Method, device and program for optimizing and analyzing joining position of vehicle body, and method for manufacturing vehicle body

Abstract

This optimization analysis method for the joining position of a vehicle body sets all or part of a vehicle body model as a model to be analyzed (S1), sets joint candidate lines for the model to be analyzed to generate a joint line optimization analysis model (S3), sets a variable load condition (S5) and a target fatigue life (S6), and performs component rigidity sensitivity analysis. A rigidity low-sensitivity component model having a low sensitivity with respect to rigidity performance is selected (S7), and a bonding wire / component shape optimization analysis model is generated (S8). Setting, as optimization analysis conditions (S9), a condition relating to the cumulative damage degree of the remaining bonding candidate line, a condition relating to the rigidity of the bonding line / member shape optimization analysis model, a condition relating to the length of the bonding candidate line remaining by the optimization analysis, and a condition relating to the volume fraction of the rigid low-sensitivity member; a variable load condition is provided to the bonding wire / member shape optimization analysis model to perform optimization analysis, and an optimal arrangement of the bonding wire and an optimal shape of the rigid low-sensitivity member model that fulfill the optimization analysis condition are obtained (S11).

Description

Technical Field

[0001] The present invention relates to an optimization analysis method, device, and program for optimizing joining positions of an automotive body, and a method for manufacturing the automotive body. In particular, the present invention relates to an optimization analysis method, device, and program for optimizing joining positions of an automotive body, and a method for manufacturing the automotive body, for finding the best position of a weld line that improves the stiffness of the automotive body and the fatigue life near a weld line for bonding and joining parts assemblies in the automotive body, and a method for manufacturing the automotive body. Background Art

[0002] In recent years, especially in the automobile industry, the weight reduction of vehicle bodies has been promoted due to environmental issues, and analysis based on computer aided engineering (hereinafter referred to as "CAE analysis") has become an indispensable technology for the design of vehicle bodies. It is known that in this CAE analysis, the improvement of rigidity and weight reduction are sought by using optimization techniques such as mathematical optimization, sheet thickness optimization, shape optimization, and topology optimization.

[0003] It is known that a structure such as a vehicle body is formed by joining a plurality of parts as a component group by welding or the like. If the amount of joining at the parts joined as a component group is increased (for example, if the continuous joining line based on electric arc welding or laser welding is increased), the rigidity of the vehicle body as a whole is improved. If the rigidity is improved, the stress generated in the parts as a whole is also suppressed, and the fatigue life of the parts is continuously improved. However, conversely, there are also cases where the fatigue life decreases due to the increase in local stress. Moreover, from the perspective of the manufacturing cost of the vehicle body, it is desired to reduce the amount of joining as much as possible. In addition, the configuration of the best welding position that improves the fatigue performance for multiple input conditions at the same time is also pursued.

[0004] Therefore, a method has been proposed to find the joint position (continuously joined welding position by laser, arc, etc.) where the parts are joined together in order to improve the rigidity and fatigue life of the vehicle body while suppressing the manufacturing cost of the vehicle body. As such method, there are methods of determining the joint position by experience, intuition, etc., and methods of increasing the number of joint positions at locations with high stress by stress analysis. In addition, when dealing with multiple performances, sometimes the trial and error method is used to determine the welding position configured to meet a certain performance by evaluating other performances and confirming it.

[0005] However, the method of determining the joining position by experience, intuition, etc. does not find the position of the joining line required to improve both rigidity and fatigue life. Therefore, there are cases where the joining line is set at a position that is not necessary for improving rigidity and fatigue life, and repeated trial and error is inefficient from the perspective of cost.

[0006] In addition, in the method of adding joints to the parts with high stress by stress analysis, when compared with the joint positions before the method is used to find the joint positions, changes can be seen in rigidity and fatigue life, but there are also many cases where the deformation of the parts is suppressed and the local stress is reversely increased. Therefore, the joint positions found by this method may not be the best, and the result is a trial-and-error design, which is inefficient.

[0007] In contrast, Patent Document 1 discloses a method and apparatus for optimizing the joint position of point joining such as spot welding, continuous joining such as laser welding, arc welding or welding, which are used in joining a plurality of parts constituting a structural body model including two-dimensional elements and / or three-dimensional elements. In addition, Patent Document 2 discloses a device and method for determining a continuous joining application part of a structural body model that can easily determine a part suitable for continuous joining without complicated operations in a structural body model including two-dimensional elements and / or three-dimensional elements constituting parts.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Application Publication No. 2013-025593

[0011] Patent Document 2: Japanese Patent Application Publication No. 2016-71770 Summary of the invention

[0012] Problems to be solved by the invention

[0013] During the driving of a car, a variable amplitude load whose amplitude, direction, etc. are not constant and change in a complex manner over time is input to the car body. Therefore, it is expected that a technology for finding the optimal length and configuration of the joint line that can improve the rigidity of the car body and the fatigue life near the continuous joint line when a complex variable load is input to the car body is required. In the chassis component or suspension part of a car, a structure in which components are joined to each other by arc welding can be seen. However, it is known that even if the base metal strength of the component is improved, the fatigue strength around the arc welded part is not improved due to the influence of the notch geometry of the arc weld toe. Therefore, in the future, it is expected that the application of high-tensile steel sheets will be expanded for chassis and suspension parts, and the optimization of arc welding joint configuration will become important. On the other hand, in order to promote the lightweighting of chassis and suspension parts due to the demand for weight reduction of automotive bodies, it is important to improve the rigidity and fatigue performance of the entire chassis and suspension component group by optimizing the arc welding joint configuration.

[0014] However, in the technologies disclosed in Patent Documents 1 and 2, the optimal position of spot joining or continuous joining is determined by setting the maximum volume ratio of material, the maximum rigidity, the minimum displacement, the minimum stress, etc. as analytical conditions for performing optimization calculation, and no consideration is given to improving the fatigue life of spot joining and continuous joining. In addition, the technology disclosed in Patent Document 2 mainly targets automobile bodies joined by spot welding, and defines spot joining elements having a spot joining interval below a specified value as a location suitable for continuous joining, and there is also a problem that it cannot be applied to chassis and running parts of automobiles in which parts are continuously joined to each other by arc welding, etc.

[0015] The present invention has been completed in view of the above-mentioned problems, and its purpose is to provide an optimization analysis method, device and program for optimizing the joining position of the vehicle body, and a method for manufacturing the vehicle body, which can obtain the optimal configuration of the weld line that minimizes the length of the weld line while improving the rigidity of the vehicle body and the fatigue life of the continuous weld line that joins the component groups in the vehicle body when a simple or variable load is input to the vehicle body, while achieving lightweight parts that do not contribute to improving the rigidity.

[0016] Means for solving problems

[0017] The present invention relates to a method for optimizing and analyzing the joint position of a vehicle body. Regarding all or part of a vehicle body model having a plurality of component models including beam elements and plane elements and having an initial joint line for joining the plurality of component models as a component group, a computer executes the following steps to perform optimization analysis to obtain an optimal arrangement of the joint lines for the purpose of improving the rigidity of the vehicle body model, improving the fatigue life near the joint line for joining the component group in the vehicle body model, or minimizing the length of the joint line, and to obtain an optimized shape of the component model having low sensitivity to rigidity performance, wherein the optimization analysis method comprises: an analysis object model setting step of setting all or part of the vehicle body model as an analysis object model; and a joint line optimization analysis model generation step of generating all candidate joint lines for the analysis object model as candidates for the joint lines of the optimal arrangement. a step of setting a variable load condition, dividing the variable load provided to the joint line optimization analysis model into a plurality of loading conditions of different vibration patterns, and setting a variable load condition in which the load conditions of the vibration patterns are combined in a predetermined number of cycles to form a sequence; a step of setting a target fatigue life, setting a target fatigue life of the joint line optimization analysis model in accordance with the number of sequences of the variable load condition; and a step of analyzing the rigidity sensitivity of a component, setting an objective function related to the rigidity performance of the joint line optimization analysis model, constraints related to the volume of the component model constituting the joint line optimization analysis model, and the variable load condition provided to the joint line optimization analysis model, and performing a sensitivity analysis of the component model constituting the joint line optimization analysis model that satisfies the objective function under the variable load condition and the constraint condition. analysis), selecting a rigid low-sensitivity component model with low sensitivity to rigid performance based on the sensitivity of the component model; a joining line·component shape optimization analysis model generation step, generating a joining line·component shape optimization analysis model in which the joining candidate lines of the joining line optimization analysis model and the plane elements constituting the rigid low-sensitivity component model are set as a design space;an optimization analysis condition setting step, in order to perform optimization analysis with the joint line·component shape optimization analysis model as an optimization object, the number of cycles to failure near each joint candidate line is obtained for the load condition of each vibration mode, the sum of the number of sequences of the variable load condition set by the target fatigue life setting step, which is the ratio of the number of cycles to the number of cycles of the load condition of each vibration mode, is obtained as the linear cumulative damage of each joint candidate line, a condition related to the cumulative damage of the joint candidate line remaining after the optimization analysis, a condition related to the rigidity of the joint line·component shape optimization analysis model, and a condition related to the length of the joint candidate line remaining after the optimization analysis are set as an objective function or constraint condition as an optimization analysis condition, and a volume ratio (volume constraint) of the rigidity low-sensitivity component model is set. ratio); and an optimization analysis step, providing the variable load condition set in the variable load condition setting step to the joint line·component shape optimization analysis model, performing optimization analysis under the optimization analysis condition, obtaining the configuration of the joint candidate line achieved for the purpose of reducing the cumulative damage degree of the joint candidate line, improving the rigidity of the joint line·component shape optimization analysis model, and minimizing the length of the remaining joint candidate line as the optimal configuration of the joint line, and obtaining the residual shape of the rigidity low-sensitivity component model as the optimal shape of the component model with low sensitivity to rigidity performance. ;

[0018] Preferably, the optimization analysis step performs topology optimization based on a density method, and in the topology optimization, discretization is performed by setting a penalty coefficient to 4 or more.

