Clamping device suitable for testing tensile property or tensile-tensile low-cycle fatigue property of linear material
By designing an upper and lower clamping device with gradually varying tooth thickness, stress concentration at the wire clamping end is alleviated, enabling stable clamping and accurate testing of high-strength wires. This solves the problems of unstable clamping and low precision in traditional testing, ensuring the reliability and efficiency of test results.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- INST OF METAL RESEARCH - CHINESE ACAD OF SCI
- Filing Date
- 2025-05-30
- Publication Date
- 2026-04-28
AI Technical Summary
Traditional tensile property testing and tension-tension low-cycle fatigue property testing of wire materials suffer from problems such as unstable clamping, low testing accuracy, and clamping end breakage. Especially for high-strength wires, the general-purpose fixture design leads to stress concentration, making accurate testing impossible.
A clamping device including an upper clamp and a lower clamp is designed. The toothed base plate has teeth of different thicknesses along the height direction. The tooth thickness at the clamping end gradually decreases. The stress concentration is relieved by the swing of the teeth, and the device is fixed to the fixing rod by a locking nut to ensure stable clamping of the sample during fatigue or tensile process.
It achieves stable clamping of linear materials, ensuring the stability of load distribution. The maximum stress occurs in the parallel section of the sample, ensuring the accuracy and validity of the test results. At the same time, it is easy to operate, low in cost, and has good robustness, making it suitable for testing high-strength wires.
Smart Images
Figure CN224176246U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the field of mechanical property testing technology of metallic materials, specifically a clamping device suitable for testing the tensile properties or tensile-tensile low-cycle fatigue properties of linear materials. Background Technology
[0002] In fields such as construction, transportation, and power, there are numerous linear materials, such as the main cables of cable-stayed bridges and suspension bridges, and the reinforcing cores of electric wires and cables. Their tensile and fatigue properties are often important indicators that need to be evaluated. Tensile tests can determine a series of strength and plasticity indicators of materials, while fatigue tests can reflect the performance changes of materials under cyclic loading. These experiments provide important basis for material selection, design, and optimization. However, traditional tensile property testing and tensile-tensile low-cycle fatigue performance testing of linear materials have many problems, such as unstable clamping, low testing accuracy, and specimen clamping end breakage. These problems lead to inaccurate test results or even make the test impossible to complete.
[0003] Currently, most common testing methods for tensile or tension-tensile low-cycle fatigue properties of wire materials are designed for low-strength wires. During testing, the wire is wound around a fixture or base. However, for high-strength wires, it's impossible to wound the wire during testing, and general-purpose fixtures are typically used to hold it. Due to design flaws in these fixtures, stress concentration often occurs at the clamping end, causing the wire to break and rendering the test data invalid.
[0004] Therefore, developing a convenient, stable, and high-precision clamping device for testing the tensile or tension-tension low-cycle fatigue properties of wire materials is of great significance, especially for the accurate testing of high-strength wires. The promotion and application of this device and method will help advance wire science research and provide strong support for related high-end equipment applications. Utility Model Content
[0005] To address the problem of wire failure at the clamping end due to unreasonable design in existing tensile or tension-tension low-cycle fatigue performance tests for linear materials, the purpose of this invention is to provide a clamping device suitable for tensile or tension-tension low-cycle fatigue performance tests of linear materials, so as to meet the requirements of effective, accurate and efficient tensile or tension-tension low-cycle fatigue performance tests for linear materials.
[0006] The objective of this utility model is achieved through the following technical solution:
[0007] This utility model includes an upper clamp and a lower clamp located below the upper clamp, both mounted on a testing machine. The upper and lower clamps have the same structure and are mirror images of each other. Both the upper and lower clamps include toothed base plates and fixing rods. Each toothed base plate consists of two opposing toothed base plates. The upper end of the sample is clamped by the two toothed base plates in the upper clamp, and the lower end of the sample is clamped by the two toothed base plates in the lower clamp. One end of each toothed base plate is a clamping end for holding the sample, and the other end is a fixing end for fixing to the testing machine. The clamping end has teeth of different thicknesses along its height. The upper end of the sample is clamped by the thickest teeth of the two toothed base plates in the upper clamp, and the lower end of the sample is clamped by the thickest teeth of the two toothed base plates in the lower clamp. The toothed base plates are provided with fixing rods for fixing to the testing machine.
