A universal testing machine is provided with a detection tool for clamping and testing epoxy resin samples of various specifications

Abstract

The present application belongs to the technical field of material mechanical property testing, in particular to a universal testing machine adaptive epoxy resin multi-specification sample clamping detection tool, which comprises a testing machine main body, a fixed integrated plate fixedly connected to the upper surface of the testing machine main body, a moving integrated plate slidingly connected to the outer surface of the guiding component of the testing machine main body, and a tool assembly arranged on the opposite side surface of the fixed integrated plate and the moving integrated plate. Each tool assembly comprises, from top to bottom, a standard connecting joint, a floating self-centering mechanism, a synchronous bidirectional clamping mechanism, and a replaceable composite jaw module. The universal testing machine adaptive epoxy resin multi-specification sample clamping detection tool sets a floating self-centering mechanism, adopts cross staggered guide grooves and four sets of floating blocks to cooperate, and is arranged in layers and orthogonally with an axial linear slide rail and a radial linear slide rail, realizes two-dimensional floating adjustment motion decoupling in the horizontal plane, and can provide sufficient rigid holding force through the disc spring set after centering.

Description

Technical Field

[0001] This invention relates to the field of material mechanical property testing technology, and in particular to a universal testing machine-compatible fixture for holding and testing epoxy resin samples of various specifications. Background Technology

[0002] Epoxy resin, as an important thermosetting polymer material, is widely used in key areas such as electrical insulation, composite matrix, adhesives, and structural repair due to its excellent insulation, adhesion, and mechanical properties. In its research and application, accurate testing of mechanical properties such as tensile strength, flexural properties, and compressive strength is a core aspect of ensuring product quality and engineering safety, and the universal testing machine is the fundamental equipment for performing these tests. Currently, when testing epoxy resin samples using a universal testing machine, clamping and fixing mainly rely on the machine's built-in universal fixtures. However, these fixtures were initially designed primarily for ductile materials such as metals and were not specifically optimized for the brittle characteristics of epoxy resin. This has led to a series of compatibility issues that have long plagued testing personnel.

[0003] Epoxy resin materials are inherently brittle, have low elongation, high surface hardness, and limited compressive strength. These characteristics present a significant contradiction with the rigid clamping method of existing general-purpose fixtures. On the one hand, the surface of epoxy samples is usually quite smooth, and the clamping surface of general-purpose fixtures cannot provide sufficient friction. Under tensile loads, the sample is prone to slipping out of the fixture, leading not only to distorted data such as overestimation of elongation and underestimation of strength, but also the potential for safety accidents due to sudden slippage. On the other hand, traditional fixtures often require a large clamping force to prevent slippage, but the concentrated stress generated by the rigid metal jaws can easily form stress peaks in the sample clamping section. For brittle epoxy resin, which is extremely sensitive to stress concentration, this often leads to crushing or premature fracture of the sample at the clamping point, rendering the test completely unusable. In addition, the alignment of the upper and lower clamps of existing universal testing machines mainly relies on the machining accuracy of the equipment itself, and generally lacks the ability to actively compensate for alignment. If there is a deviation between the center and the loading axis when the sample is clamped, an eccentric additional bending moment will be generated during the tensile process. For small-sized or thin epoxy samples, this additional bending moment will significantly interfere with the accuracy of the measurement results, and may even lead to abnormal fracture of the sample.

[0004] Meanwhile, epoxy resin samples come in various shapes, including conventional castings, ultra-thin films, and high-load samples. These different shapes require different clamping force distribution characteristics, contact surface friction coefficients, and jaw opening ranges. Existing general-purpose clamps cannot simultaneously meet these diverse needs. Frequent clamp changes are not only cumbersome and time-consuming, but also make it difficult to guarantee the repeatability of alignment and the comparability of test data after replacement. Therefore, there is an urgent need to develop a specialized clamping and testing fixture that can adapt to various epoxy resin sample sizes, has self-aligning capabilities, and effectively avoids slippage and cracking, in order to systematically solve the technical problems existing in the current technology. Summary of the Invention

[0005] Based on the aforementioned technical problems, this invention proposes a universal testing machine-compatible fixture for holding and testing epoxy resin samples of various specifications.

[0006] This invention proposes a universal testing machine-compatible fixture for clamping and testing epoxy resin samples of various specifications. The fixture includes a testing machine body, a fixed integrated plate fixedly connected to the upper surface of the testing machine body, a movable integrated plate slidably connected to the outer surface of the guide component of the testing machine body, and fixture assemblies arranged on the opposite side surfaces of the fixed integrated plate and the movable integrated plate. Each fixture assembly includes, from top to bottom, a standard connecting joint, a floating self-centering mechanism, a synchronous bidirectional clamping mechanism, and a replaceable composite jaw module.

[0007] The standard connector is used for quick docking and positioning with the loading end of the universal testing machine.

[0008] The lower surface of the floating self-aligning mechanism is rigidly fixed to the standard connecting joint, and the synchronous bidirectional clamping mechanism is connected above the floating self-aligning mechanism to realize adaptive micro-alignment compensation on the horizontal plane.

[0009] The synchronous bidirectional clamping mechanism adopts a bidirectional synchronous adjustment structure to achieve continuous adjustment of the jaw opening.

[0010] The composite jaw module can be detachably installed at the end of the synchronous bidirectional clamping mechanism, and is suitable for epoxy resin samples of various specifications. A flexible anti-slip buffer pad can be detachably installed on the inner side of the composite jaw module.

[0011] Preferably, the floating self-aligning mechanism includes a fixed floating base fixedly connected to the upper surface of the standard connecting joint, and a cross-shaped guide groove is provided on the upper surface of the fixed floating base. Floating sliders are slidably engaged on the inner surfaces of the four support grooves of the guide groove.

[0012] In order to ensure that the floating slider obtains accurate and independent sliding guidance in mutually perpendicular directions and to provide a stable motion basis for subsequent multi-dimensional centering adjustment, the floating slider with cross-shaped guide grooves and sliding engagement in its four support grooves is set up so that the rotational motion of the driving component can be converted into linear displacement, thereby effectively eliminating the additional eccentric load introduced by the initial deviation of the sample clamping.

