Hollow tubular sample tool clamp and test method

Abstract

The invention belongs to the technical field of biomedical mechanics tests, and relates to a hollow tubular sample work fixture and a test method, the hollow tubular sample work fixture comprises an anti-crushing expansion bolt and a tester chuck; the anti-crushing expansion bolts are installed in the two ends of the hollow tubular sample, and the hollow tubular sample provided with the anti-crushing expansion bolts is clamped and loaded through a testing machine chuck. The tool clamp is installed in a clamping section pipe of the hollow tubular sample, the hollow tubular sample can be supported by screwing down the anti-crushing expansion bolt, the clamping section of the hollow tubular sample is effectively prevented from being crushed, the clamping section of the hollow tubular sample is made to be the same as that of a solid sample, and the clamping efficiency of the hollow tubular sample is improved. And the clamping load of a testing machine can be borne without being crushed.

Description

Technical Field

[0001] The invention belongs to the technical field of biomedical mechanics testing and relates to a hollow tubular sample fixture and a testing method. Background Art

[0002] Hollow structures and porous structures are widely used in the field of medical implants. Currently, bone implants that have entered clinical research and the market generally have hollow and porous structures. This hollow and porous structure provides space for bone tissue to grow into the prosthesis and can effectively avoid the stress shielding effect of the prosthesis. Existing studies have shown that adjustable hollow artificial vertebrae are stable and have good intervertebral height restoration, and are suitable for cases with extensive resection of the spinal vertebrae.

[0003] Experimental testing is an important part of verifying and assessing the safety and reliability of hollow / porous structure applications. Mechanical tests usually use standard specimens or structural feature simulations to obtain the mechanical properties of materials and optimize and improve them. These standard specimens or structural feature simulations are usually solid structures and cannot simulate real structures with hollow features, such as hollow artificial vertebrae, hollow bone implants, etc. CN117420012A discloses a nerve cannula tensile test fixture and test method, which wraps and clamps the nerve cannula with an outer tube and an inner plug, and a clearance is set between the outer tube and the inner plug. Under the action of the external clamping force, the nerve cannula is completely clamped, and the inner and outer walls of the nerve cannula are tightly fitted with the inner wall of the outer tube and the outer wall of the inner plug, respectively. However, this inner plug support method is passive support, that is, there is a certain gap between the inner plug and the nerve cannula, and the inner plug only plays a role in preventing the nerve cannula from being compressed and deformed too much; for some brittle hollow specimens, the gap / deformation between the inner plug and the nerve cannula is sufficient to cause compression damage to the specimen.

[0004] It is difficult to use the loading scheme of direct clamping of the test machine for hollow structures, which can easily lead to the crushing and failure of hollow structural parts. Hollow structures are subjected to torsion or tension-torsion combined loads during service. The development of tooling fixtures and clamping loading schemes suitable for hollow structures is of great significance to the mechanical performance research, optimization design and engineering application of hollow structures. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention aims to provide a tooling fixture and a testing method for hollow tubular specimens. The tooling fixture is installed in the clamping section of the hollow tubular specimen. By tightening the anti-crush expansion bolts, the hollow tubular specimen can be supported, effectively preventing the clamping section of the hollow tubular specimen from being crushed, so that the clamping section of the hollow tubular specimen is the same as that of a solid specimen and can withstand the clamping load of the testing machine without being crushed.

[0006] The present invention is achieved through the following technical solutions.

[0007] A hollow tubular specimen fixture, comprising an anti-crush expansion bolt and a testing machine chuck; The anti-crush expansion bolt comprises a nut, a sleeve and a bolt. One end of the bolt is designed with equal diameter and provided with a thread matching the nut, and the other end of the bolt is designed with a conical smooth surface. The outer shape of the sleeve corresponds to the inner contour of the hollow tubular specimen, so that the anti-crush expansion bolt can be applied to hollow tubular specimens with various hollow cross-sectional characteristics. The inner part of the sleeve is designed with a conical smooth surface. The conical angle of the inner conical surface of the sleeve is the same as the conical angle of the bolt conical surface. The sleeve is provided with a plurality of slits in the circumferential direction. The bolt is inserted into the sleeve, and the thread passes through the sleeve and matches the nut. During the process of tightening the nut and the bolt, the plurality of slits in the circumferential direction of the sleeve enable the sleeve to expand and deform relatively easily in the radial direction. Anti-crush expansion bolts are installed at both ends of the hollow tubular specimen, and the hollow tubular specimen with the anti-crush expansion bolts installed is clamped and loaded by the chuck of the testing machine.

