Tension-compression-tension-compression fatigue testing machine for concrete quasi-brittle materials

Abstract

The invention relates to the technical field of concrete fatigue tests, and discloses a concrete quasi-brittle material tension-compression-tension-compression fatigue testing machine which comprises a shell, a loading platform is arranged in the shell, driving devices are arranged on the two sides of the loading platform respectively, and the loading platform slides relative to the shell through the two driving devices and extends out of the open end of the shell. The concrete sample is loaded; the dustproof fence is fixedly connected to the top face of the loading platform, a notch is formed in the side, close to the open end of the shell, of the dustproof fence, clamping devices are arranged on the two sides of an inner cavity of the dustproof fence correspondingly, the clamping devices are used for clamping the ends of concrete samples, and the two clamping devices are in transmission connection with the same stretching device. The two clamping devices move towards each other or away from each other through the stretching device; a jacking hole is formed in the top face of the loading platform, the jacking plate is located in the positioning hole, and a jacking device is arranged on the bottom face of the jacking plate. Concrete samples with different sizes can be clamped and fixed, and the experiment efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of concrete fatigue experiments, in particular to a concrete-like quasi-brittle material tension-compression-tension-compression fatigue testing machine. Background Art

[0002] Hydraulic concrete structures are often subjected to cyclic loads, such as periodic changes in water level and temperature, high-intensity earthquakes, high-power flood discharges, unit vibrations, high-speed water flow impacts, etc. The internal stress field of concrete structures subjected to the above cyclic loads will change dramatically, which can easily cause fatigue damage or even destruction.

[0003] The failure of hydraulic concrete structures under continuous cyclic fatigue loads usually manifests itself as severe crack expansion in the concrete structure, which in turn affects the safe and effective operation of hydraulic structures. Therefore, whether the design of hydraulic concrete structures is safe and reasonable depends not only on the correctness of the resistance analysis method, but also on the fatigue mechanical properties of the concrete materials used, which is an indispensable and important part of ensuring the fatigue resistance of hydraulic concrete structures and preventing earthquake disasters.

[0004] By conducting fatigue tests in the laboratory, we can not only simulate the long-term cyclic loads that concrete structures are subjected to in actual use to evaluate their fatigue life and failure mechanism, thereby ensuring the safety performance of concrete structures, but also simulate the fatigue behavior of concrete during long-term use by applying alternating loads, and observe its deformation, cracking and damage after multiple loadings, so as to gain a deeper understanding of the performance changes of concrete during long-term use. At the same time, conducting concrete fatigue tests will also help promote the progress of concrete materials and structural design. By studying the fatigue properties of different concrete materials and structural forms, it can provide theoretical support and experimental basis for the design of new concrete materials and structures, and promote the continuous development of concrete technology. Therefore, conducting concrete fatigue tests in the laboratory is of great significance for ensuring the safety performance of concrete structures, evaluating their performance under long-term use conditions, evaluating the degree of fatigue damage, and promoting the development of concrete technology.

[0005] However, most of the existing concrete fatigue fracture test devices have simple structures and single functions. The structural parts for fixing concrete in most devices cannot clamp and fix concrete specimens of different sizes, especially in axial tensile fatigue tests. During fatigue tests, the chuck often detaches or stress concentrates, affecting the fatigue test efficiency of quasi-brittle materials such as concrete. In addition, the existing concrete fatigue testing machines are mainly single tensile fatigue tests or single compression fatigue tests. During long-term and high-frequency testing, problems such as decreased accuracy and insufficient stability may occur, which will cause deviations in test results and affect the accurate evaluation of the fatigue performance of the material. In addition, since concrete is a quasi-brittle material, brittle failure of concrete specimens is likely to occur during fatigue tests, which may cause damage to the testing machine or injury to personnel. Summary of the invention

[0006] The purpose of the present invention is to provide a concrete-like quasi-brittle material tension-compression-tension-compression fatigue testing machine to solve the problems existing in the prior art.

