CN116762077A

CN116762077A - Method, device, and program for optimizing and analyzing joint position of vehicle body

Info

Publication number: CN116762077A
Application number: CN202180092036.5A
Authority: CN
Inventors: 时田裕一; 盐崎毅
Original assignee: JFE Steel Corp
Current assignee: JFE Steel Corp
Priority date: 2021-01-27
Filing date: 2021-11-01
Publication date: 2023-09-15

Abstract

The method for optimizing and analyzing the joint position of a vehicle body according to the present invention is a method in which all or a part of a vehicle body model is set as an analysis object model (S1), joint candidate points are densely set for the analysis object model to generate an optimized analysis model (151) (S3), a fluctuating load condition (S5) is set, the inverse of a given target fatigue life is set as a target cumulative damage degree (S7), the rigidity of the optimized analysis model (151) is improved, the inverse of the fatigue life of the joint candidate point (155), namely the reduction of the cumulative damage degree, and the minimization of the number of points of the joint candidate point (155) is set as an optimized analysis condition (S9), the fluctuating load condition is applied to the optimized analysis model (151), and the optimal arrangement (S13) of the joint point (157) for achieving the optimized analysis condition is obtained.

Description

Method, device, and program for optimizing and analyzing joint position of vehicle body

Technical Field

The present invention relates to a method (optimized analysis method), an apparatus, and a program for optimizing and analyzing a joint position (joining positions) of a vehicle body (automatic body), and more particularly, to a method, an apparatus, and a program for optimizing and analyzing a joint position of a vehicle body (automatic body) that improves rigidity of the vehicle body and a joint (joint point) that joins a component group (part assembly) in the vehicle body (fatigue life).

Background

In recent years, particularly in the automobile industry, weight reduction (weight reduction) of a vehicle body due to environmental problems has been advanced, and analysis by computer aided engineering (computer aided engineering) (hereinafter referred to as "CAE analysis") has become an indispensable technique in designing a vehicle body. In this CAE analysis, it is known that the rigidity can be improved and the weight can be reduced by using optimization techniques such as mathematical optimization (mathematical optimization), plate thickness optimization (sheet thickness optimization), shape optimization (shape optimization), and topology optimization (topology optimization).

A structural body (structural body) such as a vehicle body is known to be formed by joining a plurality of members (parts) as a member group by welding (welding) or the like, and if the joining amount in a portion joined as a member group is increased (for example, if a joint by spot welding is increased), the rigidity of the entire vehicle body and the fatigue life of the joint are improved. However, from the viewpoint of manufacturing costs of the vehicle body, it is desirable to reduce the amount of engagement as much as possible.

Therefore, in order to suppress the manufacturing cost of the vehicle body and to improve the rigidity of the vehicle body and the fatigue life of the joint, there are methods for determining the joint position (the welding position such as the spot welding point) where the members are joined to each other, methods for determining the joint position empirically, intuitively, and the like, and methods for setting a position with a large stress as the joint position based on stress analysis (stress analysis).

However, in the method of determining the joining position empirically and intuitively, since the position of the joining point required for improving both the rigidity and the fatigue life is not obtained, there is a case where the position required for improving the rigidity and the fatigue life is set as the joining point, trial and error is repeated, and therefore, it is necessary to say that the efficiency is poor in terms of cost.

In the method of adding the joint around the joint where the stress is large based on the stress analysis, the rigidity and the fatigue life are often improved only in the vicinity of the joint, and the rigidity and the fatigue life of other parts are relatively reduced, although the rigidity and the fatigue life are changed as compared with those before the joint is obtained by the method, and the joint obtained by the method is not necessarily optimal when evaluating the entire vehicle body.

In addition, when the position of the spot-welded joint is obtained by the above-described method, if the positions of adjacent joints are too close to each other, a current (welding current) flows to the adjacent joint (current shunt) welded first, and a sufficient current does not flow to the joint where spot welding is performed next, resulting in poor welding.

Accordingly, patent document 1 discloses a method of obtaining an optimal position of a joint by spot welding by an optimization technique.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open publication No. 2013-025593

Disclosure of Invention

Problems to be solved by the invention

However, the method disclosed in patent document 1 aims at improving rigidity while minimizing the number of points of the joint, and does not consider improvement of fatigue life of the joint based on spot welding at all. Therefore, a technique for obtaining an optimal position of a joint that can minimize the number of points of the joint while improving the rigidity of the vehicle body and the fatigue life of the joint is desired.

In addition, during running of the vehicle, a fluctuation load, in which the amplitude, direction, and the like are not fixed in time but are changed in complexity, is input to the vehicle body. Therefore, a technique for obtaining an optimal position of a joint that can improve the rigidity of a vehicle body and the fatigue life of the joint when a complex fluctuating load is input to the vehicle body is desired.

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an optimal analysis method, device, and program for a joint position of a vehicle body, which, when a variable load is input to the vehicle body of the vehicle, obtains an optimal position of the joint that improves the rigidity of the vehicle body and the fatigue life of the joint that joins a component group in the vehicle body, and minimizes the number of points of the joint.

Means for solving the problems

The method for optimizing and analyzing a joint position of a vehicle body according to the present invention is an optimizing and analyzing method for optimizing and analyzing an optimal arrangement of a joint, which is made up of a plurality of component models including Liang Yaosu (beam element), a planar element (two-dimensional element (two-dimensional element)) and/or a three-dimensional element (three-dimensional element)), and which includes all or a part of an automobile body model (automotive body model) having an initial joint where a plurality of the component models are joined as a component group, and which is performed by a computer by performing the following steps to obtain an optimal arrangement of the joint for any of an improvement in rigidity of the automobile body model, an improvement in fatigue life of a joint joining the component group in the automobile body model, and a minimization of the number of points of the joint, and includes: an analysis object model setting step of setting all or a part of the vehicle body model as an analysis object model (analysis object model); an optimal analysis model generation step of densely (dense) setting all joint candidate (joining candidate) points that are candidates for the joint of the optimal arrangement, with respect to the analysis object model, to generate an optimal analysis model; a variable load condition setting step of setting a load condition (loading condition) for dividing a variable load (variable amplitude load (variable amplitude load)) applied to the optimal analysis model into a plurality of different vibration modes (vibration pattern), and setting the load condition of each vibration mode as a variable load condition of 1 series by combining the load conditions of each vibration mode by a predetermined number of cycles; a target fatigue life setting step of setting a target fatigue life of the optimal analysis model according to the number of times of the sequence of the fluctuating load conditions (target fatigue life); an optimal analysis condition setting step of, for performing optimal analysis with respect to the optimal analysis model, calculating a number of fracture repetitions of each of the joint candidate points for each of the load conditions of each of the vibration modes (number of cycles to failure), calculating a ratio of the number of cycles of the load conditions of each of the vibration modes to the number of fracture repetitions, and setting a sum of the number of sequences of the variable load conditions set by the target fatigue life setting step as a cumulative damage degree (linear cumulative damage (liner cumulative damage)) of each of the joint candidate points, and setting a condition relating to the cumulative damage degree of the joint candidate points retained by the optimal analysis, a condition relating to rigidity of the optimal analysis model, and a condition relating to the number of joint candidate points retained by the optimal analysis as an objective function (targets) or constraint conditions (constraints) as optimal analysis conditions; and an optimization analysis step of applying the fluctuating load condition set in the fluctuating load condition setting step to the optimization analysis model, and performing optimization analysis under the optimization analysis condition, thereby obtaining, as an optimal arrangement of the joint, an arrangement of the joint candidate points achieved with the aim of any one of reduction in the cumulative damage degree of the joint candidate points, improvement in the rigidity of the optimization analysis model, and minimization of the number of points of the joint candidate points that remain.

The optimization analysis step is a step of performing topology optimization by a density method (density), and the optimization may be performed by discretizing (discretization) by setting a penalty coefficient (penalty coefficient) to 4 or more.

The method for optimizing and analyzing a joint position of a vehicle body according to the present invention is a method for optimizing and analyzing an optimal configuration of a joint, which is achieved for any of an improvement in rigidity of the vehicle body model, an improvement in fatigue life of a joint joining the component groups in the vehicle body model, and a minimization of the number of points of the joint, with respect to all or a part of a vehicle body model having a plurality of component models including a beam element, a planar element, and/or a three-dimensional element and having an initial joint in which the plurality of component models are joined as a component group, by executing the following steps by a computer: an analysis object model setting step of setting all or a part of the vehicle body model as an analysis object model; an optimal analysis model generation step of densely setting all joint candidate points that are candidates for the optimally arranged joint for the analysis object model, and generating an optimal analysis model; a variable load condition setting step of setting a variable load condition for dividing a variable load applied to the optimal analysis model into a plurality of different vibration modes, and setting the variable load condition for each vibration mode as a variable load condition of 1 series by combining the load conditions for each vibration mode by a predetermined number of cycles; a target fatigue life setting step of setting a target fatigue life of the optimal analysis model according to the number of sequences of the variable load conditions; an optimal analysis condition setting step of calculating, for each of the load conditions of the vibration modes, a number of fracture repetitions of each of the joint candidate points, and a ratio of the number of cycles to the number of fracture repetitions of the load condition of the vibration modes, the sum of the number of sequences of the variable load conditions set by the target fatigue life setting step, being a cumulative damage degree of each of the joint candidate points, and setting, as an objective function or constraint condition as an optimal analysis condition, a condition relating to a cumulative damage degree of the joint candidate points retained by the optimal analysis, a condition relating to rigidity of the optimal analysis model, and a condition relating to a number of points of the joint candidate points retained by the optimal analysis, in order to perform the optimal analysis with respect to the optimal analysis of the optimal analysis model; an optimization analysis step of assigning the fluctuating load condition set in the fluctuating load condition setting step to the optimization analysis model, and performing optimization analysis under the optimization analysis condition, wherein the configuration of the joint candidate points, which is achieved for the purpose of any one of reduction in the cumulative damage degree of the joint candidate points, improvement in the rigidity of the optimization analysis model, and minimization of the number of points of the joint candidate points that remain, is retained as a temporary optimal configuration of the joint points; a joint candidate point setting analysis object model generation step of selecting a joint candidate point of a predetermined number from the joint candidate points which are retained as a temporary optimal arrangement by the optimization analysis, and setting the selected joint candidate point in the analysis object model in place of the initial joint, thereby generating a joint candidate point setting analysis object model; a selected joint candidate performance calculation step of performing stress analysis by applying a load condition and a constraint condition of each vibration mode in the fluctuating load condition set in the fluctuating load condition setting step to the selected joint candidate setting analysis object model, and calculating a fatigue life of the selected joint candidate under the fluctuating load condition and a rigidity of the selected joint candidate setting analysis object model using a result of the stress analysis; a determination step of determining whether or not a fatigue life of the joining candidate point in the joining candidate point set analysis object model under the fluctuating load condition and a rigidity of the joining candidate point set analysis object model satisfy a given performance exceeding the analysis object model for which the initial joining point is set; and an optimal joint determination step of determining the arrangement of the selected joint candidate points as the optimal arrangement of the joint when the determination step determines that the given performance is satisfied, and changing, when the determination step determines that the given performance is not satisfied, a condition related to the cumulative damage degree of the joint candidate points retained by the optimization analysis, a condition related to the rigidity of the optimization analysis model, or a condition related to the number of points of the joint candidate points retained by the optimization analysis, which are set in the optimization analysis condition setting step, until the given performance is satisfied, and repeating the optimization analysis step, the selected joint candidate point setting analysis object model generation step, the selected joint candidate point performance calculation step, and the determination step, and determining the arrangement of the selected joint candidate points as the optimal arrangement of the joint when the given performance is satisfied.

An optimal analysis device for an optimal arrangement of a joint, which is configured to obtain an optimal arrangement of the joint for any of an improvement in rigidity of a vehicle body model, an improvement in fatigue life of a joint for joining a component group in the vehicle body model, and a minimization of the number of points of the joint, for all or a part of a vehicle body model including a plurality of component models including a beam element, a planar element, and/or a three-dimensional element and including an initial joint for joining the plurality of component models as the component group, the optimal analysis device for the joint of the vehicle body comprises: an analysis object model setting unit that sets all or a part of the vehicle body model as an analysis object model; an optimal analysis model generation unit that generates an optimal analysis model by densely setting all joint candidate points that are candidates for the optimally arranged joint points for the analysis object model; a variable load condition setting unit that sets a variable load condition for dividing a variable load applied to the optimal analysis model into a plurality of different vibration modes, and sets a variable load condition for each of the vibration modes by combining the load conditions for a predetermined number of cycles into 1 series; a target fatigue life setting unit that sets a target fatigue life of the optimal analysis model based on the number of times the load conditions are varied; an optimal analysis condition setting unit that obtains a number of fracture repetitions of each of the joint candidate points for each of the load conditions of each of the vibration modes, obtains a ratio of the number of cycles of the load conditions of each of the vibration modes to the number of fracture repetitions, sets a sum of the number of sequences of the variable load conditions set by the target fatigue life setting unit as a cumulative damage degree of each of the joint candidate points, and sets a condition relating to a cumulative damage degree of the joint candidate points retained by the optimal analysis, a condition relating to rigidity of the optimal analysis model, and a condition relating to a number of points of the joint candidate points retained by the optimal analysis as an objective function or a constraint condition as an optimal analysis condition; and an optimization analysis unit configured to apply the variable load condition set by the variable load condition setting unit to the optimization analysis model, and perform optimization analysis under the optimization analysis condition, thereby obtaining, as an optimal arrangement of the joint, an arrangement of the joint candidate points achieved for any of a reduction in cumulative damage degree of the joint candidate points, an improvement in rigidity of the optimization analysis model, and a minimization of the number of points of the joint candidate points that remain.

