Pipe clamp assembly for pipe tensile test
The inner and outer wedge clamping structure solves the clamping problem of hard and brittle thin-walled tubes in tensile tests, achieving stable clamping and accurate testing.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- 张凯杰
- Filing Date
- 2026-01-20
- Publication Date
- 2026-04-10
AI Technical Summary
Existing technologies are difficult to effectively clamp hard and brittle thin-walled tubes, especially molybdenum tubes, which leads to easy crushing, slippage and clamping deformation during tensile tests, affecting the accuracy of the test.
It adopts two independent sets of threaded drive wedge structures, inner and outer, and forms a stable two-way clamping by combining the inner wedge clamp and the outer wedge clamp. The anti-slip teeth enhance the friction and independently control the inner and outer clamping forces.
It achieves non-destructive and stable clamping of hard and brittle thin-walled pipes, adapts to pipe diameter tolerances, prevents deformation and slippage, and ensures the accuracy of tensile tests.
Smart Images
Figure CN121830241A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of mechanical property testing equipment, specifically to a pipe clamp assembly for pipe tensile testing, which is particularly suitable for testing the tensile properties of welded joints of refractory metal pipes such as molybdenum pipes. Background Technology
[0002] Tensile mechanical property testing of metal pipes is an important means of evaluating material properties and the quality of welded joints. In the fields of nuclear energy, aerospace, and high-temperature industries, molybdenum (Mo) and its alloys are often used to make thin-walled pipes due to their excellent high-temperature strength and corrosion resistance. For such refractory metal pipes, especially welded pipe samples, the accuracy of their tensile test data is directly related to the safety and reliability of the structural design.
[0003] However, in existing tensile testing techniques, effective clamping of hard and brittle thin-walled tubes remains a technical challenge, mainly due to the following issues:
[0004] First, traditional universal testing machines are typically equipped with planar wedge clamps or V-clamps. These clamps generate enormous lateral (radial) clamping forces during operation. For solid bars, this clamping force does not significantly alter the cross-sectional shape of the specimen; however, for hollow, thin-walled tubes, due to their low radial stiffness, the tube ends are prone to severe flattening deformation under the enormous clamping force. For ductile materials, this deformation leads to stress concentration; and for materials like molybdenum tubes, which exhibit significant brittleness and high hardness at room temperature, radial compression often causes the tube to be directly crushed or develop microcracks in the non-gauge section (i.e., the clamping area), resulting in premature fracture of the specimen at the clamping point, rendering the tensile test ineffective, and making it impossible to obtain accurate tensile strength and elongation data.
[0005] Secondly, to prevent the pipe from being crushed, the existing conventional solution is to insert a solid metal cylinder (mandrel) inside the pipe as a support. While this method can prevent pipe wall collapse to some extent, it has significant limitations: First, the inner diameter of the pipe usually has manufacturing tolerances. If the mandrel diameter is too large, it is difficult to insert; if the diameter is too small, there will be a gap between the pipe wall and the mandrel, and the pipe will still deform in the initial clamping stage. Second, the solid mandrel only plays a passive supporting role and cannot actively apply frictional force to the inner wall of the pipe. The tensile load depends entirely on the frictional transmission between the outer wall of the pipe and the external clamp. For molybdenum pipes with high surface hardness and low coefficient of friction, a larger external clamping force is often required to prevent slippage, which actually increases the risk of crushing.
[0006] Furthermore, some existing specialized pipe clamps are complex in structure and bulky, often requiring hydraulic drive or complex tooling for installation, making operation cumbersome and difficult to finely adjust the clamping force. During welded joint testing, unstable clamping or slippage can easily cause non-axial torsional forces on the weld, affecting the assessment of its true mechanical properties.
[0007] Therefore, there is an urgent need to develop a pipe clamp assembly that is compact, easy to operate, adaptable to pipe diameter tolerances, and actively and steadily clamps the inner and outer walls of the pipe in both directions, in order to solve the technical problems of easy crushing, slippage and clamping deformation of hard and brittle thin-walled pipes in tensile tests. Summary of the Invention
[0008] The purpose of this invention is to provide a pipe clamp assembly for pipe tensile testing, which achieves non-destructive and stable clamping of the pipe end through two sets of independent inner and outer threaded drive wedge structures.
[0009] To achieve the above objectives, the present invention adopts the following technical solution:
[0010] A pipe clamp assembly for pipe tensile testing includes a pipe clamp body, a pipe clamp sleeve, a central connecting column, and a bidirectional wedge clamping mechanism.
[0011] The pipe clamp body is used to connect to an external testing machine; the pipe clamp sleeve is fixed to one end of the pipe clamp body through a connecting structure; one end of the central connecting column is fixed to the pipe clamp body, and the other end extends axially into the internal cavity of the pipe clamp sleeve.
[0012] The bidirectional wedge clamping mechanism is located between the pipe clamp sleeve and the central connecting column, and includes an outer wedge clamping block, an inner wedge clamping block, an outer clamping nut, an inner clamping nut, and a wedge stopper.