[0007] To achieve the above object, the present invention provides the following solution: The present invention provides a concrete-like quasi-brittle material tension-compression-tension-compression fatigue testing machine, comprising:

[0008] A housing, one side of which is configured as an open end,

[0009] A loading platform, the loading platform is arranged in the shell, and driving devices are respectively arranged on both sides of the loading platform. The loading platform slides relative to the shell through the two driving devices and extends from the open end of the shell so as to load the concrete sample;

[0010] A dustproof enclosure, the dustproof enclosure is fixedly connected to the top surface of the loading platform, a notch is arranged on one side of the dustproof enclosure close to the open end of the shell, clamping devices are arranged on both sides of the inner cavity of the dustproof enclosure, the clamping devices are used to clamp the ends of the concrete sample, the two clamping devices are transmission-connected to the same stretching device, and the two clamping devices move toward or away from each other through the stretching device;

[0011] A lifting plate, the top surface of the loading platform is provided with a through hole, the lifting plate is located in the through hole, and the bottom surface of the lifting plate is provided with a lifting device, the lifting device is used to lift the concrete sample so that the two ends of the concrete sample enter the two clamping devices for clamping.

[0012] Preferably, the clamping device comprises:

[0013] A clamping frame, the clamping frame is drivingly connected to the stretching device;

[0014] The clamping plate is located at the top of the inner cavity of the clamping frame, the top surface of the clamping frame is fixedly connected with a cylinder, the output end of the cylinder passes through the clamping frame and is fixedly connected to the top surface of the clamping plate, and the clamping plate and the bottom surface of the inner cavity of the clamping frame clamp the concrete sample.

[0015] Preferably, the stretching device comprises:

[0016] A stretching motor, wherein the stretching motor is fixedly connected to one side of the dustproof enclosure;

[0017] A stretching bidirectional screw, wherein the output end of the stretching motor is fixedly connected to one end of the stretching bidirectional screw, and the other end of the stretching bidirectional screw is rotatably connected to the inner wall of the dustproof enclosure;

[0018] A stretching block is fixedly connected to the clamping frame, and the stretching bidirectional screw penetrates the stretching block and is connected to the stretching block by threads;

[0019] A stretching guide rod, both ends of which are respectively fixed to the two sides of the dustproof enclosure, and the stretching guide rod passes through the stretching block and is in sliding contact with the stretching block.

[0020] Preferably, the lifting device comprises:

[0021] Two lifting seats, the two lifting seats are fixedly connected to the bottom surface of the shell, two lifting guide rods are fixedly connected between the two lifting seats, a lifting bidirectional screw is rotatably connected between the two lifting guide rods, one end of the lifting bidirectional screw passes through the output end of the lifting motor fixed to one of the lifting seats, the lifting guide rod and the lifting bidirectional screw are penetrated by two lifting blocks, the lifting block is in sliding contact with the lifting guide rod, the lifting block is connected to the lifting bidirectional screw by threads, a lifting hole is opened on the bottom surface of the shell, one end of the lifting rod is hingedly set on the two lifting blocks, the other end of the lifting rod passes through the lifting hole and is hinged to the lifting plate, a plurality of lifting limit rods are fixedly connected to the bottom surface of the lifting plate, the lifting limit rods pass through the bottom surface of the shell and are in sliding contact with the shell.

[0022] Preferably, it also includes:

[0023] A pressing plate is arranged at the top of the inner cavity of the shell, a connecting block is fixedly connected to the top surface of the pressing plate, a pressing device is fixedly connected to the connecting block, and the pressing plate presses the concrete sample through the pressing device.

[0024] Preferably, the pressing device comprises:

[0025] The two lower pressure seats are fixedly connected to the top surface of the shell, two lower pressure guide rods are fixedly connected between the two lower pressure seats, and a lower pressure bidirectional screw is rotatably connected between the two lower pressure guide rods, one end of the lower pressure bidirectional screw passes through one of the lower pressure seats and is fixed to the output end of the lower pressure motor, the lower pressure guide rod and the lower pressure bidirectional screw are penetrated by two lower pressure blocks, the lower pressure block is in sliding contact with the lower pressure guide rod, the lower pressure block is connected to the lower pressure bidirectional screw by threads, a lower pressure hole is opened on the top surface of the shell, one end of the lower pressure rod is hingedly provided on the two lower pressure blocks, the other end of the lower pressure rod passes through the lower pressure hole and is hinged to the connecting block, a plurality of lower pressure limit rods are fixedly connected to the top surface of the pressure plate, and the lower pressure limit rods pass through the top surface of the shell and are in sliding contact with the shell.

