A method, system, storage medium and electronic device for identifying shear force of a bidirectional tensile test

Abstract

The application provides a shear force identification method, system, storage medium and electronic device for a biaxial tensile test. The method comprises the following steps: pasting a center mark point at the center of a test sample, and pasting a plurality of auxiliary mark points corresponding to the direction of a tensile arm at a strain collection area at the center of the test sample; during the biaxial tensile test, associating the change of each mark point with the shear force in the loading process; analyzing the reliability of the test result by tracking the offset of each mark point in the test process; if the offset exceeds a preset value, adjusting the tensile test parameters to reduce the shear force to below the preset value. The application discloses a shear force identification method for a biaxial tensile test, overcomes the technical problem that the shear force in the biaxial tensile test process cannot be identified, can accurately and reliably identify the change process and loading state of the material in the test process, meets the application requirements of engineering practice, and is very suitable for the test occasions of biaxial tensile test of metal sheets.

Description

Technical Field

[0001] This invention relates to the field of biaxial tensile testing technology for thin metal sheets, and particularly to a method and system for identifying shear force in biaxial tensile testing. Background Technology

[0002] In the field of metal sheet testing, biaxial tensile testing is often used to construct complex loading states to analyze and obtain the mechanical properties of materials under service conditions. Compared with uniaxial tensile testing, biaxial tensile testing machines have four mutually orthogonal tensile arms. Before the test begins, the specimen is installed at the center of the four arms. After the test starts, loading is applied simultaneously in all four tensile directions to obtain the stress-strain curve of the material. However, when the four arms of the testing machine are loaded simultaneously, the deformation center of the specimen will deviate from the initial orthogonal center position of the testing machine. At this time, a certain shear force will be generated during the loading process, causing the specimen to deviate from the initial loading state and resulting in test failure. Therefore, researchers are eager to explore a shear force identification method for biaxial tensile testing to evaluate the stability of the test process.

[0003] Currently, the industry commonly uses three loading methods for biaxial tensile testing: beam displacement control, stress control, and strain control. These three control methods can achieve simultaneous loading in four tensile directions according to their respective control parameters. However, regardless of the control method, the central region of the specimen will deviate from the initial loading state and generate shear force after the test begins, which seriously affects the measurement results of biaxial tensile testing. Therefore, it is very important to determine a shear force identification method for biaxial tensile testing. Summary of the Invention

[0004] In view of the above-mentioned technical problems, this invention provides a method, system, storage medium, and electronic device for identifying shear force in a biaxial tensile test. The purpose of this invention is to identify and determine the shear force during the biaxial tensile test, and to provide a method for identifying shear force in a biaxial tensile test that can accurately evaluate the stability of the test and meet the actual requirements of engineering.

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

[0006] A method for identifying shear force in a biaxial tensile test includes the following steps: attaching a center marker to the center of the specimen and attaching several auxiliary markers corresponding to the direction of the tensile arm to the strain acquisition area at the center of the specimen; during the biaxial tensile test, associating the changes of each marker with the shear force during the loading process; analyzing the reliability of the test results by tracking the offset of each marker during the test; if the offset exceeds a preset value, adjusting the tensile test parameters to reduce the shear force below the preset value.

[0007] Furthermore, the number of auxiliary markers is at least four, and the four auxiliary markers are equidistant from the center marker.

[0008] Furthermore, the distance between the auxiliary marker point and the central marker point shall not exceed half the length of the strain acquisition area.

[0009] Furthermore, during the experiment, the displacement values ​​of the center marker point in the X and Y directions were recorded as time changed. When the tensile ratios in the X and Y directions of the biaxial tensile test were equal, the displacement C of the center marker point in the X and Y directions was output. x and C y Establish the test time-center marker displacement curve, when C x and C y When the maximum value of C does not exceed the preset value, the influence of the shear force generated in the current test process on the test results is considered negligible. x and C y When the maximum value exceeds the preset value, the tensile test parameters need to be adjusted to reduce the shear force to below the preset value. The horizontal tensile direction is the X direction, and the vertical tensile direction is the Y direction.

[0010] Furthermore, during the experiment, the displacement values ​​of two auxiliary marker points in the horizontal direction and two auxiliary marker points in the vertical direction were recorded as time changed. When the tensile ratios in the X and Y directions of the biaxial tensile test were not equal, the vertical displacement H of the two auxiliary marker points in the horizontal direction was output. 1y and H 2y Output the horizontal displacement V of the two auxiliary marker points in the vertical direction. 1x and V 2x Establish test time-horizontal and vertical marker displacement curves, when H 1y H 2y V 1x and V 2x When the maximum values ​​of H do not exceed the preset values, the influence of shear force on the experiment can be considered negligible. 1y H 2y V 1x and V 2x If the maximum value of any one of them exceeds the preset value, the tensile test parameters need to be adjusted to reduce the shear force below the standard value.

[0011] Furthermore, the preset value ranges from -0.02mm to 0.02mm.

[0012] This invention also discloses a shear force identification system for biaxial tensile testing, comprising:

[0013] The tensile ratio monitoring unit is used to obtain the tensile ratio in the X and Y directions during the biaxial tensile test.

[0014] The marker point displacement monitoring unit is used to acquire the displacement of each marker point in the biaxial tensile test.

[0015] The curve plotting unit is used to obtain the displacement of the marker points based on different stretching ratios in the X and Y directions, and to establish the test time-marker point displacement curve based on the displacement of the marker points.