[0019] The present invention relates to an optimization analysis device for a joint position of a vehicle body. With respect to all or part of a vehicle body model having a plurality of component models including beam elements and plane elements and having an initial joint line for joining the plurality of component models as a component group, a computer executes the following steps to perform optimization analysis for obtaining an optimal arrangement of the joint lines for the purpose of improving the rigidity of the vehicle body model, improving the fatigue life near the joint line for joining the component group in the vehicle body model, or minimizing the length of the joint line, and obtaining an optimal shape of the component model with low sensitivity to rigidity performance, wherein the optimization analysis device comprises: an analysis target model setting unit for setting all or part of the vehicle body model as an analysis target model; a joint line optimization analysis model generation unit for generating a joint line optimization analysis model in which all candidate joint lines that are candidates for the joint line of the optimal arrangement are set for the analysis target model; and a variable load condition setting unit for dividing a variable load provided to the joint line optimization analysis model into a plurality of different a load condition for a vibration mode, setting a variable load condition in which the load conditions of each vibration mode are combined in a predetermined number of cycles to form a sequence of one; a target fatigue life setting unit, setting a target fatigue life of the joint line optimization analysis model in the number of sequences of the variable load condition; a component rigidity sensitivity analysis unit, setting an objective function related to the rigidity performance of the joint line optimization analysis model, a constraint condition related to the volume of the component model constituting the joint line optimization analysis model, and a variable load condition provided to the joint line optimization analysis model, performing a sensitivity analysis of the component model constituting the joint line optimization analysis model that satisfies the objective function under the variable load condition and the constraint condition, and selecting a rigidity low-sensitivity component model with low sensitivity to rigidity performance based on the sensitivity of the component model; a joint line·component shape optimization analysis model generation unit, generating a joint line·component shape optimization analysis model in which the candidate joint line of the joint line optimization analysis model and the plane elements constituting the rigidity low-sensitivity component model are set as a design space;The optimization analysis condition setting unit is configured to perform optimization analysis with the joint line and component shape optimization analysis model as an optimization object, obtain the number of fracture repetitions near each of the joint candidate lines for the load conditions of each vibration mode, obtain the total number of sequences of the variable load conditions set by the target fatigue life setting unit, which is the ratio of the number of cycles of the load conditions of each vibration mode to the number of fracture repetitions, as the cumulative damage degree of each of the joint candidate lines, and set a condition related to the cumulative damage degree of the joint candidate line remaining after the optimization analysis, a condition related to the rigidity of the joint line and component shape optimization analysis model, and a condition related to the length of the joint candidate line remaining after the optimization analysis as the optimization analysis conditions. The objective function or constraint condition of the component is set, and the constraint condition related to the volume rate of the rigid low-sensitivity component model is set; and the optimization analysis unit provides the variable load condition set in the variable load condition setting unit to the joint line component shape optimization analysis model, performs optimization analysis under the optimization analysis condition, and obtains the configuration of the joint candidate line achieved for the purpose of reducing the cumulative damage degree of the joint candidate line, improving the rigidity of the joint line component shape optimization analysis model, and minimizing the length of the remaining joint candidate line as the optimal configuration of the joint line, and obtains the residual shape of the rigid low-sensitivity component model as the optimal shape of the component model with low sensitivity to rigidity performance. ;

[0020] Preferably, the optimization analysis unit performs topology optimization based on a density method, and in the topology optimization, a penalty coefficient is set to 4 or more to perform discretization.

[0021] The present invention relates to a program for optimizing the joint position of a vehicle body, which performs optimization analysis on all or part of a vehicle body model having a plurality of component models including beam elements and plane elements and having an initial joint line for joining the plurality of component models as a component group, to find the optimal arrangement of the joint lines for the purpose of improving the rigidity of the vehicle body model, improving the fatigue life near the joint line for joining the component group in the vehicle body model, or minimizing the length of the joint line, and to find the optimal shape of the component model with low sensitivity to rigidity performance, wherein the optimization analysis program causes a computer to function as the following units: an analysis target model setting unit for setting all or part of the vehicle body model as an analysis target model; a joint line optimization analysis model generation unit for generating a joint line optimization analysis model in which all candidate joint lines that are candidates for the joint line of the optimal arrangement are set for the analysis target model; and a variable load condition setting unit for dividing a variable load provided to the joint line optimization analysis model into a plurality of different a load condition of a vibration mode, setting a variable load condition in which the load conditions of each vibration mode are combined with a predetermined number of cycles to form a sequence of one; a target fatigue life setting unit, setting a target fatigue life of the joint line optimization analysis model with the sequence number of the variable load condition; a component rigidity sensitivity analysis unit, setting an objective function related to the rigidity performance of the joint line optimization analysis model, a constraint condition related to the volume of the component model constituting the joint line optimization analysis model, and a variable load condition provided to the joint line optimization analysis model, performing sensitivity analysis of the component model constituting the joint line optimization analysis model that satisfies the objective function under the variable load condition and the constraint condition, and selecting a rigidity low-sensitivity component model with low sensitivity to rigidity performance based on the sensitivity of the component model; a joint line·component shape optimization analysis model generation unit, generating a joint line·component shape optimization analysis model in which the joint candidate line of the joint line optimization analysis model and the plane elements constituting the rigidity low-sensitivity component model are set as a design space;The optimization analysis condition setting unit is configured to perform optimization analysis with the joint line and component shape optimization analysis model as an optimization object, obtain the number of fracture repetitions near each of the joint candidate lines for the load conditions of each vibration mode, obtain the total number of sequences of the variable load conditions set by the target fatigue life setting unit, which is the ratio of the number of cycles of the load conditions of each vibration mode to the number of fracture repetitions, as the cumulative damage degree of each of the joint candidate lines, and set a condition related to the cumulative damage degree of the joint candidate lines remaining after the optimization analysis, a condition related to the rigidity of the joint line and component shape optimization analysis model, and a condition related to the length of the joint candidate lines remaining after the optimization analysis as the optimization conditions. The objective function or constraint condition of the variable load condition setting unit is set to set the constraint condition related to the volume ratio of the rigid low-sensitivity component model; and the optimization analysis unit provides the variable load condition set in the variable load condition setting unit to the joint line component shape optimization analysis model, performs optimization analysis under the optimization analysis condition, and obtains the configuration of the joint candidate line achieved for the purpose of reducing the cumulative damage degree of the joint candidate line, improving the rigidity of the optimization analysis model, and minimizing the length of the remaining joint candidate line as the optimal configuration of the joint line, and obtains the residual shape of the rigid low-sensitivity component model as the optimal shape of the component model with low sensitivity to rigidity performance. ;

[0022] Preferably, the optimization analysis unit performs topology optimization based on a density method, and in the topology optimization, a penalty coefficient is set to 4 or more to perform discretization.

[0023] The present invention relates to a method for manufacturing a vehicle body, which is a method for manufacturing a vehicle body that optimizes the configuration of a joining line for joining a component group in a vehicle body to improve the rigidity of the vehicle body and the fatigue life of the joining line, wherein the method for optimizing the joining position of the vehicle body according to the present invention is used to find the optimal shape of the component model with low sensitivity to rigidity performance and the optimal configuration of the joining line, and the shape of the corresponding vehicle body component is changed based on the optimal shape of the component model, and the joining position of the component group in the vehicle body is determined based on the determined optimal configuration of the joining line, and the component group of the vehicle body is joined at the determined joining position.

[0024] Effects of the Invention

[0025] In the present invention, all or part of the body model of the automobile is set as the analysis target model, and an optimized analysis model is generated by setting the candidate joining line as the component group for the analysis target model, and the optimization analysis conditions (objective function or constraint conditions) related to the length of the candidate joining line set as the optimization target, the fatigue life of the candidate joining line, the rigidity of the optimized analysis model, and the length of the joining line are set to perform optimization analysis on the candidate joining line. Thus, when the load is input to the body as an inconstant variable load over time as in the actual driving of the automobile, the optimal position of the joining line can be obtained for the purpose of minimizing the length of the candidate joining line, improving the rigidity of the analysis target model, and improving the fatigue life near the joining line where the component group is joined, and at the same time, the weight reduction of the parts that do not contribute to the rigidity improvement can be achieved. In addition, thereby, the optimal arrangement of the welding (joining) position of arc welding or the like in the body structure, the fatigue life near the joining line can be improved, the rigidity of the body can be improved, and the body structure can be lightweighted, and the welding cost can be reduced and the body can be made more rigid and lightweight. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a block diagram of the optimization analysis device for the joint position of the vehicle body according to the first embodiment of the present invention.

[0027] Figure 2 This is a diagram showing a rear subframe model used as an analysis target model in the first embodiment of the present invention.

[0028] Figure 3 This is a diagram for explaining an initial joint line that is preset for the rear subframe model as an example of an analysis target model in the first embodiment of the present invention.

[0029] Figure 4 This is a diagram showing an example of an arc welded portion obtained by modeling an initial joining line in calculation of fatigue life of the initial joining line in Embodiment 1 of the present invention.

[0030] Figure 5 This is a diagram showing an example of load conditions and constraint conditions in the first vibration mode and the second vibration mode provided to the rear subframe model used as the analysis target model in the first embodiment of the present invention.

[0031] Figure 6 It is a diagram showing an example of an optimized analytical model in which an initial joining line pre-set for an analytical target model and an additional joining line added to the analytical target model are set as candidate joining lines in embodiment 1 of the present invention ((a) is the entire optimized analytical model, and (b) is a partially enlarged view of the optimized analytical model).

[0032] Figure 7 This is a diagram showing an example of a variable load condition set in the first embodiment of the present invention.

[0033] Figure 8 This is a diagram for explaining an SN diagram (stress endurance diagram) used for calculation of fatigue life under variable load conditions in the first embodiment.

[0034] Fig. 9 This is a diagram showing an example of the results of the fatigue life of the initial joining line and the position of the initial joining line of the shortest three lower fatigue lives (minimum fatigue life) under the variable load condition in the first embodiment of the present invention. Fig. 9 (b) shows a state where the rear subframe model is viewed from the bottom.

[0035] Fig.10 The figures show the results of sensitivity analysis on rigidity performance using the rear subframe model in the first embodiment of the present invention ((a) is a variable load condition (input 1), and (b) is a variable load condition (input 2)).

[0036] Fig.11 This is a diagram showing an example of the element density distribution of the joint line and the component shape after the optimized analysis in which the rear subframe model is set as the analysis object and the optimized analysis conditions related to the rigidity and fatigue life are set in the first embodiment and the examples of the present invention ((a) is the variable load condition (input 1), (b) is the variable load condition (input 2)). Fig.11 In FIG, only the elements set as the design space are illustrated.

[0037] Fig.12 is based on Fig.11 FIG. 1 is a diagram showing an example of weight reduction in a component shape based on the result of the optimization analysis shown.

[0038] Fig.13 This is a flowchart showing the flow of processing in the optimization analysis method of the joining position of the vehicle body according to the first embodiment of the present invention.

[0039] Fig.14 This is an explanatory diagram of rigidity evaluation points in a rear subframe model that is a part of a vehicle body model to be analyzed in the embodiment.

[0040] Fig.15 The diagram shows the optimum arrangement of the joining lines obtained by the optimization analysis in the invention example in which the rear subframe model is set as the analysis object and the optimization analysis conditions related to the rigidity, the joining length and the volume ratio of the low-sensitivity component are set in the embodiment.

[0041] Fig.16 The diagram shows the optimum arrangement of the joining lines obtained by the optimization analysis in the comparative example in which the rear subframe model is set as the analysis object and the optimization analysis conditions related to the rigidity and the joining length are set in the embodiment. DETAILED DESCRIPTION

[0042] Before describing the optimization analysis method, device and program of the joint position of the vehicle body according to the first embodiment of the present invention, and the manufacturing method of the vehicle body according to the second embodiment, the vehicle body model used as the object in the present invention is described. In the specification and drawings of the present application, the front-rear direction of the vehicle body, the left-right direction of the vehicle body and the up-down direction of the vehicle body are respectively represented as the X direction, the Y direction and the Z direction. In the specification and drawings, for elements having substantially the same function and structure, repeated description is omitted by marking the same reference numerals.

[0043] <Body model and analysis target model>

[0044] The automotive body model used as an object in the present invention is composed of a plurality of component models such as body frame parts and chassis components, and these component models are modeled using beam elements and plane elements.

[0045] Generally speaking, vehicle body frame parts, chassis parts, and the like are mainly formed of metal sheets with a thin sheet thickness, and therefore, the component models constituting the vehicle body model may be composed of only planar elements.