[0026] Preferably, the driving device comprises:

[0027] A driving motor, wherein the driving motor is fixedly connected to the inner wall of the housing, an output end of the driving motor is fixedly connected to one end of a driving screw, and the other end of the driving screw is rotatably connected to the inner wall of the housing;

[0028] The driving block is fixedly connected to the loading platform, and the driving screw passes through the driving block and is connected to the driving block through threads.

[0029] Preferably, it also includes:

[0030] Two slide rails are respectively fixed to the bottom surface of the shell cavity, and sliders are respectively fixed to both sides of the bottom surface of the loading platform. The bottom surface of the slider is provided with a slide groove matched with the slide rail, and the inner wall of the slide groove is in sliding contact with the slide rail.

[0031] Preferably, a box door is provided at the open end of the shell, a rectangular hole is opened in the middle of the box door, a tempered glass is fixed in the rectangular hole, and a handle is fixed on the box door.

[0032] Preferably, support legs are fixedly connected to the four corners of the bottom surface of the shell.

[0033] The present invention discloses the following technical effects:

[0034] 1. The loading platform provided in the present invention extends from the open end of the shell to place the concrete sample, so as to realize the loading of the concrete sample. When conducting the test, the staff only needs to place the concrete sample on the loading platform, and then the clamping loading and tension and compression tests can be automatically performed, which greatly improves the work efficiency and loading accuracy.

[0035] 2. The clamping device provided in the present invention can clamp and fix concrete samples of different sizes, thereby improving flexibility and adaptability.

[0036] 3. The dustproof enclosure provided in the present invention can shield the broken concrete sample fragments, and at the same time, it is convenient to clean the loading platform after it is extended from the shell.

[0037] 4. The present invention can realize fatigue testing of unidirectional tension, compression and tension-compression bidirectional synchronous loading on concrete samples, which can be closer to the actual engineering operation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0039] Figure 1 It is a structural schematic diagram of a concrete-type quasi-brittle material tension-compression-tension-compression fatigue testing machine of the present invention;

[0040] Figure 2 It is a schematic diagram of the structure of the clamping device in the present invention;

[0041] Figure 3 It is a structural schematic diagram of the downward pressing device in the present invention;

[0042] Figure 4 It is a structural schematic diagram of the jacking device in the present invention;

[0043] Among them, 1. Shell; 2. Loading platform; 3. Lifting limit rod; 4. Dustproof enclosure; 5. Lifting plate; 6. Clamping frame; 7. Clamping plate; 8. Cylinder; 9. Stretching motor; 10. Stretching bidirectional screw; 11. Stretching block; 12. Stretching guide rod; 13. Lifting seat; 14. Lifting guide rod; 15. Lifting bidirectional screw; 16. Lifting motor; 17. Lifting block; 18. Lifting rod; 19. Pressing plate; 20. Connecting block; 21. Pressing seat; 22. Pressing guide rod; 23. Pressing bidirectional screw; 24. Pressing motor; 25. Pressing block; 26. Pressing rod; 27. Driving motor; 28. Driving screw; 29. ​​Driving block; 30. Slide rail; 31. Sliding block; 32. Box door; 33. Handle; 34. Support leg; 35. Pressing limit rod. DETAILED DESCRIPTION

[0044] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0046] Reference Figure 1-Figure 4 The present invention provides a concrete-like quasi-brittle material tension-compression-tension-compression fatigue testing machine, comprising:

[0047] The housing 1 has one side which is set as an open end.

[0048] A loading platform 2, which is disposed in the housing 1. Driving devices are disposed on both sides of the loading platform 2. The loading platform 2 slides relative to the housing 1 through the two driving devices and extends from the open end of the housing 1 so as to load the concrete sample.

