Clamp device for testing shear strength of cutting pick of mining machine

Abstract

The utility model discloses a clamp device for testing cutting pick shear strength of a mining machine, which belongs to the technical field of testing and comprises a support ring, and a permanent magnet is arranged in the support ring. The upper end cover is connected with the supporting ring through a bolt, and an inner hole is formed in the center of the upper end cover; the pressure head is arranged in the inner hole and is in clearance fit with the inner hole; the lower end cover is in threaded connection with the supporting ring, and a rotary permanent magnet is arranged in the center of the interior of the lower end cover; the shearing sample is arranged between the upper end cover and the supporting ring. According to the utility model, the centering property of the clamp and the sample is ensured, the unbalance loading in the test process is avoided, and the accuracy and safety of the test are effectively improved.

Description

Technical Field

[0001] This utility model belongs to the field of testing technology, and specifically relates to a testing fixture device for the shear strength of mining machine cutting teeth. Background Technology

[0002] Mining machine cutting teeth are the main tools for breaking coal seams, consisting of tooth tips (hard alloy) brazed into a tooth body (alloy steel). Due to the different thermophysical parameters of hard alloy and alloy steel, the brazing process results in significant thermal stress. Furthermore, the cutting teeth are constantly subjected to impacts from the hard phases within the coal and rock strata during operation, frequently leading to tooth tip breakage. Therefore, strengthening the performance of the brazed interface of the cutting teeth is particularly urgent. Shear strength is often a key indicator for evaluating interface performance; it refers to the maximum shear stress a material can withstand before slippage or fracture under applied external force, and is commonly used to describe the deformation and fracture characteristics of a material under stress.

[0003] According to the MT / T246-2006 coal industry standard, the shear strength of the brazed surface of the cutting tooth of a mining machine should not be less than 180 MPa. The standard proposes using a stamping failure method to test the shear strength. Before the test, the brazed area of ​​the cutting tooth needs to be cut, and a cross-section is taken to prepare a shear strength test specimen. Matching support blocks and indenter fixtures are also required. During the test, the indenter is placed above the tooth tip at the center of the specimen, and the support block is placed below the alloy steel portion of the specimen. The assembled specimen and its fixture are placed on the worktable of a universal testing machine, which applies a uniform load to the indenter until the tooth tip at the center is pressed down. In actual operation, it is difficult to align the center of the specimen with the center of the fixture, the entire device cannot be fixed on the worktable, and material fracture can occur during loading, resulting in a high risk factor for the test. Utility Model Content

[0004] To solve the above problems, the present invention adopts the following technical solution:

[0005] A testing fixture for the shear strength of cutting teeth in a mining machine includes:

[0006] A support ring, wherein a permanent magnet is disposed within the support ring;

[0007] The upper end cover is connected to the support ring by bolts, and an inner hole is provided at the center of the upper end cover;

[0008] A pressure head, wherein the pressure head is disposed within the inner hole and is clearance-fitted with the inner hole;

[0009] The lower end cover is threadedly connected to the support ring, and a rotating permanent magnet is provided at the center of the lower end cover.

[0010] A shearing specimen is disposed between the upper end cap and the support ring.

[0011] Furthermore, the inner hole of the upper end cap is provided with a wedge-shaped surface that matches the shear specimen at one end near the shear specimen.

[0012] Furthermore, the shearing specimen is constructed by brazing tooth tips into tooth bodies, and a brazing surface is formed at the connection between the tooth tips and the tooth bodies.

[0013] Furthermore, the materials of the indenter, the upper end cap, and the support ring have a hardness greater than that of the shear specimen.

[0014] Furthermore, the lower end cap is connected to the inner ring of the support ring, the height of the support ring is greater than the thickness of the shear sample, and the inner ring diameter of the support ring is greater than the outer diameter of the brazing surface.

[0015] Furthermore, the diameter of the pressure head is smaller than the inner diameter of the brazing surface, and the height of the pressure head is greater than the sum of the thickness of the shearing sample and the thickness of the upper end cap.