[0008] Wherein: the tooth thickness of the two toothed bottom plates in the upper clamp gradually decreases from top to bottom, and the tooth thickness of the two toothed bottom plates in the lower clamp gradually decreases from bottom to top.
[0009] The teeth of the two toothed base plates in the upper fixture (excluding the thickest tooth) and the teeth of the two toothed base plates in the lower fixture (excluding the thickest tooth) swing with the stretching of the sample during the test, thereby alleviating the stress concentration at the clamping part of the sample by the toothed base plates.
[0010] The spacing between adjacent teeth at the clamping end is equal.
[0011] A locking nut is threaded onto the toothed base plate, and the fixing rod is located between the locking nut and the toothed base plate. The fixing rod is fixed to the toothed base plate by screwing the locking nut.
[0012] The width of the toothed base plate clamping end is smaller than the width of the fixed end. One side or the front and rear sides of the clamping end are respectively provided with locking nuts threaded to the fixed end. The locking nuts clamp the upper and lower fixing rods between the fixed end and the fixed end.
[0013] The fixed end of the toothed base plate of the upper clamp has an outward-facing side consisting of inclined plane A, inclined plane B, and plane A from top to bottom. Inclined plane A slopes outward from top to bottom, inclined plane B slopes inward from top to bottom, and plane A is a vertical plane. The upper clamp is engaged with the testing machine through inclined planes A and B for upper and lower limit positioning.
[0014] The fixed end of the toothed base plate in the lower clamp has an outward-facing side consisting of inclined plane D, inclined plane C, and plane B from bottom to top. Inclined plane D slopes outward from bottom to top, inclined plane C slopes inward from bottom to top, and plane B is a vertical plane. The lower clamp is engaged with the testing machine through inclined plane C and inclined plane D for upper and lower limit positioning.
[0015] The upper end face of the sample is located between the two thickest teeth of the two toothed base plates in the upper fixture, and the lower end face of the sample is located between the two thickest teeth of the two toothed base plates in the lower fixture.
[0016] The advantages and positive effects of this utility model are as follows:
[0017] 1. This utility model can provide stable clamping for linear materials, ensuring stable load distribution of the sample during fatigue testing, and the maximum stress position of the sample occurs in the parallel section of the sample, thus ensuring the accuracy and effectiveness of the test results.
[0018] 2. This utility model has a simple design and uses wire-cut metal plates, which can be reused multiple times, reducing costs.
[0019] 3. This utility model is easy to operate and has good robustness. Even if the experiment is unexpectedly stopped, the clamping state of the sample is not affected, and the experiment can be restarted directly, thus ensuring testing efficiency. Attached Figure Description
[0020] Figure 1 This is a schematic diagram of the overall structure of this utility model;
[0021] Figure 2 This is a schematic diagram of the structure of the toothed base plate of the upper clamp and the upper clamp fixing rod or the toothed base plate of the lower clamp and the lower clamp fixing rod of this utility model.
[0022] Figure 3 This is a schematic diagram of the structure of the two toothed base plates of the upper clamp of this utility model clamping the upper end of the sample;
[0023] Figure 4 for Figure 3 A magnified view of a section at point A in the middle;
[0024] Figure 5 for Figure 3 A magnified view of a section at point B in the middle;
[0025] Figure 6 This is a schematic diagram of the structure of this utility model installed on a fatigue testing machine or a tensile testing machine;
[0026] Figure 7 Load and displacement diagrams during fatigue testing of linear material specimens using this invention;
[0027] Figure 8 A diagram showing the state of a linear material specimen after fatigue testing using this invention.