[0049] The dustproof enclosure 4 is fixedly connected to the top surface of the loading platform 2. A notch is arranged on one side of the dustproof enclosure 4 close to the open end of the shell 1. Clamping devices are arranged on both sides of the inner cavity of the dustproof enclosure 4. The clamping devices are used to clamp the ends of the concrete sample. The two clamping devices are transmission-connected to the same stretching device. The two clamping devices move toward or away from each other through the stretching device.

[0050] A lifting plate 5 and a through hole are provided on the top surface of the loading platform 2, the lifting plate 5 is located in the through hole, and a lifting device is provided on the bottom surface of the lifting plate 5, the lifting device is used to lift the concrete sample so that both ends of the concrete sample enter into the two clamping devices for clamping.

[0051] The loading platform 2 is extended from the open end of the shell 1 to place the concrete sample, so as to realize the loading of the concrete sample. The driving device can drive the loading platform 2 to extend or retract from the open end of the shell 1. After the loading platform 2 retracts and resets, the lifting plate 5 is driven by the lifting device to lift up a distance. The stretching device drives the two clamping devices to move and then clamp and fix the concrete sample. The stretching device is driven to drive the two clamping devices to move in opposite directions to realize the tensile test of the concrete sample. The clamping device can clamp and fix concrete samples of different sizes, thereby improving adaptability.

[0052] Existing fatigue tests are all exposed tests. The dustproof enclosure 4 provided in the present invention can shield the broken concrete sample fragments, thereby avoiding injuries to test personnel due to brittle failure in fatigue tests of quasi-brittle materials such as concrete, and is convenient for cleaning after the loading platform 2 is extended from the shell 1.

[0053] Further optimizing the solution, the clamping device includes:

[0054] A clamping frame 6, which is transmission-connected to the stretching device;

[0055] The clamping plate 7 is located at the top of the inner cavity of the clamping frame 6. The top surface of the clamping frame 6 is fixedly connected with a cylinder 8. The output end of the cylinder 8 passes through the clamping frame 6 and is fixedly connected to the top surface of the clamping plate 7. The clamping plate 7 and the bottom surface of the inner cavity of the clamping frame 6 clamp the concrete sample.

[0056] The set stretching device drives the two clamping frames 6 to move toward each other, so that the two ends of the concrete sample can be inserted into the clamping frame 6, and the cylinder 8 drives the clamping plate 7 to move to achieve the clamping and fixation of the concrete sample. At the same time, the jacking device is reset, and the stretching device drives the clamping device to perform the stretching test.

[0057] Further optimization scheme, the stretching device includes:

[0058] A stretching motor 9, which is fixed to one side of the dustproof enclosure 4;

[0059] A stretching bidirectional screw 10, wherein the output end of the stretching motor 9 is fixedly connected to one end of the stretching bidirectional screw 10, and the other end of the stretching bidirectional screw 10 is rotatably connected to the inner wall of the dustproof enclosure 4;

[0060] The stretching block 11 is fixedly connected to the clamping frame 6, and the stretching bidirectional screw 10 passes through the stretching block 11 and is connected to the stretching block 11 by threads;

[0061] The stretching guide rod 12 has two ends fixedly connected to two sides of the dustproof enclosure 4 , and the stretching guide rod 12 passes through the stretching block 11 and is in sliding contact with the stretching block 11 .

[0062] The stretching guide rod 12 is provided to play a guiding role, and the stretching motor 9 is provided to drive the stretching bidirectional screw 10 to rotate, so as to realize the synchronous displacement of the two clamping frames 6 toward or away from each other.

[0063] To further optimize the solution, the lifting device includes:

[0064] Two lifting seats 13 are fixedly connected to the bottom surface of the shell 1, two lifting guide rods 14 are fixedly connected between the two lifting seats 13, a lifting bidirectional screw 15 is rotatably connected between the two lifting guide rods 14, one end of the lifting bidirectional screw 15 passes through the output end of one of the lifting seats 13 fixedly connected to a lifting motor 16, the lifting guide rod 14 and the lifting bidirectional screw 15 are penetrated by two lifting blocks 17, the lifting block 17 is in sliding contact with the lifting guide rod 14, the lifting block 17 is connected to the lifting bidirectional screw 15 by threads, a lifting hole is opened on the bottom surface of the shell 1, one end of a lifting rod 18 is hingedly provided on the two lifting blocks 17, the other end of the lifting rod 18 passes through the lifting hole and is hinged to the lifting plate 5, a plurality of lifting limit rods 3 are fixedly connected to the bottom surface of the lifting plate 5, the lifting limit rod 3 passes through the bottom surface of the shell 1 and is in sliding contact with the shell 1.

