Wedge-shaped tensile fixture, tensile testing equipment and tensile testing method including the same

Abstract

The present invention discloses a wedge-shaped tensile fixture, a tensile testing device and a tensile testing method including the same. The fixture includes a screw, a first nut, a chuck, a chuck head and a jaw. The lower end of the screw is connected to a top plate. The first nut screwed onto the screw is provided with an annular groove. The chuck is sleeved below the first nut of the screw. One end of a hook is fixed to the chuck and the other end is inserted into the annular groove. The chuck is provided with N first elliptical holes. The chuck head includes a top plate and a column. The top plate is provided with N second elliptical holes. The column is provided with a receiving cavity. The receiving cavity is provided with N wedge-shaped grooves. Each jaw includes a straight rod and a slider. The slider slides in engagement with the groove. The lower end of the straight rod abuts against the upper end of the slider. The straight rod passes through the two elliptical holes and is screwed onto the end that passes through the first elliptical hole. The portion of the straight rod within the receiving cavity has a shoulder. An elastic element is sleeved between the shoulder and the chuck. The present invention can reduce the phenomenon of specimen fracture in the fixture caused by torsion during testing.

Description

Technical Field

[0001] The present invention relates to the technical field of tensile testing, in particular to a wedge-shaped tensile fixture, a tensile testing device comprising the same, and a tensile testing method. Background Art

[0002] Measuring the tensile strength of materials is a common practice in the construction and building materials industry. This is particularly true in the field of refractory materials, where anchor bricks are the primary brick type used in heating furnace roof construction. The suspended construction method determines the ability of anchor bricks to withstand tensile forces at both ends, making them a crucial quality and safety indicator.

[0003] During laboratory testing, the two ends of the specimen are fixed with a clamp and stretched at a constant rate. The ratio of the maximum breaking force to the broken cross-sectional area is used as the final tensile strength value.

[0004] During the experiment, ensure that the upper and lower clamps are aligned perpendicular to the specimen, with no external forces acting in other directions. Also, disperse the forces acting at the clamping locations to minimize stress concentration. Also, ensure that the slider and specimen are properly clamped to prevent the specimen from slipping.

[0005] At present, there are various problems with the tensile test fixtures of inorganic non-metallic materials in China, such as: slippage of the contact surface between the fixture and the sample; breakage of the sample at the fixture mouth; jamming of the spring inside the fixture, etc. Summary of the Invention

[0006] In order to eliminate the problems encountered in the above experiments and improve the accuracy and reliability of the measurement data, the present invention discloses a wedge-shaped tensile fixture, comprising:

[0007] The screw, the lower end of which is coaxially connected to the top plate of the chuck as a whole;

[0008] a first nut, the first nut being screwed onto the screw rod, and having an annular groove arranged along a circumferential direction thereof;

[0009] A chuck having a through hole at its center for the screw to pass through, the chuck being sleeved below the first nut of the screw through the through hole, at least two hooks being provided on the chuck, one end of each hook being fixed to the chuck, and the other end of each hook being inserted into the annular groove, and N first elliptical holes being further provided on the chuck, and the major axis of each first elliptical hole being arranged along the radial direction of the chuck;

[0010] A chuck is located below the chuck, and includes a top plate and a column coaxially connected to the lower end of the top plate. The top plate is provided with N second elliptical holes, and the major axis of each second elliptical hole is arranged along the radial direction of the chuck. The lower end of the column is open, and a receiving cavity is provided in the column coaxial with the column. N wedge-shaped grooves extending obliquely along the axial direction are evenly arranged in the circumferential direction in the receiving cavity, and the wedge-shaped grooves gradually extend radially inward in the direction away from the top plate;

[0011] N claws, each claw includes a straight rod and a slider, the lower end of the straight rod abuts against the upper end surface of the slider, the slider slides in cooperation with the wedge-shaped groove, the upper end of the straight rod has an external thread, the straight rod passes through the second elliptical hole and the first elliptical hole from bottom to top, and a second nut is screwed on the end of the straight rod that passes through the first elliptical hole, the portion of the straight rod located in the accommodating cavity has an annular shoulder, and an elastic element is sleeved between the annular shoulder and the lower end surface of the chuck,

[0012] Where N is a constant greater than or equal to 4,

[0013] The second nut is held above the chuck, and the elastic element is held below the chuck.

[0014] Preferably, N is 4.

[0015] Preferably, the surface of the slider in contact with the sample is in the form of a rough surface.

[0016] Preferably, the hook includes a first right-angled side and a third right-angled side bent at right angles in opposite directions from both ends of the second right-angled side.