The optimization analysis unit may perform topology optimization by a density method, and the optimization analysis unit may discretize the optimization by setting a penalty factor to 4 or more.

An optimal analysis device for an optimal arrangement of a joint, which is configured to obtain an optimal arrangement of the joint for any of an improvement in rigidity of a vehicle body model, an improvement in fatigue life of a joint for joining a component group in the vehicle body model, and a minimization of the number of points of the joint, for all or a part of a vehicle body model including a plurality of component models including a beam element, a planar element, and/or a three-dimensional element and including an initial joint for joining the plurality of component models as the component group, the optimal analysis device for the joint of the vehicle body comprises: an analysis object model setting unit that sets all or a part of the vehicle body model as an analysis object model; an optimal analysis model generation unit that generates an optimal analysis model by densely setting all joint candidate points that are candidates for the optimally arranged joint points for the analysis object model; a variable load condition setting unit that sets a variable load condition for dividing a variable load applied to the optimal analysis model into a plurality of different vibration modes, and sets a variable load condition for each of the vibration modes by combining the load conditions for a predetermined number of cycles into 1 series; a target fatigue life setting unit that sets a target fatigue life of the optimal analysis model based on the number of times the load conditions are varied; an optimal analysis condition setting unit that obtains a number of fracture repetitions of each of the joint candidate points for each of the load conditions of each of the vibration modes, obtains a ratio of the number of cycles of the load conditions of each of the vibration modes to the number of fracture repetitions, sets a sum of the number of sequences of the variable load conditions set by the target fatigue life setting unit as a cumulative damage degree of each of the joint candidate points, and sets a condition related to a cumulative damage degree of the joint candidate points retained by the optimal analysis, a condition related to rigidity of the optimal analysis model, and a condition related to a number of points of the joint candidate points retained in the optimal analysis as an objective function or a constraint condition as an optimal analysis condition; an optimization analysis unit configured to assign the fluctuating load condition set by the fluctuating load condition setting unit to the optimization analysis model, perform optimization analysis under the optimization analysis condition, and retain, as a temporary optimal arrangement of the joint, an arrangement of the joint candidate points achieved for any of a reduction in a cumulative damage degree of the joint candidate points, an improvement in rigidity of the optimization analysis model, and a minimization of the number of points of the retained joint candidate points; a joint candidate point setting analysis target model generation unit configured to select a joint candidate point of a predetermined number from the joint candidate points held as a temporary optimal arrangement by the optimization analysis, and set the selected joint candidate point in the analysis target model in place of the initial joint, to generate a joint candidate point setting analysis target model; a selected joint candidate performance calculation unit configured to apply a load condition and a constraint condition of each vibration mode in the fluctuating load condition set by the fluctuating load condition setting unit to the selected joint candidate setting analysis object model, perform stress analysis, and calculate a fatigue life of the selected joint candidate under the fluctuating load condition and a rigidity of the selected joint candidate setting analysis object model using a result of the stress analysis; a determination unit configured to determine whether or not a fatigue life of the joint candidate point in the joint candidate point setting analysis object model under the fluctuating load condition and a rigidity of the joint candidate point setting analysis object model satisfy a predetermined performance exceeding the analysis object model for which the initial joint point is set; and an optimal joint determination unit that determines the arrangement of the selected joint candidate points as the optimal arrangement of the joint when the determination unit determines that the predetermined performance is satisfied, and repeatedly performs processing based on the optimization analysis unit, the selected joint candidate point setting analysis object model generation unit, the selected joint candidate point performance calculation unit, and the determination unit until the predetermined performance is satisfied, and determines the arrangement of the selected joint candidate points as the optimal arrangement of the joint when the predetermined performance is satisfied by changing a condition related to a cumulative damage degree of the joint candidate points retained by the optimization analysis, a condition related to rigidity of the optimization analysis model, or a condition related to the number of points of the joint candidate points retained by the optimization analysis, which are set by the optimization analysis condition setting unit, when the determination unit determines that the predetermined performance is not satisfied.

An optimization analysis program for a joint position of a vehicle body according to the present invention is an optimization analysis program for an optimal arrangement of a joint, which is achieved for any one of the purposes of improving rigidity of a vehicle body model, improving fatigue life of a joint joining a component group in the vehicle body model, and minimizing the number of points of the joint, for all or a part of a vehicle body model including a plurality of component models including a beam element, a planar element, and/or a three-dimensional element and including an initial joint where a plurality of component models are joined as a component group, the optimization analysis program for a joint position of a vehicle body including a function of causing a computer to execute: an analysis object model setting unit that sets all or a part of the vehicle body model as an analysis object model; an optimal analysis model generation unit that generates an optimal analysis model by densely setting all joint candidate points that are candidates for the optimally arranged joint points for the analysis object model; a variable load condition setting unit that sets a variable load condition for dividing a variable load applied to the optimal analysis model into a plurality of different vibration modes, and sets a variable load condition for each of the vibration modes by combining the load conditions for a predetermined number of cycles into 1 series; a target fatigue life setting unit that sets a target fatigue life of the optimal analysis model based on the number of times the load conditions are varied; an optimal analysis condition setting unit that obtains a number of fracture repetitions of each of the joint candidate points for each of the load conditions of each of the vibration modes, obtains a ratio of the number of cycles of the load conditions of each of the vibration modes to the number of fracture repetitions, sets a sum of the number of sequences of the variable load conditions set by the target fatigue life setting unit as a cumulative damage degree of each of the joint candidate points, and sets a condition relating to a cumulative damage degree of the joint candidate points retained by the optimal analysis, a condition relating to rigidity of the optimal analysis model, and a condition relating to a number of points of the joint candidate points retained by the optimal analysis as an objective function or a constraint condition as an optimal analysis condition; and an optimization analysis unit configured to apply the variable load condition set by the variable load condition setting unit to the optimization analysis model, and perform optimization analysis under the optimization analysis condition, thereby obtaining, as an optimal arrangement of the joint, an arrangement of the joint candidate points achieved for any of a reduction in cumulative damage degree of the joint candidate points, an improvement in rigidity of the optimization analysis model, and a minimization of the number of points of the joint candidate points that remain.

An optimization analysis program for a joint position of a vehicle body according to the present invention is an optimization analysis program for an optimal arrangement of a joint, which is achieved for any one of the purposes of improving rigidity of a vehicle body model, improving fatigue life of a joint joining a component group in the vehicle body model, and minimizing the number of points of the joint, for all or a part of a vehicle body model including a plurality of component models including a beam element, a planar element, and/or a three-dimensional element and including an initial joint where a plurality of component models are joined as a component group, the optimization analysis program for a joint position of a vehicle body including a function of causing a computer to execute: an analysis object model setting unit that sets all or a part of the vehicle body model as an analysis object model; an optimal analysis model generation unit that generates an optimal analysis model by densely setting all joint candidate points that are candidates for the optimally arranged joint points for the analysis object model; a variable load condition setting unit that sets a variable load condition for dividing a variable load applied to the optimal analysis model into a plurality of different vibration modes, and sets a variable load condition for each of the vibration modes by combining the load conditions for a predetermined number of cycles into 1 series; a target fatigue life setting unit that sets a target fatigue life of the optimal analysis model based on the number of times the load conditions are varied; an optimal analysis condition setting unit that obtains a number of fracture repetitions of each of the joint candidate points for each of the load conditions of each of the vibration modes, obtains a ratio of the number of cycles of the load conditions of each of the vibration modes to the number of fracture repetitions, sets a sum of the number of sequences of the variable load conditions set by the target fatigue life setting unit as a cumulative damage degree of each of the joint candidate points, and sets a condition related to a cumulative damage degree of the joint candidate points retained by the optimal analysis, a condition related to rigidity of the optimal analysis model, and a condition related to a number of points of the joint candidate points retained in the optimal analysis as an objective function or a constraint condition as an optimal analysis condition; an optimization analysis unit configured to assign the fluctuating load condition set by the fluctuating load condition setting unit to the optimization analysis model, perform optimization analysis under the optimization analysis condition, and retain, as a temporary optimal arrangement of the joint, an arrangement of the joint candidate points achieved for any of a reduction in a cumulative damage degree of the joint candidate points, an improvement in rigidity of the optimization analysis model, and a minimization of the number of points of the retained joint candidate points; a joint candidate point setting analysis target model generation unit configured to select a joint candidate point of a predetermined number from the joint candidate points held as a temporary optimal arrangement by the optimization analysis, and set the selected joint candidate point in the analysis target model in place of the initial joint, to generate a joint candidate point setting analysis target model; a selected joint candidate performance calculation unit configured to apply a load condition and a constraint condition of each vibration mode in the fluctuating load condition set by the fluctuating load condition setting unit to the selected joint candidate setting analysis object model, perform stress analysis, and calculate a fatigue life of the selected joint candidate under the fluctuating load condition and a rigidity of the selected joint candidate setting analysis object model using a result of the stress analysis; a determination unit configured to determine whether or not a fatigue life of the joint candidate point in the joint candidate point setting analysis object model under the fluctuating load condition and a rigidity of the joint candidate point setting analysis object model satisfy a predetermined performance exceeding the analysis object model for which the initial joint point is set; and an optimal joint determination unit that determines the arrangement of the selected joint candidate points as the optimal arrangement of the joint when the determination unit determines that the predetermined performance is satisfied, and repeatedly performs processing based on the optimization analysis unit, the selected joint candidate point setting analysis object model generation unit, the selected joint candidate point performance calculation unit, and the determination unit until the predetermined performance is satisfied, and determines the arrangement of the selected joint candidate points as the optimal arrangement of the joint when the predetermined performance is satisfied by changing a condition related to a cumulative damage degree of the joint candidate points retained by the optimization analysis, a condition related to rigidity of the optimization analysis model, or a condition related to the number of points of the joint candidate points retained by the optimization analysis, which are set by the optimization analysis condition setting unit, when the determination unit determines that the predetermined performance is not satisfied.

Effects of the invention

In the present invention, by setting all or a part of the automobile body model as the analysis target model, generating an optimized analysis model in which joint candidate points for joining the component groups are set for the analysis target model, setting optimized analysis conditions (objective function or constraint condition) concerning the number of joint candidate points to be optimized, the fatigue life of the joint candidate points, the rigidity of the optimized analysis model, and the number of joints, and performing optimized analysis for the joint candidate points, it is possible to obtain an optimal position of a joint that can be achieved for the purpose of minimizing the number of joint candidate points, improving the rigidity of the analysis target model, and improving the fatigue life of the joints of the joint component groups when a variable load, such as an actual automobile running, that is not fixed in time load, is input to the automobile body. This can improve the fatigue life of spot welding, the rigidity of the vehicle body, and reduce the welding cost, and the rigidity and weight of the vehicle body.

Drawings

Fig. 1 is a block diagram (block diagram) of an apparatus for optimizing and analyzing a joint position of a vehicle body according to embodiment 1 of the present invention.

Fig. 2 is a diagram showing an example of a floor part model (floor structural member model (floor structure member model)) which is a model to be analyzed, and a load condition (moment about the FR axis) and a constraint condition (constraint condition) which are given to the floor part model in embodiment 1 of the present invention.

Fig. 3 is a diagram ((a) perspective view and (b) interval between initial joints) which are preset in the bottom plate portion model as an example of the analysis object model in embodiment 1 of the present invention.

Fig. 4 is a diagram showing an example of a load condition (moment about the RL axis) and a constraint condition of the second vibration mode given to the floor portion model as the analysis target model in embodiment 1 of the present invention.

Fig. 5 is a diagram showing an example of an optimized analysis model in which an initial junction point set in advance in an analysis object model and an additional junction point densely added to the analysis object model are set as junction candidate points in embodiment 1 of the present invention ((a) optimized analysis model, (b) junction candidate points set in the optimized analysis model).

Fig. 6 is a diagram showing an example of the variable load conditions set in embodiment 1 of the present invention.

Fig. 7 is a diagram illustrating an S-N line graph (S-N Curve) used in the calculation of fatigue life under varying load conditions in embodiment 1.

Fig. 8 is a diagram showing an example of the results of the position of the initial joint in which the fatigue life of the initial joint and the fatigue life of the lowest lower 3 points (the shortest fatigue life) are varied under the load condition in embodiment 1 of the present invention.

Fig. 9 is a diagram showing an example of a spot welding portion (welding portion) after modeling an initial joint in the calculation of the fatigue life of the initial joint in embodiment 1 of the present invention ((a) plan view, (b) perspective view).

Fig. 10 is a diagram showing an example of the optimal arrangement of the joint obtained by the optimization analysis in which the bottom plate portion model is set as the analysis target and the optimization analysis conditions concerning the rigidity and the fatigue life in embodiment 1 and example 1 of the present invention (a perspective view and (b enlarged view of a broken line frame).

Fig. 11 is a flowchart showing a flow of processing in the method for optimizing and analyzing the joint position of the vehicle body according to embodiment 1 of the present invention.

Fig. 12 is a block diagram of an optimizing and analyzing device for a joint position of a vehicle body according to embodiment 2 of the present invention.

Fig. 13 is a flowchart showing a flow of processing in the method for optimizing and analyzing the joint position of the vehicle body according to embodiment 2 of the present invention.

Fig. 14 is a diagram showing a floor portion model as a part of a vehicle body model to be analyzed in example 1 ((a) overall diagram, and (b) enlarged diagram in the vicinity of a rigidity evaluation point for evaluating rigidity).