[0046] The vehicle body model has an initial joint line for joining a plurality of component models as a component set. The initial joint line is obtained by modeling a joint line of arc welding or laser welding for joining a plurality of automobile components as a component set using plane elements and three-dimensional elements.

[0047] For example, when two component models composed of plane elements are joined by an initial joining line modeled as the plane elements, the plane elements of the initial joining line are connected to both the plane elements of the two component models.

[0048] Furthermore, when the initial joint line is modeled as a solid element, in order to distribute the translational force acting on the initial joint line to the component model, the plane element of the component model and the solid element of the initial joint line are connected by a rigid body element.

[0049] The present invention analyzes the deformation caused by the variable load acting on the analysis object model (described later) as the whole or a part of the vehicle body model, so each component model in the vehicle body model is modeled as an elastic body, a viscoelastic body, or an elastic-plastic body. In addition, the material properties, element information, and information related to the initial joint line in each component group of each component model constituting the vehicle body model are stored in the vehicle body model file 101 (refer to Figure 1 ).

[0050] [Implementation Method 1]

[0051] <Analysis device for optimizing the joint position of a vehicle body>

[0052] The structure of the optimization analysis device for the joint position of the vehicle body (hereinafter simply referred to as “optimization analysis device”) according to the first embodiment of the present invention will be described below.

[0053] An optimization analysis device is a device that takes the entire or a part of a vehicle body model as an analysis object model, and performs an optimization analysis on the analysis object model to find the optimal configuration of the joining line to achieve any one of the following objectives: improving the rigidity of the vehicle body model, improving the fatigue life of the joining line for joining a component group in the vehicle body model, and minimizing the length of the joining line.

[0054] exist Figure 1 An example of the structure of the optimization analysis device 1 according to the first embodiment is shown in FIG. The optimization analysis device 1 is composed of a PC (personal computer) and the like. Figure 1 As shown, the optimization analysis device 1 has a display device 3, an input device 5, a memory storage 7, a work data memory 9, and an arithmetic processing unit 11. The display device 3, the input device 5, the memory storage 7, and the work data memory 9 are connected to the arithmetic processing unit 11, and perform their respective functions through instructions from the arithmetic processing unit 11. The functions of the components of the optimization analysis device 1 according to the first embodiment are described below.

[0055] ≪Display device≫

[0056] The display device 3 is used to display the vehicle body model, the analysis target model, the analysis results, etc., and is composed of a liquid crystal monitor (LCD monitor) or the like.

[0057] ≪Input device≫

[0058] The input device 5 is used for the vehicle body model file 101 ( Figure 1 ), the reading of the vehicle body model, the display of the analysis object model, etc., and the input of the operator's instructions are composed of a keyboard, a mouse, etc.

[0059] Storage Devices

[0060] The storage device 7 is used for the vehicle body model file 101 ( Figure 1 ) and other files, storage of analysis results, etc., and is composed of a hard disk, etc.

[0061] ≪Working data storage≫

[0062] The working data memory 9 is used for temporary storage and calculation of data used by the calculation processing unit 11 and is composed of a RAM (Random Access Memory) and the like.

[0063] ≪Calculation Processing Unit≫

[0064] like Figure 1 As shown in FIG. 1 , the calculation processing unit 11 includes an analysis target model setting unit 13, a weld line optimization analysis model generation unit 15, a variable load condition setting unit 17, a target fatigue life setting unit 18, a component rigidity sensitivity analysis unit 19, a weld line and component shape optimization analysis model generation unit 20, an optimization analysis condition setting unit 21, and an optimization analysis unit 23, and is composed of a CPU (central processing unit) of a PC or the like. These units function by executing a predetermined program in the CPU. The functions of each unit of the calculation processing unit 11 are described below.

[0065] (Analysis object model setting part)

[0066] The analysis target model setting unit 13 acquires a vehicle body model from the vehicle body model file 101 , and sets the entire or a part of the acquired vehicle body model as the analysis target model.

[0067] An example of the processing performed by the analysis target model setting unit 13 is described below. First, the operator instructs the vehicle body model to be read from the vehicle body model file 101 using the input device 5, and the vehicle body model is read from the storage device 7. Next, the vehicle body model is displayed on the display device 3 in accordance with the operator's instruction. Then, the operator specifies a portion to be set as a target of optimization analysis in the vehicle body model displayed on the display device 3 in accordance with the operator's instruction. The analysis target model setting unit 13 sets the specified portion as the analysis target model.

[0068] exist Figure 22 shows an example in which a simplified rear subframe model 111 of a suspension subframe (hereinafter referred to as a rear subframe) on the rear side of a chassis member is set as an analysis target model.

[0069] exist Figure 2 In the rear subframe model 111 shown, as a component model, the side frame upper member 112 and the side frame lower member 113 on the right side are joined by arc welding to form a side frame R211. Similarly, the side frame upper member 114 and the side frame lower member 115 on the left side are joined by arc welding to form a side frame L212. The cross member upper member 116 and the cross member lower member 117 on the front side of the vehicle body are joined by arc welding to form a cross member front member 213. The cross member front member 118 and the cross member rear member 119 on the rear side of the vehicle body are joined by arc welding to form a rear cross member 214. These side frame R211, side frame L212, cross member front member 213 and rear cross member 214 are further joined by arc welding to form a parallel cross structure. In addition, the components supporting the suspension and the components for installing the link mechanism leading to the tire, namely brackets 120, 121, and 122, are joined to the cross-shaped structure by arc welding. Figure 2 Only the right side is shown, but the same bracket is also installed on the left side). These component models are modeled as plane elements. Figure 2 In FIG. 1 , components connecting the tire input point 100 and the brackets 120 , 121 , 122 and the rear cross member 214 are simplified by straight lines representing bar elements.

[0070] And, if Figure 3 As shown, the rear subframe model 111 is pre-set with an initial joining line 131 for joining each component model as a component group, and the length of the initial joining line is 6540 mm. Figure 4 As shown in FIG. 1 , the initial joint line 131 is modeled as a plane element that is connected to the plane element of the component model by sharing nodes. The thickness of the initial joint line 131 is set to the thinner plate thickness of the component model to be joined. In addition, the material property value of the initial joint line 131 is set to be the same as that of the component model.

[0071] In addition, in order to set the variable load conditions and constraint conditions to be provided to the rear subframe model 111 by the variable load condition setting unit 17 described later, as shown in FIG. Figure 5 As shown, brackets 120, 121, 122 and rear cross beam 214 and tire input point 100 (refer to Figure 2 ) are connected by rod elements. The tire input point 100 is set as the load input point A, and the four points of the mounting bushing a, b, c, and d in the figure are set as complete restraint points.

[0072] (Joint line optimization analysis model generation section)

[0073] like Figure 6 As shown, the welding line optimization analysis model generation unit 15 generates a welding line optimization analysis model 151 by setting all welding line candidates that are candidates for the best arrangement for the analysis target model, that is, the largest welding line that can be set.

[0074] exist Figure 6 2 shows a joining line optimization analytical model 151 generated by setting a candidate joining line 155 for the rear subframe model 111 . Figure 6 (b) shows a part of the optimized analytical model 151 of the bonding line, where the solid line represents the initial bonding line 131 and the dotted line represents the additional bonding line 153. Figure 6 In (a), these initial joining lines 131 and additional joining lines 153 are shown as candidate joining lines 155. The additional joining lines 153 may be added by connecting the intermittently set initial joining lines 131 (b-1, b-2), extended at the ends of the initial joining lines 131 (b-3), or changed in shape when there is no space for setting the additional joining lines 153. The additional joining lines 153 may be modeled as a plane element or a three-dimensional element, similarly to the initial joining lines 131 described above.

[0075] (Variable load condition setting section)

[0076] The variable load condition setting unit 17 divides the variable load provided to the optimization analysis model into load conditions of a plurality of different vibration modes, and sets a variable load condition in which the load conditions of the vibration modes are combined in a predetermined number of cycles to form one sequence.

[0077] The variable load is obtained by dividing the magnitude, position, and direction of the load input to the analysis target model into one or more different vibration modes and combining each vibration mode at a predetermined number of cycles, simulating the variable load input to the vehicle body that changes over time when the actual vehicle is running. In addition, the variable load condition is provided in the calculation of the fatigue life of the initial joint line 131 and the joint candidate line 155 described later.

[0078] The variable load condition setting unit 17 may divide the variable load into a plurality of loads of different vibration modes, and set a variable load condition combining the variable load conditions and a constraint condition of the constraint analysis target model for each variable load condition.

[0079] In the first embodiment, regarding the variable load condition, in the rear subframe model 111, the mounting sleeves a to d mounted on the vehicle body are completely constrained, the tire input point 100 on the right side of the vehicle body is set as the load input point A, and the load input point A is set as follows: Figure 5 The load condition of the first vibration mode is that the variable load of ±2.5 kN is input in the forward and backward direction (input 1) as shown in (a) and Figure 5 The conditions of the second vibration mode are as shown in (b) where a variable load of ±6.0 kN is input in the inner and outer directions (input 2).

[0080] And, if Figure 7 As shown in the schematic diagram of the variable load history, the variable load condition is a combination of the load condition of the first vibration mode, 1 cycle, and the load condition of the second vibration mode, 5 cycles, to form a variable load condition of 1 series. Furthermore, fatigue life is considered in the load variable condition. Figure 7 The curve graph shown is a curve graph of alternating (reversed) variable loads with the magnitude of the load as the amplitude under each condition of the load condition of the first vibration mode and the load condition of the second vibration mode in order to represent the number of cycles of each of the load condition of the first vibration mode and the load condition of the second vibration mode in a sequence of variable load conditions.

[0081] (Target fatigue life setting section)

[0082] The target fatigue life setting unit 18 sets the target fatigue life of the weld line optimization analysis model 151 according to the number of sequences of the variable load conditions.

[0083] As the target fatigue life of the welding line optimization analysis model 151, the load condition of the vibration mode among the variable load conditions set by the variable load condition setting unit 17 is provided to the analysis target model and stress analysis is performed separately, and the fatigue life is calculated using commercially available fatigue life prediction software, and the target fatigue life is set based on the shortest fatigue life. In addition, a predetermined number of sequences may be set as the target fatigue life of the welding line optimization analysis model 151 based on a conventional empirical rule.

[0084] Generally speaking, the load input to the body of an actual automobile is not constant over time, so the initial joint line 131 can be regarded as a stress state in which stresses of various amplitudes are randomly generated. To evaluate the fatigue life of the initial joint line 131 under such a stress state, the linear cumulative damage rule is used.

[0085] In the cumulative fatigue damage law, first, the state where stresses of various amplitudes are randomly generated is considered to be σ1, σ2, σ3, σ m Next, suppose that each stress amplitude σ1, σ2, σ3, ··σ m The number of repetitions (fracture repetitions) N1, N2, N3, etc., until fracture (fatigue fracture) at each stress amplitude is generated separately. m From Figure 8 The SN line diagram shown is read. These stress amplitudes are repeated for n1, n2, n3, etc. m The damage degree is considered as n1 / N1, n2 / N2, n3 / N3··n m / N m .

[0086] In the cumulative fatigue damage law, as shown in formula (1), the sum of the damage degrees under each stress amplitude, that is, the cumulative damage degree dm, is calculated. And when the cumulative damage degree dm ≥ 1, fatigue failure occurs. In the variable load condition of receiving irregular repeated variable loads, the Rainflow Counting method can also be used to determine the stress amplitudes σ1, σ2, σ3, ··σ m and the number of repetitions n1, n2, n3...n m .