[0013] Preferably, the floating self-aligning mechanism further includes a linkage housing fixedly connected to the bottom wall of the guide groove. An axial linear slide rail arranged in parallel is fixedly connected to the upper surface of the linkage housing. An axial slider is slidably engaged on the outer surface of the axial linear slide rail. A radial linear slide rail arranged in parallel is fixedly connected to the upper surface of the axial slider. A radial slider is fixedly connected to the outer surface of the radial linear slide rail. A T-shaped floating platform is fixedly connected to the upper surface of the radial slider.

[0014] In order to achieve decoupled motion of two-dimensional floating adjustment in the horizontal plane and ensure that the upper clamping mechanism has good installation rigidity and micro-displacement compensation capability in any direction in the plane, the axial linear slide rail and the radial linear slide rail are arranged in layers orthogonally. The axial slider drives the radial linear slide rail to move axially, and the radial slider moves relatively radially. The two movements do not interfere with each other. The T-shaped floating platform, as the final bearing base, works together to complete adaptive centering and avoids the sample from bending or breaking due to rigid tension.

[0015] Preferably, the floating self-centering mechanism further includes an L-shaped push block fixedly connected to the surface of the floating slider near the floating platform. The upper surface of the push block is fixedly connected to guide blocks distributed inward and outward. Disc springs are fixedly connected to the opposite side surfaces of the two guide blocks. The lower surface of the floating platform is provided with an annular mountain-shaped push-pull groove. The free ends of the two disc springs are fixedly connected to the two side surfaces of the middle plate of the push-pull groove, respectively.

[0016] Through the above technical solution, in order to enable the floating platform to automatically and slightly adjust with the center of the sample in the horizontal plane, and to maintain sufficient rigidity and stability after centering, the linear displacement of the floating slider is converted into pushing and pulling of the guide block by the L-shaped push block. The guide blocks on both sides clamp the disc spring to form an elastic energy storage structure. The free end of the disc spring is fixedly connected to the middle plate of the mountain-shaped push-pull groove on the lower surface of the floating platform. The compression and rebound of the disc spring generate an adaptive balance force, which takes into account the dual requirements of compliant centering and stable clamping.

[0017] Preferably, the floating self-centering mechanism further includes rotating grooves arranged in a ring array inside the fixed floating base. The upper end of the rotating groove is fixedly connected to the lower end of the corresponding guide groove. A floating screw is rotatably connected inside the rotating groove through a bearing. Two opposing floating screws are arranged in a bidirectional manner and rotate synchronously. A linkage tube block is threaded onto the outer surface of the floating screw. The upper surface of the linkage tube block is fixedly connected to the lower surface of the floating slider.

[0018] In order to achieve active, symmetrical and uniform drive adjustment of the floating slider and improve transmission efficiency and service life through the above technical solution, rotating slots distributed in a ring array and floating screws connected by bearings are set up. The two floating screws adopt bidirectional threads and rotate synchronously. The screw rotation is converted into the opposite or opposite linear motion of the floating slider by the linkage block of the threaded sleeve, ensuring that the centering adjustment in any direction has good symmetry and uniformity, and avoiding secondary eccentricity caused by unilateral adjustment.

[0019] Preferably, a connecting rod is fixedly connected to one side surface of the two radially floating screws. The connecting rod is rotatably connected to the surface of the linkage housing via a bearing. A driven bevel gear is rotatably connected to the inner surface of the opposite axial side of the linkage housing via a bearing. A driving bevel gear is rotatably connected to the inner top wall of the linkage housing via a bearing. The two driven bevel gears mesh with the driving bevel gear respectively. A reduction motor is fixedly connected to the adjacent side surface of the fixed floating base. The output shafts of the two reduction motors are fixedly connected to the side surface of the corresponding floating screw respectively.

[0020] In order to achieve the linkage and synchronous control of the floating sliders in four directions and ensure the consistency of motion of the floating platform when it translates in any direction in the horizontal plane, the floating screw in the radial direction is directly driven by the geared motor, and the coaxial power is transmitted through the connecting rod. In the axial direction, the active bevel gear meshes with two driven bevel gears and transmits the power to the two axially opposite floating screws through the connecting rod, forming a compact and precise bevel gear transmission structure. The geared motor provides sufficient driving torque, which is convenient for automated centering control.

[0021] Preferably, the synchronous bidirectional clamping mechanism includes a clamping guide rail fixedly connected to the upper surface of the floating platform, and clamping sliders that are relatively distributed are slidably engaged on the outer surface of the clamping guide rail. A zero-point quick-change component is fixedly connected to the upper surface of the clamping sliders, and a clamping panel is fixedly connected to the surface of the central pull rod of the zero-point quick-change component.

[0022] Through the above technical solution, the zero-point quick-change component includes an integrated rigid base body. The base body integrates a hydraulic oil circuit and is provided with an external hydraulic oil port and a hydraulic drive plunger. A locking actuator and an elastic preload reset assembly are assembled in the hollow cavity inside the base. The locking actuator includes a transversely arranged central tie rod, symmetrically arranged wedge-shaped locking claws, and support rollers on the back of the locking claws. The elastic preload reset assembly consists of multiple symmetrically stacked disc springs. One end of the disc spring assembly abuts against the inner wall of the base, and the other end presses against the wedge-shaped locking claws through the support rollers. A positioning stop is provided at the bottom of the base for unified reference positioning. Under normal conditions, the preload force output by the disc spring assembly is squeezed by the support rollers against the wedge-shaped locking claws, and the wedge surface of the central tie rod achieves mechanical self-locking clamping of the workpiece stud. Hydraulic oil is introduced into the oil circuit to push the hydraulic drive plunger to push the central pull rod axially, thereby releasing the radial compression of the wedge surface on the locking claw and compressing the disc spring assembly to open the locking claw and release the workpiece. After hydraulic pressure is released, the disc spring assembly rebounds, which can drive the locking claw to close again to complete the zero-point positioning and locking. In order to ensure that the clamping panel remains parallel and moves relatively during the opening and closing process, and to achieve quick disassembly and assembly and high-precision repeatable positioning of different specifications of jaw modules, a linear motion pair is formed by setting a precision clamping guide rail and a clamping slider. A zero-point quick-change component is integrated between the clamping slider and the clamping panel. Using its internal hydraulic locking and elastic reset mechanism, tool-free quick change is achieved. At the same time, the position of the clamping panel relative to the loading axis of the testing machine is consistent after the change, improving the comparability and repeatability of test data.

