A polyethylene pressure pipe and fitting connection pull resistance test device

Abstract

This invention belongs to the technical field of testing equipment and provides a tensile testing device for polyethylene pressure pipe and fitting connections. The device includes a testing equipment box, a constant temperature testing chamber fixedly mounted on the testing equipment box, and a tensile testing assembly. The tensile testing assembly includes a motor unit housed within the testing equipment box, a ball screw rotatably mounted within the constant temperature testing chamber and connected to the motor unit, a top lifting frame movably sleeved around the ball screw, and a bottom clamping frame fixedly mounted on the bottom wall of the constant temperature testing chamber. The top lifting frame is equipped with a top clamping unit for holding the sample pipe end, and the bottom clamping frame is equipped with a bottom clamping unit for holding the sample pipe end. The tensile testing device for polyethylene pressure pipe and fitting connections provided by this invention has a high degree of automation, improves the efficiency of the tensile testing, avoids testing errors caused by improper manual operation, and improves the accuracy of the test results.

Description

Technical Field

[0001] This invention belongs to the field of testing equipment technology, and specifically relates to a pull-out resistance test device for polyethylene pressure pipe and fitting connection. Background Technology

[0002] Currently, pull-out tests on polyethylene pressure pipes and fittings are generally conducted using a tensile tester to verify the pull-out resistance of the polyethylene pressure pipes and fittings when subjected to longitudinal tensile force by applying a constant longitudinal tensile force to the sample. However, the following problems exist in actual testing: First, according to the standard, a certain test temperature needs to be maintained during the test, but existing tensile testing devices cannot control the temperature. The test often needs to be conducted in a constant-temperature environment, which is time-consuming and labor-intensive, affecting test efficiency. Second, since tensile testing devices generally provide longitudinal tensile force by manually increasing the test load (such as weights), the applied tensile force has low accuracy and is cumbersome to operate, affecting the accuracy of the test results. Simultaneously, since the samples are manually clamped and fixed, it is impossible to guarantee the clamping is secure. Slippage during the test often occurs due to loose clamping, requiring retesting and affecting test efficiency. Furthermore, the standard requires testing three samples; only when all three samples remain intact is the test considered passed, and each sample often requires a continuous 1-hour test, resulting in a long testing time and low test efficiency.

[0003] Therefore, it is necessary to design a pull-out resistance test device for polyethylene pressure pipes and fittings that can at least solve some of the above problems and defects. Summary of the Invention

[0004] To address the above technical problems, this invention proposes a tensile testing device for polyethylene pressure pipes and fittings connections. This device features a high degree of automation, improving the efficiency of the tensile testing, avoiding test errors caused by improper manual operation, and enhancing the accuracy of the test results.

[0005] The technical solution of this invention is:

[0006] This invention proposes a pull-out resistance test device for polyethylene pressure pipes and fittings, including a test equipment box, a constant temperature test chamber fixedly installed on the test equipment box, and a pull-out test assembly;

[0007] The pull-out test assembly includes a motor unit housed in the test equipment box, a ball screw rotatably housed in the constant temperature test chamber and connected to the motor unit, a top lifting frame movably sleeved on the outer periphery of the ball screw, and a bottom clamping frame fixedly installed on the bottom wall of the constant temperature test chamber. The top lifting frame is provided with a top clamping unit for clamping the end of the sample tube, and the bottom clamping frame is provided with a bottom clamping unit for clamping the end of the sample tube.

[0008] Preferably, the top lifting frame includes a ball nut movably sleeved on the outer periphery of the ball screw, and three supports that are vertically and fixedly connected to the ball nut. The supports are evenly spaced along the circumferential direction, and the bottom clamping frame is provided with three supports, each corresponding to one of the three supports.

[0009] The bracket is provided with a longitudinally penetrating top limiting hole, the bottom clamp is provided with a longitudinally penetrating bottom limiting hole, and the top wall of the constant temperature test chamber is provided with a longitudinally penetrating placement hole. The placement hole, the top limiting hole, and the bottom limiting hole are arranged longitudinally opposite to each other.

[0010] Preferably, the top clamping unit is disposed on the upper end face of the bracket, and includes an upper outer clamping block, an upper inner clamping block and an upper push clamping cylinder connected to the upper inner clamping block arranged on both sides of the top limiting hole. The upper outer clamping block and the upper push clamping cylinder are fixedly connected to the bracket.