[0016] The data processing unit is used to compare the maximum value of the marker displacement of the test time-marker displacement curve with the preset value, and adjust the test parameters of the biaxial tensile test based on the comparison results.

[0017] Compared with the prior art, the present invention has the following advantages: The present invention discloses a shear force identification method for biaxial tensile testing, which overcomes the technical problem of the inability to identify shear force during biaxial tensile testing. It can accurately and reliably identify the material change process and loading state during the test, meet the practical application requirements of engineering, and is very suitable for biaxial tensile testing of thin metal sheets. Attached Figure Description

[0018] 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.

[0019] Figure 1 This is a schematic diagram showing the location of the marking points on the sample of the present invention.

[0020] Figure 2 This refers to the change in the center point of the marker when the stretching ratio is equal according to the present invention.

[0021] Figure 3 This refers to the change in the center point of the marker when the stretching ratios are not equal according to the present 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 identifying shear force in a biaxial tensile test, comprising the following steps:

[0025] Affix one center marker to the center of the specimen. Affix four markers corresponding to the direction of the tensile arm in the strain acquisition area at the center of the specimen. These four markers in the tensile arm direction should be equidistant from the center marker, and the distance between them should not exceed half the length of the strain acquisition area. Figure 1 As shown;

[0026] The specimen is installed in the center of the testing machine, and then the specimen is clamped with the clamp on the tensile arm. The biaxial tensile test is carried out according to the loading requirements of the biaxial tensile test. At the same time, the changes in the horizontal and vertical directions of 5 marked points during the test are collected by a non-contact extensometer.

[0027] Let the horizontal tensile direction be the X direction and the vertical tensile direction be the Y direction. When the tensile ratio in the X and Y directions of the biaxial tensile test is 1:1, output the displacement C of the center marker point in the X and Y directions. x and C y Establish the test time-center marker displacement curve, such as... Figure 2 As shown, due to C x and C y If the maximum value does not exceed the standard value of 0.02 mm, the influence of the shear force generated during the current test process on the test results can be considered negligible.

[0028] When the tensile ratio in the X and Y directions of the biaxial tensile test is 2:1, the vertical displacement H of the two horizontal markers is output. 1y and H 2y Output the horizontal displacement V of the two marked points in the vertical direction. 1x and V 2x Establish test time-displacement curves for horizontal and vertical marker points, such as... Figure 3 As shown, the H collected in the current experiment 1y H2y V 1x and V 2x The maximum value is as high as 0.15 mm, and the tensile test parameters in the horizontal and vertical directions need to be adjusted to reduce the shear force below the standard value.

[0029] The standard value in this embodiment is a preset value obtained through multiple verification tests of different steel grades. Its range is -0.02mm to 0.02mm. If the center point deviation is too large, shear force will be generated, and the test curve results will be abnormal. If the deviation is too large, the testing machine is prone to instability. The shear force is monitored by setting this standard value.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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 identifying shear force in a biaxial tensile test, characterized in that, The process includes the following steps: attaching a center marker to the center of the specimen and attaching four auxiliary markers corresponding to the direction of the tensile arm to the strain acquisition area at the center of the specimen; during the biaxial tensile test, the changes of each marker are correlated with the shear force during the loading process; the reliability of the test results is analyzed by tracking the offset of each marker during the test. If the offset exceeds the preset value, the tensile test parameters are adjusted to reduce the shear force to below the preset value. The auxiliary markers are equidistant from the central marker, and the distance between the auxiliary markers and the central marker does not exceed half the length of the strain acquisition area; During the experiment, the displacement values ​​of the center marker point in the X and Y directions were recorded as time progressed. When the X and Y stretch ratios of the biaxial tensile test were 1:1, the displacement C of the center marker point in the X and Y directions was output. x and C y Establish the test time-center marker displacement curve, when C x and C y When the maximum value of C does not exceed the preset value, the influence of the shear force generated in the current test process on the test results is considered negligible. x and C y When the maximum value exceeds the preset value, the tensile test parameters need to be adjusted to reduce the shear force to below the preset value. The horizontal tensile direction is the X direction, and the vertical tensile direction is the Y direction. Record the displacement values ​​of two auxiliary marker points in the horizontal direction and two auxiliary marker points in the vertical direction as time changes. When the tensile ratio in the X and Y directions of the biaxial tensile test is 2:1, output the vertical displacement H of the two auxiliary marker points in the horizontal direction. 1y and H 2y Output the horizontal displacement V of the two auxiliary marker points in the vertical direction. 1x and V 2x Establish test time-horizontal and vertical marker displacement curves, when H 1y H 2y V 1x and V 2x When the maximum values ​​of H do not exceed the preset values, the influence of shear force on the experiment can be considered negligible. 1y H 2y V 1x and V 2x If the maximum value of any one of them exceeds the preset value, the tensile test parameters need to be adjusted to reduce the shear force to below the standard value; The preset value ranges from -0.02mm to 0.02mm.

2. A shear force identification system for a biaxial tensile test implementing the method of claim 1, characterized in that, include: The tensile ratio monitoring unit is used to obtain the tensile ratio in the X and Y directions during the biaxial tensile test. The marker point displacement monitoring unit is used to acquire the displacement of each marker point in the biaxial tensile test. The curve plotting unit is used to obtain the displacement of each marker point based on different stretching ratios in the X and Y directions, and to establish a test time-marker point displacement curve based on the displacement of the marker points. The data processing unit is used to compare the maximum displacement of each marker point on the test time-marker displacement curve with the preset value, and adjust the test parameters of the biaxial tensile test based on the comparison results.

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