[0087]

Mathematical formula 1

[0088]

[0089] The specific process of calculating the target cumulative damage degree of the initial joint line 131 under the variable load condition by the target fatigue life setting unit 18 is as follows.

[0090] First, the stress acting on each initial bonding line 131 obtained by performing stress analysis for the load conditions of each vibration mode in the variable load condition is defined as different stress amplitudes σ1, σ2, σ3, σ4, σ5, σ6, σ7, σ8, σ9, σ10, σ21, σ22, σ3, σ4, σ5, σ6, σ7, σ8, σ9, σ1 ...0, σ21, σ3, σ4, σ5, σ6, σ7, σ8, σ9, σ11, σ22, σ3, σ3, σ4, σ5, σ6, σ7, σ8, σ9, σ10, σ21, σ3, σ3, m .

[0091] Next, the target fatigue life setting unit 18 calculates the number of repetitions (fracture repetition number) N1, N2, N3, ... N of each stress amplitude generated when the initial bonding line 131 is generated until the initial bonding line 131 is broken. m According to the SN line chart ( Figure 8 ) and find the answer.

[0092] Next, the number of repetitions until fracture (fracture repetition number) N1, N2, N3, ... N m The number of cycles n1, n2, n3, ... n of the load conditions of each vibration mode in one sequence of the variable load conditions m Substituting into formula (1), the cumulative damage degree dm in 1 sequence is calculated. Furthermore, the cumulative damage degree DM when 1 sequence of the variable load condition is continuously repeated K times (K sequence) is calculated according to formula (2). Then, the sequence number K when the cumulative damage degree DM becomes 1 or more is calculated as the fatigue life of the initial joint line 131 under the variable load condition.

[0093]

Mathematical formula 2

[0094]

[0095] Based on the fatigue life of each initial joint line 131 calculated in this way, the target fatigue life setting unit 18 sets the target fatigue life of the joint line optimization analysis model 151. The target fatigue life is a fatigue life that the candidate joint line 155 (described later) remaining after the optimization analysis should satisfy. In the first embodiment, the target fatigue life is set to be at least the fatigue life of the shortest fatigue life (shortest fatigue life) among the initial joint lines 131 calculated by the target fatigue life setting unit 18.

[0096] exist Fig. 9 The rear subframe model 111 is provided with Figure 7 The variable load conditions and Figure 51 is an example of the positions of three initial joining lines 131 from the shortest fatigue life among the fatigue lives of the initial joining lines 131 obtained as a result of the stress analysis of the constraint conditions shown and the results of their fatigue lives.

[0097] Fig. 9 The fatigue life of the initial joint line 131 shown is calculated under the following variable load conditions: in the rear subframe model 111, the mounting sleeves a~d mounted on the vehicle body are fully constrained, the tire input point 100 on the right side of the vehicle body is set as the load input point A, and 1 cycle of the first vibration mode in which the variable load of ±2.5kN is input in the forward and backward directions (input 1) and 5 cycles of the second vibration mode in which the variable load of ±6.0kN is input in the inner and outer directions (input 2) are combined to be set as 1 sequence.

[0098] The fatigue life calculated for the initial joint line 131 of the rear subframe model 111 is as follows: Fig. 9 As shown in FIG. 1 , the joints between the side frame lower member 113 and the bracket 122 are 44000 series and 53000 series, and the joint between the side frame upper member 112 and the bracket 120 is 64000 series, which are three joint lines from the side with the shorter fatigue life. Based on this result, the target fatigue life setting unit 18 sets the fatigue life above the 44000 series of the initial joint line 131 where the side frame lower member 113 and the bracket 122 are joined as the target fatigue life.

[0099] In the calculation of the fatigue life by the target fatigue life setting unit 18, as described above, commercially available fatigue life prediction analysis software may be used. For example, when the fatigue life of the initial joint line 131 modeled as a plane element is calculated using commercially available fatigue life prediction analysis software, the fatigue life of the initial joint line 131 can be calculated by inputting conditions such as the stress of the initial joint line 131 into the fatigue life prediction analysis software. As the stress of the initial joint line 131, the stress value of the plane element of each component model connected to the plane element of the initial joint line 131, or the nominal structure stress (nominal structure stress) obtained from the force and moment acting on both ends of the plane element of the initial joint line 131 can be used.

[0100] In addition, the SN diagram may change depending on the load state (for example, even if the stress amplitude is the same, it depends on whether the average stress is compressive stress or tensile stress, etc.), but you can refer to the values ​​of fatigue life prediction analysis software or experimental values. Alternatively, when using nominal structural stress to calculate fatigue life, you can also use an SN diagram that includes different load states. In addition, if Figure 8As shown, the SN diagram can also be expressed on the low stress side by applying various rules such as Miner's rule that does not judge fracture below the fatigue limit, and modified Miner's rule that counts it as damage even below the fatigue limit.

[0101] (Component Rigidity Sensitivity Analysis Section)

[0102] The component rigidity sensitivity analysis unit 19 sets an objective function related to the rigidity performance of the joint line optimization analysis model 151, constraints related to the volume of the component model constituting the joint line optimization analysis model 151, and variable load conditions provided to the joint line optimization analysis model 151, and performs sensitivity analysis of the component model constituting the joint line optimization analysis model 151 that satisfies the objective function under the variable load conditions and the constraints, and selects a rigidity low-sensitivity component model with low sensitivity to the rigidity performance based on the sensitivity of the component model.

[0103] In the first embodiment, as objective functions related to the rigidity performance set by the component rigidity sensitivity analysis unit 19, there are, for example, minimization of the sum of strain energy, minimization of displacement, minimization of maximum principal stress, maximization of rigidity, etc. in the component model constituting the weld line optimization analysis model 151. In addition, as constraint conditions set by the component rigidity sensitivity analysis unit 19, there are, for example, a volume constraint ratio that specifies the volume ratio of the component model constituting the weld line optimization analysis model 151. In addition, as a variable load condition provided to the weld line optimization analysis model 151, the component rigidity sensitivity analysis unit 19 sets, for example, Figure 5 (a) and Figure 5(b) shows the variable load conditions (input 1, input 2) and constraint conditions. Moreover, the component rigidity sensitivity analysis unit 19 uses the density method in topology optimization to calculate the density (density) (element density) of each element (mesh model of plane elements) of the component model of the joint line optimization analysis model 151 calculated by the topology optimization as sensitivity. The element density is an imaginary density representing the filling state of the material in each element, and takes a value of 0 to 1. That is, if the element density is 1, it means that the element is completely filled with material. If the element density is 0, it means that the element is completely empty without material. If the element density is an intermediate value between 0 and 1, it means that it is impossible to determine whether the element is a material or a void. In addition, among the element density calculated by topology optimization, if it is an element that contributes greatly to the rigidity performance, the element density becomes a value close to 1, indicating that the sensitivity to the rigidity performance is high. In contrast, if the element has a small contribution to the rigidity performance, the element sensitivity becomes a value close to 0, indicating that the sensitivity to the rigidity performance is small. In this way, the element density calculated by topology optimization becomes an index representing the sensitivity of each element to the rigidity performance.

[0104] As an example of sensitivity analysis of the component model constituting the weld line optimization analysis model 151 calculated by the component rigidity sensitivity analysis unit 19, as an objective function related to rigidity performance, the minimization of the sum of strain energy in the component model constituting the weld line optimization analysis model 151 is set, as a constraint condition, the volume constraint rate of the component model constituting the weld line optimization analysis model 151 is set to 50%, and as a variable load condition provided to the weld line optimization analysis model 151, Figure 5 (a) and Figure 5 The density method in topology optimization is used to calculate the density (element density) of the component model constituting the joint line optimization analytical model 151 calculated by the topology optimization using the variable load conditions (input 1, input 2) and constraint conditions shown in (b). Fig.10 An example of the result of the element density of the welding line optimization analysis model 151 is shown in FIG. Fig.10 (a) is the result of the variable load condition (input 1), Fig.10(b) is the result of the variable load condition (input 2). In the sensitivity analysis of the variable load condition (input 1), it is known that the element density of the beam upper part 116, the beam lower part 117 and the bracket 122 is less than 0.5, and the sensitivity is low. In addition, in the sensitivity analysis of the variable load condition (input 2), it is known that the beam front part 118 and the beam rear part 119 are also low in sensitivity. Therefore, in this example, in the sensitivity analysis results, the component whose total area of ​​elements with an element density of less than 0.5 occupies more than 50% of the surface area of ​​the entire component is selected as a rigid low-sensitivity component model. As a result, the component models of the beam upper part 116, the beam lower part 117, the bracket 122, the beam front part 118 and the beam rear part 119 are selected as rigid low-sensitivity component models.

[0105] (Joint line and component shape optimization analysis model generation department)

[0106] The weld line and component shape optimization analytical model generation unit 20 generates a weld line and component shape optimization analytical model 156 (refer to FIG. 1 ) which is set with the weld candidate line 155 of the weld line optimization analytical model 151 and the plane elements constituting the rigidity low-sensitivity component model (the component models of the beam upper member 116, the beam lower member 117, the bracket 122, the beam front member 118, and the beam rear member 119) as the design space. Fig.11 ).

[0107] (Optimization analysis condition setting section)

[0108] In order to perform optimization analysis with the joint line·component shape optimization analysis model 156 as the object of optimization, the optimization analysis condition setting unit 21 calculates the number of fracture repetitions near each joint candidate line 155 for the load conditions of each vibration mode set by the variable load condition setting unit 17, and calculates the ratio of the number of cycles of the load conditions of each vibration mode to the number of fracture repetitions, and the sum of the sequence numbers of the variable load conditions set by the target fatigue life setting unit 18 as the cumulative damage degree DM of the said each joint candidate line 155, and sets the conditions related to the cumulative damage degree of the joint candidate line 155 remaining after the optimization analysis, the conditions related to the rigidity of the joint line·component shape optimization analysis model 156, and the conditions related to the length of the joint candidate line 155 remaining after the optimization analysis as the objective function or constraint conditions of the optimization analysis conditions, and sets the constraint conditions related to the volume ratio of the rigidity low sensitivity component model.

[0109] There are two types of optimization analysis conditions: objective function and constraint conditions. Only one objective function is set according to the purpose of optimization analysis. As objective functions, conditions related to rigidity, conditions related to fatigue life, and conditions related to joining length can be cited.

[0110] As a condition related to rigidity, for example, it is preferable to set a predetermined position in the analytical object model as a rigidity evaluation point, and set the displacement or strain of the rigidity evaluation point as an index. Furthermore, in the variable load condition, for example, the minimum of the value obtained by adding the displacement of the rigidity evaluation point A in the load condition of each vibration mode or the minimum of the displacement of the rigidity evaluation point A in the load condition of each vibration mode can be set as a condition related to rigidity. As a condition related to fatigue life, it is sufficient to set a condition greater than the target fatigue life set by the target fatigue life setting unit 18. In addition, regarding the joint length, for example, it is sufficient to set a ratio relative to the total joint length.

[0111] The constraint condition is a constraint imposed when performing optimization analysis, and a plurality of constraints may be set as necessary.

