Method for testing residual stress distribution of full cross section of profile

Abstract

The invention belongs to the technical field of material residual stress testing, and particularly relates to a method for testing full-cross-section residual stress distribution of a sectional material. According to the method, grids are divided in the X-Y direction of the cross section of the profile and longitudinal cutting is performed, so that the residual stress distribution on the whole cross section can be obtained, and the mechanical property and the stability of the profile can be evaluated more comprehensively. The residual stress is calculated by directly measuring the real plastic deformation generated after the small-section profile strip is cut, dependence of high-precision cutting equipment and a complex simulation process are avoided, the test cost is remarkably reduced, and the test period is shortened. And (3) a contour method faces challenge when processing a large-size cross section, and the test precision is influenced. The method provided by the invention has better adaptability to the size of the cross section, and the residual stress can be accurately measured through meticulous grid division and longitudinal cutting regardless of the size of the cross section, so that the accuracy and reliability of the test are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of material residual stress testing, and particularly relates to a method for testing the residual stress distribution of the entire cross-section of profiles. Background Art

[0002] Due to the complex structural shape of profiles, the current methods for testing the residual stress of profiles mainly include testing techniques such as the X-ray method and the contour method. The X-ray method testing technique is only applicable to the testing of the residual stress on the surface of materials and it is difficult to obtain the residual stress distribution of the entire cross-section of the profile. For the contour method testing technique, it is necessary to cut the cross-section of the profile with high precision, and then collect the microscopic deformation generated by the release of the residual stress on the cutting surface. To achieve high-precision cutting of the cross-section, it is necessary to rely on testing equipment such as slow wire cutting, and the cross-sectional size is not easy to be too large, otherwise it is difficult to obtain a good cross-section, which will further affect the testing accuracy of the residual stress; in addition, this method requires the establishment of a finite element model and the loading of displacements for simulation, resulting in high testing accuracy requirements, expensive testing costs, and long testing cycles during the industrial application process of this method, and it is difficult to industrialize the testing technique. Therefore, there is a great need for a method for testing the residual stress of the entire cross-section of profiles that is convenient for industrial promotion and application. Summary of the Invention

[0003] Aiming at the problems existing in the prior art, the present invention provides a method for testing the residual stress distribution of the entire cross-section of profiles. The specific contents of the present invention are as follows:

[0004] A method for testing the residual stress distribution of the entire cross-section of profiles includes the following steps:

[0005] S1. Establish an X-Y-Z three-dimensional coordinate system on the cross-section of the profile, where X and Y represent two mutually perpendicular directions on the cross-section, and Z represents the direction perpendicular to the cross-section. Divide the cross-section into a plurality of grids along the X-Y direction;

[0006] S2. Cut longitudinally into the profile along the Z direction along the grid lines to obtain a plurality of small cross-section profile strips separated from each other;

[0007] S3. Calculate the residual stress of each small cross-section profile strip, and then obtain the distribution of the residual stress of the profile on the entire cross-section, where

[0008]

[0009] Wherein,

[0010] σ ijz represents the residual stress of the small cross-section profile strip in the Z direction, i represents the i-th grid in the Y direction, and j represents the j-th grid in the X direction of the cross-section;

[0011] E is the elastic modulus;

[0012] l is the depth of longitudinal cutting;

[0013] u' ijz represents the true plastic deformation amount generated at the end center point of the small cross-section profile bar on the said cross-section.

[0014] Furthermore,

[0015] u’ ijz = u ijz + Δ ijz

[0016] Wherein,

[0017] u ijz represents the deformation amount of the small cross-section profile bar in the Z direction;

[0018] Δ ijz represents the influence amount generated by the total deformation amount of the small cross-section profile bar in the X and Y directions on the shrinkage amount in the Z direction.

[0019] Furthermore,

[0020]

[0021] Wherein,

[0022] u ijx represents the deformation amount of the small cross-section profile bar in the X direction;

[0023] u ijy represents the deformation amount of the small cross-section profile bar in the Y direction.

[0024] Furthermore,

[0025]

[0026] Furthermore, the said u' ijz ≥ 1 μm.

[0027] Furthermore, when the profile is an aluminum alloy profile, the said l ≥ 70 mm.

[0028] Advantages of the present invention:

[0029] (1) Compared with the X-ray method which is only applicable to the measurement of residual stress on the material surface, the present invention can obtain the residual stress distribution on the entire cross-section by dividing the grid along the X-Y direction of the profile cross-section and performing longitudinal cutting, so as to more comprehensively evaluate the mechanical properties and stability of the profile.

