A multi-directional mixed tension-compression-shear loading test fixture and test method

Abstract

This invention provides a multi-directional hybrid tensile-shear loading test fixture and method, comprising: a clamp connection system, a perforated clamping plate system, a clamping system, and a bolt connection system; wherein the clamping system, clamp connection system, and perforated clamping plate system are mechanically connected and fixed by the bolt connection system, the clamping system clamps the test specimen at the dovetail end, and the exposed gap in the middle of the clamping system is the part of the test specimen for mechanical performance evaluation. During the test, the multi-directional loading test fixture and test specimen are installed according to the test requirements and connected to the clamp of the tensile testing machine to perform mechanical performance testing. The multi-directional loading test fixture and method provided by this invention can perform tensile, shear, and multi-directional hybrid tensile-shear mechanical performance tests on multi-layer block additive manufacturing lattice structures, and can also be used to measure the tensile, shear, and multi-directional hybrid tensile-shear mechanical performance tests of other block structures with large thickness and width.

Description

Technical Field

[0001] This invention belongs to the field of mechanical property testing technology for structures or materials, and specifically relates to a multi-directional hybrid tensile-shear loading test fixture and test method, which is suitable for multi-layer block additive manufacturing lattice structure materials or other block structures with large thickness and width. Background Technology

[0002] Lightweighting is a perpetual pursuit in the research and development of aerospace structures and materials. Lattice material structures possess numerous superior properties, including lightweight and high strength, thermal insulation and heat dissipation, vibration reduction and energy absorption, thus attracting widespread attention from scholars and currently being applied in various industries such as aviation, aerospace, and shipbuilding. In recent years, the rapid development of additive manufacturing technology has greatly promoted the large-scale manufacturing and use of lattice structures, with an increasing number of cell configurations being designed, manufactured, and put into use.

[0003] In engineering design, lattice structures are often used in the form of multi-layered block structures with skins. Mechanical properties are the most important parameters in the design of such lattice structures. Obtaining parameters such as strength and stiffness can better guide the engineering application design of lattice structures.

[0004] Currently, mechanical performance testing of multi-layered block lattice structures focuses primarily on uniaxial tension, compression, and impact, with little research on testing under multiaxial tension-shear mixed conditions. However, multiaxial mixed stress states are a primary form of load-bearing capacity for lattice structures in engineering applications. Therefore, testing the multiaxial tension-shear mixed mechanical properties of lattice structures is crucial.

[0005] The single-lap configuration shear test method used in the study of lattice mechanical properties has excessively long and large test specimens, an overly cumbersome test system, and high material consumption, making it impossible to study the mechanical properties under multi-directional mixed loads.

[0006] The traditional shear test method, which uses adhesive bonding and clamps to connect both ends, has limitations in testing lattice structures. This is because the nonlinear mechanical constitutive properties of the adhesive bonding are difficult to characterize, and the interface strength is too low for testing under large loads. Boundary constraints, on the other hand, significantly enhance the mechanical properties of lattice structures and are a commonly used structural form in engineering applications. Therefore, this method has significant limitations in testing the performance of lattice structures.

[0007] Traditional methods for testing the multi-directional mechanical properties of materials are only suitable for multi-directional mechanical property testing of sheet-like small specimens. They cannot be used for testing the multi-directional mechanical properties of large-scale structures and may cause damage to non-test sections. Summary of the Invention

[0008] To overcome the shortcomings of existing technologies, the inventors conducted intensive research and designed a multi-directional loading test fixture and test method for testing the mechanical properties of multi-layer block lattice structures. This fixture can provide combined tensile, pure shear, and multi-directional mixed tensile-shear loads. The device has a simple structure, is easy to operate, and can realize multi-directional mechanical property tests at the large-size structural level without affecting the stability of non-tested structural sections, thus completing this invention.

