A stress corrosion loading device and a stress corrosion test method

Abstract

The application discloses a stress corrosion loading device and a stress corrosion test method. The device comprises an environment cavity, a loading execution mechanism, a medium regulation loop, an environment regulation loop, a detection unit and a controller. The loading execution mechanism is used for applying mechanical load to a sample. The medium regulation loop is used for supplying and circulating corrosion medium and adjusting its component parameters. The environment regulation loop is used for adjusting temperature and humidity parameters in the environment cavity. The detection unit is used for acquiring detection values of the component parameters and / or the temperature and humidity parameters in real time. The controller is used for independently controlling the medium regulation loop and the environment regulation loop to act according to deviations of preset target values and the detection values. Each module is combined in a detachable connection mode, and the remaining modules remain complete in structure after any module is detached. The application realizes high-precision independent real-time automatic regulation of multiple environmental parameters such as temperature and pH value, has a full detachable modular structure, and significantly improves test efficiency, equipment reusability and maintenance convenience.

Description

Technical Field

[0001] This invention relates to the field of stress corrosion testing technology, specifically to a stress corrosion loading device and a stress corrosion testing method, which is particularly suitable for evaluating the susceptibility of metallic materials to stress corrosion cracking (SCC) under simulated service environments, and can be widely used in petrochemical, nuclear power, marine engineering, aerospace and other fields. Background Technology

[0002] Stress corrosion cracking (SCC) is a low-stress brittle fracture phenomenon that occurs in metallic materials under the combined action of tensile stress (including working stress, residual stress, or applied stress) and a specific corrosive medium. It is extremely dangerous, often leading to sudden engineering failures, and is widely present in fields such as petrochemicals, marine engineering, nuclear power, aerospace, and high-pressure pipelines. The mechanism of SCC is complex and strongly influenced by the material's microstructure, stress level, and environmental factors. Even small fluctuations in environmental parameters can significantly alter the material's SCC susceptibility threshold, crack initiation, and propagation rates, resulting in poor repeatability of experimental results and difficulty in quantitatively evaluating the material's service performance.

[0003] To accurately simulate real-world service conditions, the SCC performance evaluation of materials requires the simultaneous application of precisely controllable mechanical stress (constant load, constant displacement, or slow strain rate loading) and highly simulated corrosive environmental conditions in the laboratory. Currently, international and domestic standards (such as ASTM G36, G37, G38, G129, GB / T4157, GB / T15970 series, NACETM0177, TM0198, etc.) emphasize the consistency and repeatability of test conditions. However, existing testing technologies still face bottlenecks in achieving a harmonious balance between "precise and reliable stress loading" and "accurate and stable environmental factors."

[0004] The existing stress corrosion loading devices most similar to this invention can be mainly divided into three categories.

[0005] Option 1: Slow Strain Rate Stress Corrosion Testing Machine (SSRT). This option is currently the most commonly used dynamic loading SCC testing technology in laboratories. It mainly consists of a heavy-load frame, an environmental container, a computer control system, and auxiliary circuits. It achieves constant slow rate tensile or constant load creep through stepper motor drive. The environmental container supports high temperature and high pressure conditions from room temperature and pressure to 600℃ and 30MPa. This option has a one-piece rigid structure that is not disassembled, making maintenance and cleaning difficult. It has limited independent high-precision real-time automatic control capability for multiple environmental parameters (such as temperature, pH, dissolved oxygen, and flow rate). The dynamic seal is prone to media leakage or concentration changes during long-term loading. Temperature fluctuations can cause thermal expansion of the loading rod, affecting stress constancy. It is also difficult to achieve independent batch control of multiple samples.

[0006] Option 2: Patent application CN104568729A discloses a corrosion electrolysis cell device suitable for considering the influence of stress gradients. This option designs a series corrosion electrolysis cell structure, forming a connected sealed space through series connection of cylindrical bodies. Different loads are applied independently at both ends of the working electrode to simulate stress gradients, while supporting real-time monitoring and adjustment of temperature, dissolved oxygen, pH, and flow rate. This option is a one-piece electrolysis cell structure that cannot be disassembled and reassembled, making it difficult to adapt to high temperature and high pressure, dynamic fluid, or multi-media coupling conditions. The loading accuracy is easily affected by temperature fluctuations, the sealing reliability is insufficient under long-term stress, and it lacks the ability to automatically control batch multi-sample operations.

[0007] Option 3: Patent application CN206177710U discloses a device for testing the stress corrosion behavior of metallic materials under high pressure in a fluid. This option places the entire constant load loading assembly inside the autoclave, avoiding the sealing problem of external stress transmission. An adjustable constant tensile stress is applied to the sample through a compression spring, while also supporting in-situ electrochemical testing. However, this option relies on an external autoclave auxiliary system for precise and independent control of environmental factors (such as temperature, dissolved oxygen, pH, and flow rate), making it difficult to achieve high-precision real-time automatic and stable control at the ppm level. The medium concentration is prone to change during long-term testing, and the loading accuracy is affected by fluctuations in temperature / pressure inside the autoclave. Furthermore, the entire device is an integrated autoclave structure that cannot be disassembled or modularized, making operation complex and difficult to expand to batch multi-sample or complex loading modes (such as slow strain rates), resulting in poor adaptability.