Fig. 15 is a diagram showing an optimal arrangement of joints obtained by optimizing analysis in which the floor section model is set as an analysis target and the rigidity-related optimizing analysis conditions are set in example 1.

Fig. 16 is a graph showing the rigidity improvement rate (improvement rate of stiffness) of the floor section model in which the optimal arrangement of the joints obtained by the optimization analysis is set in example 1.

Fig. 17 is a graph showing the magnification of the shortest fatigue life of the joint in the bottom plate portion model in which the optimal arrangement of the joint is set based on the shortest fatigue life of the initial joint in the bottom plate portion model in which only the initial joint is set in example 1.

Fig. 18 is a diagram illustrating a vehicle body model to be analyzed in example 2 and a variable load condition applied in the optimal analysis of the joint ((a) load condition and constraint condition of the first vibration mode, and (b) load condition and constraint condition of the second vibration mode).

Fig. 19 is a graph showing the results of (a) the shortest fatigue life ratio (minimum fatigue life ratio), (b) the rigidity improvement ratio, and (c) the number of joints of the vehicle body model of the joint obtained by the optimization analysis for each of conditions 1 to 3 in which the combination of the objective function and the constraint condition of the optimization analysis condition is changed in example 2.

Detailed Description

Before explaining the method, apparatus, and program for optimizing and analyzing the joint position of the vehicle body according to embodiment 1 and embodiment 2 of the present application, a vehicle body model which is an object of the present application will be described. In the description of the present application and the drawings, the X direction, the Y direction, and the Z direction are respectively referred to as the vehicle body front-rear direction, the vehicle body left-right direction, and the vehicle body up-down direction. In the present specification and the drawings, elements having substantially the same functions and structures are denoted by the same reference numerals, and overlapping descriptions thereof are omitted.

< vehicle body model and analysis object model >

In the present application, a body model to be subjected to the present application is composed of a plurality of component models such as body's frame members (body parts) and chassis members (chassis component), and these component models are modeled using beam elements, planar elements and/or three-dimensional elements.

In general, since a body frame member, a chassis member, and the like are mainly formed of a metal plate having a relatively thin plate thickness, a component model constituting a body model may be constituted only by planar elements.

Further, the vehicle body model has an initial joint point where a plurality of component models are joined as a component group. The initial joining point is a joining point obtained by modeling spot welds obtained by joining a plurality of automobile parts as a part group using beam elements and solid elements.

For example, when two component models composed of planar elements are joined by an initial joint modeled by beam elements, the planar elements of both component models are joined by the beam elements.

In addition, when the initial joining point is modeled using a three-dimensional element, in order to distribute a translational force (translational force) acting on the initial joining point to the component model, a planar element of the component model and the three-dimensional element of the initial joining point are joined by a rigid element (rigid body element).

In the present invention, deformation caused by application of a fluctuating load to an analysis object model (described later) that is the whole or part of a vehicle body model is analyzed, and therefore, each component model in the vehicle body model is modeled as an elastic body (elastic body) or a viscoelastic body (viscoelastic body) or a plastic body. Further, the material characteristics (material property) and the element information (element information) of each component model constituting the vehicle body model, and further, information on the initial junction or the like in each component group are stored in the vehicle body model file 101 (see fig. 1 and 12).

Embodiment 1

< device for optimizing and analyzing the joint position of a vehicle body >

The configuration of an optimizing and analyzing device (hereinafter, simply referred to as "optimizing and analyzing device") for a joint position of a vehicle body according to embodiment 1 of the present invention will be described below.

The optimization analysis device is a device that uses all or a part of a vehicle body model as an analysis target model, and performs optimization analysis for obtaining an optimal arrangement of joints for the analysis target model, the optimal arrangement being achieved with the aim of any one of improvement in rigidity of the vehicle body model, improvement in fatigue life of joints joining component groups in the vehicle body model, and minimization of the number of points of the joints.

Fig. 1 shows an example of the configuration of an optimal analysis device 1 according to embodiment 1. As shown in fig. 1, the optimum analysis device 1 is configured by a PC (personal computer) or the like, and includes a display device (display device) 3, an input device (input device) 5, a memory storage device (memory storage) 7, a data memory (working data memory) 9 for work, and an arithmetic processing unit (arithmetic processing means (arithmetic processing unit)) 11. The display device 3, the input device 5, the storage device 7, and the work data memory 9 are connected to the arithmetic processing unit 11, and execute respective functions in accordance with instructions from the arithmetic processing unit 11. The functions of the components of the optimal analysis device 1 according to embodiment 1 will be described below.

Display device

The display device 3 is used for displaying a vehicle body model, an analysis object model, and further analysis results, and is configured by a liquid crystal monitor (LCD monitor) or the like.

Input device

The input device 5 is used for reading a vehicle body model file 101 (fig. 1), displaying a vehicle body model and an analysis object model, and inputting instructions from an operator, and is configured by a keyboard, a mouse, and the like.

Storage device

The storage device 7 is used for storing various files such as a vehicle body model file 101 (fig. 1), analysis results, and the like, and is constituted by a hard disk or the like.

Data storage for work

The work data memory 9 is used for temporary storage and calculation of data used by the arithmetic processing unit 11, and is constituted by a RAM (random access memory (Random Access Memory)) or the like.

Arithmetic processing unit

As shown in fig. 1, the arithmetic processing unit 11 includes an analysis object model setting unit 13, an optimal analysis model generating unit 15, a variable load condition setting unit 17, a target fatigue life setting unit 19, an optimal analysis condition setting unit 21, and an optimal analysis unit 23, and is configured by a CPU (central processing unit) such as a PC. These sections function by executing a given program by the CPU. The functions of each unit of the arithmetic processing unit 11 will be described below.

(analysis object model setting part)

The analysis object model setting unit 13 acquires the vehicle body model from the vehicle body model file 101, and sets the whole or a part of the acquired vehicle body model as the analysis object model.

An example of the processing performed by the analysis object model setting unit 13 is described below. First, the operator instructs reading of the vehicle body model from the vehicle body model file 101 through the input device 5, and thereby 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 an instruction from the operator. Then, in accordance with an instruction from the operator, a part to be subjected to optimization analysis is specified in the vehicle body model displayed on the display device 3. The analysis object model setting unit 13 sets the specified portion as an analysis object model.

Fig. 2 shows an example in which a floor portion model 111 that is a simplified and modeled floor portion that is a part of a vehicle body is set as an analysis object model.

The floor section model 111 is configured to have a floor panel (floor panel) model 113, a tunnel (floor tunnel member (floor tunnel member)) model 115, a mount inside (mount inside) model 117, a mount outside (mount outside) model 119, a front floor cross member (front floor cross member)) model 121, and a rear floor cross member (rear floor cross member)) model 123 as component models. The mount inside model 117 and the mount outside model 119 are each formed by joining three members that are connected in the vehicle body front-rear direction.

As shown in fig. 3, in these component models, initial joints 131 for joining component groups are preset at predetermined intervals P. The initial joint 131 is modeled by, for example, beam elements that join nodes (nodes) such as plane elements of a plurality of component models that constitute a component group.

Further, since the fluctuating load condition and the constraint condition applied to the floor section model 111 are set by the fluctuating load condition setting unit 17 described later, the front end surface and the rear end surface of the floor panel model 113 and the tunnel model 115 in the floor section model 111 are respectively joined by rigid elements to generate the front end surface portion 125 and the rear end surface portion 127 as shown in fig. 2 and 4. Here, the center of gravity (center of gravity) of the front end surface portion 125 is set as a load input point a, and the center of gravity of the rear end surface portion 127 is set as a constraint point (constraint point) B by coupling the rigid body element to the front end surface portion 125. The axis in the vehicle body front-rear direction (X direction in fig. 2) passing through the load input point a is referred to as the FR axis, and the axis in the vehicle body left-right direction (Y direction in fig. 4) is referred to as the RL axis.

(optimization analysis model Generation part)

The optimal analysis model generation unit 15 densely sets all joint candidate points, which are candidates for joints to be optimal for the optimal arrangement of joining the component groups, for the analysis object model to generate an optimal analysis model.

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

As shown in fig. 3, in the floor section model 111, the initial joining points 131 are set in advance at predetermined intervals P in the component group formed by joining a plurality of components.

As shown in fig. 5, the optimal analysis model generation unit 15 densely sets additional joints 153 at a predetermined interval P (< P) between the initial joints 131 on each component group. Then, both the initial bonding point 131 and the additional bonding point 153 set in advance in the bottom plate portion model 111 are set as bonding candidate points 155, and an optimal analysis model 151 is generated.

In addition, as a step of setting the bonding candidate points by optimizing the analysis model generation unit 15, it is sufficient to set the additional bonding points according to the size of the parts to be bonded as the component group in the analysis object model, for example, by actually increasing the interval of the additional bonding points so that the current split and the like do not occur at the time of bonding between adjacent bonding points.

The additional joint may be modeled by a beam element or a three-dimensional element, as in the initial joint described above.

In the following, in embodiment 1, as shown in fig. 5, an optimization analysis model 151 generated by setting an additional joint 153 in a floor section model 111 will be described.

(variable load condition setting section)

The variable load condition setting unit 17 sets a variable load condition for dividing the variable load applied to the optimal analysis model into a plurality of different vibration modes, and sets the variable load condition for each vibration mode as a variable load condition of 1 sequence (sequence) by combining the load conditions for each vibration mode by a predetermined number of cycles.

The variable load is a variable load that is obtained by dividing one or more of the magnitude, position, and direction of the load input to the analysis object model into different vibration modes, and combining the vibration modes by a predetermined number of cycles, and simulates a temporal variation input to the vehicle body during actual running of the vehicle. The variable load condition is given in the calculation of fatigue life of the initial joint and the joint candidate point, which will be described later.

The variable load condition setting unit 17 may set a variable load condition in which the variable load is divided into a plurality of different vibration modes and the variable load conditions are combined with each other, and a constraint condition in which the analysis object model of each variable load condition is constrained.

In embodiment 1, the variable load condition is set to a load input point a of the floor section model 111, and a load condition of a first vibration mode in which a load (moment) is twisted around the FR axis as shown in fig. 2 and a load condition of a second vibration mode in which a load (moment) is twisted around the RL axis as shown in fig. 4 are input.

As for the variable load conditions, as shown in fig. 6, the load conditions of the first vibration mode for 1 cycle and the load conditions of the second vibration mode for 20 cycles are combined to be 1 series of variable load conditions. Here, the graph shown in fig. 6 is a graph schematically showing the number of cycles of each of the load conditions of the first vibration mode and the load conditions of the second vibration mode under the 1-series fluctuation load conditions, and the magnitude of each load of the load conditions of the first vibration mode and the load conditions of the second vibration mode is an alternating fluctuation load having an amplitude (amplitude).

In addition, regarding the fluctuating load conditions shown as an example in fig. 6, the amplitudes of the loads corresponding to the load conditions of the first vibration mode and the load conditions of the second vibration mode are 0.7kn·m and 1.4kN, respectively.

In embodiment 1, as shown in fig. 2 and 4, the constraint point B of the floor section model 111 is set to be completely constrained (complete restraint) in the constraint condition.

(target fatigue life setting unit)

The target fatigue life setting unit 19 sets the target fatigue life of the optimal analysis model based on the number of times the load conditions are varied.

As the target fatigue life of the optimized analysis model, a separate stress analysis may be performed by applying the load condition of the vibration mode under the varying load condition set by the varying load condition setting unit 17 to the analysis target model, and the number of sequences up to fracture (fatigue failure) under the varying load condition of the initial joint of the analysis target model may be calculated as the fatigue life by using the result of the stress analysis, and the target fatigue life may be set based on the calculated fatigue life of the initial joint. Alternatively, the predetermined number of sequences may be set as the target fatigue life of the optimal analysis model according to a conventional rule of thumb.

In general, since the load input to the actual automobile body is not fixed in time, it can be considered that stress states of various amplitudes of stress are randomly generated also at the initial junction. In order to evaluate the fatigue life of the initial joint under such a stress state, the cumulative fatigue damage rule (linear cumulative damage rule (linear cumulative damage rule)) is used.

In the cumulative fatigue damage rule, first, the state in which stresses of various amplitudes are randomly generated is regarded as a state in which stresses of different amplitudes such as σ1, σ2, σ … … σm are repeated individually. Next, the number of repetitions (number of fracture repetitions) N1, N2, N3, … … Nm up to the fracture (fatigue failure) at each stress amplitude was read from the S-N diagram shown in fig. 7, with each stress amplitude (stress amplitude) σ1, σ2, σ3, … … σm being generated separately. The degree of damage (damage defect) when these stress amplitudes were repeated N1, N2, N3 … … Nm times was regarded as N1/N1, N2/N2, N3/N3 … … Nm/Nm, respectively.

In the cumulative fatigue damage rule, as shown in the formula (1), the cumulative damage dm is obtained as the sum of the damage degrees at the respective stress amplitudes. Then, when the cumulative damage degree dm is not less than 1, fatigue failure occurs. In addition, under a fluctuating load condition that receives an irregular repeated fluctuating load, the stress amplitudes σ1, σ2, σ3, … … σm and the repetition times n1, n2, n3 … … nm may be determined by using a rain flow count method (Rainflow Counting method).

[ mathematics 1]

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

First, the stress acting on each initial joint obtained by performing stress analysis on each of the load conditions of each vibration mode in the fluctuating load conditions is set to be different stress amplitudes σ1, σ2, σ … … σm generated at the initial joint under the fluctuating load conditions.

