Closed-loop uniaxial strain testing method, system and apparatus under multi-physics conditions

Abstract

The application discloses a closed-loop uniaxial strain test method, system and device under multiple physical field conditions, and relates to the technical field of function test. The method comprises the following steps: installing a sample to be tested in a sample mounting area of a closed-loop uniaxial strain test device, applying loading scanning to the sample to be tested, determining loading conversion parameters, converting a target strain track or a target stress track into a loading control sequence, and performing uniaxial strain loading on the sample to be tested. The method further comprises the following steps: calculating loading control errors and feedback characteristic quantities, determining the effectiveness of the loading conversion parameters, pausing the current loading when the loading conversion parameters are invalid, re-determining the loading conversion parameters, and outputting a loading track and corresponding electrical measurement signals after the test is completed. The application solves the technical problem that the loading conversion parameters between the driving output quantity and the actual strain value or stress value at the sample end are prone to deviating during the uniaxial strain loading test process under multiple physical field conditions, thereby affecting the loading control accuracy and the comparability of test data.

Description

Technical Field

[0001] This invention relates to the field of functional testing technology, and in particular to a closed-loop uniaxial strain testing method, system, and apparatus under multi-physics conditions. Background Technology

[0002] Uniaxial strain or uniaxial stress loading tests are commonly used experimental methods in materials property research and service behavior analysis. By applying tensile or compressive loads to a sample along a single direction, the changes in the material's electrical, magnetic, and other physical properties with stress or strain values ​​can be observed under continuously adjustable external parameters. This allows for the study of material phase transition behavior, anisotropic effects, and multiphysics coupling characteristics. To obtain reliable experimental conclusions, it is usually necessary to simultaneously acquire electrical parameters such as resistance and capacitance, or other weak signals, while the loading state changes. Furthermore, a stable correspondence between the loading state and the measured data is required, ensuring the repeatability and comparability of data from different batches of samples, under different loading conditions, and under different external environmental conditions.

[0003] Existing uniaxial loading testing systems generally consist of a loading output section, a sample clamping and signal extraction section, a measurement and acquisition section, and a data recording and analysis section. The loading output section generates displacement or load and transfers it to the sample. The clamping and extraction section secures the sample and handles the connection and shielding grounding of the measurement cables. The measurement and acquisition section acquires measurements related to the loading state and in-situ response signals. The data recording and analysis section stores data, performs calibration conversions, and organizes experimental results. In actual experiments, to convert the driving output quantity into the actual strain or stress value at the sample end, it is usually necessary to establish a conversion relationship between the driving quantity and the loading state at the sample end through pre-calibration or loading scanning. This conversion relationship is then used for loading control and data analysis during subsequent testing.

[0004] When the testing environment expands to multi-physics conditions such as low temperature, strong magnetic field, and high vacuum, the system typically needs to be integrated with a cryogenic platform, magnet, and vacuum chamber. Constrained by probe space, thermal management, electromagnetic compatibility, and insulation and shielding structures, the loading and measurement links are more prone to structural changes due to environmental variations. On one hand, temperature changes cause differences in thermal contraction between structural components and the clamping interface, altering contact pressure, friction, and force transmission paths, thus changing the correlation between the drive output and the actual strain or stress value at the sample end. On the other hand, changes in the magnetic field or electromagnetic environment may alter the electromagnetic coupling state of surrounding cables, causing changes in noise levels, zero-point baseline, or signal response characteristics in the measurement link.

[0005] Under the aforementioned multiphysics conditions, when the environmental or structural state changes, the previously established correspondence between the driving output and the actual loading state of the sample may deviate from the actual situation, thus causing a difference between the loading control state and the actual loading state of the sample, and affecting the correspondence between the loading state and the electrical measurement signal, thereby increasing the difficulty of comparing and analyzing test data under different temperatures, magnetic fields, or experimental batches. Summary of the Invention

[0006] This invention provides a method, system, and apparatus for closed-loop uniaxial strain testing under multiphysics conditions. The technical solutions provided by this invention are as follows: In a first aspect, the present invention provides a closed-loop uniaxial strain testing method under multi-physics field conditions. The method includes: S1, installing the sample to be tested in the sample mounting area of ​​the closed-loop uniaxial strain testing device, connecting the position measuring device and the electrical measuring circuit, and acquiring the initial loading measurement signal.

[0007] S2. After receiving the initial loading measurement signal, apply a loading scan within the preset loading range to the sample to be tested, and simultaneously acquire displacement feedback signal, stress feedback signal and electrical measurement signal during the loading scan to determine the loading conversion parameter between the loading driving amount and the actual strain value or stress value at the sample end.

[0008] S3. Based on the loading conversion parameters, the target strain trajectory or target stress trajectory is converted into the corresponding loading control sequence, and uniaxial strain loading is performed on the sample to be tested according to the loading control sequence, while continuously acquiring displacement feedback signals, stress feedback signals and electrical measurement signals.

[0009] S4. During the uniaxial strain test, the loading control error is calculated based on the target loading amount and the corresponding feedback signal. The target loading amount is the target strain value or the target stress value. The loading drive output is adjusted according to the loading control error so that the sample is loaded in a closed loop according to the target loading trajectory.

[0010] S5. Simultaneously calculate the feedback characteristic quantity based on the displacement feedback signal, stress feedback signal and electrical measurement signal, and determine the validity of the loading conversion parameter between the loading driving quantity and the actual strain value or stress value at the sample end based on the feedback characteristic quantity.

[0011] S6. When the validity determination result indicates that the loading conversion parameter is invalid, pause the current loading and reapply the loading scan to the sample to redetermine the loading conversion parameter, and then continue to perform the uniaxial strain loading test.

[0012] S7. After the test is completed, output the loading trajectory and the corresponding electrical measurement signal.

[0013] A second aspect of the present invention provides a closed-loop uniaxial strain testing system under multi-physics conditions, comprising: a measurement module and a control system.

[0014] The measurement module is used to apply uniaxial strain loading to the sample under test in a multi-physics environment and to acquire displacement feedback signals, stress feedback signals and electrical measurement signals during the loading process. It includes a cryogenic measurement end, a rod and a room temperature terminal.

[0015] The cryogenic measurement end is used to mount the sample to be tested in a cryogenic or magnetic field environment and apply uniaxial strain loading.

[0016] The rod is used to transfer the applied displacement to the sample and the mechanical response at the sample end to the room temperature terminal.

[0017] Room temperature terminals are used to establish electrical connections between measurement signals and the control system.

[0018] The control system is used to perform loading scanning, loading control, and loading conversion parameter updates based on the acquired displacement feedback signals, stress feedback signals, and electrical measurement signals, and to perform closed-loop control of the uniaxial strain loading process. It includes a closed-loop piezoelectric control system, an electrical measurement system, and a host computer.

[0019] A closed-loop piezoelectric control system is used to output a drive voltage according to a load control sequence to drive a piezoelectric actuator to generate a load drive quantity.

[0020] The electrical measurement system is used to acquire electrical measurement signals of the sample under test during the loading process.

[0021] The host computer is used to calculate loading conversion parameters, generate loading control sequences, calculate loading control errors, determine the validity of loading conversion parameters, and regenerate loading scan sequences when loading conversion parameters fail, based on the collected displacement feedback signals, stress feedback signals, and electrical measurement signals.

[0022] The third aspect of the present invention is a closed-loop uniaxial strain testing device under multi-physics field conditions, comprising a transferable sample holder, a displacement application and sensor layer, a lever layer and a piezoelectric drive layer.

[0023] The transferable sample holder includes a sample holder frame, a sample fixing end, a sample loading end, and a sample holder flexible hinge. The sample fixing end is fixedly connected to the sample holder frame, and the sample loading end is connected to the sample holder frame through the sample holder flexible hinge, so that the sample loading end can be displaced relative to the sample holder frame in a single direction. The two ends of the sample to be tested are fixed between the sample fixing end and the sample loading end, respectively.

[0024] The displacement applied to the sensor layer includes a sensor layer frame, a sensor layer movable electrode one, a sensor layer movable electrode two, a position sensor mounting area one, a position sensor mounting area two, a sensor layer flexible hinge one, and a sensor layer flexible hinge two. The sensor layer movable electrode one is connected to the sensor layer frame through the sensor layer flexible hinge one, and the sensor layer movable electrode two is connected to the sensor layer frame through the sensor layer flexible hinge two, so that the sensor layer movable electrode one and the sensor layer movable electrode two can generate elastic displacement relative to the sensor layer frame. Position sensors are installed in the position sensor mounting areas one and two on the sensor layer frame, respectively, to detect the change in the slit width between the sensor layer movable electrode one and the sensor layer movable electrode two, thereby obtaining the displacement change signal generated during the loading process.

[0025] The lever layer includes a fixed end, a rotating end, and a fulcrum flexible hinge. The rotating end is connected to the fixed end via the fulcrum flexible hinge. The fixed end is connected to the piezoelectric drive layer. The rotating end is connected to the displacement application sensor layer. The drive displacement is transmitted to the displacement application sensor layer through the lever structure.

[0026] The piezoelectric drive layer includes a drive base, a drive output end, a piezoelectric actuator, and a piezoelectric connecting bridge. The piezoelectric actuator is disposed between the drive base and the drive output end. When a drive voltage is applied, the piezoelectric actuator elongates or contracts, causing the drive output end to undergo a displacement change relative to the drive base. This displacement is then transmitted to the sensor layer through the lever layer, thereby driving the sample to be tested in the transferable sample holder to generate uniaxial strain loading.

[0027] The beneficial effects of the technical solutions provided in the embodiments of the present invention include at least the following: 1. This invention establishes a loading conversion parameter between the loading drive quantity and the actual strain or stress value at the sample end during uniaxial strain testing. During loading operation, it continuously monitors and dynamically verifies the loading state by combining displacement feedback signals, stress feedback signals, and electrical measurement signals, ensuring that the loading drive output maintains a stable correspondence with the actual loading state at the sample end. When changes in multiphysics conditions lead to changes in the structural force transmission path, contact state, or signal environment, the invention can promptly identify deviations in the loading conversion parameter, thereby ensuring a stable and reliable correspondence between the loading control process and the sample's electrical response. This improves the loading accuracy and the consistency and comparability of experimental data in uniaxial strain testing under multiphysics conditions such as low temperature, strong magnetic field, and high vacuum.