[0009] The technical solution provided by this invention is as follows:

[0010] Firstly, a multi-directional hybrid tensile-shear loading test fixture includes:

[0011] The chuck connection system includes two identical chuck connection plates. One end of each chuck connection plate is a clamping end, which is connected to the upper chuck and lower chuck of the mechanical testing machine, respectively. The other end is fixedly connected to a multi-hole chuck plate through a threaded connector.

[0012] The multi-hole clamping plate system includes four identical multi-hole clamping plates. Multiple sets of first mounting holes for fixing the clamping head connecting plate and second mounting holes for fixing the clamp are machined on the vertical surface of the multi-hole clamping plate. The multiple sets of first mounting holes make the external force loading direction form different angles with the uniaxial tensile direction. Two multi-hole clamping plates are overlapped to form a clamping assembly corresponding to the mounting holes, which clamps the clamping head connecting plate and the clamp.

[0013] The clamping system includes two identical clamps, which are mounted opposite each other on two sets of clamping assemblies. The clamps are machined with snap-fit ​​grooves to engage with the two ends of the test piece.

[0014] The bolted connection system includes a movable threaded connector and a fixed threaded connector. The movable threaded connector fixes the chuck connecting plate to the clamping assembly through a first mounting hole, and the fixed threaded connector fixes the clamp to the clamping assembly through a second mounting hole.

[0015] Secondly, a multi-directional mixed tensile-shear loading test method is implemented using the multi-directional mixed tensile-shear loading test device described in the first aspect. By fixing the clamp connecting plate to different groups of first mounting holes, the direction of external force loading is at different angles to the uniaxial tensile direction, and a multi-directional mixed tensile-shear loading test is implemented.

[0016] The multi-directional hybrid tensile-shear loading test fixture and test method provided by the present invention have the following beneficial effects:

[0017] (1) The present invention provides a multi-directional hybrid tensile-shear loading test fixture and test method, which realizes the mechanical performance test of multi-layer block lattice structure under large load, multiple angles and boundary constraint, including uniaxial tension, pure shear and hybrid tensile-shear performance test;

[0018] (2) The present invention provides a multi-directional hybrid tensile-shear loading test fixture and test method. By rationally designing the hole orientation layout of the multi-hole clamping plate, the test fixture is compact, small in size, light in weight, and high in strength. It avoids the processing of large arc sections of traditional test fixtures, and the overall structure is easy to process. At the same time, the whole set of fixtures adopts a standard bolt connection, which is convenient to install and simple to disassemble.

[0019] (3) The present invention provides a multi-directional hybrid tensile-shear loading test fixture and test method, which overcomes the damage to the non-test section of the lattice structure by the traditional test fixture through the design of the groove bottom angle of the fixture system and the design of the extension section of the closing end;

[0020] (4) The multi-directional hybrid tensile-shear loading test fixture and test method provided by the present invention do not require other structural components, can be directly used with a universal testing machine for testing, and the method of use is simple;

[0021] (5) The present invention provides a multi-directional hybrid tensile-shear loading test fixture and test method, which is applicable to the mechanical property testing of various structures such as other block-shaped multi-material filled multi-layer lattice hybrid structures, multi-layer multi-level lattice structures, multi-layer gradient lattice structures, and conventional material block structures in the directions of unidirectional tensile, pure shear and multi-directional angular tensile-shear. Attached Figure Description

[0022] Figure 1 The diagram shown is a three-dimensional structural schematic of the clamp structure in Example 1 of this disclosure.

[0023] Figure 2 The diagram shown is a three-dimensional structural schematic of Example 1 of this disclosure after the upper clamping system has been installed.

[0024] Figure 3 The diagram shown is a planar structural schematic of the perforated clamping plate system in Example 1 of this disclosure.

[0025] Figure 4 The diagram shown is a three-dimensional structural schematic of the fixture structure in Example 2 of this disclosure.

[0026] Figure 5 The diagram shown is a three-dimensional structural schematic of the fixture structure in Example 3 of this disclosure.

[0027] Figure 6 The diagram shown is a three-dimensional structural schematic of the fixture structure in Example 4 of this disclosure.

