JP2012208002A - Strength analyzing device, method and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately analyze strength of an article at high speed while considering diversified fixtures.SOLUTION: A strength analyzing device executes: a step (300) for reading a small-sized model 52 of a suspension member; steps (302 and 304) for setting a load weight applying position P, a fastening position and a stiffness identification point A between the suspension member and a fixture; a step (306) for obtaining reaction force F when the load weight is applied to the suspension member; a step (314) for reading actual displacement magnitude D; steps (316 to 322) for repeating processes until a virtual spring with a spring constant K becomes available as a substitute for the fixture; and steps (324 and 326) for setting up the fixture as the virtual spring with the spring constant K. The steps realize a short-time and detailed analysis while securing analysis accuracy.

Description

  The present invention relates to a strength analysis apparatus, method, and program for analyzing the strength of an article.

  Various articles are provided in a vehicle as a typical mobile body, and various tests are performed on these articles. For example, in order to grasp the strength of a part, a strength test is performed using a fatigue strength test apparatus or the like. In recent years, simulation tests using computers have been carried out in order to improve the efficiency of component development and reduce development costs. For example, in a component strength test, a performance evaluation method based on CAE (Computer Aided Engineering) analysis by a finite element method (FEM) is used.

  Patent Document 1 discloses an apparatus for identifying the rigidity of an elastic support that elastically supports a vibration source on a base. The elastic support is modeled by spring rigidity, and a theoretical rigidity value is calculated from a force balance equation at the vibration source. An apparatus for identifying stiffness of an elastic support for identifying stiffness is described.

JP 2006-317394 A

  By the way, when testing an actual vehicle component, the vehicle component is fixed to a fixing jig and tested. Therefore, when a strength test is performed by CAE analysis, not only parts of a vehicle but also a fixing jig for fixing the parts needs to be divided into elements for numerical calculation by a finite element method.

  On the other hand, in CAE analysis, it is desired to obtain an analysis result accurately and at high speed. For this purpose, modeling using a detailed mesh divided by minute elements is performed. However, there are various specifications and shapes of fixing jigs, and the jigs are frequently changed for each test to be performed. Creation took a lot of time.

  In addition, modeling the fixing jig with a detailed mesh increases the overall model size by combining the parts and the fixing jig, resulting in a huge calculation cost.

  In view of the above facts, an object of the present invention is to obtain a strength analysis apparatus, method, and program for analyzing the strength of an article accurately and at high speed while considering various fixing jigs.

  The strength analysis apparatus according to the first aspect of the present invention is an analysis in which an article is calculated in accordance with a numerical calculation model using a finite element method for dividing an article into a plurality of elements in order to simulate the strength of the article. When the model is a large-scale model, setting means for setting each analysis model in which the analysis model obtained by dividing the article by elements larger than the elements of the large-scale model is a small-scale model, and the article is vibrated by a predetermined load Reading means for measuring the displacement of the article in advance and a jig for fixing the article as a virtual spring, the analysis model of the article as a small model, the small model is vibrated, and the fixed state An identification means for identifying a spring constant of the virtual spring based on the obtained reaction force and the read displacement amount; The virtual spring and fixture, having an analyzing unit that performs intensity analysis of the article by analyzing the large model using the finite element method.

  In the strength analysis apparatus of the present invention, the setting unit sets an analysis model that is a large-scale model for the article and an analysis model that is a small-scale model obtained by dividing the article by elements larger than the elements of the large-scale model. The identification unit vibrates a small-scale model of the article using the jig for fixing the article as a virtual spring, and identifies the spring constant of the virtual spring from the reaction force of the virtual spring and the actual displacement amount measured in advance. The analysis means analyzes the strength of the article by analyzing the large-scale model using the finite element method using the identified virtual spring having the spring constant as a fixing jig.

  Therefore, according to the present invention, a virtual spring is used instead of a fixing jig dedicated to a target part using a small-scale model obtained by dividing a mesh with a large element for simulating the influence of rigidity on a target part having a complicated shape. Therefore, the identification process can be completed in a short time. In addition, since the influence of the fixing jig rigidity is simulated by the virtual spring, detailed modeling of the fixing jig main body is not necessary, so that the number of model creation steps can be reduced. In addition, since the fixing jig is a virtual spring, when analyzing the target part in detail, it is possible to analyze with a detailed model (large model) of the target part and the fixing jig with the virtual spring, ensuring analysis accuracy. However, detailed analysis is possible in a short time.

  According to a second aspect of the present invention, in the strength analysis apparatus according to the first aspect, the identification means identifies the spring constant of the virtual spring by determining the spring constant by dividing the reaction force by the amount of displacement. It is characterized by.

  The identification means divides the reaction force by the actually measured displacement amount to obtain the spring constant, so that the virtual spring to be identified reflects the rigidity of the actual fixing jig, and the analysis accuracy is improved.

