An SMA wire material evaluation system and evaluation method simulating real application scenarios

Abstract

The present invention provides an SMA wire material evaluation system and method that simulates real-world application scenarios. This system utilizes a modular load-bearing structure, integrated with an environmental simulation cabin, a data acquisition module, and a control center. A dynamic constraint calculation unit analyzes wire material factory parameters and automatically sets load, temperature rise, and strain thresholds. An interlocking protection unit monitors load, temperature, and strain data in real time. When thresholds are exceeded, a load-temperature coordinated protection mechanism is triggered, simultaneously reducing the load and adjusting the heating power. A closed-loop control unit dynamically adjusts parameters based on stress relaxation characteristics and safety factor mapping tables stored in an adaptive database to ensure that the wire material's residual plastic strain is ≤0.1% and that the microstructure is free of phase transition defects during testing. This system significantly reduces testing equipment costs. Through dynamic threshold constraints and multi-parameter coordinated protection, it achieves high-precision testing while effectively avoiding damage to the wire material's performance, achieving both high efficiency and industrial practicality.

Description

Technical Field

[0001] The present invention relates to the technical field of shape memory alloy materials, and in particular to an SMA wire material evaluation system and evaluation method that simulates real application scenarios. Background Art

[0002] Shape memory alloy (SMA) wire, due to its unique shape memory effect and superelasticity, is widely used in aerospace, medical devices, robotics, and other fields. However, the stability of SMA wire's performance directly affects its reliability in actual working conditions. Although SMA wire products undergo relevant performance testing before shipment, most customers generally conduct spot checks on the SMA wire after receiving it. These tests examine key parameters such as phase transition temperature, strain, and force response to assess the SMA's performance and operational limits and ensure it meets actual usage requirements.

[0003] Currently, most of the equipment available on the market for SMA wire testing or evaluation is a general-purpose material tester that can be used to test the mechanical and thermodynamic properties of a variety of materials, including metals, polymers, and ceramics. Although this type of equipment is comprehensive, it has significant drawbacks:

[0004] 1. High cost: Due to the need to adapt to a variety of materials, the equipment integrates complex sensors, temperature control systems, and data analysis modules. The cost of a single unit is as high as US$300,000, far exceeding the affordability of small and medium-sized enterprises and R&D institutions.

[0005] 2. Functional redundancy: General-purpose equipment must take into account the testing requirements of multiple materials, resulting in a complex operating interface and cumbersome testing process. However, there is a lack of targeted optimization for the unique phase transformation behavior of SMA wire (such as martensite-austenite reverse transformation), resulting in insufficient testing accuracy and efficiency.

[0006] 3. Large size: To meet multifunctional requirements, the equipment usually occupies a large space and is difficult to adapt to the compact layout of production lines or laboratories, limiting its actual application scenarios.

[0007] One of the core technologies of the SMA drive system is self-feedback high-precision control. Establishing a control algorithm model requires obtaining the correlation or functional relationship between "temperature-resistance-displacement" under different loads and variable load modes (the physical structure of SMA lies in the functional relationship between "temperature-stress-strain"). Traditional SMA performance monitoring is basically measured in static mode (no load change). The phase change temperature / operating temperature obtained is significantly different from the actual application state and cannot guide practical applications.

[0008] It's important to note that the structures of existing SMA wire thermal training devices are very similar to the SMA wire evaluation system described herein. For example, patent application number CN202110475019.1, "A Shape Memory Alloy Wire Training Device," discloses a shape memory alloy wire training device for producing wires with a continuous shape and arbitrary length. The training device includes a base, a wire feed assembly, a pulley assembly, a wire take-up assembly, and a temperature control assembly. The base includes a vertically disposed mounting wall. The wire feed assembly includes a first reel mounted on the mounting wall and rotatable relative to the mounting wall, for winding a shape memory alloy wire. The pulley assembly includes a movable pulley located below the first reel, and the wire wound from the first reel can pass around the movable pulley from below, supported by the wire. The wire take-up assembly includes a second reel mounted on the mounting wall and rotatable relative to the mounting wall, located above the movable pulley, for winding the wire wound from the pulley assembly. The temperature control assembly is configured to control the temperature of the wire between the first and second reels, thereby inducing a phase change in the wire. The applicant has previously proposed a thermal training device for SMA wire. However, this type of shape memory alloy wire training device can directly affect the SMA wire during use, modifying the SMA wire. The SMA wire evaluation system of the present invention needs to completely avoid modification during use. Therefore, the SMA wire thermal training equipment involved in the prior art cannot be directly used as an SMA wire evaluation system.

