Photoelectric auxiliary complex shearing path fracture test fixture and detection method

Abstract

The application relates to a photoelectricity-assisted complex shearing path fracture test fixture and a detection method, which comprises a motion unit, a clamping unit and a data detection unit; the motion unit comprises a motion cover plate and a fixed cover plate, both of which are fixedly connected with a testing machine, and the clamping unit and the data detection unit are fixed on the motion unit; the clamping unit comprises a motion back plate and a fixed back plate, and the whole structure is symmetrically distributed in the middle part of the motion unit; the data detection unit comprises a pulse sensor and an industrial camera, and the whole structure is distributed on both sides of the motion unit and is fixedly connected with the lower end of the motion unit. The bidirectional clamping is realized through the combined design of the back plate and the cover plate, the fastening force of the test piece is stronger, the photoelectricity-assisted detection method is adopted, the strain path of the complex shearing path fracture can be obtained, the detection precision is improved, the accurate prediction of the damage and unstable fracture behavior is realized, and the method has the functions of high reliability, high efficiency, powerful function and convenient operation.

Description

Technical Field

[0001] This invention belongs to the technical field of sheet metal forming testing equipment, and specifically relates to a photoelectric-assisted complex shear path fracture testing fixture and detection method. Background Technology

[0002] In the aerospace and automotive industries, component damage and fracture are extremely common phenomena, often leading to accidents. This not only increases production and maintenance costs but also creates significant safety hazards. Therefore, preventing component damage and fracture is crucial, and obtaining accurate performance parameters and fracture indices of metallic materials is key to scientific research. Since component fracture is closely related to the shearing it experiences, obtaining fracture data under complex shear paths is an important means of predicting and preventing material fractures in production and daily life.

[0003] In traditional processes and research, the specimens undergoing shear tests are not subjected to pure shear on both sides; only a small area in the center of the specimen experiences pure shear. Therefore, existing micro-shear fixtures are relatively small, and the specimens themselves are also small. The center of the specimen is significantly affected by the shear from both sides, resulting in low accuracy of experimental data.

[0004] Furthermore, complex shear path fracture tests inevitably subject the specimen to repeated tension and compression, while current clamps only lock the specimen in one direction and cannot completely lock it. The slippage of the specimen will reduce the accuracy of the experimental data.

[0005] Therefore, traditional shearing fixtures are not well-suited for detecting the initiation and development of damage and fracture in metallic materials. Furthermore, the detection of minute cracks during shearing and the acquisition of displacement and strain fields under complex shearing paths are urgent problems to be solved. To address these issues in traditional processes, we urgently need a more practical fracture testing fixture and method that can adapt to complex shearing paths and offers high detection accuracy. Summary of the Invention

[0006] To address the above issues, this invention provides a photoelectric-assisted complex shear path fracture testing fixture and method. The bidirectional clamping is achieved through a two-way combination design of the back plate and cover plate, resulting in stronger specimen clamping force. The photoelectric-assisted detection, combining pulse sensor detection of the shear displacement field with industrial camera detection of the shear strain field, can acquire the strain path of complex shear path fractures, improving detection accuracy. It features high reliability, high efficiency, powerful functionality, and convenient operation.