  According to a third aspect of the present invention, in the strength analysis apparatus according to the first or second aspect, the identification unit vibrates the small-scale model using a virtual spring based on the identified spring constant as a fixing jig. And the identification of the spring constant is repeated until the displacement is within an allowable range.

  Further, the identification means further improves the analysis accuracy by repeating the identification of the spring constant until the displacement amount falls within the allowable range.

  According to a fourth aspect of the present invention, in the strength analysis apparatus according to the third aspect, the permissible range is determined by a ratio between a displacement amount measured in advance and a displacement amount of a calculation result.

  When identifying the spring constant, the calculation of identifying the spring constant does not cause an infinite loop or divergence by determining the ratio between the displacement amount measured in advance and the displacement amount of the calculation result. For this reason, the identification process can be completed in a short time.

  According to a fifth aspect of the present invention, in the strength analysis apparatus according to any one of the first to fourth aspects of the present invention, the article is a fixed portion that is fixed to a moving body, and a load that imparts a load to the article. The identification means is characterized in that a load is applied to the applying unit to vibrate the small-scale model to obtain a reaction force in the fixed unit.

  The article to be analyzed by the strength analysis apparatus of the present invention is preferably an article to be fixed to a moving body. In this case, the article has a fixing portion to be fixed to the moving body and an applying portion for applying a load to the article. is there. And the identification means can identify a virtual spring for analysis that matches the actual article by applying a load to the applying unit to vibrate the small-scale model and obtaining a reaction force in the fixed unit.

  The strength analysis method of the invention described in claim 6 is an analysis in which the article is calculated corresponding to a numerical calculation model using a finite element method for dividing the article into a plurality of elements in order to simulate the strength of the article. When the model is a large model, a setting step for setting each analysis model in which the analysis model obtained by dividing the article with elements larger than the elements of the large model is a small model, and the article is vibrated with a predetermined load A reading step of reading a displacement amount measured in advance of the displacement of the article, and a fixing jig for the article as a virtual spring, an analysis model of the article as a small-scale model, the small-scale model is vibrated, and a fixed state An identification step for obtaining a reaction force generated by the virtual spring, and identifying a spring constant of the virtual spring based on the obtained reaction force and the read displacement amount; and The virtual spring and fixture, having an analyzing step of performing a strength analysis of the article by analyzing the large model using the finite element method.

  According to the strength analysis method of the present invention, the identification process can be completed in a short time, and the calculation load can be reduced. In addition, since detailed modeling of the fixture main body is not required, the number of man-hours for model creation can be reduced. Furthermore, the analysis can be performed by the detailed model of the target part and the fixing jig using the virtual spring, and the detailed analysis can be performed in a short time while ensuring the analysis accuracy.

  The invention according to claim 7 is a strength analysis program for analyzing the strength of an article by a computer, and uses a finite element method for dividing the article into a plurality of elements in order to analyze the strength of the article in a simulated manner. A setting step for setting each analysis model to be a large-scale model that is calculated in correspondence with the numerical calculation model, and to be a small-scale model that is obtained by dividing the article with elements larger than the elements of the large-scale model; A reading step for reading a displacement amount measured in advance when the article is vibrated by a predetermined load; a fixing jig for the article is a virtual spring; and an analysis model of the article is a small-scale model The small-scale model is vibrated to obtain a reaction force generated by a virtual spring in a fixed state, and based on the obtained reaction force and the read displacement amount, An identification step for identifying the spring constant of the imaginary spring, and an analysis step for analyzing the strength of the article by analyzing the large-scale model using a finite element method using the virtual spring of the identified spring constant as a fixing jig And causing the computer to execute each step.

  According to the intensity analysis program of the present invention, the identification process can be completed in a short time in a computer, and the calculation load can be reduced. Further, since detailed modeling of the fixing jig main body is not required, the number of man-hours for model creation using a computer can be reduced. Furthermore, the analysis can be performed by the detailed model of the target part and the fixing jig using the virtual spring, and the detailed analysis can be executed in a short time while ensuring the analysis accuracy in the computer.

  According to the present invention, since the virtual spring is set by simulating the influence of the rigidity of the fixing jig using a small-scale model for a target object having a complicated shape, the number of steps for creating a detailed model of the fixing jig can be reduced in the analysis.

  Further, since the virtual spring is set as the fixing jig using the displacement amount obtained by measuring the displacement of the article in advance, detailed analysis can be performed in a short time while ensuring the analysis accuracy.