[0011] The bottom clamp unit is disposed on the lower end face of the bottom clamp frame, and includes a lower outer clamp block, a lower inner clamp block arranged on both sides of the bottom limiting hole, and a lower push clamp cylinder connected to the lower inner clamp block. The lower outer clamp block and the lower push clamp cylinder are fixedly connected to the bottom clamp frame.

[0012] Preferably, the pull-out test assembly further includes a first positioning unit fixedly disposed on the upper end face of the bracket and a second positioning unit fixedly disposed on the lower end face of the bracket, wherein the first positioning unit and the second positioning unit are arranged close to the upper outer clamping block and facing the top limiting hole.

[0013] Preferably, the test equipment box is equipped with a main control unit;

[0014] The motor unit is electrically connected to the main control unit, the upper push clamp cylinder and the lower push clamp cylinder are both electrically connected to the main control unit, and the first positioning unit and the second positioning unit are both electrically connected to the main control unit.

[0015] Preferably, the bottom wall of the constant temperature test chamber is provided with a contact sensing unit arranged opposite to the bottom limiting hole, and the contact sensing unit is electrically connected to the main control unit.

[0016] Preferably, the constant temperature test chamber is equipped with a temperature control component, which is electrically connected to the main control unit.

[0017] Preferably, the test equipment box is equipped with a touch screen and control buttons arranged at intervals from the constant temperature test chamber, and both the touch screen and the control buttons are electrically connected to the main control unit.

[0018] Preferably, the top of the constant temperature test chamber is provided with a sealing cover that is detachably connected thereto, the sealing cover being positioned directly above the placement hole, and the side wall of the constant temperature test chamber is provided with at least one viewing window.

[0019] Preferably, the present invention also provides a method for using a tensile testing device for polyethylene pressure pipe and fitting connections, comprising the following steps:

[0020] S1, open the sealing cover on the top of the constant temperature test chamber, and put the three samples into the constant temperature test chamber in sequence through the placement hole, the top limit hole, and the bottom limit hole;

[0021] S2, the main control unit determines whether the bottoms of the three samples are in contact through the contact sensing unit. When it is determined that the three samples are placed normally, the touch screen prompts the user to close the sealing cover.

[0022] S3, the first and second positioning units detect the diameter of the sample tube:

[0023] If the pipe diameter detected by the first positioning unit and the second positioning unit is the outer diameter of the sample tube, the motor unit will drive the top lifting frame to move downward until the pipe diameter detected by the second positioning unit is the outer diameter of the sample tube.

[0024] If the pipe diameter detected by the first positioning unit and the second positioning unit is the outer diameter of the sample tube, the motor unit will drive the top lifting frame to move upward until the pipe diameter detected by the first positioning unit is the outer diameter of the sample tube.

[0025] S4, the upper push clamping cylinder drives the upper inner clamping block to move toward the upper outer clamping block to clamp and fix the end of the sample tube; the lower push clamping cylinder drives the lower inner clamping block to move toward the lower outer clamping block to clamp and fix the end of the sample tube.

[0026] S5 allows users to input the test temperature and the tensile force required for the pull-out test via a touch screen. The constant temperature test chamber adjusts the temperature to the required test temperature through the temperature control component. Subsequently, the motor unit outputs a constant axial tensile force to the top lifting frame via a ball screw to conduct the test.

[0027] S6, the motor unit receives the feedback force from the top lifting frame in real time and transmits it to the main control unit. At the same time, it is displayed in real time on the touch screen. If the feedback force does not change significantly during the test duration, it means that the sample has passed the test. If the feedback force fluctuates, it means that the sample has failed the test.

[0028] The present invention has the following advantages and effects compared with the prior art:

[0029] (1) A constant temperature test chamber is used, which is fixedly installed on the test equipment box, and the pull-out test components are located in the constant temperature test chamber, so as to ensure that the pull-out test process is in the set temperature environment, improve the accuracy and reliability of the test results, and at the same time, different temperature environment conditions can be adjusted according to the needs to meet different test temperature requirements.

[0030] (2) By using a motor unit and a ball screw connected together, a constant longitudinal tension is applied to the sample through the motor unit, which improves the accuracy of applying the longitudinal tension and reduces the complexity of manually adjusting the test load, thereby improving the efficiency of the test and the accuracy and reliability of the test results.