[0007] The technical solution adopted in this invention is a photoelectric-assisted complex shear path fracture test fixture, which includes a motion unit, a clamping unit, and a data detection unit; the clamping unit and the data detection unit are both fixed on the motion unit; both ends of the motion unit are fixedly connected to the testing machine; the clamping unit is centrally symmetrically distributed in the middle of the motion unit; the data detection unit is distributed on both sides of the motion unit and fixedly connected to the lower end of the motion unit; the motion unit includes a motion back plate, a fixed back plate, an insulating block, a sliding guide rail, a bottom cover, and a temperature control pipe, and the motion back plate is located on the fixed back plate. Above the plate; the inner surfaces of the middle part of the moving back plate and the fixed back plate are both set in a stepped shape, and each stepped surface has a hole. The moving back plate and the fixed back plate are respectively fixed by cooperating with the moving back plate and the fixed back plate through the holes; the left and right sides of the moving back plate are provided with a first groove, and the insulating block is placed in the first groove; the left and right sides of the fixed back plate are provided with a second groove, and the sliding guide rail is placed in the second groove; the bottom cover is fixedly installed at the end of the second groove, and the insulating block is slidably connected to the sliding guide rail; the clamping unit includes a moving back plate and the fixed back plate. The system comprises a movable cover plate, a fixed cover plate, an insulating gasket, a light strip, and a test specimen. The movable and fixed cover plates have identical structures and are both L-shaped. The two inner sides of the movable and fixed cover plates contact and press against the two outer sides of the test specimen longitudinally and laterally, respectively. Both the short and long sides of the movable and fixed cover plates have through holes, through which the test specimen is locked and fixed. A third groove is provided on the inclined surface of the movable and fixed cover plates near the end of the test specimen, and the light strip is disposed within the third groove. The data detection unit includes a pulse... The system includes a sensor, an industrial camera, a mounting base, a base platform, a camera bracket, and connecting cables. The pulse sensor is fixedly mounted on the first side of the motion unit and is fixedly connected to the rear side of the motion back plate via the mounting base. The industrial camera is fixedly mounted on the second side of the motion unit and is fixedly connected to the lower end of the fixed back plate via the camera bracket. The base platform is fixedly connected to the rear side of the fixed back plate and is located below the pulse sensor. The first end of the camera bracket is fixed below the motion unit and is fixedly connected to the industrial camera.

[0008] Preferably, the top and bottom surfaces of the moving cover plate and the fixed cover plate are provided with U-shaped grooves, and the middle of the short side of the moving cover plate and the fixed cover plate is provided with a through groove, the width of the through groove being greater than the width of the U-shaped groove.

[0009] Furthermore, both the moving backplate and the fixed backplate are provided with temperature control pipes. The temperature control pipes are hollow and segmented and curved, and the outside of the temperature control pipes is provided with pipe interfaces.

[0010] Furthermore, both the moving backplate and the fixed backplate have through holes on their long sides, through which the specimen is connected to the current.

[0011] Preferably, insulating pads are fixed at the contact points of the moving back plate, the fixed back plate, the moving cover plate, and the fixed cover plate with the test specimen, and an insulating pad is fixed at the contact point of the tail probe of the pulse sensor with the base plate platform.

[0012] Preferably, the connecting line includes a control connecting line and a data transmission connecting line, wherein a first end of the control connecting line is connected to a pulse sensor and a second end of the control connecting line is connected to an industrial camera; a first end of the data transmission connecting line is connected to a pulse sensor and a second end of the control connecting line is connected to a computer.

[0013] Preferably, the axis of the industrial camera lens is perpendicular to the outer side of the fixed back plate;

[0014] A second aspect of the present invention provides a detection method for the aforementioned photoelectric-assisted complex shear path fracture test fixture, which specifically includes the following steps:

[0015] S1. The test piece to be tested is tightened in both directions by adjusting the moving back plate, fixed back plate, moving cover plate and fixed cover plate, and the work of turning on the light strip, cooling with water and pre-test debugging is started.

[0016] S2. Perform an electrical test on the fracture test fixture for complex shear paths. The specific testing method is as follows:

[0017] (1) Current is between 0.1A and 1A: When the test piece is damaged, wires are welded on both sides of the test piece and the wires are connected to the power supply from the opening holes on both sides of the fixed back plate; at this time, the first insulating pad needs to be installed at the contact part between the test piece and the moving back plate, the fixed back plate, the moving cover plate and the fixed cover plate.

[0018] (2) Current range of 50A-200A: When performing a hot shear test, a high current power supply is connected at the fixed connection of the bottom cover on both sides of the fixed back plate; at this time, a second insulating pad needs to be installed at the contact part between the specimen and the moving back plate, fixed back plate, moving cover plate and fixed cover plate, and the second insulating pad has a higher strength than the first insulating pad.

