Biaxial tension-shear loading test clamp compatible with various connection forms

Abstract

The invention discloses a biaxial tension-shear loading test fixture compatible with various connection forms, comprising: an upper pair of porous loading discs and a lower pair of porous loading discs which are oppositely arranged, each porous loading disc is of a quarter circular structure, and the center of each porous loading disc is provided with a rectangular notch; the loading angle holes are formed in the circumferential direction of the porous loading disc at intervals; one end of each loading arm is arranged between the two porous loading discs which are arranged at an interval; the two groups of pin connection systems are used for detachably connecting the loading arms with the porous loading disc; the two test piece mounting mechanisms are oppositely arranged; the plurality of disc fastening systems are used for detachably connecting the test piece mounting mechanism with the porous loading disc; the test piece mechanism comprises two trilobal test pieces, and the two test pieces are relatively fixed at the center after 60 degrees are relatively selected by taking the center of the structure as an original point; and the plurality of test piece fastening systems are used for detachably connecting the test piece mechanism with the test piece mounting mechanism. And the tension-shear ratio of the applied load can be freely controlled according to actual requirements.

Description

Technical Field

[0001] The invention relates to a biaxial tension-shear loading test fixture which is compatible with various connection forms and belongs to the technical field of mechanical property testing of materials and structures. Background Art

[0002] In the current field of body manufacturing technology, the application of composite materials such as aluminum alloy, magnesium alloy, and carbon fiber has been very extensive, which has put forward higher requirements on the strength and reliability of the connection between components. In addition to the traditional resistance spot welding process, many new connection processes have also been born, such as Self-piercing Riveting, Clinching, Flow Drill Screws, etc. The working scene of the vehicle also determines that most of the body parts are in a complex stress state with multiple stresses. Especially under the tension-shear coupling stress, the point connection form may cause stress concentration, which in turn leads to deformation, fracture, fatigue, etc. Therefore, how to accurately measure the point connection form between various materials, the strength, failure form, fatigue characteristics and other mechanical properties under the combined action of tension-shear stress are of great significance to the selection and optimization of the point connection form.

[0003] Arcan fixtures are widely used in the field of material testing. They are often used to obtain stress states in any plane to study the failure mechanism of materials under different stress states. Through different loading forms, different tension-shear ratio loading of material components can also be achieved. With the rise of composite materials and material bonding technology, the application field of Arcan fixtures has been further expanded to the mechanical properties analysis of composite materials or bonding interfaces under bidirectional loading, especially in the fields of vehicles, aviation, etc. where composite materials and bonding technology are widely used.

[0004] In view of the actual application scenarios of the current body manufacturing process, the existing Arcan fixture has certain limitations: 1. The current conventional Arcan fixture generally uses standard test pieces to test the stress state of different materials or bonding interface layers. For point connection forms such as spot welding, spot bonding, and riveting commonly used in body craftsmanship, the two parts using this connection form are usually thinner, and the current standard test pieces of the Arcan fixture are difficult to be compatible with this type of connection form.

[0005] 2. When using the Arcan fixture to perform a tensile shear test on the connection interface of two components, loading offset may occur due to uneven connection distribution, which may lead to large errors in the test results. Summary of the invention

[0006] The present invention designs and develops a biaxial tension-shear loading test fixture that is compatible with a variety of connection forms and can freely control the tension-shear ratio of the applied load according to actual needs.

[0007] Another object of the present invention is to be compatible with a variety of connection forms and to test the biaxial tensile shear properties of the connection forms.