[0023] Preferably, the synchronous bidirectional clamping mechanism further includes a bidirectional screw rotatably connected to the upper surface of the floating platform. The outer surfaces of both ends of the bidirectional screw are respectively threaded into the internal threads of the clamping slider. A drive housing connected to the upper surface of the floating platform is installed on the outer surface of the bidirectional screw. Two meshing transmission gears are rotatably connected to the inner surface of the drive housing. One of the two transmission gears is fixedly sleeved on the outer surface of the bidirectional screw, and the other is fixedly connected to a drive motor.

[0024] To achieve continuous, equal, and centrally symmetrical adjustment of the jaw opening and avoid clamping center offset caused by unilateral adjustment, the above technical solution employs a bidirectional screw with opposite threads at both ends. This allows the two clamping sliders to move synchronously towards or away from each other. The torque of the drive motor is transmitted through multi-stage transmission gears within the drive housing. Different transmission ratios are selected based on the sample size to achieve rapid feeding and precise fine-tuning, ensuring that the sample is always clamped in the center position of the clamping mechanism. This is especially important for meeting the high requirements of uniform clamping force distribution for brittle epoxy resin samples.

[0025] Preferably, the replaceable composite jaw module includes the zero-point quick-change component, the clamping panel, and a flexible buffer pad that is locked and fixed to one side surface of the clamping panel by an M6 set screw. The flexible buffer pad is a replaceable structure and includes three specifications: polyurethane (PU) pad, polytetrafluoroethylene (PTFE) pad, and fiberglass fabric rubber pad, which are respectively adapted to conventional epoxy castings, ultra-thin epoxy films, and high-load epoxy samples. The flexible buffer pad is the working surface of the jaw.

[0026] To adapt to the clamping requirements of various specifications such as conventional epoxy castings, ultra-thin epoxy films, and high-load epoxy samples, and to avoid stress concentration leading to sample cracking or tensile slippage, the above technical solution uses a zero-point quick-change assembly to achieve rapid positioning connection between the clamping panel and the drive unit. The clamping panel is fixed with replaceable flexible buffer pads by M6 set screws. Three types of pads are used to correspond to different working conditions. The flexible deformation of the pads absorbs the peak clamping pressure and increases the frictional contact area, effectively suppressing sample damage and slippage.

[0027] Preferably, the clamping and testing fixture is equipped with a complete mechanical property verification calculation system to adapt to the high-precision clamping and testing conditions of brittle epoxy resin samples. Through multi-dimensional verification formulas, it achieves precise and controllable clamping conditions, avoiding defects such as eccentric force, clamping cracking, and tensile slippage. The calculation system includes:

[0028] Formula for calculating eccentric additional bending moment: .

[0029] Formula for calculating total stress in specimen cross section: .

[0030] Precise formula for calculating lead screw clamping force: .

[0031] Sample anti-slip safety check formula: ,in For the eccentricity, For tensile load, The cross-sectional area of ​​the sample is... For eccentric bending moment, The furthest fiber distance in the sample cross-section. Let the moment of inertia of the cross section be... Apply torque to the knob, For lead screw drive efficiency. For the lead screw, The coefficient of friction between the gasket and the epoxy resin. For the clamping force of the jaws, To maximize anti-slip load-bearing capacity, This represents the maximum test load on the specimen.

[0032] To quantitatively assess the clamping state and avoid experimental defects such as eccentric force, clamping cracking, and tensile slippage through the above technical solution, a complete mechanical performance verification calculation system is configured. This system covers the formulas for eccentric additional bending moment, total cross-sectional stress, screw clamping force, and anti-slip safety verification. It quantifies loading eccentricity, bending-tension coupling stress, the relationship between input torque and clamping force, and friction reserve from multiple dimensions, providing operators with clear parameter setting basis and ensuring that clamping parameters are scientifically controllable. This system is particularly suitable for high-precision clamping and testing of brittle epoxy resin materials.

[0033] The beneficial effects of this invention are as follows:

[0034] 1. By setting up a floating self-centering mechanism, using cross-shaped guide grooves and four sets of floating sliders working in tandem, and coordinating with axial and radial linear guide rails arranged in layers orthogonally, two-dimensional floating adjustment motion decoupling in the horizontal plane is achieved; at the same time, by utilizing the combination of disc spring elastic energy storage structure and mountain-shaped push-pull groove, the floating platform can automatically make slight adjustments with the center of the sample after clamping. After centering, it can provide sufficient rigid holding force through the disc spring group. Through the above technical solution, the additional eccentric load introduced by the initial deviation of sample clamping is effectively eliminated, avoiding the bending or breakage of the sample due to rigid tension. It takes into account the dual requirements of compliant centering and stable clamping, and significantly improves the clamping centering accuracy and the reliability of test data.

[0035] 2. By setting up a synchronous bidirectional clamping mechanism, a bidirectional screw and multi-stage transmission gears are used to achieve synchronous movement of the two clamping sliders in opposite directions or back directions. This ensures that the jaw opening is continuously and equally adjustable and that the clamping center is always located at the geometric center of the mechanism. At the same time, a replaceable flexible buffer pad is set on the inner side of the clamping panel. The flexible deformation of the pad absorbs the peak clamping pressure, avoids stress concentration that could lead to sample cracking, and effectively suppresses slippage during the tensile process by increasing the friction contact area. Combined with a complete mechanical property verification and calculation system, quantitative evaluation is carried out from four dimensions: eccentric force, cross-sectional stress, clamping force output, and anti-slip safety. Through the above technical solutions, the clamping state is accurately controllable. The system systematically avoids test defects such as eccentric force, clamping cracking, and tensile slippage from both structural design and theoretical calculation levels. It is especially suitable for testing conditions where brittle epoxy resin materials are extremely sensitive to clamping damage. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of a universal testing machine adapted to a multi-specification epoxy resin sample clamping and testing fixture proposed in this invention.