[0030] (2) The contour method requires high-precision cutting and complex finite element model simulation. In contrast, the present invention calculates the residual stress by directly measuring the true plastic deformation of the small cross-section profile strip after cutting, avoiding the dependence on high-precision cutting equipment and the complex simulation process, significantly reducing the testing cost and shortening the testing cycle.

[0031] (3) The contour method faces challenges when dealing with large-size cross-sections, which affects the testing accuracy. The method of the present invention has better adaptability to the cross-section size. Regardless of the cross-section size, it can accurately measure the residual stress through detailed grid division and longitudinal cutting, thus improving the accuracy and reliability of the testing.

[0032] (4) Due to the simplified testing process and reduced cost, the technical solution of the present invention is more easily promoted and applied in the industrial environment, helping to improve the quality control level of profile production and accelerating the development and market launch speed of new products. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram showing the position of the cross-section to be measured on the profile;

[0034] Figure 2 Schematic diagram showing the sampling cross-section;

[0035] Figure 3 Schematic diagram showing the vertical matrix cutting of the cross-section;

[0036] Figure 4 Indicating the nth ij Schematic diagram showing the state of the nth cantilever beam before the release of residual stress;

[0037] Figure 5 Indicating the nth ij Schematic diagram showing the state of the nth cantilever beam after the release of residual stress;

[0038] Figure 6 Indicating the nth ij Schematic diagram showing the distribution of the residual stress of the nth cantilever beam in the Z direction;

[0039] Figure 7 Schematic diagram showing the distribution of the residual stress after quenching of the profile (in the extrusion direction of the profile, i.e., the Z direction);

[0040] Figure 8 Schematic diagram showing the position for extracting the residual stress on the cross-section;

[0041] Figure 9 Schematic diagram showing the contour map of the residual stress distribution of the cross-section of the quenched profile. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0042] The following is combined with the attached Figures 1-9The present invention will be described in detail with reference to the accompanying drawings and specific embodiments. The embodiments shown below do not limit the content of the invention described in the claims in any way. In addition, all the contents of the configurations shown in the following embodiments are not necessarily essential for the solution of the invention described in the claims.

[0043] Reference appendix Figures 1-6 , a test method for the residual stress distribution of the entire cross-section of a profile, comprising the following steps:

[0044] S1. Establish a three-dimensional X-Y-Z coordinate system on the cross-section of the profile, where X and Y represent two mutually perpendicular directions on the cross-section, and Z represents the direction perpendicular to the cross-section. Divide the cross-section into a plurality of grids along the X-Y direction;

[0045] S2. Perform longitudinal cutting into the profile along the Z direction along the grid lines to obtain a plurality of small cross-section profile strips separated from each other; that is, perform matrix cutting on the cross-section of the profile;

[0046] S3. Calculate the residual stress σ of each small cross-section profile strip ijz , and further obtain the distribution of the residual stress of the profile on the entire cross-section, where

[0047]

[0048] where,

[0049] σ ijz represents the residual stress of the small cross-section profile strip in the Z direction, i represents the i-th grid in the Y direction, and j represents the j-th grid in the X direction of the cross-section;

[0050] E is the elastic modulus;

[0051] l is the depth of longitudinal cutting;

[0052] u' ijz represents the true plastic deformation amount generated at the end center point of the small cross-section profile strip on the cross-section.

[0053] Furthermore,

[0054] u' ijz = u ijk + Δ ijz (2)

[0055] where,

[0056] u ijz represents the deformation amount of the small cross-section profile strip in the Z direction;

[0057] Δ ijz represents the influence amount of the total deformation amount of the small cross-section profile strip in the X and Y directions on the shrinkage amount in the Z direction.

[0058] Further,

[0059]

[0060] wherein,

[0061] u ijx represents the deformation of the small cross-section profile bar in the X direction;

[0062] u ijy represents the deformation of the small cross-section profile bar in the Y direction.

[0063] Further,

[0064]

[0065] Further, the u' ijz ≥ 1 μm.

[0066] Further, when the profile is an aluminum alloy profile, the l ≥ 70 mm.

[0067] In this method, the deformations of the small cross-section profile bar in the X, Y, and Z directions can be measured according to the position changes before and after cutting.

[0068] Example 1

[0069] For a certain rectangular aluminum alloy profile with a cross-section of 50×50 mm, it is quenched from 470°C into water at 20°C to obtain the residual stress distribution on the cross-section of the profile, as Figure 7 shown.

