CN218330974U - Rock direct tensile test device suitable for all compression testing machines - Google Patents

Abstract

The utility model discloses a rock direct tensile test device suitable for all pressure testing machines, which comprises a support frame, a top plate is fixedly arranged on the top of the support frame, a force-bearing plate is arranged above the top plate, and a force-bearing plate is arranged above the support frame. A plurality of vertical dowel bars are arranged on the force plate, and the dowel bars vertically penetrate the top plate and slide with the top plate, and the lower ends of the dowel bars are provided with a stretching base, and the stretching base is provided with There is a lower spherical head holder slidingly matched with the stretching base, the top of the lower spherical head holder is provided with a lower clamping blind groove, and the upper spherical head holder is provided on the top plate slidingly matched with the top board , The bottom of the upper spherical head holder is provided with an upper clamping blind groove, and the center line of the upper clamping blind groove coincides with the center line of the lower clamping blind groove. The utility model reduces equipment cost while ensuring test accuracy, simplifies test operation, and can realize rock tensile tests under various conditions.

Description

Rock Direct Tensile Test Apparatus for All Compression Testing Machines

technical field

The utility model belongs to the technical field of rock direct tensile tests, in particular to a rock direct tensile test device suitable for all pressure testing machines.

Background technique

The testing of three major types of mechanical parameters of rock, such as compression, tension, and shear, is indispensable in all rock engineering constructions. Tensile testing of rock samples is an important means to understand the ability of rocks to bear tensile loads. As one of the basic mechanical parameters in engineering construction, the tensile strength value of rocks is very important for engineering design calculations. At present, there are two main methods for determining the tensile strength of rocks: the indirect stretching method and the direct stretching method.

The indirect tension method is also called the Brazilian split method. Because of its simple operation and wide applicability, it can be completed on all conventional material compression mechanics testing machines. This method is also the only one recommended in the national standard "Engineering Rock Mass Test Method Standard" test method. Although the Brazilian splitting method is generally recommended in ISRM and "Standards for Test Methods of Engineering Rock Mass", the specific test methods are different, and can be divided into direct loading method, pad method and arc loading method.

The method recommended in "Engineering Rock Mass Test Method Standards" is to add a metal pad between the test piece and the indenter, and for soft rock, add a cork pad between the test piece and the indenter, although it is to ensure that the indenter is transmitted to the test head. The end of the component is a linear concentrated load, but the problem of fragility at the end of the brittle rock has not been solved, and the research shows that the tensile strength of the rock obtained by this method is too small.

In ISRM, it is recommended to set the contact between the indenter and the specimen as an arc. Although this method ensures that the end of the specimen is an arc-shaped compression zone, which reduces the risk of the end of the specimen being broken to a certain extent, this method requires The curvature of the indenter needs to match the size of the sample, which is not only not universal, but also leads to high tensile strength. Although this method is simple to operate and can be carried out on all material compression mechanics testing machines, it still has the following shortcomings: (1) The accuracy of the measured tensile strength is still low due to the influence of the end loading zone. (2) During the splitting process, it is difficult to ensure that the splitting surface must be along the predetermined loading surface; (3) It is impossible to ensure that the splitting surface must be the failure surface with the smallest bearing capacity, especially for those with obvious bedding and Defective rock. Therefore, the tensile strength value measured by indirect measurement cannot fully reflect the real situation.

In order to solve the problem that the indirect tensile test results cannot fully reflect the real situation, the direct tensile method is used to test the tensile mechanical properties of rocks. However, the direct tension method has low applicability because it has high requirements on the tensile function of the test equipment, which makes it impossible to use ordinary compression mechanics testing machines for testing. In order to test the tensile mechanical properties of rocks under different conditions, the applicant combined the direct tensile function of the most advanced MTS815 rock mechanics test system in the world to solve some problems in the test, and obtained ZL200610022224.8, US7624647B2, ZL201510068200 respectively .5, ZL201510068186.9, US9488560B2, US9488559B2 and other utility model patents authorized. However, there are still the following deficiencies in the testing of rock mechanical properties by the direct tension method: (1) The performance requirements for the mechanical testing equipment are high, and it is carried out on a conventional material testing machine, so the universality of popularization is low; (2) The MTS815 test The machine is used for direct tensile test. The disassembly and assembly of the loading parts during the test is very cumbersome and requires the cooperation of multiple people. The whole process is time-consuming and laborious. (3) The loading parts that need to be disassembled and assembled are all steel modules, which are large in size and heavy in weight. There are serious safety hazards in the disassembly process that may lead to equipment damage or personal injury; (4) The installation and testing process of direct stretching is relatively cumbersome, requiring at least 2 people to cooperate to complete it, and still requires a lot of labor; (5) Due to the need to use many Stacking of three loading pads and two long loading chains are respectively connected to the 2 tensile ends of the rock, resulting in eccentric tensile force and affecting the test results; (6) rock under triaxial lateral compressive stress cannot be realized The direct tensile test also cannot realize the direct tensile test of the rock under two axially directly applied compressive stresses.

