A small-size variable-angle tensile mechanics experimental platform, design method and working method

Abstract

The application provides a small-size variable-angle tensile mechanics experiment platform, a design method and a working method, and belongs to the technical field of experiment equipment. The problem that the overall size of the experiment platform is large and it is inconvenient to observe the mechanical phenomena of the experiment sample is solved. The technical scheme is as follows: the platform comprises a platform base, a movable pull hook, a displacement screw, a transmission screw and a split loading platform; the platform base is provided with a smooth groove on an XY plane, 1-4 movable pull hooks can be loaded, the displacement screw is coaxially loaded on the platform on the inner side of the pull hook, an annular groove is arranged at the position close to the end, the transmission screw is tightly connected with the movable pull hook in the Z-axis direction, and the end is arranged in the groove of the displacement screw. The application has the advantages of small size, high loading precision and arbitrary tensile direction, avoids the problems that the size of the current mechanics experiment equipment is too large, it is difficult to study the mechanical phenomena of micron-level two-dimensional materials, and the real-time observation of the tensile failure process is difficult.

Description

Technical Field

[0001] This invention relates to the field of experimental equipment technology, and in particular to a small-sized variable-angle tensile mechanics experimental platform, its design method, and its working method. Background Technology

[0002] In recent years, the microscopic tensile properties of micron-scale two-dimensional materials have attracted increasing attention. The microscopic elastic modulus and tensile strength of two-dimensional materials are closely related to their performance. For example, the bendable angle of a flexible screen is affected by the maximum tensile strain before fracture; the performance of the robotic arm in medical nanorobots needs to consider the elastic modulus; and the wind resistance of polymer mulch films in agricultural production requires materials with high tensile strength. Therefore, measuring these mechanical properties of micron-scale materials is of great significance for production and daily life. Tensile testing is the most direct method for measuring the elastic modulus, Poisson's ratio, yield strength, and fracture strength of materials. Currently, in the research of micron-scale two-dimensional materials, the tensile mechanics experimental platform mainly adopts the uniaxial tensile principle, which has the following main drawbacks:

[0003] 1. Only unidirectional tensile loads can be applied. If the material has an anisotropic elastic modulus, a tensile test in a fixed direction cannot reflect the overall mechanical properties of the material and cannot produce mechanical phenomena under specific tensile stress.

[0004] 2. The experimental platform is relatively large in size, making it difficult to fit into the vacuum chamber of a scanning electron microscope and thus hindering the observation of the mechanical phenomena of the experimental samples.

[0005] Application No.: CN201810270421.4, Biaxial Tensile Mechanical Property Testing Instrument and In-situ Microscopic Mechanical Property Testing Equipment, which states: "This invention relates to a biaxial tensile mechanical property testing instrument and an in-situ microscopic mechanical property testing equipment. The biaxial tensile mechanical property testing instrument is mainly used for tensile testing of thin film materials. In use, the specimen to be tested is placed and fixed between the upper plate assembly and the lower plate assembly of the clamp. The tensile device is used to perform biaxial or uniaxial tensile testing on the specimen. Then, the force detection device is used to detect the force on the specimen in the tensile direction, and the displacement detection device is used to detect the dimensional changes of the specimen in the tensile direction. At the same time, because the tensile mechanical property testing instrument provided by this invention is small in size and compact in structure, it can be directly combined with Raman spectrometer, XRD, ultra-depth-of-field microscope or optical microscope to achieve in-situ characterization of the microscopic damage evolution of the tested specimen, providing a reference for studying the microscopic damage evolution law and failure mechanism of materials." However, its structure is too complex and the cost is high.

[0006] How to solve the above problems is the challenge faced by this invention. Summary of the Invention

[0007] The purpose of this invention is to provide a small-sized variable-angle tensile mechanics experimental platform, its design method, and its working method; it solves the problem that the overall size of the experimental platform is too large, making it inconvenient to observe the mechanical phenomena of the experimental samples; it has the advantages of small size, high loading accuracy, and arbitrary tensile direction, avoiding the problem that current mechanical experimental equipment is too large, making it difficult to conduct research on the mechanical phenomena of micron-level two-dimensional materials and to observe the tensile failure process in real time.