[0008] Furthermore, the anti-crush expansion bolt also includes a washer, which is sleeved on the thread and located between the nut and the sleeve.

[0009] Furthermore, the washers include spring washers and flat washers.

[0010] Furthermore, the nut, spring washer, flat washer and bolt are made of metal materials to increase the strength of the anti-crush expansion bolt and provide sufficient supporting force for the hollow tubular specimen.

[0011] Furthermore, the sleeve is made of a medium hardness and medium strength material, so that the sleeve can relatively easily undergo radial expansion and deformation, and can better fit the interior of the hollow tubular specimen when supporting the hollow tubular specimen, thereby generating a relatively uniform supporting force.

[0012] Furthermore, the sleeve is made of plastic or rubber.

[0013] Furthermore, the bolts are designed to be solid or hollow structures. For hollow tubular specimens that do not require internal ventilation, solid bolts can be used; for hollow tubular specimens that require internal ventilation and pressurization / decompression, such as hollow tubular specimens of hollow air-cooled blades, hollow bolts can be used, and the interior of the specimen can be ventilated through the hollow bolts during the test.

[0014] Furthermore, the bolt is provided with an end portion at one end of a thread, which is designed to be an external hexagonal shape to facilitate the nut pre-tightening operation.

[0015] Furthermore, the inner cross-section of the hollow tubular specimen is circular, and the outer portion of the sleeve is designed with a constant diameter corresponding to the inner cross-section of the hollow tubular specimen.

[0016] A test method for the above-mentioned hollow tubular specimen fixture comprises the following steps: Step 1: Place the anti-crush expansion bolt into the clamping section at one end of the hollow tubular specimen, and apply a certain pre-tightening force by tightening the nut, so that the anti-crush expansion bolt effectively supports the hollow tubular specimen; perform the same operation on the clamping section at the other end of the hollow tubular specimen; Step 2: The hollow tubular specimen with the anti-crush expansion bolts obtained in step 1 is clamped and fixed by the clamping sections at both ends of the hollow tubular specimen using the chuck of the testing machine; Step 3: Set up the test loading scheme according to the test purpose and carry out mechanical tests on the hollow tubular specimens. Mechanical tests include tension, torsion, and tension-torsion.

[0017] Compared with the prior art, the advantages of the present invention are: The fixture is installed in the clamping section of the hollow tubular specimen. By tightening the anti-crush expansion bolt, the hollow tubular specimen can be supported, effectively preventing the clamping section of the hollow tubular specimen from being crushed, so that the clamping section of the hollow tubular specimen is the same as the solid specimen and can withstand the clamping load of the testing machine without being crushed. The contact surface between the casing and the bolt is designed as a cone surface. After tightening the anti-crush expansion bolt, the longer casing can be expanded, effectively and evenly supporting the clamping section of the hollow tubular specimen, so that the hollow tubular specimen can be clamped and loaded by the testing machine and carry out tensile, torsion, tension and twist tests; By using hollow bolts, it is possible to realize internal ventilation pressurization / decompression of hollow tubular specimens, and to carry out experimental research on hollow tubular specimens with internal ventilation requirements; By designing the outer profile of the casing, it can be applied to tubular specimens with various hollow cross-section characteristics; This test method adopts the scheme of internal support and external clamping, which can effectively ensure that the clamping part of the hollow tubular specimen is subjected to uniform force, prevent stress concentration at the clamping part, and effectively improve the success rate of the test; High-strength bolts, nuts, and washers combined with medium-hardness and medium-strength casing can not only provide sufficient supporting force, but also make the casing easier to deform, fit tightly to the hollow tubular specimen, and produce more uniform supporting force. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a front view of the anti-crush expansion bolt in an embodiment of the present invention.

[0019] Figure 2 It is a cross-sectional view of an anti-crush expansion bolt in an embodiment of the present invention.

