculation step S17.

≪Judgment step≫
Determination step S19 determines whether the fatigue life of the joint candidate point set 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 the performance is satisfied.
In the second embodiment, the judgment section 39 performs the judgment step S19.

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≫
Optimal joint point determination step S21 obtains the joint candidate point selected in selected joint candidate point setting analysis target model generation step S15 as the optimum joint point when it is judged in judgment step S19 that the predetermined performance is satisfied, and determines If it is determined in step S19 that the predetermined performance is not satisfied, until the fatigue life of the joint candidate point in the selected joint candidate point setting analysis target model and the stiffness of the selected joint candidate point setting analysis target model satisfy the predetermined performance, In the optimization analysis condition setting step S11, the conditions related to the number of joint candidate points are changed, and the optimization analysis step S13, the selected joint candidate point setting analysis target model generation step S15, the selected joint candidate point performance calculation step S17, and the determination Step S19 is repeated, and the joint candidate point selected when a predetermined performance is satisfied is determined as the optimum joint point. The reason why the predetermined performance may not be satisfied in the judgment step S19 is that there are many joint candidate points with intermediate densities, and the performance is judged by combining them.
In the second embodiment, the optimal junction determination step S21 is performed by the optimal junction determination unit 41. FIG.

As described above, in the optimization analysis method and apparatus 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 points of joint candidate points are optimized and analyzed. It is possible to appropriately determine the optimum joining point for the purpose of improving the rigidity of the target model and improving the fatigue life of the joining point where the parts assembly is joined.

In the above description, a vehicle body model obtained by modeling the entire vehicle body is obtained, 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, 352 initial joint points 131 are set in advance at intervals of 60 mm on the floor model 111, but the interval and number of the initial joint points 131 are limited to this. isn't it.

In addition, the initial joint point 131 was set in advance in the floor section model 111 by the operator or others. However, in the present invention, from 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 twisting load is applied to the floor model 111 about the FR (front to rear) axis, and the load conditions and constraint conditions shown in FIG. However, in the present invention, the load condition and the restraint condition may be appropriately set by assuming the part of the vehicle body to be analyzed and the actual load acting on the vehicle body.

In the first and second embodiments of the present invention, the target performance of the fatigue life of the joint candidate point is set based on the shortest fatigue life (shortest fatigue life) of the initial joint point set in the model to be analyzed. It was something to do.

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. 8), 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 find an optimal junction point to be added to the initial junction point without being targeted.

In the above description, the optimization analysis conditions are set such that the points of the joint candidate points are the same as the points of the initial joint points. You may also set the transformation analysis conditions.

In the first and second embodiments, as optimization analysis conditions, an objective function related to the stiffness of the optimization analysis model 151, and a constraint condition related to the fatigue life of the joint candidate point 155 and the number of remaining joint candidate points However, in the present invention, the objective function related to the number of joint candidate points and the constraint conditions related to the stiffness of the optimization analysis model and the fatigue life of the joint candidate points are optimized and analyzed. It may be set as a condition, or an objective function related to a joint candidate point, a constraint condition related to the number of joint candidate points, and the stiffness of an optimization analysis model may be set as an optimization analysis condition. good.
The effect of the difference between the objective function and the constraint conditions will be explained in the examples described later.

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.

The fixed joint point may be arbitrarily selected, for example, from among the initial joint points, or a fixed joint candidate point is set as a candidate for the fixed joint point, and the stress analysis or optimization analysis of the model to be analyzed is performed separately. , a fixed joint point may be selected from the fixed joint candidate points based on the result.
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 this embodiment, as shown in FIG. 2, a floor model 111, which is a model of the floor of a vehicle body, is targeted. obtained by

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

In the floor part model 111, an initial joining point 131 for joining the part model as a part set is set in advance. The initial joint points 131 were modeled by beam elements connecting the nodes of the plane elements of the part model, the number of initial joint points was 352, and the interval D between the initial joint points 131 was 60 mm.