Utility model content

The purpose of this utility model is to provide a rock tensile test device, which can ensure that damage occurs along the part with the lowest bearing capacity of the sample, and reduce the test cost while ensuring measurement accuracy, and can be used for testing under triaxial lateral compression stress. Rock tensile tests as well as rock tensile tests under two axially directly applied compressive stresses.

The purpose of this utility model is achieved in that the rock tensile test device includes a support frame, the top of the support frame is fixedly provided with a top plate, the top of the top plate is provided with a force plate, and the force plate is provided with A plurality of vertical dowel bars, the dowel bars vertically penetrate the top plate and slide with the top plate, and the lower ends of the dowel bars are provided with a stretching base, and the stretching base is provided with a stretching base A lower spherical head holder that slides and fits. The top of the lower spherical head holder is provided with a lower clamping blind groove. The bottom of the head holder is provided with an upper clamping blind groove, and the center line of the upper clamping blind groove coincides with the center line of the lower clamping blind groove.

Further, the support frame includes a base and a plurality of uprights arranged vertically on the base, and the top plate is fixed to the upper part of the uprights by a first fixing nut.

Further, both the base and the top plate are rounded triangles, and there are three columns.

Further, the force plate and the stretching base are in the shape of a rounded triangle, and there are three dowel rods.

Further, the stretch base is fixed to the lower end of the dowel bar through a second fixing nut.

Further, the lower end of the dowel rod is provided with a horizontal connecting rod, and the side wall of the stretch base is provided with an insertion hole, and the connecting rod is inserted into the insertion hole.

Further, the edge of the stretching base is provided with a connecting notch, and the lower end of the dowel bar is provided with a connecting block that matches the connecting notch, and the connecting block is located in the connecting notch and is detachably connected with the stretching base .

Further, the upper clamping blind groove and the lower clamping blind groove are circular holes or rectangular holes.

The beneficial effects of the utility model are: 1. The utility model only needs to have a conventional material testing machine to carry out the rock tensile test, without adding a separate tensile test device, and has wide applicability, overcoming the traditional direct stretching method equipment High cost defects.

2. The utility model adopts the direct stretching method of compression-turning-pulling, which can ensure that the damage occurs along the part with the lowest bearing capacity of the sample, and overcomes the defect of low accuracy of the traditional indirect stretching method.

3. The structure of the device is simple, mainly composed of steel structure. Compared with similar tensile test equipment, the cost is low; the volume is small, the weight is light, and it is easy to move; the operation is convenient and labor-saving, and one person can carry out the test, which reduces the cost of use; It avoids accidental damage to equipment and personal safety of operators due to the disassembly and assembly of heavy loaded parts, with high safety; the compact tensile structure avoids the problem of eccentric force that may exist in the superposition of multiple parts.

4. Due to the compact structure and small size of the utility model, it can be placed inside the pressure chamber of the existing triaxial testing machine, which solves the problem that the direct tensile test of the rock cannot be carried out under the triaxial lateral stress.

5. The utility model adopts a bracket-type compression-turn-tension device, which solves the problem that the direct tensile test of rock cannot be carried out under the direct application of compressive stress in the direction of the two loading axes, and can be directly used in conjunction with the existing true three-dimensional loading test machine , to complete the rock tensile test under the direct application of compressive stress in the direction of two loading axes.