[0009] Therefore, with the popularity of SMA wire in micro-drive devices and intelligent structures, the market urgently needs a specialized, low-cost, and high-efficiency evaluation system that can quickly and accurately detect the core performance parameters of SMA wire, while reducing equipment procurement and maintenance costs and ensuring that the equipment will not have any impact on the performance of the wire itself during the testing process. Summary of the Invention

[0010] The present invention aims to provide an SMA wire evaluation system and method that simulates real-world application scenarios. This dedicated evaluation system for SMA wires achieves low-cost, high-precision performance testing and evaluation through simplified structure and optimized temperature control and load design. Furthermore, it can simulate stress field control in real-world application scenarios. The evaluation method simulates real-world operating conditions using preset temperature curves and dynamic loads, collects data in real time, and compares it with standard parameters. This data then determines the SMA wire's "temperature-resistance-displacement" correlation parameters, providing effective parameters for the precise control of actual SMA devices / components. Most importantly, a compensation mechanism is incorporated throughout the entire testing and evaluation process, ensuring that the system serves solely as an SMA wire evaluation system and does not alter the performance of the memory alloy wire being tested.

[0011] To achieve the above objectives, the present invention proposes the following technical solutions:

[0012] An SMA wire evaluation system simulating a real-world application scenario includes a load-bearing structure having a wire clamp and a load application mechanism, wherein the wire clamp is configured to clamp one end of the SMA wire to be tested, and the load application mechanism is configured to apply a test load to the free end of the SMA wire; and an environmental simulation chamber covering the SMA wire testing area and equipped with a temperature control unit, further comprising:

[0013] a data acquisition module, comprising a displacement sensor, a force sensor, and a temperature sensor, for monitoring the strain, load response, and temperature data of the SMA wire, respectively;

[0014] Control Center, integrated:

[0015] Adaptive database, storing stress relaxation characteristic data of SMA wires of different specifications and safety factor mapping tables associated with their uses;

[0016] Dynamic constraint calculation unit, which automatically sets the maximum allowable load, critical temperature rise rate and strain threshold based on the factory performance specifications of the SMA wire;

[0017] A closed-loop control unit, which calls the stress relaxation characteristic data stored in the adaptive database to dynamically adjust the load and temperature parameters;

[0018] An interlock protection unit is configured to trigger a load-temperature coordinated protection mechanism when the real-time monitored load, temperature rise rate, or strain data exceeds a threshold value set by the dynamic constraint calculation unit;

[0019] The system ensures that the residual plastic strain of the SMA wire is ≤0.1% and the microstructure has no phase change-induced defects during the detection process through the coordinated action of the closed-loop control unit and the interlocking protection unit.

[0020] As a preferred technical solution of the present invention, the interlock protection unit performs the following operations:

[0021] Generate a load reduction curve and execute the unloading procedure. The load reduction rate is negatively correlated with the real-time temperature rise rate.

[0022] The temperature of the environmental simulation chamber is forcibly maintained in a stable range of 5-10°C above the end temperature of the austenite reverse phase transformation of the SMA wire for a duration of ≥120s;

[0023] When the temperature fluctuation in the environmental simulation cabin is greater than 5° C., a multi-stage cooling compensation program is started.

[0024] As a preferred technical solution of the present invention, the adaptive database includes:

[0025] Gradient safety factor table based on SMA wire diameter;

[0026] Phase transformation temperature-load correlation matrix based on SMA wire alloy composition;

[0027] The online learning module extracts features from the stress relaxation curve in each batch of test data and updates the stress relaxation model parameters every 24 hours.

[0028] As a preferred technical solution of the present invention, the bearing structure is provided with at least two groups of parallel distributed wire clamps and corresponding load applying mechanisms.

[0029] As a preferred technical solution of the present invention, the load applying mechanism includes:

[0030] Static loading module, which applies a constant load through a weight set;

[0031] Dynamic loading module supports sinusoidal wave loading, random vibration loading and multi-level step loading modes.