[0019] S3. The industrial camera is controlled by a pulse sensor to take pictures, and the obtained data is transmitted to the testing machine. The testing machine automatically generates a displacement load curve.

[0020] S4. Conduct cyclic shear tests with forward and reverse loading and unloading. The testing machine automatically writes out the state variables according to the different loading paths: -1 for the upward state, 0 for the stationary state, and 1 for the downward state. Based on the different state variables, the displacement load data output by the testing machine is processed in segments as follows:

[0021] (1) If the loading path of the testing machine is in the downward state, i.e. S=1, the data is stored in arrays a(x,y), c(x,y) and e(x,y) in sequence;

[0022] (2) If the loading path of the testing machine is in a stationary state, i.e. S=0, then delete the array (x,y);

[0023] (3) If the loading path of the testing machine is in the upward state, i.e. S = -1, the data will be stored in arrays such as b(x,y), d(x,y), and f(x,y) in sequence;

[0024] S5. The industrial camera obtains DIC images of the specimen's displacement and deformation during the test based on control commands from the pulse sensor, and analyzes the corresponding displacement x of the testing machine through software. i To obtain the shear strain values ​​and deformation displacements of each region of the specimen;

[0025] S6. Analyze the displacement x of the testing machine during cyclic shearing under both positive and negative loading and unloading. i The changing pattern is analyzed, and corresponding fitting is performed based on either increasing or decreasing changing patterns:

[0026] (1) If x i If the increment is positive, it represents the positive loading segment, which fits and forms functions such as f1(x), f3(x), and f5(x).

[0027] (2) If x i If the values ​​decrease, it represents the reverse unloading segment, and functions such as f2(x), f4(x), and f6(x) are fitted. The fitted equations are as follows:

[0028]

[0029] In the formula, x is the displacement of the testing machine corresponding to the DIC photograph. Here, m represents the coefficients of the fitted equation, m represents the number of piecewise curves, and n represents the number of fitted coefficients.

[0030] S7. Fit functions f1, f2, f3, etc. to different DIC data segments, and correct the testing machine data array based on the fitted functions. Use function f1 to calculate the shear strain or displacement of each part of the displacement load data, or use function f2 to calculate the shear strain or displacement of each part of the displacement load data, and so on until all the displacement data obtained by the testing machine is converted into the actual displacement or strain of the specimen. Finally, the deformation data is corrected to the true value through the entire DIC system to achieve accurate prediction of damage and instability fracture behavior.

[0031] The features and beneficial effects of this invention are:

[0032] 1. The present invention provides a photoelectric-assisted complex shear path fracture test fixture, which achieves radial clamping through the combination design of a moving back plate and a moving cover plate; and achieves axial clamping through the combination design of a fixed back plate and a fixed cover plate; the bidirectional clamping design makes the specimen clamping force stronger, and has the advantages of high fracture test accuracy and experimental stability.

[0033] 2. The present invention provides a photoelectric-assisted detection method for a complex shear path fracture test fixture. Based on a cyclic shear experiment with forward and reverse loading and unloading, it adopts a photoelectric-assisted detection strategy that combines pulse sensor detection of shear displacement field and industrial camera detection of shear strain field. This method can obtain the strain path of complex shear path fracture and perform data fitting and correction processing, thereby improving the accuracy, reliability and efficiency of fracture detection and achieving accurate prediction of damage and unstable fracture behavior.

[0034] 3. The present invention provides a photoelectric-assisted complex shear path fracture test fixture. The design of the insulating block and the guide rail has insulation, positioning and guiding functions; the light strip is installed in the groove of the cover plate to provide a light source for the industrial camera and reduce the experimental cost; the design of the temperature control pipe can reduce the experimental temperature and improve the service life; it has the characteristics of powerful auxiliary functions, convenient operation and strong practicality. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the overall structure of the photoelectric-assisted complex shear path fracture test fixture of the present invention;

[0036] Figure 2 This is a side view of the overall structure of the photoelectric-assisted complex shear path fracture test fixture of the present invention;

[0037] Figure 3 This is a top view schematic diagram of the overall structure of the photoelectric-assisted complex shear path fracture test fixture of the present invention;

