Synchronous sample clamping device for steel bar tensile test

Abstract

The utility model discloses a synchronous sample clamping device for a steel bar tensile test, which comprises a clamp seat, a left oil cylinder and a right oil cylinder are arranged on the clamp seat, and both the left oil cylinder and the right oil cylinder are connected with a hydraulic power system; the extending directions of a piston rod I of the left oil cylinder and a piston rod II of the right oil cylinder are parallel and opposite, the close ends of the piston rod I and the piston rod II are connected with a clamping plate for clamping a sample, and the other ends of the piston rod I and the piston rod II are fixedly provided with pistons which slide in the cylinder barrel in a matched manner. The synchronous shunt motor is arranged between the left oil cylinder and the hydraulic power system and between the right oil cylinder and the hydraulic power system, so that the left oil cylinder and the right oil cylinder are synchronized with high precision, the action time is shortened, and the system is simple in structure, low in failure rate and good in using effect. And the piston rod anti-rotation structures are arranged on the piston rod I and the piston rod II, so that the piston rods can be prevented from rotating, the clamping coaxiality and perpendicularity of the jaw are ensured, a sample is convenient to clamp, and the test precision is improved.

Description

Technical Field

[0001] The utility model relates to a universal material testing machine, in particular to a sample synchronous clamping device for steel bar tensile testing, belonging to the technical field of testing equipment. Background Art

[0002] In the field of building material testing, steel bar tensile testing is a routine testing content. By applying axial tension to the steel bar, the bond strength that can be achieved between the steel bar and concrete can be judged. Among them, the tensile strength, elongation and yield strength of the steel bar are the three most basic mechanical property indexes of the steel bar, and these three indexes are all obtained through steel bar tensile testing. The steel bar tensile testing uses a tensile testing machine, which mainly includes a frame composed of a base, columns and an upper crossbeam. A moving crossbeam is slidably arranged on the columns, and an upper clamp is installed on the moving crossbeam. A lower clamp is installed on the base. The upper clamp and the lower clamp respectively clamp the two ends of the steel bar. The main hydraulic cylinder drives the moving crossbeam to move upward, so that the steel bar is continuously stretched at both ends until the steel bar breaks. Since the steel bar needs to bear axial tension, reliable fixation is required for both ends of the steel bar. Currently, most of the clamps used in the test device to clamp the steel bar are wedge-shaped clamps. However, this wedge-shaped clamp is a passive clamp, and its clamping effect is related to the test force and the state of the clamping block. When the test force is greater, the clamping force is also greater. But when the test force suddenly disappears (i.e., the sample breaks), the clamping force also suddenly disappears, and the phenomenon of the clamp suddenly loosening will occur. At this time, due to the inertial effect of the original force, an impact will be generated on the clamp, resulting in relatively serious vibration and noise. In addition, when the upper jaw device and the lower jaw device clamp the sample, since the clamping block is driven by a hydraulic cylinder to drive the power driving plate to push and move upward together with the slider, during the upward movement of the left and right clamping blocks, a horizontal movement towards each other is generated at the same time to clamp the sample. The upper jaw device and the lower jaw device will apply a compressive force towards each other to the sample in the axial direction, resulting in the bending of the sample with a smaller diameter, and even the sample of brittle material will be damaged. There is also a hydraulic flat-push clamp. The hydraulic flat-push clamp uses the oil source pressure as the power to parallelly push the clamping pistons in the two cylinders on both sides of the clamp body to move, so as to achieve the purpose of clamping the sample, and has the advantages of large clamping force and good clamping effect. However, there are still certain defects. One is that the piston rod may rotate during work, affecting the clamping of the sample and the test accuracy. The other is that the two hydraulic cylinders are not easy to be synchronized, resulting in inconsistent clamping jaw extension speeds and misalignment of the clamping jaw clamping positions, causing the axis of the sample to be inconsistent with the force application axis of the loading mechanism, resulting in the force application of the loading mechanism being skewed during the test, affecting the authenticity and accuracy of the test parameters, and easily damaging the loading mechanism. When fixing the steel bar sample, in order to ensure that the steel bar sample is perpendicular to the ground and consistent with the force application axis of the loading mechanism, the position of the steel bar needs to be adjusted repeatedly. When adjusting the position of the steel bar, the clamp may need to be loosened repeatedly, which may lead to more cumbersome adjustment of the steel bar. Summary of the Invention

[0003] The purpose of the present utility model is to provide a sample synchronous clamping device for steel bar tensile test in view of the deficiencies existing in the prior art, so as to solve the problems existing in the background art.