First, stress analysis was performed by applying the load conditions and restraint conditions shown in FIG. 4 to the floor part model 111 .
Next, the fatigue life of each initial joint point was calculated using the stress at the initial joint point obtained by stress analysis, and the target fatigue life was set based on the shortest fatigue life.

Subsequently, as shown in FIG. 8, an additional joint point 153 is set between the initial joint points 131 on the floor part model 111 at an interval d=20 mm, and the initial joint point 131 and the additional joint point 153 are replaced by joint candidate points 155. An optimization analysis model 151 was densely generated.

Subsequently, load conditions were given under the constraint conditions shown in FIG. 4 and optimization analysis was performed to obtain 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 embodiment, an objective function related to the stiffness of the optimization analysis model 151, a constraint condition related to the fatigue life of the joint candidate points 155 left by the optimization analysis, and a constraint condition related to the number of joint candidate points 155 left by the optimization analysis. was set as an optimization analysis condition as an invention example.

On the other hand, as a comparative example, a comparative example was given in which the stiffness of the optimized analysis model was the objective function and the only constraint condition was the number of joint candidate points, without giving any constraint condition for the fatigue life. .

In the invention example, the constraint on the fatigue life was given as the stress at the joint candidate point 155 being smaller than the stress corresponding to the shortest fatigue life at the initial joint point 131 .

Furthermore, in both the invention example and the comparative example, the stiffness maximization of the optimized analysis model was used as the objective function, and the points of the joint candidate points were used as the constraint conditions. Regarding the stiffness of the optimized analysis model, as shown in FIG. The Z-direction displacement of the evaluation point P was used as an index of stiffness.

FIG. 9 shows the results of the remaining candidate junction points 155 in the inventive example, and FIG. 13 shows the results of the remaining candidate junction points 155 in the comparative example.
Comparing FIG. 9 and FIG. 13, there is a difference in the presence or absence of the joining candidate point 155 between the inventive example and the comparative example in the portion surrounded by the solid-line ellipse and the portion surrounded by the dashed-line ellipse.

Further, the joint candidate points 155 remaining after the optimization analysis are set as the optimum joint points, and as shown in FIGS. The stiffness of 161 and the fatigue life of the optimum joint 157 were calculated.

In calculating the stiffness and fatigue life, stress analysis was first performed by applying load conditions based on the restraint conditions shown in FIG.
As for the stiffness of the optimum junction floor model 161, the displacement of the stiffness evaluation point P (see FIG. 2(b)) obtained by stress analysis was used as an index.
Regarding the fatigue life of the optimum joint 157, the shortest fatigue life among the fatigue lives calculated using the stress of the optimum joint 157 obtained by the stress analysis of the optimum joint floor part model 161 was used as an index. In calculating the fatigue life of the optimum joint 157, the nugget diameter of the optimum joint 157 was set to 5 mm, and the plane element of the part model to which the beam element modeled as the optimum joint 157 was connected was recut into a spider web shape. (See FIG. 7).

Furthermore, the floor part model 111 (FIG. 2) in which the initial joint points 131 are set, and the optimization analysis model 151 in which the initial joint points 131 and the additional joint points 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. 14 shows the results of the rigidity improvement rate of the reference example, the invention example, the reference example and the comparative example, and FIG. 15 shows the result of the shortest fatigue life of the invention example, the reference example, the reference example and the comparative example. The rigidity improvement rate of the optimal joint point floor model 161 in the invention example and the comparative example is obtained based on the displacement of the rigidity evaluation point P in the floor part model 111 of the reference example.

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.
Comparing the invention example and the comparative example, the rigidity improvement rate of the invention example is 1.0%, which is slightly lower than the rigidity improvement rate of 1.9% of the comparative example, but the rigidity is improved compared to the reference example.
Furthermore, the shortest fatigue life of the invention example is 78,000 times, which is 2.9 times longer than the standard example (27,000 times), and is longer than the shortest fatigue life of the comparative example (48,000 times). result (114,000 times).

