A device for testing the shearing strength of a bolt for a metal fitting

Abstract

The utility model relates to bolt shear strength test technical field, concretely is a kind of hardware bolt shear strength test device, including the support pedestal of U shape, the support pedestal includes the base portion of entity, a pair of ear-shaped ear plate portion is symmetrically arranged on the base portion, the center of each ear plate portion is processed and is provided with mounting hole, the quenching sleeve is installed and arranged between two mounting holes, and the inner hole of quenching sleeve is used for loading bolt;The inner hole diameter of quenching sleeve is compatible with the nominal diameter of bolt unthreaded section, and shear clamp is embedded between two ear plate portions.The hardware bolt shear strength test device can realize the shear strength test of hardware bolt of different performance grades and different diameter specifications without frequently replacing test fixture, solves the technical problem that test cost increases and operation process is complicated in the shear strength test of different existing bolts, which needs to replace different fixtures.

Description

Technical Field

[0001] This utility model relates to the field of bolt shear strength testing technology, specifically a device for testing the shear strength of hardware bolts. Background Technology

[0002] Bolts are key components in electrical fittings used to connect and fix equipment. For each batch of bolts purchased for production, samples must be taken and shear tests must be performed as required to verify whether the shear strength of the bolts meets the design requirements.

[0003] The shear strength requirements for bolts of different performance grades are as follows: Grade 4.8 bolts: shear strength not less than 260 MPa; Grade 5.8 bolts: shear strength not less than 320 MPa; Grade 6.8 bolts: shear strength not less than 370 MPa; Grade 8.8 bolts (d≤16mm): shear strength not less than 490 MPa; Grade 8.8 bolts (d>16mm): shear strength not less than 510 MPa; Grade 10.9 bolts: shear strength not less than 640 MPa.

[0004] The theoretical calculation of shear strength is derived from 0.62Rm,min, where the minimum shear load = nominal stress area of ​​the thread × minimum shear strength. Different shear strength requirements apply to bolts of different performance grades. Currently, different test fixtures are required for shear strength tests on different bolts, significantly increasing testing costs and complexity. Utility Model Content

[0005] (a) Technical problems to be solved

[0006] To address the shortcomings of existing technologies, this utility model provides a shear strength testing device for fitting bolts, which can eliminate the need for frequent changes of test fixtures when conducting shear strength tests on fitting bolts of different performance grades and diameters. This solves the technical problem of increased testing costs and cumbersome operation procedures caused by the need to change different fixtures in existing shear strength tests for different bolts.

[0007] (II) Technical Solution

[0008] To achieve the above objectives, this utility model provides the following technical solution: a shear strength testing device for metal fittings and bolts, comprising a U-shaped support base, the support base including a solid base portion, a pair of ear-shaped ear plates symmetrically arranged on the base portion, each ear plate portion having a mounting hole machined at its center, a hardened sleeve being installed through the two mounting holes, the inner hole of the hardened sleeve being used to insert a bolt; the inner diameter of the hardened sleeve being adapted to the nominal diameter of the unthreaded section of the bolt, and a shearing clamp being embedded between the two ear plates.

[0009] Furthermore, the hardened sleeve is a ring-shaped high-strength steel part and has various specifications, and different specifications of the hardened sleeve are matched according to different specifications of bolts.

[0010] Furthermore, the bottom surface of the support base is in contact with the upper support platform of the external universal testing machine, providing a stable support platform for the shear test.

[0011] Furthermore, the shearing fixture is a T-shaped cuboid block structure, which is embedded in the gap between the two ear plates along the vertical direction of the support base; the upper surface of the shearing fixture is in contact with the lower pressure platform of the external universal testing machine, and the semi-circular concave surface machined at its lower part is in contact with the unthreaded section of the bolt. The lower pressure platform of the universal testing machine applies a load downward, transmitting the pressure downward to the unthreaded section of the bolt to form a shearing force.

[0012] Furthermore, the gap between the two ear plates where the shearing clamp is vertically embedded is ≤0.15mm.

[0013] Furthermore, the lower semi-circular concave surface of the shearing fixture and the unthreaded section of the bolt constitute the shearing section, and the length of the unthreaded portion of the bolt outside the shearing section is ≥1 times the bolt diameter; at the same time, the interval between the shearing surfaces on both sides of the shearing section is ≥2 times the bolt diameter.