[0028] 2. By applying a load scan to the sample under test during the initial loading stage and simultaneously acquiring displacement feedback signals, stress feedback signals, and electrical measurement signals, the loading driving quantity can establish a loading conversion parameter based on measured data with the actual strain or stress value at the sample end. This does not rely on a single structural calibration relationship. Instead, the loading conversion parameter is established using the response data of the sample in the actual clamping state. This reduces the probability that differences in the clamping interface, sample size deviations, and minor structural deformations will affect the accuracy of the loading quantity transfer. As a result, the loading driving quantity can more accurately reflect the true loading state at the sample end, improving the reliability and measurement accuracy of uniaxial strain loading control.

[0029] 3. During uniaxial strain testing, feedback characteristic quantities are calculated, and the validity of the loading conversion parameters is determined using the characteristic deviation between the feedback characteristic quantities and the loading response change sequence. When the cumulative deviation value exceeds a preset cumulative deviation threshold, it can be identified that the current loading conversion parameters can no longer accurately reflect the actual loading state, and the loading scan is automatically re-executed to update the loading conversion parameters. Through this dynamic verification and update mechanism based on operational data, the drift in loading relationships caused by changes in multi-physics environment or structural state can be identified relatively promptly, ensuring that the loading control process always remains consistent with the true strain or stress values ​​at the sample end, thus improving the stability and data reliability under long-term testing and multi-condition testing conditions.

[0030] 4. The closed-loop uniaxial strain testing device of this invention adopts a layered structure design consisting of a piezoelectric driving layer, a lever layer, and a displacement application and sensor layer. The driving displacement generated by the piezoelectric actuator is transmitted and adjusted through the lever layer, and the displacement change is detected in real time by the moving electrode and position sensor in the displacement application and sensor layer. Simultaneously, a transferable sample holder enables rapid installation and stable fixation of the sample. This structure can accurately detect actual displacement changes while ensuring stable transmission of the driving displacement, and reduces the impact of sample installation and replacement on the overall structure. This improves the displacement measurement accuracy and clamping repeatability during uniaxial strain loading, further enhancing the operational stability of the testing system in multi-physics environments. Attached Figure Description

[0031] The accompanying drawings are provided for a better understanding of this solution and do not constitute a limitation of the invention. Wherein: Figure 1 The flowchart shows the closed-loop uniaxial strain testing method under multiphysics conditions. Figure 2 A schematic diagram of the hierarchy of a closed-loop uniaxial strain testing device under multiphysics conditions; Figure 3 This is a structural diagram of the closed-loop uniaxial strain testing device under multi-physics field conditions according to an embodiment of the present invention; Figure 4This is a schematic diagram of the structure of the transferable sample holder according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the displacement application and sensor layer involved in an embodiment of the present invention; Figure 6 This is a schematic diagram of the lever layer involved in this embodiment; Figure 7 This is a schematic diagram of the structure of the piezoelectric drive layer involved in this embodiment of the invention; Figure 8 This is a system architecture diagram of a closed-loop uniaxial strain testing system under multiphysics conditions.

[0032] The components include: 1. Transferable sample holder; 2. Displacement application and sensor layer; 3. Lever layer; 4. Piezoelectric drive layer; 5. Sample mounting area; 6. Wiring area; 7. Uniaxial strain gauge; 8. Transferable sample stage; 9. Sample holder frame; 10. Sample fixing end; 11. Sample loading end; 12. Sample holder flexible hinge; 13. Sensing layer frame; 14. Sensing layer moving pole one; 15. Sensing layer moving pole two; 16. Position sensor mounting area one; 17. Position sensor mounting area two; 18. Sensing layer flexible hinge one; 19. Sensing layer flexible hinge two; 20. Lever fixing end; 21. Lever rotating end; 22. Lever fulcrum flexible hinge; 23. Drive fixing seat; 24. Drive output end; 25. Piezoelectric actuator; 26. Piezoelectric connecting bridge. Detailed Implementation

[0033] The following description, in conjunction with the accompanying drawings, illustrates exemplary embodiments of the present invention, including various details to aid understanding. These details should be considered merely exemplary. Therefore, those skilled in the art will recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the invention. Similarly, for clarity and brevity, descriptions of well-known functions and structures are omitted in the following description.

[0034] Embodiment 1 of the present invention provides a closed-loop uniaxial strain testing method under multiphysics field conditions, such as... Figure 1The diagram shows a flowchart of a closed-loop uniaxial strain testing method under multiphysics conditions, including the following steps: The sample to be tested is installed in the sample mounting area of ​​the closed-loop uniaxial strain testing device, and a position measurement device and electrical measurement circuit are connected. A load scan within a preset loading range is applied to the sample. The loading conversion parameter between the loading driving quantity and the actual strain or stress value at the sample end is determined. The target strain trajectory or target stress trajectory is converted into a corresponding loading control sequence, and uniaxial strain loading is performed on the sample according to the loading control sequence. During the uniaxial strain test, the loading control error is calculated, and the feedback characteristic quantity is calculated simultaneously. The validity of the loading conversion parameter is determined based on the feedback characteristic quantity. When the validity determination result indicates that the loading conversion parameter is invalid, the current loading is paused, and a loading scan is reapplied to the sample to re-determine the loading conversion parameter. Then, the uniaxial strain loading test continues. After the test, the loading trajectory and the corresponding electrical measurement signal are output. The above-mentioned closed-loop uniaxial strain testing method under multiphysics conditions is applied to a closed-loop uniaxial strain testing device under multiphysics conditions, such as... Figure 2 The diagram shows the hierarchical structure of a closed-loop uniaxial strain testing device under multiphysics conditions. From top to bottom, it includes a transferable sample holder 1, a displacement application and sensor layer 2, a lever layer 3, and a piezoelectric drive layer 4. These layers are stacked sequentially along the uniaxial loading direction (from top to bottom), allowing displacement to be transferred step-by-step between layers. The transferable sample holder 1 is located at the top of the device, used to mount the sample to be tested and serving as the final point of application for the loaded displacement. The displacement application and sensor layer 2 is located below the transferable sample holder 1. This layer detects displacement changes during loading and transfers the loaded displacement to the upper layers. The lever layer 3 is located below the displacement application and sensor layer 2. This lever layer includes a fixed lever end 20, a rotating lever end 21, and a flexible hinge at the lever fulcrum 22. This layer receives the driving displacement from the piezoelectric drive layer 4 through the fixed lever end 20, and after rotation or micro-displacement is transmitted via the flexible hinge at the lever fulcrum 22, the displacement is transmitted to the displacement application and sensor layer 2 through the rotating lever end 21. The displacement ratio is adjusted according to the relative positions of the lever components. The piezoelectric drive layer 4 is located at the bottom of the device. This layer generates expansion and contraction displacement through a piezoelectric actuator when a driving voltage is applied, thus forming the displacement drive source of the device. In this hierarchical structure, the displacement generated by the piezoelectric drive layer 4 is first transmitted to the lever layer 3, and then, after being transmitted through the structure of the lever layer 3, it enters the displacement application and sensor layer 2. In the displacement application and sensor layer 2, the relative displacement change is detected by the sensing structure, and the displacement is further transmitted to the transferable sample holder 1, thereby applying uniaxial strain to the sample to be tested mounted in the sample holder. Figure 3The diagram shows the device structure of a closed-loop uniaxial strain testing device under multi-physics conditions according to an embodiment of the present invention. It includes a sample mounting area 5, a wiring area 6, a uniaxial strain device 7, and a transferable sample stage 8. The sample mounting area 5 is located at the center of the upper surface of the device and is used to mount the sample to be tested, forming a sample fixing area. A mounting structure for fixing the sample is provided within this area, enabling the sample to maintain a stable position during uniaxial loading. The wiring area 6 is located on one side of the sample mounting area 5 and is used to connect electrical measurement circuits and related signal wires. This wiring area allows the sample to be connected to external measuring equipment, thereby synchronously acquiring the sample's electrical response signal during loading. The uniaxial strain device 7 is located below the sample mounting area 5. This structure includes a displacement application sensor layer 2, a lever layer 3, and a piezoelectric drive layer 4, used to generate displacement during loading and transmit the displacement to the sample end, thereby achieving uniaxial strain loading. A stress value detection structure is located on the sample loading path, used to detect the stress applied to the sample in the axial direction and output a stress feedback signal. The transferable sample stage 8 is positioned above the uniaxial strain gauge 7 to support the pre-prepared sample holder structure. The transferable sample stage 8 allows for rapid installation and removal of the sample holder, eliminating the need to disassemble the entire strain gauge when changing samples, thus improving experimental efficiency.

[0035] The stress detection structure is used to detect the stress applied to the sample in the axial direction. It is positioned along the sample loading path, specifically at the sample loading end 11, the sample fixing end 10, or the force transmission connector. The stress detection structure can employ a strain gauge force sensor, a piezoelectric force sensor, or a MEMS force sensor. It is connected to the data acquisition module via wires to output a stress feedback signal. This signal originates from the real-time measurement data of the stress detection structure and is used to characterize the current actual stress state at the sample end, calculate the stress value at the sample end, and participate in the determination of loading conversion parameters and validity assessment processes.

[0036] like Figure 4The diagram shows a schematic representation of the transferable sample holder according to an embodiment of the present invention. The transferable sample holder is used to achieve rapid installation and stable clamping of the sample under test during uniaxial strain loading, and to transfer external load displacement to the sample under test during loading. It includes a sample holder frame 9, a sample fixing end 10, a sample loading end 11, and a sample holder flexible hinge 12. The sample holder frame 9 is the supporting structure for the transferable sample holder, used to support the sample fixing end 10, the sample loading end 11, and the sample holder flexible hinge 12. The sample fixing end 10 is located on one side of the sample holder frame 9 and forms a rigid connection with the sample holder frame 9, ensuring that the position of the sample fixing end 10 relative to the sample holder frame 9 does not change during loading. One end of the sample under test is fixed to the sample fixing end 10, and a stable connection is formed between the sample end and the sample fixing end 10 through a clamping structure or adhesive method, thereby providing a stable reference end during loading. The sample loading end 11 is located on the opposite side of the sample fixing end 10 and is connected to the sample holder frame 9 through the sample holder flexible hinge 12. The flexible hinge 12 of the sample holder forms a connection structure with elastic deformation capability, which enables the sample loading end 11 to generate a small displacement along the loading direction under the constraint of the sample holder frame 9, while restricting the free movement of the sample loading end 11 in other directions, thereby ensuring that the movement direction of the sample loading end 11 is consistent with the uniaxial strain loading direction.