[0008] In summary, the existing technical solutions all have the following main drawbacks: (1) Low precision and poor stability of environmental factor control. It is difficult to achieve independent and high-precision real-time control of parameters such as temperature, pH value, and dissolved oxygen concentration. Even small fluctuations will lead to poor repeatability of test results; (2) Difficulty in sealing and maintaining the medium. During the loading process, medium leakage, concentration drift or composition change are likely to occur, especially under high temperature and high pressure, sealing failure occurs frequently; (3) Insufficient loading precision and stability. Problems such as thermal expansion and creep of the loading rod make it difficult to maintain constant stress / constant strain; (4) Poor structural adaptability and non-disassembly. It is impossible to quickly disassemble, clean, maintain or reassemble, and its ability to adapt to different working conditions is weak; (5) Inconvenient safety and maintenance. Insufficient safety protection against toxic and corrosive media. Disassembly and cleaning are difficult.

[0009] Therefore, there is an urgent need for a stress corrosion loading device that allows for precise control of environmental factors and is detachable and modular, in order to overcome the aforementioned shortcomings of existing technologies. Summary of the Invention

[0010] This invention provides a stress corrosion loading device and a stress corrosion testing method, aiming to overcome the shortcomings of existing technologies such as low accuracy of environmental factor control, poor sealing reliability, non-removable structure, and weak adaptability to working conditions.

[0011] To achieve the above objectives, the present invention adopts the following technical solution: A stress corrosion loading device includes: a support frame; an environmental cavity disposed on the support frame for containing a corrosive medium and providing a corrosion environment for a sample; a loading actuator acting on the sample within the environmental cavity to apply a mechanical load to the sample; a medium control circuit connected to the environmental cavity for supplying and circulating the corrosive medium into the environmental cavity and adjusting the composition parameters of the corrosive medium; an environmental control circuit connected to the environmental cavity for adjusting the temperature and humidity parameters within the environmental cavity; a detection unit disposed in the medium control circuit and / or the environmental cavity for acquiring the detection values ​​of the composition parameters and / or the temperature and humidity parameters in real time; and a controller connected to the detection unit, the medium control circuit, and the environmental control circuit, for independently controlling the operation of the medium control circuit and the environmental control circuit based on the deviation between a preset target value and the detection value; the environmental cavity, the loading actuator, the functional components in the medium control circuit, and the functional components in the environmental control circuit all adopt a detachable modular structure, with each module combined through a detachable connection, and the remaining modules maintaining structural integrity after any module is disassembled.

[0012] Furthermore, the loading actuator includes a loading frame and a loading drive component, and the sample is fixed to the loading frame by a clamping assembly; the device also includes a rotation drive module, which is connected to the loading frame for driving the sample to rotate relative to the environmental cavity; the mechanical load applied to the sample by the loading drive component is independent of the rotational motion of the rotation drive module.

[0013] Furthermore, a detachable dynamic sealing assembly is provided between the environmental cavity and the force transmission component of the loading actuator. The dynamic sealing assembly is used to adaptively compensate for the sealing gap between the force transmission component and the environmental cavity when the force transmission component moves.

[0014] Furthermore, the media control loop includes a corrosive media preparation unit, a liquid supply unit, and a liquid return treatment unit; the corrosive media preparation unit is used to prepare corrosive media according to set parameters; the liquid supply unit is connected to the environmental cavity and is used to transport the prepared corrosive media into the environmental cavity; the liquid return treatment unit is connected to the environmental cavity and is used to collect and treat the corrosive media discharged from the environmental cavity, and return the treated corrosive media to the liquid supply unit or the corrosive media preparation unit, forming a closed-loop circulation loop for the corrosive media.

[0015] Furthermore, the corrosive medium preparation unit includes multiple liquid storage containers and a quantitative supply device connected to each of the liquid storage containers. The controller controls each of the quantitative supply devices to take liquid in a proportional manner and mix them according to the set parameters in order to prepare a corrosive medium with the target components.

[0016] Furthermore, the loading actuator includes an electric loading structure, a pneumatic loading structure, a hydraulic loading structure, or a weight lever loading structure, used to apply mechanical loads in the form of constant load, constant displacement, or slow strain rate to the sample.

[0017] Furthermore, the environmental control loop includes at least one of a temperature control unit, a humidity control unit, and an airflow circulation unit; the temperature control unit is used to regulate the temperature inside the environmental cavity; the humidity control unit is used to regulate the humidity inside the environmental cavity; and the airflow circulation unit is used to generate a circulating airflow inside the environmental cavity.

[0018] Furthermore, the controller includes a parameter setting unit, a comparison unit, and an instruction output unit; the parameter setting unit is used to set target environmental parameters and target medium parameters; the comparison unit is used to compare the real-time detection value of the detection unit with the target environmental parameters or the target medium parameters to obtain a deviation signal; the instruction output unit is used to output adjustment instructions to the corresponding execution components according to the deviation signal.

[0019] Furthermore, the detection unit includes at least one of a temperature sensor, a humidity sensor, a pH sensor, a concentration sensor, and a conductivity sensor.

[0020] The present invention also provides a stress corrosion testing method, which uses the above-mentioned stress corrosion loading device to conduct the test, and includes the following steps: S1: The test sample is mounted on the loading actuator and a predetermined mechanical load is applied to the sample to obtain the loaded sample; S2: Using the sample loaded in step S1, a target corrosive medium with set parameters is supplied to the environmental cavity through the medium control circuit, so that the sample is in the target corrosive medium environment. S3: Based on step S2, adjust the environmental parameters within the environmental cavity to a set range through the environmental control loop; S4: During step S3, the detection unit detects the environmental parameters and / or the parameters of the corrosive medium in the environmental cavity in real time, obtains the real-time detection value, and transmits the real-time detection value to the controller; S5: Based on the comparison result between the real-time detection value obtained in step S4 and the preset target value, the controller outputs an adjustment command to the medium control loop and / or the environment control loop to maintain the environmental parameters and / or the parameters of the corrosive medium within the preset target value range. S6: Under the combined action of the mechanical load and the corrosive medium, stress corrosion is induced in the sample. The test data is recorded to obtain the stress corrosion evaluation results.

