Accelerated test device and method for fatigue life of rubber bellows limiting structure

Abstract

The present application belongs to the technical field of fatigue life accelerated test equipment, in particular to a kind of rubber bellows limiting structure fatigue life accelerated test device and method, including base and heat insulation test box, the bottom end of heat insulation test box is fixedly connected with the upper surface of base, and two fixed through holes are formed in the side outer wall of heat insulation test box.The present application makes the device have the function of multiple environment simulation, builds the composite test environment close to actual working condition, reflects the influence of different environments on the fatigue life of limiting structure, improves the representativeness of rubber bellows limiting structure fatigue life test results, and realizes automatic failure determination through real-time monitoring of resistance, without manual intervention, which improves the convenience of test, further improves the accuracy of rubber bellows limiting structure fatigue life test results, and the device also realizes double-sample synchronous test, greatly shortens the time consumption of multi-sample test, significantly improves the detection efficiency of fatigue test.

Description

Technical Field

[0001] This invention belongs to the technical field of fatigue life accelerated testing equipment, and in particular relates to an accelerated testing device and method for the fatigue life of a rubber bellows limiting structure. Background Technology

[0002] Rubber bellows is a tubular component made of rubber with elastic expansion and contraction properties. In pipeline connection scenarios, it is often installed at pipe joints. Its core function is to compensate for the displacement of the pipeline caused by thermal expansion and contraction, installation deviation, or vibration. It also has the functions of shock absorption, sealing and leak prevention, and buffering the pressure impact of the medium, ensuring the operational stability of the pipeline system. Because rubber bellows are highly elastic, they are prone to excessive stretching, compression, or even deformation and damage under long-term stress or extreme working conditions. Therefore, a limiting structure needs to be set on its outer side to limit the expansion and contraction stroke and prevent it from exceeding the elastic limit. This limiting structure usually consists of two metal connecting flanges (fixed to the pipe joint and the end of the bellows respectively) and multiple evenly distributed threaded connecting rods and nut assemblies. The limiting is achieved by adjusting the length of the connecting rods to ensure that the bellows works within a safe range.

[0003] As a key load-bearing component in pipeline connections, the limiting structure of rubber bellows is subjected to the cyclic effects of medium pressure, pipeline vibration, and environmental loads over a long period of time, which can easily lead to fatigue damage. If it fails, it may cause safety hazards such as pipeline leakage and uncontrolled displacement. Therefore, it is necessary to quickly assess its service life through accelerated fatigue life testing to provide data support for the reliability of pipeline systems.

[0004] However, the existing test process has obvious defects and generally ignores the impact of changes in the actual use environment of rubber bellows on the fatigue life of the limiting structure, resulting in insufficient accuracy of the test results. For example, rust interference is ignored. Metal limiting structures are prone to rust in marine and humid environments, which causes a decrease in structural strength and an increase in wear. However, the existing tests are mostly carried out in dry and non-corrosive environments, which do not simulate this working condition and cannot reflect the actual fatigue life.

[0005] Secondly, ignoring the actual interference of short-term large temperature fluctuations, in the actual application scenarios of rubber bellows, short-term drastic temperature fluctuations will directly change the mechanical properties (such as toughness and strength) of the metal limiting structure, thereby affecting the initiation and propagation rate of fatigue cracks. Traditional tests mostly use constant temperature environment for testing, completely ignoring the impact of this key working condition factor on the actual fatigue life of the limiting structure.

[0006] Moreover, traditional fatigue life tests generally adopt a mode of testing individual samples one by one. This testing method can be time-consuming when there are sufficient samples, which affects the detection efficiency of accelerated fatigue life testing of rubber bellows limiting structures.

[0007] To address this issue, we propose an accelerated testing device and method for the fatigue life of rubber bellows limiting structures. Summary of the Invention

[0008] The purpose of this invention is to address the above-mentioned problems by providing an accelerated testing device and method for the fatigue life of rubber bellows limiting structures.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: an accelerated testing device for the fatigue life of a rubber corrugated pipe limiting structure, comprising a base and a heat insulation test chamber, wherein the bottom end of the heat insulation test chamber is fixedly connected to the upper surface of the base, and two fixed through holes are opened on one side of the outer wall of the heat insulation test chamber, and a first metal bearing is fixedly connected to the hole wall of the fixed through hole, and a first rotating metal block and a second rotating metal block are respectively fixedly connected to the inner walls of the two first metal bearings; two movable through holes are opened on the outer wall of the other side of the heat insulation test chamber at a position symmetrical to the first metal bearing, and a third rotating metal block and a fourth rotating metal block are movably connected to the hole walls of the two movable through holes;

[0010] A corrosion environment simulation mechanism is fixedly connected to the inner wall of the base;

[0011] A transverse load simulation mechanism is fixedly connected to the outer wall of the thermal insulation test chamber;

[0012] Multiple thermally conductive and corrosion-resistant coils are fixedly embedded in the side wall of the base, and a temperature simulation mechanism is fixedly sleeved on both sides of the multiple thermally conductive and corrosion-resistant coils.

[0013] A U-shaped plate and a PLC controller are fixedly connected to the upper surface of the base, and an impact acceleration mechanism is fixedly connected to the upper surface of the U-shaped plate.

[0014] An automated control mechanism is fixedly connected to the outer wall of the U-shaped plate.

[0015] In the aforementioned accelerated fatigue life testing device for a rubber bellows limiting structure, the first rotating metal block, the second rotating metal block, the third rotating metal block, and the fourth rotating metal block are all fixedly fitted with metal flanges on the side walls inside the heat insulation test chamber.