[0037] Figure 2 This is a three-dimensional view of a movable integrated plate structure for a universal testing machine adapted to a multi-specification epoxy resin sample clamping and testing fixture proposed in this invention.

[0038] Figure 3 This is a three-dimensional view of a standard connection joint structure for a universal testing machine adapted to a multi-specification epoxy resin sample clamping and testing fixture proposed in this invention.

[0039] Figure 4 This is a perspective view of a fixed floating base structure for a universal testing machine adapted to a multi-specification epoxy resin sample clamping and testing fixture proposed in this invention.

[0040] Figure 5 This is a three-dimensional view of a guide slide structure for a universal testing machine adapted to a multi-specification epoxy resin sample clamping and testing fixture proposed in this invention.

[0041] Figure 6 This is a three-dimensional view of a floating slider structure for a universal testing machine adapted to a multi-specification epoxy resin sample clamping and testing fixture proposed in this invention.

[0042] Figure 7 This is a perspective view of the linkage shell structure of a universal testing machine adapted to a multi-specification epoxy resin sample clamping and testing fixture proposed in this invention.

[0043] Figure 8 This is a perspective view of the active bevel gear structure of a universal testing machine adapted to a multi-specification epoxy resin sample clamping and testing fixture proposed in this invention.

[0044] Figure 9 This is a three-dimensional view of a floating platform structure for a universal testing machine adapted to a multi-specification epoxy resin sample clamping and testing fixture proposed in this invention.

[0045] Figure 10 This is a perspective view of a push-pull groove structure for a universal testing machine adapted to a multi-specification epoxy resin sample clamping and testing fixture proposed in this invention.

[0046] Figure 11 This is a three-dimensional view of a disc spring structure for a universal testing machine adapted to a multi-specification epoxy resin sample clamping and testing fixture proposed in this invention.

[0047] Figure 12 This is a perspective view of a bidirectional screw structure for a universal testing machine adapted to a multi-specification epoxy resin sample clamping and testing fixture proposed in this invention.

[0048] Figure 13 This is a three-dimensional view of a flexible buffer pad structure for a universal testing machine adapted to a multi-specification epoxy resin sample clamping and testing fixture proposed in this invention.

[0049] Figure 14 This is a cross-sectional view of the zero-point quick-change assembly of a universal testing machine adapted to a multi-specification epoxy resin sample clamping and testing fixture proposed in this invention.

[0050] In the diagram: 1. Main body of the testing machine; 11. Fixed integrated plate; 12. Moving integrated plate; 13. Tooling assembly; 2. Standard connecting joint; 3. Floating self-centering mechanism; 31. Fixed floating base; 32. Guide slide; 33. Floating slider; 34. Linkage housing; 35. Axial linear slide rail; 36. Axial slider; 37. Radial linear slide rail; 38. Radial slider; 39. Floating platform; 40. Push block; 41. Guide block; 42. Disc spring; 43. Push 44. Groove; 45. Floating screw; 46. Linkage block; 47. Connecting rod; 48. Driven bevel gear; 49. Driven bevel gear; 50. Gearbox; 6. Synchronous bidirectional clamping mechanism; 61. Clamping guide rail; 62. Clamping slider; 63. Zero-point quick-change assembly; 64. Clamping panel; 65. Bidirectional screw; 66. Drive housing; 67. Transmission gear; 68. Drive motor; 7. Replaceable composite jaw module; 71. Flexible buffer pad. Detailed Implementation

[0051] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0052] Reference Figures 1-14 A universal testing machine is adapted to a multi-specification epoxy resin sample clamping and testing fixture, including a testing machine body 1. A fixed integrated plate 11 is fixedly connected to the upper surface of the testing machine body 1. A movable integrated plate 12 is slidably connected to the outer surface of the guide component of the testing machine body 1. A fixture assembly 13 is arranged on the opposite side surface of the fixed integrated plate 11 and the movable integrated plate 12. Each fixture assembly 13 includes a standard connecting joint 2, a floating self-centering mechanism 3, a synchronous bidirectional clamping mechanism 6, and a replaceable composite jaw module 7, which are assembled sequentially from top to bottom.

[0053] Standard connector 2 is used for quick docking and positioning with the loading end of the universal testing machine.

[0054] The lower surface of the floating self-aligning mechanism 3 is rigidly fixed to the standard connecting joint 2, and the upper part of the floating self-aligning mechanism 3 is connected to the synchronous bidirectional clamping mechanism 6 to realize the adaptive micro-alignment compensation in the horizontal plane.

[0055] The synchronous bidirectional clamping mechanism 6 adopts a bidirectional synchronous adjustment structure to achieve continuous adjustment of the jaw opening.

[0056] The composite jaw module can be detachably installed at the end of the synchronous bidirectional clamping mechanism 6, and is suitable for epoxy resin samples of various specifications. The inner side of the composite jaw module is detachably equipped with a flexible anti-slip buffer pad.

[0057] To ensure that the floating slider 33 obtains accurate and independent sliding guidance in mutually perpendicular directions and provides a stable motion basis for subsequent multi-dimensional centering adjustment, the floating self-centering mechanism 3 includes a fixed floating base 31 fixedly connected to the upper surface of the standard connecting joint 2. A cross-shaped guide groove 32 is provided on the upper surface of the fixed floating base 31. The floating slider 33 is slidably engaged in the inner surface of the four support grooves of the guide groove 32. By setting the cross-shaped guide groove 32 and the floating slider 33 slidably engaged in the four support grooves, the rotational motion of the driving component can be converted into linear displacement, thereby effectively eliminating the additional eccentric load introduced by the initial deviation of the sample clamping.

[0058] To achieve decoupled motion for two-dimensional floating adjustment in the horizontal plane and ensure that the upper clamping mechanism has good installation rigidity and micro-displacement compensation capability in any direction in the plane, the floating self-centering mechanism 3 also includes a linkage housing 34 fixedly connected to the bottom wall of the guide slide 32. The upper surface of the linkage housing 34 is fixedly connected to an axial linear slide rail 35 arranged in parallel. An axial slider 36 is slidably engaged on the outer surface of the axial linear slide rail 35. A radial linear slide rail 37 is fixedly connected to the upper surface of the axial slider 36 arranged in parallel. A radial slider 38 is fixedly connected to the outer surface of the radial linear slide rail 37. A T-shaped floating platform 39 is fixedly connected to the upper surface of the radial slider 38. By adopting a layered orthogonal stacking arrangement of the axial linear slide rail 35 and the radial linear slide rail 37, the axial slider 36 drives the radial linear slide rail 37 to move axially, and the radial slider 38 moves radially relative to it. The two movements do not interfere with each other. The T-shaped floating platform 39 serves as the final bearing base to cooperate in completing adaptive centering, avoiding bending or breakage of the sample due to rigid tension.

