Test clamp and shear strength test system

Abstract

The invention discloses a test fixture and a shear strength test system. The test fixture comprises a plurality of shear plates, two clamping blocks, a plurality of reinforcing sheets, a plurality of first-class mechanical fasteners and a plurality of second-class mechanical fasteners. The shear strength test system comprises a test fixture, a test piece to be tested and a testing machine, the to-be-tested test piece is used for being tightly connected into a mold sleeve piece formed by tightly connecting a plurality of shear plates through a plurality of reinforcing sheets of which the front and back surfaces are adhered to each non-impact damage area; and the testing machine is used for testing the shear strength of an impact damage area surrounded by each non-impact damage area on the to-be-tested test piece by applying a tensile load after establishing a connection relationship with the mold suite through the two clamping blocks. The test fixture provides reliable test support by means of the structure and the connection mode with good universality, and adapts to diversified test scenes in material science research and engineering application.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aviation industry manufacturing, and particularly relates to a test fixture and a shear strength test system. BACKGROUND

[0002] In the field of aviation industry manufacturing, with the wide application of composite materials, it is crucial to accurately grasp the mechanical properties thereof, especially for the key parameter of post-impact shear residual strength of a composite laminate, which is directly related to the reliability and durability thereof under many complex working conditions.

[0003] Previously, due to the limitation of traditional test methods, in order to obtain the important data, the technical personnel relied on the plane biaxial static load test method of the composite laminate. However, this traditional test method has significant disadvantages. On the one hand, the professional biaxial loading equipment not only has high purchase cost, but also greatly increases the test hardware investment in daily maintenance, calibration and other aspects; on the other hand, in order to meet the strict requirements of the biaxial loading test, the raw materials, forming process, machining precision and other aspects need to be controlled at a high standard, which increases the manufacturing cost. This undoubtedly brings great consumption in manpower, time and other aspects, and seriously restricts the related research and production efficiency. SUMMARY

[0004] In order to overcome the above-mentioned defects, the present application provides a test fixture and a shear strength test system to solve the problems of complex test piece manufacturing, high fixture cost, non-repeatability, test calibration and cumbersome process, and high requirements for the testing machine in the traditional test method for obtaining the post-impact shear residual strength.

[0005] In a first aspect, an embodiment of the present application provides a test fixture for testing the shear strength of a test piece, comprising:

[0006] a plurality of shear plates, two clamping blocks, a plurality of reinforcing sheets, a plurality of first mechanical fasteners and a plurality of second mechanical fasteners; each shear plate has a first assembly hole at both ends, and each shear plate body and each reinforcing sheet body has a plurality of second assembly holes matched thereon;

[0007] The plurality of shear plates are arranged in pairs to obtain a plurality of shear plate pairs, and the pairs of shear plates are assembled by closing the first assembly holes and fastened by the first mechanical fasteners to obtain a mold set;

[0008] The plurality of reinforcing sheets are combined in pairs and are used to be pasted on the non-impact damage areas of the test piece, so that the test piece is nested and assembled with the mold set through the second assembly holes on the reinforcing sheets, and is fastened to the mold set by the second mechanical fasteners; each non-impact damage area has a plurality of second assembly holes matched with the reinforcing sheet body thereon;

[0009] Each of the two clamping blocks is fastened to the mold set via the first type of mechanical fastener at one end and is configured to be connected to the testing machine at the other end for transmitting the tensile load applied by the testing machine to the impact damage area surrounded by the non-impact damage areas on the test piece to perform the shear strength test.

[0010] Optionally, the first type of mechanical fastener is a pin, and the second type of mechanical fastener is a connecting bolt.

[0011] Further, the two clamping blocks include a first U-shaped clamping block and a second U-shaped clamping block, wherein:

[0012] The connecting ears of the first U-shaped clamping block and the second U-shaped clamping block are fastened to the mold set via the first type of mechanical fastener, and the clamping arms of the first U-shaped clamping block and the second U-shaped clamping block are configured to be connected to the testing machine.

[0013] The first U-shaped clamping block and the second U-shaped clamping block adopt an adjustable-angle universal joint structure for adapting to test pieces of different thicknesses.

[0014] In a second aspect, the embodiments of the present application also provide a shear strength test system, which includes a test fixture for performing a shear strength test on a test piece, the test piece, and a testing machine.

[0015] The test piece is fastened to the mold set obtained by fastening a plurality of shear plates via a plurality of reinforcing sheets pasted on the front and back surfaces of the non-impact damage areas.

[0016] The testing machine is configured to perform a shear strength test on the impact damage area surrounded by the non-impact damage areas on the test piece by applying a tensile load after the two clamping blocks are connected to the mold set.

