A method for determining the deviation of a cut seam in single-slit method stress testing

Abstract

The present invention discloses a method for determining the cut slot deviation in single-slit method stress testing. The method for determining the cut slot deviation in single-slit method stress testing includes: S1: performing a cut slot operation on the workpiece to be tested and determining the strain measurement points, where the strain measurement points include the first strain measurement point P1 and the second strain measurement point P2; S2: establishing an original coordinate system xoy with the midpoint of the line connecting P1 and P2 as the origin O; S3: establishing a deviation coordinate system x'o'y' with the center of the line connecting the two endpoints of the long side of the cut slot as the origin O'; S4: measuring a plurality of distance data from the two endpoints of the long side of the cut slot to the strain measurement points; S5: calculating the cut slot deviation angle between the x-axis of the original coordinate system and the x'-axis of the deviation coordinate system and the cut slot displacement coordinates of the origin of the deviation coordinate system in the original coordinate system according to the plurality of distance data. The present invention can improve the accuracy and efficiency of determining the cut slot deviation.

Description

Technical Field

[0001] The present invention relates to the technical field of stress testing, and particularly relates to a method for determining the offset of a cut seam in single-slit method stress testing. Background Art

[0002] Single-slit method stress testing releases the stress at the part to be measured by cutting a thin slit on the surface of the material. Two strain gauges vertically and symmetrically distributed on both sides of the cut seam are used to measure the strain released by the cut seam, and finally the working stress of the material is calculated based on the measured strain. During actual testing, the center of the cut seam may not exactly be at the midpoint O of the line connecting the strain measurement points P1 and P2, and perpendicular to P1P2. This positional deviation will cause stress testing errors. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for determining the offset of a cut seam in single-slit method stress testing, so as to improve the accuracy and efficiency of determining the offset of the cut seam.

[0004] The technical solution of the present invention to solve the above technical problems is as follows:

[0005] The present invention provides a method for determining the offset of a cut seam in single-slit method stress testing, and the method for determining the offset of a cut seam in single-slit method stress testing includes:

[0006] S1: Perform a cut seam operation on the workpiece to be measured and determine the strain measurement points, where the strain measurement points include a first strain measurement point P1 and a second strain measurement point P2;

[0007] S2: Establish an original coordinate system xoy with the midpoint of the line connecting the first strain measurement point P1 and the second strain measurement point P2 as the origin O;

[0008] S3: Establish an offset coordinate system x'o'y' with the center of the line connecting the two endpoints of the long side of the cut seam as the origin O';

[0009] S4: Measure a plurality of distance data from the two endpoints of the long side of the cut seam to the strain measurement points;

[0010] S5: Calculate the cut seam offset angle between the x-axis of the original coordinate system and the x'-axis of the offset coordinate system and the cut seam shift coordinates of the origin of the offset coordinate system in the original coordinate system according to the plurality of distance data.

[0011] Optionally, in step S4, the two endpoints of the long side of the cut seam include a cut seam endpoint D1 and a cut seam endpoint D2, and the plurality of distance data includes the distance l between the cut seam endpoint D1 and the first strain measurement point P1 11 and its distance l from the second strain measurement point P2 12 and the distance l between the cut seam endpoint D2 and the first strain measurement point P121 and the distance l between it and the second strain measurement point P2 22 .

[0012] Optionally, step S5 includes:

[0013] S51: In the original coordinate system, using the cosine law of triangles, determine the angle γ1 between the line connecting the first strain measurement point P1 and the cut end point D1 and the y-axis, the angle γ2 between the line connecting the first strain measurement point P1 and the cut end point D2 and the y-axis, and and the angle γ3 between them;

[0014] S52: If the angles γ1, γ2 and γ3 satisfy the preset conditions, go to step S53; otherwise, the deviation of the cut position is too large;

[0015] S53: According to the angles γ1, γ2, γ3 and the distance between the first strain measurement point P1 and the second strain measurement point P2, calculate the coordinates of the cut end point D1 and the cut end point D2 in the original coordinate system;

[0016] S54: According to the coordinates of the cut end point D1 and the cut end point D2, calculate the coordinates of the origin O' in the original coordinate system, and the coordinates of the origin O' in the original coordinate system are the cut shift coordinates of the origin of the offset coordinate system in the original coordinate system;

[0017] S55: According to the coordinates of the origin O' in the original coordinate system, the angle γ1 and the angle γ2, obtain the cut deflection angle.