[0028] Figure 9 The stress-life relationship diagram obtained by using this invention to perform fatigue testing on a linear material sample;
[0029] Wherein: 1 is the upper clamp, 101 is the toothed base plate of the upper clamp, 102 is the fixing rod of the upper clamp, 103 is the locking nut of the upper clamp, 104 is the inclined plane A, 105 is the inclined plane B, and 106 is the plane A;
[0030] 2 is the lower clamp, 201 is the toothed base plate of the lower clamp, 202 is the fixing rod of the lower clamp, 203 is the locking nut of the lower clamp, 204 is plane B, 205 is inclined plane C, and 206 is inclined plane D.
[0031] 3 is the sample, 4 is the baffle, 5 is the push rod, and 6 is the spring. Detailed Implementation
[0032] The present invention will now be described in further detail with reference to the accompanying drawings.
[0033] like Figures 1-5 As shown, this utility model includes an upper clamp 1 and a lower clamp 2 located below the upper clamp 1, which are respectively installed on a fatigue testing machine or a tensile testing machine. The upper clamp 1 and the lower clamp 2 have the same structure and are mirror images of each other. Both the upper clamp 1 and the lower clamp 2 include toothed base plates and fixing rods. There are two toothed base plates in the upper clamp 1 and the lower clamp 2, which are opposite each other. The upper end of the sample 3 is clamped by the two toothed base plates in the upper clamp 1, and the lower end of the sample 3 is clamped by the two toothed base plates in the lower clamp 2. One end of each toothed base plate is a clamping end for clamping the sample, and the other end is a fixing end for fixing to the testing machine. The clamping end has teeth of different thicknesses along the height direction. The upper end of the sample 3 is clamped by the thickest teeth of the two toothed base plates in the upper clamp 1, and the lower end of the sample 3 is clamped by the thickest teeth of the two toothed base plates in the lower clamp 2. The toothed base plates are provided with fixing rods 102 for fixing to the testing machine.
[0034] In this embodiment, the upper clamp 1 has two upper clamp toothed base plates 101 arranged on the left and right, two upper clamp locking nuts 103, and four upper clamp fixing rods 102. The width of the clamping end of the upper clamp toothed base plate 101 is smaller than the width of the fixing end, that is, the top surface of the upper clamp toothed base plate 101 is "T" shaped. Upper clamp locking nuts 103 are threaded to the fixing end on one side or both sides of the clamping end in the width direction. In this embodiment, an upper clamp locking nut 103 threaded to the fixing end is located on the front side of the clamping end of the upper clamp toothed base plate 101 in the width direction. The upper clamp locking nut 103 clamps the upper and lower upper clamp fixing rods 102 between itself and the fixing end. The upper clamp fixing rods 102 are fixed to the upper clamp toothed base plate 101 by tightening the upper clamp locking nut 103. The tooth thickness of the upper clamp toothed base plate 101 gradually decreases from top to bottom, and the spacing between adjacent teeth at the clamping end is equal. Except for the thickest tooth, the other teeth of the toothed base plate 101 of the upper clamp swing with the stretching of the specimen 3 during the test, which is used to relieve stress concentration at the upper end of the specimen 3 held by the toothed base plate 101 of the upper clamp during the tensile test.
[0035] In the upper clamp 1 of this embodiment, the fixed end of the toothed base plate 101 of the upper clamp, facing outward, consists of inclined surface A104, inclined surface B105, and plane A106 from top to bottom. Inclined surface A104 slopes outward from top to bottom, inclined surface B105 slopes inward from top to bottom, and plane A106 is a vertical plane. The upper clamp 1 is engaged with the base of the fatigue testing machine or tensile testing machine through inclined surfaces A104 and B105 for upper and lower limit positioning.