[0016] In the aforementioned accelerated fatigue life testing device for a rubber corrugated pipe limiting structure, the corrosion environment simulation mechanism includes a partition fixedly connected to the inner wall of the base. A fixing hole is provided on the outer wall of the partition, and a first electric push rod is fixedly connected to the hole wall. The moving end of the first electric push rod is fixedly connected to a piston that is slidably and sealingly connected to the inner wall of the base. The base is filled with a brine layer. A return one-way valve is fixedly embedded on the upper surface of the base inside the heat insulation test chamber. A filter element is fixedly connected to the inlet end of the return one-way valve. A heat insulation delivery pipe is fixedly embedded on the upper surface of the base. The bottom end of the heat insulation delivery pipe is located inside the brine layer and is fixedly connected to an inlet one-way valve. A heat insulation hollow block is fixedly connected to the top end of the heat insulation delivery pipe. The bottom end of the heat insulation hollow block is embedded through the top of the heat insulation test chamber. Multiple ceramic heat insulation atomizing nozzles are fixedly connected to the bottom end of the heat insulation hollow block.

[0017] In the aforementioned accelerated fatigue life testing device for a rubber bellows limiting structure, the transverse load simulation mechanism includes a U-shaped frame fixedly connected to the outer wall of the heat insulation test chamber. Two second electric push rods are embedded through the vertical part of the U-shaped frame. A pressure sensor is fixedly connected to the moving end of the second electric push rod. A second metal bearing is fixedly sleeved on the outer wall of the fixed end of the pressure sensor. The inner walls of the two second metal bearings are fixedly connected to the outer walls of the third and fourth rotating metal blocks respectively through connecting blocks.

[0018] In the aforementioned accelerated fatigue life testing device for a rubber corrugated pipe limiting structure, the temperature simulation mechanism includes a heat insulation box that is fixedly sleeved with both ends of multiple thermally conductive and corrosion-resistant coils. A metal plate is fixedly embedded at the top of the heat insulation box, and multiple semiconductor coolers are fixedly connected to the upper surface of the metal plate. Multiple metal mesh plates are fixedly connected to the lower surface of the metal plate. Multiple electric heating tubes are fixedly embedded in the side wall of the heat insulation box, and the heating ends of the electric heating tubes penetrate through the multiple metal mesh plates. A mounting plate is fixedly connected to the inner wall of the heat insulation box, and a mounting hole is opened on the upper surface of the mounting plate. A heat-resistant circulating fan is fixedly connected to the wall of the mounting hole.

[0019] In the aforementioned accelerated fatigue life testing device for a rubber bellows limiting structure, the impact acceleration mechanism includes a servo motor fixedly connected to the upper surface of a U-shaped plate. The drive end of the servo motor is fixedly connected to the center of the side end of the second rotating metal block. Sprockets are fixedly sleeved on the outer walls of both the first and second rotating metal blocks. A transmission chain is sleeved on the outer walls of the two sprockets. A speed sensor is fixedly embedded in the side wall of the U-shaped plate. A speed indicator block cooperating with the speed sensor is fixedly connected to the outer wall of one of the sprockets. A crossbar is fixedly connected to the inner wall of the heat insulation test chamber. Two symmetrically distributed impact components are fixedly connected to the outer wall of the crossbar.

[0020] In the aforementioned accelerated fatigue life testing device for a rubber bellows limiting structure, the impact assembly includes a rubber sleeve and a return spring fixedly connected to the outer wall of the crossbar, and the top ends of the rubber sleeve and the return spring are jointly fixedly connected to an impact metal cover.

[0021] In the aforementioned accelerated fatigue life testing device for a rubber corrugated pipe limiting structure, the automated control mechanism includes a display and control panel and an alarm fixedly connected to the outer wall of the U-shaped plate. The side wall of the heat insulation test chamber has two through holes, and the walls of the two through holes are fixedly connected to a salt spray concentration sensor and a temperature sensor. The outer wall of the U-shaped frame is fixedly connected to two electronic ohmmeters. The two resistance terminals of one of the electronic ohmmeters are fixedly connected to the outer wall of the first metal bearing located at the first rotating metal block and the outer wall of the second metal bearing located at the third rotating metal block, respectively. The two resistance terminals of the other electronic ohmmeter are fixedly connected to the outer wall of the first metal bearing located at the second rotating metal block and the outer wall of the second metal bearing located at the fourth rotating metal block, respectively.

[0022] A method for accelerating the fatigue life testing of the aforementioned rubber bellows limiting structure, the method comprising the following steps:

[0023] S1. Test preparation: Select a defect-free rubber bellows limiting structure sample and fix it to two sets of metal flanges inside the heat insulation test chamber with stainless steel bolts. One set is connected to the first and third rotating metal blocks, and the other set is connected to the second and fourth rotating metal blocks. Inject a salt solution of a preset concentration into the base to form a salt solution layer. Input the test parameters (maximum impact value, temperature cycle threshold, salt spray concentration threshold, and lateral load threshold) to the PLC controller through the display control panel. Calibrate the zero position of each sensor and then close the door of the heat insulation test chamber.

[0024] S2. Composite Environment and Fatigue Impact Start-up: The PLC controller synchronously starts the impact acceleration mechanism, temperature simulation mechanism, corrosion environment simulation mechanism, and lateral load simulation mechanism. The impact acceleration mechanism drives two sets of samples to rotate synchronously. The speed sensor, together with the speed indicator block, monitors the speed and maintains stability. The PLC controller provides real-time feedback on the cumulative number of fatigue impacts. Each simulation mechanism constructs a composite environment according to preset parameters. The temperature simulation mechanism adjusts the temperature of the brine layer through a thermally conductive and corrosion-resistant coil. The brine, after being heated or cooled, is transported through a heat-insulated conveying pipe and a heat-insulated hollow block, and then atomized and sprayed by a ceramic heat-insulated atomizing nozzle. Through the heat insulation components working together to keep the temperature warm and the PLC controller dynamically adjusting the power of the electric heating tube, the semiconductor cooler, and the wind speed of the heat-resistant circulating fan, the temperature of the atomized salt spray is ensured to deviate from the preset temperature by ≤±2℃.

[0025] S3. Real-time monitoring and data acquisition: The electronic ohmmeter monitors the resistance values ​​of two sets of samples in real time. The temperature sensor, salt spray concentration sensor, and pressure sensor simultaneously collect environmental and load data. All data are fed back to the PLC controller and stored in real time. The speed sensor continuously monitors the speed and dynamically compensates for it.

