Steel strand fatigue testing machine with replaceable jaw

Abstract

The invention relates to the technical field of steel strand fatigue testing equipment, and particularly discloses a jaw-replaceable steel strand fatigue testing machine which comprises a rack and a pair of concave seats, the pair of concave seats are oppositely arranged in the rack, and first hydraulic oil cylinders are mounted on the two outer walls of each concave seat; first piston rods are arranged at the output ends of the first hydraulic cylinders; connecting plates are arranged at the ends of the first piston rods; a jaw plate is detachably mounted at the end part of the connecting plate; the end face of the jaw plate is provided with a limiting groove capable of being matched with the outer wall of the steel strand. A power mechanism and a connecting mechanism are arranged on the end faces, away from each other, of the pair of concave bases correspondingly. The power mechanism is connected with the top wall of the rack and can drive the concave base connected with the power mechanism to ascend and descend. The connecting mechanism is connected with the inner bottom wall of the rack; the assembling structure of the jaw plate and the connecting plate is arranged to be in an embedded and inserted mode, so that the jaw plate can be conveniently and rapidly assembled and disassembled, a worker can conveniently replace the corresponding jaw plate according to the to-be-tested steel strand, and the testing efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of fatigue testing equipment for steel strands, and in particular to a fatigue testing machine for steel strands with interchangeable jaws. Background Technology

[0002] As a key material in prestressed concrete structures, the fatigue performance of steel strand directly affects the safety and durability of the structure. Currently, the demand for testing the fatigue performance of steel strand is increasing both domestically and internationally; however, traditional fatigue testing machines suffer from problems such as severe jaw wear and low replacement efficiency.

[0003] Existing testing machines mostly adopt an integrated jaw design. When changing steel strands of different specifications and sizes for fatigue testing, the machine needs to be stopped, the entire machine disassembled, and the jaws replaced, which seriously affects testing efficiency and increases maintenance costs. Summary of the Invention

[0004] This application provides a steel strand fatigue testing machine with interchangeable jaws, which features an interlocking assembly structure for the jaw plate and connecting plate, allowing for convenient installation and removal of the jaw plate. This enables operators to replace the corresponding jaw plate according to the steel strand to be tested, thereby improving testing efficiency.

[0005] This application provides a steel strand fatigue testing machine with interchangeable jaws, which adopts the following technical solution: A steel strand fatigue testing machine with replaceable jaws includes a frame and a pair of concave seats. The pair of concave seats are arranged opposite each other inside the frame, and each concave seat has a first hydraulic cylinder horizontally mounted on its two mutually distant outer walls. The output end of the first hydraulic cylinder is provided with a first piston rod extending into the concave seat. A connecting plate is provided at the end of the first piston rod. A jaw plate is detachably installed on the end of the connecting plate away from the first piston rod. A limiting groove that can mate with the outer wall of the steel strand is opened on the end face of the jaw plate away from the connecting plate. A power mechanism and a connecting mechanism are respectively provided on the mutually distant end faces of the pair of concave seats. The power mechanism is connected to the top wall of the frame and can drive the concave seats connected thereto to move up and down. The connecting mechanism is connected to the inner bottom wall of the frame.

[0006] By adopting the above technical solution, during the fatigue test of steel strand, the steel strand is placed between two concave seats. The two first hydraulic cylinders on the concave seats are activated, causing the two connecting plates inside the concave seats to move towards each other and clamp the steel strand using jaw plates. The limiting groove set on the end face of the jaw plates can cooperate with the outer wall of the end face of the steel strand to limit the movement of the steel strand. When the size of the steel strand changes, the jaw plates that are compatible can be replaced, avoiding the trouble of disassembling and replacing the entire jaws, improving the efficiency of the test and reducing maintenance costs. The power mechanism is used to apply force to the steel strand during the test.

[0007] Preferably, the end face of the connecting plate near the jaw plate has a slot; the end face of the jaw plate near the connecting plate is fixedly connected to a locking block that can be inserted into the slot; the locking block slides in cooperation with the inner wall of the slot.