[0021] Advantages of this invention: Compared with the prior art, the present invention has the following significant advantages: (1) Through the collaborative control system consisting of independent media control loop and environmental control loop, and in conjunction with the closed-loop feedback regulation of the detection unit and controller, high precision, long-term stability and independent real-time automatic regulation of multiple environmental parameters such as temperature (up to ±0.1℃) and pH value (up to ±0.01) are achieved, fundamentally eliminating the defects of poor repeatability and large data dispersion caused by fluctuations in test conditions, and ensuring that the test conditions highly reproduce the real service environment.

[0022] (2) By using a detachable dynamic sealing component between the environmental cavity and the force transmission component of the loading actuator, zero leakage, constant concentration and stable parameters of the corrosive medium can be achieved while applying mechanical stress, avoiding the problems of medium leakage, concentration drift and sealing failure in the loading process of the prior art, and improving the effectiveness and reliability of the test.

[0023] (3) By designing the load actuator and the rotation drive module to be independent of each other, the decoupled control of stress loading and dynamic environmental exposure is realized. The sample can rotate relative to the environmental cavity while bearing constant mechanical load, simulating dynamic service conditions such as marine fluid scouring and pipeline medium circulation, thus making up for the shortcomings of the single working condition of existing equipment.

[0024] (4) Through the fully detachable modular structure design, the environmental cavity, loading actuator, functional components in the medium control circuit and the functional components in the environmental control circuit are all combined by detachable connection. After any module is disassembled, the remaining modules maintain structural integrity, realizing rapid assembly, disassembly, reassembly and replacement, greatly reducing the difficulty and time of maintenance and cleaning, and improving equipment reusability and test efficiency.

[0025] (5) The loading actuator is compatible with various loading modes such as constant load, constant displacement, and slow strain rate. The medium control loop can adapt to complex working conditions such as high temperature and high pressure, gas phase corrosion, liquid phase corrosion, and gas-liquid coupling corrosion, and fully cover the stress corrosion testing needs of various materials in petrochemical, marine, and nuclear power engineering. Attached Figure Description

[0026] Figure 1This is a schematic diagram of the overall structure of the stress corrosion loading device of the present invention; Figure 2 This is a schematic diagram of the corrosive medium preparation and recovery module in the medium control loop of the present invention; Figure 3 This is a schematic diagram of the corrosive medium preparation unit of the present invention; Figure 4 This is a schematic diagram of the loading actuator and rotation drive module of the present invention; Figure 5 This is a partial structural diagram of the loading actuator of the present invention; Figure 6 This is a schematic diagram of the controller control logic of the present invention; Figure 7 This is a schematic diagram of the control switch unit of the present invention.

[0027] The meanings of the markings in the diagram are as follows: 1-Supporting frame; 2-Supply pipeline; 3-Corrosive medium preparation unit; 4-Return liquid filtration unit; 5-Environmental control loop; 6-Return liquid transfer pump; 7-Drain port; 8-Controller; 9-Control switch unit; 10-Collection tank; 11-Rotary drive module; 12-Loading actuator; 13-Corrosive medium; 14-Supply unit; 15-Detection unit; 16-Sample; 31-NaCl solution storage container; 32-pH adjustment solution storage container; 33-Deionized water storage container; 34-Quantitative supply device; 35-Automatic dispensing cup; 52 53-Temperature sensor; 54-Humidity sensor; 55-pH sensor; 56-Concentration / Conductivity sensor; 97-Power switch; 98-Start button; 99-Stop button; 90-Emergency stop button; 91-Power indicator light; 92-Running indicator light; 93-Automatic / Manual selector switch; 94-Forward / Reverse selector switch; 151-Motor; 162-Gearbox; 173-Shaft; 184-Coupling; 195-Rigid frame module; 196-U-shaped fixing structure; 197-Loading bolts and nuts; 197-Force transmission bolts and nuts. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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 a part of the embodiments of the present invention, not all of them. 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. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention.

[0029] Example 1: Stress Corrosion Loading Device like Figure 1 As shown, the stress corrosion loading device of the present invention adopts a modular structural design. The supporting frame 1 is located in the middle of the entire device as a basic support. The environmental chamber (i.e., the corrosion chamber) is located on the supporting frame 1 and is used to contain the corrosive medium and provide a closed environment for sample corrosion. The supporting frame 1 also supports the corrosive medium supply pipeline 2 and the spray pipeline. The corrosive medium preparation unit 3 is integrated on the upper right side of the environmental chamber, the return liquid filtration unit 4 is located in the return liquid pipeline on the right side of the environmental chamber, the environmental control circuit 5 is located on the lower right side of the environmental chamber, the return liquid delivery pump 6 is located in the return liquid pipeline at the bottom of the environmental chamber, and the controller 8 and control switch unit 9 are located on the lower outer side of the environmental chamber. The rotary drive module 11 is located on the left side of the environmental chamber and is coaxially connected to the loading actuator 12 inside the environmental chamber via a coupling and a rotating shaft.