[0026] S4. Failure Judgment and Data Storage: The PLC controller compares the current resistance value of the sample with the initial calibration resistance value before the test starts in real time. If the resistance change rate of a sample exceeds 30%, it is judged as the first fatigue failure, the alarm is immediately activated, and the failure data of the sample is stored. If the resistance change rate of the same sample exceeds 30% again, only the failure data is updated, and the alarm is not repeated. The test continues for samples that have not failed until another set of samples reaches the failure threshold for the first time or the test reaches the preset maximum number of cycles. At this time, the PLC controller controls all mechanisms to stop working and stores the data of the second set of samples (if no failure occurs, the maximum number of cycles and the sample status are recorded).

[0027] S5. Sample rotation and repeated testing: Remove the failed sample, clean the insulation test chamber and metal flange connection surface, replace with two new sets of parallel samples, and repeat steps S1-S4 until all samples have been tested. If equipment failure occurs, the PLC controller will pause the test and record the data. The test will continue after the fault is cleared.

[0028] S6. Data Processing and Result Output: The PLC controller removes abnormal data, calculates the average cumulative fatigue impact count of valid samples, and generates a test report containing sample information, test parameters, failure data, and environmental curves. The report can be exported or printed via the display control panel.

[0029] S7. Test Completion: Drain the brine layer inside the base, rinse the brine circulation system, clean the impurities on the surface of the heat insulation test chamber and each mechanism, reset all mechanisms to their initial state, and turn off the power to complete the test.

[0030] Compared with existing technologies, the advantages of an accelerated testing device and method for the fatigue life of a rubber bellows limiting structure are:

[0031] 1. By setting up temperature simulation mechanism, corrosion environment simulation mechanism and lateral load simulation mechanism, a composite test environment with large periodic temperature fluctuations, salt spray corrosion and cyclic lateral load is constructed in a coordinated manner. This accurately restores the actual working conditions of the rubber bellows limiting structure, solves the problem that the existing test ignores environmental factors (such as corrosion and temperature fluctuations) and causes large deviations between the test results and the actual lifespan, and significantly improves the representativeness and accuracy of the test results.

[0032] 2. By setting up a first rotating metal block, a second rotating metal block, a third rotating metal block, a fourth rotating metal block, and matching metal flanges, the synchronous installation and parallel testing of two sets of test samples can be achieved. With the servo motor, sprocket, and transmission chain drive design of the impact acceleration mechanism, the total time for multi-sample testing is greatly shortened, effectively solving the pain point of low efficiency in traditional single-sample testing, and significantly improving the detection efficiency of fatigue testing.

[0033] 3. An automatic failure determination system based on resistance change was constructed by setting up an electronic ohmmeter, a PLC controller, and an alarm. The electronic ohmmeter monitors the resistance value at both ends of the sample in real time, and the PLC controller automatically compares the resistance change rate. When the change rate exceeds 30%, it is immediately determined to be fatigue failure and the alarm is triggered. At the same time, the failure data is stored. No manual intervention is required, which not only improves the convenience of the test operation, but also avoids the subjectivity of manual judgment and ensures the objectivity and accuracy of the test data.

[0034] 4. By using the return check valve, filter cartridge, and inlet check valve in the corrosion environment simulation mechanism, the brine solution can be recycled and reused. The filter cartridge can filter out large particulate impurities in the brine solution, avoiding clogging of the ceramic heat-insulated atomizing nozzle. This reduces the cost of consumables for the experiment, protects the stable operation of the corrosion environment simulation mechanism, and extends the service life of the equipment.

[0035] 5. By using the speed sensor, speed indicator block and PLC controller in the impact acceleration mechanism, the rotation speed of the sample is monitored in real time and dynamic compensation is performed to ensure that the preset fatigue impact force is maintained throughout the test, avoiding the problem of inconsistent impact intensity caused by speed fluctuations, and ensuring the stability and accuracy of the test process.

[0036] 6. Through the pressure sensor and the second electric push rod in the set lateral load simulation mechanism, lateral load data is collected in real time and fed back to the PLC controller. When the load exceeds the preset threshold, the electric push rod is automatically controlled to extend and retract in the opposite direction. This not only accurately simulates the cyclic action of lateral load in actual working conditions, but also allows the impact component to impact different positions of the sample threaded connecting rod, restoring the real scenario of uncertain fatigue impact position. In addition, through the soft connection of rubber sleeve and return spring, the impact metal cover plays a buffering role when it contacts the sample threaded connecting rod, avoiding non-fatigue damage to the sample caused by rigid impact. This ensures that the sample failure is only caused by cyclic fatigue impact, further improving the authenticity and accuracy of the test. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the structure of an accelerated testing device and method for the fatigue life of a rubber bellows limiting structure provided by the present invention.

[0038] Figure 2yes Figure 1 A cross-sectional structural diagram;

[0039] Figure 3 yes Figure 2 A three-dimensional structural diagram of the metal flange section;

[0040] Figure 4 yes Figure 2 A three-dimensional structural diagram of the intermediate speed indicator block;

[0041] Figure 5 yes Figure 2 A three-dimensional structural schematic diagram of the impact component.

[0042] Figure 6 yes Figure 2 A three-dimensional structural diagram of the medium-temperature simulation mechanism.