<Example 2>
The above description is for the case where the optimization analysis is performed with the stiffness of the optimization analysis model 151 (Fig. 8) as the objective function (hereinafter referred to as "Example 1"). When the number of remaining candidate joining points 155 is used as the objective function (hereinafter referred to as "second embodiment"), and when the fatigue life of the remaining candidate joining points 155 by optimization analysis is used as the objective function (hereinafter referred to as (referred to as "Embodiment 3"), the results of the optimization analysis of the joint candidate points 155 set in the optimization analysis model 151 in the same manner as in Embodiment 1 will be described.
Table 1 shows a list of combinations of minimization analysis conditions (objective function and constraint conditions) in Examples 1 to 3.

In the second embodiment, as shown in Table 1, the objective function related to the number of joint candidate points 155 left by the optimization analysis, the constraint conditions related to the fatigue life of the joint candidate points 155 left by the optimization analysis, and the optimization analysis Inventive Example 2 was set in which the constraint conditions regarding the rigidity of the model 151 were set as the optimization analysis conditions.

On the other hand, as a comparison target, as shown in Table 1, the objective function regarding the number of joint candidate points 155 and the constraint regarding only the stiffness of the optimization analysis model 151 are optimized without giving a constraint regarding fatigue life. Comparative Example 2-1 was given as the curing conditions. Also, as a comparative example, a comparative example in which no constraint condition on the rigidity of the optimization analysis model 151 is given and an objective function on the number of joint candidate points 155 and a constraint condition on fatigue life alone are given as optimization conditions. 2-2.

In Invention Example 2, Comparative Examples 2-1 and 2-2, the objective function is to minimize the number of joint candidate points 155 in the optimization analysis model 151 .

In addition, in Invention Example 2 and Comparative Example 2-1, the constraint on the stiffness of the optimization analysis model 151 is set to be greater than the stiffness of the floor model 111 in which the initial joint point 131 is set.
Furthermore, in Invention Example 2 and Comparative Example 2-2, the constraint condition regarding the fatigue life was set so that the stress at the joint candidate point 155 was smaller than the stress corresponding to the shortest fatigue life at the initial joint point 131 .

The joint candidate points 155 remaining by the optimization analysis are set as the optimum joint points 157, and for the optimum joint floor model in which the optimum joint points 157 are set, the number of joint points of the optimum joint points 157, the stiffness of the optimum joint floor model, and , the fatigue life of the optimum junction 157 was calculated.

FIG. 16 shows the results of the number of bonding points of the reference example, reference example, comparative example 2-1, comparative example 2-2, and invention example 2, and FIG. 17 shows the reference example, reference example, comparative example 2-1, and comparative example. FIG. 18 shows the results of the rigidity improvement rate of 2-2 and Invention Example 2, and the shortest fatigue life results of Reference Example, Reference Example, Comparative Example 2-1, Comparative Example 2-2, and Invention Example 2. The reference example and the reference example are the same as those of the first embodiment described above.

In Invention Example 2, Comparative Examples 2-1, and 2-2, the objective function is the number of joint candidate points 155. Therefore, as shown in FIG. 16, the number of joint points can be reduced more than in the reference example. , 6.3% (22 points), 2.8% (10 points), and 0.6% (2 points) respectively.

In addition, since invention example 2 is a constraint condition regarding the stiffness of the optimization analysis model 151 and the fatigue life of the joint candidate point, the stiffness improvement rate is 1.5% as shown in FIG. 17, which is higher than the standard example. Furthermore, as shown in FIG. 18, the shortest fatigue life was 27,000 cycles, which was the same as the standard example (27,000 cycles).

In Comparative Example 2-1, the constraint on the stiffness of the optimization analysis model 151 was given, but the stiffness improvement rate was -0.2% as shown in FIG. 17, which is almost the same as the reference example. Furthermore, since Comparative Example 2-1 does not impose a constraint on fatigue life, as shown in FIG. Decreased.

In Comparative Example 2-2, since the optimization analysis model 151 has a constraint on the fatigue life, the shortest fatigue life was 27,000 cycles as shown in FIG. 18, which is almost the same as the reference example. However, since no constraint was given to the rigidity, the rigidity improvement rate was 0.1% as shown in FIG.