[0030] The upper part of the environmental cavity is equipped with a liquid supply unit 14, which adopts a multi-nozzle uniform spraying structure. Below the nozzles are the sample 16 and the loading actuator 12. The bottom of the cavity is equipped with a liquid collection pool 10, which forms a collection area for corrosive medium 13. The bottom of the liquid collection pool 10 is equipped with a drain port 7.

[0031] The environmental chamber, loading actuator, functional components in the media control loop (including corrosive medium preparation unit 3, return liquid filtration unit 4, return liquid transfer pump 6, supply liquid pipeline 2, supply liquid unit 14, etc.), and functional components in the environmental control loop (including temperature control unit, humidity control unit, airflow circulation unit, etc.) all adopt a detachable modular structure. Each module is connected via standardized quick-connect fittings, positioning pins, or flanges, allowing for independent disassembly, replacement, cleaning, and calibration of each module without requiring complete machine disassembly. After disassembly of any module, the remaining modules maintain structural integrity. For example, when the test medium needs to be changed, the corrosive medium preparation unit 3 can be completely disassembled, cleaned, and reinstalled. When the dynamic sealing component wears down, only the dynamic sealing component at the connection between the environmental chamber and the force transmission component of the loading actuator needs to be disassembled and replaced, without disassembling the entire machine. When the temperature control range needs to be upgraded, only the heating unit in the environmental control loop needs to be replaced, without affecting the function of the loading actuator and the media control loop.

[0032] Specifically, such as Figure 2 and Figure 3 As shown, the media control loop includes a corrosive media preparation unit 3, a liquid supply unit 14, and a return liquid treatment unit (including a collection tank 10, a drain port 7, a return liquid transfer pump 6, and a return liquid filtration unit 4). This loop is used to supply and circulate corrosive media into the environmental cavity and to adjust the composition parameters (such as salinity, pH value, and concentration) of the corrosive media.

[0033] The corrosive medium preparation unit 3 includes multiple liquid storage containers (NaCl solution storage container 31, pH adjustment solution storage container 32, and deionized water storage container 33) and corresponding metering supply devices 34 (such as metering pumps / valve) connected to each liquid storage container. The outlet of each liquid storage container is connected to the corresponding metering supply device 34 via a corrosion-resistant hose, and the outlet of the metering supply device 34 flows into an automatic dispensing cup 35; the outlet of the automatic dispensing cup 35 is connected to the supply unit 14 at the top of the environmental chamber via a supply pipeline 2.

[0034] The liquid supply unit 14 is used to deliver the prepared corrosive medium into the environmental cavity. During operation, the operator inputs the target salinity, pH value and spray cycle into the controller 8. The controller 8 controls each quantitative supply device 34 to take liquid in proportion and mix it according to the set parameters to prepare a corrosive medium with the target components. After being mixed evenly in the automatic liquid dispensing cup 35, it enters the liquid supply pipeline 2.

[0035] The return fluid treatment unit is connected to the environmental cavity and is used to collect and treat the corrosive media discharged from the environmental cavity. The returned corrosive liquid after spraying enters the drain outlet 7 at the bottom of the environmental cavity via the collection tank 10. The outlet of the drain outlet 7 is connected to the return fluid transfer pump 6, which transports the returned corrosive liquid to the return fluid filtration unit 4. The return fluid filtration unit 4 is equipped with a replaceable filter element to remove corrosion products, deposits, and solid impurities from the returned liquid. The outlet of the return fluid filtration unit 4 is connected to the automatic dispensing cup 35 or the supply pipeline 2, returning the treated corrosive media to the supply unit or the corrosive media preparation unit, forming a closed-loop circulation circuit for the corrosive media.

[0036] Closed-loop regulation process: After the return liquid flows through the online pH sensor 54 and the concentration / conductivity sensor 55 (i.e., part of the detection unit), the detection results are fed back to the controller 8. The controller 8 controls the quantitative supply device 34 to add NaCl solution, pH adjustment solution, or deionized water according to the deviation between the measured composition of the return liquid and the set composition of the corrosive medium, so that the return liquid returns to the set parameters and then re-enters the spray cycle. This forms a closed-loop corrosive medium control process of "liquid supply-spraying-liquid collection-return liquid transportation-filtration monitoring-intelligent allocation-re-liquid supply".

[0037] Specifically, for loading actuators and rotation drive modules, such as Figure 4 and Figure 5 As shown, the loading actuator 12 and the rotary drive module 11 are arranged laterally along the environmental cavity. The rotary drive module 11 includes a motor 111 and a reducer 112, which are located on the outside of the left side of the environmental cavity. The output end of the reducer 112 is connected to the transverse rotating shaft inside the environmental cavity via a rotating shaft 113 and a coupling 114.

[0038] The loading actuator 12 includes a loading frame and a loading drive. The specimen 16 is fixed to the loading frame by a clamping assembly. The loading drive can be an electrically driven structure (such as a servo motor combined with a ball screw) used to apply mechanical loads to the specimen in the form of constant load, constant displacement, or slow strain rate. Before being placed into the environmental chamber, the specimen is preloaded in the loading actuator 12 by bolts or by the clamping assembly to apply a target tensile load, and this preloaded state is maintained by a locking component.