[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0009] The small-sized variable-angle tensile mechanics experimental platform of the present invention includes a platform base, a movable hook, a displacement screw, a transmission screw, and a separate loading platform;

[0010] The plane containing the upper surface of the platform base is the XY plane, and the direction perpendicular to the upper surface of the platform base is the Z-axis;

[0011] Each edge of the platform base is provided with a smooth groove, the size of each smooth groove is matched with each guide rail of the movable hook, and each movable hook is axially slidably connected to one edge of the platform base through several guide rails;

[0012] The movable hook consists of several guide rails, a middle section, and hooks. The movable hooks are machined in one piece by a CNC machine tool. The platform base is connected to several movable hooks. The platform base is connected to several movable hooks.

[0013] Each side of the platform base is connected to a movable hook lock. The displacement screw is coaxially mounted on the inside of the movable hook on the platform in a threaded manner. An annular groove is set at one end of the displacement screw. The transmission screw is connected to the middle section of the movable hook in the Z-axis direction in a threaded manner. The end of the transmission screw is placed in the annular groove of the displacement screw and is higher than the bottom of the groove. The split loading platform is a cross-shaped elastic body. The split loading platform has several holes. The size of the holes matches the size of the hook of the movable hook, and the hook is connected to the hole.

[0014] The displacement screw is a screw with threads of uniform size or a rod with precise displacement. Near the end of the displacement screw, there is an annular groove with a depth of half its radius. The width of the displacement screw is 1.2 times the diameter of the transmission screw. The end of the displacement screw is located in the cavity on the middle section of the moving hook.

[0015] The transmission screw is threaded to one side of the middle of the movable hook, and the end of the transmission screw is in the annular groove of the displacement screw, extending into the displacement screw at one-third of its radius.

[0016] The rotation of the groove of the displacement screw causes the end of the transmission screw to move horizontally, and the transmission screw and the moving hook slide as a whole.

[0017] The movable hook includes a guide rail, a middle section, and a hook. The movable hook is a rigidly connected whole. The middle section has a first hole inside along the rotation direction of the transmission screw, and the first hole is provided with a thread that matches the transmission screw. The movable hook has a second hole along the rotation direction of the displacement screw, and the diameter of the second hole is 1.5 times the diameter of the displacement screw. The middle section and the hook are machined from a single piece of isosceles trapezoidal column. The base angle of the isosceles trapezoidal column is 45°, the top surface is the upper surface of the hook, and the bottom surface is the lower surface of the middle section.

[0018] The split loading platform is a cross-shaped column made of elastic material. The elastic modulus and yield strength of the split loading platform are less than those of the movable hook. Each side of the split loading platform has holes, and the hook is connected to the split loading platform through the holes.

[0019] A design method for a small-sized variable-angle tensile mechanics experimental platform includes:

[0020] First, based on the material and size of the experimental sample, a1 determines the maximum tensile force F that needs to be applied to the split loading platform;

[0021] Based on the elastic modulus E of the split loading platform, the normal strain of the platform when the tensile force F is applied is ε=F / AE, where A is the cross-sectional area of ​​the split loading platform and the normal displacement of the platform is x=lε, where l is the side length of the split loading platform.

[0022] a3 When two hooks are attached, if the displacement of both hooks is half of the normal displacement of the platform, then when the split loading platform is subjected to a tensile force F, the displacement of each hook is s = lF / 2AE.

[0023] According to geometric relationships, L = 2s + a2 = 2s + 2h + a1, where L is the inner side length of the platform base, and h, a1, and a2 are the height, lower base, and upper base of the trapezoid on the upper and lower bases of the middle section, respectively.