As described above, from the results of the present Example 2, the target conditions for the joint candidate points and the constraint conditions for the stiffness and fatigue life are given as the optimization analysis conditions, and the optimization analysis is performed for the joint candidate points. It was shown that the number of bonding points can be reduced from the initial number of bonding points while maintaining the improvement in ductility and fatigue life, suggesting that this can reduce the manufacturing cost.

<Example 3>
In Example 3, as shown in Table 1 above, the objective function related to the fatigue life of the joint candidate point 155 remaining by the optimization analysis, the constraint condition related to the stiffness of the optimization analysis model 151, and the remaining by the optimization analysis Inventive Example 3 is a case in which a constraint condition regarding the number of joining candidate points 155 is set as an optimization analysis condition.

On the other hand, as a comparison target, as shown in Table 1 above, the objective function related to the fatigue life of the joint candidate point 155 left by the optimization analysis without giving the constraint condition related to the rigidity of the optimization analysis model 151 and the joint Comparative Example 3 is a comparative example 3 in which a constraint condition related only to the number of candidate points 155 is set as an optimization condition.

In Invention Example 3 and Comparative Example, the objective function was to maximize the fatigue life of the joint candidate points 155 remaining by the optimization analysis, and the constraint conditions were the points of the joint candidate points 155 to the initial joint point 131 points.

Further, in Invention Example 3, the constraint condition regarding the stiffness of the optimization analysis model is given as being greater than the stiffness of the floor model 111 for which the initial joint point 131 is set.

The joint candidate points 155 remaining by the optimization analysis are set as the optimum joint points 157, and the stiffness of the optimum joint floor model and the fatigue life of the optimum joint points 157 are calculated for the optimum joint floor model in which the optimum joint points 157 are set. bottom.

FIG. 19 shows the results of the shortest fatigue life of the reference example, reference example, comparative example 3, and invention example 3, and FIG. show. The reference example and the reference example are the same as those of the first embodiment described above.

In both Inventive Example 3 and Comparative Example 3, the number of joint candidate points 155 is a constraint condition, so the number of joint points is 352, which is the same as in the reference example.

In addition, in invention example 3, the fatigue life of the joint candidate point 155 is used as the objective function, so as shown in FIG. bottom. Further, since the stiffness of the optimization analysis model 151 was used as a constraint condition, the stiffness improvement rate was a positive value of 0.9% as shown in FIG.

On the other hand, in Comparative Example 3 as well, since the fatigue life of the joint candidate point 155 was used as the objective function, the shortest fatigue life was 105,000 times, as shown in FIG. Improved. However, since the stiffness of the optimization analysis model 151 is not used as a constraint condition, the stiffness improvement rate is a negative value of -29% as shown in FIG.

As described above, from the results of the present Example 3, as optimization analysis conditions, the target condition regarding the fatigue life and the constraint conditions regarding the number of joint points and rigidity are given, and the optimization analysis is performed for the joint candidate points. It was shown that the rigidity can be improved while maintaining the , and the fatigue life can be maximized.

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 load/restraint condition setting unit 17 stress analysis unit 19 target fatigue life setting unit 21 optimization analysis Model generation unit 23 Optimization analysis condition setting unit 25 Optimization analysis unit 31 Optimization analysis device 33 Arithmetic processing unit 35 Selected joint candidate point setting analysis target model generation unit 37 Selected joint candidate point performance calculation unit 39 Judgment unit 41 Optimal 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 Optimal joint point 161 Optimal joint floor part model

Claims (6)