[0016] Furthermore, the lower end cover is also provided with a rotating shaft and a rocker arm;

[0017] The rotating permanent magnet is mounted on the rotating shaft, which is rotatably connected to the inner wall of the lower end cover; one end of the rotating shaft passes through the side wall of the lower end cover and is connected to a connector.

[0018] The support ring is provided with a through hole that matches the rocker arm, and the rocker arm passes through the through hole and is detachably connected to the connector.

[0019] Furthermore, the lower end cover is connected to the rotating shaft via a bearing, and a through hole is provided on the outer side wall of the lower end cover near the connector, and the connector is disposed in the through hole;

[0020] The thickness of the connector is less than the height of the through hole.

[0021] Furthermore, the connecting member is a rod, one end of which is fixedly connected to the rotating shaft, and the other end of which is provided with a groove that matches the rocker arm; the rocker arm is clearance-fitted with the groove.

[0022] The beneficial effects of this utility model are:

[0023] 1. This utility model, by setting a clearance fit between the pressure head and the upper end cover, and bolting the support ring and the upper end cover, ensures the alignment of the fixture and the sample by fitting the wedge-shaped surface of the inner cavity of the upper end cover with the sample shape, thus avoiding off-center loading during the test and effectively improving the accuracy and safety of the test.

[0024] 2. This utility model incorporates permanent magnets and rotating permanent magnets in the support ring and lower end cover. During testing, rotating the rocker arm drives the rotating permanent magnet in the lower end cover to rotate until it engages with the permanent magnet in the support ring to form a closed magnetic induction circuit. The generated magnetic field can firmly position the fixture and sample on the worktable of the universal testing machine, ensuring the reliability and accuracy of the test. After the test, the magnetic induction circuit can be disconnected by rotating the rocker arm to demagnetize the sample, making it easier to remove the sample and improving the efficiency of the test. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of a testing fixture device for the shear strength of a mining machine cutting tooth according to the present invention;

[0026] Figure 2 This is a schematic diagram of the shear specimen of this utility model;

[0027] Figure 3 This is a cross-sectional view of the present invention AA;

[0028] Figure 4 This is a schematic diagram of the structure of the upper end cover of this utility model;

[0029] Figure 5 This is a schematic diagram of the structure of the lower end cap and support ring of this utility model;

[0030] Figure 6 This is a schematic diagram of the structure of the lower end cover of this utility model;

[0031] Figure 7 This is a schematic diagram illustrating the magnetization and demagnetization principle of the lower end cover and support ring assembly of this utility model;

[0032] In the figure: 10, shearing specimen; 101, tooth body; 102, brazing surface; 103, tooth tip; 20, indenter; 30, upper end cap; 301, inner hole; 302, bolt step surface; 303, wedge-shaped surface; 40, support ring; 401, discharge chamber; 402, bolt hole; 403, permanent magnet; 404, magnetic induction circuit; 50, lower end cap; 501, rotating permanent magnet; 502, internal thread; 503, rocker arm. Detailed Implementation

[0033] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0034] Example 1

[0035] refer to Figures 1-7 A testing fixture for the shear strength of excavator cutting teeth, comprising:

[0036] Support ring 40, with permanent magnet 403 disposed inside support ring 40;

[0037] The upper end cover 30 is connected to the support ring 40 by bolts, and an inner hole 301 is provided at the center of the upper end cover 30.

[0038] The pressure head 20 is disposed inside the inner hole 301 and is clearance-fitted with the inner hole 301.

[0039] The lower end cover 50 is threadedly connected to the support ring 40, and a rotating permanent magnet 501 is provided at the center of the lower end cover 50.

[0040] Shear specimen 10 is placed between the upper end cover 30 and the support ring 40.

[0041] In this embodiment, the upper end cover 30 and the support ring 40 are provided with bolt holes 402, and the bolt holes 402 of the upper end cover 30 are provided with bolt step surfaces 302 away from the support ring 40.

