A method, system, storage medium, and electronic device for determining biaxial tensile test curves.

Abstract

This invention provides a method for determining biaxial tensile test curves. The method includes the following steps: setting the required biaxial tensile ratio for stress-controlled testing according to experimental requirements; determining the constitutive equation of the metal sheet under service conditions according to application requirements; performing incremental differentiation calculations on the constitutive equation to solve for the relationship between the strain component expressions in both directions and the tensile ratio; calculating the tensile ratio under strain control according to the tensile ratio set in step 1 and the strain component expressions calculated in step 3; conducting biaxial tensile tests on the material according to the stress-controlled tensile ratio set in step 1 and the strain-controlled tensile ratio calculated in step 4 to obtain biaxial tensile curves under different control methods; comparing the test curves of the corresponding tensile ratios under the two control methods to determine whether the biaxial tensile performance of the material is strain-controlled or stress-controlled. This invention overcomes the technical difficulty of not being able to determine the results of biaxial tensile stress-controlled and strain-controlled tests.

Description

Technical Field

[0001] This invention relates to the field of biaxial tensile testing technology for thin metal sheets, and more particularly to a method, system, storage medium, and electronic device for determining biaxial tensile test curves. Background Technology

[0002] In the field of metal sheet testing, biaxial tensile testing is frequently required to obtain the mechanical response of materials under complex loading conditions. Currently, the industry's conventional testing methods for biaxial tensile testing generally include three loading methods: beam displacement, stress control, and strain control. However, the biaxial tensile properties obtained using different loading methods vary significantly, making it difficult to accurately determine the material's biaxial tensile properties. Therefore, testing personnel are eager to explore a method for determining the biaxial tensile test curve to understand the material's biaxial tensile properties.

[0003] The most common test method for biaxial tensile testing is beam displacement control. Although this loading method is relatively simple to operate, the test process is not very stable and cannot meet the actual application needs of customers such as automobile OEMs. At present, with the improvement of test equipment, stress control and strain control tests have gradually attracted attention. Both of these methods can stably complete biaxial tensile tests, but the test results for the same tensile ratio are not quite the same. Therefore, it is very important to determine a method for judging the biaxial tensile test curve. Summary of the Invention

[0004] In response to the aforementioned technical problems, a method, system, storage medium, and electronic device for determining biaxial tensile test curves are provided.

[0005] The technical means employed in this invention are as follows:

[0006] A method for determining the biaxial tensile test curve includes the following steps:

[0007] Step 1: Set the biaxial tensile ratio required for the stress control test according to the test requirements;

[0008] Step 2: Determine the constitutive equations for the metal sheet under service conditions according to application requirements;

[0009] Step 3: Perform incremental differentiation calculations on the selected constitutive equations to solve for the relationship between the strain component expressions in the two directions and the stretching ratio.

[0010] Step 4: Calculate the strain-controlled strain ratio according to the strain component expression in Step 3, based on the strain ratio set in Step 1.

[0011] Step 5: Perform a biaxial tensile test on the material according to the stress-controlled tensile ratio set in Step 1 and the strain-controlled tensile ratio calculated in Step 4, and obtain biaxial tensile curves under different control methods.

[0012] Step 6: Compare the test curves of the corresponding tensile ratios under the two control methods. If the maximum stress difference and the maximum strain difference of the curves do not exceed the corresponding preset values, the test result of stress control is considered to be the biaxial tensile property of the material. Otherwise, the test result of strain control is considered to be the biaxial tensile property of the material.

[0013] Furthermore, in step 6, the maximum stress difference and maximum strain difference of the curve are calculated based on the following formulas: Maximum stress difference of the curve = (stress control limit stress - strain control limit stress) / strain control limit stress, Maximum strain difference = (stress control limit strain - strain control limit strain) / strain control limit strain.

[0014] Furthermore, the maximum stress difference and maximum strain difference of the curves do not exceed the corresponding preset values, specifically: the maximum stress difference of the curves does not exceed ±5%, and the maximum strain difference does not exceed ±1%.

[0015] The present invention also provides a system for determining the biaxial tensile test curve, comprising:

[0016] Stress-strain conversion element: used to substitute the biaxial tensile ratio parameters required for the test into the constitutive equation of the metal sheet under service conditions to obtain the strain ratio;

[0017] The data judgment unit is used to obtain the maximum stress difference and maximum strain difference in stress and strain experiments, compare the maximum stress difference and maximum strain difference with preset values, and obtain the test results.

[0018] Compared with the prior art, the present invention has the following advantages: The present invention discloses a method for determining the biaxial tensile test curve, which overcomes the technical problem that the results of biaxial tensile stress control and strain control tests cannot be determined. It can accurately and reliably determine the biaxial tensile curve of the material, meet the practical application requirements of engineering, and is very suitable for biaxial tensile testing of thin metal sheets. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1These are the test results for the same stretch ratio under different control methods according to the present invention.

[0021] Figure 2 The results show the comparison of bidirectional stretching curves of this invention. Detailed Implementation

[0022] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0023] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0024] This embodiment discloses a method for determining the biaxial tensile test curve. Based on the technical parameters of the biaxial tensile test under stress control, it combines the stress-strain component relationship under stress control and strain control. By analyzing the mechanical component relationship under the two control methods, the key test parameters are determined, thereby accurately determining the biaxial tensile curve of the material. The specific method and steps are as follows:

[0025] The bidirectional tensile ratio required for the stress control test is set according to the test requirements. The tensile ratio in the two directions is generally an integer.