[0017] The test piece is a pre-cut cross-like truncated rectangle, which includes four rectangular impact damage areas and one cross-like impact damage area, and each impact damage area surrounds the impact damage area in four directions; wherein the gap area between each pair of impact damage areas is used to accommodate the first type of mechanical fastener.

[0018] Correspondingly, the number of shear plates and reinforcing sheets is eight, and the number of the first type of mechanical fasteners is four.

[0019] Optionally, the testing machine is a universal testing machine.

[0020] The clamping arms of the first U-shaped clamping block and the second U-shaped clamping block are fastened to the mold set via two first type of mechanical fasteners arranged at intervals.

[0021] The connecting lug of the first U-shaped clamping block is configured to be connected with the crossbeam of the testing machine, and the connecting lug of the second U-shaped clamping block is configured to be connected with the base of the testing machine;

[0022] The testing machine is particularly used for testing the shear strength of the impact damage area of the test piece nested in the mold set by applying a tensile load in the axial direction in a diagonal tensile manner.

[0023] Further, the system also includes a calculation control unit;

[0024] The calculation control unit is electrically connected with the testing machine, is configured to read the real-time tensile load of the testing machine, determine the moment when the impact damage area is destroyed according to the real-time tensile load, take the current tensile load of the testing machine at the moment when the impact damage area is destroyed as the maximum tensile load, and calculate the ultimate shear strength.

[0025] Optionally, the calculation control unit is also configured to judge whether the change rate of the tensile load applied by the testing machine at the current moment exceeds the specified multiple of the set threshold value in real time under the constant loading rate of the testing machine.

[0026] If yes, the current moment is determined as the moment when the impact damage area is destroyed.

[0027] Further, the calculation control unit also includes a shear strength calculation formula for solving the shear strength of the test piece:

[0028]

[0029] Wherein, τ SAI is the ultimate shear strength to be solved, with the unit of MPa; P max is the target tensile load, with the unit of N; A is the cross-sectional area of the impact damage area, which is the product of the width of the impact damage area and the thickness of the test piece, with the unit of mm 2 .

[0030] The working process of the whole test fixture system is the result of the cooperation of various components. Specifically, components such as a shear plate and a clamping block are made of stainless steel and can be reused, thereby reducing the high cost caused by frequent replacement of fixtures. The durable design greatly prolongs the service life of the fixture and reduces long-term investment costs. Through the ingenious design of the shear plate, the reinforcing plate, the mechanical fastener, and the clamping block with the adjustable angle universal joint structure, the assembly process of the test piece and the fixture becomes simple and fast. The components are closely matched and the connection mode is intuitive, so that the operator can quickly complete the installation and debugging, further improving the test frequency per unit time. Whether it is for a composite laminate or other materials with similar shear strength test requirements, the fixture design can provide reliable test support with its good universal structure and connection mode, and adapt to diversified test scenarios in material science research and engineering applications.

[0031] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present application, nor is it intended to limit the scope of the present application. Other features of the present application will become apparent from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0033] Figure 1 is a front view of a three-dimensional structure of a test fixture for shear strength testing of a test piece according to embodiment one of the present application;

[0034] Figure 2 is a partial internal planar structure exploded schematic view of a mold kit according to embodiment one of the present application;

[0035] Figure 3 is a three-dimensional structure side view of a test fixture according to embodiment one of the present application;

[0036] Figure 4 is a connection relationship schematic view of a shear strength test system according to embodiment two of the present application;

[0037] Figure 5 is a planar structure schematic view of a test piece to be tested according to embodiment two of the present application;

[0038] Figure 6 is a working schematic view of a shear strength test system according to embodiment two of the present application;

[0039] Figure 7 Fig. 1 is a schematic diagram of the size of a test piece according to an embodiment of the present application. DETAILED DESCRIPTION

[0040] In order to make the technical personnel in the art better understand the present application, the following will be combined with the drawings in the embodiments of the present application, the technical solutions in the embodiments of the present application are described clearly and completely, obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by the person skilled in the art without making creative labor should belong to the scope of protection of the present application.

[0041] It should be noted that the terms "first", "second" and the like in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0042] Embodiment one

[0043] Figure 1 Fig. 1 is a front view of a test fixture for shear strength testing of a test piece according to an embodiment of the present application, as shown, the test fixture (S1) comprises: Figure 1

[0044] a plurality of shear plates (S10), two clamping blocks (S20), a plurality of reinforcing sheets (S30), a plurality of first mechanical fasteners (S40) and a plurality of second mechanical fasteners (S50);

[0045] Each shear plate (S10) has a first type of assembly hole at both ends, and each shear plate (S10) has a plurality of second type of assembly holes on the plate body and each reinforcing sheet (S30) has a plurality of second type of assembly holes on the sheet body, respectively;