[0008] By adopting the above technical solution, when assembling the jaw plate, the jaw plate can be assembled by aligning the clamping block with the clamping slot and inserting it into the inner wall of the clamping slot. The assembly structure of the jaw plate and the connecting plate is set to be insert-type, which can facilitate the installation and disassembly of the jaw plate, so that the staff can replace the corresponding jaw plate according to the steel strand to be tested.

[0009] Preferably, the frame includes a base plate and a top plate; a set of columns are vertically and detachably installed on the top surface of the base plate; the top plate is disposed on top of the set of columns and is detachably connected to the set of columns; a pair of concave seats are disposed opposite each other between the base plate and the top plate; the power mechanism is connected to the top plate; and the connecting mechanism is connected to the base plate.

[0010] By adopting the above technical solution, the frame is configured as a structure consisting of a base plate, a top plate, and columns, which facilitates the overall assembly and disassembly of the frame for transportation.

[0011] Preferably, the power mechanism includes a second hydraulic cylinder; the second hydraulic cylinder is vertically mounted on the top surface of the top plate, and a second piston rod penetrating the top plate is provided at the vertical end of the second hydraulic cylinder; the bottom end of the second piston rod is connected to the top surface of the top concave seat among a pair of concave seats.

[0012] By adopting the above technical solution, the second hydraulic cylinder can drive the second piston rod to change the distance between the two concave seats, so as to apply force to the clamped steel strand for fatigue testing.

[0013] Preferably, the connecting mechanism includes a force sensor, an adjustment component, and a tensioning component; the force sensor is disposed on the bottom surface of the concave seat near the base plate among the two concave seats, and the force sensor is provided with a wire that can be electrically connected to an external data display device, and the bottom surface of the force sensor is fixed to the support plate; the adjustment component is disposed on the bottom surface of the support plate and connected to the base plate, and the adjustment component can adjust the angle of the concave seat connected to the force sensor; the tensioning component is disposed between the support plate and the adjustment component, and the tensioning component can abut against the support plate and the adjustment component.

[0014] By adopting the above technical solution, the adjustment component can be used to adjust the angle of the concave seat, so that the arrangement direction of the steel strand and the direction of force application are kept on the same straight line. The tensioning component can be used to eliminate the assembly gap during the assembly process of the parts, so as to ensure the accuracy of the test results. During the fatigue test, the second hydraulic cylinder applies force to the clamped steel strand by driving the second piston rod. During this process, the force sensor can detect the magnitude of the force and transmit the detection result to the external data display device to display the force data, so that the staff can intuitively observe the changes in the force data.

[0015] Preferably, the adjusting assembly includes a cylindrical base, a long bolt, and a pair of sleeve blocks; the cylindrical base is mounted on the top surface of the base plate, and a pair of grooves are provided on the cylindrical base; the pair of grooves are respectively located on the top and bottom surfaces of the cylindrical base; a through hole connecting the two grooves is vertically provided inside the cylindrical base; the long bolt is disposed inside the cylindrical base, passing through the through hole and the pair of grooves, and the top end of the long bolt is threaded into the support plate; the pair of sleeve blocks are sleeved on the outside of the long bolt, and the two sleeve blocks are respectively located in the two grooves; two sets of fixing members are provided inside the cylindrical base, respectively located in the two grooves; the two sets of fixing members can fix the two sleeve blocks respectively; the tensioning assembly is sleeved on the outside of the long bolt, and the tensioning assembly is located between the cylindrical base and the support plate.

[0016] By adopting the above technical solution, when adjusting the angle of the concave seat, the fixing component loosens the fixing effect on the sleeve block, and the long bolt can rotate and move in the through hole. By adjusting the position of the concave seat, the steel strand clamped between the two concave seats is kept vertical and in the same straight line as the pulling direction of the second hydraulic cylinder. Then, the sleeve block is fixed by the fixing component, which causes the long bolt to be locked under the action of friction, thereby achieving the fixation of the position angle of the concave seat, so as to ensure the accuracy of the test results.

[0017] Preferably, the inner wall of the groove is provided with a plurality of threaded holes evenly distributed along the inner circumference of the groove; the fixing member includes a plurality of fixing bolts; the plurality of fixing bolts respectively pass through the plurality of threaded holes, the fixing bolts are threadedly engaged with the inner wall of the threaded holes, and the small head of the fixing bolt can be pressed against the outer wall of the sleeve block.

