An apparatus for testing the axial mechanical properties of small-sized tube bodies

Abstract

The present invention relates to the technical field of thin-walled tube performance testing, and specifically to a device for testing the axial mechanical properties of small-sized tube bodies, which solves the problems that the existing standard small punch test method uses thin plate specimens, and due to size limitations, thin-walled tubes cannot be processed into thin plates, and the standard small punch test specimens are subjected to double stress and cannot be used to test the mechanical properties of anisotropic materials. The present invention includes a sample-changing and force-applying mechanism and a testing mechanism. A separating and combining mechanism is installed outside the sample-changing and force-applying mechanism, and a plurality of testing mechanisms are installed inside the sample-changing and force-applying mechanism. The testing mechanism includes a specimen clamp. An internal force measuring mechanism is installed at the upper end of the specimen clamp, and a displacement measuring mechanism is installed at the lower end of the specimen clamp. By intercepting small specimens from the thin-walled tube, the present invention can effectively test the axial mechanical properties of the thin-walled tube, and simultaneously test and replace multiple small specimens, and the test results are more accurate.

Description

Technical Field

[0001] The present invention relates to the technical field of thin-walled tube performance testing, and particularly to a device for testing the axial mechanical properties of small-sized tube bodies. Background Technique

[0002] After the thin-walled tube is formed, mechanical property testing is required. The thin-walled tube is generally manufactured by a drawing forming process. Under this manufacturing process, some thin-walled tubes exhibit anisotropic mechanical properties. Under the condition of limited tube length, in order to test the mechanical properties of the tube, a test method using small specimens is required. The small punch technique is a micro-specimen test method, and its standard specimen is a disc with a diameter of 10 mm and a thickness of 0.5 mm. Since its birth in 1981, this technique has been widely used to test the mechanical properties of materials such as tensile, creep, and fracture toughness.

[0003] The existing standard small punch test method uses thin plate specimens. Due to size limitations, thin-walled tubes cannot be processed into thin plates, and the standard small punch specimens are subjected to double stress and cannot be used to test the mechanical properties of anisotropic materials; therefore, it does not meet the existing requirements, and for this reason, we propose a device for testing the axial mechanical properties of small-sized tube bodies. Summary of the Invention

[0004] The purpose of the present invention is to provide a device for testing the axial mechanical properties of small-sized tube bodies, so as to solve the problems raised in the above background technique that the existing standard small punch test method uses thin plate specimens, thin-walled tubes cannot be processed into thin plates due to size limitations, and the standard small punch test specimens are subjected to double stress and cannot be used to test the mechanical properties of anisotropic materials.

[0005] To achieve the above purpose, the present invention provides the following technical solution: A device for testing the axial mechanical properties of small-sized tube bodies, including a sample-changing and force-applying mechanism and a testing mechanism. A separating and combining mechanism is installed outside the sample-changing and force-applying mechanism, and a plurality of testing mechanisms are installed inside the sample-changing and force-applying mechanism. The testing mechanism includes a specimen clamp. A force measuring mechanism is installed inside the upper end of the specimen clamp, a displacement measuring mechanism is installed inside the bottom end of the specimen clamp. A tubular specimen is installed between the force measuring mechanism and the displacement measuring mechanism, and two waist-shaped holes are provided in the middle of the tubular specimen;

[0006] The specimen clamp includes a positioning bottom plate. A lower clamp is fixedly installed on the upper end surface of the positioning bottom plate, an upper clamp is installed on the upper end surface of the lower clamp, a plurality of positioning columns are installed between the lower clamp and the upper clamp. A sample placing arc groove is provided in the middle of the upper end of the lower clamp, and a positioning arc strip is installed on the inner wall of the sample placing arc groove.

[0007] Preferably, the force measuring mechanism includes an arc-headed punch rod, an arc-shaped contact surface is provided at the bottom end of the arc-headed punch rod, a transmission pressure block is installed at the upper end of the arc-headed punch rod, a force sensor is installed between the arc-headed punch rod and the transmission pressure block, and the arc-headed punch rod, the transmission pressure block and the force sensor are connected by threads.

[0008] The displacement measuring mechanism includes a mounting sleeve, a displacement sensor is installed inside the mounting sleeve, a follower rod is slidably connected between the displacement sensors, a limiting piece is installed on the outer side of the upper end of the follower rod, and a support spring is provided between the limiting piece and the mounting sleeve.