[0038] Figure 4 This is a schematic diagram of the motion unit of the present invention;

[0039] Figure 5 This is a cross-sectional schematic diagram of the insulating block guiding and positioning of the present invention;

[0040] Figure 6 This is a schematic diagram of the clamping unit of the present invention;

[0041] Figure 7 This is a schematic diagram of the structure of the moving cover plate of the present invention;

[0042] Figure 8 This is a schematic diagram of the pulse sensing part of the data detection unit of the present invention;

[0043] Figure 9 This is a schematic diagram of the industrial camera portion of the data detection unit of the present invention;

[0044] Figure 10 This is a schematic diagram of the shear test data analysis of the present invention;

[0045] Figure 11 This is a flowchart of the operation steps of the present invention;

[0046] Figure 12 This is a flowchart of the detection method of the present invention.

[0047] Key reference numerals:

[0048] Motion unit 1; clamping unit 2; data detection unit 3; motion back plate 11; insulating block 12; pre-tightening component 13; bottom cover 14; fixed back plate 15; sliding guide rail 16; temperature control pipe interface 17; motion cover plate 21; insulating gasket 22; test piece 23; fixed cover plate 24; light strip 25; pulse sensor 31; fixed base 32; base plate platform 33; camera bracket 34; connecting cable 35; industrial camera 36. Detailed Implementation

[0049] To fully describe the technical content, structural features, objectives, and effects of this invention, a detailed description will be provided below in conjunction with the accompanying drawings.

[0050] This invention provides a photoelectric-assisted complex shear path fracture testing fixture, such as... Figures 1-3 As shown, it includes a motion unit 1, a clamping unit 2, and a data detection unit 3. The motion unit 1 includes a motion backplate 11 and a fixed backplate 15, both of which are fixedly connected to the testing machine. The clamping unit 2 and the data detection unit 3 are both fixed to the motion unit 1. The clamping unit 2 includes a motion cover plate 21 and a fixed cover plate 24, whose overall structure is centrally symmetrically distributed in the middle of the motion unit 1. The data detection unit 3 includes a pulse sensor 31 and an industrial camera 36, ​​whose overall structure is distributed on both sides of the motion unit 1 and fixedly connected to the lower end of the motion unit 1. The lens axis of the industrial camera 36 is perpendicular to the outer side of the fixed backplate 15.

[0051] like Figure 4 As shown, the motion unit 1 includes a motion back plate 11, an insulating block 12, a pre-tightening member 13, a bottom cover 14, a fixed back plate 15, a sliding guide rail 16, and a temperature control pipe interface 17. The back plate includes a motion back plate 11 and a fixed back plate 15, which are arranged vertically, with the motion back plate 11 located above the fixed back plate 15. The inner sides of the middle of both the motion back plate 11 and the fixed back plate 15 are stepped, and each stepped surface has holes for fixing with the cover plate. The left and right sides of the motion back plate 11 have grooves for embedding the insulating block 12, and the left and right sides of the fixed back plate 15 have grooves for placing the sliding guide rail 16. The left and right sides of the fixed back plate 15 have pre-tightening members 13 to pre-tighten the sliding guide rail 16 and the insulating block 12. The bottom cover 14 is fixedly installed at the end of the groove on the side of the fixed back plate 15. The insulating block 12 in the groove of the motion back plate 11 is slidably connected to the sliding guide rail 16 in the groove of the fixed back plate 15.

[0052] Furthermore, the back panel is provided with a temperature control pipe with an external temperature control pipe interface 17. The temperature control pipe is hollow inside, has a segmented curved structure, and runs through the entire structure in the center.

[0053] like Figure 5 As shown, insulating pads 22 are fixed at the points where the back plate and cover plate are close to and in contact with the specimen 23, and insulating pads 22 are fixed at the points where the tail probe of the pulse sensor 31 is close to and in contact with the base plate platform 33. The design of the insulating block 12 and the guide rail has the functions of insulation, positioning and guidance.