[0004] To achieve the above object, the present utility model adopts the following technical solutions:

[0005] A sample synchronous clamping device for steel bar tensile test, comprising a fixture base, on which two oil cylinders are arranged on the left and right. The left oil cylinder and the right oil cylinder are both connected to a hydraulic power system; the extending directions of the piston rod I of the left oil cylinder and the piston rod II of the right oil cylinder are parallel, and the extending directions are opposite. The adjacent ends of the piston rod I and the piston rod II are connected to a clamping plate for clamping the sample, and the other ends of the piston rod I and the piston rod II are fixedly installed with pistons that fit and slide in the cylinder barrel. It is characterized in that: a synchronous flow dividing motor is provided between the left oil cylinder, the right oil cylinder and the hydraulic power system; and a piston rod anti-rotation structure is provided on the piston rod I and the piston rod II.

[0006] By adopting the above technical solutions, the sample clamping device adopts a hydraulic flat-push fixture, which is an active fixture. Its clamping force has nothing to do with the loading force of the test, and this clamping force acts directly on the sample. Through the proportional overflow valve, the pressure of the hydraulic system can be continuously adjusted directly on the software as needed. Through the joint control of the overflow valve and the software, the clamping force can be adjusted according to the material of the sample. During the whole test process, no matter how large the loading force of the test is, the clamping force always continuously clamps the sample, and this clamping force will not disappear when the sample breaks. The structural characteristics of the flat-push fixture can also keep no relative slip between the jaws and the fixture base during the test process, which can better fix the sample during the test process and will not generate axial force affecting the test in the tensile direction. The influence of the fixture system on the test result is small, making the result closer to the true value. The piston rod anti-rotation structure is provided on the piston rod, which can prevent the piston rod from rotating, ensure the coaxiality and perpendicularity of the jaw clamping, facilitate the clamping of the sample and improve the test accuracy.

[0007] A high-precision synchronous flow dividing motor is arranged between the left oil cylinder, the right oil cylinder and the hydraulic power system, so that the left oil cylinder and the right oil cylinder achieve high-precision synchronization, shorten the action time, and the system has a simple structure, low failure rate and good use effect.

[0008] In the above-mentioned sample synchronous clamping device for steel bar tensile test, a U-shaped groove is provided in the middle of the fixture base, and the left oil cylinder and the right oil cylinder are symmetrically arranged on both sides of the U-shaped groove. The ends of the piston rod I and the piston rod II move towards each other from both sides of the U-shaped groove and extend into the U-shaped groove.

[0009] By adopting the above technical solution, a U-shaped groove is provided in the middle of the fixture base, and the left oil cylinder and the right oil cylinder are symmetrically arranged on both sides of the U-shaped groove. The advantage of this arrangement is that the left oil cylinder and the right oil cylinder are simultaneously arranged on one fixture base, which can improve the overall rigidity of the fixture, easily maintain the parallelism of the clamping surfaces of the two clamping plates, and improve the clamping accuracy and clamping force of the jaws.

[0010] In the above-described sample synchronous clamping device for a steel bar tensile test, the anti-rotation structure of the piston rod is an eccentric structure of piston rod I, piston rod II and the piston. The axes of piston rod I and piston rod II have an eccentricity δ with the axis of the piston and are parallel to each other.

[0011] By adopting the above technical solution, the axis of the piston rod and the piston has a certain eccentricity, the structure is simple, easy to process, and the anti-rotation of the piston rod can be achieved at a relatively low cost.

[0012] In the above-described sample synchronous clamping device for a steel bar tensile test, the distance between the lower end of the clamping plate and the bottom of the U-shaped groove allows the working end of the sample fixture to pass through.

[0013] By adopting the above technical solution, the distance between the lower end of the clamping plate and the bottom of the U-shaped groove allows the working end of the sample fixture to pass through, which is convenient for the robot to drive the sample fixture to grab the sample waste after the test.

[0014] Further, the hydraulic power system includes a servo motor and an oil pump, a check valve, a proportional relief valve, a pressure transmitter, and a solenoid directional valve connected by pipelines; the oil pump is driven by the servo motor, the inlet ports of the proportional relief valve, the pressure transmitter, and the check valve are connected to the outlet of the oil pump, the outlet port of the check valve is connected to the inlet port of the solenoid directional valve, and the working oil ports of the solenoid directional valve are connected to the left and right oil cylinders; the synchronous flow dividing motor is arranged between the solenoid directional valve and the left and right oil cylinders.