[0009] Preferably, the separating and combining mechanism includes a support base, a mounting box is fixedly installed on the upper end surface of the support base, a transmission screw rod is rotatably connected inside one end corner of the mounting box, and guide columns are fixedly installed inside the other three end corners of the mounting box. A connecting frame is installed at the upper ends of the transmission screw rod and the three guide columns, and a transmission motor is fixedly installed at one end corner of the upper end surface of the connecting frame.

[0010] Preferably, the sample-changing and force-applying mechanism includes a mounting frame, a control panel is fixedly installed in the middle of the front end of the mounting frame, cylinders are fixedly installed at both ends of the mounting frame, a first connecting rod is installed at the output end of the cylinder, a second connecting rod is installed at one end of the first connecting rod, and a flipping positioning plate is rotatably connected inside the mounting frame. A plurality of DC servo motors are fixedly installed on the upper end surface of the flipping positioning plate, and a motor support seat is fixedly installed at the upper end of the DC servo motor.

[0011] Preferably, the output end of the transmission motor penetrates through one end corner of the connecting frame and is connected to the upper end of the transmission screw rod through a coupling. The transmission screw rod is connected to the mounting frame by threads. The mounting frame is slidably connected to the three guide columns, and the other three end corners of the connecting frame are fixedly connected to the three guide columns.

[0012] Preferably, the output end of the cylinder is rotatably connected to the first connecting rod through a pin, the first connecting rod and the second connecting rod are rotatably connected through a pin, and the two ends of the second connecting rod away from the first connecting rod are fixedly connected to both ends of the flipping positioning plate.

[0013] Preferably, a plurality of the motor support seats and the testing mechanism are arranged in an array on the upper end surface of the flipping positioning plate. The output end of the DC servo motor penetrates through the motor support seat and is fixedly connected to the upper end of the transmission pressure block. The transmission pressure block is fixedly connected to the force sensor, and the arc-headed punch rod is slidably connected to the upper fixture.

[0014] Preferably, the upper end of the force sensor is fixedly connected to the transmission pressing block by a thread. The lower end face of the force sensor is in close contact with the arc head punch rod. The force sensor, displacement sensor, and control panel are electrically connected.

[0015] Preferably, the mounting sleeve is connected to the lower fixture by a thread. The mounting sleeve is connected to the displacement sensor by a thread. The upper end of the follower rod passes through the displacement sensor, mounting sleeve, support spring, and limit piece and is inserted into the inner side of the middle part of the lower fixture. The follower rod is slidably connected to both the mounting sleeve and the displacement sensor. The follower rod is fixedly connected to the limit piece. The upper end of the mounting sleeve is connected to the limit piece by a support spring.

[0016] Preferably, the upper end face of the impact area of the tubular specimen is in close contact with the arc-shaped contact surface. The middle part of the lower end face of the impact area of the tubular specimen is in close contact with the follower rod. The arc-shaped contact surface is arranged between two kidney-shaped holes. The two kidney-shaped holes are symmetrically installed with respect to the axis of the arc head punch rod. The thickness dimension h of the tubular specimen is 0.5 mm.

[0017] The upper end of the lower fixture is connected to a plurality of positioning columns by threads. The bottom end of the upper fixture is slidably connected to a plurality of positioning columns. The flipping positioning plate is connected to the upper ends of a plurality of upper fixtures by threads. The tubular specimen is arranged between the upper fixture and the lower fixture. The positioning arc-shaped strip is fixedly connected to the lower fixture. One end of the tubular specimen is in close contact with one side of the positioning arc-shaped strip.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] 1. In the present invention, two cylinders push the first connecting rod and drive the flipping positioning plate to flip relative to the mounting frame through the second connecting rod. At this time, it is convenient to synchronously place a plurality of tubular specimens inside the laying arc groove. Furthermore, the end of the tubular specimen can be positioned through the positioning arc-shaped strip, thus ensuring the accurate placement of the tubular specimen. The driving motor drives the sample-changing force-applying mechanism to move downward through the driving screw rod. The lower fixture can be positioned and clamped with the upper fixture through a plurality of positioning columns. The two kidney-shaped holes are symmetrically installed with respect to the axis of the arc head punch rod. The DC servo motor performs a synchronous force-applying operation on the tubular specimen through the force measuring mechanism, which is convenient for synchronously testing a plurality of tubular specimens under different loads.