[0054] like Figure 6 As shown, the clamping unit 2 includes a movable cover plate 21, a fixed cover plate 24, an insulating gasket 22, a light strip 25, and a test piece 23. The cover plate includes a movable cover plate 21 and a fixed cover plate 24, both of which have the same shape and structure, and both are L-shaped. The two inner sides of the cover plate and the two outer sides of the test piece 23 are in longitudinal and transverse contact and compression, respectively, and both the short and long sides of the cover plate are provided with through holes for locking the test piece 23. The insulating gasket 22 is fixed on the side surface of the cover plate that contacts the test piece 23, and the end slope of the cover plate near the test piece 23 is provided with a groove for placing the light strip 25.

[0055] like Figure 7 As shown, the top and bottom surfaces of the cover plate are provided with U-shaped grooves, and a through groove is provided in the middle of its short side. The width of the through groove is slightly larger than the width of the U-shaped groove.

[0056] like Figure 8 and Figure 9As shown, the data detection unit 3 includes a pulse sensor 31, an industrial camera 36, ​​a mounting base 32, a base platform 33, a camera bracket 34, and a connecting cable 35. The pulse sensor 31 is fixedly installed on one side of the motion unit 1 and is fixedly connected to the rear side of the motion back plate 11 through the mounting base 32, and can move together with the motion back plate 11. The industrial camera 36 is fixedly installed on the other side of the motion unit 1 and is fixedly connected to the lower end of the fixed back plate 15 through the camera bracket 34. The base platform 33 is fixedly connected to the rear side of the fixed back plate 15 and is located below the pulse sensor 31. One end of the camera bracket 34 is fixed below the motion unit 1, and the other end is fixedly connected to the industrial camera 36.

[0057] Furthermore, the connection line 35 includes a control connection line 35 and a data transmission connection line 35. One end of the control connection line 35 is connected to the pulse sensor 31, and the other end is connected to the industrial camera 36; one end of the data transmission connection line 35 is connected to the pulse sensor 31, and the other end is connected to the computer.

[0058] like Figure 10 As shown, this is a shear test data graph of a photoelectric-assisted complex shear path fracture test fixture. The experimental material is SP1180, and the specimen 23 has dimensions of 64mm*18mm*1.4mm. The pure shear region in the middle of specimen 23 is less affected by the two sides, and the experimental curve has no obvious fluctuations and is relatively smooth. This indicates that the bidirectional clamping design of the back plate and cover plate can make the clamping force of specimen 23 stronger, thus improving the stability and accuracy of the shear test data.

[0059] like Figure 11 The diagram shown is a flowchart of the operation steps for a photoelectric-assisted complex shear path fracture test fixture. The usage process of this invention is explained below in conjunction with the flowchart:

[0060] First, the insulating pad 22 is attached and fixed to the contact surfaces of the moving back plate 11, the fixed back plate 15, the moving cover plate 21, and the fixed cover plate 24 with the specimen, and then the moving back plate 11 is installed into the press.

[0061] Then, the industrial camera 36 is mounted on the fixed back plate 15 and installed into the press through the thread on the head, so that the camera lens is facing the specimen mounting position in the middle of the fixed back plate.

[0062] Next, the two insulating blocks 12 are respectively embedded into the left and right side grooves of the moving back plate 11, and the two sliding guide rails 16 are respectively embedded into the left and right side grooves of the fixed back plate 15, and the bottom covers 14 are installed to prevent the guide rails from becoming loose. By adjusting the height of the press, the parts of the fixed back plate 11 and the moving back plate 15 that hold the specimen are in a horizontal state.

[0063] Again, such as Figure 7 and Figure 8As shown, a mounting base 32 and a base platform 33 are installed on the rear side of the motion backplate, and a pulse sensor 31 and an insulating pad 22 are fixed on the mounting base 32 and the base platform 33, respectively. One side of the industrial camera 36 is connected to the pulse sensor 31 by adjusting the fastening force, and the other side of the industrial camera 36 is connected to the computer via a wire.

