Testing machine and experimental method for detecting bending fatigue of nylon pipe

Abstract

The invention discloses a testing machine and method for detecting bending fatigue of a nylon pipe, and relates to the technical field of material performance testing. Comprising a rack, a first plate body and a second plate body. The first plate body is provided with a first toothed bar driven by the driving piece and a first gear meshed with the first toothed bar; the upper end of the first gear is rotationally connected with a sleeve used for clamping a pipe. The upper end of the shaft rod is hinged to the sleeve, and the lower end of the shaft rod penetrates through the first plate body. And the second plate body is provided with a driving rod for driving the shaft rod to vertically slide. Through coordinated control of transverse driving of the first gear rod and vertical driving of the shaft rod, the pipe can be bent up and down while swinging along with the first gear, so that full-circumferential and multi-angle fatigue loading and evaluation of the pipe are completed, and the overall bending fatigue performance of the pipe is comprehensively reflected.

Description

Technical Field

[0001] This application relates to the field of material performance testing technology, and in particular to a testing machine and experimental method for detecting the bending fatigue of nylon pipes. Background Technology

[0002] Bending fatigue is a key indicator for evaluating the service reliability of engineering materials, especially nylon pipes. Bending fatigue testing determines the lifespan of materials under cyclic bending loads, which is crucial for safety in various transmission applications.

[0003] Existing pipe bending fatigue testing machines typically apply reciprocating bending loads to pipe specimens via actuators, causing the specimens to bend repeatedly in a single plane. A system of multiple electronic sensors (such as displacement and force sensors) is then used to determine if the specimen has fractured. Once a fracture signal is detected, the control system instructs the actuators to stop.

[0004] However, under complex actual working conditions, pipes may be subjected to alternating stresses from different or combined directions, and anisotropy or surface defects caused by the material's microstructure and forming process may also be non-uniformly distributed along the circumference. Existing single-direction reciprocating bending testing methods are insufficient to comprehensively assess the fatigue performance of the pipe in all directions along its entire circumference, resulting in limited test results that cannot fully and accurately reflect the overall bending fatigue strength and life of the pipe. Summary of the Invention

[0005] In order to comprehensively evaluate the fatigue of the entire circumference of the pipe, this application provides a testing machine and test method for detecting the bending fatigue of nylon pipes.

[0006] Firstly, this application provides a testing machine for detecting the bending fatigue of nylon pipes, which adopts the following technical solution: A testing machine for detecting the bending fatigue of nylon pipes includes a frame; a first plate body disposed on the frame, the first plate body having a first guide post, a first gear slidably passing through the first guide post, and a driving member for driving the first gear to slide laterally; a first gear rotatably disposed on the first plate body and meshing with the first gear, a sleeve for connecting the pipe being rotatably disposed on the upper end face of the first gear, the rotation axis of the sleeve extending horizontally, a shaft slidably disposed on the axis of the first gear, one end of the shaft above the first gear being hinged to the end of the sleeve away from the pipe, the end of the sleeve hinged to the shaft having a hinge groove, the hinge groove allowing the shaft to slide vertically to drive the sleeve to rotate, and the end of the shaft below the first gear slidably passing through the first plate body; and a second plate body disposed on the frame and located below the first plate body, the second plate body having a driving rod for driving the shaft to slide.

[0007] By adopting the above technical solution, the driving component drives the first rack to slide laterally, thereby driving the first gear to rotate. When the first gear rotates, its eccentrically positioned sleeve rotates synchronously, thereby driving the tubular sample clamped on the sleeve to rotate circumferentially around the axis of the first gear. At the same time, the driving rod on the second plate can drive the shaft to slide vertically, and the shaft drives the sleeve to pitch and swing around its horizontal axis through the hinge groove. By coordinating and controlling the lateral drive of the first rack and the vertical drive of the driving rod, the tubular sample can be reciprocated in different directions while rotating around the axis. This integrated motion realizes full-circumferential, multi-angle bending fatigue loading of the tubular sample, overcoming the limitations of existing single-plane bending, and can more comprehensively simulate complex stress conditions, realizing a comprehensive evaluation of the fatigue performance in all directions of the entire circumference of the tubular body, thus fully and realistically reflecting the overall bending fatigue strength and life of the tubular material.