It is a flowchart which shows the flow of the fixing jig rigidity identification process in the intensity | strength analysis apparatus concerning embodiment of this invention. It is a block diagram showing the outline of the intensity analysis device concerning the embodiment of the present invention. It is a flowchart which shows the flow of the fatigue strength analysis process performed in the strength analysis apparatus concerning embodiment of this invention. It is explanatory drawing of the fatigue strength analysis process performed in the strength analysis apparatus concerning embodiment of this invention, (A) is a schematic diagram of an object part and a fixing jig, (B) is an image figure of a small-scale mesh model, C) is an image diagram of a large-scale mesh model. It is a flowchart which shows the flow of a creation process of the displacement database used with the intensity | strength analysis apparatus concerning embodiment of this invention. It is a perspective view which shows schematic structure of the suspension member which is an example of the component analyzed in the intensity | strength analysis apparatus concerning embodiment of this invention. It is explanatory drawing of the fatigue strength analysis process performed in the strength analysis apparatus concerning embodiment of this invention, (A) is an image figure when analyzing from a virtual spring and a large-scale mesh model, (B) is a measured value and analysis It is a diagram which shows a result value.

<Strength analyzer>
As shown in FIG. 2, the strength analysis apparatus 10 according to the present embodiment includes a computer main body 12 including a CPU 14, a RAM 16, and a ROM 18. The computer main body 12 includes an input / output interface 20, and the input / output interface 20 is connected to the CPU 14, the RAM 16, and the ROM 18 via a bus 22 so as to be able to exchange data and commands.

  The input / output interface 20 is connected to a mouse or keyboard, which is a pointing device, as an input / output device 26, and a display 24 for displaying data, commands, and other various images. The input / output interface 20 is connected to an identification unit 30, a CAE analysis unit 32, and a recording device 34.

  The identification unit 30 is a processing unit that takes charge of the fixing jig rigidity identification process, and is a processing unit that identifies the rigidity of the fixing jig that fixes the target component for strength analysis. The identification unit 30 does not use an analysis model (large-scale mesh model: hereinafter referred to as a large-scale model) divided by a detailed mesh for numerical calculation at the time of strength analysis of the target component for strength analysis, but with a coarse mesh. Identification processing is performed using the divided analysis model (small mesh model: hereinafter referred to as a small model).

  Further, the identification unit 30 replaces the fixing jig with a virtual spring to identify the spring constant of the virtual spring instead of modeling the fixing jig with a mesh model for numerical calculation when performing strength analysis. To identify the rigidity of the fixture. The identification unit 30 is a device that functions by a combined operation of the hardware resources described above and software resources described later. That is, the identification unit 30 includes a memory that stores a program for executing a flowchart of a process whose details will be described later. Therefore, the strength analysis device 10 including the identification unit 30 functions as a fixing jig stiffness identification device by the configuration of hardware resources and software resources and a complex process.

  The CAE analysis unit 32 is a processing unit in charge of CAE analysis processing, and is a processing unit that performs CAE analysis including strength analysis on the target part. The CAE analysis unit 32 analyzes the target part using a large-scale model. The analysis is performed using a virtual spring having a spring constant identified by the identification unit 30 as a fixing jig. The CAE analysis unit 32 is a device that functions by a combined operation of the above-described hardware resources and software resources described later. That is, the CAE analysis unit 32 includes a memory that stores a program for executing a flowchart of a process whose details will be described later. Therefore, the strength analysis apparatus 10 including the CAE analysis unit 32 functions as an analysis apparatus by the configuration and the complex operation of hardware resources and software resources.

  The recording device 34 includes a recording area 36 that stores an analysis model, and a recording area 38 that stores a displacement amount. In the recording area 36 of the recording device 34, an analysis model (large model) divided by a detailed mesh for numerical calculation at the time of strength analysis and an analysis model divided by a coarser mesh than the large model for a plurality of target parts for strength analysis. The analysis model pair (small model) is stored. As these analysis models, a large-scale model and a small-scale model composed of nodes, sides, and the like are obtained in advance for each target part, and numerical calculation data such as the nodes and sides are stored.

  Further, in the recording area 38 of the recording device 34, an actual measurement value of a displacement amount when a load load is applied to the target component is stored for each fixing jig for fixing the target component. The actual measurement value is measured by a fatigue strength measuring device that performs a bench test of the component strength on the target component, for example. The measurement is performed by measuring a displacement amount when a load load is applied to the target component with respect to a fixing position (attachment position) between the target component and the fixing jig in a state where the target component is fixed to the fixing jig. In other words, a load weight value and a displacement data set are stored as measurement values for each target part and each fixing jig for fixing the target part. The load weight may be applied so that the target part vibrates or may be applied linearly. In addition, the fixing position (clamping position) of the target part to the fixing jig and the load applying position to be applied to the target part vary depending on the shape of the target part, the performance to be analyzed, etc. It is preset by the combination.

  The recording area 38 of the recording device 34 includes a recording area 40. The recording area 40 stores determination data representing an allowable range for determining the suitability of the spring constant of the virtual spring 62 when the identification unit 30 performs identification. As an example of this determination data, a range with respect to the ratio between the actual displacement amount and the calculated displacement amount can be adopted, and the calculated displacement amount d is within 10 percent before and after the actual displacement amount D (0.9 <d / D < There is data showing 1.10).

