Material curve automatic calibration method for CAE simulation

Abstract

The invention relates to an automatic material curve calibration method for CAE (Computer Aided Engineering) simulation, which comprises the following steps of: inputting a displacement force curve of a test into a spreadsheet, fitting an effective stress-strain curve to a highest curve of strain 1.0 and fitting the effective stress-strain curve to a lowest curve of strain 1.0, establishing a tensile sample simulation model, and coupling the highest curve and the lowest curve by a coupling coefficient to form a new fitting curve, reading a calculation command line, reading operation output by line through VBA, and identifying an ending content. Displacement data in the preset direction in the displacement file and force data in the preset direction in the force value file are extracted to a spreadsheet to form a displacement-force curve, the goodness of fit between the simulation output curve and the test curve is calculated, and the coupling coefficient is adjusted until the goodness of fit between the simulation output curve and the test curve meets the requirement; according to the method, the optimal material curve for CAE simulation is formed, the human input cost of simulation curve calibration is effectively saved, and the calibration time is shortened.

Description

Technical Field

[0001] The invention relates to the technical field of metal sheet forming, and in particular to an automatic material curve calibration method for CAE simulation. Background Art

[0002] When performing CAE simulation, you need to first determine the input curve and verify whether the input curve can make the simulation output curve and the test curve have the best fit. This process is called curve calibration. The simulation input curve is a curve fitted based on the test curve. After each curve fitting, it needs to go through simulation calculation, simulation post-processing to form the output curve, comparison of the simulation output curve with the test curve, judgment of the modification trend of the input curve, and re-fitting of the test curve. This process requires continuous debugging, which is time-consuming and labor-intensive, and very inefficient.

[0003] The Chinese patent material hardening curve calibration method and system, storage medium, and electronic device with publication number CN116893100A include: step 1, obtaining a force-displacement curve through a uniaxial tensile test; step 2, obtaining a true stress-strain curve before necking based on the force-displacement curve; step 3, obtaining a true stress-strain curve after necking according to the true stress-strain curve before necking; step 4, splicing the true stress-strain curves before and after necking to obtain a material hardening curve; step 5, establishing a uniaxial tensile finite element model identical to the test, and bringing the material hardening curve obtained in step 4 into the finite element model model; step 6, training the radial basis neural network, the training input is the parameter σi; step 7, using the adaptive simulated annealing algorithm to optimize the parameter σi, and obtain the true stress-strain point (σi, εi) after necking; step 8, fitting the stress-strain point (σi, εi), this method improves the efficiency of obtaining the material hardening curve; however, the neural network used in this patent requires a large amount of test data as training data and a large amount of calculation to obtain relatively ideal results, which is basically impossible to achieve in the simulation benchmarking of a single curve, and this patent is mainly based on manual operation, which is inefficient. Summary of the invention

[0004] The present invention provides a material curve automatic calibration method for CAE simulation, which automatically corrects parameters to generate a fitting curve, extracts post-processing data to form an output curve, and judges the curve fitting degree to form an optimal material curve that meets CAE simulation needs. This method can effectively save the manpower investment cost of simulation curve calibration and reduce the calibration time.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A material curve automatic calibration method for CAE simulation includes the following steps:

[0007] S1. Enter the displacement force curve of the test, the effective stress strain curve fitted to the highest curve of strain 1.0, and the effective stress strain curve fitted to the lowest curve of strain 1.0 in a spreadsheet;

[0008] S2. Establish a tensile specimen simulation model, link the material card, and the simulation model outputs the cross-sectional force in the deformation area and the displacement curve with the same gauge length as the test curve;

[0009] S3, coupling the highest curve and the lowest curve with the coupling coefficient to form a new fitting curve, and automatically generating a material card file and submitting a calculation command line;

[0010] S4. In the electronic spreadsheet, the VBA command reads the calculation submission command line of step S3, submits the calculation, and reads the calculation output row by row through VBA. When the end content is recognized, it is determined that the calculation is completed.

