A measuring device and method for detecting residual stress of transparent polymer material

Abstract

The present invention relates to a measuring device for detecting residual stress of transparent polymer materials and a method for measuring residual stress. The measuring device is composed of a measuring platform, a light source, a first polarizer, a first quarter wave plate, a ball screw device, a laser, a reflector device, a second quarter wave plate, a second polarizer, a CCD camera and a transparent polymer material model. The measuring device of the present invention is provided with a plurality of slideways on the measuring platform, and a plurality of optical components involved in the photoelastic method and the astigmatism method are assembled with the slideways in sequence by installing a magnetic base. During the measurement process, the corresponding optical components can be removed or the corresponding positions of the optical components in the slideways can be adjusted according to different measuring methods, thereby meeting the requirements of different measuring methods.

Description

Technical Field

[0001] The invention relates to the field of stress measurement, and in particular to a measuring device for detecting residual stress of a transparent polymer material and a method for measuring residual stress. Background Art

[0002] Residual stress will be generated in the process of material preparation or processing. The residual stress of the material has an important influence on its reliability and service life. The influence of residual stress can be roughly divided into: the influence on material properties such as static strength, brittle failure, stress corrosion cracking and fatigue, and the influence on dimensional deviation after processing. How to take appropriate measures to adjust the residual stress or improve its distribution, reduce or eliminate the adverse effects of residual stress on material properties is an important topic in the study of residual stress of materials.

[0003] The test of residual stress is a prerequisite for adjusting the residual stress distribution and reducing or eliminating residual stress. At present, the residual stress in the material can be calculated by the finite element method, but due to the complexity and unpredictability of the stress conditions, temperature field and boundary conditions, the calculation results of the finite element method are unreliable. The experimental method can make up for the shortcomings of the finite element method. The existing residual stress test experimental methods mainly include damage detection method and non-destructive testing method. The blind hole method is often used for the damage detection of residual stress. This type of test method requires machining, so the material cannot be used any more. In addition, additional machining stress will be introduced during drilling, which affects the detection accuracy. The non-destructive testing of residual stress is a detection technology that uses a medium to realize the residual stress test. It can keep the prototype of the tested piece, so the tested piece can continue to be used, and the test accuracy is high. For example, the physical measurement method of residual stress: X-ray and magnetic methods, which do not need to separate or divide the material, can directly obtain the residual stress. The physical method can measure both macroscopic residual stress and microscopic residual stress. In addition, acoustic, optical, Raman scattering, and hardness change methods can also detect residual stress.

[0004] In addition, due to the birefringence effect of transparent polymer materials, the photoelastic method can be applied to the non-destructive detection of residual stress in transparent polymer materials. However, after the photoelastic method tests the order and isoclinic angle of the equidistant line fringes, stress separation is required to calculate the stress components. The commonly used principal stress separation method is the shear stress difference method. This method is relatively cumbersome to calculate and requires the determination of boundary conditions. In the residual stress test process, sometimes it is more complicated to determine the boundary stress, or even impossible to determine, and calculation errors will be introduced in the calculation process. The principle of the astigmatism method is similar to that of the photoelastic method. Both use the birefringence effect of transparent materials. The difference is that the photoelastic method uses transmitted light to form interference fringes, while the astigmatism method uses scattered light. However, when the astigmatism method tests the internal stress deep from the surface of the material model, the collected astigmatism fringe pattern will be affected by the intensity of the scattered light, and even cannot be tested. Therefore, the existing photoelastic method and astigmatism method cannot achieve reliable and accurate stress measurement of transparent polymer materials. Summary of the invention

[0005] Based on the above-mentioned defects when the existing astigmatism method and photoelastic method are used to measure the stress of transparent polymer materials, the technical problem to be solved by the present invention is to provide a measuring device and a measuring method that can measure the residual stress of transparent polymer materials by combining the photoelastic method and the astigmatism method.

