A thin-walled round tube specimen fatigue test fixture and automatic centering clamping method

Abstract

The present invention belongs to the technical field of test fixtures, and particularly relates to a fatigue test fixture for thin-walled round tube specimens and an automatic centering clamping method. The test fixture comprises two groups of clamp bodies symmetrically clamped on both sides of the specimen, wherein: the clamp bodies comprise an inner clamping structure and a clamp body body that are coaxial and arranged inside and outside, an annular gap space for inserting the specimen is formed between the inner clamping structure and the clamp body body, a clamping cone ring structure is respectively inserted between the inner clamping structure, the clamp body body and the specimen, and a clamping adjusting member for adjusting the depth of each clamping cone ring structure pushed into the annular gap space is also provided on the clamp body body, so that the specimen is automatically centering and clamped between the two groups of clamp bodies. The test fixture is a test fixture with simple structure, convenient installation and low cost, so as to ensure that the thin-walled round tube specimen is firmly clamped, the specimen is well centered and not eccentric during clamping, and can be used for tensile, compressive and torsional fatigue performance tests of thin-walled tube specimens.

Description

Technical Field

[0001] The invention belongs to the technical field of test fixtures, and in particular relates to a fatigue test fixture for a thin-walled round tube specimen and an automatic centering clamping method. Background Art

[0002] The tensile and compressive fatigue performance test of metal materials requires that the specimen be well centered in the clamping process without eccentricity, otherwise stress concentration and distortion will occur, affecting the test results. For fatigue performance test of special structural parts such as thin-walled pipes, the clamping tool has a greater impact on the test results. If stress concentration or distortion occurs, the specimen will fail at the stress concentration or distortion. How to ensure that thin-walled pipe structural parts are firmly clamped is a technical problem that needs to be solved urgently by technical personnel in this field.

[0003] The difficulty in solving the above technical problems lies in how to ensure that special structural parts such as thin-walled pipes can be clamped firmly and non-eccentrically to meet the tensile and compressive fatigue performance test requirements of thin-walled pipes. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a thin-walled circular tube specimen fatigue test fixture and an automatic centering clamping method with a simple structure, easy installation and low cost in response to the above-mentioned technical status quo, so as to ensure that the thin-walled circular tube specimen is firmly clamped for use in tensile, compressive and torsional fatigue performance testing of thin-walled tube specimens.

[0005] The technical solution adopted by the present invention to solve this problem is:

[0006] A thin-walled circular tube specimen fatigue test fixture comprises two sets of clamp bodies symmetrically clamped on both sides of the specimen, wherein: the clamp bodies comprise an inner clamping structure and a clamp body body coaxially arranged inside and outside, an annular gap space for inserting the specimen is formed between the inner clamping structure and the clamp body body, clamping cone ring structures are respectively inserted between the inner clamping structure, the clamp body body and the specimen, and the clamp body body is also provided with a clamping adjustment member for adjusting the depth of each clamping cone ring structure pushed into the annular gap space, so that the specimen is automatically centered and clamped between the two sets of clamp bodies.

[0007] Preferably, the inner clamping structure comprises a coaxially fixed core rod and an inner clamping block, wherein the core rod is a hollow tube structure, one end of which is connected to the inner clamping block via a thread, and the other end is connected to the testing machine.

[0008] Further preferably, the clamp body includes an integrally connected supporting part and a clamping part, the supporting part is a hollow tube structure and is coaxially sleeved on the outside of the core rod, the clamping part is a hollow column structure with one end open and is coaxially sleeved on the outside of the inner clamping block, and the diameter of the clamping part is larger than the diameter of the supporting part.

[0009] Further preferably, a keyway is formed on the inner wall of the support portion, and the keyway of the support portion is axially slidably adapted to the core rod through the keyway.

[0010] Further preferably, the clamping cone ring structure includes an inner clamping cone ring inserted between the inner clamping block and the sample and an outer clamping cone ring inserted between the sample and the clamping part, the cross-sections of the inner clamping cone ring and the outer clamping cone ring are wedge-shaped, the thickness of the inner clamping cone ring and the outer clamping cone ring gradually decreases along the direction of pushing into the annular gap space, and the inner clamping cone ring and the outer clamping cone ring are pushed into the annular gap space in opposite directions.

[0011] Further preferably, the inner clamping cone ring and the outer clamping cone ring are deformable cone rings.

