A specimen geometry validity verification method for gissmo model

Abstract

The present application relates to the technical field of plate forming, and particularly relates to a sample geometry validity verification method for a GISSMO model, a simulation model of different geometry samples is established; different geometry samples are respectively simulated (GISSMO), and displacement-force curves corresponding to sample gauges are extracted; a grid normalization curve (LCREGD) is modified, and the different geometry samples are respectively simulated again, and displacement-force curves (C2) corresponding to the sample gauges are extracted; the displacement-force curves extracted by simulation and the displacement-force curves are input into an electronic form, an absolute value of a displacement difference when a force value decreases is obtained, and is used for judging qualified simulation samples. The present application has the following advantages: traditional GISSMO simulation needs to be iterated for hundreds of times to verify sample rationality, and the present application only needs a small amount of simulation (usually 2-3 times) to quickly judge whether the sample is qualified through a grid normalization curve (LCREGD) modification comparison method, and calculation resources are saved.

Description

Technical Field

[0001] This invention relates to the field of sheet metal forming technology, and in particular to a method for validating the geometric shape of a specimen for a GISSMO model. Background Technology

[0002] In the simulation of failure behavior of metallic materials, the GISSMO (Generalized Incremental Stress State Dependent Damage Model) is widely used to predict the damage initiation and evolution process. The accuracy of this model is highly dependent on the design of the specimen geometry. However, in practical engineering applications, the following technical challenges exist: 1. Sensitivity to sample geometry: Different specimen geometries (such as the diameter of the circular hole, the radius of the transition arc, and the size of the gauge length) can lead to significant differences in local stress / strain distribution. If the design is not reasonable, the simulation results may have the following problems: Predictions made too early or too late are ineffective. The displacement-force curve deviates significantly from the experimental data; Simulation results for different mesh sizes are contradictory; 2. The grid dependency problem: Failure prediction in the GISSMO model is based on local strain accumulation, while coarse meshes underestimate the strain localization effect, leading to: When the mesh size changes, key parameters such as failure displacement and peak force fluctuate significantly. The grid parameters need to be adjusted repeatedly, which consumes a lot of computing resources (a single GISSMO simulation can take several hours to several days). 3. Limitations of existing methods: Traditional sample design relies on experience or trial and error, lacking systematic verification methods. Unable to quickly determine whether the geometry is reasonable; The optimization process requires multiple full-process simulations (usually 600-700 times), which is costly. It is difficult to guarantee the consistency of results under different grid parameters. Summary of the Invention

[0003] The purpose of this invention is to provide a method for validating the geometric shape of a specimen in a GISSMO model. This method involves: actively modifying the mesh normalization curve (LCREGD) before the full-process simulation of GISSMO to artificially stimulate mesh sensitivity; quantifying the robustness of the geometry using the absolute value of the displacement difference (δ); optimizing parameters using ANSA / LsOPT; and identifying and correcting design defects at an early stage to avoid simulation failures and resource waste caused by specimen problems in the later stages.

[0004] To achieve the above objectives, the present invention provides the following technical solution: A method for validating the geometric shape of a specimen for a GISSMO model, comprising: S1. Establish simulation models of specimens with different geometric shapes, configure (GISSMO) material card parameters, input failure equivalent plastic strain-stress triaxiality curves (LCSDG) and mesh normalization curves (LCREGD), and create spreadsheets (E1) and comparison charts of simulation output curves for each specimen (T1). S2. Simulate different geometric shapes of the specimens (GISSMO) and extract the displacement-force curves of the gauge length of the corresponding test specimens (C1). S3. Modify the grid normalization curve (LCREGD) in step S1, and perform simulation again for specimens with different geometric shapes to extract the displacement-force curve of the gauge length of the corresponding test specimen (C2). S4. Input the displacement-force curves (C1) and (C2) extracted from the simulation in steps S2 and S3 into the spreadsheet (E1) in step S1, and obtain the absolute value of the displacement difference (δ) when the force value decreases through the curve comparison chart (T1): If the absolute value of the displacement difference when the force decreases ( If the force value is less than the set threshold, the sample is a qualified simulation sample; otherwise, the characteristic parts of the sample are optimized and adjusted until the absolute value of the displacement difference when the force value decreases is ( The set threshold is met.

