Hydraulic oil closed-loop adjusting system and method of ultralow-frequency cyclic load creep testing machine

Abstract

The invention discloses a hydraulic oil closed-loop adjusting system and method for an ultralow-frequency cyclic load creep testing machine, and the system comprises a cyclic load generator, an angle sensor, a hydraulic oil adjusting module, a triaxial pressure chamber and a controller, and the cyclic load generator comprises an oil cylinder and a force transmission lever connected with the oil cylinder through a fulcrum; the force transfer lever rotates around a fulcrum when the hydraulic oil quantity in the oil cylinder changes; the angle sensor is arranged on the force transmission lever and used for monitoring the rotation angle of the force transmission lever in real time and generating an angle signal. The hydraulic oil adjusting module is connected with the oil cylinder through an oil way and used for supplementing hydraulic oil to the oil cylinder or discharging hydraulic oil from the oil cylinder. The triaxial pressure chamber is connected with an oil cylinder of the cyclic load generator through an oil conveying pipeline; the controller is in signal connection with the angle sensor and the hydraulic oil adjusting module; according to the application, the oil quantity of the hydraulic oil in the cyclic load generator is continuously monitored, adjustment can be carried out according to the monitoring result, and pressure fluctuation in the triaxial chamber in the adjustment process is avoided.

Description

Technical Field

[0001] This application relates to the field of ultra-low frequency cyclic load creep testing technology, and in particular to a hydraulic oil closed-loop adjustment system and method for an ultra-low frequency cyclic load creep testing machine. Background Technology

[0002] Salt rock, due to its low permeability, good creep properties, and self-healing characteristics, is widely used in energy storage, such as underground natural gas storage facilities. During the operation of such storage facilities, the surrounding rock of the cavity will be subjected to ultra-low frequency cyclic loading caused by the gas injection and production cycle over a long period. To assess its long-term stability, corresponding ultra-low frequency cyclic loading creep tests need to be conducted on salt rock samples in the laboratory.

[0003] Currently, traditional electro-hydraulic servo creep testing machines face significant challenges when conducting such long-term tests: insufficient system reliability, and sudden load changes due to component failures, program errors, or power outages can lead to costly test failures. While gravity loading testing machines based on levers and weights offer high reliability, they typically only apply constant loads or multi-stage step loads, making it difficult to simulate continuously changing cyclic loads and impossible to simulate triaxial stress states.

[0004] To address the aforementioned issues, gravity-driven hydraulic loading testing machines (as shown in patent ZL202311263545.7) have emerged. These machines use gravity to drive hydraulic oil, applying continuously varying loads to samples within a triaxial pressure chamber. However, the core component of this equipment, the cyclic load generator, is designed with a small cylinder and limited oil capacity for pressure amplification. During cyclic loading, the hydraulic oil needs frequent exchange between the cyclic load generator and the triaxial chamber, and the small cylinder's oil capacity is insufficient to sustain prolonged cyclic testing. When the cylinder's oil is depleted or full, load control fails. Currently, the solution to this problem relies on constant manual monitoring and oil replenishment or drainage, which is not only extremely labor-intensive but also requires connecting an external oil circuit to a high-pressure system, inevitably causing pressure fluctuations and severely interfering with the accuracy of the test data.

[0005] Therefore, there is an urgent need to develop a system that can automatically and in a closed loop adjust the oil volume without affecting the stability of the test main circuit pressure during the adjustment process. Summary of the Invention

[0006] To address the aforementioned problems, this application provides a closed-loop hydraulic oil regulation system and method for an ultra-low frequency cyclic load creep testing machine. This system enables continuous monitoring of the hydraulic oil quantity in the cyclic load generator and allows for adjustment based on the monitoring results. Furthermore, the system design allows for hydraulic oil regulation to prevent pressure fluctuations within the triaxial chamber during the adjustment process. The technical solution is as follows: This application provides a closed-loop hydraulic oil regulation system for an ultra-low frequency cyclic loading creep testing machine, comprising a cyclic load generator, an angle sensor, a hydraulic oil regulation module, a triaxial pressure chamber, and a controller. The cyclic load generator includes a cylinder and a force transmission lever connected to the cylinder via a fulcrum. The force transmission lever is configured to rotate around the fulcrum when the hydraulic oil volume in the cylinder changes. The angle sensor is mounted on the force transmission lever to monitor the rotation angle of the force transmission lever in real time and generate an angle signal. The hydraulic oil regulation module is connected to the cylinder of the cyclic load generator via an oil circuit to replenish or discharge hydraulic oil from the cylinder. The triaxial pressure chamber is connected to the... The cyclic load generator is connected to a hydraulic cylinder, and a first pneumatic valve is installed on the oil supply line. The controller is signal-connected to the angle sensor and the hydraulic oil adjustment module. The controller is used to: receive the angle signal; determine whether the hydraulic oil volume in the hydraulic cylinder exceeds a preset range based on the angle signal; when it is determined that adjustment is needed, control the first pneumatic valve to close to disconnect the oil circuit between the cyclic load generator and the triaxial pressure chamber; control the hydraulic oil adjustment module to perform oil replenishment or oil discharge operations until the angle signal indicates that the force transmission lever has returned to the vicinity of the equilibrium position; control the first pneumatic valve to open to reconnect the oil circuit between the cyclic load generator and the triaxial pressure chamber.