[0031] (3) By using a top clamping unit set on the top lifting frame and a bottom clamping unit set on the bottom clamping frame, the clamping and fixing of the sample tube end and the pipe end can be completed automatically without manual operation of clamping and fixing. The degree of automation is high and the slippage caused by manual clamping instability is avoided. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the tensile strength test equipment for the connection of polyethylene pressure pipes and fittings in Embodiment 1 of the present invention;

[0033] Figure 2 This is a partial cross-sectional schematic diagram of the pull-out resistance test equipment for the connection of polyethylene pressure pipes and fittings in Embodiment 1 of the present invention;

[0034] Figure 3 for Figure 2 Enlarged structural diagram at position A in the middle;

[0035] Figure 4 for Figure 2 A magnified structural diagram at position B in the middle;

[0036] Figure 5 This is a system architecture diagram of the pull-out resistance test equipment for polyethylene pressure pipe and fitting connection in Embodiment 1 of the present invention;

[0037] Figure 6 This is a flowchart illustrating the usage of the pull-out resistance test equipment for polyethylene pressure pipe and fitting connection in Embodiment 2 of the present invention.

[0038] Reference numerals: 1. Test equipment box; 11. Touch screen; 12. Control button; 2. Constant temperature test chamber; 21. Placement hole; 22. Contact sensing unit; 23. Temperature control component; 24. Sealing cover; 25. Viewing window; 26. Guide rod; 3. Ball screw; 4. Top lifting frame; 41. Ball nut; 42. Bracket; 421. Top limit hole; 43. Upper outer clamp; 44. Upper inner clamp; 45. Upper push clamp cylinder; 46. First positioning unit; 47. Second positioning unit; 5. Bottom clamp; 51. Bottom limit hole; 52. Lower outer clamp; 53. Lower inner clamp; 54. Lower push clamp cylinder; 6. Sample. Detailed Implementation

[0039] To enable those skilled in the art to better understand the present invention, specific embodiments will now be described in further detail. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0040] Example 1:

[0041] like Figures 1-5 As shown, this invention provides a tensile testing device for polyethylene pressure pipes and fittings, comprising a testing equipment box 1, a constant temperature testing chamber 2 fixedly mounted on the testing equipment box 1, and a tensile testing assembly. The testing equipment box 1 houses a main control unit, and the constant temperature testing chamber 2 has a closed cavity to provide a test environment with a set temperature for the tensile test. Specifically, the constant temperature testing chamber 2 houses a temperature control assembly 23, and the testing equipment box 1 houses the main control unit. The temperature control assembly 23 is electrically connected to the main control unit. The temperature control assembly 23 specifically includes a heating unit and a temperature sensor (not shown in the figure) mounted on the inner wall of the constant temperature testing chamber 2, and both the heating unit and the temperature sensor are electrically connected to the main control unit. The heating unit can specifically be a heating nickel-chromium wire. Since the heating unit and temperature sensor are not mature existing technologies in this field, their specific structure and principle will not be described here.

[0042] like Figure 1 As shown, the test equipment box 1 is equipped with a touch screen 11 and control buttons 12 arranged at intervals from the constant temperature test chamber 2. The touch screen 11 and control buttons 12 are electrically connected to the main control unit inside the test equipment box 1 so as to control the pull-out test assembly to perform the pull-out test through the touch screen 11 and control buttons 12.

[0043] like Figure 2As shown, the pull-out test assembly includes a motor unit housed in the test equipment box 1, a rotatable ball screw 3 housed in the constant temperature test chamber 2 and connected to the motor unit, a top lifting frame 4 movably sleeved around the ball screw 3, and a bottom clamp 5 fixedly mounted on the bottom wall of the constant temperature test chamber 2. The motor unit includes an electrically connected stepper motor and a motor driver chip. The motor driver chip is electrically connected to the main control unit and can drive the top lifting frame 4 through the ball screw 3 to output a constant upward pulling force. The ball screw 3 is connected to the output shaft of the stepper motor. The motor driver chip is specifically a closed-loop control chip, such as the Trinamic TMC series control chip, which has position detection and feedback functions. Given that this is a mature existing technology, it will not be described in detail here.