  FIG. 6 shows a suspension member 51 as an example of a target part. For example, for this suspension member 51, in order to obtain a mesh model for numerical calculation of strength analysis as a large-scale model, many element divisions exceeding about 12 million elements are required. On the other hand, as will be described in detail later, the small-scale model only needs to be able to reproduce the rigidity. Therefore, coarse mesh division may be used, and element division using about tens of thousands of elements may be used.

  In addition, the suspension member 51 has four fastening positions 56 (56A to 56D in FIG. 6) in order to be fixed to the fixing jig by fastening with screws or the like. The suspension member 51 has an application position 58 for applying a load load to the target part. This application position 58 is an example, and can be set at an arbitrary position of the suspension member 51. For the suspension member 51, a large-scale model and a small-scale model analysis model composed of numerical calculation data such as nodes and sides are stored in the recording area 36. Further, for example, the displacement amounts of the four tightening positions 56 (56A to 56D) measured when a load load is applied to the application position 58 of the suspension member 51, which is measured by a strength test apparatus that performs a bench test of the component strength or the like. A data set of actual measurement values and load weight values is stored in the recording area 38. Further, a ratio range (0.9 <d / D <1.10) between the actual displacement amount D and the calculated displacement amount d is stored in the recording area 38 as determination data representing the allowable range.

  The input / output interface 20 may be connected to a recording device in which a magnetic disk as a recording medium can be inserted and removed, or an auxiliary storage device having an electronic circuit having a recording area. A program such as a processing routine described later can be read from and written to the magnetic disk and the recording area using a recording device and an auxiliary storage device. Therefore, programs such as processing routines to be described later are recorded in advance in a magnetic disk or storage area without being stored in the ROM 18, and the processing program recorded in advance is executed via the recording device or auxiliary storage device. Also good. Further, a mass storage device (not shown) such as a hard disk device may be connected to the computer main body 12, and the program may be stored (installed) in the mass storage device (not shown) and executed. Also, recording media include disks such as CD-ROM, MD, MO, and DVD, magnetic tapes such as DAT, and auxiliary storage devices such as flash memory and SSD (Solid State Drive) as recording areas. Yes, when these are used, a CD-ROM device, MD device, MO device, DVD device, DAT device, auxiliary storage device or the like may be used.

<Strength analysis processing>
FIG. 3 shows the flow of the strength analysis process, and FIG. 4 shows a schematic diagram of the strength analysis process for the target component 50 and the fixing jig 60. With reference to these FIG.3 and FIG.4, the action | operation of the intensity | strength analyzer 10 of this Embodiment is demonstrated. In this embodiment, the case where the fatigue strength analysis process is performed is described as an example of the strength analysis, but the present invention is not limited to this, and the state where the target part is fixed to the jig is reproduced on the computer. It can be applied to analysis processing and performance evaluation processing using a mesh model.

  The outline of the operation of the strength analyzer 10 includes the following four processes. In the first process, an analysis model is created. That is, an analysis model (a large-scale model and a small-scale model) of a part (target part) to be subjected to strength analysis is created and stored in the recording area 36 of the recording device 34. In the second process, a displacement database (displacement DB) is created. That is, the actual target component 50 (suspension member 51) is fixed to a fatigue strength measuring device (not shown) together with a fixing jig (tightening), and the displacement amount of the fastening position is measured. In the third process, the fixture rigidity is identified. That is, the spring constant of the virtual spring 62 is identified using the small model 52 created in the first process. In the fourth process, the fatigue strength CAE analysis of the target part is performed. That is, the CAE analysis is performed on the large-scale model 54 created in the first process using the virtual spring 62 based on the spring constant identified in the third process as a fixing jig.

  As shown in FIG. 3, in detail, in the strength analysis apparatus 10 of the present embodiment, an analysis processing routine is executed to enable strength analysis of the target component 50 (for example, the suspension member 51). Here, it is assumed that the target component 50 is fixed to the fixing jig 60 at the fastening point 55 (see FIG. 4A).

  In step 100, an analysis model of a large model and a small model is created. Specifically, in this step 100, a design plan (shape, structure, material, etc.) of a target part to be analyzed, for example, a suspension member is determined. This setting is not limited to the design plan, but includes a case where an existing part is analyzed. That is, the existing target part itself may be set as a target model. Then, an analysis model of the target part for creating the design plan into the model for numerical analysis is created. The creation of this analysis model differs slightly depending on the numerical analysis method used. In this embodiment, a finite element method (FEM) is used as a numerical analysis method. Therefore, the analysis model to be created is divided into a plurality of elements having an arbitrary shape such as a triangle by element division corresponding to the finite element method (FEM), for example, mesh division, and the parts are based on numerical and analytical methods. This is a digitized version of the input data format for a computer program created in this way. This element division refers to dividing the target part into several small (finite) small parts. After calculating every small part and calculating all the small parts, the whole response can be obtained by adding all the small parts. This analysis model creation process is performed by dividing a large-scale model 54 (see FIG. 4C) divided into a plurality of fine elements by mesh division and a small-scale model 52 divided into a plurality of coarse elements (FIG. 4B). )) And create.