[0013] The outer wedge-shaped clamp is disposed between the inner side of the pipe clamp sleeve and the outer wall of the pipe to be tested; the outer clamping nut is threadedly connected to the inner wall of the pipe clamp sleeve, and its end abuts against the end of the outer wedge-shaped clamp.
[0014] The wedge-shaped stopper is located at the end of the central connecting column; the inner wedge-shaped clamp is sleeved between the outer side of the wedge-shaped stopper and the inner wall of the pipe to be tested; the inner clamping nut is threaded onto the central connecting column, and its end abuts against the end of the inner wedge-shaped clamp.
[0015] Furthermore, both the outer wedge-shaped clamp and the inner wedge-shaped clamp are split structures, with 3-6 of them, and they are evenly distributed along the circumference.
[0016] Furthermore, the inner wall of the pipe clamp sleeve and the outer wall of the outer wedge-shaped clamp are conical mating structures; the outer wall of the wedge-shaped stopper and the inner wall of the inner wedge-shaped clamp are conical mating structures.
[0017] Furthermore, both the inner wall surface of the outer wedge-shaped clamp and the outer wall surface of the inner wedge-shaped clamp are provided with anti-slip teeth.
[0018] Furthermore, the component also includes a rod clamp body, one end of which is provided with a threaded structure for connecting the rod sample.
[0019] The present invention has the following beneficial technical effects:
[0020] 1. Prevent pipe deformation: The active support of the inner wedge-shaped clamp and the external clamping of the outer wedge-shaped clamp form a two-way force structure, which avoids the hollow thin-walled pipe from being flattened or broken under the action of unidirectional clamping force. It is especially suitable for hard and brittle materials (such as molybdenum pipes).
[0021] 2. High adaptability: Both the inner and outer wedge structures are adjustable, which can adapt to a certain tolerance range of the inner and outer diameter of the pipe. Stable clamping can be achieved by adjusting the nut.
[0022] 3. Stable clamping: The split clamping block design, combined with anti-slip teeth, ensures full contact between the clamping block and the tube wall and provides great friction, effectively preventing the sample from slipping off during the stretching process.
[0023] 4. Independent control: The internal tension and external clamping are controlled by two independent nuts, and the operator can flexibly adjust the magnitude of the internal and external clamping forces according to the sample material and size. Attached Figure Description
[0024] Figure 1 This is a cross-sectional view of the pipe clamp assembly of the present invention.
[0025] The markings in the diagram are as follows: 1-Pipe clamp body; 2-Pipe clamp sleeve; 3-Central connecting column; 4-Outer wedge clamp; 5-Inner wedge clamp; 6-Outer clamping nut; 7-Inner clamping nut; 8-Wedge plug; 9-Pipe clamp connecting ring; 10-External connecting hole; 11-Bar clamp body; 12-Sample tube; 13-Test rod; 14-Weld. Detailed Implementation
[0026] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings.
[0027] like Figure 1 As shown, the present invention provides a pipe clamp assembly for pipe tensile testing, for clamping a specimen welded from a specimen tube 12 (left side, such as a molybdenum tube) and a test rod 13 (right side, such as a molybdenum rod).
[0028] 1. Basic support structure
[0029] The component includes a pipe clamp body 1 with an external connection hole 10. A pipe clamp sleeve 2 is connected to one end of the pipe clamp body 1 via a pipe clamp connecting ring 9. A central connecting post 3 is coaxially disposed in the internal cavity of the pipe clamp sleeve 2, and one end of the central connecting post 3 is fixed to the pipe clamp body 1.
[0030] 2. Bidirectional wedge clamping mechanism
[0031] This mechanism is located between the pipe clamp sleeve 2 and the central connecting column 3, and its specific structure is as follows:
[0032] The outer clamping portion includes an outer wedge-shaped clamping block 4 and an outer clamping nut 6. The outer wedge-shaped clamping blocks 4 are located inside the pipe clamp sleeve 2, numbering 3-6 and evenly distributed circumferentially, with an outer conical surface on their outer wall. The inner wall of the pipe clamp sleeve 2 has an inner conical surface that mates with the outer conical surface. The outer clamping nut 6 is threaded onto the inner wall thread of the pipe clamp sleeve 2, and its end abuts against the end of the outer wedge-shaped clamping block 4.
[0033] The inner clamping part includes an inner wedge-shaped clamping block 5, a wedge-shaped stopper rod 8, and an inner clamping nut 7. The wedge-shaped stopper rod 8 is located at the end of the central connecting post 3 away from the pipe clamp body 1 (i.e., the right end). The inner wedge-shaped clamping blocks 5 are sleeved on the outside of the wedge-shaped stopper rod 8, and there are 3-6 of them, evenly distributed circumferentially. The outer wall of the wedge-shaped stopper rod 8 has an outer conical surface, and the inner wall of the inner wedge-shaped clamping block 5 has an inner conical surface that mates with the outer conical surface. The inner clamping nut 7 is threaded onto the external thread of the central connecting post 3, and the end of the inner clamping nut 7 abuts against the end of the inner wedge-shaped clamping block 5.