[0028] Figure 7 The diagram shown is a three-dimensional structural schematic of the fixture structure in Example 5 of this disclosure.

[0029] Figure 8 The diagram shown is a three-dimensional structural schematic of the fixture structure in Example Six of this disclosure.

[0030] Figure 9 The diagram shown is a three-dimensional structural schematic of the fixture structure in Example 7 of this disclosure.

[0031] Figure 10 The diagram shows a three-dimensional structural schematic of the clamp connection system in Example 1 of this disclosure.

[0032] Figure 11 The diagram shown is a three-dimensional structural schematic of the clamping system in Example 1 of this disclosure.

[0033] Figure 12 The diagram shows a three-dimensional structural schematic of a multi-layered block lattice test specimen as shown in Example 1 of this disclosure. Detailed Implementation

[0034] The features and advantages of the present invention will become clearer and more apparent from the following detailed description.

[0035] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments. Although various aspects of embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated otherwise.

[0036] This invention provides a multi-layered block lattice structure multi-directional hybrid tensile-shear loading test fixture, such as... Figures 1 to 11 As shown, it includes a clamp connection system 10, a multi-hole clamp system 20, a clamp system 30, and a bolt connection system 40.

[0037] like Figure 1 , 2 As shown, the multi-hole clamping plate system 20 includes four identical multi-hole clamping plates (201-204). Multiple sets of first mounting holes for fixing clamp connecting plates (101, 102) and second mounting holes for fixing clamps (301, 302) are machined on the vertical surface of the multi-hole clamping plates (201-204). The multiple sets of first mounting holes make the direction of external force loading form different angles with the direction of uniaxial tension. Two multi-hole clamping plates (201-202, 203-204) overlap to form a clamping assembly corresponding to the mounting holes, clamping the clamp connecting plates (101, 102) and the clamps (301, 302).

[0038] like Figure 3As shown, the porous clamping plate (201-204) is machined with seven sets of first mounting holes at angles of 0°, 15°, 30°, 45°, 60°, 75°, and 90° to the uniaxial tensile direction. Preferably, each set of first mounting holes includes at least two through holes, such as 2-4 through holes arranged in a matrix. The center of the through holes is located on one or two arcs centered on the geometric center of the test piece 5, or the center of the through holes is located in the radial direction centered on the geometric center of the test piece 5. The hole diameter of each set of first mounting holes is the same, which facilitates installation.

[0039] The locations of the multiple mounting holes were rationally arranged based on strength and space utilization studies, taking into account assembly interference. The center of the first mounting hole in each group was set on a multi-layered circular arc centered on the geometric center of the test piece 5. The first mounting holes in the 15° and 75° directions were located on the innermost circular arc closest to the test piece 5. The first mounting holes in the 0°, 30°, 60°, and 90° directions were located on the same circular arc in the middle layer, and the first mounting hole in the 45° direction was located on the outermost circular arc. That is, 0° was defined as the uniaxial tensile direction, 90° as the pure shear direction, and the remaining 15° to 75° were defined as tensile-shear directions 1 to 5 respectively. Tests were conducted under different loading directions as follows: Figure 1 , 4 As shown in -9.

[0040] Of course, if the size requirements for the perforated clamp (201-204) are relaxed, the number of first mounting holes can be more, such as six first mounting holes in the 15° and 75° directions. Two of these holes are set on the innermost arc closest to the test piece 5, two are set on the same arc in the middle layer, and the remaining two are set on the outermost arc. If there are strict requirements for the size of the perforated clamp (201-204) or it is unnecessary to set an excessively large perforated clamp (201-204), the number of first mounting holes can be less, such as two or four, and the appropriate arc position can be selected.

[0041] To ensure testing flexibility and reduce stress on the perforated clamps (201-204) during testing, each group of first mounting holes includes two through holes centered on a multi-layered circular arc with the geometric center of the test piece 5 as the center. The line connecting the centers of each group of first mounting holes is perpendicular to the corresponding external force loading direction, and the perpendicular distances are equal. The perpendicular bisectors of the line connecting each group of first mounting holes are radial lines, and the radial lines of each group of first mounting holes intersect at the geometric center of the test piece 5.