  In step 100, the process of creating the analysis model of the target component 50 will be described. However, the analysis model may be created in advance by another device and stored in the recording area 36.

  In the embodiment, the process of creating the analysis model will be described. However, the analysis model may be created in advance by another device and stored in the recording area 36.

  In the next step 110, a displacement database (displacement DB) for the fixture for the target part is created. In this step 110, the actual target component 50 (suspension member 51) is fixed to a fatigue strength measuring device (not shown) together with a fixing jig (clamping), the displacement amount of the tightening position is measured, and the combination of the displacement amount and the load weight is combined. To obtain a data set and store it in the recording area 38.

  In the embodiment, the process of creating the analysis model will be described. However, the data set may be created in advance by another device and stored in the recording area 38.

  In the next step 120, details of which will be described later (see FIG. 1), the fixing jig rigidity of the target component 50 (suspension member 51) is identified. That is, the rigidity of the fixing jig is identified by identifying the spring constant of the virtual spring 62 when the small scale model 52 is used as the analysis model created in step 100 and the fixing jig 60 is the virtual spring 62 (see FIG. 4 (B)).

  In the next step 130, the fatigue strength CAE analysis of the target part is performed. That is, CAE analysis is executed on the large-scale model 54 created in step 100 using the virtual spring 62 based on the spring constant identified in step 120 as a fixing jig (see FIG. 4C).

  With the above processing, the fixing jig 60 is the virtual spring 62, the spring constant K of the virtual spring 62 is identified, and the virtual spring 62 with the spring constant K is fixed to the large-scale model 54 as the fixing jig. Fatigue strength analysis processing can be performed. Thereby, it is possible to perform analysis with a simple configuration using a virtual spring without dividing the fixing jig into a mesh and modeling, and the calculation load can be reduced. In addition, since it is not necessary to model the fixing jig, the time required to analyze the model of the fixing jig is not required, and the processing time required for the fatigue strength analysis process can be shortened.

  Step 100 corresponds to a process of creating an analysis model for setting by the setting means, and step 110 corresponds to a process of creating a displacement amount for reading by the reading means. Step 120 corresponds to the identification process of the identification unit, and step 130 corresponds to the intensity analysis process of the analysis unit.

<Displacement database>
FIG. 5 shows an example of the flow of processing for creating a displacement database (displacement DB) used in the strength analysis apparatus as details of step 110 in FIG. This process may be performed by the strength analysis apparatus 10 or may be performed by another apparatus.

  In step 200, a fatigue strength test (load weighting) of the target component 50 (actual target component, for example, the suspension member 51) is started using the fatigue strength measuring device. In the next step 210, the displacement of the tightening position between the target part and the fixing jig when the load weight is applied is measured. In the next step 220, the load weight value and the displacement value for each tightening position are recorded (database saved).

  In the example of FIG. 6, the four fastening positions 56 (tightening positions 56A, 56B, 56C, 56D) of the suspension member 51 are fastened and fixed to a fixing jig of a fatigue strength measuring device (not shown), and the application position 58 is fixed. Is given a load weight. The load weight value at the time of measurement and the displacement value for each tightening position (tightening positions 56A, 56B, 56C, 56D) are recorded (stored in a database). For each of these tightening positions (tightening positions 56 </ b> A to 56 </ b> D), a data set including a displacement value with a load weight value is stored in the recording area 38 as a measured value.

  At this time, a ratio range (0.9 <d / D <1.10) between the actual displacement amount D and the calculated displacement amount d is stored in the recording area 38 as determination data representing the allowable range. As the determination data representing the allowable range, an average value of measured values obtained by measuring a plurality of target parts 50 of the same type or a value determined in advance as an allowable range in design can be adopted.

<Fixing jig rigidity identification process>
FIG. 1 shows an example of the flow of the fixing jig rigidity identification process according to the present invention as details of step 120 in FIG. This processing may be performed by the strength analysis apparatus 10 or may be performed by an independent apparatus. In the present embodiment, it is executed by the identification unit 30.

  In step 300, an analysis model for identifying the fixture rigidity is read from the recording area 36. Here, since only the rigidity is obtained, a small-scale model 52 sufficient for obtaining the rigidity is read. In the next step 302, a load weight application position P and a tightening position are set for the analysis model. Here, since the suspension member 51 is used as the target component 50, it corresponds to the four tightening positions 56A to 56D to be fixed to the fixing jig by tightening with screws or the like, and the applying position 58 for applying the load weight. A position on the small model 52 is set (see FIG. 6).