[0064] Next, the specimen 23 is placed at the middle step of the moving back plate 11 and the fixed back plate 15, the moving cover plate 21 and the fixed cover plate 24 are installed, and the specimen is locked in both directions of thickness and width by the fixed connector.

[0065] Finally, turn on the experimental light strip 25, adjust the camera bracket 34 again so that the computer can clearly photograph the deformation area of ​​the specimen, and then apply current to start the experiment.

[0066] like Figure 12 The diagram shows a flowchart of a photoelectric-assisted method for testing complex shear path fracture fixtures. This invention proposes a photoelectric-assisted method for testing complex shear path fracture fixtures, which specifically includes the following steps:

[0067] S1. First, the test piece to be tested is tightened in both directions by adjusting the cover plate and the back plate, and some auxiliary work such as turning on the light strip, cooling with water and pre-test debugging is carried out.

[0068] S2. Secondly, for the complex shear path fracture test fixture, an electrical test is conducted. The test method provides two different current connection methods, as detailed below:

[0069] (1) Current is between 0.1A and 1A: When the test specimen is damaged, wires can be welded on both sides of the specimen and the wires can be connected to the power supply from the opening holes on both sides of the fixed back plate; at this time, insulating pads need to be installed at the contact parts of the specimen, back plate and cover plate.

[0070] (2) Current range of 50A-200A: When conducting a hot shear test, a high current power supply can be connected at the fixed connection of the bottom cover on both sides of the back plate; at this time, a high-strength metal gasket needs to be installed at the contact part between the specimen, the back plate, and the cover plate.

[0071] S3. Furthermore, an industrial camera is controlled by a pulse sensor to take pictures, and the obtained data is transmitted to the testing machine. The testing machine can automatically generate displacement load curves for analysis.

[0072] S4. Then, a cyclic shear test with forward and reverse loading and unloading is conducted. The testing machine automatically writes the state variables according to the different loading paths: -1 for the upward state, 0 for the stationary state, and 1 for the downward state. Based on the different state variables, the displacement load data output by the testing machine can be segmented as follows:

[0073] (1) If the loading path of the testing machine is in the downward state, i.e. S=1, the data is stored in arrays a(x,y), c(x,y) and e(x,y) in sequence;

[0074] (2) If the loading path of the testing machine is in a stationary state, i.e. S=0, then delete the array (x,y);

[0075] (3) If the loading path of the testing machine is in the upward state, i.e. S = -1, the data will be stored in arrays such as b(x,y), d(x,y), and f(x,y) in sequence.

[0076] S5. Next, the industrial camera obtains DIC images of the specimen's displacement and deformation during the test based on control commands from the pulse sensor, and analyzes the corresponding displacement x of the testing machine through software. i It can obtain the shear strain value and deformation displacement of each region of the specimen.

[0077] S6. Next, analyze the displacement x of the test machine during the cyclic shearing under positive and negative loading and unloading. i The changing pattern is analyzed, and corresponding fitting is performed based on either increasing or decreasing changing patterns:

[0078] (1) If x i If the increment is positive, it is a positive loading segment, which can be fitted to form functions such as f1(x), f3(x), and f5(x);

[0079] (2) If x i If the values ​​decrease, it represents the reverse unloading segment, which can be fitted to form functions such as f2(x), f4(x), and f6(x); the fitted equations are as follows:

[0080]

[0081] In the formula, x is the displacement of the testing machine corresponding to the DIC photograph. represents the coefficients of the fitted equation, m represents the number of piecewise curves, and n represents the number of fitted coefficients.

[0082] S7. Finally, functions f1, f2, f3, etc. are fitted according to different DIC data segments, and the testing machine data array is corrected accordingly based on the fitted functions. Function f1 can be used to calculate the shear strain or displacement of each part in the displacement load data, and function f2 can be used to calculate the shear strain or displacement of each part in the displacement load data. This process is repeated until all the displacement data obtained by the testing machine is converted into the actual displacement or strain of the specimen. Finally, the deformation data is corrected to the true value through the entire DIC system, so as to achieve accurate prediction of damage and instability fracture behavior.