[0020] 2. The force applied by the arc-headed punch rod to the tubular specimen can be measured by the force sensor of the present invention, so as to facilitate the measurement of the loads on multiple tubular specimens. When the tubular specimen is stressed and deformed, it presses down the follower rod. Then, when the follower rod moves downward, the support spring is compressed by the limit piece. Subsequently, the displacement sensor can measure the displacement of the follower rod, thereby realizing the displacement measurement of the deformation of the tubular specimen and achieving the test operation of the axial tensile properties of multiple thin-walled tubes synchronously. After the test is completed, the multiple tubular specimens can be replaced by separating the lower fixture and the upper fixture. Moreover, the follower rod can automatically reset under the support of the support spring through the limit piece, thus facilitating the repeated testing of the tubular specimens. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic structural diagram of the whole of the present invention;

[0022] Figure 2 is a top view of the sample-changing and force-applying mechanism of the present invention;

[0023] Figure 3 is a schematic structural diagram of the sample-changing and force-applying mechanism of the present invention;

[0024] Figure 4 is a schematic sectional structural diagram of the whole of the present invention;

[0025] Figure 5 is a schematic structural diagram of the test mechanism of the present invention;

[0026] Figure 6 is a schematic sectional structural diagram of the test mechanism of the present invention;

[0027] Figure 7 is an exploded structural diagram of the test mechanism of the present invention;

[0028] Figure 8 is a schematic structural diagram of the tubular specimen of the present invention;

[0029] Figure 9 is a load curve diagram of the tubular specimen of the present invention;

[0030] Figure 10 is a schematic diagram of the maximum load of the tubular specimen of the present invention;

[0031] Figure 11 is a schematic structural diagram of the tubular specimen of the present invention.

[0032] In the figure: 1. Separation and combination mechanism; 101. Support base; 102. Installation box; 103. Guide column; 104. Connection frame; 105. Transmission screw; 106. Transmission motor; 2. Sample replacement and force application mechanism; 201. Installation frame; 202. Control panel; 203. Flip positioning plate; 204. Cylinder; 205. Motor support base; 206. DC servo motor; 207. First connecting rod; 208. Second connecting rod; 3. Testing mechanism; 4. Specimen fixture; 401. Positioning base plate; 402. Lower fixture; 403. Upper fixture; 404. Positioning column; 405. Lofting arc groove; 406. Positioning arc strip; 5. Force measurement mechanism; 501. Transmission pressure block; 502. Arc contact surface; 503. Force sensor; 504. Arc head punch rod; 6. Displacement measurement mechanism; 601. Installation sleeve; 602. Follow-up rod; 603. Displacement sensor; 604. Support spring; 605. Limit piece; 7. Tubular specimen; 701. Impact area; 8. Kidney-shaped hole. Detailed implementation manner

[0033] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0034] Please refer to Figures 1 to 4 , an embodiment provided by the present invention: A device for testing the axial mechanical properties of small-sized pipe bodies, including a sample replacement and force application mechanism 2 and a testing mechanism 3. A separation and combination mechanism 1 is installed outside the sample replacement and force application mechanism 2. The separation and combination mechanism 1 includes a support base 101. An installation box 102 is fixedly installed on the upper end surface of the support base 101. A transmission screw 105 is rotatably connected to the inner side of one end angle of the installation box 102. Guide columns 103 are fixedly installed on the inner sides of the other three end angles of the installation box 102. A connection frame 104 is installed at the upper ends of the transmission screw 105 and the three guide columns 103. The other three end angles of the connection frame 104 are fixedly connected to the three guide columns 103. A transmission motor 106 is fixedly installed at one end angle of the upper end surface of the connection frame 104. The output end of the transmission motor 106 penetrates through one end angle of the connection frame 104 and is connected to the upper end of the transmission screw 105 through a coupling, so that the transmission motor 106 drives the sample replacement and force application mechanism 2 to move downward outside the three guide columns 103 under the support of the connection frame 104 through the transmission screw 105, realizing the mold closing operation of the specimen fixture 4.