[0012] Further preferably, the clamping adjustment member includes an inner clamping screw cap for adjusting the depth of the inner clamping cone ring pushed into the annular gap and an outer clamping screw cap for adjusting the depth of the outer clamping cone ring pushed into the annular gap, the end of the inner clamping cone ring abuts against the clamping part, and the end of the outer clamping cone ring abuts against the outer clamping screw cap.

[0013] Further preferably, the inner clamping screw cap is sleeved on the outer sides of the core rod and the supporting part, the inner clamping screw cap and the core rod are movably connected via a positioning structure, and the inner clamping screw cap and the supporting part are connected via threads.

[0014] Further preferably, the outer clamping screw cap is connected to the clamping portion via a threaded connection, and the outer clamping screw cap is provided with a sample passing hole for the sample to pass through.

[0015] Further preferably, the positioning structure includes an upper positioning block and a lower positioning block respectively fixed to the core rod by pins, and the end of the inner clamping screw cap is clamped between the upper positioning block and the lower positioning block, so that the inner clamping screw cap rotates around the core rod at a fixed position on the core rod.

[0016] The second object of the present invention is to provide an automatic centering and clamping method using the above-mentioned thin-walled round tube specimen fatigue test fixture, comprising the following steps:

[0017] Step 1: insert one end of the sample between the inner clamping cone ring and the outer clamping cone ring of a set of clamp bodies, and squeeze and deform the inner clamping cone ring and the outer clamping cone ring by rotating the inner clamping screw cap and the outer clamping screw cap, so that one end of the sample is squeezed and clamped, and the sample and the set of clamp bodies are axially overlapped;

[0018] Step 2: Insert the other end of the sample between the inner clamping cone ring and the outer clamping cone ring of another set of clamping bodies, and squeeze and deform the inner clamping cone ring and the outer clamping cone ring by rotating the inner clamping screw cap and the outer clamping screw cap. The other end of the sample is squeezed and clamped, and the sample and the set of clamping bodies are axially aligned, so that the sample is automatically centered and clamped between the two sets of clamping bodies.

[0019] The advantages and positive effects of the present invention are:

[0020] 1. In the present invention, the test fixture includes a core rod, an upper positioning block, a lower positioning block, an inner clamping screw cap, a clamp body, an inner clamping cone ring, an inner clamping block, an outer clamping cone ring and an outer clamping screw cap. The test fixture is a test fixture with a simple structure, easy installation and low cost, and can be used for tensile, compressive and torsional fatigue performance tests of thin-walled pipe specimens.

[0021] 2. In the present invention, the upper and lower sets of clamps are symmetrically clamped on both sides of the sample, and the internal and external clamping methods are used to ensure that the sample does not deform or twist during the clamping process. During the test, the sample is subjected to tensile and compressive fatigue loading, and no stress concentration point is generated, so that the sample is better in a two-force rod state.

[0022] 3. In the present invention, the two sets of clamps that are symmetrical in upper and lower directions can automatically center and clamp the specimen between the two sets of clamps. The specimen is well centered during clamping and is not eccentric, which can meet the requirements for tensile and compressive fatigue performance testing of thin-walled pipe fittings, so that the test fixture can be used for tensile, compressive and torsional fatigue performance testing of thin-walled pipe specimens. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The technical solution of the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments, but it should be understood that these drawings are designed only for explanation purposes and are not intended to limit the scope of the present invention. In addition, unless otherwise specified, these drawings are intended only to conceptually illustrate the structural configurations described herein and are not necessarily drawn to scale.

[0024] Figure 1 It is the intention of the fixture for fatigue testing of thin-walled round tube specimens;

[0025] Figure 2 This is a flow chart of Example 2.

[0026] In the figure: 1-core rod; 2-upper positioning block; 3-lower positioning block; 4-inner clamping screw cap; 5-clamping body; 501-supporting part; 502-clamping part; 6-inner clamping cone ring; 7-inner clamping block; 8-outer clamping cone ring; 9-outer clamping screw cap; 10-thin-walled pipe fitting. DETAILED DESCRIPTION

[0027] First of all, it should be noted that the specific structure, features and advantages of the present invention will be specifically described below by way of example, but all descriptions are only for illustration and should not be understood as limiting the present invention in any way. In addition, any single technical feature described or implied in the embodiments mentioned herein, or any single technical feature displayed or implied in the drawings, can still be combined or deleted between these technical features (or their equivalents) to obtain more other embodiments of the present invention that may not be directly mentioned in this document. In addition, in order to simplify the drawings, the same or similar technical features may be marked only in one place in the same drawing.