[0008] The technical solution provided by the present invention is: A biaxial tension-shear loading test fixture compatible with various connection forms, including: Two pairs of upper and lower porous loading plates are arranged opposite to each other. In each pair of porous loading plates, two porous loading plates are arranged at intervals. The porous loading plates are a quarter of a circular structure and have a rectangular notch at the center. a plurality of loading angle holes spaced apart along the circumference of the porous loading disk; two loading arms, one end of which is disposed between two porous loading disks disposed at intervals; Two sets of pin connection systems, one end of which passes through the loading angle hole and the loading arm to detachably connect the loading arm to the porous loading plate; Two specimen mounting mechanisms are arranged opposite to each other, and one end of the specimen mounting mechanism is arranged between the two porous loading plates arranged at intervals; A plurality of disc fastening systems, one end of which passes through the porous loading disc and one end of the specimen mounting mechanism to detachably connect the specimen mounting mechanism to the porous loading disc; The test piece mechanism comprises two three-leaf test pieces, the two test pieces are connected at the center after being rotated 60 degrees relative to each other with the structure center as the origin; the two test pieces are respectively arranged at the other ends of the two test piece installation mechanisms; One end of a plurality of specimen fastening ties passes through the other end of the specimen mounting mechanism and the specimen, so as to detachably connect the specimen to the specimen mounting mechanism.

[0009] Preferably, it also includes: a plurality of first nut mounting grooves, which are regular hexagonal structures, are arranged concentrically with the plurality of loading angle holes, and are located on one of the porous loading disks of each pair of porous loading disks; a loading arm pin hole, which is disposed at one end of the loading arm; A loading arm connecting pin, one end of which is a regular hexagon and is matched with the first nut mounting groove; the other end of the loading arm connecting pin is provided with an annular groove along the circumferential direction; A connecting pin retaining ring, which is a C-shaped structure and is matched with the annular groove; Wherein, the loading arm pin hole is matched with the loading angle hole, and the other end of the loading arm connecting pin passes through the loading angle hole and the loading arm pin hole and is positioned by a connecting pin retaining spring arranged in the annular groove; A loading arm mounting hole is provided on the side surface of the other end of the loading arm.

[0010] Preferably, the test piece has three circular ends and a first test piece mounting hole is formed thereon.

[0011] Preferably, the two test pieces are fixed with each other by at least one of welding, riveting, bolting and bonding.

[0012] Preferably, it also includes: A first specimen mounting arm hole is provided on the porous loading plate and is close to the rectangular notch; Wherein, on each of the porous loading plates, the number of the first specimen mounting arm holes is at least two.

[0013] Preferably, the specimen installation mechanism comprises: The specimen mounting arm is a rectangular structure, and one end of the arm is provided with at least two second specimen mounting arm holes; A specimen mounting platform, which is fixedly arranged at the other end of the specimen mounting arm; The specimen mounting platform has the same shape as the specimen, and a specimen connecting groove is provided in the middle of the specimen mounting platform, and second specimen mounting holes are provided on the circular ends of the specimen mounting platform.

[0014] Preferably, a second nut mounting groove is coaxially arranged with the first specimen mounting arm hole, which has the same structure as the first nut mounting groove and is located on the same porous loading plate.

[0015] Preferably, the disc fastening system comprises: a disc bolt, a disc nut and a disc fastening gasket; One end of the disc bolt passes through the first specimen mounting arm hole and the second specimen mounting arm hole and is fixed by the disc nut. The disc fastening gasket is located between the disc bolt and the porous loading plate, and the disc nut is set in the second nut mounting groove.

[0016] Preferably, the specimen fastening system comprises matched specimen bolts, specimen nuts and specimen fastening washers; One end of the specimen bolt passes through the first specimen mounting hole and the second specimen mounting hole in sequence, and is then fixed by the specimen nut; The specimen fastening gasket is arranged between the specimen bolt and the specimen mounting platform.

[0017] Preferably, the number of the loading angle holes is 13, and the angles between the loading angle holes and the vertical direction are: 0°, 7.5°, 15°, 22.5°, 30°, 37.5°, 45°, 52.5°, 60°, 67.5°, 75°, 82.5°, and 90° respectively.