[0032] As a preferred technical solution of the present invention, the data acquisition module further includes a microstructure monitoring unit configured to obtain phase change grain ratio data of the SMA wire detection area in real time;

[0033] The control center also includes an abnormality detection unit, which is connected to the data acquisition module and the interlock protection unit via a bus communication and is configured as follows:

[0034] receiving stress and phase change grain ratio data from the data acquisition module in real time;

[0035] When any of the following situations is identified, an abnormal interrupt instruction is generated and sent to the interlock protection unit:

[0036] The proportion of microscopic phase transformation grains is greater than 2%;

[0037] The phase change hysteresis area exceeds ±15% of the benchmark value in the adaptive database;

[0038] Local strain concentration>150%;

[0039] The interlock protection unit triggers a load-temperature coordinated protection mechanism in response to the abnormal interruption instruction.

[0040] The present invention also provides an SMA wire material evaluation method simulating a real application scenario, comprising the following steps:

[0041] (1) Parameter preset: Analyze the factory performance description of the SMA wire to be tested, and set the maximum allowable load, critical temperature rise rate and strain threshold through the dynamic constraint calculation unit;

[0042] (2) Clamping preload: Fix the SMA wire to be tested in the wire clamp and apply preload force to eliminate the clamping gap;

[0043] (3) Closed-loop regulation detection:

[0044] a. Controlling the temperature of the environment simulation cabin according to a preset temperature curve, and applying a static or dynamic load through the load application mechanism;

[0045] b. The closed-loop control unit receives strain, load, and temperature data from the data acquisition module in real time and dynamically adjusts the output power of the load application mechanism and the heating power of the environmental simulation chamber to stabilize the detection parameters within the threshold range set by the dynamic constraint calculation unit;

[0046] (4) Collaborative protection triggering: When the interlock protection unit detects any of the following conditions, it will immediately terminate the detection and execute the protection action: the real-time load exceeds 95% of the maximum allowable load; the temperature rise rate exceeds 80% of the critical temperature rise rate; the strain deviation exceeds ±0.5% of the set threshold;

[0047] (5) Performance evaluation and verification: Compare the final strain recovery rate with the benchmark value in the adaptive database. When the strain recovery rate is ≥99%, the wire is judged to be qualified.

[0048] As a preferred technical solution of the present invention, the preset temperature curve in step (3) includes:

[0049] Initial stabilization stage: maintain at 20°C below the phase transition starting temperature for 60-120s;

[0050] Phase transition linear scanning stage: heating at a rate of 1-5°C / s to 10°C above the end of phase transition;

[0051] Cycle detection phase: Perform at least three complete phase change cycles.

[0052] As a preferred technical solution of the present invention, the situation in which the detection is immediately terminated in step (4) also includes: the proportion of microscopic phase transformation grains is identified to be greater than 2%; the area of ​​the phase transformation hysteresis loop exceeds ±15% of the reference value; the local strain concentration is greater than 150%;

[0053] The execution protection action includes: a gradient unloading program, a temperature maintenance program and a multi-stage cooling compensation program.

[0054] As a preferred technical solution of the present invention, after step (4), the following steps are performed:

[0055] Secondary verification: Reapply 50% of the rated load and verify that the strain recovery rate is ≥99.5%.

[0056] It can be seen from the above technical solutions that the technical solution of the present invention provides an SMA wire evaluation system and evaluation method that simulates real application scenarios. The detection device is specially designed, redundant functional modules in general equipment are deleted, and it is adapted to the compact layout of the production line; the detection process steps fully cover ISO / ASTM standards and can be directly used for SMA wire factory quality inspection and R&D verification; through modular design and replacement of domestic sensors, the total cost is reduced to less than US$50,000, and efficient and accurate detection of SMA wire is achieved, which is significantly better than existing general equipment and has outstanding industrial application value; the introduction of machine learning optimization thresholds, which is different from the traditional fixed threshold judgment method, improves detection accuracy; the parallel detection design of multiple wires adapts to the efficiency requirements of the production line and improves equipment utilization.

[0057] Furthermore, unlike existing wire testing equipment, the device disclosed herein offers significant advancements in that it uses a dynamic constraint calculation unit to analyze wire factory performance parameters (maximum allowable stress, phase transition temperature range) in real time. This, combined with a safety mapping table in an adaptive database (e.g., 1.8 for medical use and 1.2 for industrial use), dynamically sets the test threshold. Compared to traditional fixed threshold methods, the dynamic threshold ensures that the test load remains below the material's actual tolerance limit. This prevents overload damage caused by parameter missetting or external factors during the testing process, which can alter the wire's inherent properties and lead to material rejection during testing, resulting in undue cost losses. When the temperature rise rate or load fluctuation exceeds a certain threshold, an exponential load reduction curve is triggered in conjunction with gradient cooling, rapidly reducing the temperature to a safe range through rapid cooling compensation. By integrating dynamic threshold constraints, multi-level coordinated protection, and real-time microstructure monitoring, the present invention establishes a comprehensive damage prevention system that significantly reduces the risk of material damage while ensuring test accuracy. This system is particularly well-suited for the precision testing of high-value SMA wires.