[0044] Combination Figure 2 and Figure 3 As shown, the top lifting frame 4 includes a ball nut 41 movably sleeved on the outer periphery of the ball screw 3, and three supports 42 vertically fixedly connected to the ball nut 41. The three supports 42 are evenly spaced along the circumferential direction with the axis of the ball screw 3 as the center. The bottom clamping frame 5 is provided with three supports 42, each corresponding to one of the three supports 42. The supports 42 are provided with a longitudinally penetrating top limiting hole 421, and the bottom clamping frame 5 is provided with a longitudinally penetrating bottom limiting hole 51. The top of the constant temperature test chamber 2 is provided with a longitudinally penetrating placement hole 21. The placement hole 21, the top limiting hole 421, and the bottom limiting hole 51 are arranged longitudinally opposite each other to ensure that the sample 6 is in a longitudinally vertical state during the test.

[0045] Further reference Figure 3 As shown, the upper end face of the support 42 of the top lifting frame 4 is provided with a top clamping unit fixedly connected thereto, which is used to clamp the end of the sample 6 tube. The top clamping unit includes an upper outer clamping block 43 and an upper inner clamping block 44 arranged on both sides of the top limiting hole 421, and an upper push clamping cylinder 45 connected to the upper inner clamping block 44. The upper outer clamping block 43 and the upper push clamping cylinder 45 are both fixedly arranged on the upper end face of the support 42 of the top lifting frame 4. The upper inner clamping block 44 is connected to the end of the piston rod of the upper push clamping cylinder 45 so that when the upper push clamping cylinder 45 pushes the piston rod, the upper inner clamping block 44 is connected to the piston rod end of the upper push clamping cylinder 45. The upper outer clamping block 43 is brought closer to the upper inner clamping block 44, thereby clamping and fixing the tube end of the sample 6. The upper push clamping cylinder 45 is electrically connected to the main control unit. It should be noted that in some embodiments, two upper push clamping cylinders 45 can be provided on both sides of the top limiting hole 421 to push the upper outer clamping block 43 and the upper inner clamping block 44 respectively so that the two move synchronously closer to complete the clamping. In addition, although a cylinder is used in this embodiment, a hydraulic cylinder or a motor can be used to replace the cylinder to achieve clamping in actual products.

[0046] Further reference Figure 4As shown, a bottom clamping unit is fixedly connected to the lower end face of the bottom clamping frame 5 for clamping the tube end of the sample 6. The bottom clamping unit includes a lower outer clamping block 52 and a lower inner clamping block 53 arranged on both sides of the bottom limiting hole 51, and a lower push clamping cylinder 54 connected to the lower inner clamping block 53. The lower outer clamping block 52 and the lower push clamping cylinder 54 are both fixedly arranged on the lower end face of the bottom clamping frame 5. The lower inner clamping block 53 is connected to the piston rod end of the lower push clamping cylinder 54 so that it moves closer to the lower end under the pushing action of the lower push clamping cylinder 54. The outer clamping block 52 is used to clamp and fix the tube end of the sample 6. The lower clamping cylinder 54 is electrically connected to the main control unit. It should be noted that in some embodiments, two lower clamping cylinders 54 can be provided on both sides of the bottom limit hole 51 to push the lower outer clamping block 52 and the lower inner clamping block 53 to move synchronously and close together to complete the clamping. In addition, although a cylinder is used in this embodiment, a hydraulic cylinder or a motor can be used to replace the cylinder to achieve clamping in actual products.

[0047] like Figure 3 As shown, the pull-out test assembly also includes a first positioning unit 46 fixedly mounted on the upper end face of the support 42 of the top lifting frame 4 and a second positioning unit 47 fixedly mounted on the lower end face of the support 42. The first positioning unit 46 and the second positioning unit 47 are arranged close to the upper outer clamping block 43 and facing the top limiting hole 421. The first positioning unit 46 and the second positioning unit 47 are both electrically connected to the main control unit to determine the connection position of the fitting and the pipe by detecting the distance between them and the sample 6. Specifically, the first positioning unit 46 and the second positioning unit 47 are both distance sensors that can work in high-temperature environments, such as infrared distance sensors or grating displacement gauges.