[0015] By adopting the above technical solutions, the proportional overflow valve can directly and continuously adjust the pressure of the hydraulic system on the software as needed. Through the joint control of the overflow valve and the software, the clamping force can be adjusted according to the material of the specimen. By setting a pressure transmitter, the output pressure of the oil pump can be monitored in real time. Before the clamping device works, the left oil cylinder, the right oil cylinder and the pipeline are filled with hydraulic oil. During operation, the servo motor drives the oil pump to work, and supplies oil to the left oil cylinder and the right oil cylinder through the pipeline, pushing the piston rod I and the piston rod II to extend towards each other. The pressure transmitter detects the oil pressure of the system in real time and feeds it back to the control system. The control system compares the actually measured oil pressure with the set load value (i.e., the clamping force value set according to the size and material of the specimen). If the measured value is less than the set value, it means that the fixture has not clamped the specimen yet, and the servo motor runs at high speed. When the fixture clamps the specimen, the measured value will rise rapidly until it reaches the set value. The control system controls the servo motor to continue running at high speed for a certain period of time (such as 30 seconds) to ensure that the specimen is clamped tightly; then it controls the servo motor to maintain low-speed operation and keep the set clamping force to make the system pressure constant. In this way, the system power of the oil source is reduced, not only reducing energy consumption, but also reducing the temperature of the hydraulic oil in the system. Beneficial effects

[0016] 1. The specimen clamping device adopts a hydraulic flat-push fixture, whose clamping force has nothing to do with the loading force of the test and acts directly on the specimen. During the test process, no matter how large the loading force of the test is, the clamping force continuously clamps the specimen. When the specimen breaks, the clamping force will not disappear, and it can keep no relative slip between the jaws and the fixture base during the test process, and there will be no axial force affecting the test in the tensile direction. The influence of the fixture system on the test result is small, making the result closer to the true value. A piston rod anti-rotation structure is set on the piston rod, which can prevent the piston rod from rotating, ensure the coaxiality and perpendicularity of the jaw clamping, facilitate the clamping of the specimen and improve the test accuracy.

[0017] 2. A high-precision synchronous flow dividing motor is set between the left oil cylinder, the right oil cylinder and the hydraulic power system, enabling the left oil cylinder and the right oil cylinder to achieve high-precision synchronization, shortening the action time, and the system has a simple structure, low failure rate and good use effect.

[0018] 3. The left oil cylinder and the right oil cylinder are both set on a fixture base, which can improve the overall rigidity of the fixture, easily maintain the parallelism of the clamping surfaces of the two clamping plates, and improve the clamping accuracy and clamping force of the jaws.

[0019] 4. The distance between the lower end of the clamping plate and the bottom of the U-shaped groove allows the working end of the specimen fixture to pass through, facilitating the robot to drive the specimen fixture to grab the specimen waste after the test. Description of the drawings

[0020] Figure 1 is the overall schematic diagram of the present invention.

[0021] Figure 2 This is a schematic diagram showing the specimen clamped on the specimen clamping device in the present utility model.

[0022] Figure 3 This is a cross-sectional schematic diagram of the lower clamp in the present utility model.

[0023] Figure 4 This is an overall schematic diagram of the lower clamp in the present utility model.

[0024] Figure 5 This is an overall schematic diagram of the hydraulic system.

[0025] Figure 6 This is a schematic diagram of the hydraulic system principle.

[0026] In the figure: 1 base, 2 loading oil cylinder, 3 moving crossbeam, 4 column, 5 upper crossbeam, 6 upper clamp, 7 lower clamp, 8 left oil cylinder, 9 right oil cylinder, 10 piston hole, 11 piston, 12 clamp seat, 13 piston rod I, 14 clamping plate, 15 piston rod II, 16 U-shaped groove, 17 main oil pump, 18 clamp oil pump, 19 servo motor, 20 proportional overflow valve, 21 pressure transmitter, 22 check valve, 23 upper clamp pipeline, 24 upper clamp electromagnetic directional valve, 25 upper clamp synchronous flow dividing motor, 26 lower clamp pipeline, 27 lower clamp electromagnetic directional valve, 28 lower clamp synchronous flow dividing motor, 29 oil tank. Embodiment

[0027] To clearly illustrate the technical features of this solution, the present utility model will be further described below through non-limiting embodiments in conjunction with the accompanying drawings.

[0028] The front, rear, left, and right directions described in the present utility model are based on the front, rear, left, and right directions shown in the accompanying drawings. For the sake of convenience of description, only parts related to the embodiments of the present utility model are shown.