[0039] The rotary drive module 11 is connected to the loading frame and is used to drive the specimen to rotate relative to the environmental cavity. After entering the environmental cavity, the motor 111 is reduced in speed and increased in torque by the reducer 112 to drive the transverse rotating shaft and multiple sets of serially connected specimens to rotate synchronously. The mechanical load applied to the specimen by the loading drive component is independent of the rotational motion of the rotary drive module—that is, the rotary drive module is only used to drive the specimen to rotate so that the specimen can obtain uniform environmental exposure, and does not directly undertake the tensile loading function of the specimen. The controller 8 can control the start and stop, speed, forward / reverse rotation and rotation cycle of the motor, so that multiple sets of specimens can obtain uniform environmental exposure during spraying, wet exposure and drying, and reduce the uneven corrosion caused by unilateral spraying or local liquid accumulation.

[0040] In this invention, the loading frame refers to a rigid load-bearing skeleton structure used to withstand loading reaction forces and provide support for the specimen. It is typically a frame or plate structure, with one end connected to the clamping assembly and the other end connected to the loading drive component, used to transfer the load generated by the loading drive component to the clamping assembly and the specimen. The loading frame can be... Figure 5 The rigid frame module 121 includes main frame bodies on both sides and multiple mounting units in the middle. The mounting units appear in pairs, located on the upper and lower sides of the rigid frame module 121, for fixing and clamping components. The main frame bodies on both sides are vertical beams. A pair of mounting units are fixedly installed on the left vertical beam. The right side of the mounting unit has a buckle, and the right vertical beam has a slot. The remaining mounting units have slots and buckles on the left and right sides respectively, for sequential connection.

[0041] The loading drive component refers to the main power element that directly generates and applies mechanical loads, including but not limited to a servo motor in conjunction with a ball screw, pneumatic cylinder, hydraulic cylinder, or weight lever mechanism, used to apply tensile or compressive mechanical loads in the form of constant load, constant displacement, or slow strain rate to the specimen. The clamping assembly refers to the end-acting element used to directly clamp and fix the end of the specimen, including but not limited to wedge chucks, three-jaw chucks, or flat clamping fixtures, used to accurately transfer the load generated by the loading drive component to the specimen and prevent slippage or deflection of the specimen during loading or rotation. The clamping assembly can be... Figure 5The U-shaped fixing structure 122 is installed on the installation unit by loading bolts and nuts 123. The sample 16 extends into the U-shaped fixing structure 122 and is fixed by force transmission bolts and nuts 124.

[0042] For dynamic sealing structures, a detachable dynamic sealing assembly is installed between the environmental cavity and the force transmission components (such as the rotating shaft and loading tie rod) of the loading actuator. A sealed bearing housing is installed where the transverse rotating shaft passes through the side wall of the environmental cavity, and a bearing and a corrosion-resistant sealing ring are installed inside the sealed bearing housing. The dynamic sealing assembly is used to adaptively compensate for the sealing gap between the force transmission component and the environmental cavity when the force transmission component moves (rotation or axial micro-movement), preventing corrosive media from leaking out along the force transmission component. This dynamic sealing assembly can adopt a multi-stage packing and lip seal combination sealing structure, or a metal spiral seal, graphite flexible seal, or bellows dynamic compensation seal structure. The bellows compensation seal can adapt to the slight deformation and axial movement of the tie rod, resulting in better dynamic sealing performance. Due to the detachable connection method, when the sealing assembly wears out, it can be disassembled and replaced separately without disassembling the entire machine. Among them, the metal seal has better high temperature and high pressure resistance and is suitable for high temperature conditions above 300℃; the bellows compensation seal can adapt to the slight deformation and axial movement of the tie rod, resulting in better dynamic sealing performance and further reducing the risk of media leakage.

[0043] Specifically, for environmental control loops and detection units, such as Figure 6 As shown, an environmental control loop is located outside the environmental cavity and communicates with it, used to regulate the temperature and humidity parameters within the environmental cavity. The environmental control loop includes at least one of a temperature control unit, a humidity control unit, and an airflow circulation unit. The temperature control unit regulates the temperature within the environmental cavity (e.g., a heater or cooler); the humidity control unit regulates the humidity within the environmental cavity (e.g., a humidifier or dehumidifier); and the airflow circulation unit creates a circulating airflow within the environmental cavity (e.g., a fan).

[0044] The detection unit includes at least one of a temperature sensor 52, a humidity sensor 53, a pH sensor 54, a concentration sensor, and a conductivity sensor 55, and is disposed in a medium control loop and / or an environmental cavity to acquire the detection values ​​of component parameters (such as pH value, concentration, conductivity) and / or temperature and humidity parameters in real time.

[0045] Temperature sensor 52 and humidity sensor 53 extend into the chamber through a reserved interface on the side wall of the environmental chamber to detect the ambient temperature and humidity of the actual exposed area of ​​the sample in real time; pH sensor 54 and concentration / conductivity sensor 55 are set at the outlet of the liquid supply line, return liquid delivery line, automatic liquid dispensing cup or return liquid filtration unit to detect the pH value, concentration and conductivity parameters of the corrosive medium in real time.

[0046] Temperature sensor 52, humidity sensor 53, pH sensor 54, and concentration / conductivity sensor 55 are all electrically connected to controller 8, forming a real-time environmental parameter detection pathway.