[0037] like Figure 5The diagram shown illustrates the structure of the displacement application and sensor layer according to an embodiment of the present invention. It includes a sensor layer frame 13, a first sensor layer moving pole 14, a second sensor layer moving pole 15, a first position sensor mounting area 16, a second position sensor mounting area 17, a first sensor layer flexible hinge 18, and a second sensor layer flexible hinge 19. The sensor layer frame 13 serves as the main support structure of this layer, supporting the first sensor layer moving pole 14, the second sensor layer moving pole 15, and the corresponding first and second sensor layer flexible hinges 18 and 19, and forming a stable connection with other structural layers in the overall device. During operation, the sensor layer frame 13 remains fixed, providing reference support for the moving structure. The first sensor layer moving pole 14 is located on one side inside the sensor layer frame 13 and is connected to the sensor layer frame 13 via the first sensor layer flexible hinge 18. The first flexible hinge 18 of the sensing layer forms a flexible connection structure with elastic deformation capability, enabling the first movable electrode 14 of the sensing layer to generate a small elastic displacement along the loading direction under external displacement, while restricting its movement in other directions, thereby ensuring that its movement trajectory is consistent with the uniaxial loading direction. The second movable electrode 15 of the sensing layer is located on the other side inside the sensing layer frame 13 and is connected to the sensing layer frame 13 through the second flexible hinge 19 of the sensing layer. The second flexible hinge 19 of the sensing layer also forms a flexible support structure, enabling the second movable electrode 15 of the sensing layer to generate elastic displacement relative to the sensing layer frame 13 during loading. Through the structural design of the first flexible hinge 18 and the second flexible hinge 19 of the sensing layer, a controllable relative displacement relationship can be formed between the first movable electrode 14 and the second movable electrode 15 of the sensing layer during loading. The position sensor mounting area 16 and the second position sensor mounting area 17 are provided in the internal region of the sensing layer frame 13. Position sensor mounting area 16 is located near the slit area between sensor layer moving electrode 14 and sensor layer moving electrode 2 15, and is used to mount a position sensor so that the position sensor can detect changes in the slit width in this area. Position sensor mounting area 2 17 is also located near the slit area on the other side, and is used to mount another position sensor to detect changes in the slit width in another position area.

[0038] The lever rotation end 21 is connected to the displacement application and sensor layer via a connecting beam or an integrated force transmission structure. The connecting beam is connected to the first sensor layer moving pole 14 and the second sensor layer moving pole 15, respectively, so that the displacement output by the lever rotation end 21 can be synchronously transmitted to the two sensor layer moving poles. The two sensor layer moving poles are preferably symmetrically arranged, and their displacement changes jointly characterize the actual displacement state applied to the sensor layer. The control system obtains a unified displacement change based on the average, weighted average, or differential calculation results of the output signals from the two position sensors, and uses this displacement change as a displacement feedback signal to participate in subsequent closed-loop control.

[0039] In actual operation, when the uniaxial strain gauge applies displacement to the sample, the displacement is transmitted step by step through the device structure to the displacement application and sensor layers. This causes the moving poles 14 and 15 of the sensing layer to undergo minute displacements under the elastic constraints of their respective flexible hinges 18 and 19. As the relative positions of the moving poles 14 and 15 change, the width of the slit formed between them also changes. Position sensors installed in the position sensor mounting areas 16 and 17 detect this change in slit width in real time and output the detected displacement change signal to the control system to characterize the displacement changes during loading. This structural design allows for high-precision detection of displacement changes while the device applies strain, thus providing reliable feedback data for closed-loop uniaxial strain loading control.

[0040] like Figure 6 The diagram shows a schematic of the lever layer involved in this embodiment. This structure is used to realize displacement transmission and displacement ratio adjustment in a closed-loop uniaxial strain testing device, enabling the driving displacement generated by the piezoelectric driving layer to be effectively transmitted to the displacement application and sensor layer, thereby achieving strain control at the sample loading end. The lever layer mainly includes a fixed lever end 20, a rotating lever end 21, and a flexible hinge at the lever fulcrum 22. The fixed lever end 20 serves as the connection structure between the lever layer and the piezoelectric driving layer, connecting with the fixed structure of the piezoelectric driving layer during device installation to form a stable force reference. During the driving process, the displacement change generated by the piezoelectric driving layer first acts on the fixed lever end 20 connected to it, causing a force change in the lever structure. Since the fixed lever end 20 maintains a stable connection with other structures in the device, this position forms a relatively stable support area in the overall structure. The rotating lever end 21 is located on one side of the fixed lever end 20 and is connected to the fixed lever end 20 via the flexible hinge at the lever fulcrum 22. The lever fulcrum flexible hinge 22 is a partially thinned elastic connection structure disposed between the fixed end 20 and the rotating end 21 of the lever. It allows the rotating end 21 of the lever to undergo minute rotation or displacement changes relative to the fixed end 20 in a predetermined rotation direction, and provides constraint in non-predetermined directions to reduce lateral offset and vibration in irrelevant directions. This flexible hinge structure enables micro-displacement transmission and displacement ratio adjustment without the need for traditional mechanical hinges.

[0041] In actual operation, when the piezoelectric driving layer undergoes displacement, this displacement is first transmitted to the fixed end 20 of the lever, driving the lever structure. Under the elastic action of the flexible hinge 22 at the lever fulcrum, the rotating end 21 of the lever rotates or displaces around the position of the flexible hinge 22. Since the rotating end 21 of the lever is connected to the displacement application sensor layer, the displacement change of the rotating end 21 is further transmitted to the displacement application sensor layer, causing the moving structure in the displacement application sensor layer to produce a corresponding displacement. By setting up a lever structure, when the piezoelectric driving layer produces a small displacement, the displacement can be transmitted to the displacement application sensor layer through the lever transmission relationship. At the same time, according to the positional relationship of the flexible hinge 22 at the lever fulcrum in the structure, the displacement transmission ratio can be adjusted, thereby achieving control over the magnitude of the loaded displacement. This structure can ensure the stability of displacement transmission and achieve high-precision strain control in the closed-loop control process in conjunction with the feedback signal of the position sensor.

[0042] like Figure 7The diagram shows a schematic of the piezoelectric drive layer according to this embodiment of the invention. This structure is used to generate a controllable drive displacement in a closed-loop uniaxial strain testing device and transmit the drive displacement to the lever layer, which in turn transmits it to the displacement application and sensor layer, thereby achieving uniaxial strain loading on the sample to be tested in the transferable sample stage. The piezoelectric drive layer mainly includes a drive fixing base 23, a drive output end 24, a piezoelectric actuator 25, and a piezoelectric connecting bridge 26. The drive fixing base 23 serves as the reference support structure for the piezoelectric drive layer, used to fix one end of the piezoelectric actuator 25 and form a stable connection with the overall structure of the device. During device installation, the drive fixing base 23 remains fixed, thereby providing a stable installation reference for the piezoelectric actuator 25, enabling the piezoelectric actuator 25 to deform in a predetermined direction when a drive voltage is applied. The drive output end 24 is located on one side of the drive fixing base 23 and is connected to the drive fixing base 23 through the piezoelectric actuator 25. The drive output end 24 is used to receive the displacement change generated by the piezoelectric actuator 25 and transmit this displacement to the lever layer. During device operation, the drive output terminal 24 can generate displacement relative to the drive mounting base 23, thereby forming a drive displacement output. A piezoelectric actuator 25 is disposed between the drive mounting base 23, the drive output terminal 24, and the piezoelectric connecting bridge 26, and is used to generate axial expansion and contraction deformation under the action of a drive voltage. The piezoelectric connecting bridge 26 is used to connect multiple sets of piezoelectric actuators 25 and coordinate the transmission of deformation among the sets of piezoelectric actuators 25. Specifically, the piezoelectric connecting bridge 26 is disposed at one end of the multiple sets of piezoelectric actuators 25, and the other end of each set of piezoelectric actuators 25 is connected to either the drive mounting base 23 or the drive output terminal 24. Specifically, one end of the two outer sets of piezoelectric actuators 25 is connected to the drive mounting base 23, and the other end is connected to the piezoelectric connecting bridge 26; one end of the middle piezoelectric actuator 25 is connected to the drive output terminal 24, and the other end is connected to the piezoelectric connecting bridge 26. Thus, the piezoelectric connecting bridge 26 forms an indirect connection with the drive mounting base 23 and the drive output end 24 through each group of piezoelectric actuators 25, so that the expansion and contraction deformation generated by each group of piezoelectric actuators 25 can be coordinated through the piezoelectric connecting bridge 26 and stably transmitted to the drive output end 24, thereby improving the stability and consistency of the drive displacement output.

[0043] In actual operation, when a driving voltage is applied to the piezoelectric actuator 25, the actuator 25 undergoes elongation or contraction deformation in the direction of the arrow. This deformation is transmitted to the drive output end 24 through the piezoelectric connecting bridge 26, causing the drive output end 24 to displace relative to the drive fixing base 23. This displacement change is then transmitted through the lever layer to the displacement application sensor layer, causing the moving structure in the displacement application sensor layer to produce a corresponding displacement, and finally transmitted to the sample loading end in the transferable sample stage, thereby causing uniaxial strain loading on the sample to be tested, which is fixed between the sample fixing end and the sample loading end. The fine displacement drive generated by the piezoelectric drive layer can achieve high-precision adjustment of the sample deformation and form a closed-loop control process in conjunction with the position sensor detection signal.

[0044] Before starting the uniaxial strain loading test, it is necessary to first install the sample to be tested and connect all measurement circuits, and obtain the basic measurement signals before loading begins. The specific process is as follows: Obtain the sample identification information and geometric parameter information of the sample to be tested. The sample to be tested has already been fixed on the transferable sample holder and prefabricated during the sample preparation stage. Therefore, before loading it into the uniaxial strain loading device, it is necessary to read the sample number corresponding to the transferable sample holder and record the correspondence between the sample number and the sample type. At the same time, the geometric parameters of the sample are recorded, including dimensional information such as sample length, sample width, and sample thickness. Geometric parameters can be obtained through vernier calipers, microscopic measuring devices, or sample preparation record data, and this information, along with the sample identification information, is written into the test record table for subsequent use in the calculation of strain and stress values.

[0045] In this embodiment, the sample to be tested can be selected from different types of materials or device structures according to the research object and experimental purpose. However, in general, it needs to be a functional material that can withstand controllable deformation in a single direction and exhibit electrical or physical property changes under uniaxial strain conditions. To facilitate experimental operation, the material is usually processed into a sample structure with a certain length direction during sample preparation, and both ends of the sample are fixed between the sample fixing end 10 and the sample loading end 11, so that the sample can generate strain values ​​along the axial direction when the sample loading end 11 is displaced.