[0007] For example, in the hydraulic oil closed-loop regulation system of the ultra-low frequency cyclic load creep testing machine provided in one embodiment, the hydraulic oil regulation module includes a constant flow pump and an oil tank. The oil outlet of the constant flow pump is connected to the oil cylinder of the cyclic load generator through a replenishment pipeline, and a second pneumatic valve is provided on the replenishment pipeline. The oil tank is connected to the oil inlet of the constant flow pump. The controller is signal-connected to the constant flow pump and is used to: control the second pneumatic valve to open and start the constant flow pump to replenish oil when oil replenishment is required; and use the pressure in the oil cylinder to discharge excess hydraulic oil to the oil tank through the discharge pipeline, and a third pneumatic valve is provided on the discharge pipeline.

[0008] For example, in the hydraulic oil closed-loop regulation system of the ultra-low frequency cyclic load creep testing machine provided in one embodiment, one end of the oil discharge pipeline is connected to the oil cylinder of the cyclic load generator, and the other end is connected to the oil storage tank.

[0009] For example, in the hydraulic oil closed-loop regulating system of the ultra-low frequency cyclic load creep testing machine provided in one embodiment, the constant flow pump is a dual-cylinder constant flow pump.

[0010] For example, in the hydraulic oil closed-loop regulation system of the ultra-low frequency cyclic load creep testing machine provided in one embodiment, the system further includes an air circuit control module. The air circuit control module includes an air compressor and multiple solenoid valves. The multiple solenoid valves are connected to the air compressor through an air supply pipeline. The control terminals of the first pneumatic valve, the second pneumatic valve, and the third pneumatic valve are respectively connected to their corresponding solenoid valves through the air supply pipeline. The controller is signal-connected to the multiple solenoid valves and controls the opening and closing of the corresponding pneumatic valves by controlling the on / off state of each solenoid valve.

[0011] For example, in the hydraulic oil closed-loop regulation system of the ultra-low frequency cyclic load creep testing machine provided in one embodiment, the plurality of solenoid valves are integrated and installed in a solenoid valve manifold.

[0012] For example, in the hydraulic oil closed-loop regulation system of the ultra-low frequency cyclic load creep testing machine provided in one embodiment, the controller is further configured to: after controlling the hydraulic oil regulation module to perform oil replenishment or oil discharge operations, delay for a preset time before controlling the first pneumatic valve to open.

[0013] For example, in the hydraulic oil closed-loop regulation system of the ultra-low frequency cyclic load creep testing machine provided in one embodiment, the preset range is an angle interval defined by a positive angle threshold and a negative angle threshold; the controller is used to: determine that oil needs to be added when the angle signal is greater than the positive angle threshold; and determine that oil needs to be drained when the angle signal is less than the negative angle threshold.

[0014] The second aspect of this application provides an ultra-low frequency cyclic load creep testing machine, including the aforementioned hydraulic oil closed-loop regulation system.

[0015] A third aspect of this application provides a closed-loop control method for hydraulic oil in an ultra-low frequency cyclic load creep testing machine. The method uses the aforementioned system and includes the following steps: monitoring the rotation angle of the force transmission lever of the cyclic load generator; determining whether the hydraulic oil volume in the cylinder of the cyclic load generator exceeds a preset range based on the monitored angle; when it is determined that adjustment is required, closing the first pneumatic valve connecting the cyclic load generator and the triaxial pressure chamber; performing oil replenishment or oil discharge operation based on the determination result; monitoring the angle change, stopping the adjustment operation when the angle returns to near the equilibrium position; and reopening the first pneumatic valve after a preset delay.

