A calibration method of a metal material cumulative damage model
By using uniaxial cyclic loading tests and least squares fitting, a cumulative damage model for metallic materials was constructed, which solved the problem that existing models could not accurately describe cumulative damage, improved the accuracy of CAE simulation analysis, and enhanced the accuracy of part forming and vehicle collision simulation.
Patent Information
- Application Number
- CN202310646929.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-06-02
- Publication Date
- 2025-12-23
- Estimated Expiration
- 2043-06-02
AI Technical Summary
Existing GISSMO and MMC fracture failure models cannot accurately describe the cumulative damage behavior of metallic materials, resulting in insufficient accuracy of CAE simulation analysis in predicting damage and failure during part forming and service processes.
A uniaxial cyclic loading test was adopted. By setting cyclic control conditions for strain-triggered unloading and stress-triggered loading, and combining the least squares method for fitting, a cumulative damage model of metallic materials was constructed, and the equivalent plastic strain-cumulative damage curve of the material was calibrated.
It achieves simple, fast, and low-cost fitting of cumulative damage in metal materials, improves the accuracy of CAE simulation analysis, better describes the cumulative damage of materials during deformation, and enhances the accuracy of simulation of the entire process from metal sheet to part forming to whole vehicle collision.
Smart Images
Figure CN116609213B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of material mechanics testing, in particular to a calibration method of a metal material cumulative damage model. BACKGROUND
[0002] Cumulative damage data of metal materials can be applied to CAE simulation analysis to predict damage failure conditions of parts in forming and service processes. Currently, fracture failure models such as GISSMO (generalized incremental stress-statedependent damage model) and MMC (Modified Mohr-Coulomb criterion) are commonly used in the automotive industry to predict the fracture failure of structural parts. The cumulative damage of GISSMO and MMC is calculated based on formula ② and formula ③ respectively. The cumulative damage of the two is completely obtained based on numerical optimization, without considering the actual cumulative damage of the metal material deformation process, so it often cannot accurately describe the cumulative damage behavior of the material.
[0003] Formula ②
[0004] In formula ②, D is the damage value, ΔD is the damage increment, n is the damage index, ε f is the fracture strain, ε p is the equivalent plastic strain, and Δε p is the plastic strain increment.
[0005] Formula ③
[0006] In formula ③, ΔD is the damage increment, Δε p is the plastic strain increment, and ε f is the fracture strain. SUMMARY
[0007] The present application aims to solve the above problems by providing a calibration method of a metal material cumulative damage model, which overcomes the problem that the cumulative damage increment formula used by the existing GISSMO and MMC fracture failure models cannot accurately describe the cumulative damage behavior of the material.
[0008] The technical solution adopted by the present application is as follows: a calibration method of a metal material cumulative damage model, the cumulative damage model is shown in formula ①:
[0009] Y=a×sinh(b×X-c)+d Formula ①
[0010] In formula 1, a, b, c, and d are material parameters, Y is the cumulative damage value, and X is the equivalent plastic strain value. The calibration of the cumulative damage model is based on uniaxial cyclic loading tests, and the calibration method includes the following steps:
[0011] (1) Perform uniaxial cyclic loading tests to obtain the engineering stress-strain curve of the material.
[0012] (2) Based on the obtained engineering stress-strain curve, calculate the Young's modulus E at different engineering strains.
[0013] (3) According to the Young's modulus E at different strains, calculate the cumulative damage D at different strains, and obtain the data points of cumulative damage and engineering strain.
[0014] (4) Convert the data points of cumulative damage and engineering strain into data points of cumulative damage and equivalent plastic strain.
[0015] (5) Use formula 1 to curve fit the data points of cumulative damage and equivalent plastic strain, and use the least squares method to obtain the best fitting values of the material parameters a, b, c, and d in formula 1.