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. is an optimization analysis method for a joint position of a vehicle body that performs the following steps and performs an optimization analysis to determine the position of the optimum joint point for joining the assembly of parts,
an analysis target model setting step of setting all or part of the vehicle body model as an analysis target model;
a load/restraint condition setting step of setting load conditions and restraint conditions applied to the model to be analyzed;
a stress analysis step of applying the load condition and the restraint condition to the model to be analyzed and performing a stress analysis;
a target fatigue life setting step of calculating the fatigue life of each of the initial joint points of the model to be analyzed using the results of the stress analysis, and setting a target fatigue life based on the calculated fatigue life of each of the initial joint points; ,
an optimization analysis model generation step of generating an optimization analysis model by densely setting all candidate connection points that are candidates for the optimum connection points for connecting the assembly of parts to the model to be analyzed;
In order to perform an optimization analysis targeting the joint candidate points for optimization, a condition relating to the fatigue life of the joint candidate points to be retained by the optimization analysis based on the target fatigue life set in the target fatigue life setting step is determined, and the conditions related to the fatigue life of the determined joint candidate points, the conditions related to the stiffness of the optimized analysis model, and the conditions related to the number of remaining joint candidate points are combined into an objective function or an optimization analysis condition setting step to be set as a constraint;
The load conditions based on the constraint conditions set in the load/constraint condition setting step are given to the optimization analysis model, optimization analysis is performed under the optimization analysis conditions, and bonding candidates remaining in the optimization analysis and an optimization analysis step of finding the point as an optimum joint point for joining the assembly of parts. 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. is an optimization analysis method for a joint position of a vehicle body that performs the following steps and performs an optimization analysis to determine the position of the optimum joint point for joining the assembly of parts,
an analysis target model setting step of setting all or part of the vehicle body model as an analysis target model;
a load/restraint condition setting step of setting load conditions and restraint conditions applied to the model to be analyzed;
a stress analysis step of applying the load condition and the restraint condition to the model to be analyzed and performing a stress analysis;
a target fatigue life setting step of calculating the fatigue life of each of the initial joint points of the model to be analyzed using the results of the stress analysis, and setting a target fatigue life based on the calculated fatigue life of each of the initial joint points; ,
an optimization analysis model generation step of generating an optimization analysis model by densely setting all candidate connection points that are candidates for the optimum connection points for connecting the assembly of parts to the model to be analyzed;
In order to perform an optimization analysis targeting the joint candidate points for optimization, a condition relating to the fatigue life of the joint candidate points to be retained by the optimization analysis based on the target fatigue life set in the target fatigue life setting step is determined, and the conditions related to the fatigue life of the determined joint candidate points, the conditions related to the stiffness of the optimized analysis model, and the conditions related to the number of remaining joint candidate points are combined into an objective function or an optimization analysis condition setting step to be set as a constraint;
The load conditions based on the constraint conditions set in the load/constraint condition setting step are given to the optimization analysis model, optimization analysis is performed under the optimization analysis conditions, and bonding candidates remaining in the optimization analysis an optimization analysis step of obtaining a point as an optimal junction point for joining the assembly of parts;
A predetermined number of joint candidate points are selected from the remaining joint candidate points, and the selected joint candidate points are set in the analysis target model in place of the initial joint points to create the selected joint candidate point setting analysis target model. Selected junction candidate point setting analysis target model generation step to be generated;
Stress analysis is performed by applying the load conditions and constraint conditions set in the load/restraint condition setting step to the selected candidate joint point setting analysis target model, and using the results of the stress analysis, fatigue of the selected joint candidate points a selected joint candidate point performance calculation step of calculating the life 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 and the rigidity of the selected joint candidate point setting analysis target model satisfy a predetermined performance exceeding the analysis target model in which the initial joint point is set. a determination step of determining whether
If it is determined in the determining step that the predetermined performance is satisfied, the selected joining candidate point is determined as an optimum bonding point, and if it is determined in the determining step that the predetermined performance is not satisfied, the Until a predetermined performance is satisfied, the conditions regarding the points of the joint candidate points are changed in the optimization analysis condition setting step, and the optimization analysis step, the selected joint candidate point setting analysis target model generation step, and the selected joint and an optimal junction point determination step of repeating the candidate point performance calculation step and the determination step, and determining the junction candidate point selected when the predetermined performance is satisfied as the optimal junction point. Optimization analysis method of joint position of 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, A vehicle body joint position optimization analysis device for determining the position of the optimum joint point for joining parts assembly,