[0046] Specifically, the sample to be tested can include the following typical material samples: When studying the properties of quantum materials, the sample to be tested can be a single crystal sample of iron-based superconducting material, such as Ba(Fe)₂. 1-x Co x)2As2 single crystal sample. During sample preparation, the single crystal material is cut into a thin strip structure, and both ends of the sample are polished. Then, the two ends of the sample are fixed between the sample fixing end 10 and the sample loading end 11. The electrical measurement circuit is connected through the wiring area 6, and the change in resistance or conductance of the sample is measured when uniaxial strain is applied. When studying unconventional superconducting materials, the sample to be tested can be a Sr2RuO4 single crystal sample. By processing the sample into a thin sheet or strip structure with a certain length direction, and fixing both ends of the sample between the sample fixing end 10 and the sample loading end 11, the resistance change data is obtained through the electrical measurement circuit during uniaxial strain loading to analyze the effect of strain value on superconducting transition temperature. When studying copper oxide high-temperature superconducting materials, the sample to be tested can be YBa2Cu3O 6+x Single-crystal samples. By fabricating the sample into a long strip structure and mounting it on a transferable sample stage 8, the electrical response signal is acquired through electrical measurement circuitry when uniaxial strain is applied, thereby studying the relationship between charge density wave structure and superconducting state. When studying the strain modulation effect of two-dimensional materials, the sample to be tested can be a graphene sample or a CrSBr layered material sample. During sample preparation, the two-dimensional material is transferred onto a substrate material, and electrode structures are formed at both ends of the material. Then, the substrate material is fixed between the sample fixing end 10 and the sample loading end 11, and the electrical measurement circuitry is connected through the wiring area 6. The electrical response signal of the material is acquired during uniaxial strain loading. In addition, in some experimental studies, the sample to be tested can also be a functional device sample with micro / nano structures, such as microelectronic devices or sensor structures based on two-dimensional materials. By fabricating the substrate on which the device is located into a structure with a certain length direction, and fixing both ends of the substrate between the sample fixing end 10 and the sample loading end 11, the electrical signal change of the device is acquired through the wiring area 6 during uniaxial strain loading.

[0047] In actual sample installation, one end of the sample is fixed to the sample fixing end 10, and the other end is fixed to the sample loading end 11, placing the sample between the sample fixing end 10 and the sample loading end 11. When the external loading structure applies displacement to the sample loading end 11, the sample loading end 11 undergoes displacement along the loading direction under the elastic constraint of the sample holder flexible hinge 12. This displacement is transmitted to the sample under test through the sample loading end 11, thereby generating uniaxial strain between the two ends of the sample. By setting the sample holder flexible hinge 12, controllable displacement of the sample loading end 11 can be achieved while ensuring structural stability, enabling the transferable sample holder to stably complete the sample installation and strain loading process under different test conditions.

[0048] In this embodiment, the sample to be tested is prefabricated by the test personnel during the sample preparation stage, fixed on the transferable sample holder. This prefabrication process is carried out in a separate sample preparation environment to reduce the time occupied by the test equipment and ensure the quality of sample installation. The specific steps are as follows: Prepare the transferable sample holder, and the test personnel perform a structural inspection on the sample holder frame 9, the sample fixing end 10, the sample loading end 11, and the sample holder flexible hinge 12. The inspection includes whether the sample holder frame 9 is deformed, whether the connection between the sample fixing end 10 and the sample holder frame 9 is firm, whether the sample loading end 11 can produce a small elastic displacement under the constraint of the sample holder flexible hinge 12, and whether the sample holder flexible hinge 12 has cracks or abnormal bending. The elastic state of the sample holder flexible hinge 12 is judged by gently pushing the sample loading end 11 and observing its rebound. When the sample loading end 11 can return to its initial position after the external force is released, the sample holder flexible hinge 12 is considered to be in normal working condition.

[0049] Verify the dimensions of the sample to be tested and record the sample identification information. Read the sample number and measure at least the length, width, and thickness of the sample. Record the measured data along with the sample identification information. After measurement, check if the end faces of the sample are flat. If there are obvious tilts or burrs, treat the end faces by grinding or trimming to ensure that the end faces are basically perpendicular to the sample axis, thus ensuring uniform stress during subsequent loading.

[0050] After inspecting the sample to be tested, install it into the transferable sample holder. Specifically, first place one end of the sample to be tested at the mounting position of the sample fixing end 10, ensuring the axis of the sample is aligned with the movement direction of the sample loading end 11. Then, fix one end of the sample to be tested onto the sample fixing end 10. After fixing, check whether the sample to be tested can be stably held in the mounting position of the sample fixing end 10 to prevent loosening during subsequent operations. After fixing one end of the sample to be tested, connect the other end of the sample to the sample loading end 11. Place the other end of the sample to be tested at the mounting position of the sample loading end 11 and fix it onto the sample loading end 11 using the same clamping structure or adhesive method, ensuring a stable connection between both ends of the sample to the sample fixing end 10 and the sample loading end 11. After connection, check again whether the sample to be tested is centered between the sample fixing end 10 and the sample loading end 11, and observe whether the axis of the sample to be tested is basically aligned with the loading direction.

[0051] Confirm the installation status of the sample to be tested. Slightly push the sample loading end 11 and observe the response of the sample to determine if it can move synchronously with the sample loading end 11. If the sample can move slightly with the sample loading end 11 without significant loosening, it indicates that the sample has formed a stable connection with the sample fixing end 10 and the sample loading end 11. If slippage or displacement occurs, readjust the position of the sample and fix it again.

[0052] After confirming the stability of the sample to be tested, record the number of the current transferable sample holder and establish a correspondence between the sample holder number and the identification information of the sample to be tested. After completing the above steps, save the transferable sample holder with the sample fixed as a whole structure, and directly install it into the uniaxial strain loading device for uniaxial strain loading test in the subsequent testing stage. By completing the fixing operation between the sample to be tested and the transferable sample holder in advance during the sample preparation stage, the installation time in the testing stage can be reduced, the testing efficiency can be improved, and the impact of sample installation errors on the test results can be reduced.

[0053] The tester installs the transferable sample stage 8, containing the sample to be tested, into the sample mounting area 5. During operation, the sample support frame 9 is aligned with the mounting position in the sample mounting area 5, ensuring that the sample support frame 9 fits snugly against the positioning structure of the sample mounting area 5. The sample support frame 9 is then fixed within the sample mounting area 5 using the fixing structure. After installation, it is observed whether the transferable sample stage 8 forms a stable connection with the sample mounting area 5, and whether the sample support frame 9 is tilted or offset. If a positional deviation is found, the position of the transferable sample stage 8 is finely adjusted to ensure that the sample support frame 9 remains stably centered within the sample mounting area 5. After installation, the sample loading end 11 is gently pushed, and it is observed whether the sample loading end 11 can produce a small displacement along the loading direction under the action of the sample support flexible hinge 12, confirming that the displacement of the sample loading end 11 is not interfered with by the structure of the sample mounting area 5.

[0054] After the transferable sample stage 8 is installed, the measurement circuit is connected. First, connect the signal line of the position measuring device in the wiring area 6, enabling the position measuring device to detect the displacement changes inside the uniaxial strain gauge 7. After connection, check that the terminals are secure and read the real-time data from the output of the position measuring device to confirm that the signal line is in a normal conductive state. Connect the electrical measurement circuit in the wiring area 6, forming an electrical connection between the electrical measurement circuit and the two ends of the sample under test, thereby enabling the acquisition of electrical measurement signals of the sample under test during strain loading. After connection, check again for any looseness at the terminals and confirm that there are no short circuits or poor contacts between the lines.

[0055] After wiring is completed, the initial measurement signal is read. Without applying external load displacement, displacement feedback data is first read using a position measuring device, and N sets of data are continuously read to observe displacement changes. The currently read displacement data is recorded as the initial displacement feedback signal. Subsequently, stress value data output by the stress value detection structure set in the sample loading path is read, and N sets of stress value data are continuously recorded. This read data is recorded as the initial stress feedback signal. Simultaneously, the current electrical signal of the sample under test is read through the electrical measurement circuit, and N sets of electrical data are continuously read. The reading results are recorded as the initial electrical measurement signal. In this embodiment, N in the N sets of data is a pre-set value in the database used to limit the amount of initial measurement signal read.

[0056] The displacement data in the initial displacement feedback signal is subtracted from the preset displacement threshold in the database, and the absolute value is taken to obtain the displacement variation amplitude. If the displacement variation amplitude is always within the preset displacement fluctuation range, the initial displacement feedback signal is considered to meet the validity condition. Similarly, the stress value data in the initial stress feedback signal is subtracted from the preset stress value threshold in the database, and the absolute value is taken to obtain the stress value variation amplitude. If the stress value variation amplitude is always within the preset stress value fluctuation range, the initial stress feedback signal is considered to meet the validity condition. Likewise, the electrical measurement data in the initial electrical measurement signal is subtracted from the corresponding preset electrical measurement data threshold in the database, and the absolute value is taken to obtain the electrical measurement data variation amplitude. If the electrical measurement data variation amplitude is always within the corresponding preset electrical measurement data fluctuation range, the initial electrical measurement signal is considered to meet the validity condition. The aforementioned displacement threshold, stress value threshold, and corresponding electrical measurement data threshold are reference thresholds pre-written into the database during the device calibration phase. They are obtained based on no-load test results, standard sample test results, or statistical analysis of historical valid test data, and are used to determine whether the initial measurement signal is within the allowable fluctuation range.

[0057] When the initial displacement feedback signal, initial stress feedback signal, and initial electrical measurement signal all meet the preset validity conditions, the currently recorded data of these three types of signals are saved as the initial load measurement signal, and the subsequent closed-loop uniaxial strain loading test process begins. If any of the initial displacement feedback signal, initial stress feedback signal, or initial electrical measurement signal does not meet the preset validity conditions, the connection status in wiring area 6 is rechecked, and the signal data is reread until all three types of signals meet the stability conditions before being recorded as the initial load measurement signal. This operation ensures that the uniaxial strain device 7 is in a stable working state before formal loading, thereby improving the reliability of the subsequent uniaxial strain test results under multiphysics conditions.