[0011] S5. In the spreadsheet, according to the feedback of step S4, the VBA command automatically reads the displacement file and the force value file in the result folder, extracts the displacement data of the pre-set direction in the displacement file and the force data of the pre-set direction in the force value file into the spreadsheet to form a displacement-force curve, displays the agreement between the simulation output curve and the test curve in the spreadsheet, and calculates the agreement between the simulation output curve and the test curve.

[0012] S6. When the degree of fit does not meet the set requirements, the coupling coefficient of step S3 is adjusted based on the coupling coefficient of step S3 and the degree of fit of step S5;

[0013] S7. Repeat steps S3 to S6 until the degree of agreement between the simulation output curve and the test curve meets the requirements.

[0014] Furthermore, in step S1, the highest curve is the curve formed by fitting when the slope of the tangent at multiple points at the end of the effective stress-strain curve is the largest, the lowest curve is the curve formed when the slope of the tangent extended from the end point of the effective stress-strain curve is zero, and the effective stress-strain curve is the curve after the test curve yields to the tensile section.

[0015] Furthermore, the coupling coefficient in step S3 is a constant between 0 and 1, and the specific formula is:

[0016] α=(α1+α2) / 2 (1)

[0017] Among them, α is the coupling coefficient obtained by coupling the highest curve and the lowest curve, and α1 and α2 are coupling coefficients between 0 and 1.

[0018] Furthermore, in step S6, when the degree of fit does not meet the set requirements, when the stress of the simulation curve is greater than the end stress of the test curve at the end strain of the test curve, α2=α; when the stress of the simulation curve is less than the end stress of the test curve at the end strain of the test curve, α1=α.

[0019] Compared with the prior art, the beneficial effects of the present invention are: when performing CAE simulation, the input curve is automatically calibrated, and the parameters can be automatically corrected to generate a fitting curve to generate a material card file, submit an operation command, determine whether the operation is completed, automatically extract the simulation result file for processing to form a displacement force curve, compare it with the test data in the spreadsheet, determine the consistency between the simulation output curve and the test curve, modify the parameters to form a new fitting curve and submit it for calculation again, so as to form the best material curve that meets the CAE simulation, obtain the best simulation fitting curve, and realize the automatic calibration of the material curve for CAE simulation, which can effectively save the manpower investment cost of simulation curve calibration and reduce the calibration time. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a curve calibration flow chart described in an embodiment of the invention. DETAILED DESCRIPTION

[0021] The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings:

[0022] The premise of this invention is that the means of outputting fitting curves are available. Programming and algorithms can be used to automatically fit curves, generate material card files, submit operation commands, determine whether the operation is completed, automatically extract displacement files and force value files of simulation calculations to form displacement-force curves, compare them with test data in spreadsheets, determine the consistency between the simulation output curve and the test curve, modify parameters to form a new fitting curve and submit it for calculation again, and finally obtain the best simulation fitting curve to achieve automatic calibration of material curves for CAE simulation.

[0023] The present invention provides a material curve automatic calibration method for CAE simulation, comprising the following steps:

[0024] S1. Enter three curves in the WPS table, one is the displacement force curve of the test, one is the highest curve of the effective stress-strain curve fitted to the strain of 1.0, and one is the lowest curve of the effective stress-strain curve fitted to the strain of 1.0; the highest curve is the curve formed by fitting when the slope of the tangent at multiple points at the end of the effective stress-strain curve is the largest, the lowest curve is the curve formed when the slope of the tangent extended from the end point of the effective stress-strain curve is zero, and the effective stress-strain curve is the curve after the test curve yields to the tensile section.

[0025] S2. Use the general nonlinear calculation software Ls_Dyna to establish a simulation model of the tensile specimen in Ls_Dyna format. Use the *INCLUDE keyword to link the material card. The simulation model can output the cross-sectional force in the deformation area and the displacement curve with the same gauge length as the test curve.