[0047] Temperature and humidity closed-loop control process: During operation, temperature sensor 52 and humidity sensor 53 continuously collect environmental parameters inside the environmental cavity and transmit the detection results to controller 8. Controller 8 compares the real-time detection values ​​with preset environmental parameters. When the temperature is lower than the set value, it controls the temperature control unit (heater) to increase the heating power; when the humidity is lower than the set value, it controls the humidity control unit (humidifier) ​​to replenish humidity; when entering the drying stage, it controls the airflow circulation unit (fan) to work in conjunction with the temperature control unit (heater) to form a circulating hot air environment inside the environmental cavity; when entering the humid exposure stage, it controls the airflow circulation unit to work in conjunction with the humidity control unit (humidifier) ​​to maintain the set humidity range inside the cavity. This forms a temperature and humidity closed-loop control loop of "environmental parameter detection - controller analysis and judgment - execution unit adjustment - environmental parameter feedback".

[0048] Closed-loop control process for media parameters: The corrosive medium is delivered to the supply unit (spray system) via the supply pipeline and sprayed onto the sample surface. After spraying, the corrosive medium is collected and enters the recycling system via the return pipeline. The pH sensor 54 and the concentration / conductivity sensor 55 continuously monitor the supply or return parameters and feed the results back to the controller 8. When the pH value, conductivity, or media concentration deviates from the set range, the controller 8 sends an adjustment command to the corrosive medium preparation unit 3, controlling the quantitative supply device 34 to add sodium chloride solution, pH adjustment solution, or deionized water, so that the corrosive medium returns to the set parameters and re-enters the supply cycle. This forms a closed-loop control loop for the corrosive medium: "media parameter detection - controller analysis and judgment - automatic media compensation - parameter re-detection".

[0049] Through the above-mentioned dual closed-loop control mechanism, the automatic switching of the three stages of immersion / spraying, wet exposure and drying is realized, as well as the long-term stable control of the parameters of the corrosive medium.

[0050] Specifically, for the controller and control logic, the controller 8 can be a PLC intelligent control terminal, which is connected to the detection unit, the media control loop, and the environmental control loop respectively. It is used to independently control the operation of the media control loop and the environmental control loop according to the deviation between the preset target value and the detected value. The controller 8 has a built-in parameter setting unit, a comparison unit, and an instruction output unit.

[0051] The parameter setting unit is used to set target environmental parameters (such as target temperature and target humidity) and target medium parameters (such as target pH value, target concentration, and target salinity). The comparison unit is used to compare the real-time detection values ​​of the detection unit with the target environmental parameters or target medium parameters to obtain deviation signals (such as ΔT, ΔpH, and Δconcentration). The command output unit is used to output adjustment commands to the corresponding actuators (such as heaters, humidifiers, metering pumps / valve, motors, etc.) based on the deviation signals. The controller 8 has a built-in PID control unit that calculates the output control quantity based on the proportional (P), integral (I), and derivative (D) of the deviation between the detected value and the target value to achieve precise closed-loop control.

[0052] The controller 8 is electrically connected to the temperature and humidity sensing probes, pH sensor, concentration / conductivity sensor, and various switching signals to form a real-time environmental parameter detection path. The controller 8 outputs control signals to the metering supply device 34 (metering pump / valve), fan, heating / drying unit, humidification unit, rotary drive module 11, return liquid transfer pump 6, and alarm components.

[0053] The control switch unit 9 is used to realize the start and stop of the whole machine power supply, automatic / manual mode switching, forward and reverse direction switching, and emergency stop protection in abnormal conditions. For its specific structure, please refer to Embodiment 7.

[0054] Example 2: Test Method The method for conducting tests using the above-mentioned stress corrosion loading device includes the following steps: S1: Specimen Installation and Loading. The specimen 16 to be tested is installed on the loading actuator 12, and a predetermined mechanical load (constant load, constant displacement, or slow strain rate) is applied to the specimen through the loading drive component to obtain the loaded specimen. The specimen is loaded and locked before being placed into the environmental cavity to eliminate the influence of operation within the environmental cavity on the loading state.

[0055] S2: Supplying the corrosive medium. Using the sample loaded in step S1, a target corrosive medium with set parameters (such as set salinity and pH value) is supplied to the environmental cavity through the medium control loop, so that the sample is in the target corrosive medium environment. Specifically, the controller 8 controls each quantitative supply device 34 to quantitatively take liquid and mix it according to the set parameters. After preparing the corrosive medium with the target components, it is transported to the environmental cavity through the liquid supply pipeline 2 and the liquid supply unit 14 (spray structure) and sprayed onto the sample surface.

[0056] S3: Adjust environmental parameters. Based on step S2, the environmental parameters (such as temperature and humidity) inside the environmental cavity are adjusted to the set range through the environmental control loop. Specifically, the controller 8 controls the operation of the temperature control unit (heater), humidity control unit (humidifier), and airflow circulation unit (fan) according to the preset target value to achieve the set temperature and humidity conditions inside the cavity.

[0057] S4: Real-time detection. During step S3, the environmental parameters (temperature, humidity) and / or parameters (pH value, concentration, conductivity) of the environmental cavity are detected in real time by the detection unit (temperature sensor 52, humidity sensor 53, pH sensor 54, concentration / conductivity sensor 55), and the real-time detection values ​​are obtained and transmitted to the controller 8.

[0058] S5: Closed-loop control. Based on the comparison between the real-time detection value obtained in step S4 and the preset target value, controller 8 outputs adjustment commands to the medium control loop and / or environmental control loop to maintain the environmental parameters and / or the parameters of the corrosive medium within the preset target value range. Specifically, when the temperature deviates from the target value, controller 8 controls the heater or cooler to operate; when the pH value deviates from the target value, controller 8 controls the metering supply device 34 to replenish the pH adjustment liquid. This step, together with S2, S3, and S4, constitutes a dual closed-loop control, which runs continuously throughout the entire experiment.