[0083] In summary, the photoelectric-assisted complex shear path fracture testing fixture of this invention achieves radial clamping through a combination of a moving back plate and a moving cover plate, and axial clamping through a combination of a fixed back plate and a fixed cover plate. The bidirectional clamping design results in stronger specimen clamping force, offering advantages such as high fracture testing accuracy and experimental stability. Furthermore, the photoelectric-assisted detection method, combining pulse sensor detection of the shear displacement field with industrial camera detection of the shear strain field, can acquire the strain path of complex shear path fractures, improving the accuracy, reliability, and efficiency of fracture detection, and enabling accurate prediction of damage and unstable fracture behavior.

[0084] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. An opto-electrically assisted complex shear path fracture testing fixture, characterized by, It includes a motion unit, a clamping unit and a data detection unit; the clamping unit and the data detection unit are fixed on the motion unit; both ends of the motion unit are fixedly connected with the testing machine; the clamping unit is symmetrically distributed in the middle of the motion unit; the data detection unit is distributed on both sides of the motion unit and is fixedly connected to the lower end of the motion unit; The motion unit includes a motion back plate, a fixed back plate, an insulating block, a sliding guide rail, a bottom cover and a temperature control pipeline, the motion back plate is above the fixed back plate, the inner side of the middle part of the motion back plate and the fixed back plate is arranged in a stepped shape, each stepped surface is provided with a hole, the motion back plate and the fixed back plate are fixed by the holes, the left side and the right side of the motion back plate are provided with first grooves, the insulating block is arranged in the first grooves, the left side and the right side of the fixed back plate are provided with second grooves, the sliding guide rail is arranged in the second grooves, the bottom cover is fixedly installed at the end of the second groove, and the insulating block is slidably connected with the sliding guide rail. The clamping unit includes a motion cover plate, a fixed cover plate, an insulating gasket, a lamp strip and a test piece, the motion cover plate and the fixed cover plate are the same in structure and are arranged in an L-shaped structure, the two side surfaces inside the motion cover plate and the fixed cover plate are in contact and extrusion with the two side surfaces outside the test piece in the longitudinal and transverse directions, the two side surfaces of the short side and the long side of the motion cover plate and the fixed cover plate are provided with cover plate through holes, the test piece is locked and fixed through the through holes of the motion cover plate and the fixed cover plate, and the end part inclined surface of the motion cover plate and the fixed cover plate close to the test piece is provided with a third groove, and the lamp strip is arranged in the third groove. The data detection unit includes a pulse sensor, an industrial camera, a fixed seat, a bottom plate platform, a camera support and a connecting line, the pulse sensor is fixedly installed on the first side of the motion unit and is fixedly connected with the back side of the motion back plate through the fixed seat, the industrial camera is fixedly installed on the second side of the motion unit and is fixedly connected with the lower end of the fixed back plate through the camera support, the bottom plate platform is fixedly connected to the back side of the fixed back plate and is below the pulse sensor, and the first end of the camera support is fixed below the motion unit and is fixedly connected with the industrial camera.

2. The photo-electrically assisted complex shear path fracture test fixture of claim 1, wherein, The top surface and the bottom surface of the motion cover plate and the fixed cover plate are provided with U-shaped grooves, and the middle part of the short side of the motion cover plate and the fixed cover plate is provided with a through groove, and the width of the through groove is greater than the width of the U-shaped groove.

3. The photo-electrically assisted complex shear path fracture test fixture of claim 2, wherein, The motion back plate and the fixed back plate are provided with temperature control pipelines, the temperature control pipelines are hollow structures and are in a segmented curved shape, and the outer part of the temperature control pipeline is provided with a pipeline interface.

4. The photo-electrically assisted complex shear path fracture test fixture of claim 1, wherein, The long side surface of the motion back plate and the fixed back plate is provided with a back plate through hole, and the test piece is connected with current through the back plate through hole.

5. The photo-electrically assisted complex shear path fracture test fixture of claim 1, wherein, The motion back plate, the fixed back plate, the motion cover plate and the fixed cover plate are fixedly provided with insulating gaskets at the contact positions of the test piece, and an insulating gasket is fixedly arranged at the contact position of the tail probe of the pulse sensor and the bottom plate platform.