[0018] By adopting the above technical solution, after adjusting the position and angle of the concave seat, the fixing bolt can be rotated and pressed against the outer wall of the sleeve block. The sleeve block is fixed by the friction between the collar and the end of the fixing bolt, thereby fixing the position of the long bolt so as to fix the position of the concave seat after the angle is aligned.

[0019] Preferably, the tensioning assembly includes a pair of collars; the pair of collars are sleeved on the outside of the long bolt, the two collars are located at the top of the cylindrical seat and the bottom of the support plate, the two collars are symmetrically arranged and the end faces of the two collars that are close to each other are inclined progressive surfaces that cooperate with each other.

[0020] By adopting the above technical solution, when the testing machine is assembled and tested, it is necessary to rotate two sets of rings. Through the cooperation of the progressive end faces of the two sets of rings, the end faces of the two sets of rings that are far apart from each other are pressed against the bottom surface of the support plate and the top surface of the cylindrical seat, respectively, eliminating the assembly gap during the component assembly process. This allows the testing machine to apply continuous force during the test and prevents jamming when crossing the zero point.

[0021] Preferably, both collars have insertion holes on their outer walls.

[0022] By adopting the above technical solution, when rotating the two rings, a matching insert rod can be inserted into the insertion hole so that the worker can push the insert rod to drive the ring to rotate, making it convenient for the worker to apply force.

[0023] Preferably, a set of countersunk holes are vertically provided on the cylindrical base; each of the set of countersunk holes is provided with a fastening bolt for fixing the cylindrical base to the base plate.

[0024] By adopting the above technical solution, the setting of fastening bolts can facilitate the installation and disassembly of the column base on the base plate, and facilitate the assembly of adjustment components.

[0025] In summary, this application has the following beneficial effects: 1. Place the steel strand between the two concave seats, activate the two first hydraulic cylinders on the concave seats to make the two connecting plates inside the concave seats move towards each other and use the jaw plates to clamp the steel strand. When the size of the steel strand changes, the jaw plates can be replaced to match, avoiding the trouble of disassembling and replacing the entire jaws, improving the efficiency of testing and reducing maintenance costs. The power mechanism is used to apply force to the steel strand during the test. 2. Loosening the fixing bolts on the sleeve block allows the long bolt to rotate and move within the through hole of the cylindrical seat, adjusting the position and angle of the concave seat connected to the force sensor. This ensures that the clamped steel strand is aligned with the direction of the applied force. Then, the fixing bolts are rotated to fix the sleeve block, thus fixing the position and angle of the concave seat and ensuring the accuracy of the test results. 3. When the testing machine is assembled and the test is carried out, rotate the two rings. Through the cooperation of the progressive end faces of the two rings, the end faces of the two rings that are far apart from each other are pressed against the bottom surface of the support plate and the top surface of the cylindrical seat, respectively. This eliminates the assembly gaps in the component assembly process, so that the testing machine can continuously apply force during the test and will not jam when crossing the zero point. Attached Figure Description

[0026] Figure 1 This is a structural schematic diagram of a steel strand fatigue testing machine with interchangeable jaws; Figure 2This is a schematic diagram of the internal structure of the concave seat in this application; Figure 3 This is an exploded view of the connecting plate and jaw plate in this application; Figure 4 This is a schematic diagram of the mating structure of the concave seat and the connecting mechanism in this application; Figure 5 This is a cross-sectional structural diagram of the adjustment component in this application; Figure 6 This is an exploded view of the tensioning component in this application.