[0029] Please refer to Figure 1 、 Figure 2, A synchronous clamping device for specimens in a steel bar tensile test, comprising a frame composed of a base 1, columns 4, and an upper crossbeam 5. The columns 4 are arranged on the base 1, and the top of the columns 4 is connected to the upper crossbeam 5. A moving crossbeam 3 is located between the base 1 and the upper crossbeam 5 and is slidably arranged on the columns 4. An upper clamp 6 is installed on the moving crossbeam 3, and a lower clamp 7 is correspondingly installed on the base 1. The upper clamp 6 and the lower clamp 7 respectively clamp the two ends of the steel bar, and the moving crossbeam 3 is driven by a test loading device to conduct a tensile test; The test loading device includes 1 loading cylinder 2 on each of the left and right sides. The two loading cylinders 2 can simultaneously drive the moving crossbeam 3 to make the lifting of the moving crossbeam 3 more stable; The cylinder body of the loading cylinder 2 is connected to the base 1.

[0030] Specifically, please refer to Figure 2 to Figure 4 , The upper clamp 6 and the lower clamp 7 have the same structure, both including a clamp seat 12. For the convenience of installation and maintenance during use, in this embodiment, the clamp seat 12 is detachably connected to the base 1 / moving crossbeam 3, for example, by a bolt connection method. The clamp seat 12 is provided with bolt holes, and the upper clamp 6 and the lower clamp 7 are connected to the base 1 / moving crossbeam 3 of the testing machine through bolts. The two ends of the specimen are respectively clamped on the upper clamp 6 and the lower clamp 7, and the test loading device drives the moving crossbeam 3 to conduct a tensile test on the specimen.

[0031] The following is a specific description of the lower fixture 7 only. There are two oil cylinders, a left oil cylinder 8 and a right oil cylinder 9, arranged on the fixture base 12, and both the left oil cylinder 8 and the right oil cylinder 9 are connected to the hydraulic power system; in this embodiment, a U-shaped groove 16 is provided in the middle of the fixture base 12, and the left oil cylinder 8 and the right oil cylinder 9 are symmetrically arranged on both sides of the U-shaped groove 16. The cylinder barrel of the oil cylinder and the fixture base 12 are of an integral structure. Specifically, cylinder head holes are respectively provided on both sides of the U-shaped groove 16 on the fixture base 12, and piston holes 10 are provided outside the cylinder head holes. The piston 11 is located in the piston hole 10 and is connected to the piston rod. The piston 11 and the piston rod can also be an integrally formed piston assembly. The piston 11 divides the piston hole 10 into a rod chamber and a rodless chamber. The fixture base 12 is provided with a rod chamber oil port and a rodless chamber oil port (not shown in the figure) respectively connected to the rod chamber and the rodless chamber, and the rod chamber oil port and the rodless chamber oil port are connected to the hydraulic power system through pipelines. The end parts of the piston rod I13 of the left oil cylinder 8 and the piston rod II15 of the right oil cylinder 9 respectively extend into the U-shaped groove 16 from the cylinder head holes on both sides of the U-shaped groove 16 in opposite directions. The extending direction of the piston rod I13 of the left oil cylinder 8 and the piston rod II15 of the right oil cylinder 9 is parallel, and the extending directions are opposite. The closer ends of the piston rod I13 and the piston rod II15 are connected to the clamping plate 14 for clamping the specimen, and the other ends of the piston rod I13 and the piston rod II15 are fixedly installed with pistons 11 that slide in cooperation with the cylinder barrel. Anti-rotation structures are provided on both the piston rod I13 and the piston rod II15. Specifically, the anti-rotation structure is an eccentric structure of the piston rod I, the piston rod II15 and the piston 11. The axes of the piston rod I and the piston rod II have an eccentricity δ with the axis of the piston 11 and are parallel to each other. In this embodiment, the eccentricity δ is 3 mm.

[0032] The distance between the lower end of the clamping plate 14 and the bottom of the U-shaped groove 16 allows the working end of the specimen fixture to pass through.