[0016] The beneficial effects of the hydraulic oil closed-loop regulation system and method for an ultra-low frequency cyclic load creep testing machine provided in some embodiments of this application are as follows: The system achieves fully automatic closed-loop regulation, freeing up manpower. An angle sensor monitors the angle change of the force transmission lever in real time, directly reflecting the oil level in the cylinder of the cyclic load generator. The controller automatically determines whether oil replenishment or drainage is needed based on the angle signal and controls the constant flow pump and pneumatic valve to perform the corresponding operations. This forms a complete "monitoring-judgment-execution" closed loop, completely replacing the 24 / 7 manual monitoring and operation required, greatly saving labor costs and avoiding human error. To completely eliminate pressure fluctuations during the adjustment process and ensure test accuracy, the controller first closes the first pneumatic valve connected to the triaxial pressure chamber before adjusting the oil volume, physically isolating the adjustment circuit from the main test circuit. Subsequently, all oil replenishment or drainage operations are performed within this isolated subsystem, and any resulting pressure fluctuations are confined within the subsystem and cannot be transmitted to the triaxial chamber. After adjustment, the controller delays for a period of time until the pressure stabilizes before reopening the first pneumatic valve. This process fundamentally eliminates the possibility of fluctuations in the load on the specimen caused by external adjustment operations, ensuring the accuracy and reliability of long-term creep test data. The system forms an internal circulation of hydraulic oil, making it self-sufficient. It uses a constant-flow pump with an oil reservoir as the oil source, and the discharged hydraulic oil is not discarded but recycled back into the reservoir. This means that the reservoir only needs to be filled with oil at the beginning of the test, and the system can achieve self-circulation during the subsequent long test process without the need for additional hydraulic oil replenishment. This reduces material consumption and maintenance work, making it ideal for unattended tests lasting several weeks or months. The system boasts high reliability and is suitable for long-term harsh environments. The core control valves utilize pneumatic valves instead of solenoid valves to switch on and off high-pressure oil circuits, as pneumatic valves offer significantly superior high-pressure resistance compared to solenoid valves. Through an indirect control method—"controller → low-pressure solenoid valve → compressed air → high-pressure pneumatic valve"—precise electrical control is achieved while ensuring long-term operational reliability and lifespan under high-pressure conditions, perfectly meeting the high-pressure, long-term requirements of ultra-low frequency creep testing. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this specification or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the hydraulic oil closed-loop regulation system of the ultra-low frequency cyclic load creep testing machine of this application; Figure 2 This is a schematic diagram of the cyclic load generator structure of this application; Figure 3 This is a schematic diagram of the constant flow pump structure of this application; Figure 4 This is a schematic diagram of the solenoid valve manifold structure of this application; Figure 5 This is a schematic diagram of the triaxial chamber structure of this application. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0020] Unless otherwise defined, the technical or scientific terms used in this disclosure shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” and similar terms used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as “comprising” or “including” mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as “connected” or “linked” are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as “upper,” “lower,” “left,” and “right” are used only to indicate relative positional relationships, and these relative positional relationships may change accordingly when the absolute position of the described objects changes.

[0021] The first aspect of this application provides a closed-loop hydraulic oil regulation system for an ultra-low frequency cyclic load creep testing machine, such as... Figure 1-5As shown, the device includes a cyclic load generator 3, an angle sensor 4, a hydraulic oil regulating module, a triaxial pressure chamber 5, and a controller 1. The cyclic load generator 3 includes a cylinder 304 and a force transmission lever 303 connected to the cylinder 304 via a fulcrum 305. The force transmission lever 303 is configured to rotate around the fulcrum 305 when the amount of hydraulic oil in the cylinder 304 changes. The angle sensor 4 is mounted on the force transmission lever 303 and is used to monitor the rotation angle of the force transmission lever 303 in real time and generate an angle signal. The hydraulic oil regulating module is connected to the cylinder 304 of the cyclic load generator 3 via an oil circuit and is used to replenish or discharge hydraulic oil from the cylinder 304. The triaxial pressure chamber 5 is connected to the cyclic load generator 3 via an oil supply line 10. The generator 3 is connected to the cylinder 304, and a first pneumatic valve 13 is provided on the oil supply line 10. The controller 1 is signal-connected to the angle sensor 4 and the hydraulic oil adjustment module. The controller 1 is used to: receive the angle signal; determine whether the hydraulic oil volume in the cylinder 304 exceeds the preset range based on the angle signal; when it is determined that adjustment is needed, control the first pneumatic valve 13 to close to disconnect the oil circuit between the cyclic load generator 3 and the triaxial pressure chamber 5; control the hydraulic oil adjustment module to perform oil replenishment or oil discharge operations until the angle signal indicates that the force transmission lever 303 returns to the vicinity of the equilibrium position; control the first pneumatic valve 13 to open to reconnect the oil circuit between the cyclic load generator 3 and the triaxial pressure chamber 5.

[0022] An angle sensor 4 is installed on the force transmission lever 303 of the cyclic load generator 3 to detect the angle of the lever 303. When the hydraulic oil content in the cyclic load generator 3 decreases, one end of the weight on the force transmission lever 303 rotates downwards, and one end of the cylinder 304 rotates upwards. When the hydraulic oil content in the cyclic load generator 3 increases, one end of the weight on the force transmission lever 303 rotates upwards, and one end of the cylinder 304 rotates downwards. The angle sensor 4 detects the rotation angle and direction. The angle sensor 4 monitors the angle of the force transmission lever 303 of the cyclic load generator 3 in real time and transmits the monitoring signal to the controller 1.