[0027] Explanation of reference numerals in the attached drawings: 1. Frame; 11. Base plate; 12. Top plate; 13. Column; 2. Concave seat; 21. First hydraulic cylinder; 22. First piston rod; 23. Connecting plate; 231. Slot; 24. Jaw plate; 241. Limiting slot; 242. Block; 3. Power mechanism; 31. Second hydraulic cylinder; 32. Second piston rod; 4. Connecting mechanism; 41. Force sensor; 411. Wire; 412. Support plate; 42. Adjustment assembly; 421. Columnar seat; 422. Long bolt; 423. Sleeve block; 424. Groove; 425. Through hole; 426. Threaded hole; 427. Fixing bolt; 428. Countersunk hole; 429. Fastening bolt; 43. Tensioning assembly; 431. Collar; 432. Insertion hole. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to the accompanying drawings. Identical components are indicated by the same reference numerals. It should be noted that the terms "front," "rear," "left," "right," "upper," "lower," "bottom," and "top" used in the following description refer to directions in the drawings, while the terms "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively.

[0029] This invention discloses a steel strand fatigue testing machine with interchangeable jaws, such as... Figure 1 , Figure 2 and Figure 3 As shown, the device includes a frame 1 and a pair of concave seats 2. The frame 1 includes a base plate 11 and a top plate 12. Four vertically arranged columns 13 are detachably installed on the top surface of the base plate 11. The top plate 12 is horizontally installed on the top of the four columns 13. The top plate 12 and the four columns 13 can be detachably installed and connected. The pair of concave seats 2 are positioned opposite each other between the base plate 11 and the top plate 12. A first hydraulic cylinder 21 is horizontally installed on the two outer walls of each concave seat 2 that are far apart from each other. A first piston rod 22 extending into the concave seat 2 is coaxially fixed to the output end of the first hydraulic cylinder 21. A connecting plate 23 is fixed to the end of the first piston rod 22. A detachable jaw plate 24 is inserted and installed at the end of the connecting plate 23 away from the first piston rod 22. A limiting groove 241 that can cooperate with the outer wall of the end of the steel strand is vertically opened on the end face of the jaw plate 24 away from the connecting plate 23. The top plate 12 is provided with a power mechanism 3 connected to the top surface of the top concave seat 2 of the two concave seats 2. The power mechanism 3 can drive the concave seat 2 connected to it to move up and down. The top surface of the bottom plate 11 is provided with a connecting mechanism 4 connected to the bottom surface of the bottom concave seat 2 of the two concave seats 2.

[0030] The steel strand is placed between the two concave seats 2. The two first hydraulic cylinders on the concave seats 2 are activated, causing the two connecting plates 23 inside the concave seats 2 to move towards each other and clamp the steel strand using the jaw plates 24. The limiting groove 241 on the end face of the jaw plates 24 can cooperate with the outer wall of the end face of the steel strand to limit the steel strand. When the size of the steel strand changes, the jaw plates 24 that are suitable can be replaced, avoiding the trouble of disassembling and replacing the entire jaw, improving the efficiency of testing and reducing maintenance costs. The power mechanism 3 is used to apply force to the steel strand during the test, and the connecting mechanism 4 is used to support the concave seat 2 located at the bottom.

[0031] like Figure 1 and Figure 2 As shown, the power mechanism 3 includes a second hydraulic cylinder 31, which is vertically mounted on the top surface of the top plate 12. The output end of the second hydraulic cylinder 31 is coaxially fixed to a second piston rod 32 that passes through the top plate 12. The bottom end of the second piston rod 32 is fixed to the top surface of the concave seat 2 located at the top of the two concave seats 2.

[0032] The second hydraulic cylinder 31 can drive the second piston rod 32 to move and change the distance between the two concave seats 2 so as to apply force to the clamped steel strand for fatigue testing.

[0033] like Figure 2 and Figure 3 As shown, the connecting plate 23 has a horizontal slot 231 on the end face near the jaw plate 24, and a locking block 242 is horizontally fixed on the end face of the jaw plate 24 near the connecting plate 23; the locking block 242 can be horizontally inserted into the slot 231, and the locking block 242 slides with the inner wall of the slot 231.

[0034] The assembly structure of the jaw plate 24 and the connecting plate 23 is set to be interlocked, which can facilitate the installation and removal of the jaw plate 24 on the connecting plate 23, so that the staff can replace the corresponding jaw plate 24 according to the steel strand to be tested.