[0016] Further, perform uniaxial cyclic loading tests on a universal tensile machine. The unloading control conditions are: the engineering strain of the sample increases by 0.002-0.01 (for example, it can be 0.002, 0.005, 0.006, 0.008, 0.01, etc.) to trigger unloading, and the unloading speed is 1.8-3.0 mm / min (for example, it can be 1.8 mm / min, 2.0 mm / min, 2.5 mm / min, 2.8 mm / min, 3.0 mm / min, etc.). The loading control conditions are: the load decreases to 200-800 N (for example, it can be 200 N, 300 N, 500 N, 600 N, 800 N, etc.) to trigger loading, and the loading speed is 1.8-3.0 mm / min (for example, it can be 1.8 mm / min, 2.0 mm / min, 2.5 mm / min, 2.8 mm / min, 3.0 mm / min, etc.). According to these loading and unloading conditions, perform cyclic loading and unloading until the sample breaks, and obtain the engineering stress-strain curve of the material.
[0017] As preferred, the unloading control condition is that the engineering strain of the sample is increased by 0.005 (the engineering strain for controlling unloading should not be too high or too low, for example, too high will result in less final measurement data points, thereby reducing the precision, and the condition for triggering unloading is that the engineering strain is increased by 0.002-0.01, which can meet the requirement of obtaining appropriate data points for commonly used automobile metal materials), and the unloading is triggered, and the unloading speed is 3 mm / min; the loading control condition is that the load is reduced to 500 N, and the loading is triggered, and the loading speed is 3 mm / min (the speed can be adjusted according to actual requirements, and in order to facilitate control, the speed of the loading and unloading processes is usually kept consistent).
[0018] Further, in step (2), for the obtained engineering stress-strain curve, the loading curve and the unloading curve of different cycle numbers are marked as L i and UL i respectively, the cycle number i is a natural number greater than 0, the loading curve of the first cycle is marked as L1, the unloading curve is marked as UL1, the loading curve of the second cycle is marked as L2, the unloading curve is marked as UL2, and the subsequent cycles are marked in the same manner.
[0019] Further, the linear equation y=a0+b0×x is used to perform Young's modulus fitting on the loading curve L1 of the first cycle, and the obtained b0 value is the initial Young's modulus E0.
[0020] Further, the linear equation y=a i +b i ×x is used to perform fitting on the unloading curves of all cycles, and the obtained b i value is the Young's modulus E i .
[0021] Further, the formula D i =1-E i / E0 is used to calculate the cumulative damage values of all cycles, and the data points of the cumulative damage and the engineering strain are obtained, wherein E0 and E i represent the initial Young's modulus and the Young's modulus of the i-th cycle, respectively.
[0022] Further, based on the equivalent plastic strain-engineering strain relationship curve obtained by DIC measurement or finite element simulation analysis, the data points of the cumulative damage and the engineering strain are converted into the data points of the cumulative damage and the equivalent plastic strain.
[0023] In summary, due to the adoption of the above technical solutions, the present application has the following advantages:
[0024] 1. The application can carry out uniaxial cyclic loading test on metal materials without intermittent shutdown, test the change of elastic modulus in the deformation process of metal materials, and convert the cumulative damage in the deformation process based on the continuous damage theory of metal materials, finally fit the equivalent plastic strain-cumulative damage curve of metal materials by using the cumulative damage model of the application, realize simple, fast and low-cost metal material cumulative damage fitting, and overcome the defects of no cumulative damage test data available for traditional CAE simulation analysis and inaccurate numerical optimization.
[0025] 2. The main innovation of the application is to construct a metal material cumulative damage model and design a cycle control condition, so that the metal material cumulative damage model can be calibrated through simple uniaxial cyclic loading test, the equivalent plastic strain-cumulative damage curve closer to the actual situation of metal materials is obtained, and the cumulative damage of materials in the whole deformation process is better described, so as to improve the precision of the whole process simulation from metal sheet to part forming to vehicle collision. BRIEF DESCRIPTION OF DRAWINGS
[0026] Figure 1 It is a metal material cumulative damage test and fitting method flowchart of the application based on uniaxial cyclic loading test;
[0027] Figure 2 It is a uniaxial cyclic loading test sample structure schematic diagram used in the embodiment of the application;
[0028] Figure 3 It is a uniaxial cyclic loading test stress-strain curve diagram of the embodiment of the application;
[0029] Figure 4 It is a uniaxial cyclic loading test cyclic loading and unloading curve marking schematic diagram of the embodiment of the application;
[0030] Figure 5 It is a schematic diagram of fitting Young's modulus by using linear equation in the embodiment of the application;
[0031] Figure 6 It is a Young's modulus E data point and cumulative damage D data point diagram of the embodiment of the application;
[0032] Figure 7 It is a schematic diagram of fitting cumulative damage-equivalent plastic strain curve by using cumulative damage model formula 1 in the embodiment of the application;
[0033] Figure 8 It is a comparative diagram of fitting cumulative damage-equivalent plastic strain curve by using cumulative damage model formula 1 in the embodiment of the application and cumulative damage-equivalent plastic strain curve based on MMC and GISSMO fracture model. DETAILED DESCRIPTION
[0034] The present invention will now be described in detail with reference to the accompanying drawings.