[0026] S3. The highest curve and the lowest curve are coupled with the coupling coefficient to form a new fitting curve, and the new fitting curve is automatically generated as a Ls_Dyna format material card file and an Ls_Dyna submission calculation command line. The coupling coefficient is a constant between 0 and 1. The specific formula is:

[0027] α=(α1+α2) / 2 (2)

[0028] Among them, α is the coupling coefficient obtained by coupling the highest curve and the lowest curve, and α1 and α2 are coupling coefficients between 0 and 1.

[0029] S4. In the WPS table, the VBA command reads the calculation command line submitted by the general nonlinear calculation software Ls_Dyna in step S3, and uses a shell script to submit the Ls_Dyna operation. At the same time, the operation output is read line by line through the VBA command. When the end content is recognized, it is determined that the operation is finished.

[0030] S5. In the WPS table, according to the feedback from step 4, the VBA command automatically reads the nodout node displacement file and the secforce section force file in the result folder, extracts the displacement data of the pre-set direction in the nodout node displacement file and the force data of the pre-set direction in the secforce section force file into the WPS table to form a displacement-force curve. The chart in the WPS table can intuitively display the consistency between the simulation output curve and the test curve, and calculate the degree of consistency between the simulation output curve and the test curve.

[0031] S6. When the degree of fit does not meet the set requirements, based on the coupling coefficient of step S3 and the degree of fit of step S5, adjust the coupling coefficient of step S3, that is, when the stress of the simulation curve is greater than the end stress of the test curve at the end strain of the test curve, α2=α; when the stress of the simulation curve is less than the end stress of the test curve at the end strain of the test curve, α1=α.

[0032] S7. Repeat steps S3 to S6 until the degree of agreement between the simulation output curve and the test curve meets the requirements.

[0033] The following examples are implemented on the premise of the technical solution of the present invention, and provide detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to the following examples. The methods used in the following examples are conventional methods unless otherwise specified.

[0034] [Example]

[0035] See Figure 1 , a curve calibration flow chart of a material curve automatic calibration method for CAE simulation of the present invention, α, α1 and α2 are fitting curve coupling coefficients, α1 and α2 change with the curve calibration process, are constants between 0 and 1, α=(α1+α2) / 2; Lh is the highest curve of the effective stress-strain curve fitted to the strain of 1.0; Ll is the lowest curve of the effective stress-strain curve fitted to the strain of 1.0; Lin is the fitting curve formed by the coupling of Lh and Ll; Le is the test displacement force curve; Lestress is the end stress of the test curve Le; Loutstress is the stress of the simulation curve Lout corresponding to the end strain of the test curve Le.

[0036] A material curve automatic calibration method for CAE simulation includes the following steps:

[0037] S1. Create two pages in the WPS table. Page 1 is responsible for automatically generating the fitting curve Lin, generating the material card file, submitting the Ls_Dyna operation command and judging whether the operation is completed; Page 2 is responsible for automatically extracting the simulation calculation results to form the displacement force curve Lout, comparing it with the test data Le in the WPS table, judging the consistency between the simulation output curve Lout and the test curve Le, determining whether it is necessary to modify the parameters to form a new fitting curve Lin and submit the calculation again.

[0038] S2. Enter two curves in WPS table page 1, one is the highest curve Lh of the effective stress-strain curve fitted to the strain of 1.0, and the other is the lowest curve Ll of the effective stress-strain curve fitted to the strain of 1.0; the highest curve Lh is the curve formed by fitting when the slope of the multi-point tangent at the end of the effective stress-strain curve Lt is the largest, and the lowest curve Ll is the curve formed when the slope of the extended tangent of the effective stress-strain curve Lt is zero. The effective stress-strain curve Lt is the curve that yields to the tensile section after the test curve Le is converted into the effective stress-strain curve. Enter the displacement force curve Le of the test in WPS table page 2.

[0039] S3. Establish a simulation model of tensile specimen in Ls_Dyna format, use *INCLUDE keyword to link material cards, the simulation model can output the cross-sectional force in the deformation area and the displacement curve with the same gauge length as the test curve, and set the coupling coefficients α1=0, α2=1.