[0042] In this embodiment, five bolt holes 302 are provided, and the five bolt holes 302 are evenly distributed on the upper end cover 30 and the support ring 40.

[0043] Preferably, the inner hole 301 of the upper end cover 30 is provided with a wedge-shaped surface 303 that matches the shear specimen 10 at one end.

[0044] In this embodiment, the wedge-shaped surface 303 of the upper end cap 30 is used to clamp the side slope of the shear specimen 10, and the upper surface of the support ring 40 is used to support the entire shear specimen 10.

[0045] Preferably, the shearing sample 10 is formed by brazing the tooth tip 103 into the tooth body 101, and a brazing surface is formed at the connection between the tooth tip 103 and the tooth body 101.

[0046] In this embodiment, one end of the tooth body 101 has a U-shaped structure; the tooth tip 103 is embedded in the tooth body 101 and connected to the tooth body 101 by brazing; wherein, the brazing surface 102 should have good filling degree and avoid cracks.

[0047] Preferably, the materials of the pressure head 20, the upper end cap 30, and the support ring 40 have a hardness greater than that of the shear specimen 10.

[0048] Preferably, the lower end cap 50 is connected to the inner ring of the support ring 40, the height of the support ring 40 is greater than the thickness of the shear sample 10, and the inner ring diameter of the support ring 40 is greater than the outer diameter of the brazing surface 102.

[0049] In this embodiment, the inner ring of the support ring forms a discharge cavity 401, the height of which is greater than the thickness of the sheared sample 10; the height of the support ring 40 is greater than the thickness of the sheared sample 10, and with the space reserved for the end cap 50, space can be provided for multiple shearing of the tooth tip 103; the inner diameter of the support ring 40 is greater than the outer diameter of the brazing surface 102, ensuring that the tooth tip 103 can be pressed down smoothly.

[0050] In this embodiment, the outer surface of the lower end cover 50 is provided with threads, and the inner ring of the support ring 40 is provided with an internal thread 502 that matches the threads.

[0051] Preferably, the diameter of the pressure head 20 is smaller than the inner diameter of the brazing surface 102, and the height of the pressure head 20 is greater than the sum of the thicknesses of the shear sample 10 and the upper end cap 30.

[0052] Preferably, the lower end cover 50 is also provided with a rotating shaft and a rocker arm 503;

[0053] A rotating permanent magnet 501 is mounted on a rotating shaft, which is rotatably connected to the inner wall of the lower end cover 50; one end of the rotating shaft passes through the side wall of the lower end cover 50 and is connected to a connector.

[0054] The support ring 40 is provided with a through hole that matches the rocker arm 503, through which the rocker arm 203 is detachably connected to the connector.

[0055] Preferably, the lower end cover 50 is connected to the rotating shaft via a bearing, and a through hole is provided on the outer side wall of the lower end cover 50 near the connector, with the connector disposed inside the through hole;

[0056] The thickness of the connector is less than the height of the through hole.

[0057] Preferably, the connecting member is a rod, one end of which is fixedly connected to the rotating shaft, and the other end of which is provided with a groove that matches the rocker arm 503; the rocker arm 503 is clearance-fitted with the groove.

[0058] In this embodiment, the groove is a polygonal groove, preferably a hexagonal groove.

[0059] In this embodiment, during the test, the rocker arm 503 drives the rotating permanent magnet 501 until it cooperates with the permanent magnet 403 to form a closed magnetic induction circuit 404. The generated magnetic field can firmly position the fixture and the shear sample 10 on the worktable of the universal testing machine, ensuring the reliability and accuracy of the test. After the test, the magnetic induction circuit 404 can be disconnected by turning the rocker arm 503 to demagnetize the sample, making it easier to remove the shear sample 10 and improving the efficiency of the test.