[0043] In the diagram: 1. Base; 2. Thermal insulation test chamber; 3. First metal bearing; 4. Temperature simulation mechanism; 41. Thermal insulation box; 42. Metal plate; 43. Semiconductor cooler; 44. Metal mesh plate; 45. Electric heating tube; 46. Mounting plate; 47. Heat-resistant circulating fan; 5. Corrosion environment simulation mechanism; 51. Partition plate; 52. First electric push rod; 53. Piston; 54. Brine layer; 55. Return check valve; 56. Filter block; 57. Thermal insulation delivery pipe; 58. Inlet check valve; 59. Thermal insulation hollow block; 510. Ceramic thermal insulation atomizing nozzle; 6. Lateral load simulation mechanism; 61. U-shaped frame; 62. Second electric push rod; 63. Pressure sensor; 64. 7. Second metal bearing; 8. Impact acceleration mechanism; 9. Servo motor; 10. Sprocket; 11. Transmission chain; 12. Speed ​​sensor; 13. Speed ​​indicator block; 14. Crossbar; 15. Impact assembly; 16. Rubber sleeve; 17. Return spring; 18. Impact metal cover; 19. Automated control mechanism; 10. Display control panel; 10. Alarm; 11. Salt spray concentration sensor; 12. Temperature sensor; 13. Electronic ohmmeter; 14. First rotating metal block; 15. Second rotating metal block; 16. Third rotating metal block; 17. Fourth rotating metal block; 18. Thermally conductive and corrosion-resistant coil; 19. U-shaped plate; 10. PLC controller; 11. Metal flange. Detailed Implementation

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] like Figures 1-6As shown, an accelerated testing device for the fatigue life of a rubber corrugated pipe limiting structure includes a base 1 and a heat insulation test chamber 2. The bottom end of the heat insulation test chamber 2 is fixedly connected to the upper surface of the base 1. Two fixed through holes are opened on one side of the outer wall of the heat insulation test chamber 2, and a first metal bearing 3 is fixedly connected to the hole wall of the fixed through hole. A first rotating metal block 10 and a second rotating metal block 11 are fixedly connected to the inner walls of the two first metal bearings 3, respectively. Two movable through holes are opened on the outer wall of the other side of the heat insulation test chamber 2 at a position symmetrical to the first metal bearings 3, and a third rotating metal block 12 and a fourth rotating metal block 13 are movably connected to the hole walls of the two movable through holes.

[0046] A corrosion environment simulation mechanism 5 is fixedly connected to the inner wall of the base 1. The corrosion environment simulation mechanism 5 includes a partition 51 fixedly connected to the inner wall of the base 1. A fixing hole is opened on the outer wall of the partition 51, and a first electric push rod 52 is fixedly connected to the wall of the fixing hole. The moving end of the first electric push rod 52 is fixedly connected to a piston 53 that is slidably and sealingly connected to the inner wall of the base 1. The interior of the base 1 is filled with a brine liquid layer 54. A one-way return liquid system is fixedly embedded on the upper surface of the base 1 located inside the heat insulation test chamber 2. A filter element block 56 is fixedly connected to the inlet end of valve 55 and return check valve 55. A heat insulation delivery pipe 57 is fixedly embedded on the upper surface of base 1. The bottom end of heat insulation delivery pipe 57 is located inside brine layer 54 and is fixedly connected to inlet check valve 58. A heat insulation hollow block 59 is fixedly connected to the top end of heat insulation delivery pipe 57. The bottom end of heat insulation hollow block 59 is embedded through the top of heat insulation test chamber 2. Multiple ceramic heat insulation atomizing nozzles 510 are fixedly connected to the bottom end of heat insulation hollow block 59.

[0047] A transverse load simulation mechanism 6 is fixedly connected to the outer wall of the heat insulation test chamber 2. The transverse load simulation mechanism 6 includes a U-shaped frame 61 fixedly connected to the outer wall of the heat insulation test chamber 2. Two second electric push rods 62 are embedded through the vertical part of the U-shaped frame 61. A pressure sensor 63 is fixedly connected to the moving end of the second electric push rod 62. A second metal bearing 64 is fixedly sleeved on the outer wall of the fixed end of the pressure sensor 63. The inner walls of the two second metal bearings 64 are fixedly connected to the outer walls of the third rotating metal block 12 and the fourth rotating metal block 13 respectively through connecting blocks.

[0048] Multiple thermally conductive and corrosion-resistant coils 14 are fixedly embedded in the side wall of the base 1. A temperature simulation mechanism 4 is fixedly sleeved on both sides of the multiple thermally conductive and corrosion-resistant coils 14. The temperature simulation mechanism 4 includes a heat insulation box 41 that is fixedly sleeved on both sides of the multiple thermally conductive and corrosion-resistant coils 14. A metal plate 42 is fixedly embedded in the top of the heat insulation box 41. Multiple semiconductor coolers 43 are fixedly connected to the upper surface of the metal plate 42. Multiple metal mesh plates 44 are fixedly connected to the lower surface of the metal plate 42. Multiple electric heating tubes 45 are fixedly embedded in the side wall of the heat insulation box 41. The heating end of the electric heating tube 45 passes through the multiple metal mesh plates 44. A mounting plate 46 is fixedly connected to the inner wall of the heat insulation box 41. A mounting hole is opened on the upper surface of the mounting plate 46, and a heat-resistant circulating fan 47 is fixedly connected to the wall of the mounting hole.

[0049] A U-shaped plate 15 and a PLC controller 16 are fixedly connected to the upper surface of the base 1. An impact acceleration mechanism 7 is fixedly connected to the upper surface of the U-shaped plate 15. The impact acceleration mechanism 7 includes a servo motor 71 fixedly connected to the upper surface of the U-shaped plate 15. The drive end of the servo motor 71 is fixedly connected to the center of the side end of the second rotating metal block 11. A sprocket 72 is fixedly sleeved on the outer wall of both the first rotating metal block 10 and the second rotating metal block 11. A transmission chain 73 is sleeved on the outer wall of both sprockets 72. A speed sensor 74 is fixedly embedded on the side wall of the U-shaped plate 15. A speed indicator block 75 that cooperates with the speed sensor 74 is fixedly connected to the outer wall of one of the sprockets 72. A crossbar 76 is fixedly connected to the inner wall of the heat insulation test chamber 2. Two symmetrically distributed impact components 8 are fixedly connected to the outer wall of the crossbar 76. The impact component 8 includes a rubber sleeve 81 and a return spring 82 fixedly connected to the outer wall of the crossbar 76. An impact metal cover 83 is fixedly connected to the top of the rubber sleeve 81 and the return spring 82.