[0059] S6: Test and Data Recording. Under the combined action of mechanical load and corrosive medium, stress corrosion is induced in the sample. Test data (such as fracture time, crack propagation rate, electrochemical parameters, etc.) are recorded to obtain stress corrosion evaluation results.

[0060] Specifically, for the safety start / stop and mode switching unit, such as Figure 7 As shown, the safety start / stop and mode switching unit corresponds to... Figure 1 The control switch unit 9 is located near the controller 8 and electrically connected to the controller 8. This unit includes a power switch 91, a start button 92, a stop button 93, an emergency stop button 94, a power indicator light 95, a running indicator light 96, an automatic / manual selection switch 97, and a forward / reverse selection switch 98.

[0061] Power switch 91 is used to connect or disconnect the power supply to the entire machine. Start button 92 and stop button 93 are used to start and stop the test program, respectively. Emergency stop button 94 is used to immediately cut off the rotary drive and pump valve output in case of leakage, overheating, sensor malfunction, or motor malfunction. Automatic / manual selection switch 97 is used to switch between the automatic closed-loop control mode and manual jogging adjustment mode of controller 8. Forward / reverse selection switch 98 is used to change the rotation direction of rotary drive module 11, which, in conjunction with the speed parameters in controller 8, realizes the control of sample rotation speed, direction, and cycle. Power indicator light 95 and running indicator light 96 are used to display the power-on status and test running status of the entire machine, thereby facilitating the operator's intuitive judgment of the device's working status and improving test safety.

[0062] The electric precision loading structure using a servo motor and ball screw in Embodiment 1 of this invention can also be replaced with a pneumatic loading structure, a hydraulic loading structure, or a weight lever mechanical loading structure. Pneumatic and hydraulic loading methods are suitable for ultra-high load and ultra-high pressure conditions, offering greater load output torque and stronger impact resistance. The weight lever loading structure is simple, lower in cost, and extremely stable, suitable for ambient temperature and pressure, low strain rate, and long-term static constant load aging tests. Furthermore, the single-center loading tie rod structure can be replaced with a multi-tier symmetrical loading structure, further improving structural coaxiality under ultra-high loads and eliminating minor eccentric bending moments. All of the above alternative structures can be matched with the universal assembly interfaces of the load-bearing frame and environmental cavity, without requiring modification to the overall modular architecture.

[0063] In Example 1, a lower-mounted servo-reduced rotary drive structure is used, which eliminates the need for a bottom rotary motor and can be replaced with an upper coaxial rotary drive structure, a magnetic non-contact rotary drive structure, or a fully locking and fixed clamping structure. When using the upper rotary drive scheme, the rotary drive unit is integrated into the upper end of the loading rod, and there are no electrical drive components inside the cavity, further improving equipment safety under high-temperature, high-pressure, and highly corrosive conditions. The magnetic non-contact rotary drive method achieves a fully sealed, non-penetrating drive, eliminating the dynamic seal structure of the transmission shaft and preventing dynamic seal wear and leakage. When using a fully fixed clamping structure, the rotation function is eliminated, resulting in a simpler and more rigid structure, specifically suited for traditional static stress corrosion testing. Furthermore, the wedge-shaped self-centering clamp can be replaced with a three-jaw circumferential clamp or a flat plate clamping clamp, suitable for clamping and fixing irregularly shaped specimens, weld specimens, and pipe slice specimens.

[0064] Example 1 employs a split, snap-fit ​​quick-release chamber structure. This snap-fit ​​structure can be replaced with a flange bolt-tightening sealing structure or a flip-top quick-opening sealing structure. The flange bolt-tightening structure provides greater sealing force and higher pressure resistance, making it suitable for extreme test conditions such as ultra-high temperature and high pressure. The flip-top structure has a shorter opening stroke and faster assembly / disassembly speed, making it suitable for large-volume, high-frequency sample rotation testing. Simultaneously, the PTFE lining of the chamber can be replaced with a Hastelloy anti-corrosion coating or a titanium alloy lining structure, further enhancing the chamber's corrosion resistance against strong oxidizing, strong acid, and strong alkali corrosive media. The overall volume of the chamber and the number of interfaces can be flexibly adjusted according to test requirements.

[0065] Example 1 employs a multi-metering pump active proportioning and online real-time titration control scheme. In low-precision, standard testing scenarios, the multi-pump automatic proportioning structure can be replaced with a manual pre-mixing and constant-pressure replenishment automatic compensation structure, simplifying the equipment structure and reducing costs. The corresponding pH control method can be replaced by micro-pump dynamic titration with automatic buffer replacement and intermittent quantitative reagent replenishment; the media mixing structure can be replaced with magnetic stirring and airflow agitation mixing, both of which achieve uniform media mixing and concentration stability. Furthermore, the media circulation loop can be replaced with a static immersion closed structure, eliminating the circulation pump body and specifically adapting to static immersion stress corrosion tests.

[0066] In Example 1, a centralized closed-loop control using a PLC is employed. Alternatively, distributed microcontroller control or cloud-based remote programmable control can also be used. Furthermore, the multi-parameter PID coupling algorithm can be replaced with fuzzy PID or adaptive PID algorithms to improve the parameters' anti-interference capability under complex fluctuating conditions. These changes in control methods are merely equivalent replacements of algorithms and hardware, without altering the overall modular structure of the device or its core experimental principles.