[0023] The hydraulic oil closed-loop adjustment system of the ultra-low frequency cyclic load creep testing machine of this application monitors the angle of the force transmission lever through an angle sensor, realizing indirect, real-time and non-contact measurement of the hydraulic oil volume in the cyclic load generator; the controller judges and controls the first pneumatic valve to close first and then adjust, ensuring that pressure fluctuations are isolated outside the triaxial pressure chamber during oil replenishment or drainage, thereby ensuring the continuity and stability of the load applied to the specimen during the creep test, solving the core problems of impractical manual adjustment and the influence of pressure fluctuations on test results.

[0024] For example, in the hydraulic oil closed-loop regulation system of the ultra-low frequency cyclic loading creep testing machine provided in one embodiment, such as Figure 1-3 As shown, the hydraulic oil regulating module includes a constant flow pump 2 and an oil storage tank 201. The oil outlet 203 of the constant flow pump 2 is connected to the cylinder 304 of the circulating load generator 3 via an oil replenishment pipeline 9. A second pneumatic valve 12 is provided on the oil replenishment pipeline 9. The oil storage tank 201 is connected to the oil inlet 204 of the constant flow pump 2. The controller 1 is signal-connected to the constant flow pump 2 and is used to: control the second pneumatic valve 12 to open and start the constant flow pump 2 to replenish oil when oil replenishment is required; and use the pressure in the cylinder 304 to discharge excess hydraulic oil to the oil storage tank 201 through the oil discharge pipeline 8 when oil discharge is required. A third pneumatic valve 11 is provided on the oil discharge pipeline 8.

[0025] The constant flow pump 2 can inject hydraulic oil into the circulating load generator 3 at a constant flow rate. The constant flow pump 2 can receive signals from the controller 1. When it is necessary to replenish oil into the circulating load generator 3, the constant flow pump 2 starts working under the control of the controller 1 to replenish oil into the circulating load generator 3. The constant flow pump 2 adopts a dual-cylinder pump, which can ensure stable hydraulic oil output. The uppermost part of the constant flow pump 2 is equipped with an oil tank 201. The oil tank has two functions: (1) The bottom of the oil tank is connected to the pipeline, and the other end of the pipeline is connected to the constant flow pump 2. When the hydraulic oil in the circulating load generator 3 is too low, it is necessary to replenish oil from the constant flow pump 2 into the circulating load generator 3. When the hydraulic oil in the constant flow pump 2 is insufficient, hydraulic oil can be replenished from the oil tank 201. (2) When there is too much hydraulic oil in the circulating load generator 3, it is necessary to discharge the hydraulic oil from the circulating load generator 3. The discharged hydraulic oil can be discharged into the oil tank 201 on the constant flow pump 2. The two processes described above ensure that the hydraulic oil in the constant flow pump 2 and the circulating load generator 3 maintains a dynamic circulation, preventing hydraulic oil from being discharged outside the system and causing losses. Therefore, only an appropriate amount of hydraulic oil needs to be added to the tank before the test begins, and no manual replenishment is required afterwards.

[0026] According to the above embodiments, the application of the constant flow pump ensures constant flow and stable pressure during the oil replenishment process; the oil tank is integrated with the constant flow pump, allowing the hydraulic oil to circulate within the system, avoiding oil loss and achieving long-term unattended automated operation. Oil discharge is achieved using high pressure within the cylinder, eliminating the need for an additional power unit, resulting in energy saving and high efficiency.

[0027] For example, in the hydraulic oil closed-loop regulation system of the ultra-low frequency cyclic loading creep testing machine provided in one embodiment, such as Figure 1-2 As shown, one end of the oil drain line 8 is connected to the oil cylinder 304 of the circulating load generator 3, and the other end is connected to the oil storage tank 201.

[0028] Based on the above embodiments, the oil drain path is clearly defined. Connecting the drain line directly to the oil reservoir forms a complete closed-loop hydraulic oil circuit, ensuring leak-free system operation, maintaining a clean working environment, and further reducing maintenance requirements.

[0029] For example, in the hydraulic oil closed-loop regulating system of the ultra-low frequency cyclic load creep testing machine provided in one embodiment, the constant flow pump 2 is a dual-cylinder constant flow pump.

[0030] According to the above embodiments, the dual-cylinder constant flow pump, as a preferred type of constant flow pump, has the technical advantage of providing an extremely stable, pulsation-free hydraulic oil flow, thereby minimizing the hydraulic shock to the cyclic load generator system during the oil replenishment process.

[0031] For example, in the hydraulic oil closed-loop regulation system of the ultra-low frequency cyclic loading creep testing machine provided in one embodiment, such as Figure 1-4 As shown, the system also includes a pneumatic control module, which includes an air compressor 7 and multiple solenoid valves 601, 602, and 603. The multiple solenoid valves are connected to the air compressor 7 via air supply lines 14, 15, and 16. The control terminals of the first pneumatic valve 13, the second pneumatic valve 12, and the third pneumatic valve 11 are connected to the corresponding solenoid valves 601, 602, and 603 via the air supply lines 14, 15, and 16, respectively. The controller 1 is signal-connected to the multiple solenoid valves and controls the opening and closing of the corresponding pneumatic valves by controlling the on / off state of each solenoid valve.