[0035] Please refer to Figure 5 and Figure 6, multiple testing mechanisms 3 are installed inside the sample-changing and force-increasing mechanism 2. The testing mechanism 3 includes a specimen fixture 4. Inside the upper end of the specimen fixture 4, a force measurement mechanism 5 is installed. Inside the bottom end of the specimen fixture 4, a displacement measurement mechanism 6 is installed. A tubular specimen 7 is installed between the force measurement mechanism 5 and the displacement measurement mechanism 6. Two waist-shaped holes 8 are provided in the middle of the tubular specimen 7. The upper end face of the tubular specimen 7 is in fitting contact with the arc-shaped contact surface 502. The middle part of the lower end face of the tubular specimen 7 is in fitting contact with the follower rod 602. The arc-shaped contact surface 502 is arranged between the two waist-shaped holes 8. The two waist-shaped holes 8 are symmetrically installed with respect to the axis of the arc head punch 504. The thickness dimension h of the tubular specimen 7 is 0.5 mm. By applying a load to the impact area 701 between the two waist-shaped holes 8, the mechanical properties test of the tubular specimen 7 can be realized.

[0036] Please refer to Figure 5 , Figure 6 , Figure 7 , Figure 8 and Figure 11 , the specimen fixture 4 includes a positioning base plate 401. An upper fixture 402 is fixedly installed on the upper end face of the positioning base plate 401. An upper fixture 403 is installed on the upper end face of the lower fixture 402. The upper ends of the flipping positioning plate 203 and multiple upper fixtures 403 are all connected by threads. The tubular specimen 7 is arranged between the upper fixture 403 and the lower fixture 402. Multiple positioning columns 404 are installed between the lower fixture 402 and the upper fixture 403. The upper end of the lower fixture 402 is connected to multiple positioning columns 404 by threads. The bottom end of the upper fixture 403 is slidably connected to multiple positioning columns 404. A sample laying arc groove 405 is provided in the middle of the upper end of the lower fixture 402. A positioning arc strip 406 is installed on the inner wall of the sample laying arc groove 405. The positioning arc strip 406 is fixedly connected to the lower fixture 402. One end of the tubular specimen 7 is in fitting contact with one side of the positioning arc strip 406. The positioning arc strip 406 can be used to position the end of the tubular specimen 7, thereby ensuring the accurate placement of the tubular specimen 7.

[0037] Please refer to Figure 6 and Figure 7, the force measuring mechanism 5 includes an arc-headed punch 504, enabling the motor support base 205, supported by the DC servo motor 206, to perform synchronous testing operations on the tubular specimen 7 through the force measuring mechanism 5. The arc-headed punch 504 is slidably connected to the upper fixture 403. The bottom end of the arc-headed punch 504 is provided with an arc-shaped contact surface 502. A transmission pressing block 501 is installed at the upper end of the arc-headed punch 504. A force sensor 503 is installed between the arc-headed punch 504 and the transmission pressing block 501. The upper end of the force sensor 503 is threadedly connected to the transmission pressing block 501, and the lower end surface of the force sensor 503 is in close contact with the arc-headed punch 504. The force sensor 503 can measure the force exerted by the arc-headed punch 504 on the tubular specimen 7, facilitating synchronous testing operations on multiple tubular specimens 7 under different loads.

[0038] Please refer to Figure 6 and Figure 7 , the displacement measuring mechanism 6 includes a mounting sleeve 601. The mounting sleeve 601 is threadedly connected to the lower fixture 402. A displacement sensor 603 is installed inside the mounting sleeve 601. The mounting sleeve 601 is threadedly connected to the displacement sensor 603. A follower rod 602 is slidably connected between the displacement sensors 603. The follower rod 602 is slidably connected to both the mounting sleeve 601 and the displacement sensor 603. A limit piece 605 is installed on the outer side of the upper end of the follower rod 602, and the follower rod 602 is fixedly connected to the limit piece 605. A support spring 604 is provided between the limit piece 605 and the mounting sleeve 601. The upper end of the follower rod 602 passes through the displacement sensor 603, the mounting sleeve 601, the support spring 604, and the limit piece 605 and is inserted into the inner side of the middle part of the lower fixture 402. The upper end of the mounting sleeve 601 is connected to the limit piece 605 through the support spring 604. When the tubular specimen 7 deforms, it will press down on the follower rod 602. Then, when the follower rod 602 moves downward, it drives the support spring 604 to compress through the limit piece 605. Subsequently, the displacement sensor 603 can detect the displacement amount of the follower rod 602, thereby realizing the measurement of the displacement of the tubular specimen 7 in the vertical direction after being deformed by force.