[0006] The technical solution adopted by the present invention to solve the above technical problems is: a measuring device for detecting residual stress of transparent polymer materials, comprising a measuring platform, a light source, a first polarizer, a first 1 / 4 wave plate, a ball screw device, a laser, a reflector device, a second 1 / 4 wave plate, a second polarizer, a CCD camera and a transparent polymer material model, wherein:

[0007] The measuring platform is provided with a plurality of slideways;

[0008] The light source, the first polarizer, the first 1 / 4 wave plate, the second 1 / 4 wave plate, the second polarizer and the CCD camera are respectively assembled in sequence in the slideway on the measuring platform through the magnetic base, and the light source, the first polarizer, the first 1 / 4 wave plate, the second 1 / 4 wave plate, the second polarizer and the CCD camera can be separated from the slideway or their positions in the slideway can be adjusted by moving the magnetic base;

[0009] The ball screw device is arranged on a measuring platform between two slideways for assembling the first 1 / 4 wave plate and the second 1 / 4 wave plate;

[0010] A polarizing plate is provided at the front end of the laser, and the laser can be driven to move up and down by a ball screw device;

[0011] The reflector device is used to reflect the laser light scattered out of the transparent polymer material model, and is fixedly mounted with the ball screw device.

[0012] In the above scheme, the laser is fixed to the ball screw device through a connecting plate, the reflector device is composed of a reflective lens and a grooved steel block, the grooved steel block is fixed to the ball screw device through bolts, and the reflective lens is at an angle of 45° to the horizontal direction.

[0013] In the above solution, the reflective lens is embedded in the channeled steel block by means of groove matching, and the reflective lens and the channeled steel block are bonded together.

[0014] In the above solution, the light source, the first polarizer, the first 1 / 4 wave plate, the second 1 / 4 wave plate, the second polarizer and the CCD camera are fixed to the magnetic base via connecting rods respectively.

[0015] The present invention also provides a method for measuring residual stress of a transparent polymer material based on the above-mentioned measuring device, comprising the following steps:

[0016] In the first step, the light source, the first polarizer, the first 1 / 4 wave plate, the second 1 / 4 wave plate, and the second polarizer are removed or moved to one side of the slide. The laser generates 45° polarized light through the polarizer installed at the front end. The transparent polymer material model is placed in front of the laser, the laser and the ball screw device are turned on, and the laser is incident on the transparent polymer material model. The CCD camera collects images in the reflector device; at the same time, the ball screw device drives the laser to scan up and down, and the light intensity is superimposed during the scanning process. Finally, the light and dark scattered light interference fringe pattern is obtained. The stress calculation can be performed based on the interference fringe pattern. The stress component σ at each point inside the specimen y The calculation formula of the fringe order is as follows:

[0017]

[0018] Where: n x is the fringe order in the scattered light interference fringe pattern when the incident light is incident along the x-axis; f σ is the stripe value of the material; d is the model thickness;

[0019] In the second step, the light source, the first polarizer, the transparent polymer material model, the second polarizer and the CCD camera are adjusted to be coaxial, and the plane polarized light field is obtained by rotating the first polarizer and the second polarizer to adjust the optical path. The mixed fringe pattern of isoclinic lines and isoclinic lines is collected by the CCD camera, and the two polarizers are rotated at the same time to change the isoclinic line fringe pattern. The rotation angle of the two polarizers is the isoclinic angle θ of each point on the corresponding isoclinic line;

[0020] The third step is to adjust the light source, the first polarizer, the first quarter wave plate, the transparent polymer material model, the second quarter wave plate, the second polarizer and the CCD camera to an axis, and adjust the optical path by rotating the first polarizer and the second polarizer to obtain a circularly polarized light field. The arithmetic stripe pattern can be obtained from the circular polarization square. The order n of the arithmetic stripes at each point can be measured by the Tardy compensation method. The stress at each point can be calculated by the shear stress difference method from the equal inclination angle and the arithmetic stripe order n. The calculation formula is as follows:

[0021]

[0022] Where: n is the order of the equidistant fringe; f σ is the stripe value of the material; d is the model thickness;

[0023] Using the principal stress difference, the isocline angle θ and the stress component σ calculated in the first step y , the other two stress components τ are calculated xy and σ x ;

[0024]

[0025]

[0026] Where: θ is the isoclinic angle; n is the order of the equidistant line fringes; f σ is the stripe value of the material; d is the model thickness; n x It is the fringe order in the scattered light interference fringe pattern when the incident light is incident along the x-axis.

[0027] Compared with the prior art, the present invention has the following advantages and effects:

[0028] 1. The transparent polymer material residual stress measuring device described in the present invention is provided with a plurality of slideways on the measuring platform, and a plurality of optical components involved in the photoelastic method and the astigmatism method are assembled with the slideways in sequence by installing a magnetic base. During the measuring process, the corresponding optical components can be removed or the corresponding positions of the optical components in the slideways can be adjusted according to the measuring requirements, thereby meeting the requirements of different measuring methods.

