A control method, system, storage medium and electronic device for preventing instability of a biaxial tensile test

Abstract

The application provides a control method, system, storage medium and electronic device for preventing instability of a bidirectional tensile test. The method comprises the following steps: defining a plurality of loading ratios of the bidirectional tensile test according to test requirements; when the loading ratios are the same, adjusting a stress control parameter to a multiple of an initial parameter when the material strength in the X and Y tensile axis directions reaches a preset parameter adjustment range; when the loading ratios are different, adjusting the control parameter in the direction of a large-ratio tensile axis to a multiple of the initial parameter when the material strength in the direction reaches the preset parameter adjustment range, adjusting the control parameter in the direction of a small-ratio tensile axis to a multiple of the initial parameter when the material strength in the direction reaches the preset parameter adjustment range; and converting the stress control to displacement control when the material reaches the strength limit until the test is completed. The application overcomes the technical problem that the bidirectional tensile test using stress control may fail due to instability during the test, and effectively prevents the instability of the bidirectional tensile test.

Description

Technical Field

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

[0002] When studying the yield deformation characteristics of thin metal sheets, biaxial tensile tests are often used to construct different loading conditions to obtain the biaxial tensile mechanical properties of the material. Unlike uniaxial tensile tests, biaxial tensile tests often use stress-controlled loading to ensure a constant stress ratio in the two tensile directions. However, due to the plastic deformation characteristics of the material, severe stress instability often occurs before and after the start of plastic deformation in biaxial tensile tests under stress-controlled conditions, causing violent vibration of the testing machine shaft and leading to test failure. If instability occurs during the biaxial tensile test, the biaxial tensile load curve of the material will exhibit a distinct "wavy" shape, and the stress ratio will deviate significantly, failing to meet the requirements of practical engineering applications such as scientific research experiments. Therefore, developing a control method to prevent instability in biaxial tensile tests is crucial.

[0003] Currently, there is no test method to eliminate instability in biaxial tensile testing and ensure test stability. In order to obtain biaxial tensile curves with a constant stress ratio, testers can only try to obtain stable test results by repeating a large number of tests. This method has low test efficiency, and the testing machine will experience severe shaking and abnormal noise every time it becomes unstable, which seriously damages the service life of the testing machine and cannot meet the needs of scientific research and engineering. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a control method, system, storage medium, and electronic device for preventing instability in biaxial tensile tests. The invention aims to overcome the technical challenge of instability leading to test failure in stress-controlled biaxial tensile tests, and proposes a control method that can both prevent instability and ensure the safe operation of testing equipment, improve testing efficiency, and meet the practical needs of customer testing and engineering.

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

[0006] A control method for preventing instability in biaxial tensile tests includes the following steps: defining multiple loading ratios for biaxial tensile tests according to testing requirements, where the loading ratio is the ratio of stress control in the X and Y tensile directions of the specimen, where the X direction is the rolling direction of the steel plate and the Y direction is perpendicular to the rolling direction of the steel plate; for biaxial tensile tests with the same X and Y loading forces, the loading ratio is defined as the same. In this state, when the material strength in both the X and Y tensile axes reaches the preset parameter adjustment range, the stress control parameter is adjusted to a multiple of the initial parameter; for biaxial tensile tests with different X and Y loading forces, the loading ratio is defined as different. In this state, when the material strength in the tensile axis of the larger proportion reaches the preset parameter adjustment range, the control parameter in that direction is adjusted to a multiple of the initial parameter, and when the material strength in the tensile axis of the smaller proportion reaches the preset parameter adjustment range, the control parameter is adjusted to a multiple of the initial parameter; when the material reaches its ultimate tensile strength, stress control is converted to displacement control until the end of the test.

[0007] Furthermore, the initial parameter setting range for stress control in the X and Y tensile axis directions is 10 N / s to 200 N / s.

[0008] Furthermore, when the loading ratio is the same, when the material strength in both the X and Y tensile axes reaches the preset parameter adjustment range, the stress control parameter is adjusted to 200% of the initial parameter. The preset parameter adjustment range satisfies the following: the lower limit of the test parameter adjustment range with the same loading ratio = uniaxial tensile yield strength × 90% × 95%, and the upper limit of the parameter adjustment range with the same loading ratio = uniaxial tensile yield strength × 90% × 105%.