[0070] From Figure 7 it can be seen that the profile shows a symmetric distribution as a whole in the X and Y directions. Therefore, for this study, the 1 / 4 quadrant of the cross-section nodes is analyzed. Cut along the extrusion direction of the profile from the cross-section, and the cutting depth is 100 mm. The positions of each point of the cantilever beam (i.e., the small cross-section profile bar, the same below) are shown in Figure 8, and the coordinates of the cantilever beam end points before and after cutting are shown in Table 1. The elastic modulus E of the aluminum alloy material is 70 GPa.

[0071] Before matrix cutting, the coordinates of each point at the cross-section end are shown in Table 1. After matrix cutting, the coordinates of each point on the cross-section are shown in Table 2.

[0072] Table 1 Coordinates of each point on the cross-section before matrix cutting (mm)

[0073] Test point x coordinate y coordinate z coordinate P1 31.1734 43.5199 381.529 P2 43.5149 43.5148 381.545 P3 31.1731 31.1731 381.507 P4 43.5199 31.1734 381.529

[0074] Table 2 Coordinates of each point on the cross-section after matrix cutting (mm)

[0075] Test point x coordinate y coordinate z coordinate P1 31.0332 43.0772 381.542 P2 43.0202 43.0201 381.661 P3 30.9854 30.9854 381.382 P4 43.0772 31.0331 381.542

[0076] Before and after matrix cutting, the displacements of the four points P1 - P4 at the cross - section end are shown in Table 3.

[0077] Table 3 Displacements of each point on the cross - section before and after matrix cutting (mm)

[0078] Test point <![CDATA[u x > <![CDATA[u y > <![CDATA[u z > P1 -0.1402 -0.4427 0.013 P2 -0.4947 -0.4947 0.116 P3 -0.1877 -0.1877 -0.125 P4 -0.4427 -0.1403 0.013

[0079] According to the calculation formula (4) in the above text, the residual stresses of each test point (P1 - P4) can be calculated and are shown in Table 4.

[0080] Table 4 Calculation results of residual stresses of each point (MPa)

[0081] Test point Test residual stress P1 -9.9 P2 -82.9 P3 87.3 P4 -9.9

[0082] The contour map of the residual stress distribution of the profile cross - section obtained by quenching is as Figure 9 shown. As can be seen from Table 4 and Figure 9 it can be known that the coincidence degree of the residual stress distribution trends of the two is relatively good, indicating that the new residual stress test method proposed by the present invention can obtain the residual stress distribution of the cross - section.

[0083] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for testing residual stress distribution of a profile's entire cross section, characterized in that: The following steps are involved: S1, establishing an XYZ three-dimensional coordinate system on the cross section of the profile, where X and Y represent two mutually perpendicular directions on the cross section, and Z represents a direction perpendicular to the cross section, and dividing the cross section into a plurality of grids along the XY directions; S2, longitudinally cutting the profile along the grid lines along the Z direction to obtain a plurality of small-section profile strips separated from each other; S3, calculate the residual stress σ of each small cross-section profile strip ijz , and then obtain the distribution of residual stress of the profile on the whole cross section, where σ ijz represents the residual stress of the small cross-section profile strip in the Z direction, i represents the i-th grid in the Y direction, and j represents the j-th grid in the X direction of the cross section; E is the elastic modulus; l is the depth of longitudinal cutting; u' ijz It indicates the actual plastic deformation of the small-section profile strip at the center point of the end on the cross section.

2. The method for testing residual stress distribution of a profile in full cross section according to claim 1, characterized in that: in' ijz =in ijz +Δ ijz in, u ijz Indicates the deformation of the small cross-section profile in the Z direction; Δ ijz It indicates the influence of the total deformation of the small cross-section profile in the X and Y directions on the shrinkage in the Z direction.

3. A test method for residual stress distribution of a profile full cross section according to claim 2, characterized in that: in, u ijx Indicates the deformation of the small cross-section profile strip in the X direction; u ijy Indicates the deformation of the small-section profile strip in the Y direction.

4. A testing method for residual stress distribution of a profile full cross section according to claim 3, characterized in that:

5. The testing method for residual stress distribution of the entire cross section of a profile according to any one of claims 1 to 4, characterized in that: The u' ijz ≥1μm.

6. A method for testing residual stress distribution of a profile full cross section according to claim 5, characterized in that: When the profile is an aluminum alloy profile, l≥70mm.

Images