[0112] In the first embodiment, it is preferable to set the condition that the fatigue life of the candidate joint line 155 is greater than the target fatigue life set by the target fatigue life setting unit 18 as the constraint condition. The number of fracture repetitions of the candidate joint line 155 is the same as the number of fracture repetitions of the initial joint line 131 under the variable load condition described above, and can be used. Figure 8 It is calculated based on the SN diagram shown.

[0113] Regarding the conditions related to fatigue life, it is not limited to directly providing the target fatigue life set by the target fatigue life setting unit 18 as a constraint condition. A constraint condition can also be provided so that the cumulative damage degree DM of the sequence number of the target fatigue life set by the target fatigue life setting unit 18 of the joining candidate line 155 under the variable load condition becomes a cumulative damage degree DM<1 that does not cause fatigue failure.

[0114] The cumulative damage degree DM of the candidate joining line 155 can be calculated by, for example, using the stress of the plane element of the component model connected to the plane element modeled as the candidate joining line 155, the nominal structural stress calculated from the force and moment acting on both ends of the plane element, and the like. Figure 8 It is calculated using the SN diagram shown and equation (2).

[0115] In addition, regarding the condition related to the length of the candidate joining line 155, the length of the remaining candidate joining line 155 can be set to a predetermined value. In the first embodiment, a constraint condition is set to make the length of the remaining candidate joining line 155 less than the length of the initial joining line 131. In addition, a constraint condition is set to make the length of the candidate joining line 155 greater than 30 mm so as to avoid each candidate joining line 155 from being finely cut.

[0116] Regarding the optimization analysis condition related to the line length of the candidate joining line 155, when the density method is applied in the topology optimization in the optimization analysis of the optimization analysis unit 23, the volume of the candidate joining line 155 calculated based on the density of the element (plane element, three-dimensional element, etc.) modeled as the candidate joining line 155 can also be provided as a constraint condition. In addition, regarding the constraint condition related to the volume ratio of the rigid low-sensitivity component, the volume ratio of the remaining rigid low-sensitivity component can be set to a specified value. In the present embodiment 1, a constraint condition is set to make the volume ratio of the remaining rigid low-sensitivity components (the upper beam part 116, the lower beam part 117, the bracket 122, the front beam part 118, and the rear beam part 119) less than 50%.

[0117] (Optimization and Analysis Department)

[0118] The optimization analysis unit 23 provides the variable load conditions set by the variable load condition setting unit 17 to the optimization analysis model, performs optimization analysis under the optimization analysis conditions, and obtains the configuration of the joining candidate line 155 that achieves any one of the following objectives: reducing the cumulative damage degree of the joining candidate line 155, improving the rigidity of the optimization analysis model, and minimizing the length of the remaining joining candidate line 155, and obtains the residual shape of the rigidity low-sensitivity component as the optimal shape of the component model with low sensitivity to rigidity performance.

[0119] Topology optimization can be applied as the optimization analysis of the optimization analysis unit 23. When the density method is used in the topology optimization, for the elements (plane elements, three-dimensional elements, etc.) modeled as the joint candidate lines 155, the normalized virtual density taking the value of 0 to 1 is given as a design variable, and the value of the density that satisfies the optimization analysis conditions is calculated.

[0120] Furthermore, if the calculated density value is 1, the joining candidate line 155 is in a completely existing state; if the calculated density value is 0, the joining candidate line 155 does not exist; and if the calculated density value is an intermediate value, the joining of the joining candidate line 155 to the component group is in an intermediate state.

[0121] Therefore, when there are many intermediate densities when applying the density method in topology optimization, it is preferable to discretize using a penalty coefficient as shown in Formula (3).

[0122]

Mathematical formula 3

[0123]

[0124] In discretization, the penalty coefficient is usually 2 or more, but in the optimization analysis of the joining position according to the present invention, the penalty coefficient is preferably 4 or more.

[0125] The optimization analysis unit 23 may perform optimization analysis based on topology optimization as described above, or may perform optimization analysis based on other calculation methods.

[0126] exist Fig.11 The figure shows the element density distribution of the candidate joining line 155 and the rigid low-sensitivity component model (component models of the upper beam part 116, the lower beam part 117, the bracket 122, the front beam part 118 and the rear beam part 119) obtained by the optimization analysis unit 23 in the topology optimization by applying the density method. In the rigid low-sensitivity component model, the part with low element density can be punched and thinned for the purpose of weight reduction. For example, the element density of 0.40 is set as a threshold, and the element density below 0.40 is judged as an unnecessary part, and punching and thinning based on TWB (tailor welded blank) are performed. Fig.12 An example of the shape of such a lightweight component is shown in FIG. Fig.12 In the example shown, holes H are provided in the upper crossbeam member 116, the lower crossbeam member 117, the front crossbeam member 118, and the rear crossbeam member 119, and the bracket 122 is thinned based on TWB. TWB (tailor-welded blank) refers to a component obtained by laser joining raw materials with different plate thicknesses. In this example, the plate thickness of the original component of 2.6 mm is reduced to 1.0 mm. By such lightweighting, as shown in the embodiment described later, the weight of the original component of 16.2 kg can be reduced by 650 g to 15.5 kg (4.0% weight reduction). The effect of the optimal configuration of the joining line obtained in this embodiment 1 is described in the embodiment described later.

[0127] <Analysis method for optimizing the joint position of the vehicle body>

[0128] The first embodiment of the present invention relates to an optimization analysis method for the joining position of a vehicle body (hereinafter referred to as "optimization analysis method"), in which a computer executes the following steps for all or part of a vehicle body model having a plurality of component models composed of beam elements and plane elements and having an initial joining line 131 where the plurality of component models are joined as a component group, to perform optimization analysis to find the best configuration of the joining line to achieve any one of the following goals: improving the rigidity of the vehicle body model, improving the fatigue life near the joining line where the component group in the vehicle body model is joined, or minimizing the length of the joining line. Fig.13As shown, the optimization analysis method includes an analysis object model setting step S1, a joint line optimization analysis model generation step S3, a variable load condition setting step S5, a target fatigue life setting step S6, a component rigidity sensitivity analysis step S7, a joint line·component shape optimization analysis model generation step S8, an optimization analysis condition setting step S9, and an optimization analysis step S11. The following is an explanation of each of these steps. The following steps are performed by an optimization analysis device 1 ( Figure 1 ).

[0129] ≪Analysis object model setting steps≫

[0130] The analysis target model setting step S1 sets all or part of the vehicle body model as the analysis target model.

[0131] In the first embodiment, in the analysis target model setting step S1 , the analysis target model setting unit 13 sets the rear subframe model 111 , which is a part of the vehicle body model, as the analysis target model.

[0132] ≪Joint line optimization analysis model generation steps≫

[0133] The welding line optimization analysis model generation step S3 sets all the candidate welding lines 155 that are candidates for the welding lines with the best arrangement to the analysis target model, and generates the welding line optimization analysis model.

[0134] In the first embodiment, in the joint line optimization analytical model generation step S3 , the joint line optimization analytical model generation unit 15 generates additional joint lines 153 between the initial joint lines 131 preset for the rear subframe model 111 , and sets both the initial joint lines 131 and the additional joint lines 153 as candidate joint lines 155 .

[0135] ≪Steps for setting variable load conditions≫

[0136] The variable load condition setting step S5 divides the variable load provided to the weld line optimization analysis model 151 into load conditions of a plurality of different vibration modes, and sets a variable load condition that combines the load conditions of the vibration modes in a predetermined number of cycles to form one sequence.

[0137] In the first embodiment, in the variable load condition setting step S5, the variable load condition setting unit 17 of the optimization analysis device 1 sets Figure 5 The load conditions of the first vibration mode shown in (a) are 1 cycle and Figure 5 The load condition of the second vibration mode shown in (b) is combined into 5 cycles and set as one series of variable load conditions (refer to Figure 7 ), and, if Figure 5 As shown, set the constraint conditions for constraining the constraint points a to d.

[0138] ≪Steps for setting target fatigue life≫

[0139] The target fatigue life setting step S6 sets the target fatigue life of the joint line optimization analysis model 151 with the sequence number of the variable load condition set in the variable load condition setting step S5. As the target fatigue life of the joint line optimization analysis model 151, the load condition of the vibration mode among the variable load conditions set in the variable load condition setting step S5 may be provided to the analysis target model and stress analysis may be performed separately. The sequence number of the variable load condition that becomes the fatigue life under the variable load condition of the initial joint line 131 of the analysis target model may be calculated using the result of the stress analysis. The sequence number of the variable load condition that becomes the target fatigue life may be set based on the calculated sequence number of the variable load condition that becomes the fatigue life of the initial joint line 131. Alternatively, the sequence number of the variable load condition that becomes a predetermined target fatigue life may be set based on a conventional empirical rule.

[0140] The target fatigue life is the fatigue life that the candidate joining line 155 to be optimized should satisfy, and at least the number of sequences of the variable load conditions that become the shortest fatigue life (shortest fatigue life) of each initial joining line 131 calculated in the target fatigue life setting step S6 is set as the target fatigue life.

[0141] ≪Part Rigidity Sensitivity Analysis Procedure≫

[0142] The component rigidity sensitivity analysis step S7 is the following step: setting an objective function related to the rigidity performance for the joint line optimization analysis model 151, performing sensitivity analysis of the component model constituting the joint line optimization analysis model 151 relative to the variable load condition, and selecting a rigidity low-sensitivity component model with low sensitivity to the rigidity performance based on the sensitivity of the component model.

[0143] ≪Joint Line and Part Shape Optimization Analysis Model Creation Procedure≫

[0144] The weld line and component shape optimization analysis model generation step S8 is a step of generating a weld line and component shape optimization analysis model 156 in which the weld candidate lines 155 of the weld line optimization analysis model 151 and the plane elements constituting the rigidity low sensitivity component model are set as design spaces.

[0145] ≪Optimize the analysis condition setting steps≫

[0146] The optimization analysis condition setting step S9 is the following step: in order to perform an optimization analysis with the joint line / component shape optimization analysis model 156 as the object of optimization, the number of fracture repetitions of each joint candidate line 155 is calculated for the load conditions of different multiple vibration modes in the variable load condition setting step S5, and the sum of the sequence numbers of the variable load conditions set by the target fatigue life setting step S6, which is the ratio of the number of cycles of the load conditions of each vibration mode to the number of fracture repetitions, is calculated as the cumulative damage degree DM of each joint candidate line 155, and the conditions related to the cumulative damage degree of the joint candidate line 155 remaining after the optimization analysis, the conditions related to the rigidity of the joint line optimization analysis model 151, and the conditions related to the length of the joint candidate line 155 remaining after the optimization analysis are set as the objective function or constraint conditions as the optimization analysis conditions, and the constraint conditions related to the volume ratio of the rigid low-sensitivity component model are set.

[0147] In the first embodiment, in the optimization analysis condition setting step S9, the optimization analysis condition setting unit 21 sets the maximization of the rigidity of the joining line / component shape optimization analysis model 156 (minimization of the displacement of the rigidity evaluation point A) as the objective function, and sets the constraint condition that the fatigue life of the joining candidate line 155 is greater than the target fatigue life, the constraint condition that the length of the remaining joining candidate line 155 is less than the length of the initial joining line 131 and the length of each joining candidate line 155 is more than 30 mm, and the constraint condition that the volume ratio of the remaining rigid low-sensitivity component model is less than 50% as the optimization analysis conditions.