[0050] An automated control mechanism 9 is fixedly connected to the outer wall of the U-shaped plate 15. The automated control mechanism 9 includes a display control panel 91 and an alarm 92 fixedly connected to the outer wall of the U-shaped plate 15. Two through holes are opened on the side wall of the heat insulation test chamber 2, and a salt spray concentration sensor 93 and a temperature sensor 94 are fixedly connected to the walls of the two through holes. Two electronic ohmmeters 95 are fixedly connected to the outer wall of the U-shaped frame 61. The two resistance terminals of one electronic ohmmeter 95 are fixedly connected to the outer wall of the first metal bearing 3 located at the first rotating metal block 10 and the outer wall of the second metal bearing 64 located at the third rotating metal block 12, respectively. The two resistance terminals of the other electronic ohmmeter 95 are fixedly connected to the outer wall of the first metal bearing 3 located at the second rotating metal block 11 and the outer wall of the second metal bearing 64 located at the fourth rotating metal block 13, respectively.

[0051] The first rotating metal block 10, the second rotating metal block 11, the third rotating metal block 12, and the fourth rotating metal block 13 are all fixedly fitted with metal flanges 17 on the side walls inside the heat insulation test chamber 2.

[0052] The semiconductor cooler 43, electric heating tube 45, heat-resistant circulating fan 47, first electric push rod 52, second electric push rod 62, servo motor 71, and alarm 92 are all electrically connected to the output terminal of PLC controller 16 via wires. The display control panel 91, salt spray concentration sensor 93, temperature sensor 94, electronic ohmmeter 95, speed sensor 74, and pressure sensor 63 are all electrically connected to the input terminal of PLC controller 16 via wires. In addition, the metallic structures that can contact the brine in this invention are made of titanium alloy (TA2). The surface of titanium alloy has a stable oxide film and strong corrosion resistance. The non-metallic structures that contact the brine are made of engineering plastics or rubber materials. For example, the base 1 and the heat insulation test chamber 2 are both made of engineering plastics (PPH). The above-mentioned electrical components, electrical connections, and selected materials are all existing technologies and will not be described in detail here.

[0053] The operating principle of the present invention is described as follows: When it is necessary to conduct an accelerated fatigue life test on the produced rubber corrugated pipe limiting structure, the staff first extracts a sufficient number of rubber corrugated pipe limiting structure samples, then grinds the surface of the rubber corrugated pipe limiting structure to remove the oxide layer and impurity layer, and at the same time, two rubber corrugated pipe limiting structures are installed in the heat insulation test chamber 2 each time.

[0054] The specific connection method is as follows: one rubber bellows limiting structure is fixedly connected to the metal flange 17 at the first rotating metal block 10 and the third rotating metal block 12 by stainless steel bolts, and the other rubber bellows limiting structure is fixedly connected to the metal flange 17 at the second rotating metal block 11 and the fourth rotating metal block 13 by stainless steel bolts.

[0055] After closing the door of the thermal insulation test chamber 2, the maximum impact value preset during the design of the rubber bellows limiting structure is input into the display control panel 91. The display control panel 91 feeds back this parameter to the PLC controller 16. Subsequently, the PLC controller 16 controls the servo motor 71 to be powered on and started. The servo motor 71 drives the second rotating metal block 11 to rotate. The second rotating metal block 11 drives the first rotating metal block 10 to rotate synchronously through the sprocket 72 and the transmission chain 73, thereby driving the two rubber bellows limiting structure samples in the thermal insulation test chamber 2 to rotate together. During the rotation, each threaded connecting rod of the two rubber bellows limiting structures will contact the impact component 8. Each time the impact component 8 impacts the threaded connecting rod, it can simulate one fatigue impact that the rubber bellows limiting structure will experience in actual working conditions. The more fatigue impacts it withstands, the longer its fatigue life. The impact acceleration mechanism 7 drives the rubber bellows limiting structure... The faster the structure rotates, the greater the impact force between the impact component 8 and the threaded connecting rod, and the more significant the fatigue impact effect. When one of the sprockets 72 rotates, the speed indicator block 75 fixed on its outer wall will rotate synchronously with the sprocket 72 and repeatedly pass through the detection end of the speed sensor 74. The speed sensor 74 adopts a photoelectric sensing design, and its detection end has a built-in light source emitter and a photosensitive receiver. When the speed indicator block 75 rotates past the detection end, it will block the light source, causing the photosensitive receiver to generate an electrical pulse signal. The PLC controller 16 calculates the real-time speed of the sprocket 72 by counting the number of pulse signals received per unit time and combining it with the number of speed indicator blocks 75 (one speed indicator block 75 for each sprocket 72). Since the sprocket 72 rotates synchronously with the second rotating metal block 11, the first rotating metal block 10, and the rubber bellows limiting structure, the speed of the sprocket 72 is equal to the rotation speed of the rubber bellows limiting structure.

[0056] If the rotational speed detected by the speed sensor 74 reaches the speed corresponding to the "maximum impact value" preset by the PLC controller 16, the PLC controller 16 will control the servo motor 71 to maintain the speed continuously. At the same time, the PLC controller 16 will provide real-time feedback on the cumulative number of fatigue impacts (i.e., fatigue life data) on the display control panel 91 based on "real-time rotational speed × number of threaded connecting rods of the rubber bellows limit structure". This design realizes dual-sample synchronous testing, which greatly shortens the time of multi-sample testing and significantly improves the detection efficiency of fatigue testing.

[0057] In the initial stage of the fatigue test of the rubber bellows limiting structure, the PLC controller 16 simultaneously starts the temperature simulation mechanism 4, the corrosion environment simulation mechanism 5 and the lateral load simulation mechanism 6 to construct a composite test environment that closely resembles the actual working conditions.