Next, the target fatigue life setting unit 19 obtains the number of repetitions (number of repetitions of breaking) N1, N2, N3, … … Nm from the initial junction 131 when each stress amplitude is generated separately at the initial junction 131, based on the S-N diagram (fig. 7).

Next, the number of repetitions until fracture (fracture repetition number) N1, N2, N3, … … Nm at each stress amplitude and the number of cycles N1, N2, N3, … … Nm of the load condition of each vibration mode in 1 sequence of the variable load condition are substituted into the equation (1), and the cumulative damage dm in 1 sequence is calculated. Further, the cumulative damage DM when the 1 sequence of the variable load condition is continuously repeated K times (K sequences) is calculated according to the formula (2).

[ math figure 2]

Then, the number of sequences K when the cumulative damage DM becomes 1 or more is calculated as the fatigue life of the initial joint under the fluctuating load condition.

The target fatigue life setting unit 19 sets a target fatigue life based on the thus calculated fatigue life of each of the initial joints 131. The target fatigue life is the fatigue life that should be satisfied by a joint candidate point (described later) that is retained by the optimal analysis. In embodiment 1, the target fatigue life is set to be at least a long fatigue life equal to or longer than the shortest fatigue life (minimum fatigue life)) in each initial joint calculated by the target fatigue life setting unit 19.

Fig. 8 shows an example of the position of the initial joint at the shortest lower 3 point and the result of the fatigue life of the initial joint 131 obtained by using the result of the stress analysis obtained by applying the variable load condition and the constraint condition shown in fig. 6 to the floor part model 111.

The fatigue life of the initial joint 131 shown in fig. 8 is calculated under varying load conditions in which a torque of 0.7kn·m around the FR axis as the load condition of the first vibration mode (fig. 2) is combined in an alternating manner with a torque of 1.4kn·m around the RL axis as the load condition of the second vibration mode (fig. 4) in an alternating manner with a torque of 20 cycles to set 1 sequence. A specific procedure for calculating the target fatigue life of the initial joint 131 will be described in example 1 described later.

As shown in fig. 8, regarding the fatigue life obtained for each initial joint 131 of the floor section model 111, the fatigue life of the initial joint 131 at the portion C where the floor panel model 113 and the mount inside model 117 are joined is the shortest, 18800 series, the fatigue life of the initial joint 131 at the portion D where the floor panel model 113 and the rear floor cross member model 123 are joined is the 22900 series, and the fatigue life of the initial joint 131 at the portion E where the channel model 115 and the rear floor cross member model 123 are joined is the 24900 series. Based on the result, the target fatigue life setting unit 19 sets a long fatigue life equal to or longer than the fatigue life of the initial joint 131 at the portion C as the target fatigue life.

When calculating the fatigue life of the initial joint by the target fatigue life setting unit 19, as in the spot welding unit 141 illustrated in fig. 9, the portion (the center portion 147 and the peripheral portion 149) to which the Liang Yaosu 145 of the component model 143 is joined may be set based on the nugget diameter (nugget diameter) of the actual spot welding point, and the stress value of the planar element in the peripheral portion 149 may be used by re-cutting the planar element into a spider web shape.

Further, in the calculation of the fatigue life based on the target fatigue life setting unit 19, commercially available fatigue life prediction analysis software may be used. For example, in the case where the fatigue life of the initial joint modeled by the beam element is calculated using commercially available fatigue life prediction analysis software, the fatigue life of the initial joint can be calculated by inputting conditions such as stress of the initial joint into the fatigue life prediction analysis software. As the stress of the initial joint, a stress value of a planar element of each component model to which the beam element is coupled, or a nominal structural stress (nominal structure stress) obtained from a force and a moment acting on both ends of the beam element can be used.

The S-N diagram may also vary depending on the load state of the load, for example, even if the load is the same stress amplitude, whether the average stress is compressive stress (compressive stress) or tensile stress (tensile stress), or the like, but the value or experimental value of the fatigue life prediction analysis software may be referred to. Alternatively, where nominal structural stress is used to calculate fatigue life, one S-N plot containing different load conditions may also be used. Further, as shown in fig. 7, the S-N diagram may be expressed by various rules such as the micin ' S rule (min ' S rule) that does not determine fracture when the stress is less than or equal to the fatigue limit (fatigue limit), and the modified min ' S rule (damage) that counts as damage (damage) even when the stress is less than or equal to the fatigue limit.

(optimizing analysis Condition setting part)

The optimal analysis condition setting unit 21 obtains the number of fracture repetitions of each joint candidate point for each of the load conditions of each vibration mode set by the variable load condition setting unit 17, obtains the ratio of the number of cycles to the number of fracture repetitions of the load condition of each vibration mode, and sets the sum of the number of sequences of the variable load conditions set by the target fatigue life setting unit 19 as the cumulative damage degree DM of each joint candidate point, and sets the conditions related to the cumulative damage degree of the joint candidate point retained by the optimal analysis, the conditions related to the rigidity of the optimal analysis model, and the conditions related to the number of points of the joint candidate point retained by the optimal analysis as the objective function or constraint condition as the optimal analysis conditions.

The optimized analysis conditions include an objective function and a constraint condition. The objective function is set to only one according to the purpose of the optimization analysis. In embodiment 1, a condition related to the rigidity of the optimal analysis model is set as an objective function.

As the condition relating to rigidity, for example, a predetermined position in the analysis object model may be defined as a rigidity evaluation point, and a displacement (displacement) or strain (strain) of the rigidity evaluation point may be defined as an index. In the fluctuating load conditions, for example, the minimization of the value obtained by adding the displacements of the rigidity evaluation points P under the load conditions of the respective vibration modes or the minimization of the displacements of the rigidity evaluation points P under the load conditions of the respective vibration modes may be set as the condition related to rigidity.

The constraint conditions are constraints imposed on the basis of performing the optimization analysis, and a plurality of constraint conditions are set as needed.

In embodiment 1, a condition that the fatigue life of the joint candidate point is longer than the target fatigue life set by the target fatigue life setting unit 19 may be set as a constraint condition. The number of fracture repetitions of the joint candidate point can be calculated using the S-N line diagram shown in fig. 7, as in the case of the number of fracture repetitions of the initial joint point under the fluctuating load condition.

The conditions relating to the fatigue life are not limited to the constraint conditions in which the target fatigue life set by the target fatigue life setting unit 19 is directly applied, and the constraint conditions in which the cumulative damage degree DM of the number of sequences of the joining candidate points under the fluctuating load condition set as the target fatigue life by the target fatigue life setting unit 19 does not cause fatigue failure is set to < 1 may be applied.

Here, the cumulative damage degree DM of the joining candidate point may be calculated using, for example, the stress of the planar element of the component model to which the beam element modeled as the joining candidate point is joined, the nominal structural stress calculated from the force and moment acting on both ends of the beam element, or the like, using the S-N line diagram shown in fig. 7 and the equation (2) similarly to the cumulative damage degree DM of the initial joining point described above.

Further, regarding the condition concerning the number of points of the joint candidate points, the number of points of the joint candidate points to be held can be set to a given value. In embodiment 1, a constraint condition is set that the number of reserved join candidate points is the same as the number of initial join points.

In addition, regarding the optimization analysis condition regarding the number of points of the joint candidate points, for example, when the density method is applied to the topology optimization in the optimization analysis by the optimization analysis unit 23 described later, the volume (volume) of the joint candidate points calculated based on the density (density) of the elements (beam elements, solid elements, etc.) modeled as the joint candidate points may be given as the constraint condition.

(optimization analysis unit)

The optimizing and analyzing unit 23 applies the fluctuating load condition set by the fluctuating load condition setting unit 17 to an optimizing and analyzing model, and performs optimizing and analyzing under the optimizing and analyzing condition, thereby obtaining, as the optimal arrangement of the joint, the arrangement of the joint candidate points achieved with the aim of any one of reduction in the cumulative damage degree of the joint candidate points, improvement in the rigidity of the optimizing and analyzing model, and minimization of the number of points of the joint candidate points that remain.

As the optimization analysis by the optimization analysis unit 23, topology optimization can be applied. When the density method is used for topology optimization, a normalized (normalized) virtual density having a value of 0 to 1 is given as a design variable (design variable) to elements (beam elements, solid elements, etc.) modeled as joint candidate points, and a value of the density satisfying the optimization analysis condition is calculated.

If the calculated density has a value of 1, the joining candidate point is completely present, if the calculated density has a value of 0, the joining candidate point is absent, and if the calculated density has an intermediate value, the joining of the component group based on the joining candidate point is intermediate.

Therefore, when the intermediate density of the density method is large in the topology optimization, it is preferable to use the penalty coefficient to perform discretization as shown in the equation (3). In addition, K _M Is to the elementsThe rigid matrix (stiffness matrix) to which a penalty (penalty) is applied, K is the rigid matrix of elements, ρ is the normalized (normalized) density, and p is the penalty coefficient.

[ math 3]

K _M (ρ)＝p ^p K……(3)

Wherein, the liquid crystal display device comprises a liquid crystal display device,

K _M rigid matrix that imposes a penalty on the rigid matrix of elements

K rigid matrix of elements

Density normalized by ρ

p penalty coefficient

Although the penalty coefficient frequently used in discretization is 2 or more, in the optimization analysis of the joint position according to the present invention, the penalty coefficient is preferably 4 or more. Further, it is more preferable that the penalty coefficient is 4 or more in the planar element and the stereoscopic element, and 20 or more in the beam element.

The optimization analysis unit 23 may perform the optimization analysis based on the topology optimization as described above, or may perform the optimization analysis based on another calculation method.

Fig. 10 shows an example of the optimal arrangement of the joints 157 obtained by the optimization analysis unit 23 performing the optimization analysis by applying the density method to the topology optimization. The operational effect of the optimal arrangement of the joint points obtained in embodiment 1 will be described in example 1 described later.

< method for optimizing and analyzing the joining position of vehicle body >

In the method for optimizing and analyzing the joint position of the vehicle body according to embodiment 1 of the present invention (hereinafter, simply referred to as "optimizing and analyzing method"), the following steps are executed by a computer for all or a part of the vehicle body model having a plurality of component models composed of beam elements, plane elements, and/or three-dimensional elements and having an initial joint for joining the plurality of component models as a component group, and optimizing and analyzing the optimal arrangement of the joint for the purpose of any one of the improvement in rigidity of the vehicle body model, the improvement in fatigue life of the joint for joining the component groups in the vehicle body model, and the minimization of the number of points of the joint are obtained, and as shown in fig. 11, the method includes an analysis object model setting step S1, an optimizing and analyzing generating step S3, a variable load condition setting step S5, a target fatigue life setting step S7, an optimizing and analyzing condition setting step S9, and an optimizing and analyzing step S11. These steps will be described below. The following steps are performed by the optimization analysis device 1 (fig. 1) configured by a computer.

Analytical object model setting step

In the analysis object model setting step S1, all or a part of the vehicle body model is set as the analysis object model.

In embodiment 1, in the analysis object model setting step S1, the analysis object model setting unit 13 sets the floor part model 111, which is a part of the vehicle body model, as the analysis object model.

Step of generating an optimized analytical model

In the optimal analysis model generation step S3, all joint candidate points that are candidates for joints to be optimally arranged are densely set for the analysis object model, and an optimal analysis model is generated.

In embodiment 1, in the optimal analysis model generation step S3, the optimal analysis model generation unit 15 generates additional junctions 153 densely between the initial junctions 131 set in advance in the floor section model 111 at a predetermined interval p (p < P, P: interval between the initial junctions) at which the actual additional junctions 153 can be increased, such as a current split at the time of joining between adjacent junctions, and sets both the initial junctions 131 and the additional junctions 153 as joining candidate points 155.

Step of setting variable load conditions

In the variable load condition setting step S5, load conditions are set in which the variable load applied to the optimal analysis model is divided into a plurality of different vibration modes, and the load conditions in the respective vibration modes are combined by a predetermined number of cycles to set 1 series of variable load conditions.

In embodiment 1, in the variable load condition setting step S5, the variable load condition setting unit 17 of the optimal analysis device 1 sets a variable load condition (see fig. 6) in which 1 cycle of the load condition of the first vibration mode shown in fig. 2 and 20 cycles of the load condition of the second vibration mode shown in fig. 4 are combined to set 1 sequence, and further sets constraint conditions for constraining the constraint point B as shown in fig. 2 and 4.

Target fatigue Life setting step

In the target fatigue life setting step S7, the target fatigue life of the optimal analysis model is set based on the number of times the variable load condition is set in the variable load condition setting step S5. As the target fatigue life of the optimization analysis model, the analysis object model may be subjected to stress analysis separately by applying the load condition of the vibration mode among the fluctuation load conditions set in the fluctuation load condition setting step S5, and the sequence number of fluctuation load conditions of the fatigue life of the initial joint serving as the analysis object model under the fluctuation load condition may be calculated by using the result of the stress analysis, and the sequence number of fluctuation load conditions serving as the target fatigue life may be set based on the calculated sequence number of fluctuation load conditions serving as the fatigue life of the initial joint, or the sequence number of fluctuation load conditions may be set to the target fatigue life according to a conventional rule of thumb.

Here, the target fatigue life is a fatigue life to be satisfied by the joint candidate point to be optimized, and at least the number of sequences of the long variable load conditions equal to or greater than the number of sequences of the variable load conditions that are the shortest fatigue life (shortest fatigue life) of each initial joint calculated in the target fatigue life setting step S7 is set as the target fatigue life.