[0035] like Figure 1 and Figure 4As shown, the connecting mechanism 4 includes a force sensor 41, an adjusting component 42, and a tensioning component 43. The force sensor 41 is disposed on the bottom surface of the concave seat 2 near the base plate 11 among the two concave seats 2. A wire 411 is disposed on the force sensor 41, which can realize the electrical connection between the force sensor 41 and the external data display device. A support plate 412 is fixedly connected to the bottom surface of the force sensor 41. The adjusting component 42 is disposed on the top surface of the base at the bottom of the support plate 412 and connected to the support plate 412. The adjusting component 42 can adjust the angle position of the concave seat 2 connected to the force sensor 41. The tensioning component 43 is disposed between the support plate 412 and the adjusting component 42. The tensioning component 43 can press against the support plate 412 and the adjusting component 42 to eliminate assembly gaps.

[0036] The adjustment component 42 can be used to adjust the angle of the concave seat 2, while the tensioning component 43 can be used to eliminate the assembly gap during the assembly process of the parts and ensure the accuracy of the test results. The force sensor 41 can detect the magnitude of the force and transmit the detection result to an external data display device to display the force data so that the staff can intuitively observe the changes in the force data.

[0037] like Figure 4 and Figure 5 As shown, the adjusting assembly 42 includes a cylindrical seat 421, a long bolt 422, and a pair of sleeve blocks 423. The cylindrical seat 421 is detachably mounted on the top surface of the base plate 11. A pair of grooves 424 are provided on the cylindrical seat 421, located on the top and bottom surfaces of the cylindrical seat 421 respectively. A through hole 425 is also vertically provided inside the cylindrical seat 421, connecting the two grooves 424. The long bolt 422 is located inside the cylindrical seat 421, passing through the through hole 425 and the pair of grooves 424. The top end of the long bolt 422 is threaded into the support plate 412. The pair of sleeve blocks 423 are located in the two grooves 424 respectively and are both sleeved outside the long bolt 422. Two sets of fixing members are provided inside the cylindrical seat 421, located in the two grooves 424 respectively, for fixing the two sleeve blocks 423. The tensioning assembly 43 is located between the cylindrical seat 421 and the support plate 412 and is sleeved outside the long bolt 422.

[0038] When adjusting the angle of the concave seat 2, first loosen the fixing of the sleeve block 423, so that the long bolt 422 can rotate and move in the through hole 425. Then adjust the position of the concave seat 2 so that the steel strand clamped between the two concave seats 2 remains vertical and is in the same straight line as the pulling direction of the second hydraulic cylinder 31. Then use the fixing to fix the sleeve block 423, so that the long bolt 422 is locked under the action of friction, thereby fixing the position of the concave seat 2 and ensuring the accuracy of the test results.

[0039] like Figure 4 and Figure 5As shown, the inner wall of the groove 424 is provided with a plurality of threaded holes 426 evenly distributed along the inner circumference of the groove 424; the fastener includes a plurality of fixing bolts 427; the plurality of fixing bolts 427 are respectively threaded to the inner wall of the plurality of threaded holes 426, and the small head of the fixing bolt 427 can be pressed against the outer wall of the sleeve block 423.

[0040] Rotating the fixing bolt 427 can lock and unlock the sleeve block 423, so as to adjust the angle position of the concave seat 2 and fix the position after adjustment.

[0041] like Figure 5 and Figure 6 As shown, the tensioning assembly 43 includes a pair of collars 431 symmetrically arranged around the long bolt 422. The two collars 431 are located between the cylindrical seat 421 and the support plate 412. The end faces of the two collars 431 that are far apart from each other contact the cylindrical seat 421 and the support plate 412 respectively. The end faces of the two collars 431 that are close to each other are inclined progressive surfaces that cooperate with each other. Insertion holes 432 are provided on the outer walls of the two collars 431.

[0042] During the debugging of the testing machine, the two rings 431 sleeved outside the long bolt 422 are rotated. With the cooperation of the asymptotic end faces of the two rings 431, the two rings 431 respectively abut against the bottom surface of the support plate 412 and the top surface of the cylindrical seat 421, eliminating the assembly gap between the parts so that the testing machine can continuously apply force during the test and will not cause jamming when crossing the zero point, ensuring the accuracy of the test data. The setting of the insertion hole 432 facilitates the insertion of the rod to rotate the rings 431.