Description of drawings

Fig. 1 is a schematic top view of Embodiment 1;

Fig. 2 is the sectional schematic diagram of I-I of Fig. 1;

The schematic diagram of the front view of Fig. 3 embodiment two;

The schematic diagram of the front view of the third embodiment of Fig. 4;

Reference signs: 1—base; 2—column; 3—top plate; 4—first fixing nut; 5—force plate; 6—dowel rod; 7—stretching base; 8—second fixing nut; 9— Lower spherical head holder; 10—oil pressure protection heat shrinkable film; 11—upper spherical head holder; 12—sample.

detailed description

Below in conjunction with accompanying drawing and embodiment the utility model is further described.

Embodiment one

As shown in Figure 1 and Figure 2, the rock direct tension test device applicable to all pressure testing machines of the present utility model includes a support frame, a top plate 3 is fixedly arranged on the top of the support frame, and a stress plate is arranged above the top plate 3 5. A plurality of vertical dowel bars 6 are arranged on the force plate 5, and the dowel bars 6 vertically penetrate the top plate 3 and slide with the top plate 3, and the lower end of the dowel bars 6 is provided with a stretching base 7, which pulls The stretch base 7 is provided with a lower spherical head holder 9 that slides with the stretch base 7, the top of the lower spherical head holder 9 is provided with a lower clamping blind groove, and the top plate 3 is provided with a sliding fit with the top plate 3. The upper spherical head holder 11, the bottom of the upper spherical head holder 11 is provided with an upper clamping blind groove, and the centerline of the upper clamping blind groove coincides with the centerline of the lower clamping blind groove.

The support frame is used to support other parts, and frames of various structures can be used. Preferably, the support frame includes a base 1 and a plurality of columns 2 vertically arranged on the base 1, and the top plate 3 is fixed to the columns 2 by the first fixing nut 4 the upper part. The base 1 adopts a metal plate with a certain thickness, and the column 2 can adopt a cylindrical metal rod, which can be a hollow tube. The lower end of the upright column 2 can be welded with the base 1, and can also adopt common connection methods such as screw fit. The upper part of the column 2 is provided with an external thread, which can be positioned by setting the first fixing nut 4 on the upper and lower surfaces of the top plate 3, or a supporting step can be set on the outer wall of the upper part of the column 2, and the top plate 3 is placed on the supporting step, and on the upper surface of the top plate 3 A first fixing nut 4 is provided to lock the top plate 3 . The top board 3 is detachably installed, and the top board 3 can be pulled down when moving, which is also convenient for adjusting the height of the top board 3 .

The base 1 and the top plate 3 can be in the shape of a square, a circle, a triangle, etc., as shown in FIG. 1 , preferably a triangle with rounded corners. The number of columns 2 can be 3, 4, etc., preferably 3, so that the top plate 3 can be positioned more stably and fixed better. In addition, a small number of upright columns 2 are used, and the space between the upright columns 2 is larger, so that it is convenient to install other measurement sensors on the rock sample to be tested and reserve an operable space.

The force plate 5 is directly subjected to the compressive load, the force plate 5, the dowel 6 and the tensile base 7 form a tension frame that converts the compressive load into a tensile load, and the upper end of the dowel 6 can be welded to the force plate 5 The connection can also be by means of screw connection, screw connection or positioning pin connection. The force plate 5 and the stretching base 7 can be in the shape of a triangle, a rectangle, etc., preferably a rounded triangle, and there are 3 dowel rods 6, which can realize stable load transmission and prevent the stretching frame from tilting. The lower end of the dowel bar 6 is provided with an external thread, and the stretching base 7 is fixed on the lower end of the dowel bar 6 through the second fixing nut 8 for easy disassembly.

The force plate 5 is located above the top plate 3 , and there is an appropriate distance between the force plate 5 and the top plate 3 , so as to ensure that the force plate 5 can transmit the load to the dowel bar 6 after being subjected to a compressive load. The dowel bar 6 is slidingly fitted with the top plate 3 , and the fit gap is as small as possible to ensure that the compressive load is transmitted vertically downward along the dowel bar 6 .

The lower spherical head holder 9 and the upper spherical head holder 11 are used to clamp the rock sample 12, the lower clamping blind groove and the upper clamping blind groove can fix the sample 12, the lower clamping blind groove and the upper clamping The blind groove can be a circular hole or a square hole, determined according to the shape of the sample 12 .