an analysis target model setting unit that sets all or part of the vehicle body model as an analysis target model;
a load/restraint condition setting unit that sets load conditions and restraint conditions applied to the model to be analyzed;
a stress analysis unit that applies the load condition and the constraint condition to the model to be analyzed and performs a stress analysis;
a target fatigue life setting unit that calculates the fatigue life of each of the initial joint points of the model to be analyzed using the results of the stress analysis, and sets a target fatigue life based on the calculated fatigue life of each of the initial joint points; ,
an optimization analysis model generating unit for generating an optimization analysis model by densely setting all connection candidate points, which are candidates for the optimum connection points for connecting the parts assembly, to the analysis target model;
related to the fatigue life of the joint candidate points to be retained by the optimization analysis based on the target fatigue life set by the target fatigue life setting unit in order to perform the optimization analysis targeting the joint candidate points for optimization; A condition is determined, and an objective function is an optimization analysis condition that includes the determined fatigue life of the joint candidate points, the stiffness of the optimized analysis model, and the number of remaining joint candidate points. Or an optimization analysis condition setting unit that is set as a constraint,
The load conditions based on the constraint conditions set by the load/constraint condition setting unit are given to the optimization analysis model, optimization analysis is performed under the optimization analysis conditions, and the remaining joints in the optimization analysis and an optimization analysis unit that obtains a candidate point as an optimum joint point for joining the assembly of parts. 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, A vehicle body joint position optimization analysis device for determining the position of the optimum joint point for joining parts assembly,
an analysis target model setting unit that sets all or part of the vehicle body model as an analysis target model;
a load/restraint condition setting unit that sets load conditions and restraint conditions applied to the model to be analyzed;
a stress analysis unit that applies the load condition and the constraint condition to the model to be analyzed and performs a stress analysis;
a target fatigue life setting unit that calculates the fatigue life of each of the initial joint points of the model to be analyzed using the results of the stress analysis, and sets a target fatigue life based on the calculated fatigue life of each of the initial joint points; ,
an optimization analysis model generating unit for generating an optimization analysis model by densely setting all connection candidate points, which are candidates for the optimum connection points for connecting the parts assembly, to the analysis target model;
related to the fatigue life of the joint candidate points to be retained by the optimization analysis based on the target fatigue life set by the target fatigue life setting unit in order to perform the optimization analysis targeting the joint candidate points for optimization; A condition is determined, and an objective function is an optimization analysis condition that includes the determined fatigue life of the joint candidate points, the stiffness of the optimized analysis model, and the number of remaining joint candidate points. Or an optimization analysis condition setting unit that is set as a constraint,
The load conditions based on the constraint conditions set by the load/constraint condition setting unit are given to the optimization analysis model, optimization analysis is performed under the optimization analysis conditions, and the remaining joints in the optimization analysis an optimization analysis unit that obtains a candidate point as an optimum joint point for joining the assembly of parts;
A predetermined number of joint candidate points are selected from the remaining joint candidate points, and the selected joint candidate points are set in the analysis target model in place of the initial joint points to create a selected joint candidate point setting analysis target model. a selected joint candidate point setting analysis target model generation unit to generate;
A stress analysis is performed by applying the load conditions and constraint conditions set by the load/constraint condition setting unit to the selected candidate joint point setting analysis target model, and using the results of the stress analysis, the selected joint candidate points are determined. a selected joint candidate point performance calculation unit that calculates the fatigue life 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 and the rigidity of the selected joint candidate point setting analysis target model satisfy a predetermined performance exceeding the analysis target model in which the initial joint point is set. a determination unit that determines whether
If the determining unit determines that the predetermined performance is satisfied, the selected joining candidate point is determined as an optimum joining point, and if the determining unit determines that the predetermined performance is not satisfied, the Until a predetermined performance is satisfied, the optimization analysis condition setting unit changes the condition regarding the number of joint candidate points, and the optimization analysis unit, the selected joint candidate point setting analysis target model generation unit, and the selected joint and an optimum joint point determination unit that repeats the processing by the candidate point performance calculation unit and the determination unit and decides the joint candidate point selected when the predetermined performance is satisfied as the optimum joint point. The optimization analysis device of the joint position of the car body characterized by this.

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