[0058] In this embodiment, the electrical measurement signals include at least one or more of the following: resistance signal, voltage signal, current signal, and impedance signal. During actual testing, the appropriate type of electrical measurement signal is selected for acquisition based on the research objective of the sample under test, and the measurement signal is transmitted to the host computer via the electrical measurement lines in wiring area 6.

[0059] After acquiring the initial loading measurement signal, it is necessary to establish the correspondence between the driving quantity and the actual strain or stress value of the sample before formal closed-loop control. This embodiment calculates the loading conversion parameters between the loading driving quantity and the strain or stress value at the sample end by performing a loading scan within a preset loading range and simultaneously acquiring displacement feedback signals, stress feedback signals, and electrical measurement signals. The specific operation process is as follows: After acquiring the initial loading measurement signal, a loading scan sequence is first generated based on the preset loading range and preset scan step size. During operation, the initial displacement feedback signal in the initial loading measurement signal is read, and this initial state is used as the scan starting point. Subsequently, a set of sequentially arranged driving voltage sequences is generated according to the experimentally set maximum loading range and scan step size. For example, starting from the initial driving value, the sequence gradually increases to the maximum driving value with a fixed scan step size, and then gradually reverts to the initial driving value according to the corresponding step size, thus forming a complete loading scan sequence. After generating the sequence, the corresponding driving voltage is output to the piezoelectric actuator in the uniaxial strain gauge according to the sequence order, causing the piezoelectric actuator to gradually generate the corresponding loading driving quantity.

[0060] Upon each load driving input output, the corresponding feedback signal is acquired after a stabilization waiting period. First, the displacement feedback signal output by the position sensor is read, and the current displacement value is recorded. Then, the stress feedback signal output by the stress detection structure located in the sample loading path is read, and this signal is recorded as the current stress value. Simultaneously, the electrical measurement signal of the sample under test is read through the electrical measurement circuit, and the corresponding electrical response data is recorded. All three signals are recorded using the current load driving input as an index, thus establishing a corresponding relationship.

[0061] After acquiring data corresponding to multiple sets of loading driving forces, the displacement change is calculated. First, the initial displacement feedback signal is read as the reference displacement value. Then, the displacement feedback signal recorded at each loading moment is subtracted from the initial displacement feedback signal to obtain the displacement change corresponding to each loading moment. After obtaining the displacement change, the strain value at the sample end is calculated based on the geometric parameters of the sample under test. The sample length recorded in the sample identification information is read, and then the displacement change is divided by the original sample length to obtain the strain value at the sample end. Simultaneously with the strain calculation, the stress value at the sample end is calculated. First, the stress value sensor output value recorded in the stress feedback signal is read to obtain the stress feedback signal recorded at each loading moment. Then, the sample cross-sectional area recorded in the sample geometric parameters is read. This cross-sectional area is obtained by multiplying the sample width and sample thickness. Then, according to the stress value calculation relationship, the stress feedback signal recorded at each loading moment is divided by the sample cross-sectional area to obtain the stress value at the sample end corresponding to each loading moment. After completing the above calculations, the loading driving force, sample end strain value, and sample end stress value at each loading moment are combined and recorded in chronological order. In specific operation, the data at each moment is stored in the form of a triplet. All records are arranged sequentially according to the loading scan order to form a complete loading scan data set. The stress value detection structure is set on the sample loading path, specifically at the sample loading end 11, the sample fixing end 10, or the force transmission connection structure between the two, to directly or indirectly detect the load applied to the sample in the axial direction. The measurement data output by the stress value detection structure serves as a stress feedback signal.

[0062] After obtaining the loading scan dataset, the relationship between the loading driving force and the sample strain value is calculated. First, the loading driving force and sample strain value data from all data records are read, and a data sequence is established with the loading driving force as the independent variable and the sample strain value as the dependent variable. Then, a linear fitting method is used to calculate the proportional relationship between the two. In this specific calculation, the coefficient k is solved using the least squares method. ε ,make The sum of squared errors is minimized, thus yielding the conversion parameter k between the loading driving amount and the strain value at the sample end. ε This is denoted as the strain value proportionality coefficient. Here, D represents the loading driving force, ε represents the strain value at the sample end, and c... ε This is the zero-point offset of the strain value.

[0063] The same method was used to calculate the relationship between the loading driving force and the sample end stress value. Loading driving force and sample end stress value data were read from the loading scan dataset. The loading driving force was used as the independent variable and the sample end stress value as the dependent variable. The solution coefficient k was calculated using the least squares method. σ ,make The sum of squared errors is minimized, thus yielding the conversion parameter k between the loading driving amount and the sample end stress value. σ This is denoted as the stress value proportionality coefficient. Here, D represents the loading driving force, σ represents the stress value at the sample end, and c... σ This is the zero-point offset of the stress value.

[0064] After completing the above calculations, the obtained strain value proportionality coefficient, strain value zero-point offset, stress value proportionality coefficient, and stress value zero-point offset are stored uniformly and recorded as loading conversion parameters. In the subsequent closed-loop loading control process, by reading these loading conversion parameters, the corresponding loading driving amount can be deduced from the target strain value or target stress value, thereby achieving precise control of the uniaxial strain loading process of the sample under test.

[0065] It should be noted that when determining the loading conversion parameters, either the loading driving force and the strain value at the sample end, or the loading driving force and the stress value at the sample end, can be calculated based on the testing requirements. These two types of loading conversion parameters are optional. In actual processing, based on the data type recorded in the loading scan data set, a data correspondence between the loading driving force and the strain value at the sample end, or between the loading driving force and the stress value at the sample end, is established, and the corresponding loading conversion parameters are calculated for use in the subsequent loading control process.

[0066] It should be explained that the zero-point offsets for strain and stress values ​​can be pre-set in the database and called during the loading and scanning calculation process. These offsets are used to correct the initial bias of the measurement system, thereby avoiding the influence of structural installation errors or sensor zero-point drift on subsequent calculation results. Specifically, during system initialization, the zero-point offsets for strain and stress values ​​are pre-stored in the database. These offsets can be set based on the calibration results of the device under different testing conditions, for example, calculated from baseline data collected by the device in an unloaded state, and the corresponding values ​​are written into the database to form bias parameter records. By pre-setting the zero-point offsets for strain and stress values ​​in the database and correcting the bias of the collected data during the calculation process, baseline errors caused by initial zero-point offset of the sensor, sample installation prestress values, or minor structural deformations of the device can be eliminated. This makes the loading conversion parameters between the loading drive and the actual strain or stress values ​​at the sample end more stable and reliable, thereby improving the accuracy of uniaxial strain test results under multiphysics conditions.

[0067] After determining the loading conversion parameters, uniaxial strain loading needs to be applied to the sample under test according to the loading target set in the experiment. This embodiment converts the target strain trajectory or target stress trajectory into a corresponding loading control sequence, and drives the uniaxial strain device step by step according to this loading control sequence, thereby achieving loading control of the sample under test. Simultaneously, displacement feedback signals, stress feedback signals, and electrical measurement signals are continuously acquired during the loading process. The specific operation process is as follows: The target loading trajectory set in the experiment is read. This target loading trajectory can be either a target strain trajectory or a target stress trajectory. After reading, the target loading trajectory is time-discretely processed. During operation, the target loading trajectory is first sampled according to a preset uniform time step. If the target loading trajectory is a continuous function, the corresponding target value is calculated at each sampling time node; when the target loading trajectory is existing discrete data, each data point and corresponding time information in the target loading trajectory is first read and sorted according to chronological order. Then, a uniform time step is set, and a new time-interval sequence is generated based on the start and end times of the target loading trajectory. For each new time node, find the two closest time nodes in the original data sequence and read the corresponding target values. Based on the position of this time node between the two original time nodes, calculate the ratio between the two target values ​​to obtain the target value corresponding to this time node. Repeat this process for all time nodes to ensure that each time node corresponds to a target value. This process results in a target loading sequence arranged with a uniform time step, maintaining consistent time intervals between adjacent data points.

[0068] This process yields a target loading sequence arranged chronologically, with each sampling time point corresponding to a target strain or stress value. The target loading sequence is then converted into a corresponding loading drive sequence based on loading conversion parameters. If the target loading trajectory is a target strain trajectory, the strain value scaling factor and strain value zero-point offset are read from the loading conversion parameters. Let the target strain value be ε. i The strain value proportionality coefficient is k ε The zero-point offset of the strain value is c ε The corresponding load driver quantity is then calculated through reverse conversion: ; Among them, D i This refers to the load driver quantity corresponding to the i-th sampling time point, where i is the number of the sampling time point. , where n is the number of sampling time points.

[0069] If the target loading trajectory is the target stress trajectory, then read the stress value scaling factor and stress value zero-point offset from the loading conversion parameters. Let the target stress value be σ.i The stress value proportionality coefficient is k σ The zero-point offset of the stress value is c. σ The load driver quantity is then calculated as follows: ; Among them, D i This refers to the load driver value corresponding to the i-th sampling time point, where i is the number of the sampling time point. , where n is the number of sampling time points.

[0070] Through the above calculations, each target value in the target loading sequence is converted to generate a loading drive sequence arranged in chronological order.

[0071] After obtaining the loading drive sequence, the corresponding loading drive quantities are output to the uniaxial strain gauge step by step according to the sequence order. Specifically, the drive quantity corresponding to the current time node is converted into a corresponding drive voltage and output to the piezoelectric actuator, causing the piezoelectric actuator to produce the corresponding deformation. This displacement is then applied to the sensor layer through the lever layer and displacement layer, transmitting the displacement to the sample loading end in the transferable sample stage, causing the sample to produce the corresponding uniaxial strain. After each drive quantity output, a stable waiting time is maintained to allow the device structure to reach a stable state before proceeding to the next time node. Specifically, the loading drive quantity corresponding to the current time node is read. The loading drive quantity represents the drive displacement to be generated by the piezoelectric actuator, which needs to be converted into a drive voltage that the piezoelectric actuator can execute before being output. The calibration parameters of the piezoelectric actuator are read from the database. These calibration parameters are obtained experimentally and pre-stored during the device calibration phase, and are used to describe the correspondence between the piezoelectric actuator drive voltage and the generated displacement. The calibration parameters include the piezoelectric displacement proportionality coefficient and the drive voltage zero-point offset, where the piezoelectric displacement proportionality coefficient represents the displacement change that can be generated by a unit drive voltage. Dividing the applied driving force by the piezoelectric displacement proportionality coefficient yields the voltage change corresponding to the displacement change. This voltage change is then superimposed with the zero-point offset of the driving voltage to obtain the driving voltage value at the current time point. This calculation process converts the required driving displacement into the corresponding driving voltage.