[0005] In S4, the absolute value of the displacement difference when the force value decreases is obtained by comparing the curves in group T1. The calculation formula is as follows: ①; In formula ①, This represents the absolute value of the displacement difference as the force decreases. This represents the displacement point where the force value on the displacement-force curve (C1) first decreases after reaching its peak. This indicates the displacement point at which the force value on the displacement-force curve (C2) first drops after reaching its peak.

[0006] Optimizing the characteristic parts of the specimen involves setting the length, width, curvature, and diameter of the circular hole of the deformed parts of specimens with different geometric shapes as optimization variables in the simulation model, configuring each specimen model in the optimization software, and performing optimization calculations.

[0007] The optimization calculation involves iteratively adjusting the offset distance of characteristic parts of the sample using optimization software. After each adjustment, the simulation is re-executed, and the absolute value of the displacement difference during force reduction is calculated. The calculation continues until the absolute value of the displacement difference (δ) meets the set threshold. At this point, the geometry of the sample is considered a qualified simulation sample.

[0008] The optimization software used is ANSA and LS-OPT. The deformation area is defined by the Morphing function of ANSA software, and the optimization calculation is performed using LS-OPT software.

[0009] The simulation model is based on LS_DYNA.

[0010] The chart format for the curve comparison group (T1) is a scatter plot with straight lines.

[0011] Compared with the prior art, the beneficial effects of the present invention are: 1. Traditional GISSMO simulation requires hundreds of iterations to verify the rationality of the sample, while the present invention uses the grid normalization curve (LCREGD) modification comparison method, which only requires a small number of simulations (usually 2 to 3 times) to quickly determine whether the sample is qualified, saving computing resources; 2. By actively modifying the mesh normalization curve (LCREGD) and calculating the absolute value of the displacement difference when the force value decreases ( This forces the exposure of the grid sensitivity defects in the specimen geometry, avoiding inconsistencies in subsequent full-process simulation results (such as GISSMO simulation) due to unreasonable design; and ensures that the optimized specimen can output consistent failure prediction results (δ≤0.2) under different grid sizes. 3. By combining ANSA's Morphing function and LS-OPT optimization settings, the geometric parameters of the specimen (such as the diameter of the circular hole, the transition arc, etc.) are automatically adjusted, eliminating the need for manual trial and error and shortening the design cycle; clear judgment criteria (such as δ≤0.2) and visual comparison tools (spreadsheet curve group T1) are provided, making the specimen verification process quantifiable and reproducible, reducing reliance on human experience; 4. By establishing a simulation model, configuring material parameters, inputting the failure equivalent plastic strain-stress triaxiality curve and mesh normalization curve, and using optimization software for optimization calculations, not only is the efficiency of sample verification improved, but also the interference of human factors is reduced, thereby improving the objectivity and accuracy of the verification results. Attached Figure Description

[0012] Figure 1 This is a comparison chart of the simulation output curves of the shear sample.

[0013] Figure 2 This is a comparison chart of the output curves from the simulation of tensile specimens.

[0014] Figure 3 This is a comparison chart of the simulation output curves of a circular notch sample.

[0015] Figure 4 This is a comparison chart of the simulation output curves of the right-angled square groove sample.

[0016] Figure 5 This is a comparison chart of the simulation output curves for the circular hole sample.

[0017] Figure 6 This is a comparison chart of the simulation output curves of the cupped sample.

[0018] Figure 7 This is a flowchart of the sample verification process. Detailed Implementation

[0019] The present invention will now be described in detail with reference to the accompanying drawings, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0020] The following embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments. Unless otherwise specified, the methods used in the following embodiments are conventional methods.

