A GISSMO shear test specimen optimization method

Abstract

The present invention relates to the technical field of failure modes of materials in dynamic tensile testing experiments for mechanical property analysis of steel plates, and in particular to a method for optimizing specimens for GISSMO shear tests. The present invention determines the specimen state, optimizes the specimen shape, and improves the experimental effect through finite element simulation analysis. Utilizing the finite element analysis method, LS‑DYNA is used to perform processing error analysis tests at the level of 0.01mm to 0.03mm on the original specimen tensile process. The test shows that the specimen fracture deviation is approximately within 2°. When the notch distance remains unchanged, the butt notch shape is repeatedly optimized, and the butt tip radius is gradually increased to confirm that the fracture deviation is controlled to be less than 0.5° under the same processing error level. This achieves the goal of reducing the problem of fracture direction deviation of the original specimen caused by processing errors. At the same time, LS‑DYNA is used to perform finite element analysis on the specimen tensile process, confirm the invalid deformation area during the specimen tensile process, optimize the invalid area, and simplify the specimen shape.

Description

Technical Field

[0001] The present invention relates to the technical field of failure modes of materials tested in dynamic tensile testing of steel plate mechanical properties analysis experiments, and in particular to a GISSMO shear test specimen optimization method. Background Art

[0002] With the development of digital methods and related programs, many studies on digital simulation of automobile collision problems have been carried out both at home and abroad in recent years. The biggest difficulty in the finite element calculation process lies in the selection of failure criteria and related calculation parameters.

[0003] The generalized incremental stress state-dependent damage model (GISSMO) is widely embedded in general commercial software due to its simple expression and the fact that failure parameters can be easily determined through experiments. It is used in crash simulation and stamping simulation and plays an important role in the vehicle development process.

[0004] CN 111125960 A discloses a method for optimizing the parameters of a GISSMO material failure model, which solves the technical problem of large computational complexity and difficulty in obtaining an optimal solution when calibrating model parameters using traditional experimental results. The GISSMO failure model parameters are inversely derived and calibrated based on material mechanical property test data. Optimization can be performed by simply fitting curves of several groups of experimental sampling points.

[0005] However, the GISSMO failure model requires experimental benchmarking of the material under different stress states, of which shear testing is a particularly important stress state. While current shear test specimens can meet the deformation requirements of the shear failure mode, they suffer from the following issues: 1. Specimens are difficult to manufacture and lack compatibility with some experimental equipment. 2. During the manufacturing process, the specimen fracture point can exhibit misalignment, resulting in misalignment in the experimental fracture direction, typically between 1° and 2°, affecting detection accuracy. 3. Fracture direction deflection affects measurement accuracy. Summary of the Invention

[0006] In order to overcome the shortcomings of the existing technology, a GISSMO shear test specimen optimization method is provided, which focuses on solving the problem of consistency deviation in the fracture direction of existing shear test specimens, while improving the problems of preparation difficulties and poor matching with experimental equipment, stabilizing the fracture direction, and improving measurement accuracy. In addition, the sample state can be determined through finite element simulation analysis, the sample shape can be optimized, and the experimental effect can be improved.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A GISSMO shear test specimen optimization method is used. The specimen is a thin plate with a rectangular cross section. The specimen is clamped at both ends with a clamping length of C. A strain gauge is set on one side. The strain gauge area length is 20-40 mm. The gauge length is L0. The deformation range width is b. The shear fracture zone length is a. The thickness of the experimental specimen is represented by T.

[0009] The specific steps include:

[0010] Step 1: Create a CAD model of the shear test specimen and import the created CAD model into LS-DYNA software;

[0011] Step 2: Use LS-DYNA to simulate the shear test of the specimen and generate a deformation state diagram before the mesh begins to fail;

[0012] Step 3: Under the premise of keeping the gauge length L0 unchanged, adjust the position of the sample tip interface, perform machining error correction on the sample CAD model with an accuracy level of 0.01-0.03mm, and import the CAD model with error correction at each level into LS-DYNA;

[0013] Step 4: Use LS-DYNA to perform shear test simulations on each CAD model after error correction to obtain the mesh state when the specimen fails;

[0014] Step 5: Determine the difference in fracture angle between the error-corrected and uncorrected shear test specimens at failure, as well as the length a of the shear fracture zone;

[0015] Step 6: Modify the specimen CAD model and optimize the shape of the interface.