[0009] Furthermore, for the maximum loading ratio, when the material strength in the tensile axis direction of the large proportion reaches the preset parameter adjustment range, the control parameter in that direction is adjusted to 200% of the initial parameter. When the material strength in the tensile axis direction of the small proportion reaches the preset parameter adjustment range, the stress control parameter is adjusted to 200% of the initial parameter. The lower limit of the parameter adjustment range in the tensile axis direction of the large proportion is equal to uniaxial tensile yield strength × 90% × 95%, and the upper limit of the parameter adjustment range is equal to uniaxial tensile yield strength × 90% × 105%. The lower limit of the parameter adjustment range in the tensile axis direction of the small proportion is equal to uniaxial tensile yield strength × 25% × 90%, and the upper limit of the parameter adjustment range is equal to uniaxial tensile yield strength × 25% × 110%.

[0010] Furthermore, for biaxial tensile tests with other loading ratios, when the material strength in the axial direction of the large proportion of the tensile test reaches the parameter adjustment range, the stress control parameter is adjusted to 200% of the initial parameter; when the material strength in the axial direction of the small proportion of the tensile test reaches the parameter adjustment range, the stress control parameter is adjusted to 200% of the initial parameter. The lower limit of the parameter adjustment range in the axial direction of the large proportion of the tensile test is equal to uniaxial tensile yield strength × 90% × 95%, and the upper limit of the parameter adjustment range is equal to uniaxial tensile yield strength × 90% × 105%. The lower limit of the parameter adjustment range in the axial direction of the small proportion of the tensile test is equal to uniaxial tensile yield strength × 80% × 95%, and the upper limit of the parameter adjustment range is equal to uniaxial tensile yield strength × 80% × 105%.

[0011] The present invention also provides a control system for preventing instability in a biaxial tensile test, comprising:

[0012] The tensile strength monitoring unit is used to acquire tensile strength data in the X and Y directions during the biaxial tensile test.

[0013] The stress control parameter adjustment unit is used to judge different X and Y loading ratios. When the material strength in the X and Y tensile axis directions reaches the preset parameter adjustment range, the corresponding stress control parameter is adjusted to a multiple of the initial parameter.

[0014] Compared with the prior art, the present invention has the following advantages: The present invention discloses a control method for preventing instability in biaxial tensile tests, which overcomes the technical problem that instability will occur during the test in biaxial tensile tests using stress control, leading to test failure. It can effectively prevent abnormal phenomena such as instability in biaxial tensile tests, ensure the safe operation of test equipment, improve test efficiency, and meet the practical application requirements of scientific research and other engineering work. Attached Figure Description

[0015] 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.

[0016] Figure 1 This is the stable biaxial tensile test curve of the present invention.

[0017] Figure 2 The instability phenomenon collected by the test equipment when the method of this patent is not used in the test. Detailed Implementation

[0018] 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.

[0019] 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.

[0020] This embodiment discloses a control method for preventing instability in biaxial tensile tests. Based on the principle of biaxial tensile testing, it correlates the instability characteristics of materials with the control parameters of biaxial tensile testing. By designing a refined parameter control range during the test, instability in biaxial tensile testing is prevented. The specific method and steps are as follows:

[0021] Conduct uniaxial tensile tests on the required test materials to obtain the yield strength of the required test materials;

[0022] According to the testing requirements, at least 5 loading ratios for biaxial tensile tests should be defined. The loading ratios are the X and Y tensile directions of the specimen, where the X direction is the rolling direction of the steel plate and the Y direction is perpendicular to the rolling direction of the steel plate.

[0023] For biaxial tensile tests with the same loading ratio, the stress control parameters in the X and Y tensile axes are set within the range of 10 N / s to 200 N / s. Any value within this range can be selected as the initial value. The control parameters for the X and Y tensile axes are set according to the same stress control parameter range. It is defined that when the material strength in the X and Y tensile axes reaches the parameter adjustment range, the stress control parameters will be adjusted to 200% of the initial parameters. The lower limit of the parameter adjustment range for tests with the same loading ratio is defined as uniaxial tensile yield strength × 90% × 95%, and the upper limit of the parameter adjustment range for tests with the same loading ratio is defined as uniaxial tensile yield strength × 90% × 105%. It is defined that when the material reaches its strength limit, stress control will be converted to displacement control until the end of the test. In this embodiment, reaching the strength limit specifically refers to the tensile strength of the material being automatically collected by the equipment during the test. The strength gradually increases from the beginning of the tensile test, and the maximum value is the material's strength limit.