[0046] The plurality of shear plates (S10) are arranged in pairs to obtain a plurality of shear plate pairs, and the pairs of shear plates are assembled by closing the first type of assembly hole, and the mold set is obtained by fastening connection through the first mechanical fasteners (S40);

[0047] ​The plurality of reinforcing sheets (S30) are combined two by two, and are used to be pasted to each non-impact damage area of the test piece to be tested, to nest the test piece to be tested with the mold set through the second type of assembly holes on the reinforcing sheets (S30), and to be fastened and connected to the mold set by the second type of mechanical fasteners (S50); each non-impact damage area has a plurality of second type of assembly holes matched with the sheet body of the reinforcing sheet (S30);

[0048] Each clamping block (S20) is fastened and connected to the mold set by the first type of mechanical fasteners (S40) at one end, and is configured to be connected to the testing machine at the other end, to conduct the tensile load applied by the testing machine to the impact damage area surrounded by each non-impact damage area on the test piece to be tested, for shear strength testing.

[0049] In the embodiment of the present application, the shear plate is a main component of the test fixture, has a specific shape and structure, has the first type of assembly holes at two ends, and has the second type of assembly holes on the plate body. The plurality of shear plates are arranged opposite to each other and are closed and assembled through the first type of assembly holes, and are fastened and connected by the first type of mechanical fasteners to form the mold set, to provide a basic structure for mounting and positioning the test piece, and to help the load to be reasonably transmitted to the test piece in cooperation with other components during testing. The clamping block is a component for connecting the testing machine and the mold set, is fastened and connected to the mold set by the first type of mechanical fasteners at one end, and is connected to the testing machine at the other end, and mainly functions to stably conduct the tensile load applied by the testing machine to the mold set, and then to the test piece, so that the test piece is subjected to a specific load to perform shear strength testing. The reinforcing sheet is a sheet-shaped component pasted on the non-impact damage area of the test piece, has holes matched with the second type of assembly holes on the plate body of the shear plate on the sheet body, is made of glass fiber epoxy resin laminate, is pasted on the non-impact damage area of the test piece by two by two combination, is used to enhance the strength of the non-impact damage area, prevents the non-impact damage area from being damaged too early due to the load during testing, ensures that the test piece can withstand sufficient load, and enables the load to be more concentrated on the impact damage area, so that the shear strength of the impact damage area can be more accurately tested. Meanwhile, the test piece is connected to the mold set through the second type of assembly holes on the reinforcing sheet and the mold set.

[0050] The first type of mechanical fastener is used to connect the fastening elements of different components, mainly used to connect the shear plates together to form a mold set, and to fasten the clamping block with the mold set, ensuring that the connection between the components is firm and reliable, and can withstand the tensile load applied by the testing machine, ensuring the stability of the fixture structure during testing. The second type of mechanical fastener is also a fastening element for connection, used to fasten the test piece with the second type of assembly hole on the reinforcing sheet to the mold set, so that the test piece can be securely installed in the mold set and accurately withstand and transmit the load during testing, ensuring the accuracy and reliability of the test.

[0051] Specifically, the mold set assembled by the shear plates is the core support structure of the entire fixture system. The clamping block is tightly connected to the mold set at one end, and this connection is based on the first type of mechanical fastener, forming a stable mechanical transmission path. When the testing machine starts to apply a tensile load, the clamping block accurately and stably transmits the force from the testing machine to the mold set, and the mold set, with its rigid structure built by multiple shear plates, evenly disperses the load, preparing for subsequent transmission to the test piece. Without the solid foundation of shear plates, the load transmitted by the clamping block cannot be effectively received and distributed; on the contrary, without the conduction of the clamping block, the mold set composed of shear plates cannot obtain the power source, and the two are interdependent, opening the first step of load transmission.

[0052] For ease of understanding, Figure 2 For the inside of the mold set, a set of shear plates and the planar structure between the reinforcing sheets are shown in the exploded view. S60 is the first type of assembly hole, and S70 is the second type of assembly hole. The second type of assembly hole of the shear plate body and the corresponding assembly hole of the reinforcing sheet body are the key interfaces for close cooperation. In the formal experiment, there is a test piece between the two reinforcing sheets S30, but it is not shown in Figure 2 , Figure 2 Only the internal synthetic structure of the mold set is shown. After multiple shear plates are arranged in a specific layout, the reinforcing sheets are combined two by two and accurately attached to the non-impact damage area of the test piece according to these assembly holes, achieving perfect nesting with the shear plates. On the one hand, the shear plates provide a framework for the reinforcing sheets, ensuring that the reinforcing sheets can be accurately positioned and stably attached to the test piece; on the other hand, the reinforcing sheets fill the structural "gap" between the test piece and the shear plates, strengthening the mechanical properties of the test piece in the non-impact damage area, making the overall structure of the test piece more stable and better able to adapt to the subsequent loading process.