[0016] Step 7: Same as step 3, perform machining error correction on the optimized sample CAD model;

[0017] Step 8: Similar to step 4, use LS-DYNA to simulate the optimized specimen CAD model to obtain the mesh state when the specimen fails, and determine the fracture angle and fracture length a. After comparing them with the difference determined in step 5, proceed to step 9 when the deviation is reduced to the acceptable range. If it fails, return to step 6.

[0018] Step 9: Modify the specimen CAD model, optimize the invalid deformation area, and simplify the specimen shape;

[0019] Step 10: Use LS-DYNA to simulate the shear test of the sample to confirm the impact of the streamlined sample on the fracture area. If there is no impact, proceed to step 11. If there is an impact, return to step 9.

[0020] Step 11: Organize the sample CAD model and complete the sample optimization process.

[0021] Furthermore, the qualified value of the fracture angle deviation is set to be less than 0.5°.

[0022] Furthermore, the simulation analysis of the shear experiment needs to correspond to 8 strain rates at the same time. The 8 strain rates are 0.001 / s, 0.01 / s, 0.1 / s, 1 / s, 10 / s, 100 / s, 500 / s, and 1000 / s. Technicians should compare the results under the 8 strain rates at the same time.

[0023] Furthermore, when streamlining the non-functional area of ​​the specimen, the corner areas should be chamfered, with a chamfer of R2.5 near the fracture area and a chamfer of 0.5 mm at other corners.

[0024] Furthermore, the main focus is on optimizing the shape of the sample interface and reducing the sensitivity of error correction. Specifically, the sharp corners of the interface are eliminated and the shape of the interface is gradually blunted.

[0025] Furthermore, to finally streamline the optimized area, it is necessary to simulate the shear test of the specimen through LS-DYNA to confirm the impact of the streamlined specimen on the fracture area.

[0026] Furthermore, the experimental plate is a thin plate less than 3 mm, the specimen thickness T≤3 mm; and the shear fracture length a is greater than T.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention focuses on solving the problem of fracture direction consistency deviation of existing shear test specimens, while improving the problems of preparation difficulties and poor compatibility with experimental equipment, stabilizing the fracture direction, and improving measurement accuracy. The present invention determines the specimen state and optimizes the specimen shape through finite element simulation analysis to improve the experimental effect. The present invention solves the problem of fracture direction consistency deviation of existing shear test specimens. Compared with traditional experimental specimens, the fracture consistency deviation problem of the specimens optimized by this patent is solved, the fracture direction is better, the specimen processing is more convenient, and the specimen is lighter. (Among them, using the finite element analysis method, LS-DYNA is used to perform processing error analysis tests at the level of 0.01mm to 0.03mm on the original specimen stretching process. The test shows that the specimen fracture deviation is approximately within 2°. When the notch distance remains unchanged, the shape of the butt joint notch is repeatedly optimized, and the radius of the butt joint tip is gradually increased to confirm that under the same processing error level, the fracture deviation is controlled to be less than 0.5°. This achieves the reduction of the fracture direction deviation problem caused by the processing error of the original specimen. At the same time, LS-DYNA is used to perform finite element analysis on the specimen stretching process to confirm the invalid deformation area during the specimen stretching process, optimize the invalid area, and simplify the specimen shape.) BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is the optimization flow chart of the present invention;

[0030] Figure 2 This is a schematic diagram of the sample size for the shear test of the present invention;

[0031] Figure 3 is the fracture diagram of the shear test specimen before optimization;

[0032] Figure 4 Schematic diagram of the fracture of the shear test specimen of the present invention. DETAILED DESCRIPTION

[0033] The following will be combined with examples of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the implementation case described is only one of the embodiments of the present invention, and those skilled in the art can refer to the content of this article and appropriately improve the process parameters to achieve it. It is particularly important to point out that all similar replacements and modifications are obvious to those skilled in the art, and they are all considered to be included in the present invention. The methods and applications of the present invention have been described through preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

[0034] like Figure 1 As shown, the present invention discloses a GISSMO shear test sample optimization method, specifically as follows Figure 2 As shown, a thin plate specimen with a rectangular cross section is used. Both ends of the specimen are clamped ends, the clamping length is C, a strain gauge is set on one side, the strain gauge area length is 20 to 40 mm, the gauge section length is L0, the width is b, the shear fracture zone length is a, and the thickness of the experimental specimen is represented by T.