[0017] Preferably, the included angle between the wedge-shaped groove and the axis of the chuck is 7-8°.

[0018] Preferably, the elastic element is a spring.

[0019] The present invention also discloses a tensile testing device, comprising the two wedge-shaped tensile clamps described above and a tensile testing machine, wherein the wedge-shaped tensile clamps are respectively mortised with a pair of tensile mechanisms of the tensile testing machine via screw rods.

[0020] The present invention also discloses a tensile test method, using the two wedge-shaped tensile fixtures described above, and performing the following steps:

[0021] Place one end of the specimen between N sliders of one fixture, rotate the first nut so that the slider clamps the outer circumference of the one end of the specimen, and place the other end of the specimen between N sliders of another fixture, rotate the first nut so that the slider clamps the outer circumference of the other end of the specimen;

[0022] Connect the screw rods of the two clamps to the corresponding stretching mechanisms respectively;

[0023] The tensile test is carried out by stretching the specimen to both sides through the tensile mechanism.

[0024] The wedge-shaped tensile fixture of the present application, as well as the tensile testing equipment and tensile testing method including the same, have the following beneficial technical effects:

[0025] (1) Since the first nut can drive the jaws to move the specimen evenly up and down, and the wedge-shaped groove can ensure that the tensile force on the specimen is in the same direction as the specimen axis, there will be no torsion that causes the specimen to break in the fixture;

[0026] (2) When the strength of the low-strength specimen is not known in advance, the pre-tightening force is slowly and slightly applied by the elastic force of the spring to clamp the specimen, ensuring that the low-strength specimen will not be damaged by the artificial pre-tightening force;

[0027] (3) Moreover, for high-strength specimens, the clamping is tightened during the loading process, which effectively prevents the specimen from slipping due to insufficient prestressing. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The above features and technical advantages of the present invention will become clearer and easier to understand by describing its embodiments in conjunction with the following drawings.

[0029] Figure 1 is a schematic diagram showing a wedge-shaped tensile fixture according to an embodiment of the present invention;

[0030] Figure 2 is a schematic diagram showing a first nut according to an embodiment of the present invention;

[0031] Figure 3 is a schematic diagram showing a chuck according to an embodiment of the present invention;

[0032] Figure 4 1 is a bottom view of a column of a chuck according to an embodiment of the present invention;

[0033] Figure 5 is a schematic diagram showing the connection between a wedge-shaped tensile fixture and a tensile testing machine according to an embodiment of the present invention;

[0034] Figure 6 Schematic diagram showing the steps of a tensile test method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0035] The following describes embodiments of the wedge-shaped tensile grip, a tensile testing apparatus including the same, and a tensile testing method according to the present invention with reference to the accompanying drawings. Those skilled in the art will recognize that the described embodiments may be modified in various ways or combinations thereof without departing from the spirit and scope of the present invention. Therefore, the drawings and description are illustrative in nature and are not intended to limit the scope of the claims. Furthermore, throughout this specification, the drawings are not drawn to scale, and like reference numerals represent like parts.

[0036] like Figure 1 As shown, the wedge-shaped tensile fixture of this embodiment includes a screw rod 1, a first nut 2 (such as Figure 2 As shown in the figure, the hook 3, the chuck 4, the chuck head 5, and the four claws 7 are provided. The first nut 2 has an internal thread, and the screw 1 has an external thread that matches the first nut 2. The first nut 2 is screwed onto the screw 1. The first nut has a first cylindrical body 21 and a second cylindrical body 22 that are coaxially connected. The second cylindrical body 22 is located at the lower end of the first cylindrical body 21. An annular groove 221 is provided on the second cylindrical body 22 along the circumference. The chuck 4 has a through hole in the center. The screw 1 passes through the through hole 43 of the chuck 4, so that the chuck 4 is concentrically located below the first nut 2.

[0037] At least two hooks 42 are also provided on the chuck 4, preferably four hooks 42 are evenly provided along the circumference. The hooks 42 are in the shape of right-angle bends, specifically, two consecutive right-angle bends with opposite bend directions. Figure 1 As shown, the hook includes a first right-angled edge 421, a second right-angled edge 422, and a third right-angled edge 423. The third right-angled edge 423 of the hook is fixedly connected to the chuck 4, which can be fixed to the upper end surface of the chuck 4 by bolts, and the first right-angled edge 421 is inserted into the annular groove 221 on the second cylindrical body 22. This allows the chuck 4 to move axially during the rotation of the first nut 2.

[0038] And, as Figure 3 As shown, four first elliptical holes 41 are provided on the chuck 4 so that the straight rod 71 of the clamping jaw 7 passes through the first elliptical holes 41. In addition, the major axis of the first elliptical holes 41 is arranged along the radial direction of the chuck 4.