[0028] In the present invention, unless otherwise clearly specified and limited, the terms "installation", "setting", "connection", "fixation", "screwing" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined, for ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances. The present invention is described in detail below with reference to the accompanying drawings.

[0029] Embodiment 1:

[0030] A thin-walled circular tube specimen fatigue test fixture comprises two sets of clamp bodies symmetrically clamped on both sides of the specimen, wherein: the clamp bodies comprise an inner clamping structure and a clamp body body 5 coaxially arranged inside and outside, an annular gap space for inserting the specimen 10 is formed between the inner clamping structure and the clamp body body 5, clamping cone ring structures are respectively inserted between the inner clamping structure, the clamp body body 5 and the specimen 10, and the clamp body body 5 is also provided with a clamping adjustment member for adjusting the depth of each clamping cone ring structure pushed into the annular gap space, so that the specimen 10 is automatically centered and clamped between the two sets of clamp bodies.

[0031] In this embodiment, the sample 10 is a thin-walled pipe. Figure 1As shown, the test fixture includes two identical upper and lower groups of clamp bodies. When testing the tensile and compressive fatigue properties of thin-walled pipe fittings, the sample 10 is inserted into the annular space between the inner clamping structure of the fixture and the clamp body 5. At the same time, clamping cone ring structures are respectively inserted between the inner clamping structure, the clamp body 5 and the sample 10. The clamping cone ring structure is pushed into the annular space through the clamping adjustment piece to squeeze and deform the clamping cone ring structure, and the thin-walled pipe fitting is squeezed and clamped. The upper and lower groups of clamp bodies are symmetrically clamped on both sides of the sample. The method of simultaneous internal and external clamping is used to ensure that the sample is not deformed or twisted during the clamping process. During the test, by applying tensile and compressive fatigue loading to the sample, no stress concentration point is generated, so that the sample is better in a two-force rod state.

[0032] The two sets of clamps symmetrically arranged up and down can automatically center and clamp the specimen 10 between the two sets of clamps. The specimen is well centered and not eccentric during clamping, which can meet the requirements of the tensile and compressive fatigue performance test of thin-walled pipe fittings, so that the test fixture can be used for tensile, compressive and torsional fatigue performance tests of thin-walled pipe specimens.

[0033] Furthermore, in the present embodiment, it can also be considered that the inner clamping structure includes a coaxially fixed core rod 1 and an inner clamping block 7, wherein the core rod 1 is a hollow tube structure, one end of which is connected to the inner clamping block 7 via a thread, and the other end is connected to the testing machine, and the connection method is determined according to different testing machine models.

[0034] Furthermore, in this embodiment, it can also be considered that Figure 1 As shown, the clamp body 5 includes a supporting portion 501 and a clamping portion 502 that are integrally connected. The supporting portion 501 is a hollow tube structure and is coaxially sleeved on the outside of the core rod 1. The clamping portion 502 is a hollow column structure with one end open and is coaxially sleeved on the outside of the inner clamping block 7. The diameter of the clamping portion 502 is greater than the diameter of the supporting portion 501.

[0035] Furthermore, in this embodiment, it can also be considered that the inner wall of the support part 501 is formed with a keyway, the keyway of the support part 501 is axially slidably adapted to the core rod 1 through the keyway, and the keyway of the inner hole of the clamp body 5 is matched with the core rod 1 through the keyway, ensuring that the clamp body 5 can slide axially along the core rod without rotating.

[0036] Furthermore, in the present embodiment, it can also be considered that the clamping cone ring structure includes an inner clamping cone ring 6 inserted between the inner clamping block 7 and the sample 10 and an outer clamping cone ring 8 inserted between the sample 10 and the clamping part 502, the cross-sections of the inner clamping cone ring 6 and the outer clamping cone ring 8 are wedge-shaped, the thickness of the inner clamping cone ring 6 and the outer clamping cone ring 8 gradually decreases along the direction of pushing into the annular gap space, and the inner clamping cone ring 6 and the outer clamping cone ring 8 are pushed into the annular gap space in opposite directions.

[0037] Furthermore, in the present embodiment, it can also be considered that the inner clamping cone ring 6 and the outer clamping cone ring 8 are deformable cone ring parts, which can be but are not limited to deformable metal materials or deformable rubber materials. Considering factors such as connection strength, copper is preferred, and the structural material of the test fixture except the inner clamping cone ring 6 and the outer clamping cone ring 8 is preferably stainless steel.