[0024] For the defined maximum loading ratio, the test parameters in the X and Y tensile axis directions are set according to the control parameter range of the same loading ratio and the same loading ratio for the biaxial tensile test. It is defined that when the material strength in the large-ratio tensile axis direction reaches the parameter adjustment range, the control parameters will be adjusted to 200% of the initial parameters; similarly, when the material strength in the small-ratio tensile axis direction reaches the parameter adjustment range, the control parameters will be adjusted to 200% of the initial parameters. The lower limit of the parameter adjustment range in the large-ratio tensile axis direction = uniaxial tensile yield strength × 90% × 95%, and the upper limit of the parameter adjustment range = uniaxial tensile yield strength × 90% × 105%. The lower limit of the parameter adjustment range in the small-ratio tensile axis direction = uniaxial tensile yield strength × 25% × 90%, and the upper limit of the parameter adjustment range = uniaxial tensile yield strength × 25% × 110%. It is defined that when the material reaches its ultimate strength, stress control will be switched to displacement control until the end of the test.

[0025] For biaxial tensile tests with other loading ratios, the test parameters in the X and Y tensile axis directions are set according to the control parameter range of the same loading ratio and biaxial tensile test. It is defined that when the material strength in the large-ratio tensile axis direction reaches the parameter adjustment range, the stress control parameter is adjusted to 200% of the initial parameter. It is also defined that when the material strength in the small-ratio tensile axis direction reaches the parameter adjustment range, the stress control parameter is adjusted to 200% of the initial parameter. The lower limit of the parameter adjustment range in the large-ratio tensile axis direction = uniaxial tensile yield strength × 90% × 95%, and the upper limit of the parameter adjustment range = uniaxial tensile yield strength × 90% × 105%. The lower limit of the parameter adjustment range in the small-ratio tensile axis direction = uniaxial tensile yield strength × 80% × 95%, and the upper limit of the parameter adjustment range = uniaxial tensile yield strength × 80% × 105%. It is defined that when the material reaches the ultimate strength, stress control is converted to displacement control until the end of the test.

[0026] When the stretching ratios in the X and Y directions are exchanged, the parameters in the X and Y stretching axis directions can be defined by exchanging the maximum loading ratio and other loading ratios as described above.

[0027] A stable biaxial tensile curve can be obtained by performing a biaxial tensile test according to the test parameters set for the two tensile axes in the current X and Y directions.

[0028] Example 1

[0029] A uniaxial tensile test was conducted on the required test material, DP980 steel, to obtain the yield strength of the required test material, which is 668 MPa.

[0030] Five biaxial tensile test loading ratios are defined according to the testing requirements: 3:1, 3:2, 3:3, 2:3, and 1:3. The loading ratio is the ratio of the stress control in the X and Y tensile directions of the specimen. The X direction is the rolling direction of the steel plate, and the Y direction is perpendicular to the rolling direction of the steel plate.

[0031] For a biaxial tensile test with a loading ratio of 3:3, the same stress control parameter of 30 N / s is set in both the X and Y tensile axes. When the material strength in both tensile axes reaches any value within the range of 570 MPa to 630 MPa, the stress control parameter is adjusted to 60 N / s. When the material reaches its ultimate strength, the stress control is converted to displacement control until the end of the test.

[0032] When the stretching ratio is 3:1, the stress control parameter is set to 30 N / s in the X-axis stretching direction and 10 N / s in the Y-axis stretching direction. It is defined that when the material strength in the X-axis stretching direction reaches any value within the range of 570 MPa to 630 MPa, the stress control parameter is adjusted to 60 N / s. It is defined that when the material strength in the Y-axis stretching direction reaches any value within the range of 149 MPa to 182 MPa, the stress control parameter is adjusted to 20 N / s. It is defined that when the material reaches the strength limit, the stress control is converted to displacement control until the end of the test.

[0033] When the stretching ratio is 3:2, the stress control parameter is set to 30 N / s in the X-axis stretching direction and 20 N / s in the Y-axis stretching direction. The stress control parameter is defined as 60 N / s when the material strength in the X-axis stretching direction reaches any value within the range of 570 MPa to 630 MPa, and as 40 N / s when the material strength in the Y-axis stretching direction reaches any value within the range of 503 MPa to 556 MPa. The stress control is then converted to displacement control until the end of the test after the material reaches its strength limit.

[0034] When the stretch ratio is 1:3, the steps for 3:1 can be followed, simply by swapping the parameters of the X and Y stretch axes; when the stretch ratio is 2:3, the steps for 3:2 can be followed, simply by swapping the parameters of the X and Y stretch axes.

[0035] A stable biaxial tensile curve can be obtained by conducting a biaxial tensile test according to the test parameters set for the current X and Y tensile axes. The biaxial tensile curve with a tensile ratio of 3:3 is shown below. Figure 1 As shown, when the method of this patent is not used in the experiment, the instability phenomenon collected by the test equipment is as follows: Figure 2 As shown, this invention can effectively prevent instability and other abnormal phenomena in biaxial tensile tests, ensure the safe operation of testing equipment, and improve testing efficiency.