[0008] Optionally, a support rod is provided on the upper end face of the first gear. The support rod is eccentrically disposed on the first gear. The end of the support rod away from the first gear is hinged to the sleeve. The hinge point between the support rod and the sleeve is disposed on the sleeve away from the shaft.

[0009] By adopting the above technical solution, the eccentric setting of the support rod causes the sleeve to not only revolve when the first gear rotates, but also generate an additional lever effect through the offset hinge point between the support rod and the sleeve. This effectively transforms the rotational motion of the first gear into the complex spatial oscillation of the sleeve. This structure enhances the diversity and controllability of the bending loading direction, enabling more precise and multi-dimensional application of bending stress to the tubular sample. This helps to more accurately detect and evaluate the differences in bending fatigue performance at different locations on the circumference of the tubular material.

[0010] Optionally, a second gear is rotatably mounted on the second plate. The drive rod has a thread on its surface and is threadedly connected to the second gear. The second gear is used to drive the drive rod to move up and down in the vertical direction. The drive rod is rotatably connected to the lower end of the shaft. The second gear is coaxial with the first gear. A limiting rod is provided on the second plate to restrict the rotation of the drive rod. The limiting rod passes through the upper end of the drive rod. The drive rod has a limiting groove that slides relative to the limiting rod.

[0011] By adopting the above technical solution, the rotation of the second gear is precisely converted into the linear lifting motion of the drive rod through the threaded pair. The cooperation between the limiting rod and the limiting groove strictly restricts the rotational freedom of the drive rod, ensuring that it only performs vertical movement. This achieves precise and stable control of the vertical sliding stroke of the shaft, thereby enabling precise setting and adjustment of the bending swing amplitude (deflection) of the sleeve (i.e., the tubular sample).

[0012] Optionally, the second plate is provided with a second guide post and a second toothed rod that slides through the second guide post. The sliding direction of the second toothed rod is parallel to the sliding direction of the first toothed rod, and the second toothed rod meshes with the second gear.

[0013] By adopting the above technical solution, the lateral sliding of the second rack can directly drive the rotation of the second gear, which in turn controls the lifting and lowering of the shaft via the drive rod. This structure also converts the drive on the second plate (used to control the bending amplitude) into a lateral linear input, making the overall control logic of the testing machine unified and coordinated. By synchronously controlling the sliding of the first and second racks, precise programming and control of the composite motion mode of circumferential rotation and multi-directional bending of the pipe can be achieved, providing a reliable experimental method for simulating complex alternating stress paths and studying the fatigue behavior of materials under multiaxial stress states.

[0014] Optionally, connecting rods are connected to both ends of the first toothed rod. The end of the connecting rod away from the first toothed rod slides through the first plate and connects to both ends of the second toothed rod. A groove is provided on the first plate for the connecting rod to slide.

[0015] By adopting the above technical solution, the connecting rod mechanically links the first and second racks. When the driving component drives the first rack to slide laterally, the connecting rod synchronously drives the second rack to slide. This ensures a fixed mechanical linkage between the circumferential rotational motion and the bending amplitude adjustment motion of the tubular sample, enabling a specific and repeatable composite loading path. This mechanical synchronization method is structurally reliable, eliminates the need for complex electronic synchronization control, reduces complexity, and ensures the stability and consistency of motion coordination during long-term fatigue testing.

[0016] Optionally, the connecting rod includes a first rod body and a second rod body. The first rod body is engaged with both ends of the first toothed rod, and the second rod body is connected to both ends of the second toothed rod. The first rod body is slidably sleeved on the second rod body. A spring is provided inside the first rod body, with one end of the spring disposed inside the first rod body and the other end disposed on the second rod body. The spring is used to move the first rod body to engage with the first toothed rod.

[0017] By adopting the above technical solution, the spring provides an upward holding force for the first rod, keeping the spring engaged with the first toothed rod under normal conditions, thereby transmitting motion. This allows for relative sliding between the first and second rods, compressing the spring and releasing the engagement between the first rod and the first toothed rod. This, in turn, releases the synchronous sliding of the first and second toothed rods. At this point, the sliding of the first toothed rod drives the first gear to rotate, the second toothed rod stops sliding, the second gear stops rotating, and the shaft stops sliding up and down. Consequently, the sleeve only rotates back and forth horizontally with the first gear, facilitating switching between horizontal and vertical rotation of the sleeve.