[0038] Furthermore, in the present embodiment, it can also be considered that the clamping adjustment member includes an inner clamping screw cap 4 for adjusting the depth of the inner clamping cone ring 6 pushed into the annular gap and an outer clamping screw cap 9 for adjusting the depth of the outer clamping cone ring 8 pushed into the annular gap, and the end of the inner clamping cone ring 6 abuts against the clamping part 502, and the end of the outer clamping cone ring 8 abuts against the outer clamping screw cap 9.

[0039] Furthermore, in this embodiment, it can also be considered that the inner clamping screw cap 4 is sleeved on the outside of the core rod 1 and the support part 501, the inner clamping screw cap 4 and the core rod 1 are movably connected through a positioning structure, and the inner clamping screw cap 4 and the support part 501 are connected through a thread.

[0040] Furthermore, in this embodiment, it can also be considered that the outer clamping screw cap 9 is connected to the clamping portion 502 via a threaded connection, and the outer clamping screw cap 9 is provided with a sample passing hole for the sample to pass through.

[0041] Furthermore, in this embodiment, the positioning structure includes an upper positioning block 2 and a lower positioning block 3 respectively fixed to the core rod 1 by pins, and the end of the inner clamping screw cap 4 is clamped between the upper positioning block 2 and the lower positioning block 3, so that the inner clamping screw cap 4 rotates around the core rod 1 at a fixed position on the core rod 1, such as Figure 1 The upper positioning block 2 and the lower positioning block 3 are fixed to the core rod 1 by pins, and the ends of the inner clamping screw cap 4 are clamped between the two positioning blocks, so that the inner clamping screw cap 4 can be ensured to rotate around the core rod at a fixed position.

[0042] Working principle: Figure 1 As shown, a thin-walled round tube specimen fatigue test fixture includes two identical upper and lower clamp bodies, and the clamp body includes a core rod 1, an upper positioning block 2, a lower positioning block 3, an inner clamping screw cap 4, a clamp body 5, an inner clamping cone ring 6, an inner clamping block 7, an outer clamping cone ring 8 and an outer clamping screw cap 9. The inner clamping screw cap 4 is connected to the small end (supporting part 501) of the clamp body 5 by threads, and the outer clamping screw cap 9 is connected to the large end (clamping part 502) of the clamp body 5 by threads. An inner clamping cone ring 6 and an outer clamping cone ring 8 with openings are arranged inside the clamp body 5. By rotating the inner clamping screw cap 4 and the outer clamping screw cap 9, the thin-walled pipe in the middle of the cone ring can be clamped, thereby achieving the purpose of fixing the specimen.

[0043] By using this test fixture, when testing the tensile and compressive fatigue properties of thin-walled pipe specimens, the specimen is inserted between the inner clamping cone ring 6 and the outer clamping cone ring 8 of the fixture, and the inner clamping screw cap 4 and the outer clamping screw cap 9 are rotated to squeeze the inner clamping cone ring 6 and the outer clamping cone ring 8 to deform, so as to squeeze and clamp the thin-walled pipe, thereby achieving the purpose of stably clamping the thin-walled pipe specimen. The test fixture is a test fixture with simple structure, easy installation and low cost, and can be used for tensile, compressive and torsional fatigue properties tests of thin-walled pipe specimens.

[0044] Embodiment 2:

[0045] An automatic centering and clamping method for the thin-walled round tube specimen fatigue test fixture described in Application Example 1 comprises the following steps:

[0046] Step 1: insert one end of the sample 10 between the inner clamping cone ring 6 and the outer clamping cone ring 8 of a set of clamp bodies, and squeeze and deform the inner clamping cone ring 6 and the outer clamping cone ring 8 by rotating the inner clamping screw cap 4 and the outer clamping screw cap 9, so that one end of the sample 10 is squeezed and clamped, and the sample 10 and the set of clamp bodies coincide axially;

[0047] Step 2: Insert the other end of the sample 10 between the inner clamping cone ring 6 and the outer clamping cone ring 8 of another set of clamp bodies, and squeeze and deform the inner clamping cone ring 6 and the outer clamping cone ring 8 by rotating the inner clamping screw cap 4 and the outer clamping screw cap 9. The other end of the sample 10 is squeezed and clamped, and the sample 10 and the set of clamp bodies are axially overlapped, so that the sample 10 is automatically centered and clamped between the two sets of clamp bodies.