[0024] According to the experimental requirements, the guide rail should meet the following conditions: s0>s, where s0 is the maximum sliding distance of a hook and s is the displacement of the hook at this time; the length of the displacement screw should meet the following condition: after installation, the first end should have sufficient distance outside the platform base to control the number of rotations;

[0025] According to the experimental requirements, the rotation angle θ of the displacement screw and the translational displacement s of the hook have the following relationship: s = θb / 2π, where b is the pitch of the displacement screw, s is the displacement of this hook at this time, and π is pi; furthermore, when the tension F is applied, the rotation angle θ of the displacement screw is θ = lFπ / bAE, where l is the side length of the split loading platform, A is the cross-sectional area of ​​the split loading platform, and E is the elastic modulus of the split loading platform.

[0026] A working method for a small-sized variable-angle tensile mechanics experimental platform includes:

[0027] b1 fixes the experimental sample on a separate loading platform, so that the experimental sample deforms synchronously;

[0028] During unidirectional tensioning, only two opposite sides of the split loading platform are connected to the movable hook, displacement screw, and transmission screw. Rotating the displacement screw outward causes its groove to move the end of the transmission screw outward. Since the transmission screw and movable hook are rigidly connected, and the contact surface between the movable hook and the platform base is smooth with low friction, the movable hook also moves synchronously outward, providing unidirectional tension. When the rotation angle θ of both displacement screws is θ = lFπ / bAE, the tension applied to the split loading platform is F, where l is the side length of the split loading platform and A is the cross-sectional area of ​​the split loading platform. E is the elastic modulus of the split loading platform, b is the pitch of the displacement screw, and π is pi. When performing variable angle tensioning, the split loading platform is connected to four movable hooks, controlling two opposite displacement screws to rotate outward by an angle θ1, and another set of opposite displacement screws to rotate outward by θ2 turns. Then the forces on the split loading platform in the two directions are θ1bAE / lπ and θ2bAE / lπ, respectively. The angle between the resultant force direction and the θ1bAE / lπ direction is arctan(θ2 / θ1), where l is the side length of the split loading platform, A is the cross-sectional area of ​​the split loading platform, E is the elastic modulus of the split loading platform, b is the pitch of the displacement screw, and π is pi.

[0029] When the b3 split loading platform deforms, it causes the sample on it to deform as well, subjecting it to tensile force in the same direction as the tensile force on the split loading platform.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] 1. This invention provides tension through a horizontally set movable hook and controls the magnitude of the tension through a horizontally set displacement screw. The upper and lower surfaces of the sample are reserved, and after the test platform is placed horizontally, the experimental process of the sample can be directly observed from above.

[0032] 2. In this invention, the rotation of the groove of the displacement screw drives the translation of the hook. The rotation angle of the displacement screw and the displacement of the hook have a multiple relationship. Therefore, by controlling the rotation angle of the displacement screw, the displacement of the hook can be precisely controlled with high sensitivity. During the experiment, tightening the displacement screw can keep the sample under constant force and keep the deformation process stopped, making it easy to transfer the experimental table and the sample to the microscope for observation.

[0033] 3. Because the movable hooks of this invention are designed as isosceles trapezoids (base angle of 45°), when the four hooks are in the initial state (no displacement), the two hypotenuses are attached to each other, leaving a square space in the middle to place the split loading platform. This can maximize the use of the space within the loading platform and provide the maximum hook displacement range and the maximum pulling force range.

[0034] 4. Since the platform base of this invention can be equipped with up to 4 hooks, which provide tension in the x-axis and y-axis directions respectively, the direction and magnitude of the resultant force can be changed by increasing or decreasing the displacement distance of two hooks.

[0035] 5. Because this invention is applicable to small sample sizes, it uses a soft loading platform to transmit tensile force, which can effectively avoid stress concentration affecting the uniform deformation of the material.