[0043] like Figure 1 and Figure 4 As shown, a set of countersunk holes 428 are vertically opened on the top surface of the bottom wall of the column base 421 and are evenly distributed around the circumference of the column base 421. Each countersunk hole 428 is provided with a fastening bolt 429 that can pass through the countersunk hole 428 and be threaded into the base plate 11.

[0044] The fastening bolt 429 allows for easy installation and removal of the column base 421 on the base plate 11, facilitating the assembly of the long bolt 422.

[0045] Working principle: During the fatigue test of the steel strand, the steel strand is placed between two concave seats 2. The two first hydraulic cylinders on the concave seats 2 are activated, causing the two connecting plates 23 inside the concave seats 2 to move towards each other and clamp the steel strand using jaw plates 24. This causes the grooves 424 on the end face of the jaw plates 24 to contact and engage with the outer wall of the end of the steel strand, limiting the movement of the steel strand. Then, the second hydraulic cylinder 31 is activated, driving the second piston rod 32 to move, causing the distance between the two concave seats 2 to change and apply force to the steel strand for fatigue testing. During the fatigue test, the force sensor 41 can detect the magnitude of the force and transmit the detection result to an external data display device to display the force data, so that the staff can intuitively observe the changes in the force data. When the size of the steel strand changes, the jaw plates 24 that are compatible can be replaced, thus avoiding the trouble of disassembling and replacing the entire jaws, improving the efficiency of testing and reducing maintenance costs. To ensure the accuracy of the test results, the testing machine needs to be adjusted before the test. By rotating the fixing bolt 427 to loosen the fastening effect on the sleeve block 423, the long bolt 422 can rotate and move within the through hole 425 of the cylindrical seat 421. At this time, adjust the position and angle of the concave seat 2 connected to the force sensor 41 so that the clamped steel strand is in the same straight line as the direction of the applied force. Then rotate the fixing bolt 427 to fix the sleeve block 423, thereby fixing the position and angle of the concave seat 2. Before the testing machine starts working, by rotating the two rings 431 sleeved on the outside of the long bolt 422, the asymptotic end faces of the two rings 431 cooperate with each other, so that the opposite end faces of the two rings 431 press against the bottom surface of the support plate 412 and the top surface of the cylindrical seat 421 respectively, thereby eliminating the assembly gap between the parts, so that the testing machine can continuously apply force during the test, and there will be no jamming when crossing the zero point, ensuring the accuracy of the test data.

[0046] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A fatigue testing machine for steel strands with interchangeable jaws, characterized in that: The assembly includes a frame (1) and a pair of concave seats (2); the pair of concave seats (2) are arranged opposite to each other inside the frame (1), and each concave seat (2) has a first hydraulic cylinder (21) horizontally mounted on its two mutually spaced outer walls; the output end of the first hydraulic cylinder (21) is provided with a first piston rod (22) extending into the concave seat (2); the end of the first piston rod (22) is provided with a connecting plate (23); the end of the connecting plate (23) away from the first piston rod (22) can be... The jaw plate (24) is disassembled and installed; the jaw plate (24) has a limiting groove (241) on the end face away from the connecting plate (23) that can cooperate with the outer wall of the steel strand; the end faces of the pair of concave seats (2) that are far apart from each other are respectively provided with a power mechanism (3) and a connecting mechanism (4); the power mechanism (3) is connected to the top wall of the frame (1), and the power mechanism (3) can drive the concave seat (2) connected to it to move up and down; the connecting mechanism (4) is connected to the inner bottom wall of the frame (1).

2. The steel strand fatigue testing machine with interchangeable jaws according to claim 1, characterized in that: The connecting plate (23) has a slot (231) on the end face near the jaw plate (24); the jaw plate (24) has a block (242) fixedly connected to the end face near the connecting plate (23) that can be inserted into the slot (231); the block (242) slides in cooperation with the inner wall of the slot (231).