[0148] As a condition related to rigidity, for example, it is preferable to set a predetermined position in the analysis target model as a rigidity evaluation point and set the displacement or strain of the rigidity evaluation point as an index. Furthermore, in the variable load condition, for example, the variable load is divided into each vibration mode and the displacement of the rigidity evaluation point A in the load condition of each vibration mode is minimized, or the displacement of the rigidity evaluation point A under the variable load condition is minimized as a condition related to rigidity.

[0149] In addition, as a condition related to fatigue life, it is not limited to providing the target fatigue life set in the target fatigue life setting step S6 directly as a constraint condition. For example, a constraint condition that makes the cumulative damage degree DM of the joining candidate line 155 less than the cumulative damage degree equivalent to the target fatigue life can also be provided.

[0150] ≪Optimize the parsing steps≫

[0151] The optimization analysis step S11 provides the variable load condition set in the variable load condition setting step S5 to the bonding line·component shape optimization analysis model 156, performs optimization analysis under the optimization analysis condition, and obtains the configuration of the bonding candidate line 155 that is achieved by reducing the cumulative damage degree of the bonding candidate line 155, improving the rigidity of the bonding line·component shape optimization analysis model 156, and minimizing the length of the remaining bonding candidate line 155 as the purpose, and obtains the residual shape of the rigidity low-sensitivity component model as the optimal shape of the component model with low sensitivity to rigidity performance.

[0152] In the first embodiment, in the optimization analysis step S11, the optimization analysis unit 23 sets the candidate joining line 155 set for the rear subframe model 111 and the rigidity low-sensitivity component model (the component model of the cross beam upper member 116, the cross beam lower member 117, the bracket 122, the cross beam front member 118, and the cross beam rear member 119) as the optimization object and performs optimization analysis, and obtains the configuration of the candidate joining line 155 that satisfies the optimization analysis conditions as the optimal configuration of the joining line 157, sets a hole H in the cross beam upper member 116, the cross beam lower member 117, the cross beam front member 118, and the cross beam rear member 119, and thins the bracket 122 by TWB ( Fig.12 ).

[0153] <Analysis program for optimizing the joint position of the vehicle body>

[0154] Embodiment 1 of the present invention can be configured as an optimization analysis program for the joint positions of a vehicle body that enables various parts of the optimization analysis device 1 for the joint positions of a vehicle body constituted by a computer to function. That is, the optimization analysis program for the joint positions of a vehicle body involved in embodiment 1 of the present invention sets all or part of a vehicle body model as an analysis target model, and performs optimization analysis on the analysis target model to find the optimal configuration of the joint line to achieve any one of the following purposes: improving the rigidity of the vehicle body model, improving the fatigue life near the joint line where the component group in the vehicle body model is joined, and minimizing the length of the joint line, and to find the optimal shape of the component model that has low sensitivity to the rigidity performance. As in Figure 1 As shown in the figure as an example, the optimization analysis program of the joining position of the vehicle body involved in the first embodiment of the present invention enables the computer to function as an analysis object model setting unit 13, a joining line optimization analysis model generation unit 15, a variable load condition setting unit 17, a target fatigue life setting unit 18, a component rigidity sensitivity analysis unit 19, a joining line and component shape optimization analysis model generation unit 20, an optimization analysis condition setting unit 21 and an optimization analysis unit 23.

[0155] As described above, according to the method, device, and program for optimizing the joint position of the vehicle body involved in the first embodiment, the entire or a part of the vehicle body model is set as the analysis target model, and the joint line optimization analysis model 151 obtained by setting the joint candidate line 155 to be joined as the component group for the analysis target model is generated, and the optimization analysis conditions (objective function or constraint conditions) related to the remaining line length, fatigue life, and rigidity of the joint line·component shape optimization analysis model 156 of the joint candidate line 155 set as the optimization target are set to perform optimization analysis on the joint candidate line 155, thereby, when a variable load whose amplitude, direction, etc. changes with the passage of time is input to the vehicle body, the optimal arrangement of the joint line that is achieved with the purpose of minimizing the length of the joint candidate line 155, improving the rigidity of the analysis target model, and improving the fatigue life of the joint line that joins the component group can be obtained, and at the same time, the weight reduction of the component that does not contribute to the rigidity improvement can be achieved. In this way, by setting the joint line and the component shape as the optimization target at the same time, the optimization of both parties (joint line and component shape) that affect each other can be achieved efficiently.

[0156] In the above description, a vehicle body model obtained by modeling the entire vehicle body is obtained, and the rear subframe model 111, which is a part of the vehicle body model, is set as the analysis target model. However, the present invention may set the entire vehicle body model as the analysis target model, or may set a part of the vehicle body model other than the rear subframe model 111 as the analysis target model. In addition, a vehicle body partial model, which is a part of the vehicle body model, may be obtained, and the obtained vehicle body partial model may be set as the analysis target model.

[0157] In addition, the above description takes as an example the case where the initial joint line 131 in the rear subframe mold 111 is set to 6540 mm in advance, but the length of the initial joint line 131 is not limited to this.

[0158] The initial joint line 131 is a joint line that is preset by an operator or other means in the rear subframe model 111. However, the present invention may also allow an operator to newly set an initial joint line 131 by using the analysis target model setting unit or in the analysis target model setting step, or to set an initial joint line 131 by adding to the analysis target model that has already been set with the initial joint line 131.

[0159] In the first embodiment, the rear subframe model 111 is set Figure 5 The load conditions and constraint conditions shown in the figure are as follows. However, the present invention assumes that the variable load conditions and constraint conditions will act on the part of the vehicle body set as the analysis object or the actual vehicle body, and may appropriately set the variable load conditions and constraint conditions.

[0160] In the example of the first embodiment, the target performance of the fatigue life of the candidate joining line 155 is set based on the shortest fatigue life (shortest fatigue life) of the initial joining line 131 set for the analysis target model.

[0161] However, the present invention preferably calculates and sets the additional bonding line 153 (see Figure 6 ) and the fatigue life of the candidate joining line 155 in the joining line optimization analysis model 151 obtained by the calculation, determine the shortest fatigue life among the calculated fatigue lives of the candidate joining line 155, and set the target fatigue life in the optimization analysis in a manner that satisfies the following relationship.

[0162] (The shortest fatigue life of the initial bonding line) ≤ (the target fatigue life of the bonding candidate line) ≤ (the shortest fatigue life of the bonding candidate line for which the bonding line before the optimization analysis is set)

[0163] Moreover, the above description sets both the initial joining line 131 and the additional joining line 153 as the candidate joining line 155 for optimization analysis, but it is also possible to set only the additional joining line 153 as the candidate joining line 155, without setting the initial joining line 131 as the object of optimization analysis, and find the optimal configuration of the joining line added to the initial joining line 131.

[0164] Furthermore, if the optimization analysis is performed by setting the initial weld line 131 to be included in the candidate weld line 155, the candidate weld line 155 that is joined as a component group disappears during the optimization analysis, and the component group becomes scattered, and sometimes the optimization analysis cannot be performed. In such a case, it is preferable to set at least one fixed weld line that is not the object of the optimization analysis in each component group.

[0165] For example, a fixed weld line can be arbitrarily selected from the initial weld lines 131, or a candidate fixed weld line can be set as a candidate for the fixed weld line and stress analysis or optimization analysis of the analysis object model can be performed, and the fixed weld line can be selected from the candidate fixed weld lines based on the results.

[0166] In the above description, the fatigue life of the candidate joining line 155 or the rigidity of the joining line optimization analysis model 151 is set as the objective function, but the line length of the candidate joining line 155 may be set as the objective function, and the fatigue life and rigidity may be set as constraints.

[0167] [Implementation Method 2]

[0168] The above-mentioned method for optimizing the joint position of the vehicle body according to the first embodiment performs optimization analysis to obtain the optimal arrangement of the joint line for the purpose of improving the rigidity of the vehicle body model having the initial joint line 131 for joining a plurality of component models as a component group, improving the fatigue life of the joint line for joining the component group in the vehicle body model, and minimizing the length of the joint line. However, the present invention can be configured as a method for manufacturing a vehicle body in which the rigidity of the vehicle body and the fatigue life of the joint line are improved by optimally arranging the joint line for joining the component group in the vehicle body.

[0169] In the manufacturing method of the vehicle body involved in the present embodiment 2, the optimization analysis method of the joining position of the vehicle body involved in the aforementioned embodiment 1 is used to obtain the optimal configuration of the joining lines for all or part of the vehicle body model having an initial joining line in which a plurality of component models are joined as a component group. Furthermore, in the manufacturing method of the vehicle body involved in the present embodiment 2, the optimal shape of a component model with low sensitivity to rigidity performance (rigidity low sensitivity component model) is obtained. Then, the shape of the corresponding vehicle body component is changed based on the optimal shape of the rigidity low sensitivity component model. Furthermore, the joining position of the component group in the vehicle body is determined based on the obtained optimal configuration of the joining lines of the vehicle body model. Then, the component group of the vehicle body is joined at the determined joining position. As a scheme for changing the shape of the corresponding vehicle body component based on the optimal shape of the rigidity low sensitivity component model, the following scheme can be exemplified.

[0170] When the density method of topology optimization is used in the optimization analysis, the residual shape after removing (so-called weight reduction) the unnecessary parts below a predetermined threshold value (e.g., an element density of 0.4) in the element density distribution from the component model with low sensitivity to the rigid performance of the vehicle body (rigid low-sensitivity component model) is the optimal shape of the rigid low-sensitivity component model. As a specific example of a scheme for changing the shape of a body part, the three-dimensional position data of the unnecessary parts in the rigid low-sensitivity component model is input into a CAD / CAM program, and CAD processing such as smoothing and shape optimization processing is performed in accordance with the constraints during the manufacture of the actual body part to change the CAD data of the corresponding body part. The CAD data of the stamping die is produced based on the CAD data of the changed body part, and the stamping die is produced based on the CAD data of the produced stamping die. Then, the produced stamping die is used to change the shape by stamping to produce a lightweight body part.

[0171] As a scheme for making a stamping die, the following scheme can be exemplified. Among the stamping dies, there are stamping dies made of castings and stamping dies made of steel. In the case of a stamping die made of castings, a solid casting method (lost foam casting method) is used to make a casting die model from a material that disappears at high temperatures such as foamed polystyrene by using NC processing of an NC machine tool. In addition, in the case of a stamping die made of steel, it is necessary to machine the steel (cutting, grinding, grinding) by NC processing. The CAD data of the stamping die made based on the CAD data of the changed body parts is input into a CAD / CAM program that cooperates with an NC machine tool and converted into NC data (NC program) for NC processing. The NC machine tool performs machining on a casting die model made of foamed polystyrene or a steel die. Then, using the obtained NC data (NC program), a casting die model made of foamed polystyrene or a steel die is made using an NC machine tool to make an actual stamping die.