[0018] Optionally, the spring is in a compressed state within the first rod body due to the weight of the first rod body, and if the spring continues to compress, the first rod body disengages from the first toothed rod.

[0019] By adopting the above technical solution, the first rod can be slid downwards to compress the spring, disengage the first rod from the first toothed rod, and release the drive for vertical rotation of the sleeve.

[0020] Optionally, the bottom of both ends of the first toothed rod is provided with a slot, and the top of the first rod is provided with a groove that matches the slot. The first rod slides vertically through the slot and the groove and engages with the first toothed rod.

[0021] By adopting the above technical solution, the combination of the slot and the groove forms a simple, robust, and rapidly disengaging mechanical locking structure. During normal testing, this locking mechanism effectively transmits lateral driving force. When disengagement is required, the first rod only needs to slide vertically down a short distance to completely detach, with a direct, rapid, and interference-free action.

[0022] Optionally, a buckle is rotatably connected to the outer wall of the first rod near one end of the second rod. The rotation axis of the buckle extends in the horizontal direction, and the buckle is used to engage with the bottom wall of the second plate after the first rod is disengaged from the first toothed rod.

[0023] By adopting the above technical solution, the snap-fit ​​design provides a self-locking state retention mechanism. When the first rod moves down and disengages from the first toothed rod, the snap-fit ​​rotates under the action of gravity or inertia and can engage with the bottom wall of the second plate, thereby locking the first rod in the descending position and preventing it from accidentally resetting under vibration or residual stress, thus enhancing the stability of the linkage release between the first and second toothed rods.

[0024] Secondly, this application provides an experimental method for detecting the bending fatigue of nylon tubing, applied to the testing machine for detecting the bending fatigue of nylon tubing described in the first aspect. The method includes: controlling a driving member to drive the first rack to slide back and forth on the first plate; rotating the first gear based on the sliding force of the first rack and driving the tubing on the sleeve to bend in the horizontal direction; controlling the driving rod to slide in the vertical direction and transmitting the power of the vertical sliding to the shaft, so that the shaft drives the tubing on the sleeve to bend in the vertical direction while rotating with the first gear.

[0025] Since an experimental method for detecting the bending fatigue of nylon pipes has the same technical effect as the testing machine for detecting the bending fatigue of nylon pipes provided in the first aspect above, the relevant description in the first aspect above can be referred to, and will not be repeated here.

[0026] In summary, this application includes at least one of the following beneficial technical effects: Through the cooperation of the driving component with the first gear, eccentric support rod and sleeve, as well as the linkage between the shaft and the driving rod, the composite motion of circumferential rotation and multi-directional bending of the tubular sample around its own axis is realized. This enables bending fatigue loading and testing of the tubular material in the full circumference and at multiple angles, overcoming the limitations of bending in a single direction. It more comprehensively characterizes the performance differences of the material caused by anisotropy or circumferential defects, and significantly improves the comprehensiveness and authenticity of bending fatigue testing. By incorporating a spring within the connecting rod and using a slot and groove design between the first toothed rod and the first rod body, the tube fatigue test can switch from bending in the horizontal direction and bending in the vertical direction to bending only in the horizontal direction. Through the cooperation of the second gear, the threaded drive rod, and the limit rod and limit groove, precise and stable control of the shaft lifting and the sleeve swing amplitude is achieved. This enables precise setting and adjustment of the bending strain amplitude applied to the pipe, providing key technical support for quantitative determination of the stress-life (SN) curve of the material and accurate analysis of fatigue performance. Attached Figure Description

[0027] Figure 1 A schematic diagram of the overall structure of a testing machine for detecting the bending fatigue of nylon pipes is provided for the embodiments of this application.

[0028] Figure 2 This is a structural schematic diagram provided for illustrating the first plate and the second plate in an embodiment of this application.

[0029] Figure 3 An exploded view of the connecting rod provided for an embodiment of this application.