[0042] like Figure 10As shown, the chuck connection system 10 includes two identical chuck connection plates (101, 102). One end of each chuck connection plate (101, 102) is a clamping end, which is connected to the upper and lower chucks of the mechanical testing machine, respectively. The other end is fixedly connected to a multi-hole clamping plate via a threaded connector. Generally, the upper and lower chucks of a mechanical testing machine are sufficient to clamp the clamping end; however, if the load is too large and the clamping method cannot fix the clamping end, holes are drilled at the clamping end, and the machine is fixed to the mechanical testing machine via a threaded connector.

[0043] The end of the clamp connecting plate (101, 102) connected to the multi-hole clamping plate (201-204) has at least two through holes perpendicular to the plate surface, serving as mounting holes for fixing the clamp connecting plate (101, 102) and the multi-hole clamping plate (201-204). The perpendicular bisector of the connecting line of these through holes is the central symmetry line of the entire clamp connecting plate (101, 102). The distance of the through hole from the central symmetry line is equal to the distance of each group of first mounting holes on the multi-hole clamping plate (201-204) from its central symmetry line, and the through holes also have the same diameter as the first mounting holes. This ensures that the through holes can be installed in conjunction with the multi-hole clamping plate (201-204).

[0044] The clamping system 30 includes two identical clamps (301, 302), which are mounted opposite each other on two sets of clamping components. The clamps are machined with snap-fit ​​grooves to snap-fit ​​with the two ends of the test piece.

[0045] like Figure 11 As shown, the end of the clamps (301, 302) connected to the perforated clamps (201-204) has at least two through holes perpendicular to the plate surface, serving as mounting holes for fixing the clamps (301, 302) and the perforated clamps (201-204). These through holes correspond in position and have the same diameter as the second mounting hole on the perforated clamps (201-204), ensuring that they can be installed in conjunction with the perforated clamps (201-204).

[0046] The end of the clamps (301, 302) connected to the test piece 5 is provided with a dovetail groove structure as a locking groove, with a groove bottom angle of 30° to 60°, such as 45°. The dovetail groove structure has an extension section at the closing end to ensure that the test piece 5 is in a semi-enclosed state, protecting the end of the test piece from initial failure. Corresponding to the clamps, the test piece 5 is manufactured by additive manufacturing or investment casting, etc., and its two ends have a dovetail structure that matches the clamps (301, 302) so as to constrain the degrees of freedom of the test piece 5 other than the loading direction, such as... Figure 12 As shown.

[0047] The inner surface of the dovetail groove structure of the fixture (301, 302) is similar to the outer contour of the dovetail structure of the test piece 5. At the same time, the two opposite inclined sides of the dovetail groove structure are fitted with the test piece 5 with a clearance. For example, there is a gap of about 0.5mm between the dovetail groove structure and the test piece 5. The gap is left to facilitate the smooth installation of the test piece. The bottom edge of the dovetail groove structure is fitted with the test piece 5 with a transition.

[0048] Considering Saint-Venant's principle, a transition zone is added between the dovetail structure of test piece 5 and the test section. The transition zone and the dovetail structure are rounded at the joint to prevent stress concentration-induced failure in the non-test section. The test section can be a blocky multi-layer block lattice structure, a multi-material filled multi-layer lattice hybrid structure, a multi-layer multi-level lattice structure, a multi-layer gradient lattice structure, or a conventional material block structure, etc.

[0049] In the tensile-shear test at 15° to 75°, the geometric center of the test piece 5 after installation is located on the perpendicular bisector of the line connecting the centers of the two sets of second mounting holes, ensuring that the geometric center of the test piece is in the loading direction. In the uniaxial tensile or pure shear test, the geometric center of the test piece 5 after installation is not required to be located on the perpendicular bisector of the line connecting the centers of the two sets of second mounting holes; it is only required that the test piece 5 can be successfully fixed between the two clamps (301, 302).