[0026] The service condition of thin metal sheets is generally a plane stress state. The constitutive equation under the required plane stress condition is determined according to the application requirements.

[0027] Incremental differentiation calculations were performed on the selected constitutive equations to solve for the relationship between the strain component expressions in the two directions and the stretching ratio.

[0028] Based on the stretching ratio set in step 1, the stretching ratio under strain control is calculated according to the strain component expression in step 3.

[0029] The material was subjected to a biaxial tensile test according to the stress-controlled tensile ratio set in step 1 and the strain-controlled tensile ratio calculated in step 4, and biaxial tensile curves under different control methods were obtained.

[0030] Compare the test curves for the corresponding tensile ratios under the two control methods. If the maximum stress difference of the curve = (stress control limit stress - strain control limit stress) / strain control limit stress does not exceed ±5%, and the maximum strain difference = (stress control limit strain - strain control limit strain) / strain control limit strain does not exceed ±1%, then the test result of stress control is considered to be the biaxial tensile property of the material. Otherwise, the test result of strain control is considered to be the biaxial tensile property of the material.

[0031] Example 1

[0032] The required biaxial tensile ratio, σ, is set according to the experimental requirements for the stress control test. X :σ Y = 1:P, where P is an integer, and specific ratios include 4:0, 4:4, 2:4, 3:4, 1:4, 4:1, 4:2, 4:3, 0:4; 4:

[0033] The service condition of thin metal sheets is generally a plane stress state. The Mises constitutive equation under the required plane stress conditions is determined according to user requirements.

[0034] Incremental derivatives were performed on the selected constitutive equations, since σ Y =Pσ X The relationship between the strain component expressions in the two directions and the stretching ratio is obtained by solving the expression ε1:ε2=(P-2):(1-2P);

[0035] Based on the stretching ratio set in step 1, the stretching ratio under strain control is calculated according to the strain component expression in step 3. The stress ratios 4:0, 4:4, 2:4, 3:4, 1:4, 4:1, 4:2, 4:3, and 0:4 correspond to the strain ratios -8:4, 4:4, 0:-6, 2:5, 2:-7, -7:2, -6:0, 5:2, and 4:-8, respectively.

[0036] Biaxial tensile tests were conducted on DP980 steel according to the stress-controlled tensile ratio set in step 1 and the strain-controlled tensile ratio calculated in step 4, and biaxial tensile curves under different control methods were obtained.

[0037] A comparison of the test curves for the corresponding tensile ratios under the two control methods shows that, for example... Figure 2As shown, under the two control conditions, the maximum stress difference of the curve is (836-807) / 807 = 3.6%, and the maximum strain difference is (0.0182-0.018077) / 0.018077 = 0.68%, which means that... Figure 1 The test results under medium stress control are the biaxial tensile properties of the material.

[0038] The sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0039] In the above embodiments of the present invention, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0040] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. Among them, the device embodiments described above are only exemplary. For example, the division of the units can be a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of units or modules, which can be electrical or other forms.

[0041] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0042] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0043] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, read-only memory (ROM), random access memory (RAM), portable hard drives, magnetic disks, or optical disks.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for determining the curve of a biaxial tensile test, characterized in that, Includes the following steps: Step 1: Set the biaxial tensile ratio required for the stress control test according to the test requirements; Step 2: Determine the constitutive equations for the metal sheet under service conditions according to application requirements; Step 3: Perform incremental differentiation calculations on the selected constitutive equations to solve for the relationship between the strain component expressions in the two directions and the stretching ratio. Step 4: Calculate the strain-controlled strain ratio according to the strain component expression in Step 3, based on the strain ratio set in Step 1. Step 5: Perform a biaxial tensile test on the material according to the stress-controlled tensile ratio set in Step 1 and the strain-controlled tensile ratio calculated in Step 4, and obtain biaxial tensile curves under different control methods. Step 6: Compare the test curves of the corresponding tensile ratios under the two control methods. If the maximum stress difference and the maximum strain difference of the curves do not exceed the corresponding preset values, the test result of stress control is considered to be the biaxial tensile property of the material. Otherwise, the test result of strain control is considered to be the biaxial tensile property of the material.

2. The method for determining the biaxial tensile test curve according to claim 1, characterized in that, In step 6, the maximum stress difference and maximum strain difference of the curve are calculated based on the following formulas: Maximum stress difference of the curve = (stress control limit stress - strain control limit stress) / strain control limit stress, Maximum strain difference = (stress control limit strain - strain control limit strain) / strain control limit strain.

3. The method for determining the biaxial tensile test curve according to claim 1, characterized in that, The maximum stress difference and maximum strain difference of the curves do not exceed the corresponding preset values, specifically: the maximum stress difference of the curves does not exceed ±5%, and the maximum strain difference does not exceed ±1%.

4. A system for determining the biaxial tensile test curve according to any one of claims 1 to 3, characterized in that, include: Stress-strain conversion element: used to substitute the biaxial tensile ratio parameters required for the test into the constitutive equation of the metal sheet under service conditions to obtain the strain ratio; The data judgment unit is used to obtain the maximum stress difference and maximum strain difference in stress and strain experiments, compare the maximum stress difference and maximum strain difference with preset values, and obtain the test results.

5. A storage medium, characterized in that, The storage medium includes a stored program, wherein when the program is executed, it performs the method described in any one of claims 1 to 3.

6. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, The processor executes the method described in any one of claims 1 to 3 by running the computer program.

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