[0048] Further reference Figure 4 As shown, the bottom wall of the constant temperature test chamber 2 is also provided with a contact sensing unit 22 arranged opposite to the bottom limit hole 51. The contact sensing unit 22 is electrically connected to the main control unit. Specifically, it can be a pressure sensor used to detect whether the sample 6 is properly placed so that the main control unit can determine whether the test can be started.

[0049] like Figure 2 As shown, the constant temperature test chamber 2 is also equipped with a guide rod 26 arranged parallel to the ball screw 3. The guide rod 26 is arranged close to the inner wall of the constant temperature test chamber 2. The end of the support 42 of the top lifting frame 4 away from the ball screw 3 is movably inserted through the guide rod 26, which improves the overall stability of the top lifting frame 4 while ensuring that the movement of the support 42 is in the vertical longitudinal direction.

[0050] Combination Figure 1 and Figure 2As shown, the top of the constant temperature test chamber 2 is provided with a sealing cover 24 that can be detachably connected to it, and the sealing cover 24 is placed directly above the placement hole 21; the constant temperature test chamber 2 is provided with at least one viewing window 25 located on its side wall, so as to allow the external observer to directly observe the tensile test process and status inside the constant temperature test chamber 2 through the viewing window 25. Specifically, in this embodiment, three viewing windows 25 are provided and are evenly distributed along the side wall of the constant temperature test chamber 2, so that the test personnel can observe the test process and test status of the three samples 6 through the viewing windows 25 respectively.

[0051] Example 2:

[0052] In Embodiment 2 of the present invention, using Figure 6 The following explanation is provided. Furthermore, the pull-out resistance test equipment for polyethylene pressure pipes and fittings involved in this embodiment specifically adopts the test equipment provided in Example 1. For details, please refer to the content of Example 1 above. Descriptions of parts that are not different from those in Example 1 are omitted, and the same reference numerals are used.

[0053] like Figure 6 As shown, the method of using the pull-out resistance testing equipment for polyethylene pressure pipe and fitting connections involved in this invention specifically includes the following steps:

[0054] S1. Open the sealing cover 24 on the top of the constant temperature test chamber 2, and insert three qualified test specimens 6 vertically into the constant temperature test chamber through the placement hole 21 and the top limiting hole 421 and bottom limiting hole 51. It should be noted that the test specimens 6 must meet the requirements in the standard, such as the pipe diameter not exceeding 63mm and the pipe length being at least 300mm. For details, please refer to the relevant provisions in GB / T15820-1995 "Pull-out test of polyethylene pressure pipes and fittings". In addition, the pipe should not be too long. If the pipe is too long, it can be cut as needed to avoid the pipe length being too long to be clamped on the fitting. At the same time, the pipe diameter of the test specimens 6 has been measured to calculate the tensile force required for the test. The specific formula can be found in the standard, which will not be repeated here.

[0055] S2, the main control unit determines whether the bottoms of the three samples 6 are in contact with the insertion through the contact sensing unit 22 (the pressure detection value of the contact sensing unit 22 changes). When it is determined that the three samples 6 are properly inserted, the touch display screen 11 prompts to close the sealing cover 24.

[0056] S3, the first positioning unit 46 and the second positioning unit 47 detect the diameter of the sample 6: If the diameter (distance) detected by the first positioning unit 46 and the second positioning unit 47 is the outer diameter of the sample 6, the motor unit drives the top lifting frame 4 to move downward a certain distance through the ball screw 3 until the diameter detected by the second positioning unit 47 is the outer diameter of the sample 6; if the diameter detected by the first positioning unit 46 and the second positioning unit 47 is the outer diameter of the sample 6, the motor unit drives the top lifting frame 4 to move upward a certain distance through the ball screw 3 until the diameter detected by the first positioning unit 46 is the outer diameter of the sample 6; that is, ensuring that the first positioning unit 46 detects the outer diameter of the sample 6 and the second positioning unit 47 detects the outer diameter of the sample 6, thereby ensuring that the top clamping unit clamps and fixes the end of the sample 6; then proceed to the next step.

[0057] S4, the upper push-clamp cylinder 45 drives the upper inner clamping block 44 to move toward the upper outer clamping block 43 to clamp and fix the end of the sample 6 pipe. The lower push-clamp cylinder 54 drives the lower inner clamping block 53 to move toward the lower outer clamping block 52 to clamp and fix the end of the sample 6 pipe. It should be noted that the clamping force applied to the sample 6 by the upper push-clamp cylinder 45 and the lower push-clamp cylinder 54 is specifically set according to the material and pipe diameter of the sample 6 to ensure the stability of the clamping and prevent slippage.