[0058] It should be appreciated that all combinations of the foregoing concepts, as well as additional concepts described in greater detail below, to the extent such concepts are not mutually inconsistent, can be considered to be part of the inventive subject matter of this disclosure.

[0059] The foregoing and other aspects, embodiments, and features of the present invention will be more fully understood from the following description in conjunction with the accompanying drawings. Other additional aspects of the present invention, such as features and / or beneficial effects of the exemplary embodiments, will become apparent from the following description or through practice of specific embodiments according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] The accompanying drawings are not drawn to scale. In the accompanying drawings, each identical or nearly identical component shown in various figures may be represented by the same reference numeral. For clarity, not every component is labeled in every figure. Embodiments of various aspects of the present invention will now be described by way of example with reference to the accompanying drawings, in which:

[0061] Figure 1 Schematic diagram of the system structure of an embodiment of the present invention.

[0062] Figure 2 Schematic diagram of the austenite and martensite microstructure of the wire material according to Example 2 of the present invention;

[0063] Figure 3 Schematic diagram of the austenite and martensite microstructure of the wire material according to Example 3 of the present invention;

[0064] Figure 4 is the stress-strain curve of the wire material of Example 1 of the present invention;

[0065] Figure 5 is the stress-strain curve of the wire material of Example 2 of the present invention;

[0066] Figure 6 1 is the stress-strain curve of the wire material of Example 3 of the present invention.

[0067] The meanings of the accompanying drawings are as follows:

[0068] 100-Environmental simulation cabin, 200-Control center, 300-Base, 400-Fixed frame, 500-Wire clamp, 600-Load application mechanism, 700-SMA wire, 800-Force sensor. DETAILED DESCRIPTION

[0069] To further clarify the objectives, technical solutions, and advantages of the embodiments of the present invention, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only a portion of the embodiments of the present invention, not all of them. Based on the described embodiments of the present invention, all other embodiments derived by persons of ordinary skill in the art without requiring creative effort are within the scope of protection of the present invention. Unless otherwise defined, technical or scientific terms used herein shall have the ordinary meanings understood by persons of ordinary skill in the field to which the present invention pertains.

[0070] The terms "first," "second," and similar terms used in the patent specification and claims of this invention do not denote any order, quantity, or importance, but are merely used to distinguish different components. Similarly, unless the context clearly indicates otherwise, the singular forms of "a," "an," or "the" and similar terms do not denote a limitation of quantity, but rather denote the presence of at least one. Terms such as "include" or "comprising" indicate that the elements or objects preceding "include" or "comprising" encompass the features, integers, steps, operations, elements, and / or components listed after "include" or "comprising," and do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or combinations thereof. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0071] In order to solve the defects of existing testers that can be used for SMA wire performance testing, such as high cost, redundant functions, and large size, as well as the problem that wire performance damage cannot be effectively avoided during the testing process, an embodiment of the present invention provides an SMA wire evaluation system that simulates real application scenarios. The system can realize stress field control that simulates actual application scenarios, and obtain "temperature-resistance-displacement" related parameters on this basis, which can provide effective parameters for the precise control of actual SMA elements / devices. At the same time, the test threshold is dynamically set during testing so that the test load is always lower than the actual bearing limit of the material, avoiding overload damage caused by parameter missetting or external factors during the testing process, which may cause changes in the wire's own performance and lead to the scrapping of the wire during the testing process.

[0072] like Figure 1As shown, the present invention discloses an SMA wire evaluation system that simulates real application scenarios, including a load-bearing structure, an environmental simulation cabin 100, a data acquisition module and a control center 200. The load-bearing structure is provided with a base 300, a fixing frame 400, a wire clamp 500 and a load applying mechanism 600. The fixing frame 400 is vertically connected to the base 300. The wire clamp 500 is fixed to the upper end of the fixing frame 400 and is used to clamp one end of the SMA wire 700 to be tested. The wire hangs down under its own weight, and the load applying mechanism 600 is arranged at the end away from the wire clamp 500 (i.e., the free end of the wire) and applies a detection load.