[0020] Figure 3 It is a front view of the sleeve of the present invention.

[0021] Figure 4 It is a cross-sectional view of the sleeve of the present invention.

[0022] Figure 5 It is a front view of the bolt of the present invention.

[0023] Figure 6 It is a cross-sectional view of the bolt of the present invention.

[0024] Figure 7 It is a partial schematic diagram of the installation of the anti-crush expansion bolt of the present invention in a hollow tubular specimen.

[0025] Figure 8 It is a partial cross-sectional view of the installation of the anti-crush expansion bolt of the present invention in a hollow tubular specimen.

[0026] Fig. 9 It is a schematic diagram of the clamping and loading of the hollow tubular sample of the present invention.

[0027] Fig.10 It is a cross-sectional view of the clamping and loading of the hollow tubular specimen of the present invention.

[0028] Fig.11 It is a schematic diagram of a hollow bolt of the present invention.

[0029] Fig.12 It is a cross-sectional view of a hollow bolt of the present invention.

[0030] Fig.13 It is an isometric schematic diagram of a sleeve with a specific cross-sectional shape according to the present invention.

[0031] Fig.14 yes Fig.13 Schematic diagram from another perspective.

[0032] Fig.15 yes Fig.13 Show or hide part of the diagram.

[0033] Fig.16 It is a schematic diagram of a finite element model of a hollow tubular sample holder of the present invention.

[0034] Fig.17 yes Fig.16 Show or hide part of the diagram.

[0035] Fig.18 It is a second schematic diagram of the finite element model of the hollow tubular sample clamp of the present invention.

[0036] Fig.19 yes Fig.18 Show or hide part of the diagram.

[0037] Fig. 20 This is a diagram showing the analysis results of the sample clamping position of the finite element model of the hollow tubular sample clamping of the present invention.

[0038] Fig.21 This is a diagram showing the analysis results of the clamping position of two specimens of the finite element model of the hollow tubular specimen clamp of the present invention.

[0039] Fig. 22 It is a stress distribution diagram of a hollow tubular specimen clamped by a finite element model of the present invention.

[0040] Fig.23 It is a stress distribution diagram of two specimens of the hollow tubular specimen clamped by a finite element model of the present invention.

[0041] In the figure: 1. Anti-crush expansion bolt, 2. Testing machine chuck, 3. Hollow tubular specimen; 101. nut, 102. spring washer, 103. flat washer, 104. sleeve, 105. bolt, 106. thread. DETAILED DESCRIPTION

[0042] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0043] like Figure 1 and Fig.10 As shown, a hollow tubular specimen fixture comprises an anti-crushing expansion bolt 1 and a testing machine chuck 2; The anti-crush expansion bolt 1 comprises a nut 101, a sleeve 104 and a bolt 105. One end of the bolt 105 is designed with equal diameter and is provided with a thread 106 that matches the nut 101, and the other end of the bolt 105 is designed with a conical smooth surface. The outer shape of the sleeve 104 corresponds to the inner contour of the hollow tubular specimen 3, so that the anti-crush expansion bolt 1 can be applied to hollow tubular specimens 3 with various hollow cross-sectional characteristics. The inner part of the sleeve 104 is designed with a conical smooth surface. The cone angle of the cone surface inside the sleeve 104 is the same as the cone angle of the cone surface of the bolt 105. The sleeve 104 is provided with several slits in the circumferential direction. The bolt 105 is inserted into the sleeve 104, and the thread 106 passes through the sleeve 104 and matches with the nut 101. During the tightening process of the nut 101 and the bolt 105, the several slits in the circumferential direction of the sleeve 104 enable the sleeve 104 to expand and deform relatively easily in the radial direction. Anti-crush expansion bolts 1 are installed inside both ends of the hollow tubular specimen 3, and the hollow tubular specimen 3 with the anti-crush expansion bolts 1 installed is clamped and loaded by the testing machine chuck 2. In this embodiment, the internal cross-section of the hollow tubular specimen 3 is circular, and the outside of the sleeve 104 is designed with a constant diameter corresponding to the internal cross-section of the hollow tubular specimen 3. The testing machine chuck 2 is a round bar chuck of a mechanical properties testing machine, and the hollow tubular specimen 3 with the anti-crush expansion bolts 1 installed is clamped and loaded by the round bar chuck.