The lower spherical head holder 9 and the upper spherical head holder 11 are all provided with a hemispherical arc surface, while the top plate 3 is provided with a groove that matches the upper spherical head holder 11 arc surface, stretching the base 7 A groove matching the arc surface of the lower spherical head holder 9 is arranged on the top, so that the lower spherical head holder 9 and the upper spherical head holder 11 can rotate flexibly within a certain angle range. After the sample 12 is processed, it is impossible to completely ensure that the two end faces are perpendicular to the axis of the sample 12. After the lower clamping blind groove and the upper clamping blind groove are respectively bonded to the upper and lower end faces of the sample 12, the axis of the tensile load will be It is impossible to completely coincide with the axis of the sample 12. If there is a certain angle, it will cause eccentric load and affect the test results. After the lower spherical head holder 9 and the upper spherical head holder 11 are provided with a hemispherical arc surface, during the test, if the axis of the tensile load deviates from the axis of the sample 12, the lower spherical head holder 9 and the upper The spherical head holder 11 can automatically rotate under the action of the load, so that the direction of the load is consistent with the axial direction of the sample 12, thereby ensuring the accuracy of the test results.

As shown in Figure 2, both the lower spherical head holder 9 and the upper spherical head holder 11 are limited by the hemispherical arc surface, and the lower spherical head holder 9 and the upper spherical head holder can be easily clamped before and after the test. The holder 11 is removed so that the end face of the sample 12 can be bonded to the bottom of the lower clamping blind groove and the upper clamping blind groove, and the operation difficulty is low. In addition, the lower spherical head holder 9 and the upper spherical head holder 11 for fixing specimens 12 of different shapes and sizes can be replaced, so that the device can be used for tensile tests of specimens 12 of various shapes and sizes .

Embodiment two

As shown in Figure 3, the rock direct tension test device applicable to all pressure testing machines of the present utility model comprises a support frame, a top plate 3 is fixedly arranged on the top of the support frame, and a force plate 5 is arranged above the top plate 3, and A plurality of vertical dowel bars 6 are arranged on the force plate 5, and the dowel bars 6 vertically penetrate the top plate 3 and are slidably matched with the top plate 3, and the lower ends of the dowel bars 6 are provided with a stretching base 7, and the stretching base 7 A lower spherical head holder 9 that slides and fits with the stretching base 7 is arranged on the top, and the top of the lower spherical head holder 9 is provided with a lower clamping blind groove, and the top plate 3 is provided with an upper spherical head that slides with the top board 3 Holder 11, the bottom of the upper spherical head holder 11 is provided with an upper clamping blind groove, the upper clamping blind groove and the lower clamping blind groove are circular holes or rectangular holes, and the center line of the upper clamping blind groove is in line with the The centerlines of the lower clamping blind slots are coincident. The supporting frame includes a base 1 and a plurality of uprights 2 vertically arranged on the base 1 , and a top plate 3 is fixed on the upper part of the uprights 2 by first fixing nuts 4 . Both the base 1 and the top plate 3 are rounded triangles, and there are three columns 2 . The force plate 5 and the stretch base 7 are rounded triangles, and there are three dowel rods 6 .

The lower end of the dowel bar 6 is provided with a horizontal connecting rod, and the side wall of the stretch base 7 is provided with an embedding groove, and the connecting rod is plugged and connected with the embedding hole.

Embodiment three

As shown in Figure 4, the rock direct tensile test device applicable to all pressure testing machines of the present utility model comprises a support frame, a top plate 3 is fixedly arranged on the top of the support frame, and a stress plate 5 is arranged above the top plate 3, and A plurality of vertical dowel bars 6 are arranged on the force plate 5, and the dowel bars 6 vertically penetrate the top plate 3 and are slidably matched with the top plate 3, and the lower ends of the dowel bars 6 are provided with a stretching base 7, and the stretching base 7 A lower spherical head holder 9 that slides and fits with the stretching base 7 is arranged on the top, and the top of the lower spherical head holder 9 is provided with a lower clamping blind groove, and the top plate 3 is provided with an upper spherical head that slides with the top board 3 Holder 11, the bottom of the upper spherical head holder 11 is provided with an upper clamping blind groove, the upper clamping blind groove and the lower clamping blind groove are circular holes or rectangular holes, and the center line of the upper clamping blind groove is in line with the The centerlines of the lower clamping blind slots are coincident. The supporting frame includes a base 1 and a plurality of uprights 2 vertically arranged on the base 1 , and a top plate 3 is fixed on the upper part of the uprights 2 by first fixing nuts 4 . Both the base 1 and the top plate 3 are rounded triangles, and there are three columns 2 . The force plate 5 and the stretch base 7 are rounded triangles, and there are three dowel rods 6 .