[0035] The implementation steps are as follows:

[0036] Step 1: Create a CAD model of the shear test specimen and import the created CAD model into the LS-DYNA software.

[0037] Step 2: Use LS-DYNA to simulate the shear test of the specimen and generate a deformation state diagram before the mesh begins to fail.

[0038] Step 3: Under the premise of keeping the gauge length L0 unchanged, adjust the position of the sample tip interface, perform machining error correction on the sample CAD model with an accuracy level of 0.01 to 0.03 mm, and import the CAD models with error corrections at each level into LS-DYNA.

[0039] Step 4: Use LS-DYNA to perform shear test simulation on each CAD model after error correction to obtain the mesh state when the specimen fails.

[0040] Step 5: Determine the difference in fracture angle between the error-corrected and uncorrected shear test specimens at failure, as well as the length a of the shear fracture zone.

[0041] Step 6: Modify the specimen CAD model and optimize the shape of the interface.

[0042] Step 7: Same as step 3, perform machining error correction on the optimized sample CAD model.

[0043] Step 8: As with step 4, use LS-DYNA to simulate the optimized specimen CAD model to obtain the mesh state when the specimen fails, and determine the fracture angle and fracture length a. After comparing them with the difference confirmed in step 5, proceed to step 9 when the deviation is reduced to the qualified range. If it fails, return to step 6.

[0044] Step 9: Modify the specimen CAD model, optimize the invalid deformation area, and simplify the specimen shape.

[0045] Step 10: Use LS-DYNA to simulate the shear test of the sample to confirm the impact of the streamlined sample on the fracture area. If there is no impact, proceed to step 11. If there is an impact, return to step 9.

[0046] Step 11: Organize the sample CAD model and complete the sample optimization process.

[0047] In steps 2, 4, 8, and 10, the simulation analysis of the shear experiment must correspond to 8 strain rates at the same time. The 8 strain rates are 0.001 / s, 0.01 / s, 0.1 / s, 1 / s, 10 / s, 100 / s, 500 / s, and 1000 / s. Technicians should compare the results under the 8 strain rates at the same time.

[0048] In this optimization, the experimental plate was made of high-strength steel with a thickness of 1.5 mm and a material of DP780.

[0049] In this optimization, the initial value of a is set to a = 5 mm;

[0050] In this optimization, the corner areas should be chamfered when streamlining the non-functional areas of the specimen, with a chamfer of 2.5 mm near the fracture area and 0.5 mm at other corners.

[0051] The fracture diagram in step 4 is as follows Figure 3 As shown, the fracture diagram in step eight is as follows Figure 4 shown.

[0052] In step five, the analysis results were compared with the actual measurements, where the maximum deviation of the fracture angle was 1.723°, while the deviation of the length a after fracture was smaller.

[0053] In step six, the main focus is on optimizing the shape of the sample interface and reducing the sensitivity of error correction. Specifically, the sharp corners of the interface are eliminated and the shape of the interface is gradually blunted.

[0054] In step eight, the qualified value of the fracture angle deviation is set to be less than 0.5°. If the fracture angle deviation is less than 0.5°, the next step of optimization is entered. If it is greater than 0.5°, the process returns to step six. According to the analysis results and the actual measurement, the maximum deviation of the fracture angle is 0.422°, and the deviation of the length a after fracture is relatively small.

[0055] In step nine, the final streamlined optimized area is divided at a 45° angle after passing the interface radius of 1.5 mm. The analysis in step ten confirms that the streamlined optimized area has almost no effect on the fracture deformation.