[0030] Explanation of reference numerals in the attached drawings: 1. Frame; 11. Frame body; 12. Top plate; 2. First plate; 21. First guide post; 22. First gear; 221. Slot; 23. Drive component; 24. First gear; 241. Shaft; 242. Support rod; 25. Sleeve; 251. Hinge groove; 26. Slide groove; 3. Second plate; 31. Drive rod; 311. Limiting groove; 32. Second gear; 33. Limiting rod; 34. Second guide post; 35. Second gear; 36. Notch; 4. Connecting rod; 41. First rod body; 411. Groove; 412. Buckle; 2. Second rod body; 43. Spring. Detailed Implementation

[0031] This application discloses a testing machine for detecting the bending fatigue of nylon pipes. (Refer to...) Figure 1 and Figure 2 , Figure 1 This application provides a schematic diagram of the overall structure of a testing machine for detecting the bending fatigue of nylon pipes. Figure 2 The schematic diagram provided in this application illustrates the structure of the first plate and the second plate. A testing machine for detecting the bending fatigue of nylon pipes includes a frame 1, a first plate 2, and a second plate 3. The first plate 2 is mounted on the frame 1. The first plate 2 is provided with a first guide post 21, a first gear 22 that slides through the first guide post 21, and a driving member 23 that drives the first gear 22 to slide laterally. The first plate 2 is also rotatably mounted with a first gear 24 that meshes with the first gear 22. A sleeve 25 for connecting a pipe is rotatably mounted on the upper end face of the first gear 24. The rotation axis of the sleeve 25 extends horizontally. A shaft 241 is slidably mounted on the axis of the first gear 24. One end of the shaft 241 located above the first gear 24 is hinged to the end of the sleeve 25 away from the pipe. The end of the sleeve 25 that is hinged to the shaft 241 has a hinge groove 251. The hinge groove 251 allows the shaft 241 to slide vertically and drive the sleeve 25 to rotate. The end of the shaft 241 located below the first gear 24 slides through the first plate 2. The second plate 3 is mounted on the frame 1 and located below the first plate 2. The second plate 3 is provided with a drive rod 31 for sliding the drive shaft 241.

[0032] In this embodiment, the frame 1 includes a frame body 11 and a top plate 12. The first plate 2 and the second plate 3 are both located below the top plate 12 and are parallel to it. A pair of first guide posts 21 are located on the first plate 2, and the pair of first guide posts 21 are spaced apart along the sliding direction of the first gear 22. The end of the sleeve 25 away from the shaft 241 is used to connect to a nylon tube. The nylon tube on the sleeve 25 is bent in both the horizontal and vertical directions by the rotation of the first gear 24 and the up-and-down sliding of the shaft 241.

[0033] For example, the drive component 23 includes a motor fixed to the first plate 2, a crank coaxially connected to the motor shaft, and a rocker arm rotatably connected to the end of the crank away from the motor shaft. The motor is positioned near the end of the first rack 22, and the motor shaft extends in a direction perpendicular to the sliding direction of the first rack 22. The end of the rocker arm away from the crank is rotatably connected to the end of the first rack 22, so that the motor drives the crank to rotate, the crank drives the rocker arm to rotate, and the rocker arm's swing and rotation cause the first rack 22 to slide back and forth horizontally on the first plate 2. When the first rack 22 slides back and forth at the midpoint of its stroke, the sleeve 25 is exactly perpendicular to the first rack 22, and at this time, the nylon tubing on the sleeve 25 is in an unbent state.

[0034] In some embodiments, a support rod 242 is provided on the upper end surface of the first gear 24. The support rod 242 is eccentrically disposed on the first gear 24. The end of the support rod 242 away from the first gear 24 is hinged to the sleeve 25. The hinge point between the support rod 242 and the sleeve 25 is disposed on the sleeve 25 away from the shaft 241.

[0035] In this embodiment, the support rod 242 is hinged to the bottom wall of the sleeve 25, so that the shaft rod 241 can drive one end of the sleeve 25 to rise and fall based on the fulcrum of the sleeve 25, thereby causing the nylon tube on the sleeve 25 to bend up and down.

[0036] In some embodiments, a second gear 32 is rotatably mounted on the second plate 3, and the surface of the drive rod 31 is threaded and threadedly connected to the second gear 32. The second gear 32 is used to drive the drive rod 31 to move up and down in the vertical direction. The drive rod 31 is rotatably connected to the lower end of the shaft 241. The second gear 32 is coaxial with the first gear 24. A limiting rod 33 is provided on the second plate 3 to limit the rotation of the drive rod 31. The limiting rod 33 passes through the upper end of the drive rod 31, and the drive rod 31 has a limiting groove 311 that slides relative to the limiting rod 33.