[0058] When the temperature simulation mechanism 4 is working, the PLC controller 16 controls the temperature fluctuations inside the thermal insulation test chamber 2 according to a preset cycle (e.g., 30 minutes per cycle: 10 minutes for high temperature environment, 10 minutes for low temperature environment, and 10 minutes for temperature change transition). The control panel 91 displays preset high temperature thresholds (e.g., 65℃) and low temperature thresholds (e.g., 5℃). The temperature sensor 94 monitors the temperature inside the thermal insulation test chamber 2 in real time, converting the temperature data into electrical signals and sending them to the PLC controller 16.

[0059] When heating is required, the PLC controller 16 starts the electric heating tube 45, which dissipates heat evenly through the metal mesh plate 44. The heat-resistant circulating fan 47 sends hot air into the heat-conducting and corrosion-resistant coil 14, where it exchanges heat with the brine layer 54 in the base 1, thus raising the temperature of the brine.

[0060] When cooling is required, the PLC controller 16 starts the semiconductor cooler 43, which conducts the cooling through the metal plate 42, and works with the heat-resistant circulating fan 47 to send cold air into the heat-conducting and corrosion-resistant coil 14 to reduce the temperature of the brine.

[0061] After being heated or cooled, the brine is transported through the insulated conveying pipe 57 and the insulated hollow block 59, and then atomized and sprayed into the heat insulation test chamber 2 through the ceramic insulated atomizing nozzle 510. Due to the synergistic heat preservation effect of the insulated conveying pipe 57, the insulated hollow block 59 and the ceramic insulated atomizing nozzle 510, the temperature loss caused by the heat absorption of the brine during transport and atomization evaporation can be reduced. At the same time, the PLC controller 16 dynamically adjusts the power of the electric heating tube 45, the start and stop of the semiconductor cooler 43 and the wind speed of the heat-resistant circulating fan 47 according to the real-time feedback of the temperature sensor 94, so as to ensure that the temperature of the atomized salt spray deviates from the preset temperature by ≤±2℃, thereby achieving precise temperature control and periodic large fluctuations. Combined with the impact acceleration mechanism 7 and the impact component 8, it ensures that the fatigue life test conforms to the actual working conditions of temperature fluctuations.

[0062] When the lateral load simulation mechanism 6 is working, the PLC controller 16 controls the moving ends of the two second electric push rods 62 to slowly extend and retract within a set period (e.g., 30 minutes), pushing the third rotating metal block 12 and the fourth rotating metal block 13 to move, and respectively driving the two rubber bellows limiting structures to generate radial displacement. The pressure sensor 63 installed on the moving end of the second electric push rod 62 will detect the lateral load applied to the rubber bellows limiting structure in real time, convert the pressure data into an electrical signal and send it to the PLC controller 16. Before the test, the staff preset the lateral load threshold (corresponding to the maximum extrusion load under actual working conditions) in the PLC controller 16 according to the actual use scenario of the rubber bellows limiting structure. If the load detected by the pressure sensor 63 exceeds the threshold, the PLC controller 16 immediately controls the moving end of the second electric push rod 62 to extend and retract in the opposite direction, forming a cyclical lateral load action. This simulation not only restores the displacement change caused by the lateral load in actual working conditions, but also enables the impact component 8 to impact different positions of the threaded connecting rod, accurately simulating the real scenario of uncertain fatigue impact position, and further improving the accuracy of fatigue life test.

[0063] When the corrosion environment simulation mechanism 5 is working, the staff prepares a salt solution of corresponding concentration (such as 5% NaCl solution suitable for marine environment) according to the corrosion rate of the metal material of the rubber corrugated pipe limiting structure in the natural environment. The staff then presets the salt spray concentration threshold in the heat insulation test chamber 2 to the PLC controller 16 through the display control panel 91. Subsequently, the PLC controller 16 controls the moving end of the first electric push rod 52 to perform a telescopic movement. When the first electric push rod 52 extends, it pushes the piston 53 to squeeze the salt water layer 54 in the base 1. The salt water passes through the liquid inlet one-way valve 58, the heat insulation delivery pipe 57, and the heat insulation hollow block 59, and is atomized by multiple ceramic heat insulation atomizing nozzles 510 before being sprayed into the heat insulation test chamber 2. The salt water mist forms electrochemical corrosion on the surface of the metal limiting structure, simulating the corrosion process in the actual environment.

[0064] When the first electric push rod 52 retracts, a negative pressure is formed inside the base 1, which draws the brine accumulated at the bottom of the heat insulation test chamber 2 through the return liquid check valve 55. At the same time, the brine is filtered by the filter block 56 to remove large particles of impurities, avoiding clogging of the ceramic heat insulation atomizing nozzle 510 and realizing the recycling of brine. The salt spray concentration sensor 93 detects the salt spray concentration inside the heat insulation test chamber 2 in real time and feeds the data back to the PLC controller 16. If the concentration exceeds the preset threshold, the PLC controller 16 immediately stops the operation of the first electric push rod 52 until the salt spray concentration drops below the threshold and then resumes operation. This design accurately simulates the natural corrosion environment. Combined with fatigue impact testing, it ensures that the test results can reflect the impact of corrosion on the fatigue life of the limiting structure.

[0065] Throughout the fatigue life test, two electronic ohmmeters 95 monitor the resistance values ​​at both ends of the corresponding rubber bellows limiting structure in real time. The two measuring terminals of one electronic ohmmeter 95 form a detection circuit through the first rotating metal block 10 and its outer first metal bearing 3, metal flange 17, rubber bellows limiting structure, another metal flange 17, third rotating metal block 12 and its outer second metal bearing 64 to measure the resistance of the first rubber bellows limiting structure sample.

[0066] Another electronic ohmmeter 95 forms a detection loop through the second rotating metal block 11 and its outer first metal bearing 3, metal flange 17, rubber bellows limiting structure, another metal flange 17, fourth rotating metal block 13 and its outer second metal bearing 64, to measure the resistance of the second rubber bellows limiting structure sample. The electronic ohmmeter 95 converts the resistance data into an electrical signal and sends it to the PLC controller 16. The PLC controller 16 compares the current resistance value with the initial calibration resistance value before the test starts (resistance value under no-damage condition) in real time.