[0044] Furthermore, the anti-crush expansion bolt 1 also includes a washer, which is sleeved on the thread 106 and located between the nut 101 and the sleeve 104 .

[0045] Furthermore, the washers include a spring washer 102 and a flat washer 103 .

[0046] Furthermore, the nut 101 , the spring washer 102 , the flat washer 103 , and the bolt 105 are made of metal materials to increase the strength of the anti-crush expansion bolt 1 and provide sufficient supporting force for the hollow tubular specimen 3 .

[0047] Furthermore, the sleeve 104 is made of a medium-hardness and medium-strength material, so that the sleeve 104 can be relatively easily expanded and deformed radially, and can better fit the interior of the hollow tubular specimen 3 when supporting the hollow tubular specimen 3, thereby generating a relatively uniform supporting force.

[0048] Furthermore, the sleeve 104 is made of plastic or rubber.

[0049] Furthermore, the bolt 105 is designed to be a solid or hollow structure. For a hollow tubular specimen 3 that does not require internal ventilation, a solid bolt 105 can be used; for a hollow tubular specimen 3 that requires internal ventilation and pressurization / decompression, such as a hollow tubular specimen of a hollow air-cooled blade, a hollow bolt 105 can be used. During the test, the interior of the specimen is ventilated through the hollow bolt 105.

[0050] Furthermore, the end of the bolt 105 is provided with a thread 106 at one end, which is designed to be an external hexagonal shape to facilitate the pre-tightening operation of the nut 101.

[0051] A test method for the above-mentioned hollow tubular specimen fixture comprises the following steps: Step 1: Place the anti-crush expansion bolt 1 into the clamping section at one end of the hollow tubular specimen 3, and apply a certain pre-tightening force by tightening the nut 101, so that the anti-crush expansion bolt 1 effectively supports the hollow tubular specimen 3; perform the same operation on the clamping section at the other end of the hollow tubular specimen 3; Step 2: The hollow tubular sample 3 with the anti-crush expansion bolt 1 installed obtained in step 1 is clamped and fixed by the clamping sections at both ends of the hollow tubular sample 3 using the chuck 2 of the testing machine; Step 3: Set the test loading scheme according to the test purpose, and carry out mechanical tests on the hollow tubular specimen 3. The mechanical tests include tension, torsion, and tension-torsion.

[0052] Combination Fig.11 and Fig.12As shown, the bolt 105 can be designed to be a solid or hollow structure. For hollow tubular specimens that do not require internal ventilation, solid bolts can be used; for hollow tubular specimens that require internal ventilation pressurization / decompression, such as hollow tubular specimens of hollow air-cooled blades, hollow bolts can be used to ventilate the interior of the specimen during the test.

[0053] Combination Fig.13 , Fig.14 , Fig.15 As shown, the interior of the sleeve 104 is a conical surface that matches the bolt 105, and the exterior of the sleeve 104 can be designed into a specific cross-sectional shape according to the internal contour of the hollow tubular specimen 3, so that the anti-crush expansion bolt can be applied to tubular specimens with various hollow cross-sectional characteristics.

[0054] refer to Figures 16 to 23 , Fig.16 and Fig.17 This is a schematic diagram of a finite element model 1 of a hollow tubular specimen clamp, in which the anti-crush expansion bolts are not installed; Fig.18 and Fig.19 Schematic diagram of finite element model 2 for the hollow tubular specimen clamp. Model 2 is installed with anti-crush expansion bolts.

[0055] Fig. 20 This is a finite element model of a hollow tubular specimen clamping part analysis result diagram. Fig.21 This is the analysis result diagram of the clamping position of the hollow tubular specimen in the finite element model, which includes the analysis results of radial stress, circumferential stress, radial strain, and circumferential strain. Fig. 20 and Fig.21 It can be seen that compared with model 1 without anti-crush expansion bolts, model 2 with anti-crush expansion bolts has greater radial stress and circumferential stress, and smaller radial strain and circumferential strain, indicating that the internal anti-crush expansion bolts can effectively support the hollow specimen and prevent the hollow specimen from producing excessive compression deformation / strain. At the same time, the internal support of the anti-crush expansion bolts can increase the compressive stress between the hollow specimen and the fixture, and effectively increase the clamping loading force of the hollow specimen.