[0029] 2. The measuring device described in the present invention can be used for non-destructive testing of residual stress of transparent polymer materials by photoelastic method, and can also be used for non-destructive testing of residual stress of transparent polymer materials by astigmatism method. At the same time, it can also be used to measure the residual stress of transparent polymer materials by combining photoelastic method and astigmatism method. Various different measuring methods can be realized by a set of devices, and the conversion between different measuring methods is reliable and convenient.

[0030] 3. The transparent polymer material residual stress measuring device described in the present invention connects a laser to a ball screw. When stress is measured using the astigmatism method, the ball screw can drive the laser to scan the transparent polymer material model up and down, and light intensity is superimposed during the scanning process. Compared with the existing measuring device that uses a laser to directly irradiate the material model, the stripes are free of distortion and there is no need to use a high-power laser.

[0031] 4. The measurement method of the present invention combines the astigmatism method and the photoelastic method to measure the stress of transparent polymer materials. On the one hand, it can overcome the cumbersomeness and disadvantages of using the photoelastic method directly to measure stress, which requires stress separation to calculate the stress components; on the other hand, it can also avoid the problem that when the astigmatism method is used directly to measure stress, when the internal stress of the test material model is deep from the surface, the collected astigmatism fringe pattern will be affected by the scattered light intensity, and even the test cannot be performed. In addition, the measurement and calculation method of the present invention can quickly and accurately measure the residual stress of the transparent polymer material model. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0033] Figure 1 This is a top view of the measuring device described in Example 1 of the present invention.

[0034] Figure 2 This is a side view of the measuring device described in Example 1 of the present invention.

[0035] Figure 3 , Figure 4 This is an optical principle diagram of the measurement method described in Example 4 of the present invention.

[0036] Explanation of reference numerals: 1. Measuring platform; 2. Light source; 3. First polarizer; 4. First 1 / 4 wave plate; 5. Transparent polymer material model; 6. Magnetic base; 7. Second 1 / 4 wave plate; 8. Second polarizer; 9. CCD camera; 10. Reflector device; 11. First slide; 12. Second slide; 13. Third slide; 14. Fourth slide; 15. Fifth slide; 16. Sixth slide; 17. Laser; 18. Ball screw device; 19. Connecting rod; 20. Connecting plate; 21. Bolt; 22. Polarizer. DETAILED DESCRIPTION

[0037] The present invention is further described in detail below in conjunction with embodiments. The following embodiments are for explanation of the present invention but the present invention is not limited to the following embodiments.

[0038] Example 1: Figures 1 to 2 As shown, a measuring device for detecting residual stress of a transparent polymer material comprises a measuring platform 1, a light source 2, a first polarizer 3, a first 1 / 4 wave plate 4, a ball screw device 18, a laser 17, a reflector device 10, a second 1 / 4 wave plate 7, a second polarizer 8, a CCD camera 9 and a transparent polymer material model 5, wherein:

[0039] The measuring platform 1 is provided with a first slide 11, a second slide 12, a third slide 13, a fourth slide 14, a fifth slide 15, and a sixth slide 16 in sequence;

[0040] The light source 2, the first polarizer 3, the first 1 / 4 wave plate 4, the second 1 / 4 wave plate 7, the second polarizer 8 and the CCD camera 9 are respectively assembled in the first slide 11, the second slide 12, the third slide 13, the fourth slide 14, the fifth slide 15 and the sixth slide 16 on the measuring platform 1 in sequence through the magnetic base 6. The light source 2, the first polarizer 3, the first 1 / 4 wave plate 4, the second 1 / 4 wave plate 7, the second polarizer 8 and the CCD camera 9 can be separated from the slide or their positions in the slide can be adjusted by moving the magnetic base 6;

[0041] The ball screw device 18 is arranged on the measuring platform between the third slideway 13 and the fourth slideway 14;

[0042] The laser 17 is used to provide a laser light source. A polarizing plate 22 is provided at the front end of the laser 17. When assembled, the laser is fixed to the ball screw device 18 through a connecting plate 20. During the measurement process, the laser can be driven to move up and down by the ball screw device 18.