Optimizing analysis Condition setting step

In the optimization analysis condition setting step S9, in order to perform the optimization analysis with the optimization analysis model as the optimization target, the number of fracture repetitions of each joint candidate point is obtained for each of the load conditions of the plurality of different vibration modes in which the variable load is divided in the variable load condition setting step S5, the sum of the number of cycles of the load condition of each vibration mode and the number of the fracture repetitions is obtained, and the number of sequences of the variable load condition set in the target fatigue life setting step S7 is set as the cumulative damage degree DM of each joint candidate point, and the condition related to the cumulative damage degree of the joint candidate point retained in the optimization analysis, the condition related to the rigidity of the optimization analysis model, and the condition related to the number of the joint candidate points retained in the optimization analysis are set as the objective function or the constraint condition as the optimization analysis condition.

In embodiment 1, in the optimal analysis condition setting step S9, the optimal analysis condition setting unit 21 sets a constraint condition that the maximum rigidity of the optimal analysis model (the minimum displacement of the rigidity evaluation point P) is an objective function, and a constraint condition that the fatigue life of the joint candidate point 155 is longer than the target fatigue life, and a constraint condition that the number of points of the joint candidate point to be held is the same as the number of points of the initial joint point, as the optimal analysis condition.

As the condition relating to rigidity, for example, a predetermined position in the analysis object model may be set as a rigidity evaluation point, and displacement or strain of the rigidity evaluation point may be used as an index. In the variable load condition, for example, the variable load may be divided into vibration modes, and the minimization of the value obtained by adding the displacements of the rigidity evaluation points P under the load condition of each vibration mode or the minimization of the displacement of the rigidity evaluation points P under the variable load condition may be a condition related to rigidity.

The conditions relating to the fatigue life are not limited to the constraint conditions in which the target fatigue life set in the target fatigue life setting step S7 is directly given, and for example, constraint conditions in which the cumulative damage degree DM of the joint candidate point is equal to or less than the cumulative damage degree corresponding to the target fatigue life may be given.

Optimizing analysis step

In the optimizing and analyzing step S11, the varying load condition set in the varying load condition setting step S5 is given to the optimizing and analyzing model, and optimizing and analyzing is performed under the optimizing and analyzing condition, and the arrangement of the joint candidate points, which is achieved with the aim of any one of the reduction of the cumulative damage degree of the joint candidate points, the improvement of the rigidity of the optimizing and analyzing model, and the minimization of the number of the remaining joint candidate points, is obtained as the optimal arrangement of the joint points.

In embodiment 1, in the optimization analysis step S11, the optimization analysis unit 23 performs optimization analysis on the joint candidate points set in the floor section model 111 as the target of optimization, and obtains the arrangement of the joint candidate points 155 satisfying the optimization analysis condition as the optimal arrangement of the joints 157, as shown in fig. 10.

< procedure for optimizing and analyzing the position of joining the vehicle body)

In embodiment 1 of the present invention, an optimal analysis program for the joint position of the vehicle body can be configured to function each part of the optimal analysis device 1 for the joint position of the vehicle body, which is configured by a computer. That is, in the optimization analysis program for the joint position of the vehicle body according to embodiment 1 of the present invention, all or a part of the vehicle body model is set as the analysis target model, and the analysis target model is obtained to perform the optimization analysis of the optimal arrangement of the joint, which is achieved for any of the purposes of improving the rigidity of the vehicle body model, improving the fatigue life of the joint for joining the component groups in the vehicle body model, and minimizing the number of points of the joint, and the optimization analysis program has functions that the computer performs as the analysis target model setting unit 13, the optimization analysis model generating unit 15, the variable load condition setting unit 17, the target fatigue life setting unit 19, the optimization analysis condition setting unit 21, and the optimization analysis unit 23 as shown as an example in fig. 1.

As described above, according to the method, apparatus, and program for optimizing and analyzing the joining position of the vehicle body according to embodiment 1, all or a part of the vehicle body model is set as the analysis target model, the optimization analysis model in which the joining candidate points for joining the component groups are set for the analysis target model is generated, the optimization analysis conditions (objective function or constraint condition) concerning the number of retained joining candidate points to be optimized, the fatigue life, and the rigidity of the optimization analysis model are set, and the optimization analysis for the joining candidate points is performed, whereby when the fluctuation load such as the amplitude, the direction, and the like, which fluctuates in time, is input to the vehicle body, the optimal arrangement of the joining points can be obtained with the aim of any one of minimizing the number of joining candidate points, improving the rigidity of the analysis target model, and improving the fatigue life of the joining point for joining the component groups.

Embodiment 2

In embodiment 1 of the present invention described above, topology optimization by a density method is applied to optimization analysis, and joint candidate points satisfying the optimization analysis conditions are obtained. Regarding whether the joint candidate points are retained or vanished in the topology optimization, it is determined based on the value of the density of the joint candidate points.

As described above, the density in the topology optimization based on the density method is a normalized virtual density having a value of 0 to 1, and if the value of the density is 1, it means a state in which the bonding candidate point is completely retained, if it is 0, it means a state in which the bonding candidate point is disappeared, and if it is an intermediate value between 0 and 1, it means an intermediate state in which the bonding candidate point is retained and disappeared.

Therefore, as described above, when the intermediate density of the density method is large in topology optimization, it is preferable to use the penalty coefficient for discretization as shown in the formula (1).

When discretization is performed by adding a penalty coefficient to topology optimization, the arrangement of joint candidate points of a given number of points reserved by optimization analysis is set as the target performance of fatigue life and rigidity of the analysis object model of the optimal arrangement of joint points.

However, when discretization is performed without adding a penalty coefficient to the topology optimization, joint candidate points of intermediate density remain in the optimized analysis model after the optimized analysis. In order to obtain the optimal arrangement of the bonding points at a given number of points based on the result of the optimization analysis, for example, the arrangement of bonding candidate points having a density equal to or higher than a certain threshold value is selected as the optimal arrangement of the bonding points, and the arrangement of bonding candidate points having a value lower than the intermediate density of the threshold value is not selected as the optimal arrangement of the bonding points.

If the optimal arrangement of the joints thus obtained is reset in the analysis object model and the fatigue life of the analysis object model is calculated, there may be a problem that stress concentrates on a specific joint and is lower than the target fatigue life, or the rigidity of the analysis object model is lowered, and the fatigue life and/or rigidity do not satisfy a given performance.

Accordingly, intensive studies have been conducted to solve the above problems, and as a result, it has been found that: if it is determined that the fatigue life and rigidity of the analysis object model in which the arrangement of the selected joint candidate points is set instead of the initial joint point satisfy the predetermined performance, the optimal arrangement of the joint points satisfying the predetermined performance with respect to rigidity and fatigue life can be obtained by changing the optimal analysis condition (for example, the threshold value of density) and performing the optimal analysis again.

The method, apparatus and program for optimizing and analyzing the joint position of the vehicle body according to embodiment 2 are completed based on the above findings, and a specific configuration thereof will be described. The same components as those of the method, apparatus, and program for optimizing and analyzing the joint position of the vehicle body according to embodiment 2 are not described repeatedly.

< device for optimizing and analyzing the joint position of a vehicle body >

The configuration of an optimizing and analyzing device for a joint position of a vehicle body according to embodiment 2 of the present invention will be described below.

The optimization analysis device 31 is a device for performing an optimization analysis of an optimal arrangement of joints, which is achieved for the purpose of any one of an improvement in rigidity of a vehicle body model, an improvement in fatigue life of a joint joining a component group in the vehicle body model, and a minimization of the number of points of the joints, with respect to all or a part of an automobile body model having a plurality of component models composed of beam elements, plane elements, and/or three-dimensional elements and having an initial joint joining a plurality of the component models as a component group, and is composed of a PC (personal computer) or the like, and is provided with a display device 3, an input device 5, a storage device 7, a data memory 9 for work, and an arithmetic processing unit 33, as shown in fig. 12. The display device 3, the input device 5, the storage device 7, and the work data memory 9 are connected to the arithmetic processing unit 33, and execute the respective functions according to instructions from the arithmetic processing unit 33.

Arithmetic processing unit

As shown in fig. 12, the arithmetic processing unit 33 includes an analysis object model setting unit 13, an optimal analysis model generating unit 15, a variable load condition setting unit 17, a target fatigue life setting unit 19, an optimal analysis condition setting unit 21, and an optimal analysis unit 34, and further includes a selected joint candidate point setting analysis object model generating unit 35, a selected joint candidate point performance calculating unit 37, a determining unit 39, and an optimal joint determining unit 41, and is configured by a CPU (central processing unit) such as a PC. These sections function by executing a given program by the CPU.

Since the analysis object model setting unit 13, the optimal analysis model generating unit 15, the variable load condition setting unit 17, the target fatigue life setting unit 19, and the optimal analysis condition setting unit 21 in the arithmetic processing unit 33 have the same functions as those of the present embodiment 1 described above, the functions of the optimal analysis unit 34, the selected joining candidate point setting analysis object model generating unit 35, the selected joining candidate point performance calculating unit 37, the determining unit 39, and the optimal joining point determining unit 41 will be described below.

(optimization analysis unit)

The optimizing analysis unit 34 applies the fluctuating load condition set by the fluctuating load condition setting unit 17 to the optimizing analysis model, performs optimizing analysis under the optimizing analysis condition, and reserves, as the temporary optimal arrangement of the joint, the arrangement of the joint candidate points achieved with the aim of any one of reduction in the cumulative damage degree of the joint candidate points, improvement in the rigidity of the optimizing analysis model, and minimization of the number of points of the reserved joint candidate points.

As the optimization analysis by the optimization analysis unit 34, topology optimization can be applied in the same manner as the optimization analysis unit 23 of embodiment 1 described above.

(selected join candidate Point setting analysis object model Generation part)

The selected joint candidate point setting analysis object model generation unit 35 selects a joint candidate point of a given number from among the joint candidate points held as a temporary optimal arrangement by the optimization analysis unit 34, sets the selected joint candidate point in the analysis object model instead of the initial joint, and generates a selected joint candidate point setting analysis object model.

In the topology optimization by the density method, since the density of the element (for example, liang Yaosu) modeled as the joint candidate point is calculated, the joint candidate point setting analysis object model generating unit 35 may select a predetermined point number from among the joint candidate points whose density is equal to or higher than a predetermined threshold value, for example, and set the point number in the analysis object model.

(selected Joint candidate Performance calculation section)

The selected joint candidate performance calculation unit 37 performs stress analysis by giving the load condition and the constraint condition of each vibration mode in the fluctuating load condition set by the fluctuating load condition setting unit 17 to the model to be analyzed for the selected joint candidate setting, and calculates the fatigue life of the selected joint candidate under the fluctuating load condition and the rigidity of the model to be analyzed for the selected joint candidate using the result of the stress analysis.

The fatigue life of the joint candidate point set in the joint candidate point setting analysis object model under the fluctuating load condition may be calculated based on the cumulative fatigue damage rule by using the stress of the joint candidate point obtained by the stress analysis of the joint candidate point setting analysis object model in the same manner as the target fatigue life setting unit 19 described above, and the cumulative damage degree DM (see formula (2)) may be obtained by commercially available fatigue life prediction analysis software.

As the stress of the joint candidate point used for calculation of the cumulative damage DM, for example, the stress of a planar element of a component model to which the beam element modeled as the joint candidate point is coupled, the nominal structural stress calculated from the forces and moments acting on both ends of the beam element, and the like can be used.

Further, the rigidity of the model to be analyzed for setting the joint candidate point may be selected, for example, by using a predetermined position as a rigidity evaluation point, using a displacement or strain thereof as an index, dividing the displacement of the rigidity evaluation point under a fluctuating load condition and the fluctuating load into vibration modes, and adding the displacements of the rigidity evaluation points under the load conditions of the vibration modes to each other to obtain a value as an index.

(determination section)

The determination unit 39 determines whether or not the fatigue life of the joint candidate point in the joint candidate point setting analysis object model under the fluctuating load condition and the rigidity of the joint candidate point setting analysis object model satisfy a given performance exceeding the analysis object model for which the initial joint is set.

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

(optimal junction determination section)

When the determination unit 39 determines that the predetermined performance is satisfied, the optimal joint determination unit 41 determines the arrangement of the joint candidate points selected by the joint candidate point setting analysis object model generation unit 35 as the optimal arrangement of the joint points, and when the determination unit 39 determines that the predetermined performance is not satisfied, the optimal joint determination unit changes the condition regarding the cumulative damage degree of the joint candidate points reserved by the optimization analysis, the condition regarding the rigidity of the optimization analysis model, or the condition regarding the number of the joint candidate points reserved by the optimization analysis, which are set by the optimization analysis condition setting unit 21, until the predetermined performance is satisfied, and repeatedly performs the processing of the optimization analysis unit 34, the joint candidate point setting analysis object model generation unit 35, the joint candidate point selection performance calculation unit 37, and the determination unit 39 until the predetermined performance is satisfied.

When the determination unit 39 does not determine that the rigidity and fatigue life satisfy the predetermined performance, the optimal joint determination unit 41 may change the optimal analysis conditions such as the threshold value for selecting the joint candidate points, for example, by the optimal analysis condition setting unit 21 so as to increase the number of the joint candidate points remaining in the optimal analysis.

In addition, when changing the conditions related to the cumulative damage degree of the joint candidate points, the conditions related to the rigidity of the optimal analysis model, or the conditions related to the number of points of the joint candidate points to be held in the optimal analysis condition setting unit 21, any one of the conditions may be changed, or two or three of the conditions may be changed at the same time.