[0059] To enable the floating platform 39 to automatically and slightly adjust with the center of the sample in the horizontal plane while maintaining sufficient rigidity and stability after centering, the floating self-centering mechanism 3 also includes an L-shaped push block 40 fixedly connected to the surface of the floating slider 33 near the floating platform 39. The upper surface of the push block 40 is fixedly connected to guide blocks 41 distributed inward and outward. Disc springs 42 are fixedly connected to the opposite side surfaces of the two guide blocks 41. The lower surface of the floating platform 39 has an annular mountain-shaped push-pull groove 43. The free ends of the two disc springs 42 are fixedly connected to the two sides of the middle plate of the push-pull groove 43. The linear displacement of the floating slider 33 is converted into a push-pull on the guide blocks 41 by the L-shaped push block 40. The two guide blocks 41 clamp the disc springs 42 to form an elastic energy storage structure. The free ends of the disc springs 42 are fixedly connected to the middle plate of the mountain-shaped push-pull groove 43 on the lower surface of the floating platform 39. The compression and rebound of the disc springs 42 generate an adaptive balance force, taking into account both the requirements of compliant centering and stable clamping.

[0060] To achieve active, symmetrical, and uniform drive adjustment of the floating slider 33 and improve transmission efficiency and service life, the floating self-centering mechanism 3 also includes rotating grooves 44 arranged in a ring array inside the fixed floating base 31. The upper end of the rotating grooves 44 is fixedly connected to the lower end of the corresponding guide grooves 32. The interior of the rotating grooves 44 is rotatably connected to floating screws 45 via bearings. The two opposing floating screws 45 are bidirectionally arranged and rotate synchronously. The outer surface of the floating screws 45 is threaded with a linkage block 46. The upper surface of the linkage block 46 is fixedly connected to the lower surface of the floating slider 33. By setting the rotating grooves 44 arranged in a ring array and the floating screws 45 rotatably connected inside via bearings, the two opposing floating screws 45 adopt bidirectional threads and rotate synchronously. The linkage block 46, which is threaded, converts the screw rotation into the opposite or opposite linear motion of the floating slider 33, ensuring that the centering adjustment in any direction has good symmetry and uniformity, and avoiding secondary eccentricity caused by unilateral adjustment.

[0061] To achieve synchronized control of the four-directional floating sliders 33 and ensure consistent motion of the floating platform 39 when translating in any direction in the horizontal plane, connecting rods 47 are fixedly connected to one side of the two radial floating screws 45. The connecting rods 47 are rotatably connected to the surface of the linkage housing 34 via bearings. Driven bevel gears 48 are rotatably connected to the inner surface of the axially opposite side of the linkage housing 34 via bearings. A driving bevel gear 49 is rotatably connected to the inner top wall of the linkage housing 34 via bearings. The two driven bevel gears 48 mesh with the driving bevel gears 49 respectively, fixing the floating... A geared motor 50 is fixedly connected to an adjacent side surface of the base 31. The output shafts of the two geared motors 50 are fixedly connected to one side surface of the corresponding floating screw 45. The radial floating screw 45 is directly driven by the geared motor 50, and coaxial power is transmitted through the connecting rod 47. In the axial direction, the driving bevel gear 49 meshes with two driven bevel gears 48 and transmits the power to the two axially opposite floating screws 45 through the connecting rod 47. This forms a compact and precise bevel gear transmission structure, which, together with the geared motor 50, provides sufficient driving torque for automated centering control.

[0062] By setting up a floating self-centering mechanism 3, using cross-shaped guide rails 32 and four sets of floating sliders 33 working together, and coordinating with axial linear rails 35 and radial linear rails 37 arranged in layers orthogonally, two-dimensional floating adjustment motion decoupling in the horizontal plane is achieved; at the same time, by utilizing the elastic energy storage structure of disc springs 42 and the cooperation of mountain-shaped push-pull grooves 43, the floating platform 39 can automatically and slightly adjust with the center of the sample after the sample is clamped. After centering, it can provide sufficient rigid holding force through the disc spring group. Through the above technical solution, the additional eccentric load introduced by the initial deviation of the sample clamping is effectively eliminated, and the sample is prevented from bending or breaking due to rigid tension. It takes into account the dual requirements of compliant centering and stable clamping, and significantly improves the clamping centering accuracy and the reliability of test data.

[0063] To ensure that the clamping panel 64 remains parallel and moves relatively during opening and closing, and to achieve rapid assembly and disassembly and high-precision repeatability of different jaw modules, the synchronous bidirectional clamping mechanism 6 includes a clamping guide rail 61 fixedly connected to the upper surface of the floating platform 39. Clamping sliders 62, distributed relatively to each other, are slidably engaged on the outer surface of the clamping guide rail 61. A zero-point quick-change assembly 63 is fixedly connected to the upper surface of the clamping sliders 62. The clamping panel 64 is fixedly connected to the surface of the central pull rod of the zero-point quick-change assembly 63. By setting the precision clamping guide rail 61 and the clamping sliders 62 to form a linear motion pair, and integrating the zero-point quick-change assembly 63 between the clamping sliders 62 and the clamping panel 64, tool-free quick replacement is achieved using its internal hydraulic locking and elastic reset mechanism. This ensures the consistency of the position of the clamping panel 64 relative to the loading axis of the testing machine after replacement, improving the comparability and repeatability of test data. The zero-point quick-change assembly 63 includes an integrated rigid base. The base body integrates a hydraulic oil circuit and is equipped with an external hydraulic oil port and a hydraulic drive plunger. The hollow cavity inside the base is equipped with a locking actuator and an elastic preload reset assembly. The locking actuator includes a transversely arranged central tie rod, symmetrically arranged wedge-shaped locking claws, and support rollers on the back of the locking claws. The elastic preload reset assembly consists of multiple symmetrically stacked disc springs. One end of the disc spring assembly abuts against the inner wall of the base, and the other end presses against the wedge-shaped locking claws through the support rollers. The bottom of the base is equipped with a positioning stop for unified reference positioning. Under normal conditions, the preload force output by the disc spring assembly is used to squeeze the wedge-shaped locking claws through the support rollers and cooperate with the wedge surface of the central tie rod to achieve mechanical self-locking clamping of the workpiece stud. Hydraulic oil is introduced into the oil circuit to push the hydraulic drive plunger to push the central tie rod axially to release the radial compression of the wedge surface on the locking claws and compress the disc spring assembly to open the locking claws and release the workpiece. After hydraulic pressure is released, the disc spring assembly rebounds and can drive the locking claws to close again to complete the zero-point positioning and locking.