[0043] The reflector device 10 is used to reflect the laser light scattered from the transparent polymer material model 5 , and is fixedly mounted to the ball screw device 18 .

[0044] In this embodiment 1, the reflector device 10 is composed of a reflector lens and a steel block with a groove, and the steel block with a groove can be fixed to the ball screw device 18 by multiple bolts 21. The reflector lens is embedded in the steel block with a groove, and the reflector and the steel block with a groove are bonded; further, when specifically set, the reflector lens needs to be at an angle of 45° with the horizontal direction.

[0045] Furthermore, in the present embodiment 1, the light source 2 , the first polarizer 3 , the first 1 / 4 wave plate 4 , the second 1 / 4 wave plate 7 , the second polarizer 8 and the CCD camera 9 are fixed to the magnetic base 6 via connecting rods 19 , respectively.

[0046] The transparent polymer material residual stress measurement device described in this embodiment 1 integrates all optical components involved in the photoelastic method and the astigmatism method on a measurement platform. When measuring the stress of the transparent polymer material model, the position of each optical component can be flexibly adjusted to meet the detection requirements.

[0047] Example 2: Figures 1 to 2 As shown, a method for measuring residual stress of transparent polymer material using the measuring device described in Example 1

[0048] The measurement method described in this embodiment 2 performs stress detection based on the principle of photoelasticity, and the specific operation steps are as follows:

[0049] S1, remove or slide the first 1 / 4 wave plate 4 and the second 1 / 4 wave plate 7 to an area that does not affect the measurement, adjust the light source 2, the first polarizer 3, the transparent polymer material model 5, the second polarizer 8 and the CCD camera 9 to be coaxial, and adjust the optical path by rotating the first polarizer 3 and the second polarizer 8 to obtain a plane polarized light field, collect the mixed fringe pattern of equidistant lines and isoclinic lines by the CCD camera 9, and rotate the two polarizers at the same time to change the isoclinic line fringe pattern, and the rotation angle of the two polarizers is the isoclinic angle θ of each point on the corresponding isoclinic line;

[0050] S2, the light source 2, the first polarizer 3, the first 1 / 4 wave plate 4, the transparent polymer material model 5, the second 1 / 4 wave plate 7, the second polarizer 8 and the CCD camera 9 are adjusted to an axis, and the circularly polarized light field is obtained by rotating the first polarizer 3 and the second polarizer 8 to adjust the light path. The arithmetic stripe pattern can be obtained from the circularly polarized light field, and the order of the arithmetic stripes at each point can be measured by the Tardy compensation method. The stress at each point can be calculated by the equal inclination angle θ and the arithmetic stripe order using the shear stress difference method.

[0051] Example 3: Figures 1 to 2 As shown, a method for measuring residual stress of transparent polymer material using the measuring device described in Example 1

[0052] The measurement method described in this embodiment 3 performs stress detection on transparent polymer materials based on the principle of astigmatism, and the specific operation steps are as follows:

[0053] S1, remove or move the light source 2, the first polarizer 3, the first 1 / 4 wave plate 4, the second 1 / 4 wave plate 7, and the second polarizer 8 to one side of the slide, the laser 17 generates 45° polarized light through the polarizer 22 installed at the front end, the transparent polymer material model 5 is placed directly in front of the laser 17, the laser 17 and the ball screw device 18 are turned on, the laser is incident on the transparent polymer material model 5, and the CCD camera 9 performs image acquisition in the reflector device 10; at the same time, the ball screw device 10 drives the laser 17 to scan up and down, and the light intensity is superimposed during the scanning process, and finally a light and dark scattered light interference fringe pattern is obtained, and the stress value of each point inside the specimen can be calculated based on the light and dark scattered light interference fringe pattern.