[0050] The bolt connection system 40 includes movable threaded connectors (413, 416, 419, 422) and fixed threaded connectors (401, 404, 407, 410). The movable threaded connectors fix the chuck connecting plates (101, 102) to the clamping assembly through the first mounting hole, and the fixed threaded connectors fix the clamps (301, 302) to the clamping assembly through the second mounting hole.

[0051] Fixed threaded connectors (401, 404, 407, 410) include a set of bolts, nuts, and washers. The outer diameter of the nut is equal to the outer diameter of the first mounting hole. Movable threaded connectors (413, 416, 419, 422) also include a set of bolts, nuts, and washers. The outer diameter of the nut is equal to the outer diameter of the second mounting hole. The diameters of the first and second mounting holes are determined based on the specifications of the standard bolts, and assembly interference is considered in the mounting hole layout design. The bolt length ensures that the remaining portion after connection with other systems is longer than the nut thickness.

[0052] The present invention also provides a method for multi-directional mixed tensile-shear loading test of a multi-layer block lattice structure. The method uses the multi-directional mixed tensile-shear loading test fixture described in the first aspect. By fixing the clamp connecting plates (101, 102) to different groups of first mounting holes, the direction of external force loading is at different angles to the uniaxial tensile direction, and the multi-directional mixed tensile-shear loading test is carried out.

[0053] Seven examples are given, as the only difference between the seven examples is the loading direction angle. In specific installation tests, the only difference is the installation position of the movable bolt. The following example uses Example 1 as an example to introduce the installation fixture method and measurement method in detail. The other embodiments only provide overall structural installation diagrams and brief descriptions.

[0054] The names and definitions of the seven examples are as follows: Example 1, mechanical property measurement under pure shear test; Example 2, mechanical property measurement under uniaxial tensile test; Example 3, mechanical property measurement under a 15° tensile-shear mixed test; Example 4, mechanical property measurement under a 30° tensile-shear mixed test; Example 5, mechanical property measurement under a 45° tensile-shear mixed test; Example 6, mechanical property measurement under a 60° tensile-shear mixed test; Example 7, mechanical property measurement under a 75° tensile-shear mixed test.

[0055] Example 1

[0056] (I) Installing the clamps

[0057] 1) Install the upper fixing clamp system and connect the multi-hole clamp I 201, multi-hole clamp II 202 and clamp I 301 using fixing threaded connectors (401, 404). Clamp I 301 is clamped between multi-hole clamp I 201 and multi-hole clamp II 202.

[0058] 2) Install the upper clamping system. Connect the upper fixed clamping system and the chuck connecting plate I 101 using movable threaded connectors (413, 416). The chuck connecting plate I 101 is clamped between the perforated clamping plate I 201 and the perforated clamping plate II 202. Installation complete as follows: Figure 2 As shown.

[0059] 3) Use the upper chuck of the universal testing machine to clamp the clamping end of the chuck connecting plate I 101. To prevent slippage due to insufficient friction, sandpaper of appropriate thickness can be added between the clamping end and the upper chuck. The universal testing machine mentioned here includes, but is not limited to, the INSTRON universal testing machine and the MTS universal testing machine.

[0060] 4) Install the lower fixing clamp system and connect the perforated clamp III 203, perforated clamp IV 204 and clamp II 302 using the fixing bolt system (407, 410). Clamp II 302 is clamped between perforated clamp III 203 and perforated clamp IV 204.

[0061] 5) Install the lower clamping system and connect the lower fixed clamping system and the chuck connecting plate II 102 using the movable bolt system (419, 422). The chuck connecting plate II 102 is clamped between the perforated clamping plate III 203 and the perforated clamping plate IV 204.

[0062] 6) Use the lower chuck of the universal testing machine to clamp the clamping end of the chuck connecting plate II 102. Similarly, to prevent slippage due to insufficient friction, sandpaper of appropriate thickness can be added between the clamping end and the lower chuck. The relative clamping position of the lower chuck is the same as that of the upper chuck, specifically meaning that the geometric centers of the chuck connecting plate I 101 and the chuck connecting plate II 102 are located on the same plumb line.