[0064] To achieve continuous, equal, and centrally symmetrical adjustment of the jaw opening and avoid clamping center offset caused by unilateral adjustment, the synchronous bidirectional clamping mechanism 6 also includes a bidirectional screw 65 rotatably connected to the upper surface of the floating platform 39. The outer surfaces of both ends of the bidirectional screw 65 are respectively threaded into the internal threads of the clamping sliders 62. A drive housing 66 connected to the upper surface of the floating platform 39 is installed on the outer surface of the bidirectional screw 65. Two meshing transmission gears 67 are rotatably connected to the inner surface of the drive housing 66. One of the two transmission gears 67 is fixedly sleeved on the outer surface of the bidirectional screw 65, and the other is fixedly connected to a drive motor 68. By using a bidirectional screw 65 with opposite thread directions at both ends, the two clamping sliders 62 can move synchronously towards or away from each other. The torque of the drive motor 68 is transmitted through the meshing of the multi-stage transmission gears 67 in the drive housing 66. Different transmission ratios can be selected according to the sample size to achieve rapid feeding and precise fine adjustment, ensuring that the sample is always clamped in the center position of the clamping mechanism, especially meeting the high requirements of uniform clamping force distribution for brittle epoxy resin samples.

[0065] To accommodate various clamping requirements, including conventional epoxy castings, ultra-thin epoxy films, and high-load epoxy specimens, and to prevent stress concentration that could lead to specimen cracking or tensile slippage, a replaceable composite jaw module 7 is provided. This module includes a zero-point quick-change assembly 63, a clamping panel 64, and a flexible buffer pad 71 secured to one side of the clamping panel 64 by an M6 set screw. The flexible buffer pad 71 is replaceable and comes in three sizes: polyurethane (PU), polytetrafluoroethylene (PTFE), and fiberglass fabric rubber, to accommodate conventional epoxy castings, ultra-thin epoxy films, and high-load epoxy specimens, respectively. The flexible buffer pad 71 serves as the working surface of the jaws. The zero-point quick-change assembly 63 enables rapid positioning and connection between the clamping panel 64 and the drive unit. The clamping panel 64 is secured to the replaceable flexible buffer pad 71 by an M6 set screw. The three types of pads correspond to different working conditions, utilizing the flexible deformation of the pads to absorb peak clamping pressure and increase the frictional contact area, effectively suppressing specimen damage and slippage.

[0066] To quantitatively assess the clamping condition and avoid test defects such as eccentric stress, clamping cracking, and tensile slippage, a complete mechanical property verification calculation system is configured for the clamping and testing fixture. This system is adapted to the high-precision clamping and testing conditions of brittle epoxy resin samples. Through multi-dimensional verification formulas, the clamping condition is accurately and controllably controlled, avoiding test defects such as eccentric stress, clamping cracking, and tensile slippage. The calculation system includes:

[0067] Formula for calculating eccentric additional bending moment: .

[0068] Formula for calculating total stress in specimen cross section: .

[0069] Precise formula for calculating lead screw clamping force: .

[0070] Sample anti-slip safety check formula: ,in For the eccentricity, For tensile load, The cross-sectional area of ​​the sample is... For eccentric bending moment, The furthest fiber distance in the sample cross-section. Let the moment of inertia of the cross section be... Apply torque to the knob, For lead screw drive efficiency. For the lead screw, The coefficient of friction between the gasket and the epoxy resin. For the clamping force of the jaws, To maximize anti-slip load-bearing capacity, To determine the maximum test load for the sample, a complete mechanical property verification calculation system is configured, covering formulas for eccentric additional bending moment, total stress of cross section, screw clamping force, and anti-slip safety verification. It quantifies loading eccentricity, bending-tension coupling stress, the relationship between input torque and clamping force, and friction reserve from multiple dimensions, providing operators with clear parameter setting basis and ensuring that clamping parameters are scientifically controllable. It is particularly suitable for high-precision clamping and testing of brittle epoxy resin materials.

[0071] By setting up a synchronous bidirectional clamping mechanism 6, a bidirectional screw 65 is used in conjunction with a multi-stage transmission gear 67 to achieve synchronous movement of the two clamping sliders 62 in opposite directions or in opposite directions. This ensures that the jaw opening is continuously and equally adjustable and that the clamping center is always located at the geometric center of the mechanism. At the same time, a replaceable flexible buffer pad 71 is set on the inner side of the clamping panel 64. The flexible deformation of the pad absorbs the peak clamping pressure, avoids stress concentration that could lead to sample cracking, and effectively suppresses slippage during the tensile process by increasing the friction contact area. With the help of a complete mechanical property verification calculation system, quantitative evaluation is carried out from four dimensions: eccentric force, cross-sectional stress, clamping force output, and anti-slip safety. Through the above technical solutions, the clamping state is accurately controllable. The system avoids test defects such as eccentric force, clamping cracking, and tensile slippage from both structural design and theoretical calculation levels. It is especially suitable for testing conditions where brittle epoxy resin materials are extremely sensitive to clamping damage.