3. The steel strand fatigue testing machine with interchangeable jaws according to claim 1, characterized in that: The frame (1) includes a base plate (11) and a top plate (12); a set of columns (13) are vertically and detachably installed on the top surface of the base plate (11); the top plate (12) is disposed on the top of the set of columns (13) and is detachably connected to the set of columns (13); a pair of concave seats (2) are disposed opposite each other between the base plate (11) and the top plate (12); the power mechanism (3) is connected to the top plate (12); the connecting mechanism (4) is connected to the base plate (11).

4. The steel strand fatigue testing machine with interchangeable jaws according to claim 3, characterized in that: The power mechanism (3) includes a second hydraulic cylinder (31); the second hydraulic cylinder (31) is vertically mounted on the top surface of the top plate (12), and the vertical end of the second hydraulic cylinder (31) is provided with a second piston rod (32) that penetrates the top plate (12); the bottom end of the second piston rod (32) is connected to the top surface of the top concave seat (2) of a pair of concave seats (2).

5. A steel strand fatigue testing machine with interchangeable jaws according to claim 3, characterized in that: The connecting mechanism (4) includes a force sensor (41), an adjustment component (42), and a tensioning component (43). The force sensor (41) is disposed on the bottom surface of the concave seat (2) near the base plate (11) of the two concave seats (2). The force sensor (41) is provided with a wire (411) that can be electrically connected to an external data display device. The bottom surface of the force sensor (41) is fixed to the support plate (412). The adjustment component (42) is disposed on the bottom surface of the support plate (412) and connected to the base plate (11). The adjustment component (42) can adjust the angle of the concave seat (2) connected to the force sensor (41). The tensioning component (43) is disposed between the support plate (412) and the adjustment component (42). The tensioning component (43) can abut against the support plate (412) and the adjustment component (42).

6. A steel strand fatigue testing machine with interchangeable jaws according to claim 5, characterized in that: The adjusting assembly (42) includes a cylindrical seat (421), a long bolt (422), and a pair of sleeve blocks (423). The cylindrical seat (421) is mounted on the top surface of the base plate (11), and a pair of grooves (424) are provided on the cylindrical seat (421). The pair of grooves (424) are located on the top and bottom surfaces of the cylindrical seat (421), respectively. A through hole (425) connecting the two grooves (424) is vertically provided inside the cylindrical seat (421). The long bolt (422) is located inside the cylindrical seat (421), and the long bolt (422) passes through the through hole (425). A pair of grooves (424) are provided, and the top of the long bolt (422) is threadedly connected to the support plate 412; a pair of sleeves (423) are sleeved on the outside of the long bolt (422), and the two sleeves (423) are respectively located in the two grooves (424); the cylindrical seat (421) is provided with two sets of fixing members respectively located in the two grooves (424); the two sets of fixing members can fix the two sleeves (423) respectively; the tensioning component (43) is sleeved on the outside of the long bolt (422), and the tensioning component (43) is located between the cylindrical seat (421) and the support plate 412.

7. A steel strand fatigue testing machine with interchangeable jaws according to claim 6, characterized in that: The inner wall of the groove (424) is provided with a plurality of threaded holes (426) evenly distributed along the inner circumference of the groove (424); the fastener includes a plurality of fixing bolts (427); the plurality of fixing bolts (427) respectively pass through the plurality of threaded holes (426), the fixing bolts (427) are threadedly engaged with the inner wall of the threaded holes (426), and the small head of the fixing bolts (427) can be pressed against the outer wall of the sleeve block (423).

8. A steel strand fatigue testing machine with interchangeable jaws according to claim 5, characterized in that: The tensioning assembly (43) includes a pair of collars (431); the pair of collars (431) are sleeved on the outside of the long bolt (422), the two collars (431) are located at the top of the column base (421) and the bottom of the support plate 412, the two collars (431) are symmetrically arranged and the end faces of the two collars (431) that are close to each other are inclined progressive surfaces that cooperate with each other.

9. A steel strand fatigue testing machine with interchangeable jaws according to claim 8, characterized in that: Both collars (431) have insertion holes (432) on their outer walls.

10. A steel strand fatigue testing machine with interchangeable jaws according to claim 6, characterized in that: The cylindrical base (421) is vertically provided with a set of countersunk holes (428); each of the set of countersunk holes (428) is provided with a fastening bolt (429) that can fix the cylindrical base (421) on the base plate (11).

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