[0037] In this embodiment, the rotation axis of the second gear 32 coincides with the rotation axis of the first gear 24, and the size of the first gear 24 is the same as that of the second gear 32. The limiting rod 33 passes laterally through both ends of the limiting groove 311 and is fixedly connected to the second plate 3. The shaft 241 passes downward through the end of the first plate 2 located above the second plate 3 and is rotatably connected to the drive rod 31. The limiting groove 311 is located on the drive rod 31 near the end of the shaft 241, so that the limiting rod 33 can limit the movement of the drive rod 31. While allowing the limiting rod 33 and the drive rod 31 to slide relative to each other, the drive rod 31, through a threaded connection, can only move vertically up and down under the rotation of the second gear 32. Specifically, the forward and reverse rotation of the second gear 32 enables the drive rod 31 to move vertically up and down, thereby driving the shaft 241 to move vertically up and down.

[0038] It should be noted that the limiting rod 33 is located in the limiting groove 311. The upper and lower groove walls of the limiting groove 311 limit the sliding of the limiting rod 33 relative to the driving rod 31, so as to limit the distance of the driving rod 31 to rise and fall by the length of the limiting groove 311 in the vertical direction, thereby limiting the distance of the shaft 241 to rise and fall.

[0039] In some embodiments, the second plate 3 is provided with a second guide post 34 and a second toothed rod 35 that slides through the second guide post 34. The sliding direction of the second toothed rod 35 is parallel to the sliding direction of the first toothed rod 22, and the second toothed rod 35 meshes with the second gear 32.

[0040] In this embodiment, the second guide post 34 and the first guide post 21 are vertically aligned, meaning there is a pair of second guide posts 34 on the second plate 3. The second rack 35 and the first rack 22 are also vertically aligned, and the first rack 22 and the second rack 35 have the same length, the same sliding direction, and the same tooth pattern. This ensures that the first rack 22 and the second rack 35 slide synchronously, thereby driving the first gear 24 and the second gear 32 to rotate synchronously. This allows the lifting speed of the drive rod 31 and the shaft 241 to be correlated with the swing speed of the sleeve 25, achieving synchronization.

[0041] In some embodiments, the two ends of the first toothed rod 22 are connected to connecting rods 4. The end of the connecting rod 4 away from the first toothed rod 22 slides through the first plate 2 and is connected to the two ends of the second toothed rod 35. The first plate 2 is provided with a groove 26 for the connecting rod 4 to slide.

[0042] In this embodiment, there are two connecting rods 4, located at both ends of the first toothed rod 22, which are used to connect the two ends of the first toothed rod 22 and the two ends of the second toothed rod 35. In this way, when the first toothed rod 22 slides, the first toothed rod 22 drives the connecting rod 4 to slide in the slide groove 26, and then the connecting rod 4 drives the second toothed rod 35 to slide synchronously with the first toothed rod 22.

[0043] In some embodiments, see Figure 2 and Figure 3 , Figure 3 The exploded view provided for the embodiment of this application shows the connecting rod 4. The connecting rod 4 includes a first rod body 41 and a second rod body 2. The first rod body 41 is engaged with both ends of the first toothed rod 22. The second rod body 2 is connected to both ends of the second toothed rod 35. The first rod body 41 is slidably sleeved on the second rod body 2. A spring 43 is provided inside the first rod body 41. One end of the spring 43 is disposed inside the first rod body 41, and the other end is disposed on the second rod body 2. The spring 43 is used to move the first rod body 41 to engage with the first toothed rod 22.

[0044] In this embodiment, the first rod 41 slides within the groove 26, and the second rod 2 slides vertically within the first rod 41. A spring 43, located inside the first rod 41, provides elastic force to engage the first rod 41 with the first toothed rod 22. The second rod 2 is fixedly connected to the second toothed rod 35.

[0045] In some embodiments, the spring 43 is in a compressed state within the first rod 41 due to the gravity of the first rod 41, and if the spring 43 continues to compress, the first rod 41 disengages from the first toothed rod 22.