[0021] Example 1 See Figure 7 A method for validating the geometric shape of a specimen in a GISSMO model, comprising: S1. Based on LS_DYNA, establish simulation models for specimens with different geometric shapes, configure GISSMO material card parameters (including model selection parameter IDAM, failure element deletion parameter DMGTYP, damage accumulation index DMGEXP, stress attenuation threshold DCRIT, stress attenuation index FADEXP, etc.), and input the failure equivalent plastic strain-stress triaxiality curve (LCSDG) and the original mesh normalization curve (LCREGD). In the original mesh normalization curve (LCREGD), the horizontal axis represents different mesh sizes, and the vertical axis represents the normalization coefficient. The mesh size increases from small to large, such as 0.5mm, 1.0mm, 2.5mm, and 5.0mm. The normalization coefficient corresponds to a decreasing mesh size from 1.0, such as 0.5mm→1.0, 5.0mm→0.3, and the normalization coefficient for a 0.5mm mesh is 1.0. Create an Excel or WPS spreadsheet E1 file and create a set of comparison charts (T1) of the simulation output curves for each sample. The chart format for each sample should be a scatter plot with straight lines.

[0022] S2. Simulate different geometric shapes of the specimens separately (GISSMO) and extract the displacement-force curve of the original test specimen gauge length (C1).

[0023] S3. Modify the original grid normalization curve (LCREGD), modify the normalization coefficients except for 1.0, set the normalization coefficients to 1 / 2 of the original coefficients, perform GISSMO simulation on specimens with different geometries, and extract the displacement-force curve of the modified test specimen gauge length (C2).

[0024] S4. Input the original displacement-force curve (C1) and the modified displacement-force curve (C2) of the test specimen gauge length into the spreadsheet (E1) in step S1. The simulation output curve comparison chart (T1) of each specimen visually compares the matching of the original displacement-force curve (C1) and the modified displacement-force curve (C2) of the test specimen gauge length, and obtains the absolute value of the displacement difference (δ) when the force value decreases. The calculation formula is as follows: ①; In formula ①, This represents the absolute value of the displacement difference as the force decreases. This represents the displacement point where the force value first drops after reaching its peak on the original test specimen gauge length displacement-force curve (C1). This indicates the displacement point at which the force value of the displacement-force curve (C2) of the modified test specimen gauge length first drops after reaching its peak.

[0025] S5, if the absolute value of the displacement difference when the force decreases ( If the value is less than the set threshold of 0.2, it means that the geometry can adapt to different mesh parameters and the simulation results are reliable. Therefore, the sample is a qualified simulation sample and can be used for GISSMO simulation. If the absolute value of the displacement difference when the force decreases ( If the displacement difference is greater than or equal to the set threshold of 0.2, geometric defects are exposed (such as unreasonable hole diameter or transition arc design). At this point, the sample does not meet the requirements of GISSMO simulation. The characteristic parts of the sample are optimized and adjusted until the absolute value of the displacement difference is reached. The sample must meet the set threshold. Specimens optimized using a single mesh parameter may only be effective for a specific mesh. Modifying the original mesh normalization curve (LCREGD) ensures that the sample is effective under various mesh conditions.

[0026] S6. The deformation region is defined using the Morphing function of ANSA software, and optimization calculations are performed using LS-OPT software. ANSA software's Morphing function defines Morphingboxes for the necking deformation parts of specimens with different geometric shapes. The deformation offset method, offset direction, and offset distance of the characteristic parts of the necking deformation parts of specimens with different geometric shapes are set, and an OptimizationTask is established. LS-OPT is used to uniformly optimize the simulation model of all geometric specimens, and the optimization variable is the offset distance set in ANSA software. The optimization calculation is performed by iteratively adjusting the offset distance of the geometric characteristic parts of the specimen using optimization software (ANSA software and LS-OPT software). After each adjustment, the simulation and the absolute value of the displacement difference (δ) when the force value decreases are re-executed until the absolute value of the displacement difference (δ) meets the set threshold. At this time, the specimen geometry is a qualified simulation specimen.