[0032] The solenoid valve is installed on the gas supply pipeline. Its function is to receive signals from the controller 1 and control the opening and closing of the gas supply pipeline according to the signals. One end of the gas supply pipeline is connected to the air compressor 7, which can output high-pressure gas. The other end of the gas pipeline is connected to the pneumatic valve, which in turn controls the opening and closing of the pneumatic valve.

[0033] The controller 1 in this application has two functions: First, the data monitored by the angle sensor is transmitted to the controller 1 in real time, and the system judges the relationship between the monitored value and the operating threshold. When the threshold to be adjusted is exceeded, the adjustment program is started. Second, the controller 1 is connected to the constant flow pump 2 and the solenoid valve through a signal line, controlling the operation of the constant flow pump 2 and the solenoid valve to ensure that the hydraulic oil adjustment is carried out according to the set program.

[0034] According to the above embodiments, the design of the pneumatic control module solves the control problem of high-pressure oil circuits. Since solenoid valves cannot directly withstand high-pressure hydraulic oil, while pneumatic valves can, this solution uses a controller to control a low-pressure solenoid valve, which in turn controls compressed air to drive the high-pressure pneumatic valve, forming a reliable, low-cost, and safe indirect control solution for the on / off of high-pressure oil circuits.

[0035] For example, in the hydraulic oil closed-loop regulation system of the ultra-low frequency cyclic loading creep testing machine provided in one embodiment, such as Figure 4 As shown, the multiple solenoid valves 601, 602, and 603 are integrated and installed in a solenoid valve manifold 6.

[0036] According to the above embodiments, the solenoid valve is integrated and installed in the housing, which saves installation space, simplifies the air circuit layout, facilitates maintenance and troubleshooting, and improves the overall integrity and reliability of the system.

[0037] For example, in the hydraulic oil closed-loop regulation system of the ultra-low frequency cyclic load creep testing machine provided in one embodiment, the controller 1 is further configured to: after controlling the hydraulic oil regulation module to perform oil replenishment or oil discharge operations, delay for a preset time, and then control the first pneumatic valve 13 to open.

[0038] According to the above embodiments, the delayed opening of the first pneumatic valve has a key effect: it provides a pressure buffer and stabilization period after adjustment, ensuring that the pressure in the cyclic load generator cylinder is balanced with the pressure in the triaxial chamber before connection, completely eliminating the risk of small pressure fluctuations that may exist at the end of adjustment being transmitted to the triaxial chamber, and further ensuring the accuracy of the test.

[0039] For example, in the hydraulic oil closed-loop regulation system of the ultra-low frequency cyclic load creep testing machine provided in one embodiment, the preset range is an angle interval defined by a positive angle threshold and a negative angle threshold; the controller 1 is used to: determine that oil needs to be added when the angle signal is greater than the positive angle threshold; and determine that oil needs to be drained when the angle signal is less than the negative angle threshold.

[0040] According to the above embodiments, positive and negative angle thresholds are used as the basis for judgment. The effect is to set a working range that allows the hydraulic oil to make normal profits and losses, avoiding the system from operating too frequently. This ensures the timeliness of adjustment and improves the stability and service life of the system.