[0036] In this embodiment, the lower clamp 2 has two lower clamp toothed base plates 201 arranged on the left and right, two lower clamp locking nuts 203, and four lower clamp fixing rods 202. The width of the clamping end of the lower clamp toothed base plate 201 is smaller than the width of the fixed end, that is, the bottom surface of the lower clamp toothed base plate 201 is "T" shaped. A lower clamp locking nut 203 threaded to the fixed end is provided on one side or both sides of the clamping end in the width direction. In this embodiment, a lower clamp locking nut 203 threaded to the fixed end is provided on the front side of the clamping end of the lower clamp toothed base plate 201 in the width direction. The lower clamp locking nut 203 clamps the upper and lower lower clamp fixing rods 202 between itself and the fixed end. The lower clamp fixing rods 202 are fixed to the lower clamp toothed base plate 201 by tightening the lower clamp locking nut 203. The tooth thickness of the clamping end of the lower clamp toothed base plate 201 gradually decreases from bottom to top, and the spacing between adjacent teeth at the clamping end is equal. Except for the thickest tooth, the other teeth of the toothed bottom plate 201 of the lower clamp swing with the stretching of the specimen 3 during the test, which is used to relieve stress concentration at the lower end of the specimen 3 held by the toothed bottom plate 201 of the lower clamp during the fatigue or tensile test.
[0037] In this embodiment, the lower clamp 2 has three sides on its fixed end facing outwards: inclined plane D206, inclined plane C205, and plane B204, from bottom to top. Inclined plane D206 slopes outwards from bottom to top, inclined plane C205 slopes inwards from bottom to top, and plane B204 is a vertical plane. The lower clamp 2 engages with the base of the fatigue testing machine or tensile testing machine via inclined plane C205 and inclined plane D206 for upper and lower positioning.
[0038] The upper end face of the sample 3 is located between the two thickest teeth of the clamping ends of the two upper clamp toothed base plates 101 in the clamp 1, and the lower end face of the sample 3 is located between the two thickest teeth of the clamping ends of the two lower clamp toothed base plates 201 in the lower clamp 2.
[0039] During installation, assemble the upper clamp 1 and the lower clamp 2, tighten the upper clamp locking nut 103, and fix the upper clamp fixing rod 102 to the upper clamp toothed base plate 101; tighten the lower clamp locking nut 203, and fix the lower clamp fixing rod 202 to the lower clamp toothed base plate 201. Then, the upper clamp 1 is fixed to the upper base of the fatigue testing machine or tensile testing machine via the upper clamp fixing rod 102, and the lower clamp 2 is fixed to the lower base of the fatigue testing machine or tensile testing machine via the lower clamp fixing rod 202. The specific fixing method is the existing technology. For example, baffles 4 can be set on both the front and rear sides of the fixing position of the upper and lower bases. The upper clamp 1 or the lower clamp 2 is placed in the baffles 4 on the front and rear sides. The inclined surfaces A104 and B105 on the upper clamp 1 abut against the corresponding inclined surfaces on the upper base, and the inclined surfaces C205 and D206 on the lower clamp 2 abut against the corresponding inclined surfaces on the lower base. The upper clamp 1 and the lower clamp 2 are fixed by the top rod 5 set on the baffle 4. In addition, the upper clamp fixing rod 102 is connected to the upper base and the lower clamp fixing rod 202 is connected to the lower base by the spring 6 to prevent the upper clamp 1 and the lower clamp 2 from loosening during the test.
[0040] The specimen 3 is placed vertically between the two toothed base plates 201 of the lower clamp 2, with the lower end face of the specimen 3 positioned between the two lowest teeth with the thickest tooth thickness on the two lower clamp toothed base plates 201. The lower clamp 2 is then clamped using a fatigue testing machine or a tensile testing machine. The lower base is moved so that the upper end face of the specimen 3 is positioned between the two highest teeth with the thickest tooth thickness on the two upper clamp toothed base plates 101. The upper clamp 1 is then clamped using a fatigue testing machine or a tensile testing machine to ensure that the specimen 3 is positioned between the upper clamp 1 and the lower clamp 2, thus ensuring the accuracy of the experimental structure. Tensile or tension-tension low-cycle fatigue testing is then initiated. During the test, the portion of the specimen 3 closest to its upper and lower ends is clamped by the two teeth with the thickest tooth thickness. The other teeth oscillate with the tension of the specimen 3 during the test, alleviating stress concentration at the clamped portions of the specimen 3.