[0018] The beneficial effects of the present invention are: 1. The three-leaf specimen of this device has a simple structure, is easy to process, and is well compatible with the point connection forms of components commonly used in the field of body manufacturing technology, such as spot welding, riveting, etc.; 2. The biaxial tensile shear loading test method proposed by this device can realize the strength test of the connection form under complex tensile and shear conditions, and through the thickness adjustment gasket, it can effectively prevent the loading center deviation caused by the inconsistent thickness of the two three-leaf specimens; 3. The test fixture of this device is reasonably designed, the overall structure is easy to process, and the various parts of the fixture are connected with standard bolts, which is easy to install and disassemble. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the three-dimensional structure of the biaxial tension-shear loading test fixture that is compatible with various connection forms according to the present invention.

[0020] Figure 2 This is an exploded view of the biaxial tensile shear loading test fixture of the present invention that is compatible with various connection forms.

[0021] Figure 3 It is a three-dimensional schematic diagram of the connection of the three-leaf test piece in the present invention.

[0022] Figure 4 It is a schematic diagram of the loading angle holes of the porous loading plate and the force diagram of the specimen in the present invention.

[0023] FIG5( a ) is a cross-sectional view of a three-leaf specimen connected by spot welding in the present invention.

[0024] FIG5( b ) is a cross-sectional view of a three-leaf specimen connected by rivets in the present invention.

[0025] FIG5( c ) is a cross-sectional view of a three-leaf specimen using bonding point connection in the present invention.

[0026] Loading arm 1, loading arm mounting hole 1a, loading arm pin hole 1b, porous loading plate 1 2, porous loading plate 2 21, loading angle hole 2a, first nut mounting groove 2b, hole 1 201, hole 2 202, hole 3 203, hole 4 204, hole 5 205, hole 6 206, hole 7 207, hole 8 208, hole 9 209, hole 10 210, hole 11 211, hole 12 212, hole 13 213, hole 14 214, hole 15 215, hole 16 216, hole 17 217, hole 18 218, hole 19 219, hole 20 220, hole 21 221, hole 22 222, hole 23 223, hole 24 224, hole 25 225, hole 2 Sixteen 226, first specimen mounting arm hole 2c, disc fastening system 3, disc bolt 31, disc nut 32, disc fastening gasket 33, specimen mounting mechanism 4, specimen mounting arm 41, specimen mounting platform 42, third nut mounting groove 4a, second specimen mounting hole 4b, specimen connecting groove 4c, second specimen mounting arm hole 4d, three-leaf specimen 5, first specimen mounting hole 5a, spot welding point 51, rivet point 52, bonding point 53, specimen fastening system 6, specimen bolt 61, specimen nut 62, specimen fastening gasket 63, pin connection system 7, loading arm connecting pin 71, connecting retaining ring 72, annular groove 7a, thickness adjustment plate 8, thickness adjustment gasket mounting hole 8a, gasket hole 8b. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0028] like Figure 1 -5, the present invention provides a biaxial tensile shear loading test fixture that is compatible with a variety of connection forms, including: a loading arm 1, a porous loading disc 2, a disc fastening system 3, a specimen mounting mechanism 4, a three-leaf specimen 5, a specimen fastening system 6, a pin connection system 7, and a thickness adjustment gasket 8.

[0029] Two pairs of upper and lower porous loading discs are arranged opposite to each other, and each pair of porous loading discs includes a porous loading disc 1 2 and a porous loading disc 2 21 arranged at intervals. Multiple loading angle holes 2a are opened in the circumferential direction on the porous loading disc 1 2 and the porous loading disc 2 21. One end of the two loading arms 1 is respectively arranged between the two porous loading discs 1 2 and the porous loading disc 2 21 arranged at intervals, and are fixedly and detachably connected by two sets of pin connection systems 7. Two specimen mounting mechanisms 4 are arranged opposite to each other, wherein one end of the specimen mounting mechanism 4 is arranged between the porous loading disc 1 2 and the porous loading disc 21, and are fixedly and detachably connected by a disc fastening system 3. The specimen mechanism includes two three-leaf specimens 5. The two three-leaf specimens 5 are fixed at the center after being rotated 60° relative to each other with the structure center as the origin. The two specimens 5 are respectively arranged at the other ends of the two specimen mounting mechanisms 4, and are fixedly and detachably connected by a specimen fastening system 6.