[0056] contrast Figure 3 and Figure 4 It can be seen that the deformation state and fracture direction after optimization are significantly better than those before optimization. The experimental verification shows that the problem of fracture consistency deviation has been solved.

[0057] The present invention focuses on solving the problem of consistency deviation of the fracture direction of existing shear test specimens, while improving the problems of preparation difficulties and poor compatibility with experimental equipment, stabilizing the fracture direction, and improving measurement accuracy. The present invention determines the specimen state and optimizes the specimen shape through finite element simulation analysis to improve the experimental effect. The present invention solves the problem of consistency deviation of the fracture direction of existing shear test specimens. Compared with traditional experimental specimens, the problem of fracture consistency deviation of the specimens optimized by this patent is solved, the fracture direction is better, the specimen processing is more convenient, and the specimen is lighter.

[0058] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A GISSMO shear test sample optimization method, characterized in that: A thin plate specimen with a rectangular cross section is used. The specimen is clamped at both ends with a clamping length of C. A strain gauge is set on one side. The strain gauge area length is 20-40 mm. The gauge length is L0, the width is b, the shear fracture zone length is a, and the thickness of the test specimen is represented by T. The specific steps include: Step 1: Create a CAD model of the shear test specimen and import the created CAD model into LS-DYNA software; Step 2: Use LS-DYNA to simulate the shear test of the specimen and generate a deformation state diagram before the mesh begins to fail; Step 3: Under the premise of keeping the gauge length L0 unchanged, adjust the position of the sample tip interface, perform machining error correction on the sample CAD model with an accuracy level of 0.01-0.03mm, and import the CAD model with error correction at each level into LS-DYNA; Step 4: Use LS-DYNA to perform shear test simulations on each CAD model after error correction to obtain the mesh state when the specimen fails; Step 5: Determine the difference in fracture angle between the error-corrected and uncorrected shear test specimens in the failure state, as well as the length a of the shear fracture zone; Step 6: Modify the specimen CAD model and optimize the shape of the interface; Step 7: Same as step 3, correct the machining error of the optimized sample CAD model; Step 8. Similar to step 4, use LS-DYNA to simulate the optimized specimen CAD model to obtain the mesh state when the specimen fails, and determine the fracture angle and fracture length a. After comparing them with the difference determined in step 5, proceed to step 9 when the deviation is reduced to the acceptable range. If it fails, return to step 6. Step 9: Modify the specimen CAD model, optimize the invalid deformation area, and simplify the specimen shape; Step 10: Use LS-DYNA to simulate the shear test on the sample to confirm the impact of the streamlined sample on the fracture area. If there is no impact, proceed to step 11; if there is an impact, return to step 9; Step 11: Organize the sample CAD model and complete the sample optimization process.

2. A GISSMO shear test sample optimization method according to claim 1, characterized in that: The acceptable value of fracture angle deviation is set to be less than 0.5°.

3. A GISSMO shear test sample optimization method according to claim 1, characterized in that: The simulation analysis of the shear experiment needs to correspond to 8 strain rates at the same time. The 8 strain rates are 0.001 / s, 0.01 / s, 0.1 / s, 1 / s, 10 / s, 100 / s, 500 / s, and 1000 / s. Technicians should compare the results under the 8 strain rates at the same time.

4. A GISSMO shear test sample optimization method according to claim 1, characterized in that: When streamlining the non-functional area of ​​the specimen, the corner area should be chamfered, with a chamfer of R2.5 near the fracture area and a chamfer of 0.5mm at other corners.

5. A GISSMO shear test sample optimization method according to claim 1, characterized in that: Optimize the shape of the specimen interface, eliminate the sharp corners of the interface, and gradually blunt the shape of the interface.

6. A GISSMO shear test sample optimization method according to claim 1, characterized in that: To finally streamline the optimized area, it is necessary to perform shear test simulation on the specimen using LS-DYNA to confirm the impact of the streamlined specimen on the fracture area.

7. A GISSMO shear test sample optimization method according to claim 1, characterized in that: The experimental plate is a thin plate less than 3mm, the specimen thickness T≤3mm; the shear fracture length a is greater than T.

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