[0036] 6. The structural design of the movable hook of the present invention comprehensively considers factors such as the amount of hook movement, the elastic modulus of the test sample, the overall size of the platform, and the transmission effect of the displacement screw and transmission screw, and is suitable for observing the tensile deformation of two-dimensional materials;

[0037] 7. This invention has the advantages of small size, high loading accuracy, and arbitrary stretching direction. It can effectively avoid the problems of current mechanical experimental equipment being too large in size, having too large an increase in loading force, and being difficult to change the stretching direction, making it difficult to conduct research on micron-level two-dimensional material mechanical phenomena and to observe the tensile failure process in real time. Attached Figure Description

[0038] Figure 1 This is a three-dimensional side view of the small-size variable-angle tensile mechanics experimental platform of the present invention.

[0039] Figure 2 This is a top view of the small-size variable-angle tensile mechanics experimental platform of the present invention;

[0040] Figure 3 This is a schematic diagram of the moving hook structure of the small-size variable angle tensile mechanics experimental platform of the present invention. (a) is an overall three-dimensional side view, and (b) is a half-section view from the same perspective.

[0041] Figure 4 This is a schematic diagram of the structure of the small-size variable angle tensile mechanics experimental platform of the present invention after the combination of the moving hook, displacement screw and transmission screw. (a) is an overall three-dimensional side view, and (b) is a half-section view from the same perspective.

[0042] Figure 5 This is a three-dimensional side view of the split loading platform in this invention;

[0043] Figure 6 This is a top view of the present invention before tensioning, after the small-sized variable-angle tensile mechanics experimental platform with the split loading platform has been loaded.

[0044] Figure 7 The image shows the top view after the small-sized variable-angle tensile mechanical experimental platform with the split loading platform installed in this invention has been stretched.

[0045] The attached diagram is labeled as follows: 1-Platform base; 2-Moving hook; 21-Guide rail; 22-Middle section; 23-Hook; 3-Displacement screw; 4-Transmission screw; 5-Separated loading platform. Detailed Implementation

[0046] An embodiment of the present invention will be further described below with reference to the accompanying drawings:

[0047] Example 1

[0048] See Figure 1-7 As shown, the present invention provides a technical solution comprising a platform base 1, a movable hook 2, a displacement screw 3, a transmission screw 4, and a separate loading platform 5;

[0049] The plane containing the upper surface of platform base 1 is the XY plane, and the direction perpendicular to the upper surface of platform base 1 is the Z-axis;

[0050] Each side of the platform base 1 is provided with a smooth groove, and the size of each smooth groove matches each guide rail 21 of the movable hook 2. Each movable hook 2 is axially slidably connected to one side of the platform base 1 through several guide rails 21.

[0051] The movable hook 2 is composed of several guide rails 21, a middle section 22 and hooks 23. The movable hook 2 is machined by CNC machine tool. The platform base 1 is connected to several movable hooks. The platform base 1 is connected to several movable hooks 2.

[0052] Each side of the platform base 1 is connected to a movable hook lock 2. The displacement screw 3 is coaxially mounted on the inside of the movable hook 2 on the platform in a threaded manner. An annular groove is provided at one end of the displacement screw 3. The transmission screw 4 is connected to the middle section 22 of the movable hook 2 in the Z-axis direction in a threaded manner. The end of the transmission screw 4 is placed in the annular groove of the displacement screw 3 and is higher than the bottom of the groove. The split loading platform 5 is a cross-shaped elastic body. The split loading platform 5 has several holes. The size of the holes matches the size of the hook 23 of the movable hook 2, and the hook 23 is connected to the holes.

[0053] The displacement screw 3 is a screw with threads of uniform size or a rod with precise displacement. Near the end of the displacement screw 3, there is an annular groove with a depth of half its radius. The width of the displacement screw 3 is 1.2 times the diameter of the transmission screw 4. The end of the displacement screw 3 is located in the cavity on the middle section 22 of the movable hook 2.

[0054] The transmission screw 4 is threaded to one side of the middle end 22 of the movable hook 2. The end of the transmission screw 4 is in the annular groove of the displacement screw 3 and extends into the displacement screw 3 to one-third of its radius.

[0055] The rotation of the groove of the displacement screw 3 causes the end of the transmission screw 4 to move horizontally, and the transmission screw 4 and the movable hook 2 slide as a whole.