[0034] 3. Auxiliary Structure
[0035] The inner wall of the outer wedge-shaped clamp 4 and the outer wall of the inner wedge-shaped clamp 5 are both machined with anti-slip teeth to enhance friction. A rod clamp body 11 is provided on the right side, one end of which is provided with an internal thread groove for connecting the test rod 13.
[0036] Working principle:
[0037] When clamping, insert one end of the sample tube 12 into the gap between the inner and outer wedge-shaped clamps.
[0038] First, manually rotate the inner clamping nut 7 to push the inner wedge-shaped clamp 5 axially. Since the wedge-shaped stopper 8 is fixed in position, the inner wedge-shaped clamp 5 is opened up under the action of the conical surface, resulting in radial expansion, and presses against the inner wall of the sample tube 12 from the inside.
[0039] Subsequently, the outer clamping nut 6 is manually rotated to push the outer wedge-shaped clamp 4 to move axially. Under the action of the inner conical surface of the pipe clamp sleeve 2, the outer wedge-shaped clamp 4 undergoes radial contraction, gripping the outer wall of the sample tube 12 from the outside.
[0040] Through the above operations, the sample tube 12 is firmly clamped by the uniform contraction and expansion of 3-6 split clamping blocks, which not only ensures the friction required for stretching, but also prevents the tube wall from being crushed.
Claims
1. A pipe clamp assembly for tensile testing of pipes, characterized in that, include: Pipe clamp body (1); A pipe clamp sleeve (2) is connected to one end of the pipe clamp body (1); A central connecting post (3) is coaxially disposed inside the pipe clamp sleeve (2), one end of which is fixed to the pipe clamp body (1); and A bidirectional wedge clamping mechanism is provided between the pipe clamp sleeve (2) and the central connecting column (3); The bidirectional wedge clamping mechanism includes an outer wedge clamp (4), an inner wedge clamp (5), an outer clamping nut (6), an inner clamping nut (7), and a wedge stopper (8). The outer wedge-shaped clamp (4) is disposed on the inner side of the pipe clamp sleeve (2); the outer clamp nut (6) is threadedly connected to the inner wall of the pipe clamp sleeve (2), and the end of the outer clamp nut (6) abuts against the end of the outer wedge-shaped clamp (4); The wedge-shaped stopper (8) is disposed at one end of the central connecting post (3) away from the pipe clamp body (1); the inner wedge-shaped clamp (5) is sleeved on the outside of the wedge-shaped stopper (8); The inner clamping nut (7) is threaded onto the central connecting column (3), and the end of the inner clamping nut (7) abuts against the end of the inner wedge-shaped clamp (5).
2. The pipe clamp assembly for pipe tensile testing according to claim 1, characterized in that, Both the outer wedge-shaped clamp (4) and the inner wedge-shaped clamp (5) are split structures, each consisting of 3-6 pieces, and are evenly distributed along the circumference.
3. The pipe clamp assembly for pipe tensile testing according to claim 1, characterized in that, The inner wall of the pipe clamp sleeve (2) is provided with an inner conical surface, and the outer wall of the outer wedge-shaped clamp (4) is provided with an outer conical surface that cooperates with the inner conical surface.
4. The pipe clamp assembly for pipe tensile testing according to claim 1, characterized in that, The outer wall of the wedge-shaped stopper (8) is provided with an outer conical surface, and the inner wall of the inner wedge-shaped clamp (5) is provided with an inner conical surface that matches the outer conical surface of the wedge-shaped stopper (8).
5. The pipe clamp assembly for pipe tensile testing according to claim 1, characterized in that, The inner wall surface of the outer wedge-shaped clamp (4) and the outer wall surface of the inner wedge-shaped clamp (5) are both provided with anti-slip teeth.
6. The pipe clamp assembly for pipe tensile testing according to claim 1, characterized in that, A pipe clamp connecting ring (9) is provided between the pipe clamp body (1) and the pipe clamp sleeve (2), and the pipe clamp sleeve (2) is fixedly connected to the pipe clamp body (1) through the pipe clamp connecting ring (9).
7. The pipe clamp assembly for pipe tensile testing according to claim 1, characterized in that, The tube clamp body (1) is provided with a through external connection hole (10); the assembly also includes a rod clamp body (11), one end of which is provided with an internal thread groove for connecting a rod sample.
8. The pipe clamp assembly for pipe tensile testing according to claim 1, characterized in that, The central connecting column (3) has an external thread section, and the internal clamping nut (7) is threaded onto the external thread section; the wedge-shaped stopper (8) is fixedly connected to the end of the central connecting column (3) or is an integral structure with the central connecting column (3).