[0058] S5, the test temperature and the tensile force required for the pull-out test are input through the touch screen 11. The constant temperature test chamber 2 adjusts the temperature of the closed cavity to the required test temperature (e.g., 23±2℃) through the temperature control component 23. Then, the motor unit outputs the corresponding constant tensile force to the top lifting frame 4 through the ball screw 3 to conduct the test, so as to apply a constant longitudinal (axial) tensile force to the sample 6. Furthermore, the test personnel only need to input the pipe diameter data of the measured sample 6 through the touch screen 11, and the main control unit will automatically calculate the tensile force required for the test based on the pipe diameter data, without the need for manual calculation.

[0059] S6, the motor unit receives the feedback force from the top lifting frame 4 (load) in real time and transmits it to the main control unit for storage and recording. At the same time, it is displayed in real time on the touch screen 11. If the feedback force received by the motor unit does not change significantly within the test duration (such as 1 hour as specified in the standard), it means that the sample 6 has passed the test. If the feedback force received by the motor unit fluctuates, it means that at least one of the fittings and pipes of the sample 6 has become loose, that is, the load at the load end has changed. In this case, it means that the sample 6 has failed the test.

[0060] Furthermore, it should be noted that although the device provided in this embodiment can test three specimens 6 simultaneously, a single specimen 6 can be tested according to actual test requirements. Given that the existing tensile tester device requires testing three specimens 6 separately, and all three specimens 6 must remain intact to be considered as having passed the test, testing three specimens 6 simultaneously can improve test efficiency. At the same time, since the test environment conditions are the same, the phenomenon of test result distortion caused by errors in the test environment conditions during separate tests can be avoided.

[0061] In summary, the pull-out resistance testing equipment for polyethylene pressure pipes and fittings provided by this invention has a high degree of automation, which improves the efficiency of pull-out resistance testing, avoids test errors caused by improper manual operation, and improves the accuracy of test results.

[0062] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. All equivalent changes and modifications made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. A polyethylene pressure pipe and fitting pull resistance test apparatus, characterized by: The application relates to a tensile test device, which comprises a test device box (1), a constant-temperature test cabin (2) fixedly arranged on the test device box (1), and a tensile test assembly. The tensile test assembly comprises a motor unit arranged in the test device box (1), a ball screw (3) rotatably arranged in the constant-temperature test cabin (2) and connected with the motor unit, a top lifting frame (4) movably sleeved on the outer periphery of the ball screw (3), and a bottom clamping frame (5) fixedly arranged on the bottom wall of the constant-temperature test cabin (2), wherein the top lifting frame (4) is provided with a top clamping unit for clamping the pipe end of a test sample (6), and the bottom clamping frame (5) is provided with a bottom clamping unit for clamping the pipe end of the test sample (6). The top lifting frame (4) comprises a ball nut (41) movably sleeved on the outer periphery of the ball screw (3), and three supports (42) fixedly and perpendicularly connected with the ball nut (41), wherein the supports (42) are uniformly and circumferentially spaced, the bottom clamping frame (5) is provided with three bottom clamping units corresponding to the three supports (42) respectively, the supports (42) are provided with top limiting holes (421) longitudinally penetrating through, the bottom clamping frame (5) is provided with bottom limiting holes (51) longitudinally penetrating through, and the top wall of the constant-temperature test cabin (2) is provided with a placing hole (21) longitudinally penetrating through, wherein the placing hole (21), the top limiting holes (421) and the bottom limiting holes (51) are longitudinally and oppositely arranged. The tensile test assembly further comprises a first positioning unit (46) fixedly arranged on the upper end face of the support (42) and a second positioning unit (47) fixedly arranged on the lower end face of the support (42), wherein the first positioning unit (46) and the second positioning unit (47) are arranged towards the top limiting holes (421). The test device box (1) is internally provided with a main control unit, the first positioning unit (46) and the second positioning unit (47) are electrically connected with the main control unit, the bottom wall of the constant-temperature test cabin (2) is provided with a contact sensing unit (22) oppositely arranged with the bottom limiting holes (51), and the contact sensing unit (22) is electrically connected with the main control unit.