  Next, in step 304, a stiffness identification point A is set. The rigidity identification point A is a tightening point 55 between the target component 50 (suspension member 51) and the fixing jig 60 for identifying the rigidity of the fixing jig in numerical calculation (see FIG. 4A). That is, there are four tightening positions 56A to 56D. In the present embodiment, a case where the rigidity of the fixing jig is identified for each tightening position will be described. Therefore, in this step 304, any one of the four tightening positions 56A to 56D is set as the rigidity identification point A. The setting of the stiffness identification point A may be set by input from the input / output device 26, or may be set in an order based on a predetermined priority order or may be set randomly (randomly). In the following description, a case where the tightening positions 56A, 56B, 56C, and 56D are set in this order will be described.

  Here, the case of identifying the rigidity of the fixing jig for each tightening position (identifying the spring constant of the virtual spring) will be described. However, in the following description, all the tightening positions are processed within each step. May be. That is, you may replace with the process which calculates | requires each fastening position in each step.

  Further, when the tightening position 56 has a region or a plurality of points, the rigidity identification point A can be set to any one of the plurality of points of the tightening position 56 or within the region. For example, one tightening position 56A on the front side of the suspension member 51 has a through hole 56AH for passing a screw or the like, and has a contact portion 56AT around it (see FIG. 6). Accordingly, the contact portion 56AT comes into contact with the fixing jig. Here, one point in the tightening region composed of the surface of the contact portion 56AT and the surface region of the through hole 56AH continuous with the surface is determined as a rigidity identification point. Set to A. For example, one point of the inner peripheral portion of the contact portion 56AT, one point of the outer peripheral portion, the center of gravity of the tightening region, or the center point of the surface region of the through hole 56AH is set. That is, the tightening position 56 </ b> A consisting of the region is regarded as one point, and that one point is set as the rigidity identification point A. Further, the application position P (application position 58) to which the load weight is applied is set similarly.

  In the next step 306, the reaction force F is calculated. In this step 306, three processes of steps 308 to 312 are executed. First, in step 308, all tightening positions of the analysis model (small model 52) are set to be fixed (completely constrained). In the next step 310, a predetermined load weight is applied to the application position P. This simulates the measurement of fatigue strength when the small-scale model 52 of the suspension member 51 is fixed to a fixing jig. Next, in step 312, the reaction force F at the stiffness identification point A is calculated. Here, calculation is performed for each element in which the suspension member 51 is roughly mesh-divided, and calculation is performed for all small parts. Then, the entire response is obtained by adding all the small parts. Therefore, after calculating for each element when a predetermined load weight is applied to the application position P and obtaining an overall response, the reaction force F is obtained.

  When the reaction force F is obtained, the process proceeds to step 314, and a data set of the load weight value and the actual displacement amount D for the tightening position 56A is read from the displacement database (displacement DB) stored in the recording area 38. That is, the data set of the measured values of the displacements at the tightening positions 56 </ b> A to 56 </ b> D when the load weight is applied to the application position 58 of the suspension member 51 and the load weight value measured by the strength test apparatus is read.

  In the next step 316, the spring constant K is calculated from the obtained reaction force F and the actual displacement D of the stiffness identification point A. Here, as an example, Hooke's law is used, and a value obtained by dividing the reaction force F by the displacement amount D is defined as a spring constant K (K = F / D). The calculation of the spring constant K is not limited to Hooke's law, and the spring constant K may be calculated by other methods. When the spring constant K is obtained, in step 318, the virtual spring 62 having the spring constant K is attached to the rigidity identification point A as a fixing jig for the tightening position 56A (see FIG. 4B).

  Next, in step 320, the displacement amount d of the stiffness identification point A and its reaction force (F) are calculated by FEM. That is, the tightening positions other than the tightening position 56A of the small model 52 are fixed (completely constrained), and the load model is applied to the applying position P in the same manner as in Step 310, whereby the small model 52 of the suspension member 51 is mounted. The fatigue strength measurement when fixed to a fixture is simulated again. Then, the reaction force F at the stiffness identification point A is calculated again, and the displacement amount d of the stiffness identification point A is calculated.

  In the next step 322, it is determined whether or not the virtual spring 62 can be replaced with a fixing jig. This determination is made by determining from the determination data representing the allowable range stored in the recording area 38 based on whether or not it is within the allowable range. Here, as an example, the ratio (d / D) between the actual displacement D and the calculated displacement d can be employed. That is, in step 322, a ratio between the actual displacement amount D and the calculated displacement amount d is obtained, and whether or not the obtained ratio is within the allowable range (0.9 <d / D <1.10). Determine.