[0073] The data acquisition module includes a displacement sensor, a force sensor 800, a temperature sensor, and a microstructure monitoring unit, each positioned at a corresponding location in the system. These sensors monitor the strain, load response, temperature, and phase-transformed grain ratio of the SMA wire 700. The displacement sensor, force sensor, and temperature sensor can all utilize existing technologies and are common knowledge to those skilled in the art. The microstructure monitoring unit is used to monitor microstructural changes (such as the phase-transformed grain ratio) in the SMA wire 700. It integrates an Olympus BX53M metallographic microscope and uses ImagePro Plus software to analyze the phase-transformed grain ratio in the SMA wire in real time to determine the martensite / austenite phase ratio. If the unexpected phase-transformed grain ratio exceeds 2% or the phase-transformation hysteresis area exceeds ±15% of the baseline value in the adaptive database, a level 3 alarm is triggered and a microstructure damage report is generated. Alternatively, surface morphology analysis of the SMA wire after testing can be performed using a micro-fiber spectrometer or scanning electron microscope. If no martensitic twins or dislocation accumulation are observed, the absence of phase-transformation-induced defects is determined.

[0074] Control center 200 is electrically connected to the data acquisition module and integrates an adaptive database, a dynamic constraint calculation unit, a closed-loop control unit, an anomaly detection unit, and an interlock protection unit. The adaptive database stores stress relaxation characteristic data for SMA wires of varying specifications (e.g., diameters of 0.02-2.0 mm) and a safety factor mapping table associated with each application. Specifically, a gradient safety factor table based on wire diameter is used, setting the safety factor for wires with diameters of 0.02-0.5 mm to 1.5-2.0, and for wires with diameters of 0.5 mm < d ≤ 2.0 mm to 1.2-1.5. A phase transition temperature-load correlation matrix, based on alloy compositions such as nickel-titanium, copper, and iron, is used to map the relationship between critical phase transition temperatures and allowable loads. An online learning module uses a time series analysis algorithm to extract features from the stress relaxation curves in each batch of test data, updating the stress relaxation model parameters every 24 hours.

[0075] The dynamic constraint calculation unit automatically sets the maximum allowable load, critical temperature rise rate, and strain threshold based on the factory performance specifications of the SMA wire 700, wherein the factory performance specifications include a phase transition temperature range, a maximum allowable stress, and a nominal stress recovery rate.

[0076] The system dynamically adjusts load and temperature parameters through a closed-loop control unit to ensure that the residual plastic strain of the SMA wire during testing is ≤0.1% and that the microstructure is free of phase transformation-induced defects. For example, the closed-loop control unit utilizes a PID algorithm to dynamically adjust the output power of the load application mechanism 600 and the heating power of the environmental simulation chamber 100 based on the deviation between real-time strain data and the target value, with a control cycle of ≤10ms.

[0077] The interlock protection unit is configured to trigger a load-temperature collaborative protection mechanism when the real-time monitored load, temperature rise rate, or strain data exceeds the threshold set by the dynamic constraint calculation unit. This load-temperature collaborative protection mechanism includes synchronously reducing the output power of the load application mechanism, the heating power of the environmental simulation chamber, and initiating a multi-stage cooling compensation program, such as semiconductor refrigeration plates and the injection of low-temperature inert gas. In short, the adaptive database provides a safety factor mapping table for the dynamic constraint calculation unit → the closed-loop control unit calls the stress relaxation model in the database → the interlock protection unit performs protection based on the output results of the closed-loop control unit. The adaptive database is a shared data source for each unit module. The dynamic constraint calculation unit sets the initial threshold before detection, the closed-loop control module continuously adjusts the parameters during detection, and the interlock unit engages protection when the threshold is exceeded. The three form a temporal logic chain of preset-adjustment-protection to control the system and prevent damage to the wire during the detection process.

[0078] The anomaly detection unit is communicatively connected to the closed-loop control unit and the interlock protection unit. It is configured to receive real-time strain concentration data from the data acquisition module and phase transformation grain ratio data from the microstructure monitoring unit. Upon identifying any of the following conditions, an anomaly interrupt command is generated and sent to the interlock protection unit: the microscopic phase transformation grain ratio is greater than 2%; the phase transformation hysteresis loop area exceeds ±15% of the reference value in the adaptive database; or the local strain concentration is greater than 150%. The interlock protection unit responds to the anomaly interrupt command and triggers the load-temperature coordinated protection mechanism. For example, the strain data required by the anomaly detection unit to detect local strain concentration is derived from the dynamic adjustment process of the data acquisition module and the closed-loop control module based on the adaptive database.