[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0036] like Figure 1 As shown, a calibration method for a cumulative damage model of metallic materials is provided, wherein the cumulative damage model is shown in formula ①:
[0037] Y=a×sinh(b×Xc)+d formula ①
[0038] In formula ①, a, b, c, and d are material parameters, Y is the cumulative damage value, and X is the equivalent plastic strain value. The calibration of the cumulative damage model is based on uniaxial cyclic loading tests, and its calibration method includes the following steps:
[0039] (1) Conduct uniaxial cyclic loading tests to obtain the engineering stress-strain curves of the material;
[0040] (2) Based on the obtained engineering stress-strain curves, calculate the Young's modulus E under different engineering strains;
[0041] (3) Calculate the cumulative damage D under different strains based on Young's modulus E under different strains, and obtain the data points of cumulative damage and engineering strain;
[0042] (4) Convert the data points of cumulative damage and engineering strain into data points of cumulative damage and equivalent plastic strain;
[0043] (5) The data points of cumulative damage and equivalent plastic strain are fitted using formula ①, and the best fitting values of material parameters a, b, c and d in formula ① are obtained by using the least squares method.
[0044] To better explain the present invention, specific embodiments are listed below:
[0045] Example
[0046] Using low-alloy high-strength steel HC340LA as the test object, the following methods were employed: Figure 2 The calibration method for the P12 specimen in GB / T 228.1 shown includes the following steps:
[0047] S1. Conduct uniaxial cyclic loading tests.
[0048] use Figure 2The uniaxial cyclic loading test was carried out on the universal tensile machine, and the unloading control condition was: strain control, 50 mm extensometer was selected, and the sample engineering strain was increased by 0.005 to trigger unloading, and the unloading speed was 3 mm / min; the loading control condition was: the load was reduced to 500N to trigger loading, and the loading speed was 3 mm / min;
[0049] According to the above loading and unloading conditions, the cyclic loading-unloading was carried out until the sample was broken, the engineering stress-strain curve of the test was recorded and saved, and Figure 3 the curve was obtained.
[0050] For the engineering stress-strain curve, L i and UL i were used to mark the loading curve and unloading curve of different cycle numbers respectively, cycle number i was a natural number greater than 0, the loading curve of the first cycle was marked as L1, and the unloading curve was marked as UL1; the loading curve of the second cycle was marked as L2, and the unloading curve was marked as UL2, and the subsequent cycles were marked in the same way. The marking diagram of the cyclic loading and unloading curve is shown in Figure 4 .
[0051] S2, Young's modulus calculation
[0052] The linear equation y=a0+b0×x was used to fit the loading curve L1 of the first cycle, and the value of b0 obtained by fitting was the initial Young's modulus E0. The linear equation y=a i +b i ×x was used to fit all the unloading curves, and the value of b i obtained by fitting was the Young's modulus E i of different cycle numbers, as shown in Figure 5 .
[0053] S3, cumulative damage value calculation
[0054] The formula D i =1-E i / E0(E0 and E i represent the initial Young's modulus and the Young's modulus of the i-th cycle respectively) was used to calculate the cumulative damage value of all cycles, and the data points of cumulative damage and engineering strain were obtained. Based on the equivalent plastic strain-engineering strain relationship curve obtained by DIC measurement or finite element simulation analysis, the data points of cumulative damage and engineering strain were converted to data points of cumulative damage and equivalent plastic strain, as shown in Figure 6 .