[0018] Optionally, in step S51, the angle γ1 is:

[0019]

[0020] The angle γ2 is:

[0021]

[0022] The angle γ3 is:

[0023]

[0024] where l 11 is the distance between the cut end point D1 and the first strain measurement point P1, l 12 is the distance between the cut end point D1 and the second strain measurement point P2, l 21is the distance between the cut end point D2 and the first strain measurement point P1, l 22 is the distance between the cut end point D2 and the second strain measurement point P2, h is half of the distance between the first strain measurement point P1 and the second strain measurement point P2, a is half of the distance between the cut end point D1 and the cut end point D2, and arccos(·) is the inverse cosine function.

[0025] Optionally, in the step S52, the preset condition is:

[0026] γ3≥γ1+γ2

[0027] where γ1 is the angle between the line connecting the first strain measurement point P1 and the cut end point D1 in the original coordinate system and the y-axis, γ2 is the angle between the line connecting the first strain measurement point P1 and the cut end point D2 in the original coordinate system and the y-axis, and γ3 is the angle between the line connecting the first strain measurement point P1 and the cut end point D1 and the line connecting the first strain measurement point P1 and the cut end point D2 between them.

[0028] Optionally, in the step S54, the coordinates (x o′ , y o′ ) of the origin O' in the original coordinate system are calculated by the following method:

[0029]

[0030] where x D1 is the abscissa of the cut end point D1 and x D1 =-l 11 sinγ1, x D2 is the abscissa of the cut end point D2 and x D2 =l 12 sinγ2, y D1 is the ordinate of the cut end point D1 and y D1 =l 11 cosγ1 - h, y D2 is the ordinate of the cut end point D2 and y D2 =l 12 cosγ2 - h, l 11 is the distance between the cut end point D1 and the first strain measurement point P1, l 12 is the distance between the cut end point D1 and the second strain measurement point P2, h is half of the distance between the first strain measurement point P1 and the second strain measurement point P2, and γ1 is the angle between the line connecting the first strain measurement point P1 and the cut end point D1 in the original coordinate system and the y-axis, and γ2 is the angle between the line connecting the first strain measurement point P1 and the cut end point D2 in the original coordinate system The included angle with the y-axis.

[0031] Optionally, in step S55, the cutting slot deflection angle θ is:

[0032]

[0033] where sgn() represents the sign function and y D1 is the ordinate of the cutting slot end point D1 and y D1 = l 11 cosγ1 - h, y D2 is the ordinate of the cutting slot end point D2 and y D2 = l 12 cosγ2 - h, arccos(·) is the inverse cosine function, l 11 is the distance between the cutting slot end point D1 and the first strain measurement point P1, l 12 is the distance between the cutting slot end point D1 and the second strain measurement point P2, h is half of the distance between the first strain measurement point P1 and the second strain measurement point P2, and a is half of the distance between the cutting slot end point D1 and the cutting slot end point D2.

[0034] The present invention has the following beneficial effects:

[0035] (1) The quantitative description of the cutting slot deviation in the present invention is realized through the measurement of length, that is, the cutting slot deviation parameters (θ, x 11 , l 12 , l 21 , l 22 ) are calculated by the distances (l o′ , y o′ ) between the cutting slot end points (D1, D2) and the centers of the strain measurement points (P1, P2). High-precision data can be obtained only by common microscopes, vernier calipers, etc. for the measurement of length, and the cutting slot deviation parameters calculated therefrom are more accurate;

[0036] (2) The present invention can judge whether the cutting slot position deviation exceeds the test accuracy requirement according to whether γ3 is greater than or equal to γ1 + γ2 by the included angles (γ1, γ2, γ3) between the connecting lines of the cutting slot end points (D1, D2) and the centers of the strain measurement points (P1, P2) with the y-axis, so as to accurately judge whether the current test is valid;

[0037] (3) Through the cutting slot deviation determination method provided by the present invention, the position deviation of the actual cutting slot can be quickly and accurately determined in the single-slit method stress test, providing a theoretical basis for further evaluating the influence of the cutting slot position deviation on the precise measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1It is the flowchart of the method for determining the slit deviation in the single-slit method stress test of the present invention;

[0039] Figure 2 It is the schematic diagram of the parameter solving process under slit deviation. Specific embodiments

[0040] The principles and features of the present invention will be described below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0041] When conducting an actual test using the single-slit method stress test method, the center of the slit may not exactly be at the midpoint O of the line connecting the strain measurement points P1 and P2, and be perpendicular. This positional deviation will cause stress test errors. If this positional deviation can be quantitatively described and a stress solving theory considering the slit position deviation is constructed, the stress test errors caused by the slit deviation can be eliminated.