[0054] Example 4: Figures 1 to 2 As shown, a method for measuring residual stress of transparent polymer material using the measuring device described in Example 1

[0055] The measurement method described in Example 4 combines the photoelastic method and the astigmatism method to detect the residual stress of transparent polymer materials. The specific operation steps are as follows:

[0056] In the first step, the light source 2, the first polarizer 3, the first 1 / 4 wave plate 4, the second 1 / 4 wave plate 7, and the second polarizer 8 are removed or moved to one side of the slideway, and the transparent polymer material model 5 is placed in front of the laser 17, and the laser 17 and the ball screw device 18 are turned on. The laser is incident on the transparent polymer material model 5, and the CCD camera 9 performs image acquisition in the reflector device 10; at the same time, the ball screw device 18 drives the laser 17 to scan up and down, and the light intensity is superimposed during the scanning process. Finally, a light and dark scattered light interference fringe pattern is obtained. The stress calculation can be performed based on the interference fringe pattern. The stress component σ at each point inside the specimen y The calculation formula of the fringe order is as follows:

[0057]

[0058] Where: n x is the fringe order in the scattered light interference fringe pattern when the incident light is incident along the x-axis; f σ is the fringe value of the material; d is the model thickness; (the specific optical path diagram is as follows Figure 3 (shown)

[0059] In the second step, the light source 2, the first polarizer 3, the transparent polymer material model 5, the second polarizer 8 and the CCD camera 9 are adjusted to be coaxial, and the plane polarized light field is obtained by rotating the first polarizer 3 and the second polarizer 8 to adjust the optical path, and the CCD camera 9 collects the mixed fringe pattern of isoclinic lines and isoclinic lines, and the two polarizers are rotated at the same time to change the isoclinic line fringe pattern, and the rotation angle of the two polarizers is the isoclinic angle θ of each point on the corresponding isoclinic line;

[0060] In the third step, the light source 2, the first polarizer 3, the first 1 / 4 wave plate 4, the transparent polymer material model 5, the second 1 / 4 wave plate 7, the second polarizer 8 and the CCD camera 9 are adjusted to an axis, and the circularly polarized light field is obtained by rotating the first polarizer 3 and the second polarizer 7 to adjust the optical path. The arithmetic stripe diagram can be obtained from the circular polarization square. The order n of the arithmetic stripes at each point can be measured by the Tardy compensation method. The stress at each point can be calculated by the shear stress difference method from the equal inclination angle and the arithmetic stripe order n (the specific optical path diagram is shown in FIG. Figure 4 The calculation formula is as follows:

[0061]

[0062] Where: n is the order of the equidistant fringe; f σ is the stripe value of the material; d is the model thickness;

[0063] Using the principal stress difference, the isocline angle θ and the stress component σ calculated in the first step y , the other two stress components τ are calculated xy and σ x ;

[0064]

[0065]

[0066] Where: θ is the isoclinic angle; n is the order of the equidistant line fringes; f σ is the stripe value of the material; d is the model thickness; n x It is the fringe order in the scattered light interference fringe pattern when the incident light is incident along the x-axis.

[0067] Among them, when the residual stress of transparent polymer materials is measured by the photoelastic method described in Example 2 of the present invention, after the order of the arithmetic line fringes and the isoclinic angle are tested, the shear stress difference method needs to be used to perform stress separation and calculate the stress components. Among them, the shear stress difference method is relatively cumbersome to calculate, and it is necessary to determine the boundary conditions. In the process of residual stress testing, it is relatively complicated to determine the boundary stress, or even impossible to determine it. In addition, calculation errors will be introduced in the calculation process.

[0068] When the residual stress of a transparent polymer material is measured by the astigmatism method described in Example 3 of the present invention, the principle is similar to that of the photoelastic method, both of which utilize the birefringence effect of transparent materials. The difference is that the photoelastic method uses transmitted light to form interference fringes, while the astigmatism method utilizes scattered light. Although this method can measure the internal stress of a material model, when testing the internal stress deep from the surface of the material model, the collected astigmatism fringe pattern will be affected by the intensity of the scattered light, and even the test cannot be performed.

[0069] The stress measurement method described in Example 4 of the present invention can effectively avoid the defects existing in Examples 2 and 3, and can conveniently and accurately test the three stress components σ x , σ y and τ xy , which is the residual stress of the transparent polymer material model to be tested.