[0063] 7) Adjust the lower clamp of the universal testing machine to align the upper and lower clamps. Specifically, this means that the center lines of clamp I301 and clamp II 302 are on the same horizontal line.

[0064] 8) Install the test piece. Place the dovetail-end test piece 5 at the center position between clamp I 301 and clamp II 302, so that the geometric center of the test piece 5 is located on the plane of symmetry of clamp I 301 and clamp II 302. A suitable amount of sandpaper can be added to clamp I 301 and clamp II 302 to fill the gap between the dovetail end of the test piece 5 and clamp I 301 and clamp II 302.

[0065] (II) Measurement

[0066] Adjust the lower clamp of the universal testing machine downwards to completely fix the test piece 5.

[0067] Adjust the test parameters of the universal testing machine, such as tensile loading rate, protection position, and loading force, to carry out relevant mechanical property tests and collect data.

[0068] Example 2:

[0069] Installation of fixtures and measurement methods: Remove the four movable bolts 413, 416, 419, and 422 from Example 1, and proceed as follows... Figure 4 Install according to the installation structure diagram.

[0070] Example 3:

[0071] Installation of fixtures and measurement methods: Remove the four movable bolts 413, 416, 419, and 422 from Example 1, and proceed as follows... Figure 5 Install according to the installation structure diagram.

[0072] Example 4:

[0073] Installation of fixtures and measurement methods: Remove the four movable bolts 413, 416, 419, and 422 from Example 1, and proceed as follows... Figure 6 Install according to the installation structure diagram.

[0074] Example 5:

[0075] Installation of fixtures and measurement methods: Remove the four movable bolts 413, 416, 419, and 422 from Example 1, and proceed as follows... Figure 7 Install according to the installation structure diagram.

[0076] Example 6:

[0077] Installation of fixtures and measurement methods: Remove the four movable bolts 413, 416, 419, and 422 from Example 1, and proceed as follows... Figure 8 Install according to the installation structure diagram.

[0078] Example 7:

[0079] Installation of fixtures and measurement methods: Remove the four movable bolts 413, 416, 419, and 422 from Example 1, and proceed as follows... Figure 9 Install according to the installation structure diagram.

[0080] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

[0081] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A multi-directional hybrid tensile-shear loading test fixture, characterized in that, include: The chuck connection system includes two identical chuck connection plates. One end of each chuck connection plate is a clamping end, which is connected to the upper chuck and lower chuck of the mechanical testing machine, respectively. The other end is fixedly connected to the multi-hole chuck plate through a threaded connector. The multi-hole clamping plate system includes four identical multi-hole clamping plates. Two multi-hole clamping plates are overlapped to form a clamping assembly corresponding to the mounting holes, which clamps the chuck connecting plate and the clamp. Multiple sets of first mounting holes for fixing the chuck connecting plate and second mounting holes for fixing the clamp are machined on the vertical surface of the multi-hole clamping plate. The multiple sets of first mounting holes make the external force loading direction form different angles with the uniaxial tension direction. The clamping system includes two identical clamps, which are mounted opposite each other on two sets of clamping assemblies. The clamps are machined with snap-fit ​​grooves to engage with the two ends of the test piece. The bolted connection system includes a movable threaded connector and a fixed threaded connector. The movable threaded connector fixes the chuck connecting plate to the clamping assembly through a first mounting hole, and the fixed threaded connector fixes the clamp to the clamping assembly through a second mounting hole.

2. The multi-directional hybrid tensile-shear loading test fixture according to claim 1, characterized in that, The porous clamp is machined with seven sets of first mounting holes at 0°, 15°, 30°, 45°, 60°, 75° and 90° to the uniaxial tensile direction. Each set of first mounting holes includes at least two through holes. The center of the through holes is located on an arc with the geometric center of the test piece as the center, or the center of the through holes is located in the radial direction with the geometric center of the test piece as the center.