[0014] (III) Beneficial Effects

[0015] Compared with the prior art, this utility model provides a device for testing the shear strength of hardware bolts, which has the following advantages:

[0016] 1. The bottom surface of the support base is in contact with the upper support platform surface of the universal testing machine, providing a stable support foundation for the testing device. This effectively avoids load transmission deviation caused by unstable support during the test and improves the accuracy of the test data.

[0017] 2. The shearing fixture is fitted between the two lugs with a gap of ≤0.15mm, which ensures that the downward pressure load can be accurately transmitted to the shearing part of the bolt without threads. At the same time, the design of the length of the unthreaded part outside the shearing section being ≥1 times the bolt diameter and the shearing surface interval being ≥2 times the bolt diameter effectively avoids the influence of the force on the non-shearing section of the bolt on the test results, making the test more consistent with the actual shear stress state of the bolt. Attached Figure Description

[0018] Figure 1 These are the front and left views of a hardware bolt shear strength testing device according to this utility model;

[0019] Figure 2 for Figure 1 Front and left views after the bolts are inserted;

[0020] Figure 3 for Figure 2 Sectional view of the front view;

[0021] Figure 4 for Figure 3 A cross-sectional view of the bolt being cut by pressing down the shearing fixture;

[0022] In the figure: 1. Support base; 101. Base part; 102. Ear plate part; 103. Mounting hole; 104. Hardened sleeve; 2. Bolt; 3. Shearing fixture; 4. Shearing section; 5. Shearing surface. Detailed Implementation

[0023] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0024] Please see Figure 1-4 A device for testing the shear strength of metal fittings and bolts is characterized by comprising a U-shaped support base 1. The support base 1 is made of a robust material, and its main body is a solid rectangular base portion 101, which provides stable foundation support. On both sides of the upper surface of the base portion 101, a pair of upwardly extending, ear-shaped ear plates 102 are symmetrically arranged, parallel to each other and spaced a certain distance apart. Each ear plate portion 102 has a precisely machined mounting hole 103 at its center along its thickness direction, and the two mounting holes 103 are coaxially aligned. A hardened sleeve 104 is installed through these two coaxial mounting holes 103 and is securely fixed. The inner hole of the hardened sleeve 104 is used to insert the bolt 2 to be tested; the diameter of this inner hole is precisely designed to match the nominal diameter of the unthreaded section (polished section) of the bolt 2, ensuring a tight fit and no wobble within the hole. A shearing clamp 3 is tightly fitted into the gap between the two ear plate portions 102, providing a guiding space for the vertical movement of the shearing clamp 3. The hardened sleeve 104 is a ring-shaped high-strength steel part, which is usually heat-treated to obtain high hardness and wear resistance, and has a variety of inner diameter specifications, so that different specifications of the hardened sleeve 104 can be selected to match the shank diameter of different specifications of bolts 2, ensuring the versatility and accuracy of the test.

[0025] In the above embodiment, the bottom surface of the support base 1 is flat and directly contacts the upper support platform of the external universal testing machine, providing a stable and reliable rigid support platform for the entire shearing test process. The shearing fixture 3 is a T-shaped cuboid block structure, usually made of high-strength alloy tool steel. Its main body is precisely fitted into the gap between the two ear plate portions 102 along the vertical direction of the support base 1. The mating clearance between the two sides of the shearing fixture 3 and the inner sides of the two ear plate portions 102 is ≤0.15mm, to ensure that it can only move smoothly in the vertical direction without lateral swaying. The upper surface of the shearing fixture 3 is flat and directly contacts the lower pressure platform of the external universal testing machine. A precise semi-circular concave surface is machined on its lower part, which contacts the outer surface of the unthreaded section of the bolt 2, i.e., the smooth section, placed inside the hardened sleeve 104. When the universal testing machine is started, its downward pressing platform applies a load downward at a uniform speed. This pressure is transmitted downward through the shearing fixture 3 and ultimately acts on the unthreaded section of the bolt 2 to form a shear force. The contact area between the lower semi-circular concave surface of the shearing fixture 3 and the unthreaded section of the bolt 2 constitutes the shearing section 4. To ensure that shear failure occurs in this predetermined area and to reduce the influence of end effects, the length of the unthreaded portion of the bolt 2 outside the shearing section 4, i.e., the smooth section, should be ≥1 times the nominal diameter of the bolt. At the same time, the interval between the shearing surfaces 5 on both sides of the shearing section 4, i.e., the theoretical shear initiation lines formed by the contact between the cutting edges on both sides of the concave surface of the shearing fixture and the bolt, should be ≥2 times the nominal diameter of the bolt to ensure the formation of a sufficient pure shearing area.