[0036] 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.

[0037] 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.

[0038] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. The device embodiments described above are merely illustrative; for example, the division of units can be a logical functional division, and in actual implementation, there may be other division methods. For instance, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the displayed or discussed mutual coupling, direct coupling, or communication connection may be through some interfaces; the indirect coupling or communication connection between units or modules may be electrical or other forms.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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 control method for preventing instability in a biaxial tensile test, characterized in that, The process includes the following steps: First, define various loading ratios for biaxial tensile tests based on testing requirements. The loading ratio is the ratio of stress control in the X and Y tensile directions of the specimen, where X is the rolling direction of the steel plate and Y is perpendicular to the rolling direction. Second, for biaxial tensile tests with the same X and Y loading forces, the loading ratio is defined as the same. In this state, when the material strength in both the X and Y tensile axes reaches the preset parameter adjustment range, the stress control parameters are adjusted to a multiple of the initial parameters. Third, for biaxial tensile tests with different X and Y loading forces, the loading ratio is defined as different. In this state, when the material strength in the larger proportion of the tensile axes reaches the preset parameter adjustment range, the control parameters in that direction are adjusted to a multiple of the initial parameters. When the material strength in the smaller proportion of the tensile axes reaches the preset parameter adjustment range, the control parameters are adjusted to a multiple of the initial parameters. Finally, when the material reaches its ultimate tensile strength, stress control is switched to displacement control until the test ends.

2. The control method for preventing instability in a biaxial tensile test according to claim 1, characterized in that, The initial parameter setting range for stress control in the X and Y tensile axis directions is 10 N / s to 200 N / s.

3. The control method for preventing instability in a biaxial tensile test according to claim 1, characterized in that, When the loading ratio is the same, when the material strength in both the X and Y tensile axes reaches the preset parameter adjustment range, the stress control parameter is adjusted to 200% of the initial parameter. The preset parameter adjustment range satisfies the following: the lower limit of the test parameter adjustment range with the same loading ratio = uniaxial tensile yield strength × 90% × 95%, and the upper limit of the parameter adjustment range with the same loading ratio = uniaxial tensile yield strength × 90% × 105%.

4. The control method for preventing instability in a biaxial tensile test according to claim 1, characterized in that, For the maximum loading ratio, when the material strength in the tensile axis direction of the large ratio reaches the preset parameter adjustment range, the control parameter in that direction is adjusted to 200% of the initial parameter. When the material strength in the tensile axis direction of the small ratio reaches the preset parameter adjustment range, the stress control parameter is adjusted to 200% of the initial parameter. The lower limit of the parameter adjustment range in the tensile axis direction of the large ratio is equal to uniaxial tensile yield strength × 90% × 95%, and the upper limit of the parameter adjustment range is equal to uniaxial tensile yield strength × 90% × 105%. The lower limit of the parameter adjustment range in the tensile axis direction of the small ratio is equal to uniaxial tensile yield strength × 25% × 90%, and the upper limit of the parameter adjustment range is equal to uniaxial tensile yield strength × 25% × 110%.

5. The control method for preventing instability in biaxial tensile tests according to claim 1, for biaxial tensile tests with other loading ratios, when the material strength in the tensile axial direction of the large proportion reaches the parameter adjustment range, the stress control parameter is adjusted to 200% of the initial parameter; when the material strength in the tensile axial direction of the small proportion reaches the parameter adjustment range, the stress control parameter is adjusted to 200% of the initial parameter. The lower limit of the parameter adjustment range in the tensile axial direction of the large proportion is equal to uniaxial tensile yield strength × 90% × 95%, and the upper limit of the parameter adjustment range is equal to uniaxial tensile yield strength × 90% × 105%. The lower limit of the parameter adjustment range in the tensile axial direction of the small proportion is equal to uniaxial tensile yield strength × 80% × 95%, and the upper limit of the parameter adjustment range is equal to uniaxial tensile yield strength × 80% × 105%.

6. A control system for the control method for preventing instability in a biaxial tensile test as described in any one of claims 1 to 5, characterized in that, include: The tensile strength monitoring unit is used to acquire tensile strength data in the X and Y directions during the biaxial tensile test. The stress control parameter adjustment unit is used to judge different X and Y loading ratios. When the material strength in the X and Y tensile axis directions reaches the preset parameter adjustment range, the corresponding stress control parameter is adjusted to a multiple of the initial parameter.

7. 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 5.

8. 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 5 through the computer program.

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