[0067] The above description is merely an embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related system fields, are similarly included within the scope of protection of the present invention.

Claims

1. A stress corrosion loading device, characterized in that, include: An environmental chamber is used to contain corrosive media and provide a corrosive environment for the sample. The loading actuator (12) acts on the sample (16) inside the environmental cavity to apply a mechanical load to the sample (16); The medium control loop is connected to the environmental cavity and is used to supply and circulate the corrosive medium (13) into the environmental cavity and to adjust the composition parameters of the corrosive medium (13). An environmental control loop (5) is connected to the environmental cavity and is used to adjust the temperature and humidity parameters within the environmental cavity. The detection unit (15) is set in the medium control circuit and / or the environmental cavity to acquire the detection values ​​of component parameters and / or temperature and humidity parameters in real time. The controller (8) is connected to the detection unit (15), the medium control loop and the environmental control loop (5) respectively, and is used to independently control the operation of the medium control loop and the environmental control loop (5) according to the deviation between the preset target value and the detection value. The loading actuator (12) includes a loading frame and a loading drive component. The sample (16) is fixed to the loading frame by a clamping assembly. The device also includes a rotation drive module (11), which is connected to the loading frame for driving the sample (16) to rotate relative to the environmental cavity. The mechanical load applied to the sample (16) by the loading drive component is independent of the rotational motion of the rotation drive module (11). A detachable dynamic sealing assembly is provided between the environmental cavity and the force transmission component of the loading actuator (12). The dynamic sealing assembly is used to adaptively compensate for the sealing gap between the force transmission component and the environmental cavity when the force transmission component moves. The environmental cavity, the loading actuator (12), the functional components in the medium control circuit and the functional components in the environmental control circuit (5) all adopt a detachable modular structure. The modules are combined by a detachable connection method, and the remaining modules remain structurally intact after any module is disassembled.

2. The stress corrosion loading device according to claim 1, characterized in that, The medium control circuit includes a corrosive medium preparation unit (3), a liquid supply unit (14), and a liquid return treatment unit; The corrosive medium preparation unit (3) is used to prepare the corrosive medium (13) according to the set parameters. The liquid supply unit (14) is connected to the environmental cavity and is used to deliver the prepared corrosive medium (13) into the environmental cavity; The liquid return treatment unit is connected to the environmental cavity and is used to collect and treat the corrosive medium (13) discharged from the environmental cavity, and return the treated corrosive medium (13) to the liquid supply unit (14) or the corrosive medium preparation unit (3) to form a closed loop of corrosive medium (13).

3. The stress corrosion loading device according to claim 2, characterized in that, The corrosive medium preparation unit (3) includes multiple liquid storage containers and a quantitative supply device (34) connected to each liquid storage container. The controller (8) controls each quantitative supply device (34) to take liquid in proportion and mix according to the set parameters to prepare a corrosive medium (13) with the target components.

4. The stress corrosion loading device according to claim 1, characterized in that, The loading actuator (12) includes an electric loading structure, a pneumatic loading structure, a hydraulic loading structure or a weight lever loading structure, used to apply a mechanical load in the form of constant load, constant displacement or slow strain rate to the sample (16).

5. The stress corrosion loading device according to claim 1, characterized in that, The environmental control loop (5) includes at least one of a temperature control unit, a humidity control unit, and an airflow circulation unit; The temperature control unit is used to regulate the temperature inside the ambient cavity; The humidity control unit is used to regulate the humidity inside the environmental cavity; The airflow circulation unit is used to create a circulating airflow within the environmental cavity.

6. The stress corrosion loading device according to claim 1, characterized in that, The controller (8) includes a parameter setting unit, a comparison unit, and an instruction output unit; The parameter setting unit is used to set the target environment parameters and the target medium parameters; The comparison unit is used to compare the real-time detection value of the detection unit (15) with the target environmental parameters or target medium parameters to obtain a deviation signal; The instruction output unit is used to output adjustment instructions to the corresponding execution components according to the deviation signal.

7. The stress corrosion loading device according to claim 1, characterized in that, The detection unit (15) includes at least one of a temperature sensor (52), a humidity sensor (53), a pH sensor (54), and a concentration / conductivity sensor (55).

8. A stress corrosion testing method, characterized in that, The test using the stress corrosion loading device according to any one of claims 1 to 7 includes the following steps: S1: The test specimen (16) is mounted on the loading actuator (12), and a predetermined mechanical load is applied to the specimen (16) to obtain the loaded specimen (16). S2: Using the sample (16) loaded in step S1, the target corrosive medium (13) with set parameters is supplied to the environmental cavity through the medium control circuit, so that the sample (16) is in the environment of the target corrosive medium (13). S3: Based on step S2, the environmental parameters in the environmental cavity are adjusted to the set range through the environmental control loop (5); S4: During step S3, the environmental parameters and / or parameters of the corrosive medium (13) in the environmental cavity are detected in real time by the detection unit (15) to obtain real-time detection values, and the real-time detection values ​​are transmitted to the controller (8). S5: The controller (8) outputs adjustment commands to the medium control loop and / or the environment control loop (5) based on the comparison result between the real-time detection value obtained in step S4 and the preset target value, so that the environmental parameters and / or the parameters of the corrosive medium (13) are maintained within the preset target value range. S6: Under the combined action of the mechanical load and the corrosive medium (13), the sample (16) is subjected to stress corrosion. The test data is recorded to obtain the stress corrosion evaluation results.

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