[0072] Working principle: In a specific embodiment of the present invention, two sets of tooling assemblies 13 are arranged opposite to each other. The upper set is fixedly installed on the upper surface of the main body 1 of the testing machine via a fixed integrated plate 11 as a reference end. The lower set is slidably snapped onto the outer surface of the guide component of the testing machine via a movable integrated plate 12 and moves with the loading beam to adapt to specimens of different lengths. During installation, the upper and lower sets of tooling assemblies 13 are quickly docked and positioned with the loading end of the universal testing machine via standard connecting joints 2 to ensure the coaxiality of the tooling assembly 13 and the loading axis of the testing machine.

[0073] After the sample is placed between the upper and lower composite jaw modules, the drive motor 68 drives the bidirectional screw 65 to rotate via the transmission gear 67. The reverse threads at both ends of the bidirectional screw 65 drive the two clamping sliders 62 to slide synchronously towards each other on the clamping guide rail 61. Then, through the zero-point quick-change component 63, the clamping panel 64 and the flexible buffer pad 71 are driven to move closer to the sample and apply the initial clamping force. During this process, if there is a slight eccentricity between the sample center and the loading axis, the eccentric component force is transmitted to the floating platform 39 through the clamping slider 62. The mountain-shaped push-pull groove 43 on the lower surface of the floating platform 39 forms an elastic linkage with the floating slider 33 through the disc spring 42 and the guide block 41. The push-pull groove 43 pushes the disc spring 42 in the corresponding direction to compress or rebound. The deformation of the disc spring 42 is fed back to the floating slider 33 through the L-shaped push block 40. The floating slider 33 generates a corresponding displacement in the cross-shaped guide groove 32. At the same time, the axial linear slide rail 35 and the radial linear slide rail 37 are orthogonally stacked in layers to decouple the axial movement and radial movement so that they do not interfere with each other. The two work together to make the floating platform 39 adaptively translate in the horizontal plane until the sample center coincides with the loading axis. The disc spring group restores balance and self-locks to maintain the center position.

[0074] After the specimen is automatically aligned, the operator drives the bidirectional screw 65 to tighten it further by inputting external torque according to the clamping torque parameters pre-calculated by the mechanical property verification calculation system. The screw clamping force calculation formula quantitatively converts the input torque into the actual clamping force of the jaws. This clamping force is transmitted to the clamping panel 64 through the clamping slider 62 and the zero-point quick-change component 63, and finally acts on the contact surface between the flexible buffer pad 71 and the specimen. At the same time, the static friction force generated between the pad and the specimen is ensured by the anti-slip safety verification formula to ensure that the friction force reserve is always greater than the maximum test load in the subsequent tensile test. After the universal testing machine starts the tensile program, the moving integrated plate 12 moves upward along the guide component, driving the upper tooling assembly 13 to apply an axial tensile load to the specimen. The load is transmitted to the clamping panel 64 and the specimen through the standard connecting joint 2 and the floating self-centering mechanism 3. If a new eccentricity trend occurs during the tensile process due to material inhomogeneity or slight slippage of the clamping end, the floating self-centering mechanism 3 will restart the above-mentioned elastic adaptive adjustment mechanism to compensate for the instantaneous eccentricity in real time, so that the tensile load is always applied along the specimen axis, avoiding premature fracture of the specimen due to the additional bending moment caused by eccentricity, and the total stress of the specimen section is always within a controllable range, ensuring the authenticity and validity of the test data.

[0075] When it is necessary to switch to epoxy resin samples of different specifications or materials, there is no need to disassemble the entire tooling assembly 13. Quick change can be achieved through the zero-point quick change component 63: Under normal conditions, the disc spring assembly inside the zero-point quick change component 63 outputs preload force, which is used by the support roller to squeeze the wedge-shaped locking claw. This, together with the wedge surface of the central tie rod, achieves mechanical self-locking clamping of the pull studs of the clamping panel 64. When changing, hydraulic oil is introduced into the zero-point quick change component 63. The hydraulic oil pushes the hydraulic drive plunger to push the central tie rod axially, releasing the radial compression of the locking claws on the wedge surface and compressing the disc spring assembly to open the locking claws and release the workpiece. The original clamping panel 64 and flexible buffer pad 71 can then be removed. When installing the new module, simply push the pull studs of the new clamping panel 64 into the base. After removing the hydraulic oil, the disc spring assembly rebounds and drives the locking claws to close, completing the zero-point positioning and locking. The entire process requires no additional tools, and the positioning stop ensures that the positional accuracy of the clamping panel 64 relative to the loading axis remains unchanged after the change.

[0076] The composite jaw module is equipped with three types of flexible buffer pads 71: polyurethane (PU), polytetrafluoroethylene (PTFE), and glass fiber fabric rubber. These pads are adapted to different clamping requirements of conventional epoxy castings, ultra-thin epoxy films, and high-load epoxy samples, respectively. This enables the machine to quickly switch between multiple sample specifications and is versatile enough to significantly expand the universal testing machine's adaptability to epoxy resin samples of different shapes.

[0077] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A universal testing machine adapted to a multi-specification epoxy resin sample clamping and testing fixture, comprising a testing machine body (1), characterized in that: A fixed integrated plate (11) is fixedly connected to the upper surface of the main body (1) of the testing machine. A movable integrated plate (12) is slidably connected to the outer surface of the guide component of the main body (1). A tooling assembly (13) is arranged on the opposite side surface of the fixed integrated plate (11) and the movable integrated plate (12). Each tooling assembly (13) includes a standard connecting joint (2), a floating self-centering mechanism (3), a synchronous bidirectional clamping mechanism (6), and a replaceable composite jaw module (7) assembled sequentially from top to bottom. The standard connector (2) is used for quick docking and positioning with the loading end of the universal testing machine; The lower surface of the floating self-aligning mechanism (3) is rigidly fixed to the standard connecting joint (2), and the synchronous bidirectional clamping mechanism (6) is connected above the floating self-aligning mechanism (3) to realize adaptive micro-alignment compensation on the horizontal plane; The synchronous bidirectional clamping mechanism (6) adopts a bidirectional synchronous adjustment structure to realize continuous adjustment of the jaw opening; The composite jaw module can be detachably installed at the end of the synchronous bidirectional clamping mechanism (6) and is suitable for epoxy resin samples of various specifications. A flexible anti-slip buffer pad can be detachably installed on the inner side of the composite jaw module.