[0172] As a scheme for determining the joining position of a component group in a car body, the following scheme can be exemplified. As a specific example of the scheme for determining the joining position, the position data of the three-dimensional coordinates of the optimal configuration of the joining line of the car body model obtained by using the optimization analysis method of the joining position of the car body is input into a CAD / CAM program that cooperates with the NC unit of the welding robot configured in the car body welding process, and is converted into NC data (NC program) for the welding robot. In addition, as a specific example of the scheme for joining the component group in the car body, the welding robot configured in the car body welding process is operated by using the converted NC data, so that the component group of the car body is joined at the determined joining position. In this way, according to the manufacturing method of the car body involved in this embodiment 2, it is possible to achieve the optimal configuration of the welding position of arc welding and the like in the car body structure, improve the fatigue life near the joining line, and improve the rigidity of the car body, and it is possible to achieve a reduction in welding costs and a high rigidity and light weight of the car body.

[0173] Example

[0174] Since an analysis was performed to confirm the effect of the present invention, the analysis will be described below. Fig.14 As shown, the rear sub-frame model 111 obtained by modeling the rear sub-frame is taken as an object, and the optimal arrangement of the joining lines for joining the component models constituting the rear sub-frame model 111 as a component group is obtained by optimization analysis.

[0175] In the rear sub-frame model 111, as described in Embodiment 1, as component models, the side frame upper member 112 and the side frame lower member 113 are joined by arc welding to form the side frame R211. The side frame upper member 114 and the side frame lower member 115 are joined by arc welding to form the side frame L212. The cross beam upper member 116 and the cross beam lower member 117 are joined by arc welding to form the cross beam front member 213. The cross beam front member 118 and the cross beam rear member 119 are joined by arc welding to form the rear cross beam 214. These side frames R211, side frames L212, cross beam front member 213 and rear cross beam 214 are further joined by arc welding to form a tic-tac-toe structure. These component models are modeled as plane elements.

[0176] The rear subframe model 111 is previously set with an initial joining line 131 for joining the component models as a component group. The initial joining line 131 is modeled as a plane element connecting the nodes of the plane elements of the component models, and the length of the initial joining line 131 is 6540 mm.

[0177] <Invention Example>

[0178] In the invention example, first, based on Figure 7 The target fatigue life is set based on the fatigue life of the initial bond line 131 under the varying load conditions shown.

[0179] Figure 7 The variable load conditions shown are set as the load conditions of the first vibration mode where a variable load of ±2.5 kN is input in the forward and backward directions (input 1) (refer to Figure 5 (a)) The conditions of the second vibration mode where a variable load of ±6.0 kN is input in the inner and outer directions (input 2) (refer to Figure 5 (b)). In addition, regarding the variable load condition, one cycle of the load condition of the first vibration mode and five cycles of the load condition of the second vibration mode are combined to form one sequence of variable load conditions.

[0180] Next, for the load condition of the first vibration mode ( Figure 5 (a)) and the load condition of the second vibration mode ( Figure 5 (b)) stress analysis of the rear subframe model 111 was performed to obtain stress generated at the initial joint line 131 under the load conditions of each vibration mode.

[0181] Next, according to the SN line diagram ( Figure 8 ) and the number of repetitions N1 and N2 until the initial bonding line 131 breaks when different stress amplitudes σ1 and σ2 are generated at the initial bonding line 131 under the variable load condition are obtained.

[0182] 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 conditions of the first vibration mode and the load conditions of the second vibration mode in the variable load conditions of the 1st sequence are substituted into formula (1) to calculate the cumulative damage degree dm in the 1st sequence.

[0183] The sequence number K when the cumulative damage degree DM calculated using equation (2) becomes greater than 1 is calculated as the fatigue life of the initial joint line 131 under the variable load condition, and the target fatigue life is set based on the shortest fatigue life among the fatigue lives of the initial joint lines 131.

[0184] Then, if Figure 6 As shown, additional joint lines 153 are set between the initial joint lines 131 in the rear subframe model 111 , and a joint line optimization analysis model 151 is generated in which the initial joint lines 131 and the additional joint lines 153 are set as joint candidate lines 155 .

[0185] Then, an objective function related to the rigidity performance of the welding line optimization analysis model 151, constraints related to the volume of the component model constituting the welding line optimization analysis model 151, and variable load conditions provided to the welding line optimization analysis model 151 are set, and sensitivity analysis of the component model constituting the welding line optimization analysis model 151 that satisfies the objective function is performed under the variable load conditions and constraints, and a rigid low-sensitivity component model with low sensitivity to the rigidity performance is selected based on the sensitivity of the component model.

[0186] Specifically, as shown in the first embodiment, the total amount of strain energy in the component model constituting the weld line optimization analysis model 151 is minimized, and the volume constraint rate of the component model constituting the weld line optimization analysis model 151 is set to 50% as a constraint condition, and the variable load condition provided to the weld line optimization analysis model 151 is set to Figure 5 (a) and Figure 5 The density method in topology optimization is used to calculate the density (element density) of the component model constituting the joint line optimization analysis model 151 calculated by the topology optimization under the variable load conditions (input 1, input 2) and constraint conditions shown in (b) of FIG. 15A . As a result of the sensitivity analysis, the component whose total area of ​​elements with an element density of 0.5 or less occupies more than 50% of the surface area of ​​the entire component is selected as a rigid low-sensitivity component model. As a result, the component models of the beam upper part 116, the beam lower part 117, the bracket 122, the beam front part 118, and the beam rear part 119 are selected as rigid low-sensitivity component models.

[0187] Then, a joint line and component shape optimization analysis model 156 is generated, which is set as a design space using the planar elements of the joint candidate line 155 and the rigidity low-sensitivity component model (component models of the beam upper member 116, beam lower member 117, bracket 122, beam front member 118, and beam rear member 119) constituting the joint line optimization analysis model 151. In the example of the invention, this joint line and component shape optimization analysis model 156 is set as the object of optimization.

[0188] <Comparative Example>

[0189] In the comparative example, the component shape is not optimized, and therefore the aforementioned weld line optimization analysis model 151 is optimized.

[0190] Next, the invention examples and comparative examples are provided. Figure 5 The optimization analysis was performed based on the load conditions and constraint conditions shown in the figure, and the candidate joining line 155 satisfying the optimization analysis conditions was obtained. In the optimization analysis, topology optimization based on the density method was applied, and the penalty coefficient was set to 4 in the topology optimization to perform discretization.

[0191] Table 1 shows combinations of objective functions and constraint functions for optimizing analytical conditions.

[0192]

[0193] The objective function related to rigidity is set so that the rigidity evaluation point A (refer to Fig.14 ) is an objective function equal to or less than the displacement of the rigidity evaluation point A when stress analysis is performed on the rear subframe model 111 in which the initial joint line 131 is set.

[0194] In addition, regarding the constraint conditions related to fatigue life, the cumulative damage degree DM of the candidate joint line 155 under the variable load condition is calculated in the same manner as the initial joint line 131 described above. Then, a constraint condition is set so that the fatigue life calculated based on the cumulative damage degree DM of each candidate joint line 155 is greater than the target fatigue life. Moreover, the objective function and constraint conditions related to the length of the candidate joint line 155, that is, the joint length, are set so that the length of the candidate joint line 155 remaining after the optimization analysis is less than the length of the initial joint line 131. The constraint condition of the component shape in the invention example is to make the volume ratio of the rigid low-sensitivity component less than 50%.

[0195] exist Fig.15 The results of the remaining candidate joining line 155 and the component shape in the invention example are shown in FIG. Fig.16 The result of the remaining candidate joining line 155 in the comparative example is shown in FIG. Fig.15 In the same way as above, Fig.12 In the example shown, a portion of a low-sensitivity component having a low element density is shown as an open hole shape.

[0196] In the invention example, Fig.15 As shown, at the joints between the bracket 121 and the side frame upper member 112, the joints between the cross beam front member 118 and the cross beam rear member 119, and the joints between the cross beam front member 118 and the side frame lower member 113 (in Fig.15 The bonding wires are sparsely arranged in the area indicated by the black arrow in (b).

[0197] In contrast, in the comparative example, Fig.16 As shown in FIG. 1 , the welding wires are densely arranged around the brackets 120, 121, and 122, and are also densely arranged in other locations as compared with the overall invention example. Specifically, as shown in Table 2 described later, the welding length (weld length) (length of the welding wire) of the comparative example is 6340 mm, while the welding length (length of the welding wire) of the invention example is 6040 mm.

[0198] Next, in order to evaluate the performance of the invention example and the comparative example, with respect to the invention example, the candidate joining line 155 remaining after the optimization analysis was set as the optimally arranged joining line 157 and the optimal rear subframe model 158 (refer to Fig.15 ) was taken as the object, and for the comparative example, the analytical model in which the candidate joining line 155 remaining after the optimization analysis was set was taken as the object, and the rigidity and fatigue life of the joining line were calculated.

[0199] In the calculation of rigidity and fatigue life, Figure 5 The load conditions of the first vibration mode and the load conditions of the second vibration mode and the constraint conditions shown in FIG. 1 are provided to the optimal weld line rear subframe model 161 and stress analysis is performed. Regarding rigidity, the rigidity evaluation point A (refer to FIG. 1 ) obtained by stress analysis under the load conditions of the first vibration mode and the load conditions of the second vibration mode is Figure 5 ) are set as indicators respectively.

[0200] Regarding the fatigue life, the shortest fatigue life among fatigue lives calculated using the stress of the joint line obtained by stress analysis of the optimal joint line rear subframe model 161 was set as an index.

[0201] The evaluation results are shown in Table 2. Table 2 also shows the welding length and the component weight.

[0202]

[0203] The improvement rate of stiffness in inputs 1 and 2 is calculated by the following formula.

[0204]

Mathematical formula 4

[0205]

[0206] The fatigue life of the invention example is significantly improved compared to the original part, and is roughly the same as the comparative example. In addition, regarding the rigidity improvement rate, both the invention example and the comparative example are improved compared to the original part. Moreover, regarding the component weight, the comparative example is 16.2 kg, while the invention example is 15.5 kg. The component weight of the invention example is reduced by 0.7 kg (4%) compared to the original part. In this way, it is verified that according to the present invention, the fatigue life and rigidity can be improved while reducing the welding length and component weight.

[0207] Industrial Applicability

[0208] According to the present invention, it is possible to provide an optimization analysis method, device and program for optimizing the joining position of a vehicle body, and a method for manufacturing a vehicle body, which can obtain the optimal configuration of the joining line while minimizing the length of the joining line while improving the rigidity of the vehicle body and the fatigue life of the continuous joining line that joins the component groups in the vehicle body when a simple or variable load is input to the vehicle body, and at the same time achieve lightweighting of the components that do not contribute to improving the rigidity.

[0209] Description of Reference Numerals

[0210] 1. Optimize the analysis device

[0211] 3 Display device

[0212] 5 Input Devices

[0213] 7 Storage Devices

[0214] 9 Data storage for operation

[0215] 11. Calculation processing unit

[0216] 13 Analysis object model setting section

[0217] 15 Joint line optimization analytical model generation department

[0218] 17 Variable load condition setting section

[0219] 18 Target fatigue life setting section

[0220] 19 Component Rigidity Sensitivity Analysis Department

[0221] 20 Joint line and component shape optimization analysis model generation department

[0222] 21 Optimize the analysis condition setting section

[0223] 23 Optimization Analysis Department

[0224] 31 Optimize the parsing device

[0225] 33. Calculation Processing Unit

[0226] 34 Optimization and Analysis Department

[0227] 100 Tire Input Points

[0228] 101 Car body model file

[0229] 111 Rear subframe model

[0230] 112 Side frame upper part

[0231] 113 Side frame lower part

[0232] 114 Side frame upper part

[0233] 115 frame lower part

[0234] 116 Beam upper part

[0235] 117 Beam lower part

[0236] 118 beam front piece

[0237] 119 beam rear piece

[0238] 120, 121, 122 brackets

[0239] 131 Initial bonding line

[0240] 141 Arc welding department

[0241] 151 Analytical model for optimized bonding line

[0242] 153 Additional bonding line

[0243] 155 Joining candidate line

[0244] 156 Analytical model for joint line and component shape optimization

[0245] 157 Bonding Wire

[0246] 158 Best rear subframe model

[0247] 201 Car body model

[0248] 203 Side beam

[0249] 211 Side frame R

[0250] 212 Side frame L

[0251] 213 beam front piece

[0252] 214 Rear cross member.