[0060] Working principle: The tooth tip is brazed and embedded into the tooth body to create a finished cutting tooth. A circular shearing sample is then cut out from the brazed surface of the cutting tooth. The inclined structure of the shearing sample is placed tightly against the wedge-shaped surface of the upper end cap, and the bottom surface of the shearing sample is placed on the support ring. By tightening the bolts, the upper end cap and the support ring are automatically aligned and clamped. Then, the lower end cap is tightened and fixed to the inner wall of the support ring with threads. At the same time, the connecting piece is aligned with the through hole, and the rocker arm is installed, so that the clamping device and the sample become a whole. Place the entire assembly on the worktable of the universal testing machine. Once the position is determined, move the rocker arm to generate a magnetic field, firmly positioning the assembly on the worktable. Then, insert the indenter into the inner hole of the upper end cover. Apply a downward load to the indenter using the universal testing machine, causing the tooth tip to press down and detach from the shear specimen. Record the maximum value during the loading process. Combined with the diameter and height of the brazed surface, the final shear strength value can be obtained. The shear specimen can be replaced by adjusting the tightness of the bolts to conduct multiple shear tests. After the test is completed, the rocker arm can be moved again to demagnetize the assembly, and the entire fixture can be removed from the worktable.

[0061] The above description is merely a preferred embodiment of this utility model and is not intended to limit the scope of this utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this utility model are included within the protection scope of this utility model.

Claims

1. A testing fixture for the shear strength of cutting teeth in a mining machine, characterized in that, include: A support ring, wherein a permanent magnet is disposed within the support ring; The upper end cover is connected to the support ring by bolts, and an inner hole is provided at the center of the upper end cover; A pressure head, wherein the pressure head is disposed within the inner hole and is clearance-fitted with the inner hole; The lower end cover is threadedly connected to the support ring, and a rotating permanent magnet is provided at the center of the lower end cover. A shearing specimen is disposed between the upper end cap and the support ring.

2. The testing fixture device for the shear strength of mining machine cutting teeth according to claim 1, characterized in that, The inner hole of the upper end cap has a wedge-shaped surface that matches the shear specimen at one end.

3. The testing fixture device for the shear strength of mining machine cutting teeth according to claim 1, characterized in that, The shearing specimen is formed by brazing tooth tips into tooth bodies, and a brazing surface is formed at the connection between the tooth tips and the tooth bodies.

4. The testing fixture device for the shear strength of mining machine cutting teeth according to claim 1, characterized in that, The materials of the indenter, the upper end cap, and the support ring have a hardness greater than that of the shear specimen.

5. The testing fixture device for the shear strength of mining machine cutting teeth according to claim 3, characterized in that, The lower end cap is connected to the inner ring of the support ring. The height of the support ring is greater than the thickness of the shear sample, and the inner ring diameter of the support ring is greater than the outer diameter of the brazing surface.

6. The testing fixture device for the shear strength of mining machine cutting teeth according to claim 3, characterized in that, The diameter of the pressure head is smaller than the inner diameter of the brazing surface, and the height of the pressure head is greater than the sum of the thickness of the shearing sample and the thickness of the upper end cap.

7. The testing fixture device for the shear strength of mining machine cutting teeth according to claim 1, characterized in that, The lower end cover is also provided with a rotating shaft and a rocker arm; The rotating permanent magnet is mounted on the rotating shaft, which is rotatably connected to the inner wall of the lower end cover; one end of the rotating shaft passes through the side wall of the lower end cover and is connected to a connector. The support ring is provided with a through hole that matches the rocker arm, and the rocker arm passes through the through hole and is detachably connected to the connector.

8. A testing fixture device for the shear strength of a mining machine cutting tooth according to claim 7, characterized in that, The lower end cover is connected to the rotating shaft via a bearing. A through hole is provided on the outer side wall of the lower end cover near the connector, and the connector is disposed in the through hole. The thickness of the connector is less than the height of the through hole.

9. A testing fixture device for the shear strength of a mining machine cutting tooth according to claim 8, characterized in that, The connecting member is a rod, one end of which is fixedly connected to the rotating shaft, and the other end of which is provided with a groove that matches the rocker arm; the rocker arm is clearance-fitted with the groove.

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