Wedge load test method for full-thread stud

Abstract

The invention discloses a wedge load test method for a full-thread stud. A thread cavity is formed in an upper clamp and used for screwing threads at the upper end of the full-thread stud; a lower cavity is formed in the clamp body, an opening of the lower cavity is a first inclined face, the outer wall of the supporting pad is a second inclined face matched with the first inclined face, the supporting pad is arranged at the opening of the lower cavity and penetrates through the lower end of the full-thread stud, the lower end of the full-thread stud is located in the lower cavity and penetrates through a threaded hole of the threaded wedge pad, and the threaded wedge pad has an inclined angle. The method has the advantages that if the thread strength is insufficient, the defect on the surface of the thread can be torn to form a crack source under a multi-time wedge load test method, appearance inspection is performed on the thread of the full-thread stud after the test is finished, and if the crack source exists at the root of the thread, the thread strength of the full-thread stud is insufficient.

Description

Technical Field

[0001] The invention relates to the field of testing technology, and in particular to a wedge load test method for a full-thread stud used for testing the reliability of a bolt under repeated loads. Background Art

[0002] Fully threaded studs are mainly used for flange connections in petroleum, chemical industry, and pressure pipelines. They are subjected to hydraulic pulsation forces, which belong to high-cycle stress. The bolt implementation standards are GB / T22513 and HG20634. In the standards, mechanical tensile test bars are used for tensile tests. The detection performance of tensile test bars cannot completely replace the overall performance of bolts, because the threads of fully threaded studs are usually rolled threads after heat treatment. After heat treatment, the thread surface will be "hardened" due to the influence of extrusion stress. In this way, when the thread is subjected to hydraulic high-cycle pulsation force load, it is easy to form a crack source from the hardened part of the thread, reducing the fatigue strength and causing early failure and fracture of the fully threaded stud. Summary of the invention

[0003] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a wedge load test method for a full-thread stud for testing the reliability of the bolt under repeated loads.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A wedge load test method for a full-thread stud comprises an upper fixture and a lower fixture, wherein the lower fixture comprises a fixture body, a threaded wedge pad and a support pad, wherein a threaded cavity is arranged in the upper fixture for screwing the thread of the upper end of the full-thread stud; a lower cavity is arranged in the fixture body, wherein the opening of the lower cavity is a first inclined surface, and the outer wall of the support pad is a second inclined surface matching the first inclined surface, wherein the support pad is arranged at the opening of the lower cavity and is passed through by the lower end of the full-thread stud, wherein the lower end of the full-thread stud is located in a threaded hole in the lower cavity passing through the threaded wedge pad, and the threaded wedge pad has an oblique angle;

[0006] S1: Install the upper fixture on the upper beam of the testing machine, and the lower fixture on the lower beam of the testing machine;

[0007] S2: Screw the upper end of the full-thread stud into the upper fixture, the screw-in length shall not be less than the thread diameter of the full-thread stud, and screw the lower end of the full-thread stud into the threaded hole of the threaded wedge after passing through the support pad, the screw-in length shall not be less than the thread diameter of the full-thread stud. At the same time, make sure that the gap length between the upper fixture and the lower fixture is not less than 6 times the pitch length;

[0008] S3: Move the upper beam of the testing machine to subject the full-thread stud to tensile force. At this moment, due to the bevel of the threaded wedge pad, the full-thread stud is subjected to bending force. When the tensile force on the full-thread stud reaches the maximum load value, the full-thread stud does not break, and it is determined that the strength of the full-thread stud meets the specified performance requirements.

[0009] Furthermore, the lower end of the fully threaded stud passes through the inner hole of the support pad, and the diameter of the inner hole of the support pad is larger than the diameter of the fully threaded stud.

[0010] The beneficial effects of the present invention are: 1. It can quickly evaluate the bearing capacity of the full-thread stud when it is subjected to bending force;

[0011] 2. If the thread strength is insufficient, the defects on the thread surface will tear open to form crack sources under the multiple wedge load test method. After the test, the thread of the full-thread stud is visually inspected. If crack sources are found at the bottom of the thread teeth, it means that the thread strength of the full-thread stud is insufficient;

[0012] 3. This test method can clearly show the deformation of the full-thread stud after the test. If the thread of the full-thread stud shrinks, that is, the length changes, it means that the overall strength of the full-thread stud is insufficient and does not meet the requirements;

[0013] 4. The present invention can detect manufacturing defects of full-thread studs, provide more accurate performance evaluation of full-thread studs, and detect failure problems at an early stage. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the lower fixture structure.

[0015] 1 is a full-thread stud; 2 is the fixture body; 3 is a threaded wedge pad; 4 is a support pad; 5 is a threaded hole; 6 is a chamfer; 7 is an inner hole of the support pad; W is a bevel angle. DETAILED DESCRIPTION

[0016] The following will be combined with the attached embodiment of the present invention Figure 1 , the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0017] Example 1 Reference Figure 1A wedge load test method for a full-thread stud comprises an upper fixture and a lower fixture, wherein the lower fixture comprises a fixture body 2, a threaded wedge pad 3 and a support pad 4, wherein a threaded cavity is provided in the upper fixture for screwing the thread of the upper end of the full-thread stud 1; a lower cavity is provided in the fixture body, wherein the opening of the lower cavity is a first inclined surface, and the outer wall of the support pad is a second inclined surface matching the first inclined surface, wherein the support pad is provided at the opening of the lower cavity and is passed through by the lower end of the full-thread stud, wherein the lower end of the full-thread stud is located in a threaded hole 5 passing through the threaded wedge pad in the lower cavity, and the threaded wedge pad has an oblique angle W; and a chamfer 6 is provided on the threaded wedge pad;