[0042] Therefore, the present invention provides a method for determining the slit deviation in the single-slit method stress test. Referring to Figure 1 as shown, the method for determining the slit deviation in the single-slit method stress test includes:

[0043] S1: Perform a slitting operation on the workpiece to be tested and determine the strain measurement points. Among them, the strain measurement points include the first strain measurement point P1 and the second strain measurement point P2; here, the first strain measurement point P1 and the second strain measurement point P2 are determined according to the stress extension direction, and the line connecting the two is perpendicular to the slit.

[0044] S2: Establish an original coordinate system xoy with the midpoint O of the line connecting the first strain measurement point P1 and the second strain measurement point P2 as the origin;

[0045] S3: Establish a deviation coordinate system x'o'y' with the center of the line connecting the two endpoints of the long side of the slit as the origin O';

[0046] Referring to Figure 2 as shown, in the figure, O' is the center point after the slit deviation, and its coordinates are (x o′ , y o′ ).

[0047] S4: Measure a plurality of distance data from the two endpoints of the long side of the slit to the strain measurement points;

[0048] The two endpoints of the long side of the slit include the slit endpoint D1 and the slit endpoint D2. The plurality of distance data includes the distance l 11 from the slit endpoint D1 to the first strain measurement point P1 and its distance l 12 from the second strain measurement point P2, and the distance l 21 from the slit endpoint D2 to the first strain measurement point P1and the distance l from it to the second strain measurement point P2 22 . Specifically referring to Figure 2 , D1 and D2 represent the two end points of the long side of the cut, represents the length of the cut, represents the strain measurement point spacing,

[0049] In reality, the cut is a narrow slit with material missing, and its central position is difficult to accurately determine. Therefore, the cut displacement (x o′ , y o′ ) is difficult to directly measure; the same problem exists in measuring the cut deflection angle θ. However, the end points D1 and D2 of the long side of the cut can be clearly defined, and the centers P1 and P2 of the measurement points are generally marked on the strain gauge. Therefore, the distances from the cut end points (D1, D2) to the measurement points (P1, P2) can be conveniently measured with a micrometer, a microscope ruler or a vernier caliper. Denote the distances from D1 to P1 and P2 as l 11 , l 12 , the distances from D2 to P1 and P2 as l 21 , l 22 , then the three parameters θ, x o′ and y o′ characterizing the cut position deviation can be obtained from the 4 length parameters l 11 , l 12 , l 21 , l 22 .

[0050] S5: According to the multiple distance data, calculate the cut deflection angle between the x-axis of the original coordinate system and the x'-axis of the offset coordinate system, and the cut displacement coordinates of the origin of the offset coordinate system in the original coordinate system.

[0051] Optionally, the step S5 includes:[[]]

[0052] S51: In the original coordinate system, use the cosine theorem of triangles to determine the angle γ1 between the line connecting the first strain measurement point P1 and the cut end point D1 and the y-axis, the angle γ2 between the line connecting the first strain measurement point P1 and the cut end point D2 and the y-axis, and and the angle γ3 between them;

[0053] Then, the angle γ1 is:[[]]

[0054]

[0055] The angle γ2 is:[[]]

[0056]

[0057] The included angle γ3 is as follows:

[0058]

[0059] where, l 11 is the distance between the cut end point D1 and the first strain measurement point P1, l 12 is the distance between the cut end point D1 and the second strain measurement point P2, l 21 is the distance between the cut end point D2 and the first strain measurement point P1, l 22 is the distance between the cut end point D2 and the second strain measurement point P2, h is half of the distance between the first strain measurement point P1 and the second strain measurement point P2, a is half of the distance between the cut end point D1 and the cut end point D2, and arccos(·) is the inverse cosine function.