[0041] Experimental Example
[0042] Taking the tensile-low cycle fatigue performance test of φ2.5mm pearlitic ultra-high strength steel wire as an example. The upper clamp toothed base plate 101 and the lower clamp toothed base plate 201 used are made by wire cutting of quenched Cr12MoV, with a hardness of 60HRC; the upper clamp fixing rod 102 and the lower clamp fixing rod 202 are M2.5 screws, which are fixed by the upper clamp locking nut 103 and the lower clamp locking nut 203 respectively; the distance between the two upper clamp toothed base plates 101 of the upper clamp 1 before clamping is 5mm, and the distance between the two lower clamp toothed base plates 201 of the lower clamp 2 before clamping is 5mm.
[0043] The maximum fatigue load of pearlitic ultra-high strength steel wire is approximately 12 kN at a frequency of 1 Hz, and the stress ratio of the fatigue load is 0.1, 10. 3 At the end of the cycle, the forces on each level of teeth on the upper clamp toothed base plate 101 and the lower clamp toothed base plate 201 are shown in Table 1. The resultant force on each level of teeth is approximately 12kN.
[0044] Table 1
[0045] series Tooth width (mm) Tooth height (mm) Tooth thickness (mm) The tooth experiences a force (N). 1 20 16 13.00 3600 2 20 16 9.85 2520 3 20 16 7.33 1764 4 20 16 5.98 1234.80 5 20 16 5.06 864.36 6 20 16 4.36 605.05 7 20 16 3.79 423.54 8 20 16 3.32 296.48 9 20 16 2.93 207.53 10 20 16 2.58 145.27 11 20 16 2.28 101.69 12 20 16 2.02 71.18 13 20 16 1.79 49.83 14 20 16 1.59 34.88 15 20 16 1.41 24.42 16 20 16 1.25 17.09
[0046] Install the upper clamp 1 and lower clamp 2 onto the base of the fatigue testing machine or tensile testing machine as described above. Figure 6 As shown.
[0047] The effectiveness of fatigue testing is mainly reflected in the fracture location being within the parallel segment, with higher accuracy occurring closer to the middle of the parallel segment. Stability is primarily reflected in the stability during load cycles. Stable cyclic loading is a necessary condition for ensuring accurate test results. The stability of the sample is manifested in its stable strain response under cyclic loading, which can be characterized by displacement. The load and displacement during the loading process are as follows... Figure 7 As shown, the load and displacement remain stable.
[0048] After fatigue testing, the condition of the specimen is as follows: Figure 8 As shown, the stress-life relationship obtained from fatigue testing is as follows: Figure 9 As shown, this can be used to evaluate the fatigue strength of materials. In this experimental example, the conditional life fatigue strength of the material at 1000 cycles is approximately 2070 MPa.
[0049] This invention can effectively conduct tensile or tension-tension low-cycle fatigue tests on linear materials to obtain accurate data on the tensile properties or tension-tension low-cycle fatigue properties of linear materials.
[0050] The above description is merely an embodiment of this utility model and is not intended to limit the scope of protection of this utility model. Any modifications, equivalent substitutions, improvements, extensions, etc., made within the spirit and principles of this utility model are included within the scope of protection of this utility model.