[0056] The movable hook 2 includes a guide rail 21, a middle section 22, and a hook 23. The movable hook 2 is a rigidly connected whole. The middle section 22 has a first hole inside along the rotation direction of the transmission screw, and the first hole is provided with a thread that matches the transmission screw. The movable hook 2 has a second hole along the rotation direction of the displacement screw, and the diameter of the second hole is 1.5 times the diameter of the displacement screw. The middle section 22 and the hook 23 are machined from a single piece of isosceles trapezoidal column. The base angle of the isosceles trapezoidal column is 45°, the top surface is the upper surface of the hook, and the bottom surface is the lower surface of the middle section.

[0057] The split loading platform 5 is a cross-shaped column made of elastic material. The elastic modulus and yield strength of the material of the split loading platform 5 are less than those of the material of the movable hook 2. Each side of the split loading platform 5 is provided with holes, and the hook 23 is connected to the split loading platform 5 through the holes.

[0058] A design method for a small-sized variable-angle tensile mechanics experimental platform includes:

[0059] First, based on the material and size of the experimental sample, a1 determines the maximum tensile force F that needs to be applied to the split loading platform 5;

[0060] Based on the elastic modulus E of the split loading platform 5, the normal strain of the platform when the tensile force F is applied is ε = F / AE, where A is the cross-sectional area of ​​the split loading platform 5, and the normal displacement of the platform is x = lε, where l is the side length of the split loading platform.

[0061] When two hooks are attached, if the displacement of both hooks is half of the normal displacement of the platform, then when the split loading platform 5 is subjected to a tensile force F, the displacement of each hook is s = lF / 2AE.

[0062] According to geometric relationships, L = 2s + a2 = 2s + 2h + a1, where L is the inner side length of platform base 1, and h, a1, and a2 are the height, lower base, and upper base of the trapezoidal shape on the upper and lower surfaces of the middle section 22, respectively.

[0063] According to the experimental requirements, the guide rail 21 should satisfy: s0>s, where s0 is the maximum sliding distance of a hook and s is the displacement of this hook at this time; the length of the displacement screw 3 should satisfy: after installation, the first end should leave a sufficient distance outside the platform base 1 to control the number of rotations;

[0064] According to the experimental requirements, the rotation angle θ of the displacement screw and the translational displacement s of the hook have the following relationship: s = θb / 2π, where b is the pitch of the displacement screw, s is the displacement of this hook at this time, and π is pi; furthermore, when the tension F is applied, the rotation angle θ of the displacement screw is θ = lFπ / bAE, where l is the side length of the split loading platform 5, A is the cross-sectional area of ​​the split loading platform 5, and E is the elastic modulus of the split loading platform 5.

[0065] A working method for a small-sized variable-angle tensile mechanics experimental platform includes:

[0066] b1 fixes the experimental sample on the split loading platform 5, so that the experimental sample deforms synchronously;

[0067] During unidirectional tensioning, only two opposite sides of the split loading platform 5 are connected to the movable hook 2, displacement screw 3, and transmission screw 4. Rotating the displacement screw 3 outward causes the groove of the displacement screw 3 to move the end of the transmission screw 4 outward. Since the transmission screw 4 and the movable hook 2 are rigidly connected, and the contact surface between the movable hook 2 and the platform base 1 is smooth with low friction, the movable hook 2 also moves synchronously, causing it to move outward and providing unidirectional tension. When the rotation angle θ of both displacement screws 3 is θ = lFπ / bAE, the tension applied to the split loading platform 5 is F, where l is the side length of the split loading platform 5, and A is the cross-sectional area of ​​the split loading platform 5. The cross-sectional area is E, the elastic modulus of the split loading platform 5 is b, the pitch of the displacement screw is b, and π is pi. When the variable angle tension is applied, the split loading platform 5 is connected to four movable hooks 2, which control two opposite displacement screws 3 to rotate outward by an angle θ1, and another set of opposite displacement screws 3 to rotate outward by θ2 turns. Then the forces on the split loading platform 5 in the two directions are θ1bAE / lπ and θ2bAE / lπ, respectively. The angle between the resultant force direction and the θ1bAE / lπ direction is arctan(θ2 / θ1), where l is the side length of the split loading platform 5, A is the cross-sectional area of ​​the split loading platform 5, E is the elastic modulus of the split loading platform 5, b is the pitch of the displacement screw, and π is pi.