[0060] S52: If the included angle γ1, the included angle γ2, and the included angle γ3 satisfy the preset conditions, then proceed to step S53; otherwise, the deviation of the cut position is too large;

[0061] That is, when the preset condition γ3≥γ1 + γ2 is satisfied, it means that even if there is a deviation in the cut position, its end points D1 and D2 are still located on both sides of the . If not satisfied, it means that the deviation of the cut position is too large and the test is invalid.

[0062] S53: Calculate the coordinates of the cut end point D1 and the cut end point D2 in the original coordinate system according to the included angle γ1, the included angle γ2, the included angle γ3, and the distance between the first strain measurement point P1 and the second strain measurement point P2;

[0063] Thus, the coordinates (x D1 , y D1 ) and (x D2 , y D2 ) of D1 and D2 in the xoy coordinate system are as follows:

[0064] x D1 =-l 11 sinγ1, y D1 =l 11 cosγ1 - h

[0065] x D2 =l 12 sinγ2, y D2 =l 12 cosγ2 - h

[0066] S54: Calculate the coordinates of the origin O' in the original coordinate system based on the coordinates of the cut seam endpoints D1 and D2. The coordinates of the origin O' in the original coordinate system are the cut seam shift coordinates of the origin of the offset coordinate system in the original coordinate system.

[0067] Given the coordinates of D1 and D2, the coordinates of the center point O' can be expressed as:

[0068]

[0069] where x D1 is the abscissa of the cut seam endpoint D1 and x D1 = -l 11 sinγ1, x D2 is the abscissa of the cut seam endpoint D2 and x D2 = l 12 sinγ2, y D1 is the ordinate of the cut seam endpoint D1 and y D1 = l 11 cosγ1 - h, y D2 is the ordinate of the cut seam endpoint D2 and y D2 = l 12 cosγ2 - h, l 11 is the distance between the cut seam endpoint D1 and the first strain measurement point P1, l 12 is the distance between the cut seam endpoint D1 and the second strain measurement point P2, h is half of the distance between the first strain measurement point P1 and the second strain measurement point P2, γ1 is the angle between the line connecting the first strain measurement point P1 and the cut seam endpoint D1 in the original coordinate system and the y-axis, γ2 is the angle between the line connecting the first strain measurement point P1 and the cut seam endpoint D2 in the original coordinate system and the y-axis.

[0070] S55: Obtain the cut seam deflection angle based on the coordinates of the origin O' in the original coordinate system, the angle γ1, and the angle γ2.

[0071] Reference Figure 2 shows that the cut seam deflection angle θ satisfies:

[0072] Thus, the cut seam deflection angle θ can be obtained as:

[0073]

[0074] where sgn() represents the sign function and y D1 is the ordinate of the cut seam endpoint D1 and y D1 = l 11 cosγ1 - h, yD2 is the ordinate of the cutting seam endpoint D2 and y D2 = l 12 cosγ2 - h, where arccos(·) is the inverse cosine function, l 11 is the distance between the cutting seam endpoint D1 and the first strain measurement point P1, l 12 is the distance between the cutting seam endpoint D1 and the second strain measurement point P2, h is half of the distance between the first strain measurement point P1 and the second strain measurement point P2, and a is half of the distance between the cutting seam endpoint D1 and the cutting seam endpoint D2.