The edge of stretching base 7 is provided with connecting notch, and the lower end of dowel 6 is provided with the connecting block that cooperates with connecting notch, and connecting block is positioned at connecting notch and is detachably connected with stretching base 7. Specifically, the connecting block can be connected with the stretch base 7 through connecting pieces such as bolts.

The test method of the rock direct tensile test device applicable to all pressure testing machines can adopt any one of the rock tensile test devices in Embodiments 1 to 3, and one end of the sample 12 is bonded to the lower spherical head by superglue for clamping The lower part of the device 9 clamps the blind groove, and the other end of the sample 12 is bonded to the upper part of the upper spherical head holder 11 to clamp the blind groove by superglue. The section of sample 12 can be circular, also can be various shapes such as rectangle, ellipse, prepare lower spherical head holder 9 and upper spherical head holder 11 according to the shape and size of sample 12. Then put the entire rock tensile test device on the material compression mechanics testing machine, and use the material compression mechanics testing machine to apply a compressive load to the force plate 5, the compressive load is transmitted to the tensile base 7 through the dowel 6, and the tensile base 7 is in the A tensile load is formed on the sample 12, and the magnitude of the tensile load is equal to the compressive load applied by the material compression mechanics testing machine.

The rock direct tensile test device applicable to all pressure testing machines of the utility model converts the compressive load into a tensile load through the tensile frame composed of the force plate 5, the dowel 6 and the tensile base 7. 12 The applied load is equal to the load of the existing direct tensile test, which can ensure that the failure occurs along the part with the lowest bearing capacity of the sample, and overcomes the defect of low accuracy of the traditional indirect tensile method.

In addition, the material compression mechanics testing machine is a conventional test equipment. The compression mechanics tests of various materials are applied by the material compression mechanics testing machine. The equipment structure is simple, the operation threshold is low, and the cost is low. All have the ability to purchase and use, and overcome the defects of high cost and difficult operation of traditional direct tensile test equipment.

In addition, the utility model has the advantages of simple structure, low cost, compact structure and small volume, and can be used in conjunction with various conventional compression mechanics testing machines for various materials to realize rock tensile tests under various conditions.

In addition to the above-mentioned test methods, the rock direct tensile test device applicable to all pressure testing machines of the utility model can also realize rock tensile tests under triaxial lateral pressure conditions, and can cooperate with existing triaxial testing machines , the specific test process is as follows: one end of the sample 12 is bonded to the lower clamping blind groove of the lower spherical head holder 9 by superglue, and the other end of the sample 12 is bonded to the upper spherical head holder by superglue The top of 11 clamps the blind groove. And the oil pressure protection heat shrinkable film 10 is fixed on the outer wall of the lower spherical head holder 9, the sample 12 and the upper spherical head holder 11, as shown in Fig. 2, Fig. 3 or Fig. 4 . Then the whole rock tensile test device is placed on the base inside the pressure chamber of the triaxial testing machine to ensure that the force plate 5 of the rock tensile testing device can be in good contact with the indenter of the triaxial testing machine, and the rock is fixed by bolts. The tensile test apparatus is fixed. By filling the pressure chamber 18 with oil to apply the triaxial lateral compressive stress to the target value, a compressive load is applied to the stressed plate 5 through the testing machine pressure head, and the compressive load is transmitted to the tensile base 7 through the dowel rod 6, and the tensile base 7, a tensile load is formed on the sample 12, and the magnitude of the tensile load is equal to the compressive load applied by the material compression mechanics testing machine; when the sample 12 is destroyed, the oil in the pressure chamber is pumped back.

In addition to the above-mentioned test methods, the rock tensile test device of the present utility model can also carry out direct tensile tests on rocks under two axially directly applied compressive stresses, which solves the problem that the direct tensile test of rocks cannot be directly applied in two axial directions. It is difficult to carry out under compressive stress; and the operation is simple and convenient, and the rock tensile test device of embodiment one, two or three is inserted into the test bed of true three-way loading testing machine to carry out two axially directly applied compressive stresses. The rock tensile test does not require cumbersome disassembly and installation, and only one person can carry out the test, saving manpower and material resources.