[0065] The provided lifting motor 16 drives the lifting bidirectional screw 15 to rotate, thereby driving the two lifting blocks 17 to move toward or away from each other synchronously, and the provided lifting limit rod 3 plays a limiting role, thereby realizing the lifting and lowering of the lifting plate 5.

[0066] Further optimization plans also include:

[0067] The pressing plate 19 is arranged at the top of the inner cavity of the shell 1. The top surface of the pressing plate 19 is fixedly connected with a connecting block 20. The connecting block 20 is fixedly connected with a pressing device. The pressing plate 19 presses the concrete sample through the pressing device.

[0068] Further optimization scheme, the pressing device includes:

[0069] Two lower pressing seats 21 are fixedly connected to the top surface of the shell 1, two lower pressing guide rods 22 are fixedly connected between the two lower pressing seats 21, and a lower pressing bidirectional screw 23 is rotatably connected between the two lower pressing guide rods 22. One end of the lower pressing bidirectional screw 23 passes through one of the lower pressing seats 21 and is fixed to the output end of a lower pressing motor 24. The lower pressing guide rod 22 and the lower pressing bidirectional screw 23 are penetrated by two lower pressing blocks 25, and the lower pressing blocks 25 are in sliding contact with the lower pressing guide rod 22. The lower pressing blocks 25 are connected to the lower pressing bidirectional screw 23 by threads. A lower pressing hole is opened on the top surface of the shell 1, and one end of a lower pressing rod 26 is hingedly set on the two lower pressing blocks 25, and the other end of the lower pressing rod 26 passes through the lower pressing hole and is hinged to the connecting block 20. A plurality of lower pressing limit rods 35 are fixedly connected to the top surface of the pressing plate 19, and the lower pressing limit rods 35 pass through the top surface of the shell 1 and are in sliding contact with the shell 1.

[0070] The working principle of the set down-pressing device is the same as that of the jacking device, and the pressing plate 19 is driven to perform pressure testing on the concrete sample.

[0071] Further optimizing the scheme, the driving device includes:

[0072] A driving motor 27, the driving motor 27 is fixedly connected to the inner wall of the housing 1, one end of a driving screw 28 is fixedly connected to the output end of the driving motor 27, and the other end of the driving screw 28 is rotatably connected to the inner wall of the housing 1;

[0073] The driving block 29 is fixedly connected to the loading platform 2 , and the driving screw 28 passes through the driving block 29 and is connected to the driving block 29 by threads.

[0074] The drive motor 27 drives the drive screw 28 to rotate, thereby achieving the displacement of the drive block 29, so that the loading platform 2 can be extended or retracted from the housing 1.

[0075] Further optimization plans also include:

[0076] Two slide rails 30 are respectively fixed to the bottom surface of the inner cavity of the shell 1, and sliders 31 are respectively fixed to both sides of the bottom surface of the loading platform 2. The bottom surface of the slider 31 is provided with a slide groove adapted to the slide rail 30, and the inner wall of the slide groove is in sliding contact with the slide rail 30.

[0077] The provided slide block 31 and the slide rail 30 have a limiting effect on the displacement of the loading platform 2, thereby ensuring the stability of the displacement.

[0078] According to a further optimization scheme, a box door 32 is provided at the open end of the shell 1 , a rectangular hole is provided in the middle of the box door 32 , a tempered glass is fixed in the rectangular hole, and a handle 33 is fixed to the box door 32 .

[0079] According to a further optimized solution, support legs 34 are fixedly connected to the four corners of the bottom surface of the shell 1 .