[0041] The hydraulic oil closed-loop regulation system of the ultra-low frequency cyclic loading creep testing machine of this application, when conducting cyclic loading and unloading creep tests, allows the cyclic load generator 3 to change the position of the movable weight 301, causing the hydraulic oil pressure in the cylinder 304 to cyclically change. The cylinder 304 of the cyclic load generator 3 is connected to the hydraulic oil in the axial pressure chamber 501 or confining pressure chamber 502 of the triaxial chamber 5 via a pipeline. The pressure of the hydraulic oil in the axial pressure chamber 501 or confining pressure chamber 502 of the triaxial chamber 5 will also cyclically change synchronously, thereby applying cyclically changing axial pressure or confining pressure to the rock sample 503. Since both the axial pressure and confining pressure in the triaxial chamber 5 are controlled by the same cyclic load generator, the loading and unloading principles of the axial pressure and confining pressure are exactly the same as the hydraulic oil closed-loop regulation principle of the cyclic load generator. For simplicity, this embodiment uses confining pressure for description. Driven by the force transmission lever 303 of the cyclic load generator 3, the hydraulic cylinder 304 can move up and down, thus allowing the hydraulic oil volume within the cylinder 304 to vary within a certain range. During the pressure cycle, the hydraulic oil flows back and forth between the cylinder 304 of the cyclic load generator 3 and the confining pressure chamber 502 of the triaxial chamber 5. When the load increases, the hydraulic oil in the cylinder 304 of the cyclic load generator 3 flows into the confining pressure chamber 502 of the triaxial chamber 5; when the load decreases, the hydraulic oil in the confining pressure chamber 502 of the triaxial chamber 5 flows back into the cylinder 304 of the cyclic load generator 3. Therefore, as long as cyclic loading is applied, the amount of hydraulic oil in the cylinder 304 of the cyclic load generator 3 is constantly changing. To amplify the hydraulic oil pressure within the cyclic load generator, the diameter of the cylinder 304 of the cyclic load generator 3 is designed to be relatively small. Therefore, the amount of hydraulic oil that can be stored in cylinder 304 is insufficient to meet the oil volume required for adjusting the pressure within the triaxial chamber 5. Once all the hydraulic oil in cylinder 304 has flowed into the triaxial chamber 5, even if the movable weight 301 is moved, no more hydraulic oil can flow into the triaxial chamber 5, and the pressure within the triaxial chamber 5 will no longer increase. Similarly, once cylinder 304 is full of hydraulic oil, even if the movable weight 301 is moved, the hydraulic oil in the triaxial chamber 5 cannot flow back into the circulating load generator 3, and the pressure within the triaxial chamber 5 cannot decrease. In other words, when the hydraulic oil in cylinder 304 is depleted or filled, the circulating load generator 3 loses its ability to regulate the confining pressure and axial pressure within the triaxial chamber 5. To solve these problems, it is necessary to adjust the hydraulic oil in cylinder 304 of the circulating load generator 3. When the hydraulic oil in the cyclic load generator 3 is insufficient, oil is added to the cylinder 304 of the cyclic load generator 3 through an external hydraulic oil regulating system. When the hydraulic oil in the cyclic load generator 3 is excessive, the hydraulic oil in the cylinder 304 is discharged through an external hydraulic oil regulating system.

[0042] When the hydraulic oil in cylinder 304 of the cyclic load generator 3 changes, the force transmission lever 303 of the cyclic load generator 3 will rotate at a certain angle around the fulcrum 305. When the hydraulic oil in cylinder 304 decreases, the weight side of the force transmission lever 303 will descend, and the cylinder 304 side will rise; when the hydraulic oil in cylinder 304 increases, the weight side of the force transmission lever 303 will rise, and the cylinder 304 side will descend. Therefore, by installing an angle sensor 4 on the force transmission lever 303 and monitoring the tilt angle of the force transmission lever 303 in real time, the function of real-time monitoring of the hydraulic oil in cylinder 304 of the cyclic load generator 3 can be realized. When the force transmission lever 303 is horizontal, the monitoring value of angle sensor 4 is 0°; when the weight side of the force transmission lever 303 descends and the cylinder 304 side rises, the monitoring value of angle sensor 4 is positive; when the weight side of the force transmission lever 303 ascends and the cylinder 304 side descends, the monitoring value of angle sensor 4 is negative. A threshold value, such as ±2°, for the angle of the force transmission lever 303 is set in controller 1. When the rotation angle of the force transmission lever 303 is within ±2°, the hydraulic oil in the cylinder 304 of the cyclic load generator 3 is not adjusted. When the rotation angle of the force transmission lever 303 is greater than 2°, the hydraulic oil adjustment system replenishes oil to the cyclic load generator 3. When the rotation angle of the force transmission lever 303 is less than -2°, the hydraulic oil adjustment system drains oil from the cyclic load generator 3.

[0043] When the cyclic load generator 3 is working normally and does not require oil replenishment or drainage, the cyclic load generator and the first pneumatic valve 13 are open, and the third pneumatic valve 11 and the second pneumatic valve 12 are closed. When the controller 1 detects that the angle of the angle sensor 4 is greater than 2°, the controller 1 will control the hydraulic oil adjustment system to perform the following operations: (1) By controlling the solenoid valve 601, the cyclic load generator 3 and the first pneumatic valve 13 are closed, cutting off the oil supply line 10 between the cyclic load generator and the triaxial chamber, so as to prevent the pressure fluctuation generated during hydraulic oil adjustment from being transmitted to the triaxial chamber 5. (2) The third pneumatic valve 11 is kept closed, and the second pneumatic valve 12 is opened by controlling the solenoid valve 603. (3) The constant flow pump 2 is turned on, and hydraulic oil is replenished into the cyclic load generator 3 from the constant flow pump 2. (4) Monitor the reading of angle sensor 4 in real time. During the oil replenishment process, the reading of angle sensor 4 gradually decreases from 2°. When the reading of angle sensor 4 is detected to be 0°, control the constant flow pump 2 to shut down and stop replenishing oil into the cyclic load generator 3. At the same time, control the solenoid valve 603 to close the pneumatic valve 12. (5) After the pneumatic valve 12 is closed for 3 seconds, control the solenoid valve 601 to open the cyclic load generator and the first pneumatic valve 13, so that the cyclic load generator and the triaxial chamber oil supply line 10 are reconnected. The 3-second interval is reserved here to allow the pressure in the cylinder 304 of the cyclic load generator 3 to stabilize before connecting the cyclic load generator and the triaxial chamber oil supply line 10, so as to avoid the pressure fluctuation in the cyclic load generator 3 from being transmitted to the triaxial chamber 5.