[0026] The working principle of the above embodiments is as follows:

[0027] In use, firstly, select a hardened sleeve 104 with an inner diameter corresponding to the nominal diameter of the smooth section of the bolt 2 to be tested, and install it into the coaxial mounting holes 103 of the ear plates 102 on both sides of the support base 1 and fix it; then, insert the unthreaded section of the bolt 2 into the inner hole of the hardened sleeve 104, adjust the position of the bolt 2 so that the shearing section 4 is located in the middle position between the two ear plates 102, and the length of the smooth section other than the shearing section 4 is ≥ 1 times the nominal diameter of the bolt; then, insert the shearing fixture 3 vertically into the gap between the two ear plates 102, ensuring that the fit clearance between its two sides and the inner side of the ear plates is ≤ 0.15mm, and at the same time, make the semi-circular concave surface of the lower part of the shearing fixture 3 tightly fit with the outer surface of the smooth section of the bolt 2; then, place the bottom surface of the support base 1 flat on the upper support platform of the universal testing machine, so that the upper surface of the shearing fixture 3 is aligned and in contact with the lower pressure platform of the testing machine; start the universal testing machine, set the uniform loading parameters, and slowly apply the load downwards on the lower pressure platform (e.g. Figure 3-4(The downward arrow indicates the direction of the applied load). The load is transmitted to the bolt 2 through the shearing fixture 3, forming a pure shear force in the shearing section 4. As the load increases, the shearing section 4 of the bolt 2 gradually undergoes plastic deformation until it breaks along the shearing surface 5, i.e., the theoretical shear line where the cutting edges on both sides of the concave surface of the shearing fixture contact the bolt. At this time, the testing machine automatically records the maximum load value at the time of failure. After the test, the testing machine is turned off, the damaged bolt 2 is removed, and the debris on the surface of the hardened sleeve 104 and the shearing fixture 3 is cleaned. If it is necessary to test bolts of different specifications, the above operation can be repeated after replacing the hardened sleeve 104 with the corresponding inner diameter.

[0028] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0029] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A device for testing the shear strength of metal fittings and bolts, characterized in that: The system includes a U-shaped support base (1), which includes a solid base portion (101). A pair of ear-shaped ear plates (102) are symmetrically arranged on the base portion (101). Each ear plate portion (102) has a mounting hole (103) machined at its center. A hardened sleeve (104) is installed through the two mounting holes (103). The inner hole of the hardened sleeve (104) is used to insert a bolt (2). The inner diameter of the hardened sleeve (104) is adapted to the nominal diameter of the unthreaded section of the bolt (2). A shearing clamp (3) is embedded between the two ear plate portions (102).

2. The device for testing the shear strength of hardware bolts according to claim 1, characterized in that: The hardened sleeve (104) is a ring-shaped high-strength steel part and has various specifications. The hardened sleeve (104) of different specifications is matched with bolts (2) of different specifications.

3. The device for testing the shear strength of hardware bolts according to claim 1, characterized in that: The bottom surface of the support base (1) is in contact with the upper support platform of the external universal testing machine, providing a stable support platform for the shear test.

4. The device for testing the shear strength of hardware bolts according to claim 1, characterized in that: The shearing fixture (3) is a T-shaped cubic block structure, which is embedded in the gap between the two ear plates (102) along the vertical direction of the support base (1); the upper surface of the shearing fixture (3) is in contact with the lower pressure platform of the external universal testing machine, and the semi-circular concave surface machined at its lower part is in contact with the unthreaded section of the bolt (2). The lower pressure platform of the universal testing machine applies a load and transmits the pressure downward to the unthreaded section of the bolt (2) to form a shearing force.

5. The device for testing the shear strength of hardware bolts according to claim 4, characterized in that: The shearing clamp (3) is vertically fitted between the two ear plate portions (102) with a gap of ≤0.15mm.

6. The device for testing the shear strength of hardware bolts according to claim 4, characterized in that: The lower semi-circular concave surface of the shearing fixture (3) and the unthreaded section of the bolt (2) form the shearing section (4). The length of the unthreaded portion of the bolt (2) outside the shearing section (4) is ≥ 1 times the bolt diameter. At the same time, the interval between the shearing surfaces (5) on both sides of the shearing section (4) is ≥ 2 times the bolt diameter.

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