[0027] Traditional GISSMO simulations require hundreds of iterations to verify the rationality of a sample, while this invention, through a mesh normalization curve (LCREGD) modification and comparison method, only requires a small number of simulations (usually 2-3) to quickly determine whether a sample is qualified, saving computational resources; by actively modifying the mesh normalization curve (LCREGD) and calculating the absolute value of the displacement difference when the force value decreases ( This approach forcibly exposes the grid sensitivity defects of the specimen geometry, avoiding inconsistencies in subsequent full-process simulation results (such as GISSMO simulation) due to unreasonable design; ensuring that the optimized specimen can output consistent failure prediction results (δ≤0.2) under different grid sizes; combining ANSA's Morphing function and LS-OPT optimization settings, automatically adjusting the specimen's geometric parameters (such as hole diameter, transition arc, etc.) without manual trial and error, shortening the design cycle; providing clear judgment criteria (such as δ≤0.2) and visual comparison tools (spreadsheet curve group T1), making the specimen verification process quantifiable and reproducible, reducing reliance on human experience; by establishing simulation models, configuring material parameters, inputting failure equivalent plastic strain-stress triaxiality curves and grid normalization curves, and using optimization software for optimization calculations, not only is the efficiency of specimen verification improved, but also the interference of human factors is reduced, improving the objectivity and accuracy of verification results.

Claims

1. A method for verifying the validity of specimen geometry in a GISSMO model, characterized in that, include: S1. Establish simulation models of specimens with different geometric shapes, configure (GISSMO) material card parameters, input failure equivalent plastic strain-stress triaxiality curves (LCSDG) and mesh normalization curves (LCREGD), and create spreadsheets (E1) and comparison charts of simulation output curves for each specimen (T1). S2. Simulate different geometric shapes of the specimens (GISSMO) and extract the displacement-force curves of the gauge length of the corresponding test specimens (C1). S3. Modify the grid normalization curve (LCREGD) in step S1, and perform simulation again for specimens with different geometric shapes to extract the displacement-force curve of the gauge length of the corresponding test specimen (C2). S4. Input the displacement-force curves (C1) and (C2) extracted from the simulation in steps S2 and S3 into the spreadsheet (E1) in step S1, and obtain the absolute value of the displacement difference when the force value decreases through the curve comparison chart (T1). ): If the absolute value of the displacement difference when the force decreases ( If the force value is less than the set threshold, the sample is a qualified simulation sample; otherwise, the characteristic parts of the sample are optimized and adjusted until the absolute value of the displacement difference when the force value decreases is ( The set threshold is met.

2. The method for verifying the validity of specimen geometry for GISSMO models according to claim 1, characterized in that, In S4, the absolute value of the displacement difference when the force value decreases is obtained by comparing the curves (T1). The calculation formula is as follows: ①； In formula ①, This represents the absolute value of the displacement difference as the force decreases. This represents the displacement point where the force value on the displacement-force curve (C1) first decreases after reaching its peak. This indicates the displacement point at which the force value on the displacement-force curve (C2) first drops after reaching its peak.

3. The method for verifying the validity of specimen geometry for a GISSMO model according to claim 1, characterized in that, The aforementioned optimization adjustment of the sample feature parts involves setting the length, width, curvature, and diameter of the circular hole of the deformed parts of samples with different geometric shapes as optimization variables in the simulation model, configuring each sample model in the optimization software, and performing optimization calculations.

4. The method for verifying the validity of specimen geometry for a GISSMO model according to claim 2, characterized in that, The optimization calculation involves iteratively adjusting the offset distance of the characteristic parts of the sample using optimization software. After each adjustment, the simulation is re-executed, and the absolute value of the displacement difference during the force decrease is calculated. The calculation continues until the absolute value of the displacement difference (δ) meets the set threshold. At this point, the geometry of the sample is considered a qualified simulation sample.

5. The method for verifying the validity of specimen geometry for a GISSMO model according to claim 4, characterized in that, The optimization software used is ANSA and LS-OPT. The deformation region is defined by the Morphing function of ANSA software, and the optimization calculation is performed using LS-OPT software.

6. The method for verifying the validity of specimen geometry for a GISSMO model according to claim 1, characterized in that, The simulation model described is based on LS_DYNA.

7. The method for verifying the validity of the specimen geometry for a GISSMO model according to claim 1, characterized in that, The chart format of the curve comparison chart group (T1) is a scatter plot with straight lines.

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