[0044] When the controller 1 detects that the angle of the angle sensor 4 is less than -2°, the controller 1 will control the hydraulic oil adjustment system to perform the following operations: (1) By controlling the solenoid valve 601, the circulating load generator and the first pneumatic valve 13 are closed, cutting off the oil supply line 10 between the circulating load generator and the triaxial chamber, so as to prevent the pressure fluctuation generated during hydraulic oil adjustment from being transmitted to the triaxial chamber 5. (2) The second pneumatic valve 12 is kept closed, and the third pneumatic valve 11 is opened by controlling the solenoid valve 602. (3) There is high pressure in the hydraulic oil in the cylinder 304 of the circulating load generator 3. Under the action of this pressure, the hydraulic oil is discharged from the cylinder 304 of the circulating load generator 3 and flows into the oil storage tank 201 of the constant flow pump 2 through the oil discharge line 8. (4) The reading of the angle sensor 4 is monitored in real time. During the oil discharge process, the reading of the angle sensor 4 gradually increases from -2°. When the reading of the angle sensor 4 is detected to be 0°, the third pneumatic valve 11 is closed, and the oil discharge from the circulating load generator 3 is stopped. (5) After the pneumatic valve 11 is closed for 3 seconds, the solenoid valve 601 is controlled to open the cyclic load generator and the first pneumatic valve 13, so that the cyclic load generator and the triaxial chamber oil supply line 10 are reconnected. The 3-second interval is reserved here to allow the pressure in the cylinder 304 of the cyclic load generator 3 to stabilize before connecting the cyclic load generator and the triaxial chamber oil supply line 10, so as to avoid pressure fluctuations in the cyclic load generator 3 from being transmitted to the triaxial chamber 5.

[0045] Since the working pressure range of solenoid valves is generally 0.1MPa to 1MPa, while the working pressure of ultra-low frequency cyclic load creep test systems is generally 10MPa to 80MPa, solenoid valves are not suitable for the oil circuit of the test system. The working pressure of pneumatic valves can meet the pressure range of hydraulic oil in the oil circuit of the ultra-low frequency cyclic load creep test system, but the control commands of controller 1 cannot directly control the pneumatic valves. Therefore, this application uses solenoid valves to control the pneumatic valves, thereby achieving control over the opening and closing of the oil circuit of the ultra-low frequency cyclic load creep test system.

[0046] The solutions described in the above embodiments enable real-time monitoring of the hydraulic oil in the ultra-low frequency cyclic loading creep testing machine, and real-time dynamic adjustment of the hydraulic oil based on the monitoring data. This process forms a closed loop of monitoring and adjustment, with fully automated control and no need for manual intervention.

[0047] The hydraulic oil closed-loop regulation system of the ultra-low frequency cyclic loading creep testing machine disclosed in this application can continuously monitor the hydraulic oil level in the cyclic load generator. When adjustment is required, it controls a constant-speed replenishing pump to adjust the hydraulic oil. Once the oil level is detected to be normal, the adjustment action stops. This process achieves closed-loop regulation of the hydraulic oil, which is fully automated and requires no manual intervention, saving labor costs. Through system design, the oil supply line between the cyclic load generator and the triaxial chamber is disconnected during hydraulic oil adjustment, and the oil supply line between the cyclic load generator and the triaxial chamber is opened after adjustment is completed and the oil pressure in the cyclic load generator stabilizes, thus avoiding pressure fluctuations in the triaxial chamber during hydraulic oil adjustment.

[0048] The second aspect of this application provides an ultra-low frequency cyclic load creep testing machine, including the aforementioned hydraulic oil closed-loop regulation system.

[0049] A third aspect of this application provides a closed-loop control method for hydraulic oil in an ultra-low frequency cyclic loading creep testing machine. The method uses the aforementioned system and includes the following steps: The rotation angle of the force transmission lever 303 of the cyclic load generator 3 is monitored in real time by the angle sensor 4. Based on the monitored angle, determine whether the hydraulic oil volume in the cylinder 303 of the cyclic load generator 3 exceeds the preset range; When it is determined that adjustment is needed, close the first pneumatic valve 13 that connects the cyclic load generator 3 and the triaxial pressure chamber 5; Based on the judgment result, control the hydraulic oil regulating module to perform oil replenishment or oil discharge operations; The system monitors angle changes in real time and stops adjusting when the angle returns to near the equilibrium position. After a preset delay, the first pneumatic valve 13 is reopened.

[0050] According to the above embodiments, the advantages of the hardware system are integrated into a set of efficient, reliable, and repeatable operating procedures, which ensures the automation of the experiment and high-precision results.