2. The polyethylene pressure pipe and fitting pull resistance test apparatus of claim 1, wherein: The top clamping unit is arranged on the upper end face of the support (42) and comprises upper outer clamping blocks (43) and upper inner clamping blocks (44) arranged on both sides of the top limiting holes (421), and an upper pushing clamping cylinder (45) connected with the upper inner clamping blocks (44), wherein the upper outer clamping blocks (43) and the upper pushing clamping cylinder (45) are fixedly connected with the support (42). The bottom clamping unit is arranged on the lower end face of the bottom clamping frame (5) and comprises lower outer clamping blocks (52) and lower inner clamping blocks (53) arranged on both sides of the bottom limiting holes (51), and a lower pushing clamping cylinder (54) connected with the lower inner clamping blocks (53), wherein the lower outer clamping blocks (52) and the lower pushing clamping cylinder (54) are fixedly connected with the bottom clamping frame (5).

3. The polyethylene pressure pipe and fitting pull- out resistance test apparatus of claim 2, wherein: The motor unit is electrically connected with the main control unit, and the upper pushing clamping cylinder (45) and the lower pushing clamping cylinder (54) are electrically connected with the main control unit.

4. The polyethylene pressure pipe and fitting pull- out resistance test apparatus of claim 1, wherein: The constant-temperature test cabin (2) is internally provided with a temperature control assembly (23) which is electrically connected with the main control unit.

5. The polyethylene pressure pipe and fitting pull- out test apparatus of claim 1, wherein: The test equipment box (1) is provided with a touch display screen (11) and a control button (12) which are arranged at intervals with the constant-temperature test cabin (2), and the touch display screen (11) and the control button (12) are electrically connected with the main control unit.

6. The polyethylene pressure pipe and fitting pull- out test apparatus of claim 1, wherein: The constant-temperature test cabin (2) is provided with a detachable sealing cover (24) on the top thereof, the sealing cover (24) is arranged directly above the placing hole (21), and the sidewall of the constant-temperature test cabin (2) is provided with at least one visual window (25).

7. A method of using the polyethylene pressure pipe and fitting connection pull-out test apparatus of claim 1, wherein, The method comprises the following steps: S1, the sealing cover (24) on the top of the constant-temperature test cabin (2) is opened, and the three test samples (6) are sequentially placed into the constant-temperature test cabin (2) through the placing hole (21), the top limiting hole (421) and the bottom limiting hole (51); S2, the main control unit judges whether the bottoms of the three test samples (6) are in contact through the contact sensing unit (22), and when it is judged that the three test samples (6) are normally placed, the touch display screen (11) prompts to close the sealing cover (24); S3, the first positioning unit (46) and the second positioning unit (47) detect the pipe diameter of the test sample (6): If the pipe diameters detected by the first positioning unit (46) and the second positioning unit (47) are both the outer diameters of the pipe fittings of the test sample (6), the motor unit drives the top lifting frame (4) to move downward until the pipe diameter detected by the second positioning unit (47) is the outer diameter of the pipe material of the test sample (6); If the pipe diameters detected by the first positioning unit (46) and the second positioning unit (47) are both the outer diameters of the pipe materials of the test sample (6), the motor unit drives the top lifting frame (4) to move upward until the pipe diameter detected by the first positioning unit (46) is the outer diameter of the pipe fitting of the test sample (6); S4, the upper push cylinder (45) drives the upper inner clamping block (44) to move towards the upper outer clamping block (43) to clamp and fix the pipe fitting end of the test sample (6), and the lower push cylinder (54) drives the lower inner clamping block (53) to move towards the lower outer clamping block (52) to clamp and fix the pipe material end of the test sample (6); S5, the test temperature and the required pulling force for the pull-out resistance test are input through the touch display screen (11), the constant-temperature test cabin (2) adjusts the temperature to the required test temperature through the temperature control assembly (23), and then the motor unit outputs a constant axial pulling force to the top lifting frame (4) through the ball screw (3) to perform the test; S6, the motor unit receives the feedback force of the top lifting frame (4) in real time and transmits it to the main control unit, and simultaneously displays it in real time through the touch display screen (11), if the feedback force does not change significantly during the test duration, it represents that the test sample (6) passes the test, and if the feedback force fluctuates, it represents that the test sample (6) fails the test.

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