[0067] If the resistance value does not change significantly (change rate < 30%), it indicates that the rubber bellows limiting structure has not suffered fatigue damage such as breakage, and the test can continue.

[0068] If the resistance value increases significantly (e.g., a rubber bellows limiting structure has three threaded connecting rods, and after one of them breaks, the conductive cross-sectional area decreases by about 33%, corresponding to a resistance value increase of more than 30%), it is determined that the sample has experienced its first fatigue failure (at least one threaded connecting rod breaks). The PLC controller 16 immediately controls the alarm 92 to sound an alarm, and at the same time stores the cumulative number of fatigue impacts (i.e., failure life) of the sample on the display control panel 91.

[0069] If the resistance change rate of the same sample exceeds 30% again (i.e. multiple threaded connecting rods break), the PLC controller 16 will only update the failure data of that sample (such as the cumulative number of broken connecting rods and the final resistance value), and will not trigger the alarm 92 again, and the test mechanism will continue to operate.

[0070] The PLC controller 16 will only stop all mechanisms from working and store the failure life data of the second rubber bellows limit structure sample until the resistance change rate of another group of samples is ≥30% for the first time (the second group of samples fails for the first time), or the test reaches the maximum number of cycles preset by the control panel 91 (to prevent the test from going on indefinitely because the sample has not failed for a long time).

[0071] After completing the tests of all samples according to the above procedure, the PLC controller 16 automatically calculates the average cumulative number of fatigue impacts of all valid samples (samples without equipment failure interference), and finally outputs the accurate fatigue life of the rubber bellows limit structure. This design achieves automatic failure determination through real-time resistance monitoring without manual intervention, which not only improves the convenience of the test, but also ensures the objectivity and accuracy of the data.

[0072] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A kind of rubber bellows limit structure fatigue life accelerated test device, including base (1) and heat insulation test box (2), it is characterized in that, The bottom end of the heat insulation test chamber (2) is fixedly connected to the upper surface of the base (1). Two fixed through holes are opened on one side of the outer wall of the heat insulation test chamber (2), and the hole wall of the fixed through hole is fixedly connected to a first metal bearing (3). The inner walls of the two first metal bearings (3) are respectively fixedly connected to a first rotating metal block (10) and a second rotating metal block (11). Two movable through holes are opened on the outer wall of the other side of the heat insulation test chamber (2) at the location symmetrical to the first metal bearing (3), and the hole walls of the two movable through holes are movably connected to a third rotating metal block (12) and a fourth rotating metal block (13). The inner wall of the base (1) is fixedly connected to a corrosion environment simulation mechanism (5); The outer wall of the thermal insulation test chamber (2) is fixedly connected to a transverse load simulation mechanism (6); The side wall of the base (1) is fixedly embedded with multiple thermally conductive and corrosion-resistant coils (14), and the two ends of the multiple thermally conductive and corrosion-resistant coils (14) are jointly fixedly sleeved with a temperature simulation mechanism (4). The upper surface of the base (1) is fixedly connected to a U-shaped plate (15) and a PLC controller (16), and the upper surface of the U-shaped plate (15) is fixedly connected to an impact acceleration mechanism (7). An automated control mechanism (9) is fixedly connected to the outer wall of the U-shaped plate (15). The first rotating metal block (10), the second rotating metal block (11), the third rotating metal block (12) and the fourth rotating metal block (13) are all fixedly fitted with metal flanges (17) on the side walls inside the heat insulation test chamber (2). The transverse load simulation mechanism (6) includes a U-shaped frame (61) fixedly connected to the outer wall of the heat insulation test chamber (2). Two second electric push rods (62) are embedded through the vertical part of the U-shaped frame (61). A pressure sensor (63) is fixedly connected to the moving end of the second electric push rod (62). A second metal bearing (64) is fixedly sleeved on the outer wall of the fixed end of the pressure sensor (63). The inner walls of the two second metal bearings (64) are fixedly connected to the outer walls of the third rotating metal block (12) and the fourth rotating metal block (13) respectively through connecting blocks. The impact acceleration mechanism (7) includes a servo motor (71) fixedly connected to the upper surface of the U-shaped plate (15). The driving end of the servo motor (71) is fixedly connected to the center of the side end of the second rotating metal block (11). The outer walls of the first rotating metal block (10) and the second rotating metal block (11) are both fixedly fitted with sprockets (72). The outer walls of the two sprockets (72) are jointly fitted with a transmission chain (73). The side wall of the U-shaped plate (15) is fixedly embedded with a speed sensor (74). The outer wall of one of the sprockets (72) is fixedly connected with a speed indicator block (75) that cooperates with the speed sensor (74). The inner wall of the heat insulation test chamber (2) is fixedly connected with a crossbar (76). The outer wall of the crossbar (76) is fixedly connected with two symmetrically distributed impact components (8).

2. The apparatus for accelerated fatigue life test of a rubber bellows position-limiting structure according to claim 1, characterized in that, The corrosion environment simulation mechanism (5) includes a partition (51) fixedly connected to the inner wall of the base (1). The outer wall of the partition (51) is provided with a fixing hole, and a first electric push rod (52) is fixedly connected to the wall of the fixing hole. The moving end of the first electric push rod (52) is fixedly connected to a piston (53) that is sealed and slidably connected to the inner wall of the base (1). The interior of the base (1) is filled with a brine layer (54). A return liquid check valve (55) is fixedly embedded on the upper surface of the base (1) located inside the heat insulation test chamber (2). (55) has a filter core block (56) fixedly connected to its inlet end. The upper surface of the base (1) is fixedly embedded with a heat-insulating conveying pipe (57). The bottom end of the heat-insulating conveying pipe (57) is located inside the brine layer (54) and is fixedly connected to an inlet check valve (58). The top end of the heat-insulating conveying pipe (57) is fixedly connected to a heat-insulating hollow block (59). The bottom end of the heat-insulating hollow block (59) is embedded through the top of the heat-insulating test chamber (2). The bottom end of the heat-insulating hollow block (59) is fixedly connected to multiple ceramic heat-insulating atomizing nozzles (510).