[0072] After obtaining the driving voltage, the calculated result needs to be checked for voltage range. First, the allowable driving voltage range of the piezoelectric actuator is read, which includes the minimum and maximum driving voltages. Then, the calculated driving voltage is compared with the allowable range. When the calculated driving voltage is less than the preset minimum driving voltage, the driving voltage is adjusted to the minimum driving voltage; when the calculated driving voltage is greater than the preset maximum driving voltage, the driving voltage is adjusted to the maximum driving voltage; when the driving voltage is within the allowable range, the calculation result remains unchanged. After completing the driving voltage calculation and range verification, the driving voltage is output as a control signal to the piezoelectric actuator. Under the action of the driving voltage, the piezoelectric actuator generates a corresponding elongation or contraction displacement. This displacement is transmitted to the drive output end through the piezoelectric connecting bridge, and then transmitted to the displacement application and sensor layer through the lever layer, thereby causing the sample loading end in the transferable sample holder to generate a corresponding displacement, causing the sample to be tested to undergo uniaxial strain loading according to the target loading trajectory.

[0073] Within each load drive output cycle, feedback signals are simultaneously acquired. First, the displacement feedback signal output by the position sensor is read and the current displacement data is recorded. Then, the stress feedback signal output by the stress detection structure is read and the corresponding stress value data is recorded. Simultaneously, the electrical measurement signal of the sample under test is read through the electrical measurement circuit, and the electrical response data is recorded. While acquiring the above data, the timestamp of the current acquisition moment is also recorded to indicate the actual acquisition time corresponding to the data.

[0074] After each data acquisition, the current driving force, displacement feedback signal, stress feedback signal, electrical measurement signal, and timestamp are combined and recorded. Specifically, data at each moment is stored according to a unified data structure, and the data records are arranged sequentially by time to form a loading operation data sequence. During the loading control process, the above driving output and data acquisition steps are continuously repeated, and new data records are continuously appended to the loading operation data sequence. In this way, the correspondence between the loading driving force and various feedback signals can be recorded in real time throughout the entire uniaxial strain loading process, thus providing a complete data foundation for subsequent data analysis and closed-loop control adjustment.

[0075] After generating the loading control sequence and starting uniaxial strain loading, the loading process needs to be continuously adjusted based on feedback signals to ensure that the actual loading state of the sample follows the target loading trajectory. This embodiment calculates the difference between the target loading amount and the actual strain or stress value at the sample end, and dynamically adjusts the loading drive based on this difference to achieve closed-loop loading control. The specific operation process is as follows: During the uniaxial strain test, data is first read according to a pre-set sampling period. The sampling period can be set according to experimental requirements, for example, sampling at fixed time intervals. At each sampling moment, the target loading amount corresponding to the current time node is read from the loading operation data sequence, and simultaneously, the currently acquired displacement feedback signal and stress feedback signal are read. The displacement feedback signal comes from the detection data corresponding to the position sensor, and the stress feedback signal comes from the measurement data of the stress value detection structure.

[0076] After receiving the feedback signal, the actual load value at the sample end is calculated based on the loading conversion parameters. When using strain control, the strain value proportionality coefficient and strain value zero-point offset in the loading conversion parameters are first read, and the actual strain value at the current sample end is calculated based on the displacement feedback signal. The currently acquired displacement feedback signal, the initial displacement reference value, and the sample length are obtained. The displacement change at the current moment is obtained by subtracting the initial displacement reference value from the currently acquired displacement feedback signal. The displacement change at the current moment is divided by the sample length to obtain the strain value at the sample end. The calculated strain value is then subtracted from the strain value zero-point offset to obtain the actual strain value at the sample end.

[0077] When using stress control, first read the stress feedback signal at the current moment, and then read the sample width and sample thickness from the sample geometry parameters. Divide the current stress feedback signal by the sample cross-sectional area obtained by multiplying the sample width and sample thickness to obtain the sample end stress value at the current moment. Subtract the zero-point offset of the stress value from the sample end stress value at the current moment to obtain the actual stress value at the sample end at the current moment.

[0078] After obtaining the actual strain or stress value at the sample end, this value is compared with the target loading amount corresponding to the current time point. If strain control is used, the target strain value is subtracted from the actual strain value to obtain the current loading control error; if stress control is used, the target stress value is subtracted from the actual stress value to obtain the current loading control error. After obtaining the loading control error, this error is input into the drive adjustment calculation process. Specifically, the drive adjustment amount is calculated based on the loading control error: the loading control error is multiplied by a proportional adjustment coefficient to obtain the drive adjustment amount. The proportional adjustment coefficient is determined based on the device calibration results, the piezoelectric actuator response characteristics, the sample type, and the target loading response speed and stability requirements. The drive adjustment amount is superimposed or subtracted from the current drive amount to obtain the updated loading drive amount, where the direction of increase or decrease is determined by the sign of the loading control error. After calculating the new loading drive quantity, this drive quantity is converted into a corresponding drive voltage and output to the piezoelectric actuator in the uniaxial strain gauge. This causes the piezoelectric actuator to generate a new drive displacement, which is then transmitted to the sample loading end in the transferable sample stage through the lever layer and displacement applied to the sensor layer. This causes the strain state of the sample to move closer to the target loading trajectory. The proportional adjustment coefficient can be calibrated through pre-testing before the test begins. Specifically, a closed-loop loading test is performed under different proportional adjustment coefficients. The time required to reach the target loading quantity, the steady-state error, and whether oscillations or overshoot occur are compared. When the preset response speed is reached, the steady-state error meets the requirements, and there is no obvious oscillation or overshoot, the corresponding proportional adjustment coefficient is determined as the proportional adjustment coefficient used under the current test conditions.

[0079] After each update of the driving force, feedback signals are continuously acquired, and relevant data at the current moment is written into the loading operation data sequence. Specifically, the written data includes the target loading amount at the current time point, the calculated loading control error, the updated loading driving force, and the synchronously acquired displacement feedback signals, stress feedback signals, and electrical measurement signals. All data is recorded in chronological order, forming a continuously updated loading operation data sequence. By repeatedly performing the above data reading, error calculation, and driving adjustment process, a closed-loop control structure is formed in the loading control process, thereby gradually bringing the actual loading state of the sample under test closer to the target loading trajectory.

[0080] During uniaxial strain testing, to determine whether the loading conversion parameters can still accurately reflect the correspondence between the loading driving amount and the actual strain or stress value at the sample end under the current test conditions, it is necessary to simultaneously analyze the displacement feedback signal, stress feedback signal, and electrical measurement signal during loading, and to determine the validity of the loading conversion parameters through the calculated feedback characteristic quantities. The specific operation process is as follows: During the test operation, signals are read according to a pre-set sampling period. In this embodiment, it is preferable to simultaneously read the displacement feedback signal, stress feedback signal, and electrical measurement signal acquired at the current moment at the arrival of each sampling period, and record the signals corresponding to each sampling period in chronological order, forming a displacement feedback signal sequence, a stress feedback signal sequence, and an electrical measurement signal sequence. As the sampling period progresses, the number of data points in the three signal sequences gradually increases, thus forming continuous time series data. After obtaining each signal sequence, the change in each sequence is calculated. Specifically, the signal values ​​of adjacent sampling periods are calculated using a difference operation to obtain the signal change. For example, in the j-th sampling period, where j = 1, 2, ..., m, j is the sampling period number and m is the number of sampling periods, the sampled value of the current sampling period is subtracted from the corresponding sampled value of the previous sampling period to obtain the corresponding change. By sequentially calculating the differences between each sampling period, the displacement change sequence, stress value change sequence, and electrical response change sequence can be obtained. Feedback characteristic quantities are then calculated. Specifically, the maximum and minimum values ​​in the change sequence are read within the current analysis time window, and the difference between the maximum and minimum values ​​is calculated to obtain the change amplitude. The change between two adjacent sampling periods is divided by the corresponding time interval to obtain the change rate per unit time. The change rate within each time interval can be further averaged to obtain the change rate characteristic quantity. The change sequence within the current time window is read and its average value is calculated. Then, the difference between each change and the average value is squared and averaged. Finally, the square root of the average value is calculated to obtain the signal fluctuation characteristic quantity.

[0081] While calculating the feedback characteristic quantities, the currently acquired displacement feedback signal or stress feedback signal is converted and calculated according to the loading conversion parameters. When strain control is used, the strain value at the sample end is calculated based on the displacement feedback signal; when stress control is used, the stress value at the sample end is calculated based on the stress feedback signal. Subsequently, following the same method as the aforementioned change quantity calculation, the difference between the strain value or stress value at the sample end of adjacent sampling periods is calculated to obtain the loading response change sequence.

[0082] After obtaining the feedback characteristic quantities and the loading response change sequence, corresponding matching processing is performed on the two types of data. Specifically, data from the displacement change sequence, stress value change sequence, electrical response change sequence, and loading response change sequence are read within the same time window and aligned according to the same time index. Then, the difference between each feedback characteristic quantity and the loading response change sequence is calculated, and the corresponding characteristic deviation is obtained through difference calculation. The absolute value of the difference between the displacement change amplitude characteristic quantity and the change amplitude in the loading response change sequence is used to obtain the displacement amplitude deviation; the absolute value of the difference between the change rate characteristic quantity and the loading response change rate is used to obtain the rate deviation; and the absolute value of the difference between the signal fluctuation characteristic quantity and the loading response fluctuation characteristic quantity is used to obtain the fluctuation deviation. Multiple characteristic deviations can be obtained through the above calculations. After obtaining each characteristic deviation, a threshold comparison calculation is performed on each deviation. Specifically, a pre-set judgment threshold is first read, and each characteristic deviation is divided by its corresponding judgment threshold to obtain the deviation ratio of each characteristic deviation. When the deviation ratio of a certain characteristic deviation is greater than or equal to 1, it indicates that the characteristic deviation has reached or exceeded the allowable range, and the deviation value corresponding to that characteristic is recorded as 1. When the deviation ratio is less than 1, it indicates that the characteristic deviation is still within the allowable range, and the deviation value corresponding to that characteristic is recorded as 0. The deviation values ​​corresponding to all characteristics are accumulated to obtain the cumulative deviation value. Then, a pre-set cumulative deviation threshold is read. When the cumulative deviation value is greater than or equal to the cumulative deviation threshold, it indicates that multiple feedback characteristics have deviated significantly, indicating that the loading conversion parameter between the loading driving quantity and the actual strain or stress value at the sample end has changed. At this time, the validity judgment result of the loading conversion parameter is recorded as loading conversion parameter failure. When the cumulative deviation value is less than the cumulative deviation threshold, it indicates that the feedback characteristic is still consistent with the loading response, and the validity judgment result of the loading conversion parameter is recorded as loading conversion parameter validity, and the current test process continues. Through the above continuous calculation process, the applicable status of the loading conversion parameter can be dynamically monitored during the test, thereby providing a judgment basis for the subsequent loading control process. The aforementioned preset judgment threshold is determined based on the statistical distribution of each feedback feature quantity under normal loading conditions, preferably using the mean and standard deviation of the corresponding feature deviation quantities in multiple repeated loading experiments; the cumulative deviation threshold is determined based on the degree of influence on the stability of the loading conversion parameters when multiple feature deviations exceed the limit simultaneously, preferably obtained through pre-experiment calibration.