[0048] Through the thin-walled circular tube specimen fatigue test fixture, the specimen is automatically clamped between the two sets of clamps by means of simultaneous internal and external clamping, ensuring that the specimen does not deform or twist during the clamping process. During the test, by applying tensile and compressive fatigue loading to the specimen, no stress concentration point is generated, allowing the specimen to be better in a two-force rod state.

[0049] The above embodiments describe the present invention in detail, but the contents are only preferred embodiments of the present invention and cannot be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. A thin-walled round tube specimen fatigue test fixture, Features: It includes two sets of clamp bodies symmetrically clamped on both sides of the specimen, where: The clamp body comprises an inner clamping structure and a clamp body body (5) which are coaxially arranged inside and outside, an annular gap space for inserting the sample (10) is formed between the inner clamping structure and the clamp body body (5), clamping cone ring structures are respectively inserted between the inner clamping structure, the clamp body body (5) and the sample (10), and the clamp body body (5) is also provided with a clamping adjustment member for adjusting the depth of each clamping cone ring structure pushed into the annular gap space, so that the sample (10) is automatically centered and clamped between the two sets of clamp bodies; The inner clamping structure comprises a core rod (1) and an inner clamping block (7) which are coaxially fixed; the core rod (1) is a hollow tube structure, one end of which is connected to the inner clamping block (7) via a thread, and the other end of which is connected to the testing machine; The clamp body (5) comprises an integrally connected supporting portion (501) and a clamping portion (502); the supporting portion (501) is a hollow tube structure and is coaxially sleeved on the outside of the core rod (1); the clamping portion (502) is a hollow column structure with one end open and is coaxially sleeved on the outside of the inner clamping block (7); the diameter of the clamping portion (502) is greater than the diameter of the supporting portion (501); The clamping cone ring structure comprises an inner clamping cone ring (6) inserted between the inner clamping block (7) and the sample (10) and an outer clamping cone ring (8) inserted between the sample (10) and the clamping portion (502); the thickness of the inner clamping cone ring (6) and the outer clamping cone ring (8) gradually decreases along the direction of being pushed into the annular gap space, and the inner clamping cone ring (6) and the outer clamping cone ring (8) are pushed into the annular gap space in opposite directions; the inner clamping cone ring (6) and the outer clamping cone ring (8) are deformable conical ring parts; The clamping adjustment member comprises an inner clamping screw cap (4) for adjusting the depth of the inner clamping cone ring (6) pushed into the annular gap and an outer clamping screw cap (9) for adjusting the depth of the outer clamping cone ring (8) pushed into the annular gap, the end of the inner clamping cone ring (6) abuts against the clamping portion (502), and the end of the outer clamping cone ring (8) abuts against the outer clamping screw cap (9).

2. A thin-walled round tube specimen fatigue test fixture according to claim 1, Features: The inner wall of the support portion (501) is formed with a keyway, and the keyway of the support portion (501) is axially slidably adapted to the core rod (1) through the keyway.

3. A thin-walled round tube specimen fatigue test fixture according to claim 1, Features: The inner clamping screw cap (4) is sleeved on the outer sides of the core rod (1) and the supporting part (501); the inner clamping screw cap (4) and the core rod (1) are movably connected via a positioning structure; and the inner clamping screw cap (4) and the supporting part (501) are connected via a thread.

4. A thin-walled round tube specimen fatigue test fixture according to claim 1, Features: The outer clamping screw cap (9) and the clamping portion (502) are connected via threads.

5. An automatic centering and clamping method using the thin-walled round tube specimen fatigue test fixture as described in any one of claims 1 to 4, Features: The following steps are involved: Step 1: insert one end of the sample (10) between an inner clamping cone ring (6) and an outer clamping cone ring (8) of a set of clamp bodies, and rotate the inner clamping screw cap (4) and the outer clamping screw cap (9) to squeeze and deform the inner clamping cone ring (6) and the outer clamping cone ring (8), so that one end of the sample (10) is squeezed and clamped, and the sample (10) and the set of clamp bodies are axially overlapped; Step 2: Insert the other end of the sample (10) between the inner clamping cone ring (6) and the outer clamping cone ring (8) of another set of clamp bodies, and squeeze and deform the inner clamping cone ring (6) and the outer clamping cone ring (8) by rotating the inner clamping screw cap (4) and the outer clamping screw cap (9). The other end of the sample (10) is squeezed and clamped, and the sample (10) and the set of clamp bodies are axially overlapped, so that the sample (10) is automatically centered and clamped between the two sets of clamp bodies.

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