[0030] The porous loading plate 1 2 and the porous loading plate 2 21 clamp and install a loading arm 1 and a specimen installation mechanism 4 respectively through two groups of disc fastening systems 3 and a group of pin connection systems 7; the two three-leaf specimens 5 are connected in the required connection form to form a whole, and are clamped and installed through six groups of specimen fastening systems 6 and the specimen installation mechanism 4; if the thicknesses of the two three-leaf specimens 5 are inconsistent, a number of thickness adjustment gaskets 8 can be added between the three-leaf specimens 5 and the specimen installation mechanism 4, and then installed through the specimen fastening system 6.

[0031] In the present invention, as a preference, the loading arm 1 is a rectangular structure, one end of the loading arm 1 is provided with a through-type loading arm pin hole 1b for assembling with the loading angle hole 2a on the porous loading disk 2, and the other end is provided with a through-type loading arm mounting hole 1a for cooperating with an additional material testing machine to apply load.

[0032] The outer edge shape of the porous loading plate 1 2 and the porous loading plate 2 21 is arc-shaped, and the overall shape is approximately a quarter of a circle, and a rectangular notch is provided near the center of the circle, which serves as the installation space for the specimen mounting mechanism 4 and the three-leaf specimen 5; a plurality of loading angle holes 2a are evenly distributed on the outer periphery of the porous loading plate 1 2 and the porous loading plate 2 21.

[0033] In the present invention, as a preferred embodiment, the number of loading angle holes 2a is 13, and the angles between each loading angle hole 2a and the vertical direction are: 0°, 7.5°, 15°, 22.5°, 30°, 37.5°, 45°, 52.5°, 60°, 67.5°, 75°, 82.5°, 90°. The loading angle hole 2a has the same structure and size as the loading arm pin hole 1b, and a regular hexagonal first nut mounting groove 2b is concentrically arranged around each loading angle hole 2a for the installation of the matching pin connection system 7.

[0034] On the porous loading plate 1 2, two first specimen mounting arm holes 2c are arranged in parallel in the same vertical direction as the first loading angle hole 2a, and their size and structure are the same as those of the loading angle hole 2a, and second nut mounting grooves are arranged around them for cooperating with the specimen mounting mechanism 4 for installation.

[0035] The porous loading plate 2 21 is a derivative form of the porous loading plate 1 2 , which does not have the first nut mounting groove 2 b and the second nut mounting groove. It is used to cooperate with the porous loading plate 1 2 to clamp the loading arm 1 and the specimen mounting mechanism 4 in the middle, and cooperate with the disc fastening system 3 for fastening and installation.

[0036] Each set of disc fastening system includes: disc bolt 31, disc nut 32 and disc fastening gasket 33. The screw part of disc bolt 31 is half threaded, disc nut 32 is a regular hexagonal structure, and its size is the same as the second nut installation groove, and the inner diameter of disc fastening gasket 33 is slightly larger than the screw diameter of disc bolt 31.

[0037] like Figure 3 As shown, the three-leaf specimen 5 is in the shape of a "maple leaf", with three circular openings distributed every 120° from the center of the structure, and first specimen mounting holes 5a are concentrically opened at the three circular openings for mounting in conjunction with the specimen mounting mechanism 4. Two three-leaf specimens 5 are stacked with a center offset of 60° and connected to form an integral specimen through the connection form required for the test.

[0038] The structure of the thickness adjustment gasket 8 is the same as that of the three-leaf specimen 5, and the three ports thereof are provided with thickness adjustment gasket installation holes 8a which are the same as the specimen installation ports. The structure center of the thickness adjustment gasket 8 is provided with a hollow circular space to form a gasket hole 8b, which has the same size as the specimen connection groove 4c, and is used to ensure the normal installation of the specimen connection form with longitudinal space requirements. There is no specific requirement for the thickness of the thickness adjustment gasket 8, and its main purpose is to ensure that the thickness of the two three-leaf specimens 5 is consistent, thereby avoiding the generation of unnecessary torque.