[0053] The reinforcing piece and the test piece are in a close relationship of reinforcement and being reinforced. The reinforcing piece is closely attached to each non-impact damage area of the test piece through the carefully designed two-by-two combination mode, and is firmly attached by secondary gluing. This attachment not only enhances the carrying capacity of the local area of the test piece, prevents premature damage caused by load concentration in the non-impact damage area, and interferes with the shear strength test results, but also establishes a connection with the shear plate and the mold set through the second type of assembly hole, so that the test piece can be deeply integrated into the entire fixture system. Once the test piece is not firmly bound with the reinforcing piece, the test piece may be separated from the restraint of the fixture system during the loading process, resulting in test failure; on the contrary, if the test piece is not reinforced by the reinforcing piece, the structural weakness of the test piece will be exposed, and the test piece cannot bear the required load.

[0054] The first type of mechanical fastener plays a key role in the connection process of the shear plate assembled into the mold set and the clamping block with the mold set. They tightly lock each shear plate to ensure that the mold set has sufficient rigidity and stability to withstand and conduct high-strength tensile load; at the same time, they firmly fix the clamping block on the mold set to ensure the continuity of load transmission. If the first type of mechanical fastener is loose or missing, the shear plate will be scattered, the clamping block will be separated, and the entire fixture system will be paralyzed.

[0055] The second type of mechanical fastener focuses on stably embedding the test piece with the reinforcing piece into the mold set, accurately locking the position of the test piece according to the design of the assembly hole of the reinforcing piece and the shear plate, so that the test piece does not displace or separate during the loading process. Once the second type of mechanical fastener fails, the test piece will be randomly displaced under the action of the load, and the accuracy and order of the test cannot be guaranteed.

[0056] Optionally, the first type of mechanical fastener is a pin (S40), and the second type of mechanical fastener (S50) is a connecting bolt.

[0057] The pin is a cylindrical mechanical part, usually used for positioning and connecting two or more components, and plays a role in fixing and transmitting load. In the test fixture of the embodiment of the application, it is used as the first type of mechanical fastener. After the plurality of shear plates are arranged opposite to each other, they are closed and assembled according to the first type of assembly hole to form a mold set, and the pin is inserted into the first type of assembly hole at both ends of the shear plate to fix the relative position between the shear plates, so that the mold set becomes a stable whole structure.

[0058] A connecting bolt is a common mechanical connector, typically consisting of a screw and a nut. Tightening the nut creates a preload, thereby connecting two or more components. In the test fixture of an embodiment of the present invention, the connecting bolts are used to nest and assemble the test piece, which has a reinforcement sheet attached to it, with the mold kit via the second type of assembly holes on the reinforcement sheet, and then securely connect it to the mold kit. This ensures that the test piece and the mold kit are tightly coupled, allowing the tensile load applied by the testing machine to be accurately transmitted to the test piece during testing.

[0059] Furthermore, the two clamping blocks (S20) may include a first U-shaped clamping block and a second U-shaped clamping block, wherein:

[0060] The connecting ears of the first U-shaped clamping block and the second U-shaped clamping block are fastened to the mold kit via a first type of mechanical fastener (S40); the clamping arms of the first U-shaped clamping block and the second U-shaped clamping block are configured to be connected to a testing machine.

[0061] like Figure 3 As shown, in the side view of the test fixture S1, the first U-shaped clamping block (S21) and the second U-shaped clamping block (S22) are two U-shaped clamping components, which are key components in the test fixture for connecting the testing machine and the mold kit. Each U-shaped clamping block has a two-part structure of a clamping arm and a connecting ear. Among them, the connecting ears of the first U-shaped clamping block and the second U-shaped clamping block are fastened to the mold kit via a first-class mechanical fastener (pin), and their function is to firmly clamp the mold kit and provide a stable connection basis for subsequent load transfer. The clamping arms of the first U-shaped clamping block and the second U-shaped clamping block are configured to be connected to the testing machine, and their function is to introduce the tensile load applied by the testing machine into the entire test fixture system, which is the input end of the load. Through the connection between the connecting ears and the testing machine, the tensile force of the testing machine can be transmitted to the clamping block, and then further transmitted to the mold kit and the test piece to be tested.

[0062] Optionally, the first U-shaped clamping block (S21) and the second U-shaped clamping block (S22) adopt a universal joint structure with adjustable angle to adapt to test pieces of different thicknesses.