[0046] In some embodiments, the bottom of both ends of the first toothed rod 22 is provided with a slot 221, and the top of the first rod body 41 is provided with a groove 411 that matches the slot 221. The first rod body 41 slides in the vertical direction through the slot 221 and the groove 411 to engage with the first toothed rod 22.

[0047] In this embodiment, the slot 221 is located at the top of the first rod 41, with the slot opening facing upwards. The groove 411 is located at the bottom of the first gear 22, with the groove opening facing downwards, so that after the first rod 41 slides in the vertical direction, the slot 221 and the groove 411 engage, thus allowing the first gear 22 to drive the first rod 41 to slide laterally along the length of the first gear 22. The first rod 41 can also slide in the vertical direction to disengage the slot 221 and the groove 411, releasing the connection between the first gear 22 and the first rod 41, and consequently releasing the connection between the first gear 22 and the second gear 35. At this point, the sliding of the first gear 22 does not drive the first gear 22, and since the drive rod 31 and the shaft 241 are rotatably connected, the shaft 241 is not affected by the rotation of the first gear 24.

[0048] In some embodiments, a buckle 412 is rotatably connected to the outer wall of the first rod 41 near the end of the second rod 2. The rotation axis of the buckle 412 extends in the horizontal direction. The buckle 412 is used to engage with the bottom wall of the second plate 3 after the first rod 41 is disengaged from the first toothed rod 22.

[0049] In this embodiment, the buckle 412 is bent into a U-shape, and the second plate 3 has a notch 36 for the buckle 412 to rotate into, so that after the buckle 412 pulls the first rod 41 to compress the spring 43 and slides down, the buckle 412 rotates downward into the notch 36 and engages with the bottom wall of the second plate 3, thereby locking the first rod 41 out of the state of the first toothed rod 22.

[0050] Based on the aforementioned testing machine for detecting the bending fatigue of nylon pipes, this application embodiment also provides a corresponding testing machine for detecting the bending fatigue of nylon pipes, the method comprising steps S100~S300: S100, the control drive unit drives the first rack to slide back and forth on the first plate.

[0051] In this embodiment, the output shaft of the drive component (e.g., a servo motor or linear module) is connected to the first rack, and its output reciprocating linear motion precisely controls the first rack to slide laterally (horizontally) along the first guide post. This sliding motion is the fundamental power input for subsequent circumferential rotation and compound bending of the tube. The sliding stroke and frequency of the first rack can be programmed according to test requirements (e.g., stress ratio, cycle frequency), providing a source for precise control of fatigue testing.

[0052] S200, Based on the sliding force of the first gear, the first gear rotates and drives the tubing on the sleeve to bend in the horizontal direction.

[0053] In this embodiment, the first rack meshes with the first gear, and its lateral sliding is directly converted into the alternating forward and reverse rotation of the first gear. The rotational motion of the first gear is transmitted to the sleeve hinged to it through a support rod eccentrically mounted on its upper end face. Since the hinge point between the support rod and the sleeve is off-center from the rotation axis of the sleeve, the rotation of the first gear does not simply drive the tube to rotate on its own axis, but rather, through the eccentric linkage mechanism, causes the tube sample clamped on the sleeve to generate a reciprocating rotation around its own axis while simultaneously undergoing a periodic yaw motion in the horizontal plane. This essentially constitutes a multi-angle bending load on the tube based on rotation in the horizontal projection plane, breaking through the limitations of traditional single-plane reciprocating bending and beginning to apply alternating stress to different circumferential directions of the tube.

[0054] S300: Control the drive rod to slide vertically and transmit the power of vertical sliding to the shaft, so that the shaft drives the tube on the sleeve to bend vertically while rotating with the first gear.

[0055] In this embodiment, this step is performed in conjunction with step S200 or independently according to a preset program. The rotation of the second gear (e.g., controlled by another driving component via a second rack) drives a threaded driving rod to perform precise vertical lifting and lowering. The upper end of the driving rod pushes or pulls the shaft via a rotatable connection, causing it to slide along its own axis (vertical direction) while revolving with the first gear. The vertical movement of the shaft is converted into the pitching oscillation of the sleeve around its horizontal hinge axis through the hinge groove structure between its top end and the sleeve. This oscillation causes the tubular sample to bend in the vertical plane. When the horizontal yaw motion generated by S200 and the vertical pitching motion generated by S300 are combined according to a specific timing and amplitude, i.e., the first rack and the driving rod coordinate their actions, a spatial three-dimensional composite bending motion trajectory acting on the tubular sample can be synthesized. This allows for the simulation and detection of fatigue performance under full circumferential and multiaxial stress states of the tubular material, comprehensively evaluating its bending fatigue strength and life in different directions.