[0039] The specimen mounting mechanism includes: a specimen mounting arm 41 and a specimen mounting platform 42. The specimen mounting arm 41 is a rectangular structure, and one end of the specimen mounting arm 41 is connected to the bottom of the specimen mounting platform 42, and the other end is provided with two second specimen mounting arm holes 4d opened in parallel, and the second specimen mounting arm holes 4d are the same size as the first specimen mounting arm holes 2c. The specimen mounting platform 42 has the same structure as the three-leaf specimen 5, both of which are "maple leaf-shaped", and one side of each circular opening is provided with a second specimen mounting hole 4b, and the other side is provided with a third nut mounting groove 4a, the second specimen mounting hole 4b is the same in position and size as the first specimen mounting hole, and the third nut mounting groove 4a is the same in structure and size as the first and second nut mounting grooves.

[0040] The specimen fastening system 6 includes: a specimen bolt 61, a specimen nut 62 and a specimen fastening gasket 63; the screw portion of the specimen bolt 61 is semi-threaded, one end of the specimen nut 62 is a regular hexagon, and its size is the same as the third nut mounting groove 4a, and the inner diameter of the specimen fastening gasket 63 is slightly larger than the screw diameter of the specimen bolt 61.

[0041] The pin connection system 7 includes: a loading arm connection pin 71 and a connection circlip ring 72. One end of the loading arm connection pin 71 is a regular hexagon, and its size is the same as that of the first nut mounting groove 2b, and it can be embedded therein. The other end of the loading arm connection pin 71 is provided with an annular groove 7a. The connection pin circlip ring 72 is a C-shaped structure with a notch, and its size is consistent with that of the annular groove 7a. The connection pin circlip ring 72 is matched with the annular groove 7a.

[0042] The specific installation process includes: After stacking two three-leaf test pieces 5 with the center deflected by 60 degrees, they are connected in the form required by the test to form an integrated test piece; In the present invention, as a preference, the connection form is point connection, which is at least one of spot welding, riveting, point bonding and bolt connection.

[0043] In another embodiment, the connection form may be: multi-point connection or surface connection.

[0044] Pass a loading arm connecting pin 71 through the loading angle hole 2a on the porous loading disk 1 2, the loading arm pin hole 1b, and the corresponding loading angle hole on the porous loading disk 2 1 in sequence; place the regular hexagonal end of the loading arm connecting pin 71 in the first nut mounting groove 2b to prevent axial rotation; insert the connecting pin retaining ring 72 into the annular groove 7a to limit the loading arm connecting pin 71, thereby completing the clamping installation of the loading arm 1 and the porous loading disk 2.

[0045] Place the two disc nuts 32 in the two second nut mounting grooves respectively, install the two disc bolts 31 coaxially with the two disc fastening washers 33 respectively, and then the disc bolts 32 pass through the first specimen mounting arm hole 2c, the second specimen mounting arm hole 4d, and the first specimen mounting arm hole 2c on the porous loading disk 21 in sequence; use an Allen wrench to screw the disc bolt 31 into the disc nut 32 to complete the clamping installation of the specimen mounting arm 41 and the porous loading disk 2.

[0046] Place three specimen nuts 62 in the three third nut installation grooves 4a respectively, assemble the specimen bolt 61 and the specimen fastening gasket 62 coaxially, and then pass through the first specimen installation hole 5a, the thickness adjustment gasket installation hole 8a (if not needed, it can be ignored), and the second specimen installation hole 4b in sequence, and screw the specimen bolt 61 into the specimen nut 62 with an inner hexagonal wrench to achieve the installation of one side of the three-leaf specimen, and the same is true for the other side. During the installation process, an L-shaped inner hexagonal wrench can be used to tighten the outer specimen bolt 61 through the rectangular notch on the porous loading plate, and the inner specimen bolt can be tightened by a long-bar inner hexagonal wrench through the gap between the porous loading plate 1 2 and the porous loading plate 2 21. Example 1