2. The universal testing machine-compatible epoxy resin multi-specification sample clamping and testing fixture according to claim 1, characterized in that: The floating self-centering mechanism (3) includes a fixed floating base (31) fixedly connected to the upper surface of the standard connection joint (2). A cross-shaped guide groove (32) is provided on the upper surface of the fixed floating base (31). Floating sliders (33) are slidably engaged on the inner surfaces of the four support grooves of the guide groove (32).

3. The universal testing machine-compatible epoxy resin multi-specification sample clamping and testing fixture according to claim 2, characterized in that: The floating self-centering mechanism (3) further includes a linkage housing (34) fixedly connected to the bottom wall of the guide slide (32). The upper surface of the linkage housing (34) is fixedly connected to an axial linear slide rail (35) arranged in parallel. An axial slider (36) is slidably engaged on the outer surface of the axial linear slide rail (35). A radial linear slide rail (37) arranged in parallel is fixedly connected to the upper surface of the axial slider (36). A radial slider (38) is fixedly connected to the outer surface of the radial linear slide rail (37). A T-shaped floating platform (39) is fixedly connected to the upper surface of the radial slider (38).

4. The universal testing machine-compatible epoxy resin multi-specification sample clamping and testing fixture according to claim 3, characterized in that: The floating self-centering mechanism (3) also includes an L-shaped push block (40) fixedly connected to the surface of the floating slider (33) near the floating platform (39). The upper surface of the push block (40) is fixedly connected to guide blocks (41) distributed inward and outward. The opposite side surfaces of the two guide blocks (41) are fixedly connected to disc springs (42). The lower surface of the floating platform (39) is provided with an annular mountain-shaped push-pull groove (43). The free ends of the two disc springs (42) are fixedly connected to the two sides of the middle plate of the push-pull groove (43).

5. The universal testing machine-compatible epoxy resin multi-specification sample clamping and testing fixture according to claim 4, characterized in that: The floating self-centering mechanism (3) also includes rotating grooves (44) arranged in a ring array inside the fixed floating base (31). The upper end of the rotating groove (44) is fixedly connected to the lower end of the corresponding guide groove (32). The interior of the rotating groove (44) is rotatably connected to a floating screw (45) through a bearing. The two opposing floating screws (45) are bidirectionally arranged and rotate synchronously. The outer surface of the floating screw (45) is threaded with a linkage tube block (46). The upper surface of the linkage tube block (46) is fixedly connected to the lower surface of the floating slider (33).

6. The universal testing machine-compatible epoxy resin multi-specification sample clamping and testing fixture according to claim 5, characterized in that: A connecting rod (47) is fixedly connected to one side surface of the two radial floating screws (45). The connecting rod (47) is rotatably connected to the surface of the linkage housing (34) through a bearing. A driven bevel gear (48) is rotatably connected to the inner surface of the axially opposite side of the linkage housing (34) through a bearing. A driving bevel gear (49) is rotatably connected to the inner top wall of the linkage housing (34) through a bearing. The two driven bevel gears (48) mesh with the driving bevel gear (49) respectively. A geared motor (50) is fixedly connected to the adjacent side surface of the fixed floating base (31). The output shafts of the two geared motors (50) are fixedly connected to one side surface of the corresponding floating screw (45) respectively.

7. The universal testing machine-compatible epoxy resin multi-specification sample clamping and testing fixture according to claim 6, characterized in that: The synchronous bidirectional clamping mechanism (6) includes a clamping guide rail (61) fixedly connected to the upper surface of the floating platform (39). The outer surface of the clamping guide rail (61) is slidably engaged with clamping sliders (62) that are relatively distributed. The upper surface of the clamping sliders (62) is fixedly connected with a zero-point quick-change assembly (63). The surface of the central pull rod of the zero-point quick-change assembly (63) is fixedly connected with a clamping panel (64).

8. The universal testing machine-compatible epoxy resin multi-specification sample clamping and testing fixture according to claim 7, characterized in that: The synchronous bidirectional clamping mechanism (6) further includes a bidirectional screw (65) rotatably connected to the upper surface of the floating platform (39). The outer surfaces of both ends of the bidirectional screw (65) are respectively threaded into the internal threads of the clamping slider (62). The outer surface of the bidirectional screw (65) is equipped with a drive housing (66) connected to the upper surface of the floating platform (39). The inner surface of the drive housing (66) is rotatably connected with two meshing transmission gears (67). One of the two transmission gears (67) is fixedly sleeved on the outer surface of the bidirectional screw (65), and the other is fixedly connected to a drive motor (68).

9. The universal testing machine-compatible epoxy resin multi-specification sample clamping and testing fixture according to claim 7, characterized in that: The replaceable composite jaw module (7) includes the zero-point quick-change assembly (63), the clamping panel (64), and a flexible buffer pad (71) that is locked and fixed to one side surface of the clamping panel (64) by an M6 set screw. The flexible buffer pad (71) is a replaceable structure and includes three specifications: polyurethane (PU) pad, polytetrafluoroethylene (PTFE) pad, and fiberglass fabric rubber pad, which are respectively adapted to conventional epoxy castings, ultra-thin epoxy films, and high-load epoxy samples. The flexible buffer pad (71) is the working surface of the jaw.

10. A universal testing machine-compatible epoxy resin multi-specification sample clamping and testing fixture according to claim 9, characterized in that: The clamping and testing fixture is equipped with a complete mechanical property verification calculation system, which is used to adapt to the high-precision clamping and testing conditions of epoxy resin brittle samples. Through multi-dimensional verification formulas, it achieves precise and controllable clamping conditions, avoiding defects such as eccentric force, clamping cracking, and tensile slippage in tests. The calculation system includes: Formula for calculating eccentric additional bending moment: ; Formula for calculating total stress in specimen cross section: ; Precise formula for calculating lead screw clamping force: ; Sample anti-slip safety check formula: ,in For the eccentricity, For tensile load, The cross-sectional area of ​​the sample is... For eccentric bending moment, The furthest fiber distance in the sample cross-section. Let the moment of inertia of the cross section be... Apply torque to the knob, For lead screw drive efficiency. For the lead screw, The coefficient of friction between the gasket and the epoxy resin. For the clamping force of the jaws, To maximize anti-slip load-bearing capacity, This represents the maximum test load on the specimen.

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