[0063] The universal joint is a kind of mechanical structure that can rotate flexibly within a certain angle range, in the test fixture of the embodiment of the present application, the first U-shaped clamping block and the second U-shaped clamping block adopt the adjustable angle universal joint structure, which is used to adapt to different thicknesses of the test pieces to be tested. Since different test pieces to be tested may have different thicknesses, the use of the adjustable angle universal joint structure can enable the first U-shaped clamping block and the second U-shaped clamping block to be adjusted in angle when connecting the testing machine and the mold sleeve according to the actual thickness of the test piece, so as to ensure that the test piece can be correctly installed in the fixture, and to ensure that the tensile load applied by the testing machine can be uniformly and accurately transmitted to the test piece, thereby improving the accuracy and reliability of the test.

[0064] In the embodiment of the present application, the working process of the whole test fixture system is the result of the cooperation of various components, specifically, the components such as the shear plate and the clamping block are made of stainless steel material and can be reused, which reduces the high cost caused by frequent replacement of the fixture, and this durable design greatly prolongs the service life of the fixture and reduces the long-term investment cost; through the ingenious design of the shear plate, the reinforcing sheet, the mechanical fastener and the clamping block with the adjustable angle universal joint structure, the assembly process of the test piece and the fixture becomes simple and fast. The components are closely matched and the connection mode is intuitive, so that the operator can quickly complete the installation and debugging, and further improve the test frequency per unit time; whether it is for a composite laminate or other materials with similar shear strength test requirements, the fixture design can provide reliable test support with its good universal structure and connection mode, and adapt to the diversified test scenarios in material science research and engineering application.

[0065] Embodiment two

[0066] Figure 4 A connection relationship diagram of a shear strength test system provided by the second embodiment of the present application is shown in Figure 4 As shown, the system comprises: a test fixture (S1) for testing the shear strength of a test piece, a test piece to be tested (S2), and a testing machine (S3);

[0067] The test piece to be tested (S2) is used to be fastened and connected into a mold sleeve obtained by fastening a plurality of shear plates (S10) via a plurality of reinforcing sheets pasted on the front and back surfaces of each non-impact damage area;

[0068] The testing machine (S3) is used to test the shear strength of the impact damage area surrounded by each non-impact damage area on the test piece to be tested by applying a tensile load after establishing a connection relationship with the mold sleeve via two clamping blocks (S21), (S22).

[0069] In the embodiments of the present application, a complete shear strength test system is described, covering three key components: a test fixture for fixing and loading the test piece (including a mold kit and a reinforcing sheet), a test piece to be tested as the test object, and a testing machine for providing power loading, which work together to accurately measure the shear strength of the test piece. As shown in Figure 4 The arrow indicates the flow direction of the data. The test piece to be tested (S2) refers to the object of the test, which has an impact damage area on its surface. The maximum shear strength that the impact damage point in the impact damage area can withstand needs to be measured. The test piece is tightly connected to the reinforcing sheet and the mold kit, so that the tensile load applied by the testing machine (S3) can accurately act on the impact damage point of the impact damage area. The impact damage point is generally the center position of the impact damage area. During the test, the deformation and failure of the test piece will reflect the shear strength characteristics of the impact damage point. The testing machine is a universal testing machine, which is the power source of the entire test system. By establishing a connection relationship with the two clamping blocks, the testing machine applies a tensile load to the mold kit. The testing machine can accurately control the size and loading speed of the tensile load to simulate different actual working conditions.

[0070] Optionally, the test piece to be tested is a pre-cut cross-like truncated rectangle, which includes four rectangular non-impact damage areas and one rectangular impact damage area. Each non-impact damage area surrounds the impact damage area in four directions. The gap between each pair of non-impact damage areas is used to accommodate the first type of mechanical fastener.

[0071] Correspondingly, the number of shear plates and reinforcing sheets is eight; the number of first type of mechanical fasteners is four.

[0072] The cross-like truncated rectangle is a square with corner cutting processing at four corner point regions. The remaining part presents a cross-like shape as a whole, as shown in Figure 5 , which is a schematic view of the plane of the test piece to be tested. The impact damage area is located at the center position of the cross-like truncated rectangle and is a rectangular area. The impact damage point in this area is the focus of the entire test. It simulates the part that may be impacted in actual use. By testing the shear strength of the impact damage point in this area, the mechanical property change of the material after being impacted can be understood, which provides an important basis for evaluating the impact resistance of the material and the safety of the structure.

[0073] The non-impact damage area is composed of four rectangles, which are located in the four directions of the impact damage area, surrounding the impact damage area in the middle. The main role of the non-impact damage area is to provide support and constraint for the impact damage area. During the test, by pasting the reinforcing sheet and connecting with the shear plate, the non-impact damage area can bear part of the tensile load, so as to ensure that the tensile load can be uniformly transmitted to the impact damage area, avoiding uneven deformation or premature damage of the impact damage area due to local excessive stress. At the same time, the non-impact damage area can also be used as a reference area during the test, and compared with the performance of the impact damage area for analysis.