[0033] In order to achieve the synchronous operation of the piston rods of the left oil cylinder 8 and the right oil cylinder 9, a synchronous flow dividing motor is provided between the left oil cylinder 8, the right oil cylinder 9 and the hydraulic power system; please refer to Figure 5 , Figure 6 , the hydraulic power system specifically includes a servo motor 19 and a fixture oil pump 18, a check valve 22, a proportional relief valve 20, a pressure transmitter 21, an upper fixture solenoid directional valve 24, and a lower fixture solenoid directional valve 27 connected through pipelines; specifically, by Figure 6It can be seen that the pipeline on the left is the connecting pipeline of the loading cylinder 2. The two loading cylinders 2 are driven by the main oil pump 17, which is prior art and will not be elaborated here. The pipeline in the middle and the pipeline on the right are the connecting pipelines of the cylinders of the upper fixture 6 and the lower fixture 7 of the specimen synchronous clamping device. The main oil pump 17 and the fixture oil pump 18 share a fuel tank 29. The cylinders of the upper fixture 6 and the lower fixture 7 are driven by a shared fixture oil pump 18. The fixture oil pump 18 is driven by a servo motor 19. The inlet of the oil pump is connected to the fuel tank 29, and the outlet of the oil pump is connected to the inlet of the check valve 22. The outlet of the check valve 22 is connected to the upper fixture pipeline 23 and the lower fixture pipeline 26. The upper fixture pipeline 23 includes an upper fixture electromagnetic directional control valve 24, an upper fixture synchronous flow dividing motor 25, the left cylinder 8 and the right cylinder 9 of the upper fixture. The lower fixture pipeline 26 includes a lower fixture electromagnetic directional control valve 27, a lower fixture synchronous flow dividing motor 28, the left cylinder 8 and the right cylinder 9 of the lower fixture 7. The upper fixture pipeline 23 and the lower fixture pipeline 26 are in a parallel relationship. Only the upper fixture pipeline 23 will be described below. The inlet of the upper fixture electromagnetic directional control valve 24 is connected to the outlet of the check valve 22. The oil return port of the upper fixture electromagnetic directional control valve 24 is connected to the fuel tank 29 through an oil return pipeline. The inlet end of the upper fixture synchronous flow dividing motor 25 is connected to the working oil port A of the upper fixture electromagnetic directional control valve 24 through a connecting pipeline. The outlet end of the upper fixture synchronous flow dividing motor 25 is respectively connected to the inlets of the left cylinder 8 and the right cylinder 9 of the upper fixture 6. The left cylinder 8 and the right cylinder 9 of the upper fixture 6 have the same structure and are arranged in parallel. The outlets of the left cylinder 8 and the right cylinder 9 of the upper fixture 6 are connected to the working oil port B of the upper fixture electromagnetic directional control valve 24 through pipelines. The upper fixture electromagnetic directional control valve 24 and the lower fixture electromagnetic directional control valve 27 are both connected to the programmable logic controller PLC through intermediate relays. The programmable logic controller PLC is connected to the upper computer and is controlled by the upper computer.

[0034] In this embodiment, the upper fixture electromagnetic directional control valve 24 and the lower fixture electromagnetic directional control valve 27 adopt double-electric-control three-position center-sealing solenoid valves; the proportional overflow valve adopts the TDBET6 type proportional overflow valve produced by Shandong Taifeng Hydraulic Co., Ltd.; the pressure transmitter adopts the CY11211AH23V510SG5 pressure transmitter produced by Beijing Xingyi Sensor Technology Co., Ltd.; the upper fixture synchronous flow dividing motor 25 and the lower fixture synchronous flow dividing motor 28 adopt high-precision gear type hydraulic synchronous flow dividing motors without overflow valves.

[0035] The working principle of this embodiment:

[0036] In an actual tensile test, first, the robot drives the specimen fixture to grasp the specimen, and then the two ends of the specimen are respectively placed into the upper fixture 6 and the lower fixture 7. The hydraulic power system drives the left oil cylinder 8 and the right oil cylinder 9 to act. The piston rod I of the left oil cylinder 8 and the piston rod II of the right oil cylinder 9 on the fixture seat 12 extend simultaneously and move towards each other. The clamping plates 14 at the ends of the piston rod I and the piston rod II approach each other to clamp the specimen. Then, the pressure testing machine is started, and the two loading oil cylinders 2 synchronously drive the moving crossbeam 3 to move upward with the upper fixture 6. The upper end of the specimen moves in a direction away from the lower end, and finally, the tensile test of the specimen to be tested is realized.