[0039] Please refer to Figure 3 and Figure 4, the sample-changing and force-increasing mechanism 2 includes an installation frame 201. The transmission screw 105 is threadedly connected to the installation frame 201. The installation frame 201 is slidably connected to all three guiding columns 103. A control panel 202 is fixedly installed in the middle of the front end of the installation frame 201. The force sensor 503, the displacement sensor 603, and the control panel 202 are electrically connected. Cylinders 204 are fixedly installed at both ends of the installation frame 201. The output end of the cylinder 204 is equipped with a first connecting rod 207. The output end of the cylinder 204 and the first connecting rod 207 are rotationally connected by a pin. One end of the first connecting rod 207 is equipped with a second connecting rod 208. The first connecting rod 207 and the second connecting rod 208 are rotationally connected by a pin. The two ends of the two second connecting rods 208 far from the first connecting rod 207 are fixedly connected to both ends of the flipping and positioning plate 203. The flipping and positioning plate 203 is rotatably connected to the inner side of the installation frame 201, so that the two cylinders 204 push the first connecting rod 207 and drive the flipping and positioning plate 203 to flip relative to the installation frame 201 through the second connecting rod 208. At this time, it is convenient to synchronously sample and lay out multiple tubular specimens 7;

[0040] A plurality of DC servo motors 206 are fixedly installed on the upper end surface of the flipping and positioning plate 203. The upper end of the DC servo motor 206 is fixedly installed with a motor support seat 205. The plurality of motor support seats 205 and the testing mechanism 3 are arranged in an array on the upper end surface of the flipping and positioning plate 203. The output end of the DC servo motor 206 penetrates through the motor support seat 205 and is fixedly connected to the upper end of the transmission pressing block 501, so that the DC servo motor 206 performs synchronous testing operations on the tubular specimen 7 under the support of the motor support seat 205 through the force measuring mechanism 5.

[0041] Please refer to Figure 9 , the force-displacement curve obtained by testing the tubular specimen 7 can be divided into four stages, namely the elastic deformation stage (I), the plastic deformation stage (II), the film stretching stage (III), and the plastic instability and fracture stage (IV). The yield strength ( ) and the tensile strength ( ) of the tubular specimen 7 are:

[0042] ;

[0043] ;

[0044] Where is the initial thickness of the tubular specimen 7, is the maximum load during the testing process of the tubular specimen 7, is the displacement of the follower rod 602, and are correlation coefficients depending on the testing of the tubular specimen 7, is the elastic-plastic transition force.

[0045] Please refer to Figure 10 , The value of can be obtained by the method specified in the European Union standard EN10372 or the American standard ASTM E3205. According to the method specified in the European Union standard EN10372, the elastic-plastic transition force is fitted by the following bilinear equations:[[]]

[0046] ;

[0047] where is the elastic-plastic transition force, is the displacement at , is the initial thickness of the tubular specimen 7 , is the load at . The parameters , and of the bilinear equations are determined by minimizing the fitting error, and the fitting error can be calculated by the following formula:[[]]

[0048] ;

[0049] When the fitting error reaches the minimum, is the elastic-plastic transition force measured by the method specified in the European Union standard EN10372 , denoted as ;

[0050] After finding the minimum fitting error to determine , the American standard ASTM E3205 proposes to draw a vertical line downward through the intersection point A of two linear curves, which intersects the load-displacement curve obtained from the small punch test at point C. At this time, the load value corresponding to point C is obtained by the American standard ASTM E3205, denoted as .

[0051] In use, when performing a small punch test on a thin-walled tube, the thin-walled tube is processed into a tubular specimen 7 by wire cutting. If the thickness h of the tubular specimen 7 is much larger than 0.5 mm, a thinning treatment is required. After turning on the power, the lower clamp 402 and the upper clamp 403 are separated in the initial state. Start the two cylinders 204, so that the two cylinders 204 push the first connecting rod 207 and drive the flipping positioning plate 203 to flip relative to the mounting frame 201 through the second connecting rod 208. At this time, it is convenient to synchronously place multiple tubular specimens 7 inside the lofting arc groove 405. Furthermore, the positioning arc bar 406 can position the end of the tubular specimen 7, thereby ensuring the accurate placement of the tubular specimen 7;