Claims
1. A gripping device suitable for tensile or tensile-tensile low cycle fatigue testing of linear materials, characterized in that: The test machine includes an upper clamp (1) mounted on the testing machine and a lower clamp (2) located below the upper clamp (1). The upper clamp (1) and the lower clamp (2) have the same structure and are mirror images of each other. Both the upper clamp (1) and the lower clamp (2) include toothed base plates and fixing rods. The toothed base plates in the upper clamp (1) and the lower clamp (2) are two opposite each other. The upper end of the sample (3) is clamped by the two toothed base plates in the upper clamp (1), and the lower end of the sample (3) is clamped by the lower clamp (1). The sample (3) is held by two toothed base plates in the upper clamp (1). One end of each toothed base plate is a clamping end for holding the sample, and the other end is a fixing end for fixing to the testing machine. The clamping end is provided with teeth of different thicknesses along the height direction. The upper end of the sample (3) is held by the thickest tooth of the two toothed base plates in the upper clamp (1), and the lower end of the sample (3) is held by the thickest tooth of the two toothed base plates in the lower clamp (2). The toothed base plates are provided with fixing rods (102) for fixing to the testing machine.
2. The clamping device for tensile testing or tensile-tensile low cycle fatigue testing of linear materials according to claim 1, characterized in that: The tooth thickness of the two toothed bottom plates in the upper clamp (1) gradually decreases from top to bottom, and the tooth thickness of the two toothed bottom plates in the lower clamp (2) gradually decreases from bottom to top.
3. The clamping device for testing the tensile properties or tensile-tensile low-cycle fatigue properties of linear materials according to claim 1, characterized in that: The teeth of the two toothed bottom plates in the upper clamp (1), excluding the thickest tooth, and the teeth of the two toothed bottom plates in the lower clamp (2), excluding the thickest tooth, swing with the stretching of the sample (3) during the test, thereby alleviating the stress concentration of the sample (3) held by the toothed bottom plates.
4. The clamping device for testing the tensile properties or tensile-tensile low-cycle fatigue properties of linear materials according to claim 1, characterized in that: The spacing between adjacent teeth at the clamping end is equal.
5. The clamping device for testing the tensile properties or tensile-tensile low-cycle fatigue properties of linear materials according to claim 1, characterized in that: A locking nut is threaded onto the toothed base plate, and the fixing rod is located between the locking nut and the toothed base plate. The fixing rod is fixed to the toothed base plate by screwing the locking nut.
6. The clamping device for testing the tensile properties or tensile-tensile low-cycle fatigue properties of linear materials according to claim 5, characterized in that: The width of the toothed base plate clamping end is smaller than the width of the fixed end. One side or the front and rear sides of the clamping end are respectively provided with locking nuts threaded to the fixed end. The locking nuts clamp the upper and lower fixing rods between the fixed end and the fixed end.
7. The clamping device for testing the tensile properties or tensile-tensile low-cycle fatigue properties of linear materials according to claim 1, characterized in that: The fixed end of the toothed base plate of the upper clamp (1) has an outward-facing side with inclined surface A (104), inclined surface B (105) and plane A (106) from top to bottom. Inclined surface A (104) is inclined outward from top to bottom, inclined surface B (105) is inclined inward from top to bottom, and plane A (106) is a vertical plane. The upper clamp (1) is engaged with the testing machine through inclined surface A (104) and inclined surface B (105) for upper and lower limit positioning.
8. The clamping device for testing the tensile properties or tensile-tensile low-cycle fatigue properties of linear materials according to claim 1, characterized in that: The fixed end of the toothed base plate of the lower clamp (2) has an outward-facing side with inclined surface D (206), inclined surface C (205), and plane B (204) from bottom to top. The inclined surface D (206) is inclined outward from bottom to top, the inclined surface C (205) is inclined inward from bottom to top, and the plane B (204) is a vertical plane. The lower clamp (2) is engaged with the testing machine through the inclined surface C (205) and the inclined surface D (206) for upper and lower limit positioning.
9. The clamping device for testing the tensile properties or tensile-tensile low-cycle fatigue properties of linear materials according to claim 1, characterized in that: The upper end face of the sample (3) is located between the two thickest teeth of the two toothed bottom plates in the upper clamp (1), and the lower end face of the sample (3) is located between the two thickest teeth of the two toothed bottom plates in the lower clamp (2).