[0056] 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 testing machine for detecting the bending fatigue of nylon pipes, characterized in that, The testing machine includes: frame; A first plate is mounted on the frame. The first plate has a first guide post, a first gear that slides through the first guide post, and a drive component that drives the first gear to slide laterally. A first gear that meshes with the first gear is also rotatably mounted on the first plate. A sleeve for connecting a pipe is rotatably mounted on the upper end face of the first gear. The rotation axis of the sleeve extends horizontally. A shaft is slidably mounted on the axis of the first gear. One end of the shaft above the first gear is hinged to the end of the sleeve away from the pipe. The end of the sleeve that is hinged to the shaft has a hinge groove. The hinge groove allows the shaft to slide vertically to drive the sleeve to rotate. The end of the shaft below the first gear slides through the first plate. The second plate is disposed on the frame and located below the first plate, and the second plate is provided with a drive rod for driving the shaft to slide.

2. The testing machine according to claim 1, characterized in that, A support rod is provided on the upper end face of the first gear. The support rod is eccentrically disposed on the first gear. The end of the support rod away from the first gear is hinged to the sleeve. The hinge point between the support rod and the sleeve is disposed on the sleeve away from the shaft.

3. The testing machine according to claim 1, characterized in that, A second gear is rotatably mounted on the second plate. The drive rod has a thread on its surface and is threadedly connected to the second gear. The second gear is used to drive the drive rod to move up and down in the vertical direction. The drive rod is rotatably connected to the lower end of the shaft. The second gear is coaxial with the first gear. A limiting rod is provided on the second plate to restrict the rotation of the drive rod. The limiting rod passes through the upper end of the drive rod. The drive rod has a limiting groove that slides relative to the limiting rod.

4. The testing machine according to claim 3, characterized in that, The second plate is provided with a second guide post and a second toothed rod that slides through the second guide post. The sliding direction of the second toothed rod is parallel to the sliding direction of the first toothed rod, and the second toothed rod meshes with the second gear.

5. The testing machine according to claim 4, characterized in that, The first toothed rod is connected to two connecting rods at both ends. The end of the connecting rod away from the first toothed rod slides through the first plate and connects to both ends of the second toothed rod. The first plate has a sliding groove for the connecting rod to slide.

6. The testing machine according to claim 5, characterized in that, The connecting rod includes a first rod body and a second rod body. The first rod body is engaged with both ends of the first toothed rod, and the second rod body is connected to both ends of the second toothed rod. The first rod body is slidably sleeved on the second rod body. A spring is provided inside the first rod body, with one end of the spring located inside the first rod body and the other end located on the second rod body. The spring is used to move the first rod body to engage with the first toothed rod.

7. The testing machine according to claim 6, characterized in that, The spring is in a compressed state within the first rod body due to the weight of the first rod body. If the spring continues to compress, the first rod body will disengage from the first toothed rod.

8. The testing machine according to claim 6, characterized in that, The bottom of both ends of the first toothed rod is provided with a slot, and the top of the first rod is provided with a groove that matches the slot. The first rod slides vertically through the slot and the groove and engages with the first toothed rod.

9. The testing machine according to claim 6, characterized in that, A buckle is rotatably connected to the outer wall of the first rod near the end of the second rod. The rotation axis of the buckle extends in the horizontal direction. The buckle is used to engage with the bottom wall of the second plate after the first rod is disengaged from the first toothed rod.

10. A test method for detecting the bending fatigue of nylon pipes, applied to the testing machine for detecting the bending fatigue of nylon pipes as described in claim 1, characterized in that, The method includes: The control drive unit drives the first rack to slide back and forth on the first plate; Based on the sliding force of the first toothed rod, the first gear rotates and drives the tubing on the sleeve to bend in the horizontal direction. The drive rod is controlled to slide vertically, and the power of the vertical sliding is transmitted to the shaft, so that the shaft drives the tube on the sleeve to bend vertically while rotating with the first gear.

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