[0055] S4, cumulative damage model calibration
[0056] Curve fitting was performed on the cumulative damage-equivalent plastic strain data points using formula ①. The best-fit values for parameters a, b, c, and d in formula ① were obtained using the least squares algorithm. The results are as follows: Figure 7 As shown, the final fitted curve is:
[0057] D=0.00096×sinh(11.4×ε-7.1)+0.59
[0058] Effect verification
[0059] like Figure 8 As shown, the cumulative damage D-equivalent plastic strain ε relationship curves obtained from cumulative damage formulas ② and ③ based on the GISSMO and MMC fracture models only match the experimentally calculated cumulative damage D-equivalent plastic strain ε relationship curve at the final fracture location (D=1). The middle section of these curves shows a significant difference from the experimentally calculated curve. In contrast, the relationship curve calibrated based on the cumulative damage model of this invention matches the experimentally calculated curve well throughout the entire curve. Therefore, this invention provides a superior cumulative damage model and its calibration method for damage and failure simulation analysis of material forming and service processes.
[0060] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method of calibrating a metal material cumulative damage model, characterized by, The cumulative damage model is shown in formula ①: Y=a×sinh(b×X-c)+d formula ① In formula ①, a, b, c, d are material parameters, Y is the cumulative damage value, and X is the equivalent plastic strain value. Calibration of the cumulative damage model is based on uniaxial cyclic loading tests, and the calibration method includes the following steps: (1) Perform uniaxial cyclic loading tests to obtain the engineering stress-strain curve of the material. (4) Convert the cumulative damage and engineering strain data points into cumulative damage and equivalent plastic strain data points. (5) Curve fit the cumulative damage and equivalent plastic strain data points using formula ①, and obtain the best fitting values of the material parameters a, b, c, and d in formula ① using the least squares method. (2) Based on the obtained engineering stress-strain curve, the initial Young's modulus E0 and the Young's modulus E of different cycle numbers are calculated i , E i is the Young's modulus of the ith cycle; (3) Calculate the accumulated damage D at different strains according to the initial Young's modulus E0 and the Young's modulus E of different cycle times i , and obtain the data points of accumulated damage and engineering strain; Perform uniaxial cyclic loading tests on a universal tensile machine. The unloading control condition is that the engineering strain of the sample increases by 0.002-0.01, triggering unloading, and the unloading speed is 1.8-3.0 mm / min. The loading control condition is that the load decreases to 200-800 N, triggering loading, and the loading speed is 1.8-3.0 mm / min. According to this loading and unloading condition, cyclic loading and unloading are performed until the sample breaks, and the engineering stress-strain curve of the material is obtained. The unloading control condition is that the engineering strain of the sample increases by 0.005, triggering unloading, and the unloading speed is 3 mm / min. The loading control condition is that the load decreases to 500 N, triggering loading, and the loading speed is 3 mm / min.
2. The method of calibrating a metal material cumulative damage model of claim 1, wherein, Use the linear equation y=a0+b0×x to perform Young's modulus fitting on the loading curve L1 of the first cycle, and the obtained b0 value is the initial Young's modulus E0.
3. The method of claim 2, wherein the cumulative damage model is calibrated for a metal material. Based on the equivalent plastic strain-engineering strain relationship curve obtained by DIC measurement or finite element simulation analysis, convert the cumulative damage and engineering strain data points into cumulative damage and equivalent plastic strain data points.
4. The method of calibrating a metal material cumulative damage model according to any one of claims 1 to 3, characterized in that, In step (2), for the obtained engineering stress-strain curve, the loading curve and the unloading curve of different cycle numbers are respectively marked as L i and UL i , cycle number i is a natural number greater than 0, the loading curve of the first cycle is marked as L1, the unloading curve is marked as UL1, the loading curve of the second cycle is marked as L2, the unloading curve is marked as UL2, and the subsequent cycles are marked in the same manner.
5. The method of claim 4, wherein the cumulative damage model is calibrated for a metal material. 6. The method of calibrating a metal material cumulative damage model of claim 5, wherein, Using the linear equation y=a i +b i ×x fits the unloading curves for all cycles, resulting in b. i The value is Young's modulus E. i .
7. The method of claim 6, wherein the cumulative damage model is calibrated for a metal material. The formula D i =1-E i The cumulative damage value of all cycles is calculated by the formula D i E0 and Ei represent the initial Young's modulus and the Young's modulus of the i-th cycle, respectively.
8. The method of claim 7, wherein the cumulative damage model is calibrated for a metal material.
Citation Information
Patent Citations
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