[0074] There are gap areas between each two non-impact damage areas, which have specific functions for accommodating the first type of mechanical fasteners, which connect the shear plate and the reinforcing sheet together, and then fasten the test specimen to be tested in the mold kit. The design of the gap area not only realizes the reliable connection between the test specimen and the clamp, but also ensures the compactness and stability of the connection, so that when the tensile load is applied, the force can be transmitted to the center position of the impact damage area along the predetermined path, ensuring the accuracy and reliability of the test results.

[0075] Further, the testing machine (S3) is a universal testing machine;

[0076] The connecting ears of the first U-shaped clamping block (S21) and the second U-shaped clamping block (S22) are fastened to the mold kit through two first type of mechanical fasteners (S40) arranged at intervals;

[0077] The clamping arm of the first U-shaped clamping block (S21) is configured to be connected with the crossbeam of the testing machine (S3), and the clamping arm of the second U-shaped clamping block (S22) is configured to be connected with the base of the testing machine (S3);

[0078] The testing machine (S3) is particularly used for testing the shear strength of the impact damage area of the test specimen (S2) nested in the mold kit by diagonally stretching the test specimen (S2) in the axial direction.

[0079] In the embodiment of the present application, a universal testing machine is selected as the power source of the test system, which has strong adaptability. The universal testing machine can accurately control multiple parameters such as loading force, displacement, and speed, meeting the needs of accurate testing of test specimens under different materials and different working conditions. Compared with some special but single-function testing machines, it can flexibly cope with various test scenarios, whether it is a regular shape or a specially designed test specimen such as a cross-shaped truncated rectangular test specimen, and can achieve accurate shear strength determination on its platform. The connection mode of the connecting ears of the first and second U-shaped clamping blocks and the mold kit is very critical, and the two first type mechanical fasteners (such as pins) arranged at intervals ensure the stability and reliability of the connection. This double-point connection mode can effectively disperse the load and avoid the loosening of the clamping block or the displacement deviation during the loading process due to uneven stress of single-point connection, thereby ensuring stable and smooth force transmission from the testing machine to the mold kit, laying a foundation for subsequent accurate testing of the shear strength of the impact damage area.

[0080] As shown in Figure 6 , the clamping arms of the first U-shaped clamping block (S21) are connected to the crossbeam of the testing machine, and the clamping arms of the second U-shaped clamping block (S22) are connected to the base of the testing machine, which configures a complete mechanical conduction closed loop. The crossbeam, as the main component of the testing machine for applying tension, transmits the force to the mold kit through the first U-shaped clamping block; and the base, as the support foundation of the entire system, plays a reverse restraining and stabilizing role on the mold kit through the second U-shaped clamping block. The two work together to make the mold kit maintain a stable mechanical balance state when subjected to axial tensile load, ensuring uniform stress on the test specimen and preventing adverse stress conditions such as tilting and twisting.

[0081] The testing machine specifically adopts a diagonal tensile method to test the shear strength of the impact damage area of the test specimen nested in the mold kit. When the axial tensile load is applied, due to the special connection layout of the first and second U-shaped clamping blocks and the cross-shaped truncated rectangular structure of the test specimen, the force will be conducted along a specific path inside the test specimen, and finally act on the center position of the non-impact damage area (the intersection position of the dashed lines in Figure 6 ). This conduction method makes the impact damage area subjected to a diagonal tensile component, thereby generating shear stress, simulating the shear working conditions that the impact damage area may encounter in the actual complex stress environment, and enabling more accurate acquisition of the real shear strength data of the area, providing a strong basis for material performance evaluation and engineering application.

[0082] Optionally, the system further comprises a computing control unit (S4);

[0083] The calculation control unit (S4) is connected with the testing machine (S3) to read the real-time tensile load of the testing machine (S3), determine the moment when the impact damage area is destroyed according to the real-time tensile load, take the current tensile load of the testing machine at the moment as the maximum tensile load, and calculate the ultimate shear strength.

[0084] As shown in the figure, the calculation control unit is electrically connected with the testing machine, and the connection enables data interaction between the two, so that the testing machine can transmit various parameters in the loading process to the calculation control unit in real time, providing a basis for subsequent accurate control and data analysis. Figure 4

[0085] During the shear strength test process, the calculation control unit can obtain the latest tensile load in real time at each loading moment and immediately analyze and process it, and according to the change trend of the tensile load, the test trend can be predicted in advance, and if necessary, the loading strategy of the testing machine can be dynamically adjusted to avoid affecting the accuracy of the test results due to too fast or too slow loading. Since the stress condition of the impact damage area can intuitively reflect the development of internal stress and strain when the impact damage area bears shear force, a sudden decrease in tensile load often indicates that the material is about to be or has been damaged. By continuously monitoring and sending the tensile load output by the testing machine to the calculation control unit in real time, the calculation control unit provides key first-hand data for the system to judge the test process and results.