[0080] In actual engineering, concrete specimens are all under bidirectional or tri-directional loads, and rarely under unidirectional tension or compression. In order to be more consistent with actual engineering, when using the fatigue testing machine of the present invention to perform fatigue tests on concrete brittle materials, the testing machine can not only perform unidirectional tension or unidirectional compression, but also clamp the concrete specimen at both ends through two clamping devices in actual operation, and simultaneously open the tension device and the pressing device to simultaneously realize the tension and compression bidirectional tests on the concrete specimens. It can also perform axial tension fatigue tests under the condition of setting a certain compressive load as required, or perform compression fatigue tests under the condition of setting a certain axial tensile load as required. Thus, fatigue tests of unidirectional tension, compression, and simultaneous tension and compression loading on concrete specimens can be realized.

[0081] In the actual test process, by cyclically driving the pressing device and the stretching device, tensile or compressive loads within a certain load range are repeatedly applied to the concrete specimen. For example, the concrete specimen is stretched to 5kN, unloaded to 0Kn, stretched to 5kN, unloaded to 0kN... and repeated cycles. Then, by obtaining test data, fatigue testing of the concrete specimen is achieved.

[0082] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0083] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A concrete-like quasi-brittle material tension-compression-tension-compression fatigue testing machine, characterized in that: include: A housing (1), one side of the housing (1) being configured as an open end, A loading platform (2), the loading platform (2) being arranged inside the shell (1), and drive devices being arranged on both sides of the loading platform (2), the loading platform (2) sliding relative to the shell (1) through the two drive devices and extending from the open end of the shell (1) so as to load a concrete sample; A dustproof enclosure (4), the dustproof enclosure (4) being fixedly connected to the top surface of the loading platform (2), a notch being arranged on one side of the dustproof enclosure (4) close to the open end of the shell (1), clamping devices being arranged on both sides of the inner cavity of the dustproof enclosure (4), the clamping devices being used to clamp the ends of the concrete sample, the two clamping devices being transmission-connected to the same stretching device, and the two clamping devices being moved toward or away from each other through the stretching device; A lifting plate (5), wherein a through hole is provided on the top surface of the loading platform (2), the lifting plate (5) is located in the through hole, and a lifting device is provided on the bottom surface of the lifting plate (5), the lifting device is used to lift the concrete sample so that both ends of the concrete sample enter the two clamping devices for clamping.

2. A concrete-like quasi-brittle material tension-compression-tension-compression fatigue testing machine according to claim 1, characterized in that: The clamping device comprises: A clamping frame (6), the clamping frame (6) being transmission-connected to the stretching device; A clamping plate (7), the clamping plate (7) is located at the top of the inner cavity of the clamping frame (6), the top surface of the clamping frame (6) is fixedly connected to a cylinder (8), the output end of the cylinder (8) passes through the clamping frame (6) and is fixedly connected to the top surface of the clamping plate (7), and the clamping plate (7) and the bottom surface of the inner cavity of the clamping frame (6) clamp the concrete sample.

3. A concrete-like quasi-brittle material tension-compression-tension-compression fatigue testing machine according to claim 2, characterized in that: The stretching device comprises: A stretching motor (9), wherein the stretching motor (9) is fixedly connected to one side of the dustproof enclosure (4); A stretching bidirectional screw (10), wherein the output end of the stretching motor (9) is fixedly connected to one end of the stretching bidirectional screw (10), and the other end of the stretching bidirectional screw (10) is rotatably connected to the inner wall of the dustproof enclosure (4); A stretching block (11) is fixedly connected to the clamping frame (6); the stretching bidirectional screw (10) passes through the stretching block (11) and is connected to the stretching block (11) by means of a thread; A stretching guide rod (12), the two ends of which are respectively fixedly connected to the two sides of the dustproof enclosure (4), and the stretching guide rod (12) passes through the stretching block (11) and is in sliding contact with the stretching block (11).