[0037] When the hydraulic power system drives the left oil cylinder 8 and the right oil cylinder 9 to act, the fixture oil pump 18 is driven by the servo motor 19 to output hydraulic oil. The hydraulic oil supplies oil to the upper fixture pipeline 21 and the lower fixture pipeline 25 through the one-way valve 20. In the upper fixture pipeline 21, the hydraulic oil first passes through the upper fixture electromagnetic directional valve 22 and the upper fixture synchronous flow dividing motor 24 in sequence. After being divided by the upper fixture synchronous flow dividing motor 24, the hydraulic oil enters the left oil cylinder 8 and the right oil cylinder 9 of the upper fixture 6 respectively. After flowing out of the left oil cylinder 8 and the right oil cylinder 9 of the upper fixture 6, the hydraulic oil returns to the upper fixture electromagnetic directional valve 22 and finally enters the fuel tank 29. Similarly, in the lower fixture pipeline 25, the hydraulic oil first passes through the lower fixture electromagnetic directional valve 26 and the lower fixture synchronous flow dividing motor 28 in sequence. After being divided by the lower fixture synchronous flow dividing motor 28, the hydraulic oil enters the left oil cylinder 8 and the right oil cylinder 9 of the lower fixture 7 respectively. After flowing out of the left oil cylinder 8 and the right oil cylinder 9 of the lower fixture 7, the hydraulic oil returns to the lower fixture electromagnetic directional valve 26 and finally enters the fuel tank 29.

[0038] Since the same synchronous motor is installed on the inlet pipelines of the left oil cylinder 8 and the right oil cylinder 9 of the upper fixture 6 / lower fixture 7, and the synchronous motor does not have an overflow valve, the two hydraulic cylinders can act synchronously, stop synchronously and have the same speed. The synchronous clamping of the specimen can be realized.

[0039] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "left", "right", "front", "rear", "upper", "lower", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. The above terms are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention.

[0040] Unless otherwise clearly defined and limited, the terms "installation", "connection", and "linkage" shall be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.

[0041] Except for the technical features described in the specification, the rest are known technologies to those skilled in the art.

[0042] The above-listed embodiments are only for understanding the present utility model and are not limitations on the technical solutions described in the present utility model. Those of ordinary skill in the relevant art can also make various changes or deformations based on the technical solutions described in the claims. All equivalent changes or deformations should be covered within the scope of protection of the claims of the present utility model.

Claims

1. A sample synchronous clamping device for a steel bar tensile test, comprising a fixture base, with two left and right oil cylinders arranged on the fixture base, and both the left oil cylinder and the right oil cylinder are connected to a hydraulic power system; the extending directions of the piston rod I of the left oil cylinder and the piston rod II of the right oil cylinder are parallel, and the extending directions are opposite, and one end of the piston rod I and the piston rod II that are close to each other is connected to a clamping plate for clamping the sample, and the other ends of the piston rod I and the piston rod II are fixedly installed with pistons that fit and slide in the cylinder barrel, and it is characterized in that: A synchronous flow dividing motor is provided between the left oil cylinder and the right oil cylinder and the hydraulic power system; an anti-rotation structure for the piston rod is provided on the piston rod I and the piston rod II.

2. The sample synchronous clamping device for the steel bar tensile test according to claim 1, characterized in that: A U-shaped groove is provided in the middle of the fixture seat, the left oil cylinder and the right oil cylinder are symmetrically arranged on both sides of the U-shaped groove, and the ends of the piston rod I and the piston rod II respectively move towards each other from both sides of the U-shaped groove and extend into the U-shaped groove.

3. The specimen synchronous clamping device for the steel bar tensile test according to claim 1, characterized in that: The anti-rotation structure for the piston rod is an eccentric structure of the piston rod I, the piston rod II and the piston. The axes of the piston rod I and the piston rod II have an eccentricity δ with the axis of the piston and are parallel to each other.

4. The specimen synchronous clamping device for the steel bar tensile test according to claim 1, characterized in that: The distance between the lower end of the clamping plate and the bottom of the U-shaped groove allows the working end of the specimen fixture to pass through.

5. The specimen synchronous clamping device for the steel bar tensile test according to claim 1 or 2 or 3 or 4, characterized in that: The hydraulic power system includes a servo motor and an oil pump, a one-way valve, a proportional overflow valve, a pressure transmitter, and an electromagnetic reversing valve connected by pipelines; the oil pump is driven by the servo motor, the oil inlets of the proportional overflow valve, the pressure transmitter, and the one-way valve are connected to the outlet of the oil pump, the oil outlet of the one-way valve is connected to the oil inlet of the electromagnetic reversing valve, and the working oil ports of the electromagnetic reversing valve are connected to the left and right two oil cylinders; the synchronous flow dividing motor is arranged between the electromagnetic reversing valve and the left and right two oil cylinders.

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