3. The multi-directional hybrid tensile-shear loading test fixture according to claim 2, characterized in that, The center of each group of first mounting holes is located on a multi-layered arc with the geometric center of the test piece as the center. The first mounting holes located in the 15° and 75° directions are located on the innermost arc closest to the test piece. The first mounting holes located in the 0°, 30°, 60° and 90° directions are located on the same arc in the middle layer. The first mounting hole located in the 45° direction is located on the outermost arc.

4. The multi-directional hybrid tensile-shear loading test fixture according to claim 3, characterized in that, Each group of first mounting holes includes two through holes with their centers set on multiple circular arcs centered on the geometric center of the test piece. The line connecting the centers of each group of first mounting holes is perpendicular to the corresponding external force loading direction, and the perpendicular distances are equal. The perpendicular bisectors of the line connecting each group of first mounting holes are radial lines, and the radial lines of each group of first mounting holes intersect at the geometric center of the test piece.

5. The multi-directional hybrid tensile-shear loading test fixture according to claim 1, characterized in that, The end of the clamp connecting plate that connects to the multi-hole clamp plate has at least two through holes perpendicular to the plate surface, which serve as mounting holes for fixing the clamp connecting plate and the multi-hole clamp plate. The perpendicular bisector of the connecting line of the through holes is the central symmetry line of the entire clamp connecting plate. The distance of the through hole from the central symmetry line is equal to the distance of each group of first mounting holes on the multi-hole clamp plate from its central symmetry line, and is equal to the diameter of the first mounting hole.

6. The multi-directional hybrid tensile-shear loading test fixture according to claim 1, characterized in that, The end of the clamp connected to the multi-hole clamp has at least two through holes perpendicular to the plate surface, which serve as mounting holes for fixing the clamp to the multi-hole clamp. The through holes correspond to the positions of the second mounting holes on the multi-hole clamp and have the same diameter.

7. The multi-directional hybrid tensile-shear loading test fixture according to claim 1, characterized in that, The end of the clamp connected to the test piece is provided with a dovetail groove structure as a clamping groove, and the closing end of the dovetail groove structure has an extension section; the two ends of the test piece are dovetail structures with shapes similar to the inner surface of the dovetail groove structure of the clamp.

8. The multi-directional hybrid tensile-shear loading test fixture according to claim 7, characterized in that, The two opposite inclined sides of the dovetail groove structure are clearance-fitted with the test piece, and the bottom edge of the dovetail groove structure is transition-fitted with the test piece.

9. The multi-directional hybrid tensile-shear loading test fixture according to claim 1, characterized in that, The fixed threaded connector includes a set of bolts, nuts, and washers, with the outer diameter of the nut equal to the outer diameter of the first mounting hole. The movable threaded connector includes a set of bolts, nuts, and washers, with the outer diameter of the nut equal to the outer diameter of the second mounting hole.

10. The multi-directional hybrid tensile-shear loading test fixture according to claim 7, characterized in that, A transition zone is added between the dovetail structure and the test section of the test piece, and the corners where the transition zone meets the dovetail structure are rounded.

11. The multi-directional hybrid tensile-shear loading test fixture according to claim 2, characterized in that, In the tensile-shear test at 15°~75°, the geometric center of the test piece after installation is located on the perpendicular bisector of the line connecting the centers of the two sets of second mounting holes, so that the geometric center of the test piece is in the loading direction. In uniaxial tensile or pure shear tests, the geometric center of the test piece after installation is not required to be located on the perpendicular bisector of the line connecting the centers of the two sets of second mounting holes; it is only required that the test piece can be successfully fixed between the two clamps.

12. A multi-directional hybrid tensile-shear loading test method, characterized in that, The test is carried out using the multi-directional mixed tensile-shear loading fixture as described in any one of claims 1 to 11. By fixing the clamp connecting plate to different groups of first mounting holes, the direction of external force loading is at different angles to the uniaxial tensile direction, and the multi-directional mixed tensile-shear loading test is carried out.

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