The conventional true three-way loading testing machine includes a test bench, and four horizontal support shafts are arranged around the test bench. Two adjacent support shafts are perpendicular to each other. The pressure plate; the top of the test bench is provided with a pressure head.

The specific test process is as follows: prepare a sample 12 with a rectangular cross-section, bond one end of the sample 12 to the lower part of the lower spherical head holder 9 to hold the blind slot with super glue, and glue the other end of the sample 12 to the bottom of the sample 12 with super glue. The upper part of the upper spherical head holder 11 is bonded to hold the blind groove. Then place the entire rock tensile test device on the test bench of the true three-way loading testing machine to ensure that the four sides of the sample 12 correspond to the positions of the four pressure plates, that is, to ensure that each pressure plate can fit the sample 12 One side of the test piece, and then use the press mechanism to apply pressure to the support shaft, and the pressure is transmitted to the sample 12 through the pressure plate. Then use the pressure head of the true three-way loading testing machine to apply a compressive load to the force plate 5, the compressive load is transmitted to the tensile base 7 through the dowel 6, and the tensile base 7 forms a tensile load on the sample 12, and the tensile load is The magnitude of the load is equal to the compressive load applied by the material compression mechanics testing machine. After the sample 12 is broken, the three axial forces of the true three-way loading testing machine are unloaded, and the sample 12 can be taken out.

To sum up, the utility model reduces equipment cost while ensuring test accuracy, simplifies test operation, and can realize rock tensile tests under various conditions.

The above descriptions are only preferred embodiments of the utility model, and are not intended to limit the utility model. For those skilled in the art, the utility model can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present utility model shall be included in the protection scope of the present utility model.

Claims (8)

1. The rock direct tensile test device applicable to all pressure testing machines is characterized in that: it comprises a support frame, and the top of the support frame is fixedly provided with a top plate (3), and a force bearing is arranged above the top plate (3). plate (5), the force plate (5) is provided with a plurality of vertical dowel bars (6), and the dowel bars (6) vertically penetrate the top plate (3) and slide with the top plate (3) fit, and the lower end of the dowel bar (6) is provided with a stretch base (7), and the stretch base (7) is provided with a lower spherical head holder ( 9), the top of the lower spherical head holder (9) is provided with a lower clamping blind groove, and the upper spherical head holder (11) which slides with the top board (3) is provided on the top board (3) , the bottom of the upper spherical head holder (11) is provided with an upper clamping blind groove, and the centerline of the upper clamping blind groove coincides with the centerline of the lower clamping blind groove. 2. The rock direct tensile test device applicable to all pressure testing machines according to claim 1, characterized in that: the support frame includes a base (1) and a plurality of vertical columns vertically arranged on the base (1) (2), the top plate (3) is fixed on the upper part of the column (2) through the first fixing nut (4). 3. the rock direct tensile test device applicable to all pressure testing machines according to claim 2, characterized in that: the base (1) and the top plate (3) are all rounded triangles, and the column (2) For three. 4. The rock direct tensile test device applicable to all pressure testing machines according to claim 1, 2 or 3, characterized in that: the force plate (5) and the tensile base (7) are in a rounded triangle shape , there are three dowel bars (6). 5. The rock direct tensile test device applicable to all pressure testing machines according to claim 1, characterized in that: the tensile base (7) is fixed to the dowel bar (6) by the second fixing nut (8) ) at the lower end. 6. the rock direct tensile test device applicable to all pressure testing machines according to claim 1, characterized in that: the lower end of the dowel bar (6) is provided with a horizontal connecting rod, and the tensile base ( 7) The side wall is provided with an embedding hole, and the connecting rod is plugged and connected with the embedding hole. 7. The rock direct tensile test device applicable to all pressure testing machines according to claim 1, characterized in that: the edge of the tensile base (7) is provided with a connecting notch, and the dowel bar (6 The lower end of ) is provided with the connection block that matches with the connection notch, and the connection block is located in the connection notch and is detachably connected with the stretch base (7). 8. The rock direct tensile test device applicable to all pressure testing machines according to claim 1, characterized in that: the upper clamping blind groove and the lower clamping blind groove are circular holes or rectangular holes.

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