[0083] During uniaxial strain testing, when the failure of the loading conversion parameter is determined through feedback characteristic analysis, the current loading process needs to be paused, and the correspondence between the loading drive quantity and the actual strain or stress value at the sample end needs to be re-established by re-executing the loading scan. The specific execution process is as follows: During continuous operation of the testing system, when the validity determination result indicates that the loading conversion parameter has failed, a pause control command is immediately sent to the uniaxial strain device, causing the piezoelectric actuator to stop outputting new drive voltages while maintaining the current drive state. Simultaneously with sending the pause command, the loading drive quantity corresponding to the current time point is read and recorded as the current loading state for use as a reference starting value when regenerating the loading scan range. After pausing loading, the cumulative deviation value obtained from the previous stage and the pre-set cumulative deviation threshold are read. The absolute value of the difference between the cumulative deviation value and the cumulative deviation threshold is taken to obtain the loading scan drive deviation value. The loading scan drive deviation value reflects the degree to which the current loading conversion parameter deviates from the normal state; a larger loading scan drive deviation value indicates a more significant deviation. The scan range and scan step size for re-executing the load scan are determined based on the load scan drive deviation value. Specifically, the load drive quantity recorded during pause is used as the scan center value. The load scan drive deviation value is used as the lookup key to extract the corresponding scan extension value from the pre-defined load scan drive deviation value-scan extension value mapping table in the database. This scan extension value is then added to both the upper and lower sides of the scan center value to obtain the new load scan range. Simultaneously, the load scan drive deviation value is used as the lookup key to extract the corresponding scan step size from the pre-defined load scan drive deviation value-scan step size mapping table in the database. When the load scan drive deviation value is large, the scan range is appropriately increased and the scan step size is decreased to improve the accuracy of the recalibration of the load conversion parameters.

[0084] After obtaining the updated loading scan range and the updated loading scan step size, a new loading scan sequence is generated based on these parameters. Specifically, the lower limit of the updated loading scan range is used as the starting scan point, and a sequence of sequentially arranged loading drive values ​​is generated by progressively increasing the updated loading scan step size until the scan value reaches the upper limit of the updated loading scan range, thus obtaining a complete loading scan sequence. After generating the loading scan sequence, the corresponding loading drive values ​​are output to the uniaxial strain gauge according to this sequence. At each output of the loading drive value, displacement feedback signals, stress feedback signals, and electrical measurement signals are simultaneously acquired, and the current drive value and corresponding feedback signals are recorded in chronological order. As the scan sequence is executed, a new set of loading scan data is obtained and stored in chronological order, forming an updated loading scan data set. After completing the rescan and obtaining the updated loading scan data set, the correspondence between the loading drive value and the actual strain or stress value at the sample end is recalculated based on the new scan data. In the specific calculation, each loading drive quantity and its corresponding displacement feedback signal or stress feedback signal are read from the updated loading scan data set, and the strain value or stress value at the sample end is calculated according to the aforementioned loading scan data processing procedure. Then, based on the relationship between the loading drive quantity and the corresponding strain or stress value, the proportionality coefficient and zero-point offset are recalculated to obtain the updated loading conversion parameters. After obtaining the updated loading conversion parameters, the new loading conversion parameters are written into the loading operation data sequence to replace the original loading conversion parameters. Then, based on the updated loading conversion parameters, the loading drive quantity sequence corresponding to the target loading quantity is recalculated, and a new loading control sequence is generated accordingly. After generating the new loading control sequence, the drive control signal continues to be output to the uniaxial strain gauge, and the closed-loop uniaxial strain loading test process is re-entered, thus enabling the test process to continue to operate stably under the new loading conversion parameters.

[0085] This invention also provides a closed-loop uniaxial strain testing system under multiphysics conditions, such as... Figure 8 The diagram shown is a system architecture diagram of a closed-loop uniaxial strain testing system under multiphysics conditions, including a measurement module and a control system.

[0086] The measurement module is used to apply uniaxial strain loading to the sample under test in a multi-physics environment and to acquire displacement feedback signals, stress feedback signals and electrical measurement signals during the loading process. It includes a cryogenic measurement end, a rod and a room temperature terminal.

[0087] The cryogenic measurement end is used to mount the sample to be tested in a cryogenic or magnetic field environment and apply uniaxial strain loading.

[0088] The rod is used to transfer the applied displacement to the sample and the mechanical response at the sample end to the room temperature terminal.

[0089] Room temperature terminals are used to establish electrical connections between measurement signals and the control system.

[0090] The control system is used to perform loading scanning, loading control, and loading conversion parameter updates based on the acquired displacement feedback signals, stress feedback signals, and electrical measurement signals, and to perform closed-loop control of the uniaxial strain loading process. It includes a closed-loop piezoelectric control system, an electrical measurement system, and a host computer.

[0091] A closed-loop piezoelectric control system is used to output a drive voltage according to a load control sequence to drive a piezoelectric actuator to generate a load drive quantity.

[0092] The electrical measurement system is used to acquire electrical measurement signals of the sample under test during the loading process.

[0093] The host computer is used to calculate loading conversion parameters, generate loading control sequences, calculate loading control errors, determine the validity of loading conversion parameters, and regenerate loading scan sequences when loading conversion parameters fail, based on the collected displacement feedback signals, stress feedback signals, and electrical measurement signals.

[0094] Embodiment 2 of the present invention: Based on Embodiment 1, in order to further expand the system's measurement capability under multi-physics conditions, different types of additional measurement structures can be configured on the strain device to achieve coupled testing under temperature, magnetic field and microwave irradiation conditions.

[0095] The strain gauge structure at the low-temperature measurement end has pre-reserved sensor mounting positions, allowing for the installation of Hall effect sensors or thermometers depending on experimental requirements. For magnetic field-related experiments, a Hall effect sensor is installed near the sample on the strain gauge. The voltage signal output by the Hall effect sensor measures the magnetic field strength near the sample, and the signal is transmitted to the control system via a room-temperature terminal for acquisition and recording. For temperature-related experiments, a thermometer is installed near the sample on the strain gauge. The electrical signal output by the thermometer acquires the temperature data at the sample location in real time, and the temperature signal is transmitted to the control system via a room-temperature terminal. This allows for the simultaneous acquisition of temperature or magnetic field changes during uniaxial strain loading.

[0096] Embodiment 3 of the present invention: Based on Embodiment 1 or Embodiment 2, a microwave irradiation structure can also be installed on the strain device. A microwave antenna is installed near the cryogenic measurement end. By installing a microwave antenna on the strain device, external microwave signals are introduced to the cryogenic measurement end through a transmission line, and microwave signals are radiated to the sample under test through the microwave antenna. During uniaxial strain loading tests, the sample can be microwave irradiated simultaneously with strain loading, and the electrical measurement signals of the sample can be collected synchronously, thereby studying the coupling effect of microwave irradiation conditions and strain loading on the changes in sample properties.

[0097] With the above structural configuration, the strain gauge can further realize coupled testing under multiple physical field conditions such as temperature field, magnetic field and microwave irradiation, based on the first embodiment, thereby improving the system's application flexibility and scalability in material property research.

[0098] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A closed-loop uniaxial strain testing method under multiphysics conditions, characterized in that, The method includes: S1. Install the sample to be tested in the sample mounting area of ​​the closed-loop uniaxial strain testing device, and connect the position measuring device and the electrical measurement circuit to obtain the initial load measurement signal. S2. After receiving the initial loading measurement signal, apply a loading scan within the preset loading range to the sample to be tested, and simultaneously acquire displacement feedback signal, stress feedback signal and electrical measurement signal during the loading scan to determine the loading conversion parameter between the loading driving amount and the actual strain value or stress value at the sample end. S3. Convert the target strain trajectory or target stress trajectory into the corresponding loading control sequence according to the loading conversion parameters, and perform uniaxial strain loading on the sample to be tested according to the loading control sequence, while continuously acquiring displacement feedback signals, stress feedback signals and electrical measurement signals. S4. During the uniaxial strain test, the loading control error is calculated based on the target loading amount and the corresponding feedback signal. The target loading amount is the target strain value or the target stress value. The loading drive output is adjusted according to the loading control error so that the sample is loaded in a closed loop according to the target loading trajectory. S5. Simultaneously calculate the feedback characteristic quantity based on the displacement feedback signal, stress feedback signal and electrical measurement signal, and determine the validity of the loading conversion parameter between the loading driving quantity and the actual strain value or stress value at the sample end based on the feedback characteristic quantity. S6. When the validity determination result is that the loading conversion parameter is invalid, pause the current loading and reapply the loading scan to the sample to redetermine the loading conversion parameter, and then continue to perform the uniaxial strain loading test. S7. After the test is completed, output the loading trajectory and the corresponding electrical measurement signal.

2. The closed-loop uniaxial strain testing method under multiphysics conditions as described in claim 1, characterized in that, S1 specifically includes: Acquire the sample identification information and geometric parameter information of the sample to be tested, wherein the sample to be tested is a sample that has been pre-prepared and mounted on a transferable sample holder, and record the sample identification information and geometric parameter information; The sample to be tested, mounted on the transferable sample holder, is installed in the sample mounting area of ​​the closed-loop uniaxial strain testing device. After completing the wiring, read the initial displacement feedback signal, initial stress feedback signal, and initial electrical measurement signal; The initial displacement feedback signal, the initial stress feedback signal, and the initial electrical measurement signal are tested for validity. When the initial displacement feedback signal, the initial stress feedback signal, and the initial electrical measurement signal all meet the preset validity conditions, they are recorded as the initial loading measurement signal.