[0039] The chuck 5 is located below the chuck 4 and includes a top plate 51 and a column 52 coaxially connected to the lower end of the top plate 51. The lower end of the screw 1 and the top plate 51 of the chuck 5 are connected as a whole by welding. Of course, other connection methods such as riveting, threaded connection, flange connection, etc. can also be used.

[0040] Four second elliptical holes (not shown) are provided on the top plate 51 so that the straight rod 71 of the clamping claw 7 can pass through the second elliptical holes. Moreover, the long axis of the second elliptical holes is arranged along the radial direction of the clamping head 5. Figure 1 、 Figure 4 As shown, the lower end of the column 52 is not closed, and a receiving cavity 521 is defined within the column 52, which is coaxial with the column 52. Furthermore, four wedge-shaped grooves 522 are arranged circumferentially at 90-degree intervals within the receiving cavity 521. The wedge-shaped grooves 522 form a certain angle with the axis along the radial direction, and gradually extend radially inward as they move away from the top plate. In other words, the wedge-shaped grooves form a certain angle with the axis, preferably 7-8 degrees.

[0041] The jaw 7 comprises a split straight rod 71 and a slider 72. The lower portion of the straight rod 71 abuts against the upper end surface of the slider 72. The slider 72 is embedded in the wedge-shaped groove 522 within the chuck 5, and the contact surface is preferably smooth. The upper end of the straight rod 71 is externally threaded. The straight rod 71 passes through the four second elliptical holes of the chuck 5 and the four first elliptical holes 41 of the chuck 4 from bottom to top. The end of the straight rod 71 that passes through the first elliptical hole 41 is fastened with a second nut. The second nut is larger than the first elliptical hole 41 to prevent the second nut from being positioned above the chuck 4.

[0042] A claw sleeve 711 is sleeved on the straight rod 71, and a spring 712 is sleeved above the claw sleeve 711. The lower end of the straight rod 71 abuts the slider 72, and the upper end of the claw sleeve 711 abuts the bottom of the spring 712. The spring 712 passes through the second elliptical hole and the top of the spring abuts the lower surface of the chuck 4. Of course, an annular shoulder can also be directly processed into an integral part on the support rod 71, and the annular shoulder is used to abut the bottom of the spring 712. In addition, the spring can also be replaced by an elastic element such as an elastic pad. Among them, the size of the spring 712 is larger than the size of the first elliptical hole 41, so that the lower surface of the chuck 4 can contact the upper end of the spring 712, and the spring 712 does not pass through the first elliptical hole 41.

[0043] The fixture of this embodiment can make the sample into a cross section of 35±5mm during the test. 2 , a cube with a length of 230 mm ± 50 mm. Of course, the sample is not limited to this size; this is merely an example. Screw the first nut 2 onto the upper portion of the screw 1. Since the first nut 2 is connected to the chuck 4 (without internal threads) by a hook, the rotation of the first nut 2 drives the chuck 4 axially. Furthermore, as the first nut 2 moves upward, the chuck 4 pulls the second nut 25 upward, which in turn drives the jaw 7 upward.

[0044] In the experiment, two clamps as described above are used to clamp the two ends of the sample from both ends. Specifically, the four sliders clamp the four sides of the sample respectively. The four sides of one end of the sample are clamped in the clamp head of one clamp, and the four sides of the other end of the sample are clamped in the clamp head of the other clamp. The clamps are respectively matched with the tensile mechanism of the tensile testing machine, such as Figure 5 As shown, the screw and the tensile testing machine's stretching mechanism are mortise-and-tenon-jointed. The stretching mechanism pulls the screw 1. Because the claws 7 are wedge-fitted with the wedge-shaped grooves 522 within the accommodating chamber 521, the specimen is clamped tighter and tighter as the stretching mechanism stretches, minimizing the risk of specimen slippage due to insufficient prestress. The claws are also evenly leveled, reducing stress concentration. Furthermore, because the spring 712 supports the straight rod 71 and the chuck 4, it acts as a buffer when moving the components up and down, preventing hard contact. It can provide a buffering and fine-tuning function within a certain range to ensure that the tensile force applied to the specimen is aligned with the specimen axis.

[0045] In an optional embodiment, the contact area between the slider 72 of the jaw 7 and the sample is in the form of a rough surface.

[0046] Furthermore, the above example illustrates the structure of the clamp for clamping a rectangular specimen. Since the clamp is designed to fit the four sides of the rectangle, there are four wedge-shaped grooves, four corresponding claws, and four corresponding elliptical holes. However, this embodiment does not preclude the possibility of the clamp having N wedge-shaped grooves, N corresponding claws, and N corresponding first elliptical holes and N second elliptical holes to accommodate specimens with circular cross-sections. Alternatively, this embodiment does not preclude the possibility of using two clamps to clamp an object at both ends, rather than performing a tensile test.