4. The concrete-like quasi-brittle material tension-compression-tension-compression fatigue testing machine according to claim 1, characterized in that: The lifting device comprises: Two lifting seats (13), the two lifting seats (13) are fixedly connected to the bottom surface of the shell (1), two lifting guide rods (14) are fixedly connected between the two lifting seats (13), a lifting bidirectional screw (15) is rotatably connected between the two lifting guide rods (14), one end of the lifting bidirectional screw (15) passes through the output end of a lifting motor (16) fixedly connected to one of the lifting seats (13), two lifting blocks (17) are arranged through the lifting guide rods (14) and the lifting bidirectional screw (15), and the lifting blocks (17) are connected to the lifting guide rods (14) and the lifting guide rods (15). The lifting guide rod (14) is in sliding contact, the lifting block (17) is connected to the lifting bidirectional screw (15) by threads, the bottom surface of the shell (1) is provided with a lifting hole, one end of the lifting rod (18) is hingedly provided on the two lifting blocks (17), the other end of the lifting rod (18) passes through the lifting hole and is hingedly connected to the lifting plate (5), and a plurality of lifting limit rods (3) are fixedly connected to the bottom surface of the shell (1), and the lifting limit rods (3) pass through the bottom surface of the shell (1) and are in sliding contact with the shell (1).

5. The concrete-like quasi-brittle material tension-compression-tension-compression fatigue testing machine according to claim 1, characterized in that: Also includes: A pressing plate (19), the pressing plate (19) being arranged at the top of the inner cavity of the shell (1), the top surface of the pressing plate (19) being fixedly connected to a connecting block (20), the connecting block (20) being fixedly connected to a pressing device, and the pressing plate (19) applying pressure to the concrete sample through the pressing device.

6. A concrete-like quasi-brittle material tension-compression-tension-compression fatigue testing machine according to claim 5, characterized in that: The pressing device comprises: Two lower pressing seats (21), the two lower pressing seats (21) are fixedly connected to the top surface of the shell (1), two lower pressing guide rods (22) are fixedly connected between the two lower pressing seats (21), a lower pressing bidirectional screw rod (23) is rotatably connected between the two lower pressing guide rods (22), one end of the lower pressing bidirectional screw rod (23) passes through the output end of a lower pressing motor (24) fixedly connected to one of the lower pressing seats (21), the lower pressing guide rod (22) and the lower pressing bidirectional screw rod (23) are penetrated by two lower pressing blocks (25), the lower pressing blocks (25) and the lower pressing guide rod (22) are connected to the lower pressing guide rod (23) and the lower pressing guide rod (22). The pressing guide rod (22) is in sliding contact, the pressing block (25) is connected to the pressing bidirectional screw (23) by threads, the top surface of the shell (1) is provided with a pressing hole, one end of a pressing rod (26) is hingedly provided on the two pressing blocks (25), the other end of the pressing rod (26) passes through the pressing hole and is hingedly connected to the connecting block (20), and a plurality of pressing limit rods (35) are fixedly connected to the top surface of the pressing plate (19), the pressing limit rods (35) pass through the top surface of the shell (1) and are in sliding contact with the shell (1).

7. The concrete-like quasi-brittle material tension-compression-tension-compression fatigue testing machine according to claim 1, characterized in that: The driving device comprises: A driving motor (27), wherein the driving motor (27) is fixedly connected to the inner wall of the housing (1), an output end of the driving motor (27) is fixedly connected to one end of a driving screw rod (28), and the other end of the driving screw rod (28) is rotatably connected to the inner wall of the housing (1); A driving block (29), wherein the driving block (29) is fixedly connected to the loading platform (2), and the driving screw (28) passes through the driving block (29) and is connected to the driving block (29) by means of threads.

8. The concrete-like quasi-brittle material tension-compression-tension-compression fatigue testing machine according to claim 1, characterized in that: Also includes: Two slide rails (30), the two slide rails (30) are respectively fixed to the bottom surface of the inner cavity of the shell (1), and sliders (31) are respectively fixed to both sides of the bottom surface of the loading platform (2), and the bottom surface of the slider (31) is provided with a slide groove matched with the slide rail (30), and the inner wall of the slide groove is in sliding contact with the slide rail (30).

9. The concrete-like quasi-brittle material tension-compression-tension-compression fatigue testing machine according to claim 1, characterized in that: The open end of the housing (1) is provided with a box door (32), a rectangular hole is opened in the middle of the box door (32), a tempered glass is fixed in the rectangular hole, and a handle (33) is fixed on the box door (32).

10. The concrete-like quasi-brittle material tension-compression-tension-compression fatigue testing machine according to claim 1, characterized in that: Support legs (34) are respectively fixedly connected to the four corners of the bottom surface of the shell (1).

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