< method for optimizing and analyzing the joining position of vehicle body >

In the method for optimizing and analyzing the joint position of the vehicle body according to embodiment 2 of the present invention, the following steps are executed by a computer for all or a part of the vehicle body model having a plurality of component models including the beam element, the planar element, and/or the three-dimensional element and having the initial joint where the plurality of component models are joined as the component group, and the optimal analysis for the optimal arrangement of the joint, which is achieved for any of the purposes of improving the rigidity of the vehicle body model, improving the fatigue life of the joint where the component group is joined, and minimizing the number of points of the joint, is performed, as shown in fig. 13, including an analysis object model setting step S1, an optimal analysis model generating step S3, a fluctuating load condition setting step S5, a target fatigue life setting step S7, an optimal analysis condition setting step S9, an optimal analysis step S12, a joint candidate point setting analysis object model generating step S13, a joint candidate performance calculating step S15, a determining step S17, and an optimal joint determining step S19 are performed.

Since the analysis object model setting step S1, the optimal analysis model generating step S3, the variable load condition setting step S5, the target fatigue life setting step S7, and the optimal analysis condition setting step S9 in the above-described steps are the same as in the present embodiment 1, the optimization analysis step S12, the selected joining candidate point setting analysis object model generating step S13, the selected joining candidate point performance calculating step S15, the determining step S17, and the optimal joining point determining step S19 will be described below. The steps of the optimization analysis method according to embodiment 2 are performed by an optimization analysis device 31 (fig. 12), and the optimization analysis device 31 is configured by a computer.

Optimizing analysis step

In the optimizing and analyzing step S12, the varying load condition set in the varying load condition setting step S5 is given to the optimizing and analyzing model, and optimizing and analyzing is performed under the optimizing and analyzing condition, and the arrangement of the joint candidate points, which is achieved with the aim of any one of the reduction of the cumulative damage degree of the joint candidate points, the improvement of the rigidity of the optimizing and analyzing model, and the minimization of the number of the reserved joint candidate points, is reserved as the temporary optimal arrangement of the joint points.

In embodiment 2, in the optimization analysis step S12, the optimization analysis unit 34 performs the optimization analysis with the joint candidate points set in the floor section model 111 as the target of the optimization, and as shown in fig. 10, the arrangement of the joint candidate points 155 satisfying the optimization analysis condition is kept as the temporary optimal arrangement of the joints 157.

Step of generating model to be analyzed for setting selected candidate points

In the selected joint candidate point setting analysis object model generating step S13, a joint candidate point of a given number is selected from the joint candidate points held as a temporary optimal arrangement by the optimization analysis in the optimization analysis step S12, the selected joint candidate point is set in the analysis object model instead of the initial joint, and the selected joint candidate point setting analysis object model is generated. In embodiment 2, the selected bonding candidate point setting analysis object model generating unit 35 performs the selected bonding candidate point setting analysis object model generating step S13.

Calculation step of Performance of selected candidate Joint

In the selected joint candidate performance calculation step S15, stress analysis is performed by giving the load condition and the constraint condition of each vibration mode in the fluctuating load condition set in the fluctuating load condition setting step S5 to the model to be analyzed for the selected joint candidate setting, and the fatigue life of the selected joint candidate under the fluctuating load condition and the rigidity of the model to be analyzed for the selected joint candidate setting are calculated using the result of the stress analysis. In embodiment 2, the selected-bonding-candidate-point performance calculating section 37 performs the selected-bonding-candidate-point performance calculating step S15.

Determination step

In the determination step S17, it is determined whether or not the fatigue life of the joint candidate point in the joint candidate point setting analysis object model under the fluctuating load condition and the rigidity of the joint candidate point setting analysis object model satisfy the given performance of the analysis object model exceeding the initial joint point setting. In embodiment 2, the determination unit 39 performs the determination step S17.

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

Optimal junction determination step

In the optimal joint determination step S19, when it is determined in the determination step S17 that the predetermined performance is satisfied, the arrangement of the joint candidate points selected in the joint candidate point setting analysis object model generation step S13 is determined as the optimal arrangement of the joint, and when it is determined in the determination step S17 that the predetermined performance is not satisfied, the conditions relating to the cumulative damage degree of the joint candidate points held by the optimization analysis, the conditions relating to the rigidity of the optimization analysis model, or the conditions relating to the number of the joint candidate points held by the optimization analysis set in the optimization analysis condition setting step S9 are changed, and the optimal arrangement of the joint is determined by repeating the optimization analysis step S12, the joint candidate point setting analysis object model generation step S13, the joint candidate point performance calculation step S15, and the determination step S17 until the predetermined performance is satisfied. In the determination step S17, the given performance may not be satisfied because there are a large number of joint candidate points of intermediate density, and the performance obtained by integrating them is determined. In embodiment 2, the optimal joint determination step S19 is performed by the optimal joint determination unit 41.

In addition, in the optimal analysis condition setting step S9, when changing the conditions related to the cumulative damage degree of the joint candidate points, the conditions related to the rigidity of the optimal analysis model, or the conditions related to the number of points of the joint candidate points to be held, any one of the conditions may be changed, or two or three of the conditions may be changed at the same time.

< procedure for optimizing and analyzing the position of joining the vehicle body >

In embodiment 2 of the present invention, an optimal analysis program for the joint position of the vehicle body can be configured to function each part of the optimal analysis device 31 for the joint position of the vehicle body, which is configured by a computer. That is, in the optimization analysis program for the joining position of the vehicle body according to embodiment 2 of the present invention, the optimization analysis program includes a function of causing a computer to execute, as shown by way of example in fig. 12, an analysis object model setting unit 13, an optimization analysis model generating unit 15, a fluctuation load condition setting unit 17, a target fatigue life setting unit 19, an optimization analysis condition setting unit 21, and an optimization analysis unit 34, and further includes a joining candidate point setting object model generating unit 35, a joining candidate point performance calculating unit 37, a determination unit 39, and an optimization determination unit 41, each of which is configured to calculate the optimal arrangement of the joining point for the purpose of improving the rigidity of the vehicle body model, improving the fatigue life of the joining point for the joining of the component groups in the vehicle body model, and minimizing the number of points, with respect to all or part of the vehicle body model having a plurality of component models including the beam elements, the plane elements, and/or the three-dimensional elements.

As described above, in the method, apparatus, and program for optimizing and analyzing the joining position of the vehicle body according to embodiment 2, even when the discretization is not performed in the topology optimization by the density method, the optimal placement of the joining point can be appropriately determined with the aim of minimizing the number of joining candidate points, improving the rigidity of the analysis object model, and improving the fatigue life of the joining point at which the component group is joined, even when the load that fluctuates over time as in the case of actual vehicle running is input to the vehicle body.

In the above description, a vehicle body model in which the entire vehicle body is modeled is obtained, and a floor portion model that is a part of the vehicle body model is set as an analysis object model. Of course, the present invention may use the entire body model as the analysis target model, or may use a portion of the body model other than the floor portion model as the analysis target model. Further, a vehicle body part model that is a part of the vehicle body model may be acquired, and the acquired vehicle body part model may be used as the analysis target model.

In the above description, the case where the initial joining points 131 of 352 points are set in the floor section model 111 at 60mm intervals has been exemplified, but the intervals and the number of points of the initial joining points 131 are not limited to this.

The initial joint 131 is a joint for a case where the operator or another means sets in advance in the floor section model 111. Of course, in the present invention, the initial junction point may be newly set by the operator in the analysis object model setting unit or in the analysis object model setting step, or the initial junction point may be further added and set to the analysis object model to which the initial junction point has been set.

In addition, in embodiment 1, a case is assumed in which a fixed load (moment) such as torsion about the FR (front-rear) axis and about the RL axis is applied to the floor portion model 111, and the load conditions and the constraint conditions shown in fig. 2 and 4 are set, but the present invention may be configured so that a fluctuating load condition and a constraint condition are appropriately set by assuming a part of the vehicle body to be analyzed and a fluctuating load applied to the actual vehicle body.

In the examples of embodiment 1 and embodiment 2, 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 analysis object model.

Of course, in the present invention, it is sufficient to calculate the fatigue life of the joint candidate points 155 in the optimization analysis model in which the initial joint points 131 before the optimization analysis are densely set (fig. 5) and the additional joint points 153, determine the shortest fatigue life among the calculated 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). Ltoreq. (target fatigue life of joint candidate point). Ltoreq. (shortest fatigue life of joint candidate point of joint before optimization analysis is densely set).

Further, in the above description, the optimal analysis is performed with both the initial join point and the additional join point as joining candidate points, but it is also possible to obtain the optimal arrangement of the join points added to the initial join point by using only the additional join point as joining candidate points, and not using the initial join point as the object of the optimal analysis.

In the above description of the example, the optimal analysis condition is set in which the number of points of the joint candidate is the same as the number of points of the initial joint, but the optimal analysis condition may be set in which the number of points different from the initial joint is the number of points of the joint candidate.

Further, if the initial joint is set as a joint candidate point and the optimal analysis is performed, there are cases where the joint candidate point joined as the component group disappears in the optimal analysis, and the component group becomes scattered, and the optimal analysis cannot be performed. In this case, at least one fixed joint (fixed joining point) that is not the object of the optimization analysis may be set in each component group.

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

In the above description, the fatigue life of the joint candidate points or the rigidity of the optimal analysis model is set as the objective function, but the number of the joint candidate points may be set as the objective function, and the fatigue life and rigidity may be set as the constraint conditions.

Example 1

Since the effect of the present invention is confirmed, the description will be made. In the analysis, as shown in fig. 14, the floor portion model 111 that models the floor portion of the vehicle body is taken as an object, and the optimal arrangement of the joints at which the component models constituting the floor portion model 111 are joined as the component group is obtained by the optimization analysis.

As described in embodiment 1, the floor section model 111 is configured to have a floor panel model 113, a tunnel model 115, a mount inside model 117, a mount outside model 119, a front floor cross member model 121, and a rear floor cross member model 123 as component models. These component models are modeled by planar elements.

Further, the floor portion model 111 is preset with an initial joint 131 for joining the component models as a component group. The initial joining points 131 are modeled by beam elements joining the nodes of the planar elements of the component model, the number of the initial joining points is 352 points, and the interval P between the initial joining points 131 is 60mm.

In example 1, first, a target fatigue life is set based on the fatigue life of the initial joint 131 under the fluctuating load conditions shown in fig. 6.

The fluctuating load condition shown in fig. 6 sets a combination of 1 cycle of alternating input of a torque of 0.7kn·m about the FR axis as the load condition of the first vibration mode (fig. 2), followed by alternating input of a torque of 1.4kn·m about the RL axis as the load condition of the second vibration mode (fig. 4), as 1 sequence.

Next, stress analysis of the bottom plate portion model 111 was performed for each of the load conditions of the first vibration mode (fig. 2) and the load conditions of the second vibration mode (fig. 4), and the stress generated at the initial joint 131 under the load conditions of the respective vibration modes was obtained.

Next, the number of repetitions N1 and N2 of the different stress amplitudes σ1 and σ2 generated at the initial junction 131 under the fluctuating load condition until the initial junction 131 breaks when the initial junction 131 is generated alone was obtained from the S-N line diagram (fig. 7).

Then, the number of repetitions N1 and N2 until fracture at each stress amplitude and the number of cycles N1 (=1 cycle) and N2 (=20 cycles) of the load condition of the first vibration mode and the load condition of the second vibration mode under the varying load condition of 1 sequence are substituted into the equation (1), and the cumulative damage dm in 1 sequence is obtained.

Further, the number of sequences K when the cumulative damage DM calculated using the expression (2) becomes 1 or more is calculated as the fatigue life of the initial joint 131 under the fluctuating load condition, and the target fatigue life is set based on the shortest fatigue life among the fatigue lives of the initial joints.

After the target fatigue life is set, the optimal analysis of the optimal arrangement of the joints in the floor section model 111 is performed. In the optimization analysis, first, as shown in fig. 5, additional joints 153 are set between the initial joints 131 in the bottom plate portion model 111 at intervals of p=20 mm, and an optimization analysis model 151 is generated in which the initial joints 131 and the additional joints 153 are densely set as joint candidate points 155.

Next, the load conditions and constraint conditions shown in fig. 2 and 4 are applied, and the optimization analysis is performed, so that the joint candidate points 155 satisfying the optimization analysis conditions are obtained. In the optimization analysis, topology optimization by a density method is applied, and the penalty coefficient is set to 20 in the topology optimization, and discretization is performed.

In example 1, as an example of the present invention, an objective function related to the rigidity of the optimal analysis model 151, a constraint condition related to the cumulative damage DM (fatigue life) of the joint candidate points 155 held by the optimal analysis, and a constraint condition related to the number of points of the joint candidate points 155 held by the optimal analysis are set.

Regarding the objective function related to rigidity, the displacement of the rigidity evaluation point P (see fig. 14 (b)) under each of the load condition of the first vibration mode and the load condition of the second vibration mode is set to be equal to or less than the displacement of the rigidity evaluation point P when the bottom plate portion model 111 to which the initial joint 131 is set is subjected to stress analysis.

Note that, regarding the constraint conditions concerning the fatigue life, the cumulative damage DM of the joint candidate point 155 under the fluctuating load condition was calculated in the same manner as the initial joint 131 described above. The fatigue life calculated from the cumulative damage DM of each joint candidate point 155 is set to be longer than the target fatigue life.

Further, the constraint condition concerning the number of points of the joint candidate points 155 is set to a condition that the number of points of the joint candidate points held by the optimization analysis is set to the number of points of the initial joint 131.