[0068] When the b3 separate loading platform 5 deforms, it causes the sample on it to deform as well, so that it is subjected to tensile force, the direction of which is the same as the tensile force subjected to the separate loading platform 5.

[0069] When a tensile force is applied by rotating the displacement screw 3, the sample is subjected to tensile stress. If the rotation of the displacement screw 3 is stopped, the stress on the sample will remain constant, and its deformation will remain in a certain state. Since the sample is placed in the middle of the small-sized variable-angle tensile mechanics experimental platform 5 with no obstructions above or below, the sample can be observed using instruments such as microscopes when the tensile force is kept constant. Moreover, the experimental platform is small in size, and the entire experimental platform can even be placed inside the scanning electron microscope chamber to observe the real-time deformation of the sample.

Claims

1. A small-sized variable-angle tensile mechanics experimental platform, comprising a platform base (1), characterized in that: The platform base (1) is connected to a movable hook (2), a displacement screw (3), a transmission screw (4), and a separate loading platform (5); The plane on the upper surface of the platform base (1) is the XY plane, and the direction perpendicular to the upper surface of the platform base (1) is the Z axis; Each side of the platform base (1) is provided with a smooth groove, the size of each smooth groove is matched with each guide rail (21) of the movable hook (2), and each movable hook (2) is axially slidably connected to one side of the platform base (1) through several guide rails (21); The movable hook (2) is composed of several guide rails (21), a middle section (22) and a hook (23). The movable hook (2) is integrally processed by a CNC machine tool. The platform base (1) is connected to several movable hooks. The movable hook (2) connected to the platform base (1) is provided with several. Each side of the platform base (1) is connected to a movable hook (2). The displacement screw (3) is coaxially mounted on the inside of the movable hook (2) on the platform in a threaded manner. An annular groove is provided at one end of the displacement screw (3). The transmission screw (4) is connected to the middle section (22) of the movable hook (2) in the Z-axis direction in a threaded manner. The end of the transmission screw (4) is placed in the annular groove of the displacement screw (3) and is higher than the bottom of the groove. The split loading platform (5) is a cross-shaped elastic body. The split loading platform (5) has several holes. The size of the holes matches the size of the hook (23) of the movable hook (2), and the hook (23) is connected to the holes. The working method of the small-size variable-angle tensile mechanical experimental platform is as follows: b1 Fix the experimental sample on the split loading platform (5) so that the experimental sample deforms synchronously; When b2 is subjected to unidirectional tension, only two opposite sides of the split loading platform (5) are connected to the movable hook (2), displacement screw (3), and transmission screw (4). Then, the displacement screw (3) is rotated outward. The groove of the displacement screw (3) will drive the end of the transmission screw (4) to translate outward. Since the transmission screw (4) and the movable hook (2) are rigidly connected, and the contact surface between the movable hook (2) and the platform base (1) is smooth with low friction, the movable hook (2) also translates synchronously, causing the hook to move outward and providing unidirectional tension. When the rotation angle of the two displacement screws (3) is... All for At that time, the tension applied to the split loading platform (5) is F, where Let A be the side length of the split loading platform (5), A be the cross-sectional area of ​​the split loading platform (5), E be the elastic modulus of the split loading platform (5), b be the pitch of the displacement screw, and π be pi. When performing variable angle stretching, the split loading platform (5) is connected to four movable hooks (2), controlling the two opposite displacement screws (3) to rotate outward by an angle. The other set of opposing displacement screws (3) all rotate outwards. In the case of a ring, the forces acting on the two directions of the split loading platform (5) are respectively... The direction of the resultant force is the same as The included angle of direction is ,in Let A be the side length of the split loading platform (5), A be the cross-sectional area of ​​the split loading platform (5), E be the elastic modulus of the split loading platform (5), b be the pitch of the displacement screw, and π be pi. When the b3 split loading platform (5) deforms, it causes the sample on it to deform together, so that it is subjected to tensile force, the direction of which is the same as the tensile force subjected to the split loading platform (5).