[0047] Assembling the loading arm 1 and the holes 2a with different loading angles includes: like Figure 4 As shown, the loading angle hole 2a includes: a first group of holes and a second group of holes, wherein the first group of holes includes: hole one 201, hole two 202, hole three 203, hole four 204, hole five 205, hole six 206, hole seven 207, hole eight 208, hole nine 209, hole ten 210, hole eleven 211, hole twelve 212, hole thirteen 213, and the second group of holes includes: hole fourteen 214, hole fifteen 215, hole sixteen 216, hole seventeen 217, hole eighteen 218, hole nineteen 219, hole twenty 220, hole twenty-one 221, hole twenty-two 222, hole twenty-three 223, hole twenty-four 224, hole twenty-five 225, hole twenty-six 226. According to the combination of different holes, the external force loading direction and the uniaxial tensile direction are at different angles (0°, 7.5°, 15°, 22.5°, 30°, 37.5°, 45°, 52.5°, 60°, 67.5°, 75°, 82.5°, 90°), thereby achieving different tension-shear ratio loading. The specific hole combinations corresponding to each angle are shown in Table 1.

[0048] Table 1 Description of loading angle hole combination and tension-shear ratio of the present invention

[0049] The combination of hole 1 and hole 2 can realize the transition of stress state from pure normal stress to pure shear stress, such as Figure 4 As shown, the loading center is taken as the origin O , decompose the combined stress into normal stress according to the loading angle s and shear stress t .

[0050] Normal stress s and shear stress t They can be expressed as:

[0051]

[0052] in, s is the normal stress; t is the shear stress; F is the failure load; S is the connection area; i is the loading angle.

[0053] Tension-shear ratio or It can be defined as normal stress s and shear stress t Ratio:

[0054] The specific tension-shear ratios at various loading angles are shown in Table 1.

[0055] The specific number of the loading angle holes 2a in the present invention is not required, and the number can be determined according to actual needs and the size of each component without affecting the normal function of each component. Example 2

[0056] The center of the specimen is connected using different connection methods, including: As shown in FIG5 , cross-sectional views of three different point connection forms of the three-leaf specimen 5 are shown; as shown in FIG5 (a), the centers of the two three-leaf specimens 5 are connected by a spot welding point 51; as shown in FIG5 (b), the center of the three-leaf specimen 5 is provided with a rivet mounting hole, and the centers of the two three-leaf specimens 5 are connected by a riveting point 52; as shown in FIG5 (c), the two three-leaf specimens 5 are connected by a bonding point 53.

[0057] The present invention is also compatible with various connection forms such as multi-point connection and surface connection.

[0058] It can be seen from the above embodiments that the biaxial tensile-shear loading test fixture provided by the present invention is compatible with a variety of connection forms and can freely control the tensile-shear ratio of the applied load according to actual needs. At the same time, it can effectively be compatible with point connection forms such as spot welding, riveting, and point bonding, and test the biaxial tensile-shear characteristics of the connection form, and has the characteristics of good compatibility, excellent operability and high reliability.

[0059] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes, and they can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A biaxial tensile shear loading test fixture compatible with various connection forms, characterized in that: include: Two pairs of upper and lower porous loading plates are arranged opposite to each other. In each pair of porous loading plates, two porous loading plates are arranged at intervals. The porous loading plates are a quarter of a circular structure and have a rectangular notch at the center. a plurality of loading angle holes spaced apart along the circumference of the porous loading disk; two loading arms, one end of which is disposed between two porous loading disks disposed at intervals; Two sets of pin connection systems, one end of which passes through the loading angle hole and the loading arm to detachably connect the loading arm to the porous loading plate; Two specimen mounting mechanisms are arranged opposite to each other, and one end of the specimen mounting mechanism is arranged between the two porous loading plates arranged at intervals; A plurality of disc fastening systems, one end of which passes through the porous loading disc and one end of the specimen mounting mechanism to detachably connect the specimen mounting mechanism to the porous loading disc; The test piece mechanism comprises two three-leaf test pieces, the two test pieces are connected at the center after being rotated 60 degrees relative to each other with the structure center as the origin; the two test pieces are respectively arranged at the other ends of the two test piece installation mechanisms; One end of a plurality of specimen fastening ties passes through the other end of the specimen mounting mechanism and the specimen, so as to detachably connect the specimen to the specimen mounting mechanism.