6. The photo-electrically assisted complex shear path fracture test fixture of claim 1, wherein, The connecting line comprises a control connecting line and a data transmission connecting line, a first end of the control connecting line is connected with the pulse sensor, and a second end of the control connecting line is connected with the industrial camera; a first end of the data transmission connecting line is connected with the pulse sensor, and a second end of the control connecting line is connected with the computer.

7. The photo-electrically assisted complex shear path fracture test fixture of claim 1, wherein, The axis of the industrial camera lens is perpendicular to the outer side of the fixed back plate.

8. A method for detecting the photoelectrically assisted complex shear path fracture testing fixture according to any one of claims 1-7, characterized in that, It comprises the following steps: S1, by adjusting the moving back plate, the fixed back plate, the moving cover plate and the fixed cover plate, the required test specimen is bidirectionally tightened, and the opening light strip, water cooling and pre-test debugging are started; S2, for the complex shear path fracture test fixture, the power-on test is carried out, and the specific detection method is as follows: (1) When the current is 0.1A-1A: when detecting the internal damage of the test specimen, the welding lead wire is welded on the symmetric two sides of the test specimen, and the lead wire is connected with the power supply from the opening hole on the two sides of the fixed back plate; at this time, the first insulating pad is installed on the contact part of the test specimen and the moving back plate, the fixed back plate, the moving cover plate and the fixed cover plate; (2) When the current is 50A-200A: when the hot shear experiment is carried out, the large current power supply is connected at the fixed connection of the bottom cover on the two sides of the fixed back plate; at this time, the second insulating pad is installed on the contact part of the test specimen and the moving back plate, the fixed back plate, the moving cover plate and the fixed cover plate, and the second insulating pad has higher strength than the first insulating pad; S3, the industrial camera is controlled to take pictures through the pulse sensor, and the obtained data is transmitted into the testing machine, and the testing machine automatically generates the displacement load curve; S4, the cyclic shear experiment of forward and reverse loading and unloading is carried out, the testing machine automatically writes the state variable according to the different loading paths, the uplink state is-1, the static state is 0, and the downlink state is 1, and according to the different state variables, the displacement load data output by the testing machine is processed as follows: (1) If the testing machine loading path is downlink state, that is, S=1, the data is sequentially stored in a(x, y), c(x, y) and e(x, y) arrays; (2) If the testing machine loading path is static state, that is, S=0, the array(x, y) is deleted; (3) If the testing machine loading path is uplink state, that is, S=-1, the data is sequentially stored in b(x, y), d(x, y), f(x, y) and other arrays; S5, the industrial camera obtains the displacement deformation DIC photo of the test piece in the test process based on the control command of the pulse sensor, and analyzes the corresponding test machine displacement x of the photo by software i , to obtain the shear strain value and deformation displacement of each region of the test piece; S6, analyze the change rule of displacement x in the cyclic loading and unloading of the test machine i According to the two change rules of increment and decrement, make corresponding fitting: (1) If x i is incremented, it is a forward loading segment, and the functions f1(x), f3(x), f5(x), etc. are formed by fitting; (2) If x i decreases, it is a reverse unloading section, and functions f2(x), f4(x), f6(x), etc. are formed by fitting. The fitting equation is as follows: where x is the displacement of the testing machine corresponding to the DIC picture, where a is the fitting equation coefficient, m is the number of piecewise curves, and n is the number of fitting coefficients. S7, according to different DIC data segments, f1, f2, f3 and other functions are fitted, and the testing machine data array is respectively corrected based on the fitting functions, the shear strain or displacement of each part in the displacement load data is calculated by using the function f1, or the shear strain or displacement of each part in the displacement load data is calculated by using the function f2, and so on until all the displacement data obtained by the testing machine are converted into the actual displacement or strain of the test specimen, finally the deformation data is corrected to the true value through the whole DIC system, and the accurate prediction of damage and instability fracture behavior is realized.

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