[0075] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for determining the deviation of a cut seam in a single-slit method stress test, characterized in that, The method for determining the offset of the cut in the single-slit method stress test includes: S1: Perform a slitting operation on the workpiece to be measured and determine the strain measurement points, where the strain measurement points include a first strain measurement point P 1 and a second strain measurement point P 2; S2: Based on the first strain measurement point P 1 and the second strain measurement point P 2, the midpoint of the connection line is used as the origin O to establish the original coordinate system xoy ; S3: Taking the center of the line connecting the two endpoints of the long side of the cutting seam as the origin O’ to establish an offset coordinate system x'o'y' ; S4: Measuring a plurality of distance data from both ends of the long side of the cut to the strain measurement points; S5: Based on the multiple distance data, calculate the x axis of the original coordinate system and the x' seam offset angle between the axes of the offset coordinate system and the seam shift coordinates of the origin of the offset coordinate system in the original coordinate system; In the step S4, the two end points of the long side of the slit include the slit end point D 1 and the slit end point D 2. The multiple distance data include the distance between the slit end point D 1 and the first strain measurement point P 1 l 11 and the distance between it and the second strain measurement point P 2 l 12 , and the distance between the slit end point D 2 and the first strain measurement point P 1 l 21 and the distance between it and the second strain measurement point P 2 l 22 ; The step S5 includes: S51: In the original coordinate system, use the law of cosines of a triangle to determine the angle between the line connecting the first strain measurement point P 1 and the cutting slot end point D 1 and the axis, the angle between the line connecting the first strain measurement point y 1 and the cutting slot end point 2 and the P axis, and the angle between D and ; y axis, as well as the angle between , and and ; ; S52: If the included angle , the included angle and the included angle meet the preset conditions, then proceed to step S53; otherwise, the deviation of the cutting seam position is too large; S53: According to the included angle 、the included angle 、the included angle and the distance between the first strain measurement point P 1 and the second strain measurement point P 2, calculate the coordinates of the cutting slot end point D 1 and the cutting slot end point D 2 in the original coordinate system; S54: Based on the coordinates of the cutting slot end point D 1 and the cutting slot end point D 2, calculate the coordinates of the origin O’ in the original coordinate system. The coordinates of the origin O' in the original coordinate system are the cutting slot shift coordinates of the origin of the offset coordinate system in the original coordinate system; S55: According to the origin point O' coordinates in the original coordinate system, the included angle and the included angle , the cutting seam deflection angle is obtained.

2. The method for determining the deviation of the cutting seam in the single-slit method stress test according to claim 1, characterized in that, In the step S51, the included angle is The included angle is as follows: The included angle is: Wherein, l 11 is the end point of the cut D 1 and the first strain measurement point P 1's distance, l 12 is the end point of the cut D 1 and the second strain measurement point P 2's distance, l 21 is the end point of the cut D 2 and the first strain measurement point P 1's distance, l 22 is the end point of the cut D 2 and the second strain measurement point P 2's distance, h is the first strain measurement point P 1 and the second strain measurement point P 2's distance's half, a is the end point of the cut D 1 and the end point of the cut D 2's distance's half, is the arccosine function.

3. The method for determining the deviation of the cut seam in the single-slit method stress test according to claim 1, wherein In the step S52, the preset condition is: Among them, is the first strain measurement point in the original coordinate system P 1 and the cutting seam endpoint D the connecting line of and y the included angle between the axes, is the first strain measurement point in the original coordinate system P 1 and the said cutting seam endpoint D 2 of the connecting line and y the included angle between the axes, is the first strain measurement point P 1 and the said cutting seam endpoint D 1 of the connecting line and the first strain measurement point P 1 and the said cutting seam endpoint D 2 of the connecting line the included angle between them.

4. The method for determining the offset of the cut seam in the single-slit method stress test according to claim 1, wherein In the step S54, the origin point O' The coordinates in the original coordinate system Are calculated by the following method: Among them, is the abscissa of the slit endpoint D 1 and , is the abscissa of the slit endpoint D 2 and , is the ordinate of the slit endpoint D 1 and , is the ordinate of the slit endpoint D 2 and , l 11 is the said slit endpoint D the distance between the slit endpoint P 1 and the first strain measurement point l 12 is the distance between the slit endpoint D 1 and the second strain measurement point P 2, h is half of the distance between the first strain measurement point P 1 and the second strain measurement point P 2, is the angle between the line P connecting the first strain measurement point D 1 and the slit endpoint and y the axis in the original coordinate system, is the angle between the line P connecting the first strain measurement point D 1 and the said slit endpoint and y the axis in the original coordinate system.

5. The method for determining the offset of the cut seam in the single-slit method stress test according to any one of claims 1-4, characterized in that, In the step S55, the slitting deflection angle is as follows: where sgn( ) represents the sign function and , is the ordinate of the slit endpoint D 1 and , is the ordinate of the slit endpoint D 2 and , is the arccosine function, l 11 is the slit endpoint D 1 and the first strain measurement point P 1's distance, l 12 is the slit endpoint D 1 and the second strain measurement point P 2's distance, h is half of the distance between the first strain measurement point P 1 and the second strain measurement point P 2, a is half of the distance between the slit endpoint D 1 and the slit endpoint D 2.

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