[0086] The calculation control unit accurately determines the moment when the impact damage area is destroyed according to the real-time tensile load data transmitted by the testing machine. At the moment when the damage moment is captured, the tensile load applied by the testing machine at this time is taken as the ultimate force borne by the impact damage area. Finally, the ultimate shear strength is accurately calculated using the target tensile load by using the pre-set calculation formula and material parameters, completing the whole process from raw data collection to final key indicator output, and providing highly reliable data support for material performance evaluation.

[0087] Further, the calculation control unit is also used to judge whether the change rate of the tensile load applied by the testing machine at the current moment exceeds the specified multiple of the set threshold value under the constant loading rate of the testing machine.

[0088] If yes, the current moment is determined as the moment when the impact damage area is destroyed.

[0089] ​The calculation control unit takes the constant loading rate of the testing machine as an important reference. During the entire shear strength test, the loading rate remains stable, which creates a quantifiable and comparable environment for subsequent accurate determination of the damage time of the impact damage area. Because the internal structure changes, displacement response, and loading rate are closely related when the material is subjected to a stable increasing external force, a stable loading rate makes the displacement change trend more regular, facilitating accurate capture of key nodes. The impact damage point, as the key representative point of stress and deformation of the impact damage area, can directly reflect the cumulative rate of internal damage of the material. When the material is close to failure, internal micro-cracks rapidly expand and structural instability intensifies, which will directly affect the force. By continuously comparing the change of each instantaneous force, the calculation control unit can accurately capture the qualitative change moment of the material mechanics state.

[0090] A specified multiple of the set threshold value is introduced as the critical point for damage determination. The threshold value is based on the experience value obtained from previous research and data analysis of a large number of similar materials and similar test conditions, taking into account the material's elastic modulus, Poisson's ratio, expected strength, and other inherent properties, as well as the test accuracy requirements, environmental factors, etc. Once the change rate (decrease) of the tensile load exceeds the specified multiple of the threshold value, it means that the material has exceeded the normal elastic deformation range and entered the accelerated failure stage. At this time, the calculation control unit decisively determines the current time as the damage time of the impact damage area. This accurate and scientific determination method provides a reliable time node reference for subsequent ultimate shear strength calculation.

[0091] Optionally, the calculation control unit further comprises a shear strength calculation formula for solving the shear strength of the test piece:

[0092]

[0093] where τ SAI is the ultimate shear strength to be solved, with a unit of MPa; P max is the target tensile load, with a unit of N; A is the cross-sectional area of the impact damage area, which is the product of the width of the impact damage area and the thickness of the test piece, with a unit of mm 2 .

[0094] In addition to the function of determining the damage time of the impact damage area, the calculation control unit also has the key ability to solve the shear strength of the test piece. By providing an accurate quantitative method for the ultimate shear strength of the test piece, the calculation control unit's role in the entire shear strength test system is perfected, from data acquisition, processing to the final calculation of key indicators, forming a complete functional closed loop. Specifically, P maxis the tensile load applied by the testing machine at the moment when the impact damage area is destroyed, which represents the maximum external force that the material can withstand at the moment of destruction, and is an important input parameter for measuring the strength of the material. A is the cross-sectional area of the impact damage area, which is obtained by multiplying the width of the impact damage area by the thickness of the test piece, and reflects the effective load-bearing area of the material under stress, and the size of the area directly affects the stress per unit area. As shown in Figure 7 b is the width of the non-impact damage area, a is the original width of the test piece before cutting, and a and b are known quantities before the experiment, so c = a-2b is the width of the impact damage area, and the thickness (d) of the test piece is known, so A = (a-2b) x d.

[0095] Under the diagonal tensile loading mode adopted by the test system, through the derivation of mechanical principles and geometric relationships, This coefficient can reasonably convert the applied tensile load into a calculation related to the shear strength of the impact damage point, so that the formula can accurately reflect the ultimate shear strength of the impact damage area of the test piece under this specific loading mode.

[0096] In the embodiment of the application, the real-time feedback mechanism of the test process is realized by the cooperative work of the calculation control unit and the testing machine, and this real-time intelligent decision-making capability greatly improves the reliability and scientificity of the test, and the entire test system builds an automatic test process closed loop through the two components. Through the construction of a real-time data transmission loop, the load information is transmitted to the calculation control unit in seconds, and the ultimate shear strength calculation is automatically completed immediately, saving the time-consuming of manual calculation and data processing, and at the same time, the displacement speed can be intelligently predicted to break down, and the test can be adjusted if necessary, greatly improving the test efficiency and realizing intelligent operation.

[0097] It should be understood that the various forms of the flow shown above can be reordered, added or deleted steps. For example, the steps described in the present application can be executed in parallel, in sequence or in different order, as long as the desired results of the technical solutions of the present application can be achieved, and the present application does not limit herein.