3. The apparatus for accelerated fatigue life test of a rubber bellows position-limiting structure according to claim 2, characterized in that, The temperature simulation mechanism (4) includes a heat insulation box (41) that is fixedly sleeved on both sides of multiple thermally conductive and corrosion-resistant coils (14). A metal plate (42) is fixedly embedded at the top of the heat insulation box (41). Multiple semiconductor coolers (43) are fixedly connected to the upper surface of the metal plate (42). Multiple metal mesh plates (44) are fixedly connected to the lower surface of the metal plate (42). Multiple electric heating tubes (45) are fixedly embedded in the side wall of the heat insulation box (41). The heating end of the electric heating tube (45) passes through multiple metal mesh plates (44). An installation plate (46) is fixedly connected to the inner wall of the heat insulation box (41). An installation hole is opened on the upper surface of the installation plate (46), and a heat-resistant circulating fan (47) is fixedly connected to the wall of the installation hole.

4. The accelerated testing device for fatigue life of a rubber bellows limiting structure according to claim 3, characterized in that, The impact assembly (8) includes a rubber sleeve (81) and a return spring (82) fixedly connected to the outer wall of the crossbar (76), and the top ends of the rubber sleeve (81) and the return spring (82) are fixedly connected to an impact metal cover (83).

5. The apparatus for accelerated fatigue life test of a rubber bellows position-limiting structure according to claim 4, characterized in that, The automated control mechanism (9) includes a display control panel (91) and an alarm (92) fixedly connected to the outer wall of the U-shaped plate (15). The side wall of the heat insulation test chamber (2) has two through holes, and the walls of the two through holes are fixedly connected to a salt spray concentration sensor (93) and a temperature sensor (94). The outer wall of the U-shaped frame (61) is fixedly connected to two electronic ohmmeters (95). The two resistance terminals of one of the electronic ohmmeters (95) are fixedly connected to the outer wall of the first metal bearing (3) located at the first rotating metal block (10) and the outer wall of the second metal bearing (64) located at the third rotating metal block (12), respectively. The two resistance terminals of the other electronic ohmmeter (95) are fixedly connected to the outer wall of the first metal bearing (3) located at the second rotating metal block (11) and the outer wall of the second metal bearing (64) located at the fourth rotating metal block (13), respectively.

6. A method of applying an accelerated test device for fatigue life of the rubber bellows position-limiting structure according to claim 5, characterized by, The method includes the following steps: S1. Test preparation: Select a sample of a defect-free rubber corrugated pipe limiting structure and fix it to two sets of metal flanges (17) in the heat insulation test chamber (2) with stainless steel bolts. One set is connected to the first rotating metal block (10) and the third rotating metal block (12), and the other set is connected to the second rotating metal block (11) and the fourth rotating metal block (13). Inject a salt solution of a preset concentration into the base (1) to form a salt solution layer (54). Input the test parameters to the PLC controller (16) through the display control panel (91), calibrate the zero position of each sensor, and then close the door of the heat insulation test chamber (2). S2, Composite Environment and Fatigue Impact Start-up: PLC controller (16) synchronously starts impact acceleration mechanism (7), temperature simulation mechanism (4), corrosion environment simulation mechanism (5) and lateral load simulation mechanism (6). Impact acceleration mechanism (7) drives two sets of samples to rotate synchronously. Speed ​​sensor (74) cooperates with speed indicator block (75) to monitor speed and maintain stability. PLC controller (16) provides real-time feedback on the cumulative number of fatigue impacts. Each simulation mechanism constructs a composite environment according to preset parameters. Among them, temperature simulation mechanism (4) adjusts the temperature of brine layer (54) through heat-conducting corrosion-resistant coil (14). After heating or cooling, brine is transported through heat-insulated conveying pipe (57) and heat-insulated hollow block (59) and atomized and sprayed by ceramic heat-insulated atomizing nozzle (510). Through heat insulation components and PLC controller (16) to dynamically adjust the power of electric heating tube (45), semiconductor cooler (43) and wind speed of heat-resistant circulating fan (47), the temperature of salt spray after atomization is ensured to be ≤±2℃ from the preset temperature. S3. Real-time monitoring and data acquisition: The electronic ohmmeter (95) monitors the resistance values ​​of the two sets of samples in real time. The temperature sensor (94), salt spray concentration sensor (93), and pressure sensor (63) collect environmental and load data synchronously. All data are fed back to the PLC controller (16) in real time and stored. The speed sensor (74) continuously monitors the speed and dynamically compensates. S4. Failure judgment and data storage: The PLC controller (16) compares the current resistance value of the sample with the initial calibration resistance value before the test starts in real time. If the resistance change rate of a sample exceeds 30%, it is judged as the first fatigue failure. The alarm (92) is immediately controlled to alarm and the failure data of the sample is stored. If the resistance change rate of the same sample exceeds 30% again, only the failure data is updated and the alarm is not repeated. The unfailed samples continue to be tested until another set of samples reaches the failure threshold for the first time or the test reaches the preset maximum number of cycles. The PLC controller (16) then controls all mechanisms to stop working and stores the data of the second set of samples. S5. Sample rotation and repeated testing: Remove the failed sample, clean the connection surface of the heat insulation test chamber (2) and the metal flange (17), replace the two new sets of parallel samples, repeat steps S1-S4 until all samples have completed the test. If equipment failure occurs, the PLC controller (16) will pause the test and record the data. The test will continue after the failure is resolved. S6. Data processing and result output: The PLC controller (16) removes abnormal data, calculates the average cumulative fatigue impact number of valid samples, generates a test report containing sample information, test parameters, failure data and environmental curves, and exports or prints it through the display control panel (91). S7. Test completion: Empty the salt water layer (54) inside the base (1), rinse the salt water circulation system, clean the heat insulation test chamber (2) and the surface of each mechanism, reset all mechanisms to the initial state, and turn off the power to complete the test.

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