  In step 322, whether or not the virtual spring 62 can be replaced with a fixing jig is determined based on the ratio between the actual displacement D and the calculated displacement d. However, the ratio is limited to this ratio. Of course, it may be within the range of the displacement amount d itself. In step 322, the determination is made based only on the amount of displacement, but the reaction force may be considered. When considering the reaction force, it may be considered to determine whether the ratio of the reaction force obtained in step 312 and the reaction force F obtained in step 320 is within an allowable range.

  If the result in Step 322 is negative, the process returns to Step 316 and Steps 316 to 320 are repeated. In this case, steps 316 to 320 are executed again instead of the reaction force F obtained in step 312 instead of the reaction force F obtained in step 320. That is, when the reaction force F obtained in step 312 is larger than the reaction force F obtained in step 320, the reaction force F (= F) slightly decreased from the reaction force F obtained in step 320 so that the reaction force F becomes smaller. -Α) is set. On the other hand, when the reaction force F obtained in step 312 is larger than the reaction force F obtained in step 320, the reaction force F slightly increased from the reaction force F obtained in step 320 (= F + α) so that the reaction force F becomes larger. ) Is set.

  As described above, when the process is repeated from step 316, the ratio of the actual displacement D and the calculated displacement d can be used. That is, when the ratio (d / D) exceeds the allowable range, the calculated displacement amount d is large, so the reaction force F slightly reduced from the reaction force F obtained in step 320 is set so as to be small. On the other hand, when the ratio (d / D) is less than the allowable range, since the calculated displacement amount d is small, the reaction force F slightly increased from the reaction force F obtained in step 320 is set so as to increase.

  On the other hand, when the result in step 322 is affirmative, the routine proceeds to step 324, where the spring constant K is determined as the virtual spring constant K. That is, the fixing jig 60 for the tightening position 56A of the suspension member 51 is set to be replaceable with a virtual spring 62 having a spring constant K.

  Next, in step 326, it is determined whether or not the above processing has been completed for all tightening positions. If the result is negative, the processing returns to step 304 and the above processing is repeated for the remaining tightening positions (56B to 56D). . On the other hand, when the result in step 326 is affirmative, this processing routine is terminated.

  As described above, when virtual springs are determined for each tightening position, it may be further determined whether all the tightening positions are determined and whether they are within an allowable range. For example, each process of steps 316 to 320 is obtained for the case where the virtual springs 62 are used at the four tightening positions 56A to 56D. Then, it is determined whether or not the ratio of each of the virtual springs 62 at the four tightening positions 56A to 56D is within an allowable range. By doing in this way, the judgment as the whole fixing jig incorporating all the virtual springs defined at each tightening position becomes possible.

  As described above, in the present embodiment, when performing an analysis process for analyzing a target object having a complicated shape, for example, by fixing the target part to a fixing jig dedicated to the target part, the target part is fixed to the fixing jig. A virtual spring is set instead of the fixing jig for each position. When setting the virtual spring, it is only necessary to simulate the effect of the fixture rigidity, so both the fixture body and the target part can be divided into meshes by larger elements without detailed modeling of the fixture body. It becomes possible to identify by the small model. Thus, since the virtual spring is identified by the small model, the identification process can be completed in a short time. Further, since the effect of the fixing jig rigidity is simulated by this virtual spring, detailed modeling (large-scale model) of the fixing jig main body becomes unnecessary. For this reason, the man-hour for model creation can be reduced. Furthermore, because the fixture that fixes the target part for analysis is replaced with a virtual spring, a detailed model (large model) is used only for the target part even when detailed analysis is required for the target part. In addition, by using a fixing jig with virtual springs, it is possible to perform detailed analysis in a short time while ensuring analysis accuracy.

<Example of suspension member analysis>
FIG. 7 shows the result of analyzing the suspension member 51 using the above-described strength analysis apparatus 10 and the result of actually testing the suspension member 51. Here, an aluminum cast suspension was used as the suspension member 51, and the effect was verified by a strength analysis test. As shown in FIG. 7A, the suspension member 51 has tightening positions 56A to 56D and an applying position 58. The tightening positions 56A to 56D and the applying position 58 are set with a rigidity identification point A and a load applying position P, and the tightening positions 56A to 56D are replaced with virtual springs 62 (62A to 62A) instead of the fixing jig. 62D) is attached.

The following table shows the results of the virtual spring constant K obtained for the suspension member 51 by the strength analysis apparatus 10 described above.

  FIG. 7B is a characteristic diagram showing actual measurement values and analysis result values. The horizontal axis indicates the actually measured strain value, and the vertical axis indicates the strain value obtained as a result of calculation by CAE analysis. The unit of the strain value is μ. As can be understood from FIG. 7B, the actually measured strain value and the strain value calculated by the CAE analysis have a linear relationship.