[0047] The present invention also provides a tensile testing device, comprising the two wedge-shaped tensile fixtures described above and a tensile testing machine, wherein the tensile testing machine has a pair of tensile mechanisms that can move toward and away from each other. Figure 5 As shown, the stretching mechanism 100 of the tensile testing machine is provided with a tenon hole 200. The screw is inserted into the tenon hole 200 to engage with the stretching mechanism. The stretching mechanism drives the stretching fixture to move toward or away from each other, and a tensile test can be performed.

[0048] The present invention also provides a tensile test method, using the two wedge-shaped tensile fixtures described above, to perform the following steps: Figure 6 As shown:

[0049] S20, placing one end of the specimen between N sliders of one fixture, rotating the first nut so that the slider clamps the outer periphery of the one end of the specimen, and placing the other end of the specimen between N sliders of another fixture, rotating the first nut so that the slider clamps the outer periphery of the other end of the specimen. For rectangular specimens, the slider clamps the four sides of the specimen.

[0050] S30, connecting the screw rods of the two clamps to the corresponding stretching mechanisms respectively;

[0051] S40 uses a stretching mechanism to stretch the sample to both sides to perform a tensile test.

[0052] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A wedge-shaped tensile fixture, characterized in that: include: The screw, the lower end of which is coaxially connected to the top plate of the chuck as a whole; a first nut, the first nut being screwed onto the screw rod, and having an annular groove arranged along a circumferential direction thereof; A chuck having a through hole at its center for the screw to pass through, the chuck being sleeved below the first nut of the screw through the through hole, at least two hooks being provided on the chuck, one end of each hook being fixed to the chuck, and the other end of each hook being inserted into the annular groove, and N first elliptical holes being further provided on the chuck, and the major axis of each first elliptical hole being arranged along the radial direction of the chuck; A chuck is located below the chuck, and includes a top plate and a column coaxially connected to the lower end of the top plate. The top plate is provided with N second elliptical holes, and the major axis of each second elliptical hole is arranged along the radial direction of the chuck. The lower end of the column is open, and a receiving cavity is provided in the column coaxial with the column. N wedge-shaped grooves extending obliquely along the axial direction are evenly arranged in the circumferential direction in the receiving cavity, and the wedge-shaped grooves gradually extend radially inward in the direction away from the top plate; N claws, each claw includes a straight rod and a slider, the lower end of the straight rod abuts against the upper end surface of the slider, the slider slides in cooperation with the wedge-shaped groove, the upper end of the straight rod has an external thread, the straight rod passes through the second elliptical hole and the first elliptical hole from bottom to top, and a second nut is screwed on the end of the straight rod that passes through the first elliptical hole, the portion of the straight rod located in the accommodating cavity has an annular shoulder, and an elastic element is sleeved between the annular shoulder and the lower end surface of the chuck, The second nut is held above the chuck, and the elastic element is held below the chuck. The first nut is rotated to allow the slider to clamp the periphery of the sample, and the sample is stretched by the stretching screw. The N is 4, The elastic element is a spring.

2. The wedge-shaped tensile fixture according to claim 1, characterized in that: The surface of the slider in contact with the sample is in the form of a rough surface.

3. The wedge-shaped tensile fixture according to claim 1, characterized in that: The hook includes a first right-angled side and a third right-angled side bent at right angles in opposite directions from two ends of the second right-angled side.

4. The wedge-shaped tensile fixture according to claim 1, characterized in that: The included angle between the wedge-shaped groove and the axis of the chuck is 7 to 8 degrees.

5. A tensile testing device, characterized in that: The invention comprises two wedge-shaped tensile clamps according to any one of claims 1 to 4, and a tensile testing machine, wherein the wedge-shaped tensile clamps are respectively mortised with a pair of tensile mechanisms of the tensile testing machine via screw rods.

6. A tensile test method, characterized in that: Using the wedge-shaped tensile fixtures described in any one of claims 1 to 4, the following steps are performed: Place one end of the specimen between N sliders of one fixture, rotate the first nut so that the slider clamps the outer circumference of the one end of the specimen, and place the other end of the specimen between N sliders of another fixture, rotate the first nut so that the slider clamps the outer circumference of the other end of the specimen; Connect the screw rods of the two clamps to the corresponding stretching mechanisms respectively; The tensile test is carried out by stretching the specimen to both sides through the tensile mechanism.

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