[0056] Fig. 22 It is the stress distribution diagram of the hollow tubular specimen clamped by the finite element model. Fig.23 It is the stress distribution diagram of two specimens of the hollow tubular specimen clamped by the finite element model. Fig. 22 and Fig.23 It can be seen that compared with model 1 without anti-crush expansion bolts, the tensile stress distribution of the hollow specimen test section of model 2 with anti-crush expansion bolts installed is more uniform, and the tensile test effect is better.

[0057] The above description is only a preferred embodiment of the present invention, and does not limit the implementation mode and protection scope of the present invention. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the description and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. A hollow tubular specimen fixture, characterized in that: It comprises an anti-crush expansion bolt (1) and a testing machine chuck (2); The anti-crush expansion bolt (1) comprises a nut (101), a sleeve (104), and a bolt (105); one end of the bolt (105) is designed with a constant diameter and is provided with a thread (106) that matches the nut (101); the other end of the bolt (105) is designed with a conical smooth surface; the outer surface of the sleeve (104) is a shape corresponding to the inner contour of the hollow tubular specimen (3); the inner surface of the sleeve (104) is designed with a conical smooth surface; 04) The cone angle of the inner cone surface is the same as the cone angle of the cone surface of the bolt (105), and the sleeve (104) is provided with a plurality of slits in the circumferential direction; the bolt (105) is inserted into the sleeve (104), and the thread (106) passes through the sleeve (104) and cooperates with the nut (101), and during the process of tightening the nut (101) and the bolt (105), the plurality of slits in the circumferential direction of the sleeve (104) enable the sleeve (104) to expand and deform relatively easily in the radial direction; Anti-crush expansion bolts (1) are installed inside both ends of the hollow tubular specimen (3), and the hollow tubular specimen (3) with the anti-crush expansion bolts (1) installed is clamped and loaded by a testing machine chuck (2).

2. The hollow tubular specimen fixture according to claim 1, characterized in that: The anti-crush expansion bolt (1) further comprises a washer, which is sleeved on the thread (106) and located between the nut (101) and the sleeve (104).

3. The hollow tubular specimen fixture according to claim 2, characterized in that: The washers include a spring washer (102) and a flat washer (103).

4. The hollow tubular specimen fixture according to claim 3, characterized in that: The nut (101), the spring washer (102), the flat washer (103), and the bolt (105) are made of metal material.

5. The hollow tubular specimen fixture according to claim 1, characterized in that: The sleeve (104) is made of a medium-hardness and medium-strength material.

6. The hollow tubular specimen fixture according to claim 1, characterized in that: The sleeve (104) is made of plastic or rubber material.

7. The hollow tubular specimen fixture according to claim 1, characterized in that: The bolt (105) is designed to be a solid or hollow structure.

8. The hollow tubular specimen fixture according to claim 1, characterized in that: The bolt (105) is provided with an end portion having a thread (106) at one end thereof and is designed to be an external hexagonal shape, so as to facilitate the pre-tightening operation of the nut (101).

9. The hollow tubular specimen fixture according to claim 1, characterized in that: The inner cross section of the hollow tubular specimen (3) is circular, and the outer portion of the sleeve (104) is designed to have a constant diameter corresponding to the inner cross section of the hollow tubular specimen (3).

10. A test method for a hollow tubular specimen fixture as claimed in any one of claims 1 to 9, characterized in that: The steps include: Step 1: Place the anti-crush expansion bolt (1) into the clamping section at one end of the hollow tubular specimen (3), and apply a certain pre-tightening force by tightening the nut (101) so that the anti-crush expansion bolt (1) effectively supports the hollow tubular specimen (3); perform the same operation on the clamping section at the other end of the hollow tubular specimen (3); Step 2: The hollow tubular specimen (3) installed with the anti-crush expansion bolt (1) obtained in step 1 is clamped and fixed by using the clamping sections at both ends of the hollow tubular specimen (3) with the clamping head (2) of the testing machine; Step 3: Set up a test loading plan according to the test purpose and conduct a mechanical test on the hollow tubular specimen (3).

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