[0098] The above specific embodiments do not constitute a limitation on the scope of protection of the present application. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A test fixture for performing shear strength testing on a test piece, characterized in that: include: A plurality of shear plates, two clamping blocks, a plurality of reinforcing plates, a plurality of first-type mechanical fasteners, and a plurality of second-type mechanical fasteners; each shear plate has first-type assembly holes at both ends, and each shear plate and each reinforcing plate have a plurality of second-type assembly holes on the body; The plurality of shear plates are arranged opposite to each other in pairs to obtain a plurality of shear plate pairs. After the shear plate pairs are closed and assembled according to the first type assembly holes, they are fastened and connected by the first type mechanical fasteners to obtain a mold kit. Multiple reinforcement sheets are combined in pairs and are used to be attached to the non-impact damaged areas of the test piece on the front and back sides, so that the test piece can be nested and assembled with the mold kit through the second-type assembly holes on the reinforcement sheets and fastened to the mold kit through the second-type mechanical fasteners; each non-impact damaged area has multiple second-type assembly holes that are compatible with the sheet body of the reinforcement sheet; One end of each clamping block is fastened to the mold kit via a first-class mechanical fastener, and the other end is configured to be connected to the testing machine, so as to transmit the tensile load applied by the testing machine to the impact damaged area surrounded by the non-impact damaged areas on the test piece to perform a shear strength test.

2. The test fixture according to claim 1, characterized in that The first type of mechanical fasteners are pins, and the second type of mechanical fasteners are connecting bolts.

3. The test fixture according to claim 1, characterized in that The two clamping blocks include a first U-shaped clamping block and a second U-shaped clamping block, wherein: The connecting ears of the first U-shaped clamping block and the second U-shaped clamping block are fastened to the mold kit via a first type of mechanical fastener; and the clamping arms of the first U-shaped clamping block and the second U-shaped clamping block are configured to be connected to a testing machine.

4. The test fixture according to claim 3, characterized in that The first U-shaped clamping block and the second U-shaped clamping block adopt a universal joint structure with adjustable angle, so as to adapt to test pieces of different thicknesses.

5. A shear strength testing system, characterized in that: include: A test fixture for performing a shear strength test on a test piece, a test piece to be tested, and a testing machine as described in any one of claims 1 to 4; The test piece is used to be fastened to a mold set formed by fastening multiple shear plates via multiple reinforcement sheets attached to each non-impact damaged area on the front and back sides; The testing machine is used to perform a shear strength test on an impact damaged area surrounded by non-impact damaged areas on a test piece by applying a tensile load after establishing a connection relationship with the mold kit via two clamping blocks.

6. The system according to claim 5, characterized in that The test piece is a pre-cut, truncated cross-shaped rectangle, which includes four rectangular non-impact damaged areas and one rectangular impact damaged area. The non-impact damaged areas surround the impact damaged area in four directions. The gaps between the non-impact damaged areas are used to accommodate the first type of mechanical fasteners. Correspondingly, the number of the shear plates and the number of the reinforcement plates are both eight; and the number of the first-type mechanical fasteners is four.

7. The system according to claim 5, characterized in that The testing machine is a universal testing machine; The clamping arms of the first U-shaped clamping block and the second U-shaped clamping block are fastened to the mold kit via two first-type mechanical fasteners arranged at intervals; The clamping arm of the first U-shaped clamping block is configured to be connected to a crossbeam of the testing machine, and the clamping arm of the second U-shaped clamping block is configured to be connected to a base of the testing machine; The testing machine is specifically used to perform shear strength testing on the impact damaged area of ​​the test piece to be tested nested in the mold kit by applying a tensile load in the axial direction and adopting a diagonal stretching method.

8. The system according to claim 5, wherein: Also includes: Computing control unit; Among them, the calculation control unit is electrically connected to the testing machine, and is used to read the real-time tensile load of the testing machine, determine the moment when the impact damage area is destroyed based on the real-time tensile load, and use the current tensile load of the testing machine at the moment of destruction as the maximum tensile load to calculate the ultimate shear strength.

9. The system according to claim 8, characterized in that The calculation control unit is further configured to determine in real time whether the rate of change of the tensile load applied by the testing machine at the current moment exceeds a specified multiple of a set threshold value under a constant loading rate of the testing machine; If so, the current moment is determined to be the moment when the impact damage area is destroyed.

10. The system according to claim 8, wherein: The calculation control unit further includes: a shear strength calculation formula for solving the shear strength of the test piece: Among them, τ SAI is the ultimate shear strength to be solved, in MPa; P max is the target tensile load, in N; A is the cross-sectional area of ​​the impact damage area, which is the product of the width of the impact damage area and the thickness of the test piece, in mm 2 .

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