[0018] S1: Install the upper fixture on the upper beam of the testing machine, and the lower fixture on the lower beam of the testing machine;

[0019] S2: Screw the upper end of the full-thread stud into the upper fixture, the screw-in length shall not be less than the thread diameter of the full-thread stud, and screw the lower end of the full-thread stud into the threaded hole of the threaded wedge after passing through the support pad, the screw-in length shall not be less than the thread diameter of the full-thread stud. At the same time, make sure that the gap length between the upper fixture and the lower fixture is not less than 6 times the pitch length;

[0020] S3: Move the upper beam of the testing machine to subject the full-thread stud to tensile force. At this moment, due to the bevel of the threaded wedge pad, the full-thread stud is subjected to bending force. When the tensile force on the full-thread stud reaches the maximum load value, the full-thread stud does not break, and it is determined that the strength of the full-thread stud meets the specified performance requirements.

[0021] A wedge load test method for a full-thread stud, wherein the lower end of the full-thread stud passes through an inner hole 7 of a support pad, and the diameter of the inner hole of the support pad is larger than the diameter of the full-thread stud.

[0022] A wedge load test method for a fully threaded stud, wherein the hardness of the threaded wedge pad is above HRC45.

[0023] A wedge load test method for a full-thread stud, wherein the hardness of the fixture body and the support pad is above 50HRC.

[0024] A wedge load test method for a full-thread stud, wherein the first thread of a threaded hole of a threaded wedge pad is countersunk to facilitate removal of a broken bolt.

[0025] A wedge load test method for a full-thread stud, wherein the design matching angle of the fixture body and the support pad is mainly used to play an automatic centering role during the wedge load test, so as to avoid the force applied by the test machine being consumed by the fixture body and the support pad during the wedge load test, and not being applied to the full-thread stud body. The inner hole 7 of the support pad is larger than the diameter of the bolt, so as to avoid the full-thread stud being supported by the inner hole of the support pad when subjected to bending stress during the test, thereby consuming the force applied by the test machine.

[0026] A wedge load test method for a full-thread stud, wherein the effective length of the first thread of the threaded hole of the threaded wedge pad is not less than the diameter of the full-thread stud.

[0027] A wedge load test method for a full-thread stud, wherein the bevel angle of a threaded wedge pad is matched according to the diameter of the full-thread stud, wherein when the diameter of the full-thread stud is metric M5 to M24, a threaded wedge pad with a bevel angle of 6° is used.

[0028] A wedge load test method for a full-thread stud, wherein the bevel angle of the thread wedge pad is matched according to the diameter of the full-thread stud, wherein when the diameter of the full-thread stud is greater than M24, a thread wedge pad with a bevel angle of 4° is used.

[0029] A wedge load test method for a fully threaded stud, which can quickly evaluate the load-bearing capacity of the fully threaded stud when the fully threaded stud is subjected to bending force;

[0030] A wedge load test method for a full-thread stud. If the thread strength is insufficient, the defects on the thread surface will tear open to form crack sources under multiple wedge load test methods. After the test, the thread of the full-thread stud is visually inspected. If a crack source is found at the bottom of the thread teeth, it means that the thread strength of the full-thread stud is insufficient.

[0031] A wedge load test method for a full-thread stud. The test method can clearly know the deformation of the full-thread stud after the test. If the thread of the full-thread stud shrinks, that is, the length changes, it means that the overall strength of the full-thread stud is insufficient and does not meet the requirements.

[0032] A wedge load test method for a full-thread stud. The invention can detect manufacturing defects of the full-thread stud, provide more accurate performance evaluation of the full-thread stud, and detect failure problems at an early stage.

[0033] The above are only preferred specific implementation modes of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and inventive concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A wedge load test method for a fully threaded stud, characterized in that: The invention comprises an upper clamp and a lower clamp, wherein the lower clamp comprises a clamp body (2), a threaded wedge pad (3) and a support pad (4), wherein a threaded cavity is arranged inside the upper clamp for screwing the thread of the upper end of a full-thread stud (1); a lower cavity is arranged inside the clamp body, wherein the opening of the lower cavity is a first inclined surface, and the outer wall of the support pad is a second inclined surface matching the first inclined surface, wherein the support pad is arranged at the opening of the lower cavity and is passed through by the lower end of the full-thread stud, wherein the lower end of the full-thread stud is located in the threaded hole (5) in the lower cavity and passes through the threaded wedge pad, and the threaded wedge pad has an oblique angle; S1: Install the upper fixture on the upper beam of the testing machine, and the lower fixture on the lower beam of the testing machine; S2: Screw the upper end of the full-thread stud into the upper fixture, the screw-in length shall not be less than the thread diameter of the full-thread stud, and screw the lower end of the full-thread stud into the threaded hole of the threaded wedge after passing through the support pad, the screw-in length shall not be less than the thread diameter of the full-thread stud. At the same time, make sure that the gap length between the upper fixture and the lower fixture is not less than 6 times the pitch length; S3: Move the upper beam of the testing machine to subject the full-thread stud to tensile force. At this moment, due to the bevel of the threaded wedge pad, the full-thread stud is subjected to bending force. When the tensile force on the full-thread stud reaches the maximum load value, the full-thread stud does not break, and it is determined that the strength of the full-thread stud meets the specified performance requirements.

2. A wedge load test method for a fully threaded stud according to claim 1, characterized in that: The lower end of the full-thread stud passes through the inner hole (7) of the support pad, and the diameter of the inner hole of the support pad is larger than the diameter of the full-thread stud.

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