[0051] Although the embodiments of this application have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for this application. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, this application is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A closed-loop hydraulic oil regulating system for an ultra-low frequency cyclic loading creep testing machine, characterized in that, include: A cyclic load generator includes a hydraulic cylinder and a force transmission lever connected to the hydraulic cylinder via a fulcrum, the force transmission lever being configured to rotate about the fulcrum when the amount of hydraulic oil in the hydraulic cylinder changes. An angle sensor is installed on the force transmission lever to monitor the rotation angle of the force transmission lever in real time and generate an angle signal. The hydraulic oil regulating module is connected to the oil cylinder of the circulating load generator via an oil circuit, and is used to replenish or discharge hydraulic oil from the oil cylinder. The triaxial pressure chamber is connected to the oil cylinder of the cyclic load generator via an oil supply pipeline, and a first pneumatic valve is installed on the oil supply pipeline. The controller, connected to the angle sensor and the hydraulic oil adjustment module, is configured to: receive the angle signal; determine whether the hydraulic oil volume in the cylinder exceeds a preset range based on the angle signal; when adjustment is required, control the first pneumatic valve to close to disconnect the oil circuit between the cyclic load generator and the triaxial pressure chamber; control the hydraulic oil adjustment module to perform oil replenishment or oil discharge operations until the angle signal indicates that the force transmission lever has returned to near the equilibrium position; and control the first pneumatic valve to open to reconnect the oil circuit between the cyclic load generator and the triaxial pressure chamber.

2. The hydraulic oil closed-loop regulation system of the ultra-low frequency cyclic loading creep testing machine according to claim 1, characterized in that, The hydraulic oil regulating module includes: A constant flow pump, the oil outlet of which is connected to the oil cylinder of the circulating load generator through an oil replenishment pipeline, and a second pneumatic valve is provided on the oil replenishment pipeline; An oil reservoir is connected to the oil inlet of the constant flow pump; The controller is connected to the constant flow pump and is used to: control the second pneumatic valve to open and start the constant flow pump to replenish oil when oil needs to be replenished; and use the pressure in the oil cylinder to discharge excess hydraulic oil to the oil storage tank through the oil discharge pipeline when oil needs to be discharged, with a third pneumatic valve provided on the oil discharge pipeline.

3. The hydraulic oil closed-loop regulation system of the ultra-low frequency cyclic loading creep testing machine according to claim 2, characterized in that, One end of the oil drain line is connected to the oil cylinder of the circulating load generator, and the other end is connected to the oil storage tank.

4. The hydraulic oil closed-loop regulation system of the ultra-low frequency cyclic loading creep testing machine according to claim 2, characterized in that, The constant flow pump is a dual-cylinder constant flow pump.

5. The hydraulic oil closed-loop regulation system of the ultra-low frequency cyclic loading creep testing machine according to claim 1, characterized in that, The system also includes a gas path control module, which comprises: Air compressor; Multiple solenoid valves are connected to the air compressor via air supply lines; the control terminals of the first, second, and third pneumatic valves are respectively connected to their corresponding solenoid valves via the air supply lines; the controller is signal-connected to the multiple solenoid valves and controls the opening and closing of the corresponding pneumatic valves by controlling the on / off state of each solenoid valve.

6. The hydraulic oil closed-loop regulating system of the ultra-low frequency cyclic loading creep testing machine according to claim 5, characterized in that, The multiple solenoid valves are integrated and installed in a solenoid valve manifold.

7. The hydraulic oil closed-loop regulation system of the ultra-low frequency cyclic loading creep testing machine according to claim 1, characterized in that, The controller is also used to: after controlling the hydraulic oil regulating module to perform oil replenishment or oil discharge operations, delay for a preset time before controlling the first pneumatic valve to open.

8. The hydraulic oil closed-loop regulation system of the ultra-low frequency cyclic loading creep testing machine according to claim 1, characterized in that, The preset range is an angle interval defined by a positive angle threshold and a negative angle threshold; the controller is used to: determine that oil needs to be added when the angle signal is greater than the positive angle threshold; and determine that oil needs to be drained when the angle signal is less than the negative angle threshold.

9. An ultra-low frequency cyclic loading creep testing machine, characterized in that, Includes the hydraulic oil closed-loop regulating system as described in any one of claims 1 to 8.

10. A closed-loop control method for hydraulic oil in an ultra-low frequency cyclic loading creep testing machine, characterized in that, The method uses the system as described in any one of claims 1 to 8 and includes the following steps: Monitor the rotation angle of the force transmission lever of the cyclic load generator; Based on the monitored angle, determine whether the hydraulic oil volume in the cylinder of the cyclic load generator exceeds the preset range; When it is determined that adjustment is needed, close the first pneumatic valve connecting the cyclic load generator and the triaxial pressure chamber; Based on the assessment results, perform either oil replenishment or oil removal operations; Monitor angle changes and stop adjusting when the angle returns to near the equilibrium position; After a preset delay, the first pneumatic valve is reopened.

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