[0052] Reset the flipping positioning plate 203 relative to the mounting frame 201. Start the driving motor 106, so that the driving motor 106 drives the sample-changing and force-applying mechanism 2 to move downward outside the three guiding columns 103 under the support of the connecting frame 104 through the driving screw 105. Furthermore, the flipping positioning plate 203 synchronously drives multiple force measuring mechanisms 5 to move downward through the upper clamp 403. The lower clamp 402 can perform a positioning and clamping operation with the upper clamp 403 through multiple positioning columns 404. At this time, the bottom end of the arc-headed punch 504 penetrates through the upper clamp 403 and is in close contact with the upper end surface of the tubular specimen 7. The follower rod 602 can be in close contact with the middle of the lower end surface of the tubular specimen 7 under the support of the support spring 604 through the limit piece 605. The two waist-shaped holes 8 are symmetrically installed relative to the axis of the arc-headed punch 504;

[0053] Synchronously start multiple DC servo motors 206, so that the DC servo motors 206 perform a synchronous test operation on the tubular specimen 7 through the force measuring mechanism 5 under the support of the motor support base 205. Among them, a force sensor 503 is provided between the driving pressure block 501 and the arc-headed punch 504, so that the control panel 202 can measure and display the force applied by the arc-headed punch 504 to the tubular specimen 7 through the force sensor 503. Furthermore, it is convenient to test the loads received by multiple tubular specimens 7. An arc-shaped contact surface 502 is provided at the bottom end of the arc-headed punch 504, and the arc-shaped contact surface 502 is in complete close contact with the surface of the impact area 701. In this way, it can effectively maintain uniform pressurization of the impact area 701 of the arc-headed punch 504 on the tubular specimen 7;

[0054] During the test of the tubular specimen 7, the tubular specimen 7 deforms and presses down on the follower rod 602. Then, when the follower rod 602 moves downward, it drives the support spring 604 to compress through the limit piece 605. Subsequently, the displacement sensor 603 can detect the displacement of the follower rod 602, thereby realizing the measurement of the displacement of the tubular specimen 7 in the vertical direction, facilitating the axial tensile performance test operation of multiple thin-walled tubes. After the test is completed, the multiple tubular specimens 7 can be replaced by separating the lower fixture 402 and the upper fixture 403. Moreover, the follower rod 602 can automatically reset under the support of the support spring 604 through the limit piece 605, thus facilitating the repeated testing of the tubular specimen 7.

[0055] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claimed rights.

Claims

1. An apparatus for testing the axial mechanical properties of small-sized pipe bodies, comprising a sample-changing force-applying mechanism (2) and a testing mechanism (3), characterized in that: A separating and combining mechanism (1) is installed on the outer side of the sample-changing and force-applying mechanism (2), and a plurality of testing mechanisms (3) are installed on the inner side of the sample-changing and force-applying mechanism (2). The testing mechanism (3) includes a specimen clamp (4). An internal force measuring mechanism (5) is installed on the upper end of the specimen clamp (4), and a displacement measuring mechanism (6) is installed on the inner side of the bottom end of the specimen clamp (4). A tubular specimen (7) is installed between the force measuring mechanism (5) and the displacement measuring mechanism (6). Two waist-shaped holes (8) are provided in the middle of the tubular specimen (7). The specimen clamp (4) includes a positioning bottom plate (401). A lower clamp (402) is fixedly installed on the upper end surface of the positioning bottom plate (401). An upper clamp (403) is installed on the upper end surface of the lower clamp (402). A plurality of positioning columns (404) are installed between the lower clamp (402) and the upper clamp (403). A sample placement arc groove (405) is provided in the middle of the upper end of the lower clamp (402). A positioning arc strip (406) is installed on the inner wall of the sample placement arc groove (405). The force measuring mechanism (5) includes an arc-headed punch rod (504). An arc-shaped contact surface (502) is provided at the bottom end of the arc-headed punch rod (504). A transmission pressure block (501) is installed on the upper end of the arc-headed punch rod (504). A force sensor (503) is installed between the arc-headed punch rod (504) and the transmission pressure block (501). The arc-headed punch rod (504), the transmission pressure block (501) and the force sensor (503) are connected by threads. The displacement measuring mechanism (6) includes an installation sleeve (601). A displacement sensor (603) is installed on the inner side of the installation sleeve (601). A follower rod (602) is slidably connected between the displacement sensors (603). A limiting piece (605) is installed on the outer side of the upper end of the follower rod (602). A support spring (604) is provided between the limiting piece (605) and the installation sleeve (601). The sample-changing and force-applying mechanism (2) includes an installation frame (201). A control panel (202) is fixedly installed in the middle of the front end of the installation frame (201). Cylinders (204) are fixedly installed at both ends of the installation frame (201). A first connecting rod (207) is installed at the output end of the cylinder (204). A second connecting rod (208) is installed at one end of the first connecting rod (207). A flipping positioning plate (203) is rotatably connected to the inner side of the installation frame (201). A plurality of DC servo motors (206) are fixedly installed on the upper end surface of the flipping positioning plate (203). A motor support seat (205) is fixedly installed on the upper end of the DC servo motor (206). The upper end face of the tubular specimen (7) is in complete fitting contact with the arc-shaped contact surface (502). The middle part of the lower end face of the tubular specimen (7) is in fitting contact with the follower rod (602). The arc-shaped contact surface (502) is arranged between two waist-shaped holes (8). The two waist-shaped holes (8) are symmetrically installed with respect to the axis of the arc-headed punch (504). The thickness dimension h of the tubular specimen (7) is 0.5 mm; The upper end of the lower clamp (402) is threadedly connected to a plurality of positioning posts (404). The bottom end of the upper clamp (403) is slidably connected to a plurality of positioning posts (404). The flipping positioning plate (203) is threadedly connected to the upper ends of a plurality of upper clamps (403). The tubular specimen (7) is arranged between the upper clamp (403) and the lower clamp (402). The positioning arc-shaped strip (406) is fixedly connected to the lower clamp (402). One end of the tubular specimen (7) is in fitting contact with one side of the positioning arc-shaped strip (406).