2. The biaxial tensile shear loading test fixture compatible with various connection forms according to claim 1 is characterized in that: Also includes: a plurality of first nut mounting grooves, which are regular hexagonal structures, are arranged concentrically with the plurality of loading angle holes, and are located on one of the porous loading disks of each pair of porous loading disks; a loading arm pin hole, which is disposed at one end of the loading arm; A loading arm connecting pin, one end of which is a regular hexagon and is matched with the first nut mounting groove; the other end of the loading arm connecting pin is provided with an annular groove along the circumferential direction; A connecting pin retaining ring, which is a C-shaped structure and is matched with the annular groove; Wherein, the loading arm pin hole is matched with the loading angle hole, and the other end of the loading arm connecting pin passes through the loading angle hole and the loading arm pin hole and is positioned by a connecting pin retaining spring arranged in the annular groove; A loading arm mounting hole is provided on the side surface of the other end of the loading arm.

3. The biaxial tensile shear loading test fixture compatible with various connection forms according to claim 2 is characterized in that: The test piece has three circular ends and a first test piece mounting hole is opened thereon.

4. The biaxial tensile shear loading test fixture compatible with various connection forms according to claim 3 is characterized in that: The fixing method between the two test pieces is at least one of welding, riveting, bolt connection and bonding.

5. The biaxial tensile shear loading test fixture compatible with various connection forms according to claim 4 is characterized in that: Also includes: A first specimen mounting arm hole is provided on the porous loading plate and is close to the rectangular notch; Wherein, on each of the porous loading plates, the number of the first specimen mounting arm holes is at least two.

6. The biaxial tension-shear loading test fixture compatible with various connection forms according to claim 5 is characterized in that: The test piece installation mechanism comprises: The specimen mounting arm is a rectangular structure, and one end of the arm is provided with at least two second specimen mounting arm holes; A specimen mounting platform, which is fixedly arranged at the other end of the specimen mounting arm; The specimen mounting platform has the same shape as the specimen, and a specimen connecting groove is provided in the middle of the specimen mounting platform, and second specimen mounting holes are provided on the circular ends of the specimen mounting platform.

7. The biaxial tension-shear loading test fixture compatible with various connection forms according to claim 6 is characterized in that: A second nut mounting groove is coaxially arranged with the first specimen mounting arm hole, and has the same structure as the first nut mounting groove, and both are located on the same porous loading plate.

8. The biaxial tension-shear loading test fixture compatible with various connection forms according to claim 7, characterized in that: The disc fastening system comprises: a disc bolt, a disc nut and a disc fastening gasket; One end of the disc bolt passes through the first specimen mounting arm hole and the second specimen mounting arm hole and is fixed by the disc nut. The disc fastening gasket is located between the disc bolt and the porous loading plate, and the disc nut is set in the second nut mounting groove.

9. The biaxial tension-shear loading test fixture compatible with various connection forms according to claim 8, characterized in that: The specimen fastening system comprises a matched specimen bolt, a specimen nut and a specimen fastening gasket; One end of the specimen bolt passes through the first specimen mounting hole and the second specimen mounting hole in sequence, and is then fixed by the specimen nut; The specimen fastening gasket is arranged between the specimen bolt and the specimen mounting platform.

10. The biaxial tension-shear loading test fixture compatible with various connection forms according to claim 9, characterized in that: The number of the loading angle holes is 13, and the angles between the loading angle holes and the vertical direction are: 0°, 7.5°, 15°, 22.5°, 30°, 37.5°, 45°, 52.5°, 60°, 67.5°, 75°, 82.5°, and 90° respectively.

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