Claims

1. A method for optimizing and analyzing the joint position of a vehicle body, wherein a computer executes the following steps to perform optimization analysis for all or part of a vehicle body model having a plurality of component models including beam elements and plane elements and having an initial joint line for joining the plurality of component models as a component group, thereby obtaining an optimal arrangement of the joint line for the purpose of improving the rigidity of the vehicle body model, improving the fatigue life near the joint line for joining the component group in the vehicle body model, and minimizing the length of the joint line, and obtaining an optimal shape of the component model having low sensitivity to rigidity performance, in, The optimization analysis method comprises: An analysis object model setting step of setting all or part of the vehicle body model as an analysis object model; a step of generating a welding line optimization analytical model by setting all the candidate welding lines that are candidates for the welding lines of the optimal arrangement to the analysis target model; a variable load condition setting step of dividing the variable load provided to the joint line optimization analytical model into load conditions of a plurality of different vibration modes, and setting the load conditions of the vibration modes to be combined in a predetermined number of cycles to form a series of variable load conditions; a target fatigue life setting step of setting the target fatigue life of the joint line optimization analytical model according to the sequence number of the variable load condition; A component rigidity sensitivity analysis step, wherein an objective function related to the rigidity performance of the joint line optimization analysis model, a constraint condition related to the volume of the component model constituting the joint line optimization analysis model, and a variable load condition provided to the joint line optimization analysis model are set, and a sensitivity analysis of the component model constituting the joint line optimization analysis model that satisfies the objective function is performed under the variable load condition and the constraint condition, and a rigidity low-sensitivity component model having a low sensitivity to rigidity performance is selected based on the sensitivity of the component model; a step of generating a joining line and component shape optimization analytical model, wherein the joining candidate line of the joining line optimization analytical model and the plane elements constituting the rigidity low-sensitivity component model are set as a design space; an optimization analysis condition setting step, in order to perform an optimization analysis with the joint line·component shape optimization analysis model as an optimization object, the number of fracture repetitions near each joint candidate line is calculated for the load condition of each vibration mode, the total number of sequences of the variable load condition set by the target fatigue life setting step, which is the ratio of the number of cycles of the load condition of each vibration mode to the number of fracture repetitions, is calculated as the cumulative damage degree of each joint candidate line, a condition related to the cumulative damage degree of the joint candidate line remaining after the optimization analysis, a condition related to the rigidity of the joint line·component shape optimization analysis model, and a condition related to the length of the joint candidate line remaining after the optimization analysis are set as an objective function or constraint condition as an optimization analysis condition, and a constraint condition related to the volume ratio of the rigid low-sensitivity component model is set; and An optimization analysis step, providing the variable load condition set in the variable load condition setting step to the joining line and component shape optimization analysis model, performing optimization analysis under the optimization analysis condition, obtaining the configuration of the joining candidate line achieved for the purpose of reducing the cumulative damage degree of the joining candidate line, improving the rigidity of the optimization analysis model, and minimizing the length of the remaining joining candidate line as the optimal configuration of the joining line, and obtaining the residual shape of the rigidity low-sensitivity component model as the optimal shape of the component model with low sensitivity to rigidity performance.

2. The method for optimizing the joint position of a vehicle body according to claim 1, The optimization analysis step performs topology optimization based on a density method, in which a penalty coefficient is set to 4 or more for discretization.

3. An optimization analysis device for a joint position of a vehicle body, wherein a computer executes the following steps to perform optimization analysis for all or part of a vehicle body model having a plurality of component models including beam elements and plane elements and having an initial joint line for joining the plurality of component models as a component group, thereby obtaining an optimal arrangement of the joint line for the purpose of improving the rigidity of the vehicle body model, improving the fatigue life near the joint line for joining the component group in the vehicle body model, and minimizing the length of the joint line, and obtaining an optimal shape of the component model having low sensitivity to rigidity performance, in, The optimization and analysis device comprises: an analysis target model setting unit that sets all or part of the vehicle body model as an analysis target model; a joining line optimization analytical model generating unit that generates a joining line optimization analytical model by setting all candidate joining lines that are candidates for the optimally arranged joining lines for the analysis target model; a variable load condition setting unit that divides the variable load provided to the joint line optimization analytical model into load conditions of a plurality of different vibration modes, and sets a variable load condition that combines the load conditions of the vibration modes in a predetermined number of cycles to form a sequence; a target fatigue life setting unit, which sets a target fatigue life of the joint line optimization analytical model according to the sequence number of the variable load condition; a component rigidity sensitivity analysis unit, which sets an objective function related to the rigidity performance of the joint line optimization analysis model, a constraint condition related to the volume of the component model constituting the joint line optimization analysis model, and a variable load condition provided to the joint line optimization analysis model, performs sensitivity analysis of the component model constituting the joint line optimization analysis model that satisfies the objective function under the variable load condition and the constraint condition, and selects a rigidity low-sensitivity component model having a low sensitivity to rigidity performance based on the sensitivity of the component model; a joining line and component shape optimization analytical model generating unit for generating a joining line and component shape optimization analytical model in which the candidate joining line of the joining line optimization analytical model and the plane elements constituting the rigidity low-sensitivity component model are set as a design space; an optimization analysis condition setting unit, for performing optimization analysis with the joint line·component shape optimization analysis model as an optimization object, obtaining the number of fracture repetitions near each joint candidate line for the load condition of each vibration mode, obtaining the total number of sequences of the variable load condition set by the target fatigue life setting unit, which is the ratio of the number of cycles of the load condition of each vibration mode to the number of fracture repetitions, as the cumulative damage degree of each joint candidate line, setting conditions related to the cumulative damage degree of the joint candidate line remaining after the optimization analysis, conditions related to the rigidity of the joint line·component shape optimization analysis model, and conditions related to the length of the joint candidate line remaining after the optimization analysis as objective functions or constraints as optimization analysis conditions, and setting constraints related to the volume ratio of the rigid low-sensitivity component model; and An optimization analysis unit provides the variable load condition set in the variable load condition setting unit to the joining line and component shape optimization analysis model, performs optimization analysis under the optimization analysis condition, obtains the configuration of the joining candidate line achieved for the purpose of reducing the cumulative damage degree of the joining candidate line, improving the rigidity of the optimization analysis model, and minimizing the length of the remaining joining candidate line as the optimal configuration of the joining line, and obtains the residual shape of the rigidity low-sensitivity component model as the optimal shape of the component model with low sensitivity to rigidity performance.

4. The device for optimizing and analyzing the joint position of a vehicle body according to claim 3, The optimization analysis unit performs topology optimization based on a density method, and in the topology optimization, a penalty coefficient is set to 4 or more to perform discretization.

5. An optimization analysis program for a joint position of a vehicle body, which performs optimization analysis on all or part of a vehicle body model having a plurality of component models including beam elements and plane elements and having an initial joint line for joining the plurality of component models as a component group, to find an optimal arrangement of the joint line for any one of improving the rigidity of the vehicle body model, improving the fatigue life near the joint line for joining the component group in the vehicle body model, and minimizing the length of the joint line, and to find an optimal shape of the component model having low sensitivity to rigidity performance, in, The optimization analysis program causes the computer to function as the following components: an analysis target model setting unit that sets all or part of the vehicle body model as an analysis target model; a joining line optimization analytical model generating unit that generates a joining line optimization analytical model by setting all candidate joining lines that are candidates for the optimally arranged joining lines for the analysis target model; a variable load condition setting unit that divides the variable load provided to the joint line optimization analytical model into load conditions of a plurality of different vibration modes, and sets a variable load condition that combines the load conditions of the vibration modes in a predetermined number of cycles to form a sequence; a target fatigue life setting unit, which sets a target fatigue life of the joint line optimization analytical model according to the sequence number of the variable load condition; a component rigidity sensitivity analysis unit, which sets an objective function related to the rigidity performance of the joint line optimization analysis model, a constraint condition related to the volume of the component model constituting the joint line optimization analysis model, and a variable load condition provided to the joint line optimization analysis model, performs sensitivity analysis of the component model constituting the joint line optimization analysis model that satisfies the objective function under the variable load condition and the constraint condition, and selects a rigidity low-sensitivity component model having a low sensitivity to rigidity performance based on the sensitivity of the component model; a joining line and component shape optimization analytical model generating unit for generating a joining line and component shape optimization analytical model in which the candidate joining line of the joining line optimization analytical model and the plane elements constituting the rigidity low-sensitivity component model are set as a design space; an optimization analysis condition setting unit, for performing optimization analysis with the joint line·component shape optimization analysis model as an optimization object, obtaining the number of fracture repetitions near each joint candidate line for the load condition of each vibration mode, obtaining the total number of sequences of the variable load condition set by the target fatigue life setting unit, which is the ratio of the number of cycles of the load condition of each vibration mode to the number of fracture repetitions, as the cumulative damage degree of each joint candidate line, setting conditions related to the cumulative damage degree of the joint candidate line remaining after the optimization analysis, conditions related to the rigidity of the joint line·component shape optimization analysis model, and conditions related to the length of the joint candidate line remaining after the optimization analysis as objective functions or constraints as optimization analysis conditions, and setting constraints related to the volume ratio of the rigid low-sensitivity component model; and An optimization analysis unit provides the variable load condition set in the variable load condition setting unit to the joining line and component shape optimization analysis model, performs optimization analysis under the optimization analysis condition, obtains the configuration of the joining candidate line achieved for the purpose of reducing the cumulative damage degree of the joining candidate line, improving the rigidity of the optimization analysis model, and minimizing the length of the remaining joining candidate line as the optimal configuration of the joining line, and obtains the residual shape of the rigidity low-sensitivity component model as the optimal shape of the component model with low sensitivity to rigidity performance.

6. The optimization analysis program for the joint position of the vehicle body according to claim 5, The optimization analysis unit performs topology optimization based on a density method, and in the topology optimization, a penalty coefficient is set to 4 or more to perform discretization.

7. A method for manufacturing a vehicle body, wherein a joint line for joining a component group in a vehicle body is optimally arranged to improve the rigidity of the vehicle body and the fatigue life of the joint line, in, Using the method for optimizing the joint position analysis of a vehicle body as described in claim 1 or 2, the optimal shape of the component model with low sensitivity to rigidity performance and the optimal configuration of the joint line are obtained, the shape of the corresponding vehicle body component is changed based on the optimal shape of the component model, the joint position of the component group in the vehicle body is determined based on the obtained optimal configuration of the joint line, and the component group of the vehicle body is joined at the determined joint position.

Images