2. The small-size variable-angle tensile mechanics experimental platform according to claim 1, characterized in that: The displacement screw (3) is a screw with a consistent thread size or a rod with a precise displacement amount; the displacement screw (3) has an annular groove with a depth of half its radius near its end; the width of the displacement screw (3) is 1.2 times the diameter of the transmission screw (4); and the end of the displacement screw (3) is located in the cavity on the middle section (22) of the movable hook (2).

3. The small-size variable-angle tensile mechanics experimental platform according to claim 1, characterized in that: The transmission screw (4) is threaded to one side of the middle section (22) of the movable hook (2). The end of the transmission screw (4) is in the annular groove of the displacement screw (3) and extends into the displacement screw (3) to one-third of its radius.

4. The small-size variable-angle tensile mechanics experimental platform according to claim 3, characterized in that: The groove of the displacement screw (3) rotates, causing the end of the transmission screw (4) to move horizontally, and the transmission screw (4) and the moving hook (2) slide as a whole.

5. The small-size variable-angle tensile mechanics experimental platform according to claim 1, characterized in that: The movable hook (2) includes a guide rail (21), a middle section (22) and a hook (23). The movable hook (2) is a rigidly connected whole. The middle section (22) has a first hole inside along the rotation direction of the transmission screw, and the first hole is provided with a thread that matches the transmission screw. The movable hook (2) has a second hole along the rotation direction of the displacement screw, and the diameter of the second hole is 1.5 times the diameter of the displacement screw. The middle section (22) and the hook (23) are processed from a single piece of isosceles trapezoidal column. The base angle of the isosceles trapezoidal column is 45°, the top surface is the upper surface of the hook, and the bottom surface is the lower surface of the middle section.

6. The small-size variable-angle tensile mechanics experimental platform according to claim 1, characterized in that: The split loading platform (5) is a cross-shaped column made of elastic material. The elastic modulus and yield strength of the material of the split loading platform (5) are less than the elastic modulus and yield strength of the material of the movable hook (2). Each side of the split loading platform (5) is provided with holes, and the hook (23) is connected to the split loading platform (5) through the holes.

7. A design method for a small-size variable-angle tensile mechanical experimental platform according to any one of claims 1-6, characterized in that, The design method is as follows: First, based on the material and size of the experimental sample, the maximum tensile force F that needs to be applied to the split loading platform (5) is determined; Based on the elastic modulus E of the split loading platform (5), the normal strain of the platform when the tensile force F is applied is: Where A is the cross-sectional area of ​​the split loading platform (5), and the normal displacement of the platform is... ,in The side length of the split loading platform; When two hooks are attached, if the displacement of both hooks is half of the platform's normal displacement, then when the split loading platform (5) is subjected to a tensile force F, the displacement of each hook is... ; a4 is based on geometric relationships, , where L is the inner side length of the platform base (1), and h, a1, a2 are the height, lower base, and upper base of the trapezoids on the upper and lower surfaces of the middle section (22), respectively; According to the experimental requirements, the guide rail (21) should satisfy: s0>s, where s0 is the maximum sliding distance of a hook and s is the displacement of this hook at this time; the length of the displacement screw (3) should satisfy: after installation, the first end should have enough distance outside the platform base (1) to control the number of rotations; According to the experimental requirements, the rotation angle of the displacement screw is... Translational displacement of the hook It has the following relationship: Where b is the pitch of the displacement screw, and s is the displacement of this hook at this moment. Pi; further, when a tension F is applied, the rotation angle of the displacement screw... for , Let A be the side length of the split loading platform (5), A be the cross-sectional area of ​​the split loading platform (5), and E be the elastic modulus of the split loading platform (5).

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