In example 1, as a comparison example, an example was given in which the constraint condition concerning the cumulative damage degree DM (fatigue life) was not given, but the optimal analysis condition was given in which the rigidity of the optimal analysis model was an objective function and only the number of points of the joint candidate points was the constraint condition. Here, the conditions concerning rigidity and the conditions concerning the number of points of the joint candidate points in the comparative example are the same as those of the invention example.

Fig. 10 shows the result of the reserved joint candidate point 155 in the inventive example, and fig. 15 shows the result of the reserved joint candidate point 155 in the comparative example. As is clear from comparing fig. 10 and 15, the arrangement characteristics of the bonding candidate points 155 are different from those of the comparative example in the inventive example mainly at the portions surrounded by the solid ellipses.

Further, the arrangement of the joint candidate points 155 which are retained by the optimization analysis is set as the optimal arrangement of the joints 157, and as shown in fig. 10 and 15, the rigidity and the fatigue life of the joints 157 are calculated for the optimal joint floor part model 161 in which the joints 157 of the optimal arrangement are set.

In the calculation of the rigidity and fatigue life, first, stress analysis is performed by applying the load condition of the first vibration mode shown in fig. 2 and the load condition of the second vibration mode shown in fig. 4 to the optimal joint bottom plate portion model 161 and the constraint condition.

Regarding the rigidity of the optimal joint floor part model 161, the displacement of the rigidity evaluation point P (see fig. 14 (b)) obtained by the stress analysis under each of the load conditions of the first vibration mode and the load conditions of the second vibration mode is set as an index.

Regarding the fatigue life of the joint 157, the shortest fatigue life among the fatigue lives calculated using the stress of the joint 157 obtained by the stress analysis of the optimal joint bottom plate portion model 161 is used as an index. In addition, in the calculation of the fatigue life of the joint 157, the nugget diameter of the joint 157 was set to 5mm, and the planar element of the component model to which the beam element modeled as the joint 157 was joined was cut again into a spider web shape (see fig. 9).

Further, the rigidity and the shortest fatigue life were also obtained for the bottom plate portion model 111 (fig. 14) in which the initial joint 131 was set, and the optimal analysis model 151 in which the initial joint 131 and the additional joint 153 before the optimal analysis were densely set, and were used as the base example and the reference example, respectively.

Fig. 16 shows the results of the rigidity improvement rates of the invention example, the reference example, and the comparative example, and fig. 17 shows the results of the shortest fatigue life magnifications of the invention example, the reference example, and the comparative example. The rate of improvement in rigidity in the invention example and the comparative example was obtained based on the displacement of the rigidity evaluation point P in the base plate portion model 111 in the reference example, and the shortest fatigue life ratio was set as the ratio of the shortest fatigue life of the initial joint 131 in the base plate portion model 111 in the reference example. In fig. 16, a black bar indicates the rate of increase in rigidity under the load condition of the first vibration mode, and a gray bar indicates the result of the rate of increase in rigidity under the load condition of the second vibration mode.

The rate of improvement in rigidity was positive in both the inventive examples and the comparative examples, and compared with the reference examples, the rigidity was improved, and the shortest fatigue life was also improved. As a result, as shown in fig. 16, the rigidity improvement ratio was 1.8% in the inventive example and slightly lower than 2.0% in the comparative example, but the rigidity was improved as compared with the reference example. As a result of the shortest fatigue life, as shown in fig. 17, the shortest fatigue life ratio in the inventive example was 2.4, and was also greater than the shortest fatigue life ratio (=1.1) in the comparative example, and was close to the shortest fatigue life ratio (=3.6) in the reference example.

Example 2

In example 1, although the above-described case where the optimal analysis of the joint is performed with respect to the rigidity as the objective function was made with respect to a part (floor portion) of the vehicle body, in example 2, the condition regarding the cumulative damage degree (fatigue life) of the joint candidate points held by the optimal analysis, the condition regarding the rigidity of the optimal analysis model, and the condition regarding the number of points of the joint candidate points held by the optimal analysis were set as the objective function or the constraint condition as the optimal analysis condition with respect to the vehicle body model 201 of the whole vehicle body (whole vehicle model (full vehicle model))) shown in fig. 18, and the optimal analysis of the joint in the vehicle body model was performed.

The vehicle body model 201 is configured to have a plurality of component models in which a vehicle body skeleton member and a vehicle body panel member (automobile panel part) are modeled by planar elements, and an initial joint in which the component models are joined as a component group is set in advance. The number of points of the initial junction is 4983 points, and the initial junction is modeled by beam elements that join the nodes of the planar elements of the component model.

First, additional joints are set at a minimum dotting interval of 20mm between initial joints in the vehicle body model 201, and the initial joints and the additional joints are densely set as joint candidate points, and an optimal analysis model 211 is generated (fig. 18 (a) (i) and 18 (b) (i)). Further, since the dotting intervals of the initial joints are different for each component group of the component model in the vehicle body model 201, the dotting intervals of the additional joints set in the vehicle body model 201 are not necessarily fixed, but the additional joints are set to be as uniform as possible and not lower than the minimum dotting intervals by 20mm.

In example 2, first, a variable load condition is set in which a load condition of the first vibration mode shown in fig. 18 (a) and a load condition of the second vibration mode shown in fig. 18 (b) are combined.

As shown in fig. 18 (a), regarding the load condition of the first vibration mode, the load input point (a in fig. 18 (a) (i)) is set at the left and right front suspension (front suspension) mounting position in the optimal analysis model 211, the alternating torsional load (torsional load) of ±2000N is input in the vehicle body up-down direction (Z direction), and regarding the constraint condition, the constraint is set at the rear portion of the left and right side members (side bell) 203 of the optimal analysis model 211 as the constraint point (B in fig. 18 (a) (i)) to perform complete constraint.

As shown in fig. 18B, regarding the load condition of the second vibration mode, the rear portion 207 of the left and right side members 203 of the optimal analysis model 211 is set as a load input point (a in fig. 18B (i)), an alternating lateral bending load (lateral bending load) of ±1000n is input in the vehicle body width direction (Y direction), regarding the constraint condition, the left and right front suspension mounting positions of the vehicle body model 201 are set as constraint points (B1 in fig. 18B (i)) to completely constrain, and the left and right mounting positions of the rear side sub-frames (sub-frames) and the vehicle body are set as constraint points (B2 in fig. 18B (i)) to constrain translational movement (translation).

Further, regarding the fluctuating load conditions, a combination of 1 cycle (fig. 18 (a)) of the load conditions input in the first vibration mode and 30 cycles (fig. 18 (b)) of the load conditions input in the second vibration mode was set to 1 sequence.

Next, stress analysis of the vehicle body model 201 is performed for each of the load condition and constraint condition of the first vibration mode (fig. 18 (a)) and the load condition and constraint condition of the second vibration mode (fig. 18 (b)), and the stress generated at the initial joint under the load condition of each vibration mode is obtained. In the calculation of the stress generated in the initial joining point, the portion to which Liang Yaosu in the component model 143 is joined is set based on the nugget diameter of the actual spot welding point, as in the spot welding portion 141 illustrated in fig. 9, and the planar element in the peripheral portion 149 is re-cut into the planar element in the spider web shape, and the stress value of the planar element is used.

Next, the number of repetitions N1 and N2 of different stress amplitudes σ1 and σ2 generated at the initial junction under the fluctuating load condition until the initial junction breaks when the initial junction is generated alone was obtained from the S-N line graph (fig. 7).

Then, the number of repetitions N1 and N2 until fracture at each stress amplitude and the number of cycles N1 (=1 cycle) of the load condition of the first vibration mode and the number of cycles N2 (=30 cycles) of the load condition of the second vibration mode under the varying load condition of 1 sequence are substituted into formula (1), and the cumulative damage dm in 1 sequence is obtained.

Further, the fatigue life of the initial joint under the fluctuating load condition is calculated as the number of sequences K when the cumulative damage degree DM calculated using the expression (2) becomes 1 or more, and the target fatigue life is set based on the shortest fatigue life among the fatigue lives of the initial joints.

Then, the optimization analysis model 211 is subjected to optimization analysis by applying a variable load condition that combines the load condition and constraint condition of the first vibration mode shown in fig. 18 (a) and the load condition and constraint condition of the second vibration mode shown in fig. 18 (b), and the joint candidate points satisfying the optimization analysis condition are obtained. In the optimization analysis, topology optimization by a density method is applied, and the penalty coefficient is set to 20 in the topology optimization, and discretization is performed.

In example 2, the objective function and the constraint condition for optimizing the analysis condition were set as the combinations shown in table 1 as invention examples 21, 22 and 23.

TABLE 1

(Table 1)

In invention example 21, an objective function related to the fatigue life of the joint candidate points held by the optimization analysis, a constraint condition related to the rigidity of the optimization analysis model 211, and a constraint condition related to the number of the joint candidate points held by the optimization analysis were set as the optimization analysis conditions. The target function related to the fatigue life is set to a condition that the fatigue life calculated from the cumulative damage DM of the joint candidate point is set to be greater than the target fatigue life and to be the maximum. The constraint condition concerning rigidity is set such that an average value of displacements of the left and right load input points a in stress analysis in which the load condition of the first vibration mode and the load condition of the second vibration mode are applied to the optimal analysis model 211 is equal to or less than an average value of displacements of the left and right load input points a in stress analysis in which the load condition similar to the original vehicle body model 201 is applied. Further, the constraint condition concerning the number of points of the joint candidate point is set to a condition that the number of points (=4983 points) of the initial joint point of the original vehicle body model 201 is set.

In invention example 22, the objective function related to the rigidity of the optimal analysis model 211, the constraint condition related to the fatigue life of the joint candidate points held by the optimal analysis, and the constraint condition related to the number of the joint candidate points held by the optimal analysis were set as the optimal analysis conditions. The objective function related to rigidity is set to a condition that the sum of strain energy (strain) of the optimal analysis model 211 when stress analysis is performed by giving the optimal analysis model 211 a load condition of the first vibration mode and a load condition of the second vibration mode is minimized. The constraint condition related to the fatigue life is set to a condition that the fatigue life calculated from the cumulative damage degree DM of the joint candidate point is greater than the target fatigue life and is the maximum. Further, the constraint condition concerning the number of points of the joint candidate point is set to a condition that the number of points (=4983 points) of the initial joint point of the original vehicle body model 201 is set.

In invention example 23, an objective function related to the number of points of the joint candidate points held by the optimization analysis, a constraint condition related to the fatigue life of the joint candidate points held by the optimization analysis, and a constraint condition related to the rigidity of the optimization analysis model 211 were set as the optimization analysis conditions. Regarding the objective function related to the number of points of the joint candidate points, a condition is set that the number of points of the joint candidate points is minimized. In addition, the joint candidate points that do not affect the rigidity performance or the fatigue life are not the object of the optimization analysis. The constraint condition related to the fatigue life is set to a condition that the fatigue life calculated from the cumulative damage degree DM of the joint candidate point is greater than the target fatigue life and is the maximum. Further, the constraint condition concerning rigidity is a condition that an average value of displacements of the left and right load input points a in stress analysis in which the load condition of the first vibration mode and the load condition of the second vibration mode are given to the optimal analysis model 211 is equal to or smaller than the original vehicle body model 201.

Further, assuming that the arrangement of the joint candidate points which is retained by the optimization analysis is the optimal arrangement of the joints, as shown in fig. 18, rigidity and fatigue life of the joints are calculated for the optimal joint vehicle body model 221 in which the joints of the optimal arrangement are set. In the calculation of the rigidity and fatigue life, the optimal joint body model 221 is given the load condition and constraint condition of the first vibration mode shown in fig. 18 (a) and the load condition and constraint condition of the second vibration mode shown in fig. 18 (b), and the stress analysis is performed.

Fig. 19 shows the results of the shortest fatigue life ratio (fig. 19 (a)), the rigidity improvement ratio (fig. 19 (b)) and the number of points of the reserved joining candidate points (fig. 19 (c)) in the invention examples 21, 22 and 23. Further, the results shown in fig. 19 are summarized and shown in table 2.

TABLE 2

(Table 2)

In fig. 19 and table 2, the shortest fatigue life ratio of the optimal joint body model 221 is set to be the ratio to the shortest fatigue life of the initial joint in the original body model 201. The rigidity improvement rate of the optimal joint vehicle body model 221 is obtained based on the displacement of the rigidity evaluation point (load input point a) in the original vehicle body model 201, and in fig. 19 b, a black bar chart shows the rigidity improvement rate under the load condition (torsional load) of the first vibration mode, and a gray bar chart shows the result of the rigidity improvement rate under the load condition (lateral bending load) of the second vibration mode.

As a result, the shortest fatigue life magnifications of the best joint body models 221 of the invention examples 21, 22 and 23 were all improved, and the shortest fatigue life magnifications of the invention example 21, in which the target condition was the fatigue life, were the highest, were 4.1 times.

The optimal joint vehicle body model 221 of each of invention example 21, invention example 22, and invention example 23 has positive rigidity improvement rates, and has rigidity greater than that of the original vehicle body model 201. As a result, in particular, in invention example 22 in which the target condition was set to be rigid, the rigidity was improved by 6.3% under the load condition of the first vibration mode (torsional load) and 8.3% under the load condition of the second vibration mode (lateral bending load), both of which were higher than those of invention examples 21 and 23.

Further, although the number of joints of the optimal joint vehicle body model 221 is 4893 points in the invention examples 21 and 22, similar to the original vehicle body model 201, 359 points (-7.3%) are reduced in the invention example 23 in which the target condition is set as the number of joints candidate points, compared with the original vehicle body model.