[0040] S4, coupling coefficient α = (α1 + α2) / 2, the highest curve Lh and the lowest curve Ll are coupled with the coupling coefficient α to form a new fitting curve Lin, and automatically generate Ls_Dyna format material card file and Ls_Dyna submission calculation command line, read Ls_Dyna submission calculation command line, use wshshell command to submit Ls_Dyna operation, and read the operation output line by line through VBA. When the end content is recognized, it is judged that the operation is finished.

[0041] S5. In WPS table page 2, according to the feedback of step 4, the VBA command automatically reads the nodout node displacement file and the secforce section force file in the result folder, extracts the displacement data of the pre-set direction in the nodout node displacement file and the force data of the pre-set direction in the secforce section force file to WPS table page 2, and forms the simulation output displacement-force curve Lout. The chart in page 2 can intuitively display the consistency of the simulation output curve Lout with the test curve Le, and calculate the degree of consistency between the simulation output curve Lout and the test curve Le.

[0042] S6. When the fit does not meet the set requirements, find the stress Loutstress when the strain of the simulation output curve Lout is Loutstrain, Loutstrain is approximately equal to the end strain Lestrain of the test curve Le, Lestress is the end stress of the test curve Le, if Loutstress>Lestress, update α2=α; if Loutstress<Lestress, update α1=α.

[0043] S7, repeat steps S4 to S6 until the degree of agreement between the simulation output curve Lout and the test curve Le meets the requirement, and the fitting curve Lin finally formed in step S4 is the input curve that can be used for CAE simulation.

Claims

1. A material curve automatic calibration method for CAE simulation, characterized in that: The steps include: S1. Enter the displacement force curve of the test, the effective stress strain curve fitted to the highest curve of strain 1.0, and the effective stress strain curve fitted to the lowest curve of strain 1.0 in a spreadsheet; S2. Establish a tensile specimen simulation model, link the material card, and the simulation model outputs the cross-sectional force in the deformation area and the displacement curve with the same gauge length as the test curve; S3, coupling the highest curve and the lowest curve with the coupling coefficient to form a new fitting curve, and automatically generating a material card file and submitting a calculation command line; S4. In the electronic spreadsheet, the VBA command reads the calculation submission command line of step S3, submits the calculation, and reads the calculation output row by row through VBA. When the end content is recognized, it is determined that the calculation is completed. S5. In the spreadsheet, according to the feedback of step S4, the VBA command automatically reads the displacement file and the force value file in the result folder, extracts the displacement data of the pre-set direction in the displacement file and the force data of the pre-set direction in the force value file into the spreadsheet to form a displacement-force curve, displays the coincidence of the simulation output curve and the test curve in the spreadsheet, and calculates the coincidence degree between the simulation output curve and the test curve; S6. When the degree of fit does not meet the set requirements, based on the coupling coefficient of step S3 and the degree of fit of step S5, the coupling coefficient of step S3 is adjusted; S7. Repeat steps S3 to S6 until the degree of agreement between the simulation output curve and the test curve meets the requirements.

2. The material curve automatic calibration method for CAE simulation according to claim 1, characterized in that: The highest curve in step S1 is the curve formed by fitting when the slope of the tangent line at multiple points at the end of the effective stress-strain curve is the largest, the lowest curve is the curve formed when the slope of the tangent line at the end point of the effective stress-strain curve is zero, and the effective stress-strain curve is the curve after the test curve yields to the tensile section.

3. The material curve automatic calibration method for CAE simulation according to claim 1 is characterized in that: The coupling coefficient in step S3 is a constant between 0 and 1, and the specific formula is: α＝(α1+α2) / 2 (1) Among them, α is the coupling coefficient obtained by coupling the highest curve and the lowest curve, and α1 and α2 are coupling coefficients between 0 and 1.

4. The material curve automatic calibration method for CAE simulation according to claim 1, characterized in that: In step S6, when the fit does not meet the set requirements, when the stress of the simulation curve is greater than the end stress of the test curve at the end strain of the test curve, α2=α; when the stress of the simulation curve is less than the end stress of the test curve at the end strain of the test curve, α1=α.

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