[0070] In addition, it should be noted that the shapes and names of the parts and components of the specific embodiments described in this specification may be different. Any equivalent or simple changes made based on the structure, features and principles described in the patent concept of the present invention are included in the protection scope of the patent of the present invention. The technicians in the technical field of the present invention can make various modifications or supplements to the specific embodiments described or replace them in a similar manner, as long as they do not deviate from the structure of the present invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. A measuring device for detecting residual stress of transparent polymer materials, characterized in that: The device comprises a measuring platform, a light source, a first polarizer, a first quarter wave plate, a ball screw device, a laser, a reflector device, a second quarter wave plate, a second polarizer, a CCD camera and a transparent polymer material model, wherein: The measuring platform is provided with a plurality of slideways; The light source, the first polarizer, the first 1 / 4 wave plate, the second 1 / 4 wave plate, the second polarizer and the CCD camera are respectively assembled in sequence in the slideway on the measuring platform through the magnetic base, and the light source, the first polarizer, the first 1 / 4 wave plate, the second 1 / 4 wave plate, the second polarizer and the CCD camera can be separated from the slideway or their positions in the slideway can be adjusted by moving the magnetic base; The ball screw device is arranged on a measuring platform between two slideways for assembling the first 1 / 4 wave plate and the second 1 / 4 wave plate; A polarizing plate is provided at the front end of the laser, and the laser can be driven to move up and down by a ball screw device; The reflector device is used to reflect the laser light scattered out of the transparent polymer material model, and is fixedly mounted with the ball screw device.

2. The measuring device for detecting residual stress of transparent polymer materials according to claim 1, characterized in that: The laser is fixed to the ball screw device via a connecting plate, the reflector device is composed of a reflective lens and a grooved steel block, the grooved steel block is fixed to the ball screw device via bolts, and the reflective lens is at an angle of 45° to the horizontal direction.

3. The measuring device for detecting residual stress of transparent polymer materials according to claim 2, characterized in that: The reflective lens is embedded in the steel block with a groove by means of a groove fit, and the reflective lens and the steel block with a groove are bonded.

4. The measuring device for detecting residual stress of transparent polymer materials according to claim 1, characterized in that: The light source, the first polarizing plate, the first 1 / 4 wave plate, the second 1 / 4 wave plate, the second polarizing plate and the CCD camera are fixed to the magnetic base via connecting rods respectively.

5. A method for measuring residual stress of transparent polymer materials using the measuring device according to any one of claims 1 to 4, characterized in that: The following steps are involved: In the first step, the light source, the first polarizer, the first 1 / 4 wave plate, the second 1 / 4 wave plate, and the second polarizer are removed or moved to one side of the slide. The laser generates 45° polarized light through the polarizer installed at the front end. The transparent polymer material model is placed in front of the laser, the laser and the ball screw device are turned on, and the laser is incident on the transparent polymer material model. The CCD camera collects images in the reflector device; at the same time, the ball screw device drives the laser to scan up and down, and the light intensity is superimposed during the scanning process. Finally, the light and dark scattered light interference fringe pattern is obtained. The stress calculation can be performed based on the interference fringe pattern. The stress component σ at each point inside the specimen y The calculation formula of the fringe order is as follows: Where: n x is the fringe order in the scattered light interference fringe pattern when the incident light is incident along the x-axis; f σ is the stripe value of the material; d is the model thickness; In the second step, the light source, the first polarizer, the transparent polymer material model, the second polarizer and the CCD camera are adjusted to be coaxial, and the plane polarized light field is obtained by rotating the first polarizer and the second polarizer to adjust the optical path. The mixed fringe pattern of isoclinic lines and isoclinic lines is collected by the CCD camera, and the two polarizers are rotated at the same time to change the isoclinic line fringe pattern. The rotation angle of the two polarizers is the isoclinic angle θ of each point on the corresponding isoclinic line; The third step is to adjust the light source, the first polarizer, the first quarter wave plate, the transparent polymer material model, the second quarter wave plate, the second polarizer and the CCD camera to an axis, and adjust the optical path by rotating the first polarizer and the second polarizer to obtain a circularly polarized light field. The arithmetic stripe pattern can be obtained from the circular polarization square. The order n of the arithmetic stripes at each point can be measured by the Tardy compensation method. The stress at each point can be calculated by the shear stress difference method from the equal inclination angle and the arithmetic stripe order n. The calculation formula is as follows: Where: n is the order of the equidistant fringe; f σ is the stripe value of the material; d is the model thickness; Using the principal stress difference, the isocline angle θ and the stress component σ calculated in the first step y , the other two stress components τ are calculated xy and σ x ; Where: θ is the isoclinic angle; n is the order of the equidistant line fringes; f σ is the stripe value of the material; d is the model thickness; n x It is the fringe order in the scattered light interference fringe pattern when the incident light is incident along the x-axis.

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