Industrial applicability

According to the present invention, it is possible to provide an optimal analysis method, device, and program for a joining position of a vehicle body, which can obtain an optimal position of a joining point that improves rigidity of the vehicle body and a fatigue life of the joining point for joining a component group in the vehicle body, and minimizes the number of points of the joining point, when a variable load is input to the vehicle body.

Description of the reference numerals

1. Optimizing and analyzing device

3. Display device

5. Input device

7. Storage device

9. Data memory for work

11. Arithmetic processing unit

13. Analysis object model setting unit

15. Optimization analysis model generation unit

17. Variable load condition setting unit

19. Target fatigue life setting unit

21. Optimizing analysis condition setting part

23. Optimization analysis unit

31. Optimizing and analyzing device

33. Arithmetic processing unit

34. Optimization analysis unit

35. Model generator for setting analysis object by selecting joint candidate point

37. Select joint candidate point performance calculation unit

39. Determination unit

41. Optimum junction point determining part

101. Vehicle body model file

111. Floor section model

113. Floor panel model

115. Channel model

117. Fixing piece inner side model

119. Outside model of fixing piece

121. Front floor beam model

123. Rear floor beam model

125. Front end face part

127. Rear end face part

131. Initial junction point

141. Spot welding part

143. Component model

145. Liang Yaosu

147. Center portion

149. Peripheral portion

151. Optimizing analytical model

153. Additional joint

155. Junction candidate point

157. Junction point

161. Best joint floor section model

201. Vehicle body model

203. Side beam

211. Optimizing analytical model

221. Optimal joint body model

Claims

1. A method for optimizing and analyzing the joint position of a vehicle body, wherein all or a part of a vehicle body model having a plurality of component models composed of beam elements, plane elements and/or three-dimensional elements and having an initial joint for joining a plurality of component models as a component group is subjected to optimization analysis for obtaining an optimal arrangement of the joint for any of an improvement in rigidity of the vehicle body model, an improvement in fatigue life of a joint joining the component groups in the vehicle body model, and a minimization of the number of points of the joint by executing the following steps by a computer,

The method for optimizing and analyzing the joint position of the vehicle body comprises the following steps:

an analysis object model setting step of setting all or a part of the vehicle body model as an analysis object model;

an optimal analysis model generation step of densely setting all joint candidate points that are candidates for the optimally arranged joint for the analysis object model, and generating an optimal analysis model;

a variable load condition setting step of setting a variable load condition for dividing a variable load applied to the optimal analysis model into a plurality of different vibration modes, and setting the variable load condition for each vibration mode as a variable load condition of 1 series by combining the load conditions for each vibration mode by a predetermined number of cycles;

a target fatigue life setting step of setting a target fatigue life of the optimal analysis model according to the number of sequences of the variable load conditions;

an optimal analysis condition setting step of calculating, for each of the load conditions of the vibration modes, a number of fracture repetitions of each of the joint candidate points, and a ratio of the number of cycles to the number of fracture repetitions of the load condition of the vibration modes, the sum of the number of sequences of the variable load conditions set by the target fatigue life setting step, being a cumulative damage degree of each of the joint candidate points, and setting, as an objective function or constraint condition as an optimal analysis condition, a condition relating to a cumulative damage degree of the joint candidate points retained by the optimal analysis, a condition relating to rigidity of the optimal analysis model, and a condition relating to a number of points of the joint candidate points retained by the optimal analysis, in order to perform the optimal analysis with respect to the optimal analysis of the optimal analysis model; and

And an optimization analysis step of applying the fluctuating load condition set in the fluctuating load condition setting step to the optimization analysis model, and performing optimization analysis under the optimization analysis condition to determine, as an optimal arrangement of the joint, an arrangement of the joint candidate points achieved with the aim of any one of reduction in the cumulative damage degree of the joint candidate points, improvement in the rigidity of the optimization analysis model, and minimization of the number of points of the joint candidate points that remain.

2. The method for optimizing and analyzing a joint position of a vehicle body according to claim 1, wherein,

the optimization analysis step is a step of performing topology optimization by a density method, and discretizing the topology optimization by setting a penalty coefficient to 4 or more.

3. A method for optimizing and analyzing the joint position of a vehicle body, wherein all or a part of a vehicle body model having a plurality of component models composed of beam elements, plane elements and/or three-dimensional elements and having an initial joint for joining a plurality of component models as a component group is subjected to optimization analysis for obtaining an optimal arrangement of the joint for any of an improvement in rigidity of the vehicle body model, an improvement in fatigue life of a joint joining the component groups in the vehicle body model, and a minimization of the number of points of the joint by executing the following steps by a computer,

an optimal analysis condition setting step of calculating, for each of the load conditions of the vibration modes, a number of fracture repetitions of each of the joint candidate points, and a ratio of the number of cycles to the number of fracture repetitions of the load condition of the vibration modes, the sum of the number of sequences of the variable load conditions set by the target fatigue life setting step, being a cumulative damage degree of each of the joint candidate points, and setting, as an objective function or constraint condition as an optimal analysis condition, a condition relating to a cumulative damage degree of the joint candidate points retained by the optimal analysis, a condition relating to rigidity of the optimal analysis model, and a condition relating to a number of points of the joint candidate points retained by the optimal analysis, in order to perform the optimal analysis with respect to the optimal analysis of the optimal analysis model;

An optimization analysis step of assigning the fluctuating load condition set in the fluctuating load condition setting step to the optimization analysis model, and performing optimization analysis under the optimization analysis condition, wherein the configuration of the joint candidate points, which is achieved for the purpose of any one of reduction in the cumulative damage degree of the joint candidate points, improvement in the rigidity of the optimization analysis model, and minimization of the number of points of the joint candidate points that remain, is retained as a temporary optimal configuration of the joint points;

a joint candidate point setting analysis object model generation step of selecting a joint candidate point of a predetermined number from the joint candidate points which are retained as a temporary optimal arrangement by the optimization analysis, and setting the selected joint candidate point in the analysis object model in place of the initial joint, thereby generating a joint candidate point setting analysis object model;

a selected joint candidate performance calculation step of performing stress analysis by applying a load condition and a constraint condition of each vibration mode in the fluctuating load condition set in the fluctuating load condition setting step to the selected joint candidate setting analysis object model, and calculating a fatigue life of the selected joint candidate under the fluctuating load condition and a rigidity of the selected joint candidate setting analysis object model using a result of the stress analysis;

A determination step of determining whether or not a fatigue life of the joining candidate point in the joining candidate point set analysis object model under the fluctuating load condition and a rigidity of the joining candidate point set analysis object model satisfy a given performance exceeding the analysis object model for which the initial joining point is set; and

and a best joint determination step of determining the arrangement of the selected joint candidate points as the best arrangement of the joint when the determination step is determined to satisfy the predetermined performance, wherein the conditions relating to the cumulative damage degree of the joint candidate points retained by the optimization analysis, the conditions relating to the rigidity of the optimization analysis model, or the conditions relating to the number of points of the joint candidate points retained by the optimization analysis set in the optimization analysis condition setting step are changed when the determination step is determined to not satisfy the predetermined performance, and wherein the optimization analysis step, the selected joint candidate point setting analysis object model generation step, the selected joint candidate point performance calculation step, and the determination step are repeated until the predetermined performance is satisfied.

4. An optimizing and analyzing device for the joint position of a vehicle body, wherein the optimizing and analyzing device is used for solving the optimal configuration of the joint, which is achieved by the aim of any one of improving the rigidity of the vehicle body model, improving the fatigue life of the joint for joining the component groups in the vehicle body model and minimizing the point number of the joint, aiming at all or part of the vehicle body model which is provided with a plurality of component models consisting of beam elements, plane elements and/or three-dimensional elements and is provided with an initial joint for joining the component groups,

the device for optimizing and analyzing the joint position of the vehicle body comprises:

an analysis object model setting unit that sets all or a part of the vehicle body model as an analysis object model;

an optimal analysis model generation unit that generates an optimal analysis model by densely setting all joint candidate points that are candidates for the optimally arranged joint points for the analysis object model;

a variable load condition setting unit that sets a variable load condition for dividing a variable load applied to the optimal analysis model into a plurality of different vibration modes, and sets a variable load condition for each of the vibration modes by combining the load conditions for a predetermined number of cycles into 1 series;

A target fatigue life setting unit that sets a target fatigue life of the optimal analysis model based on the number of times the load conditions are varied;

an optimal analysis condition setting unit that obtains a number of fracture repetitions of each of the joint candidate points for each of the load conditions of each of the vibration modes, obtains a ratio of the number of cycles of the load conditions of each of the vibration modes to the number of fracture repetitions, sets a sum of the number of sequences of the variable load conditions set by the target fatigue life setting unit as a cumulative damage degree of each of the joint candidate points, and sets a condition relating to a cumulative damage degree of the joint candidate points retained by the optimal analysis, a condition relating to rigidity of the optimal analysis model, and a condition relating to a number of points of the joint candidate points retained by the optimal analysis as an objective function or a constraint condition as an optimal analysis condition; and

and an optimization analysis unit configured to apply the fluctuating load condition set by the fluctuating load condition setting unit to the optimization analysis model, and perform optimization analysis under the optimization analysis condition, thereby obtaining, as an optimal arrangement of the joint, an arrangement of the joint candidate points, which is achieved with the aim of any one of reduction in the cumulative damage degree of the joint candidate points, improvement in the rigidity of the optimization analysis model, and minimization of the number of points of the joint candidate points that remain.

5. The optimal analysis device for a joint position of a vehicle body 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 factor to 4 or more.

6. An optimizing and analyzing device for the joint position of a vehicle body, wherein the optimizing and analyzing device is used for solving the optimal configuration of the joint, which is achieved by the aim of any one of improving the rigidity of the vehicle body model, improving the fatigue life of the joint for joining the component groups in the vehicle body model and minimizing the point number of the joint, aiming at all or part of the vehicle body model which is provided with a plurality of component models consisting of beam elements, plane elements and/or three-dimensional elements and is provided with an initial joint for joining the component groups,

an optimal analysis condition setting unit that obtains a number of fracture repetitions of each of the joint candidate points for each of the load conditions of each of the vibration modes, obtains a ratio of the number of cycles of the load conditions of each of the vibration modes to the number of fracture repetitions, sets a sum of the number of sequences of the variable load conditions set by the target fatigue life setting unit as a cumulative damage degree of each of the joint candidate points, and sets a condition related to a cumulative damage degree of the joint candidate points retained by the optimal analysis, a condition related to rigidity of the optimal analysis model, and a condition related to a number of points of the joint candidate points retained in the optimal analysis as an objective function or a constraint condition as an optimal analysis condition;

An optimization analysis unit configured to assign the fluctuating load condition set by the fluctuating load condition setting unit to the optimization analysis model, perform optimization analysis under the optimization analysis condition, and retain, as a temporary optimal arrangement of the joint, an arrangement of the joint candidate points achieved for any of a reduction in a cumulative damage degree of the joint candidate points, an improvement in rigidity of the optimization analysis model, and a minimization of the number of points of the retained joint candidate points;

a joint candidate point setting analysis target model generation unit configured to select a joint candidate point of a predetermined number from the joint candidate points held as a temporary optimal arrangement by the optimization analysis, and set the selected joint candidate point in the analysis target model in place of the initial joint, to generate a joint candidate point setting analysis target model;

a selected joint candidate performance calculation unit configured to apply a load condition and a constraint condition of each vibration mode in the fluctuating load condition set by the fluctuating load condition setting unit to the selected joint candidate setting analysis object model, perform stress analysis, and calculate a fatigue life of the selected joint candidate under the fluctuating load condition and a rigidity of the selected joint candidate setting analysis object model using a result of the stress analysis;

A determination unit configured to determine whether or not a fatigue life of the joint candidate point in the joint candidate point setting analysis object model under the fluctuating load condition and a rigidity of the joint candidate point setting analysis object model satisfy a predetermined performance exceeding the analysis object model for which the initial joint point is set; and

an optimal joint determination unit that determines the arrangement of the selected joint candidate points as the optimal arrangement of the joint when the determination unit determines that the predetermined performance is satisfied, and that, when the determination unit determines that the predetermined performance is not satisfied, changes a condition related to the cumulative damage degree of the joint candidate points retained by the optimization analysis, a condition related to the rigidity of the optimization analysis model, or a condition related to the number of points of the joint candidate points retained by the optimization analysis, which are set by the optimization analysis condition setting unit, until the predetermined performance is satisfied, and repeatedly performs processing of setting an analysis object model generation unit, the selected joint candidate point performance calculation unit, and the determination unit based on the optimization analysis unit, until the predetermined performance is satisfied.

7. An optimization analysis program for a joint position of a vehicle body, wherein an optimization analysis is performed for an optimal arrangement of a joint, which is achieved for any of the purposes of improving rigidity of the vehicle body model, improving fatigue life of a joint joining the component groups in the vehicle body model, and minimizing the number of points of the joint, is performed for all or a part of a vehicle body model having a plurality of component models composed of beam elements, planar elements, and/or three-dimensional elements, and having an initial joint joining the plurality of component models as component groups,

the optimal analysis program for the joint position of the vehicle body has a function of causing a computer to execute:

8. The optimal analysis program for a joint position of a vehicle body according to claim 7, wherein,

9. An optimization analysis program for a joint position of a vehicle body, wherein an optimization analysis is performed for an optimal arrangement of a joint, which is achieved for any of the purposes of improving rigidity of the vehicle body model, improving fatigue life of a joint joining the component groups in the vehicle body model, and minimizing the number of points of the joint, is performed for all or a part of a vehicle body model having a plurality of component models composed of beam elements, planar elements, and/or three-dimensional elements, and having an initial joint joining the plurality of component models as component groups,