3. The closed-loop uniaxial strain testing method under multiphysics conditions as described in claim 1, characterized in that, S2 specifically includes: Upon receiving the initial loading measurement signal, a loading scan sequence within a preset loading range is generated, and the uniaxial strain loading device is controlled to gradually output the corresponding loading drive quantity according to the loading scan sequence. At each moment of load driving output, the displacement feedback signal, stress feedback signal and electrical measurement signal corresponding to each load driving quantity are synchronously collected and recorded. The corresponding displacement change is calculated based on the recorded loading driving amount and displacement feedback signal, and the strain value at the sample end is calculated based on the displacement change and the geometric parameters of the sample to be tested. The stress value at the end of the sample is calculated based on the recorded stress feedback signal and the geometric parameters of the sample under test. The loading driving amount, the strain value at the sample end and the stress value at the sample end are established in chronological order to form a corresponding data set, which is denoted as the loading scan data set. The conversion parameters between the loading driving amount and the strain value at the sample end, as well as the conversion parameters between the loading driving amount and the stress value at the sample end, are calculated based on the loading scan data set, and the conversion parameters are stored as loading conversion parameters.

4. The closed-loop uniaxial strain testing method under multiphysics conditions as described in claim 1, characterized in that, S3 specifically includes: Read the target strain trajectory or target stress trajectory, and discretize the target strain trajectory or target stress trajectory according to a preset time step to generate a target loading sequence arranged in time order; Based on the loading conversion parameters, each target strain value or target stress value in the target loading sequence is converted and calculated to generate a corresponding loading driving quantity sequence. According to the loading drive sequence, the corresponding loading drive quantity is output to the uniaxial strain loading device step by step to form a loading control sequence and drive the sample to be tested to perform uniaxial strain loading. Within each load drive output cycle, the displacement feedback signal, stress feedback signal, electrical measurement signal, and acquisition timestamp corresponding to each load drive are synchronously acquired and recorded. A loading operation data sequence containing loading drive quantity, displacement feedback signal, stress feedback signal and electrical measurement signal is established in chronological order, and the loading operation data sequence is continuously updated.

5. The closed-loop uniaxial strain testing method under multiphysics conditions as described in claim 1, characterized in that, S4 specifically includes: During the uniaxial strain test, the target loading amount, displacement feedback signal, and stress feedback signal at the current moment are read from the loading operation data sequence according to the preset sampling period; The displacement feedback signal or stress feedback signal is converted and calculated according to the loading conversion parameters to obtain the corresponding sample end strain value or sample end stress value. The loading control error is calculated based on the target loading amount and the strain value or stress value at the sample end. The loading control error is input into the loading drive adjustment calculation process to generate the corresponding drive adjustment amount, and the loading drive amount is updated according to the drive adjustment amount. The updated loading drive quantity is used to output the loading drive control signal to the uniaxial strain loading device, and the synchronous acquisition of displacement feedback signal, stress feedback signal and electrical measurement signal continues. The target loading amount, loading control error, updated loading drive amount, and corresponding displacement feedback signal, stress feedback signal, and electrical measurement signal are written into the loading operation data sequence.

6. The closed-loop uniaxial strain testing method under multiphysics conditions as described in claim 1, characterized in that, S5 specifically includes: Displacement feedback signals, stress feedback signals, and electrical measurement signals are read synchronously according to a preset sampling period, and the displacement feedback signal sequence, stress feedback signal sequence, and electrical measurement signal sequence for each sampling period are obtained with a preset sampling period step size. The displacement change sequence, stress value change sequence, and electrical response change sequence are calculated based on the displacement feedback signal sequence, stress feedback signal sequence, and electrical measurement signal sequence of each sampling period. The corresponding feedback characteristic quantities are calculated based on the displacement change sequence, stress value change sequence, and electrical response change sequence, respectively. The feedback characteristic quantities include at least the change amplitude characteristic quantity, the change rate characteristic quantity, and the signal fluctuation characteristic quantity. The displacement feedback signal or stress feedback signal is converted and calculated according to the loading conversion parameters to obtain the corresponding sample end strain value or sample end stress value, and the loading response change sequence is calculated according to the sample end strain value or sample end stress value. The feedback feature quantity is matched with the loading response change sequence, and the corresponding feature deviation is calculated. The feature deviation quantities are then statistically obtained. The validity determination result of the loading conversion parameter is generated by comparing the deviation of each feature with the corresponding judgment threshold. The determination threshold is obtained through pre-experimental calibration, statistical analysis of historical test data, or empirical setting based on sample type and test conditions.

7. The closed-loop uniaxial strain testing method under multiphysics conditions as described in claim 6, characterized in that, The specific process for determining the validity of the generated loading conversion parameters is as follows: Read the deviation of each feature and the corresponding preset judgment threshold, calculate the ratio of each feature deviation to the corresponding judgment threshold, and obtain the deviation ratio of each feature deviation. The deviation value corresponding to the characteristic deviation with a deviation ratio greater than or equal to 1 is recorded as 1, and the deviation value corresponding to the characteristic deviation with a deviation ratio less than 1 is recorded as 0. The cumulative deviation value is obtained by summing the deviation values ​​of each characteristic deviation. Read the preset cumulative deviation threshold. If the cumulative deviation value is greater than or equal to the cumulative deviation threshold, then record the validity determination result of loading the conversion parameter as the loading conversion parameter being invalid. If the cumulative deviation value is less than the cumulative deviation threshold, the validity determination result of the loaded conversion parameter is recorded as the loaded conversion parameter being valid.

8. The closed-loop uniaxial strain testing method under multiphysics conditions as described in claim 1, characterized in that, S6 specifically includes: Read the validity determination result. When the validity determination result indicates that the loading conversion parameter is invalid, send a pause control command to the uniaxial strain loading device and record the current loading drive quantity. Read the cumulative deviation value and the cumulative deviation threshold, calculate the deviation value between the cumulative deviation value and the cumulative deviation threshold, and record it as the load scan drive deviation value; The loading scan range and loading scan step size for reloading scan are determined based on the loading scan drive deviation value and recorded as the updated loading scan range and updated loading scan step size. A loading scan sequence is generated based on the updated loading scan range and the updated loading scan step size. The corresponding loading drive quantity is then output to the uniaxial strain loading device step by step according to the loading scan sequence. The loading scan process is then re-executed to obtain the loading scan data set corresponding to this updated loading scan, which is recorded as the updated loading scan data set. The updated loading conversion parameters are calculated based on the updated loading scan data set, and then written into the loading execution data sequence. The loading control sequence is regenerated based on the updated loading conversion parameters, and the uniaxial strain loading test continues.

9. A closed-loop uniaxial strain testing system under multiphysics field conditions, wherein the closed-loop uniaxial strain testing system under multiphysics field conditions is used to implement the closed-loop uniaxial strain testing method under multiphysics field conditions as described in any one of claims 1-8, characterized in that, The system includes: a measurement module and a control system; The measurement module is used to apply uniaxial strain loading to the sample under test in a multi-physics field environment and to collect displacement feedback signals, stress feedback signals and electrical measurement signals during the loading process. It includes a low-temperature measurement end, a rod and a room-temperature terminal. The low-temperature measurement end is used to mount the sample to be tested in a low-temperature or magnetic field environment and apply uniaxial strain loading. The rod is used to transfer the applied displacement to the sample under test and to transfer the mechanical response at the sample end to the room temperature terminal. The room temperature terminal is used to realize the electrical connection between the measurement signal and the control system; The control system is used to perform loading scanning, loading control and loading conversion parameter updates based on the collected displacement feedback signal, stress feedback signal and electrical measurement signal, and to perform closed-loop control of the uniaxial strain loading process, including a closed-loop piezoelectric control system, an electrical measurement system and a host computer. The closed-loop piezoelectric control system is used to output a driving voltage according to the loading control sequence to drive the piezoelectric actuator to generate a loading driving quantity. The electrical measurement system is used to acquire electrical measurement signals of the sample under test during the loading process; The host computer is used to calculate loading conversion parameters, generate loading control sequences, calculate loading control errors, determine the validity of loading conversion parameters, and regenerate loading scan sequences when loading conversion parameters fail, based on the collected displacement feedback signals, stress feedback signals, and electrical measurement signals.

10. A closed-loop uniaxial strain testing device under multiphysics conditions, wherein the closed-loop uniaxial strain testing under multiphysics conditions is used to implement the closed-loop uniaxial strain testing method under multiphysics conditions as described in any one of claims 1-8, characterized in that, The device includes a transferable sample holder, a displacement application and sensor layer, a lever layer, and a piezoelectric drive layer; The transferable sample holder includes a sample holder frame, a sample fixing end, a sample loading end, and a sample holder flexible hinge. The sample fixing end is fixedly connected to the sample holder frame, and the sample loading end is connected to the sample holder frame through the sample holder flexible hinge, so that the sample loading end can be displaced relative to the sample holder frame in a single direction. The two ends of the sample to be tested are respectively fixed between the sample fixing end and the sample loading end. The displacement applied to the sensor layer includes a sensor layer frame, a sensor layer movable pole one, a sensor layer movable pole two, a position sensor mounting area one, a position sensor mounting area two, a sensor layer flexible hinge one, and a sensor layer flexible hinge two. The sensor layer movable pole one is connected to the sensor layer frame through the sensor layer flexible hinge one, and the sensor layer movable pole two is connected to the sensor layer frame through the sensor layer flexible hinge two, so that the sensor layer movable pole one and the sensor layer movable pole two can generate elastic displacement relative to the sensor layer frame. Position sensors are installed in the position sensor mounting area one and the position sensor mounting area two on the sensor layer frame, respectively, to detect the change in the slit width between the sensor layer movable pole one and the sensor layer movable pole two, thereby obtaining the displacement change signal generated during the loading process. The lever layer includes a fixed end, a rotating end, and a flexible hinge at the lever fulcrum. The rotating end is connected to the fixed end via the flexible hinge at the lever fulcrum. The fixed end is connected to the piezoelectric drive layer. The rotating end is connected to the displacement application sensor layer. The drive displacement is transmitted to the displacement application sensor layer through the lever structure. The piezoelectric drive layer includes a drive base, a drive output end, a piezoelectric actuator, and a piezoelectric connecting bridge. The piezoelectric actuator is disposed between the drive base and the drive output end. When a drive voltage is applied, the piezoelectric actuator elongates or contracts, causing the drive output end to undergo displacement relative to the drive base. This displacement is then transmitted to the sensor layer through the lever layer, thereby driving the sample to be tested in the transferable sample holder to generate uniaxial strain loading.

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