  In effect verification, first, a virtual spring is set for each tightening position with the fixing jig. The spring constant of the virtual panel is identified by the above-described strength analyzer. In this case, the number of iterations for identifying the spring constant was 5, and the displacement at the tightening position could be reproduced within 6%. Since it was used in a small model, one iteration calculation could be completed in about 10 minutes. All identification work times were completed within 2 hours. It was confirmed that the work time of about 2.5 days could be shortened because normal complex fixture model creation required about 3 days.

  In addition, since the model of the fixing jig main body using the virtual spring was omitted, the analysis model scale (degree of freedom) was reduced by about 10%. It was confirmed that the supercomputer CPU time spent for one analysis was about 30 hours and could be reduced by about 3 hours.

  Furthermore, as shown in the results of comparison and verification with the strain measurement values (see FIG. 7B), the analysis accuracy was almost the same as the actual measurement values, so it was confirmed that the analysis accuracy was high.

  In this way, the verification results ensured the accuracy of analysis and reduced model creation time and supercomputer (supercomputer) use time, thus reducing calculation costs.

A Stiffness identification point F Reaction force K Spring constant P Load applied position 10 Strength analysis device 12 Computer main body 30 Identification unit 32 CAE analysis unit 34 Recording device 50 Target component 51 Suspension member 52 Small model 54 Large model 55 Tightening Point 56 Tightening position 56A to 56D Tightening position 58 Application position 60 Fixing jig 62 Virtual spring

Claims (7)

In order to analyze the strength of an article in a simulated manner, an analysis model for calculating an article corresponding to a numerical calculation model using a finite element method that divides an article into a plurality of elements is a large-scale model, and elements of the large-scale model Setting means for setting each analysis model to be a small-scale model obtained by dividing the article by larger elements;
A reading means for reading a displacement amount obtained by measuring in advance the displacement of the article when the article is vibrated by a predetermined load;
The jig for fixing the article is a virtual spring, the analysis model of the article is a small model, the small model is vibrated, and the reaction force generated by the virtual spring in a fixed state is obtained. Identification means for identifying a spring constant of the virtual spring based on the read displacement amount;
Analyzing means for analyzing the strength of the article by analyzing the large-scale model using a finite element method with the identified virtual spring of the spring constant as a fixing jig,
Strength analysis apparatus having   The strength analysis apparatus according to claim 1, wherein the identification unit identifies a spring constant of the virtual spring by dividing a reaction force by a displacement amount to obtain a spring constant.   The identification means uses a virtual spring with the identified spring constant as a fixing jig, obtains a displacement amount when the small-scale model is vibrated, and repeats identification of the spring constant until the displacement amount falls within an allowable range. The strength analysis apparatus according to claim 1 or 2, characterized by the above-mentioned.   The intensity analysis apparatus according to claim 3, wherein the allowable range is determined by a ratio between a displacement amount measured in advance and a displacement amount as a calculation result.   The article has a fixing part for fixing to a moving body, and an attaching part for applying a load to the article, and the identification means applies a load to the applying part to vibrate the small-scale model, and the fixing The strength analysis apparatus according to any one of claims 1 to 4, wherein a reaction force at the portion is obtained. In order to analyze the strength of an article in a simulated manner, an analysis model for calculating an article corresponding to a numerical calculation model using a finite element method that divides an article into a plurality of elements is a large-scale model, and elements of the large-scale model A setting step for setting each analysis model to be a small-scale model obtained by dividing the article by larger elements;
A reading step of reading a displacement amount obtained by measuring in advance the displacement of the article when the article is vibrated by a predetermined load;
The jig for fixing the article is a virtual spring, the analysis model of the article is a small model, the small model is vibrated, and the reaction force generated by the virtual spring in a fixed state is obtained. An identification step of identifying a spring constant of the virtual spring based on the read displacement amount;
An analysis step of analyzing the strength of the article by analyzing the large-scale model using a finite element method with the identified virtual spring of the spring constant as a fixing jig;
Strength analysis method having A strength analysis program for analyzing the strength of an article by a computer,
In order to analyze the strength of an article in a simulated manner, an analysis model for calculating an article corresponding to a numerical calculation model using a finite element method that divides an article into a plurality of elements is a large-scale model, and elements of the large-scale model A setting step for setting each analysis model to be a small-scale analysis model obtained by dividing the article by larger elements;
A reading step of reading a displacement amount obtained by measuring in advance the displacement of the article when the article is vibrated by a predetermined load;
The jig for fixing the article is a virtual spring, the analysis model of the article is a small model, the small model is vibrated, and the reaction force generated by the virtual spring in a fixed state is obtained. An identification step of identifying a spring constant of the virtual spring based on the read displacement amount;
An analysis step for analyzing the strength of the article by analyzing the large-scale model using a finite element method with the identified virtual spring of the spring constant as a fixing jig;
An intensity analysis program that causes a computer to execute each step of.