2. The device for testing the axial mechanical properties of a small-sized tube body according to claim 1, characterized in that: The separating and combining mechanism (1) includes a support base (101). An installation box (102) is fixedly installed on the upper end face of the support base (101). A transmission screw rod (105) is rotatably connected to the inner side of one end corner of the installation box (102). Guide columns (103) are fixedly installed on the inner sides of the other three end corners of the installation box (102). A connecting frame (104) is installed at the upper ends of the transmission screw rod (105) and the three guide columns (103). A transmission motor (106) is fixedly installed at one end corner of the upper end face of the connecting frame (104).

3. The device for testing the axial mechanical properties of a small-sized tube body according to claim 2, wherein: The output end of the transmission motor (106) penetrates through one end corner of the connecting frame (104) and is connected to the upper end of the transmission screw rod (105) through a coupling. The transmission screw rod (105) is threadedly connected to the installation frame (201). The installation frame (201) is slidably connected to the three guide columns (103). The other three end corners of the connecting frame (104) are fixedly connected to the three guide columns (103).

4. An apparatus for testing the axial mechanical properties of a small-sized tube body according to claim 3, characterized in that: The output end of the air cylinder (204) is rotatably connected to the first connecting rod (207) through a pin. The first connecting rod (207) is rotatably connected to the second connecting rod (208) through a pin. The two ends of the second connecting rods (208) away from the first connecting rod (207) are fixedly connected to both ends of the flipping positioning plate (203).

5. The device for testing the axial mechanical properties of a small-sized tube body according to claim 4, characterized in that: A plurality of the motor support seats (205) and the testing mechanism (3) are arranged in an array on the upper end face of the flipping positioning plate (203). The output end of the DC servo motor (206) penetrates through the motor support seat (205) and is fixedly connected to the upper end of the transmission pressing block (501). The transmission pressing block (501) is fixedly connected to the force sensor (503). The arc-headed punch (504) is slidably connected to the upper clamp (403).

6. The device for testing the axial mechanical properties of a small-sized tube body according to claim 5, characterized in that: The upper end of the force sensor (503) is fixedly connected to the transmission pressure block (501) by a thread. The lower end surface of the force sensor (503) is in close contact with the arc head punch rod (504). The force sensor (503), the displacement sensor (603) and the control panel (202) are electrically connected.

7. An apparatus for testing the axial mechanical properties of a small-sized tube body according to claim 6, characterized in that: The mounting sleeve (601) is connected to the lower fixture (402) by a thread. The mounting sleeve (601) is connected to the displacement sensor (603) by a thread. The upper end of the follower rod (602) penetrates through the displacement sensor (603), the mounting sleeve (601), the support spring (604) and the limit piece (605) and is inserted into the inner side of the middle part of the lower fixture (402). The follower rod (602) is slidably connected to both the mounting sleeve (601) and the displacement sensor (603). The follower rod (602) is fixedly connected to the limit piece (605). The upper end of the mounting sleeve (601) is connected to the limit piece (605) by the support spring (604).

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