[0079] The interlocking protection unit triggers the load-temperature collaborative protection mechanism based on the thresholds of macroscopic parameters such as load, temperature, and strain, which is a hard protection; the anomaly detection unit identifies the risk of microscopic damage through real-time data (such as the proportion of microstructure phase change grains and local strain concentration), which is a soft protection. The two construct a dual protection mechanism from the two dimensions of macroscopic parameter exceeding the limit and microstructural degradation.

[0080] Therefore, the control center 200 of the embodiment of the present invention is configured to: read the performance description of the SMA wire 700 to be tested (from the manual provided with the manufacturer or other sources); automatically limit the test threshold range based on the performance description of the SMA wire 700, and dynamically adjust the wire damage determination threshold based on the wire specifications; obtain a description of the use of the SMA wire 700; perform a heating or cooling operation according to a preset temperature curve according to a preset testing procedure; control the load applying mechanism 600 to apply a static and / or dynamic target load; receive strain data from a displacement sensor, force data from a force sensor, temperature data from a temperature sensor, and phase transformation grain ratio data from a microstructure monitoring unit; compare the strain data, force data, and other data with an adaptive database to determine whether the SMA wire 700 is qualified; and output an electronic test evaluation report including a strain-temperature curve, a force-time curve, and a determination result. If the performance of the wire material may be damaged during the test, the interlock protection unit will be immediately triggered to execute the load-temperature coordinated protection mechanism, including synchronously reducing the output power of the load application mechanism 600 and the heating power of the environmental simulation chamber 100, and starting a multi-stage cooling compensation program when necessary.

[0081] The wire clamps can be fastened with commercially available metal wire clips and bolts, and can accommodate SMA wires with diameters ranging from 0.02 to 2.0 mm. To facilitate simultaneous testing of multiple SMA wires, at least two parallel sets of wire clamps 500 and corresponding load application mechanisms 600 can be provided on the load-bearing structure.

[0082] The load application mechanism 600 is connected to the free end of the SMA wire 700 and is used to apply a preset static and / or dynamic target load to the SMA wire 700 via weights, an electromagnetic driver, or a pneumatic actuator. The load application mechanism 600 applies a preset static target load to test the basic performance characteristics of the SMA wire 700. For example, static target loads can be applied via a weight set (including multiple weights of different specifications and weights), allowing precise load transfer by adding or subtracting weights. Applying dynamic target loads can simulate real-world application scenarios and assess adaptability to real-world working conditions. In an embodiment of the present invention, the load application mechanism 600 applies a preset dynamic target load via a dynamic loading module. The dynamic loading module includes an electromagnetic driver (model EMD-2050) and its associated power amplifier. The dynamic loading module can be applied in at least three ways: a step loading mode, a sinusoidal wave loading mode, and a random vibration loading mode. Among them, the stepped loading mode is used to simulate the performance response of the SMA wire 700 under intermittent loads, such as detecting the yield point, tensile strength and other static parameters of the SMA wire 700, and simulating the intermittent working state through multi-stage constant loads. It is a special implementation mode for applying static target loads. The static target load is applied in stages, and the loading rate of each load level can be set independently, such as 0.1-500MPa, with a duration error of ≤±1%. The sine wave loading mode generates a sine wave signal with a frequency range of 5-200Hz and an amplitude of 50-1000MPa, and supports phase offset adjustment of 0-180°. Random vibration loading mode, which is based on a power spectrum density of 200G 2 / Hz random vibration signal generation, frequency resolution ≤1Hz, PSD amplitude adjustable range is 0.1-500Pa 2 / Hz. Static target loads are used to characterize basic performance, while dynamic target loads are used to verify adaptability to real working conditions. This effectively evaluates the nonlinear mechanical behavior of SMA wire 700 under real working conditions, such as yield strength and fatigue life.

[0083] The displacement sensor is used to monitor the displacement changes of the SMA wire 700 in real time and calculate the strain, generating a strain-temperature correlation curve. The present invention utilizes displacement sensors and other sensors solely to obtain wire strain data. Therefore, conventional displacement sensors, such as non-contact laser confocal sensors and laser interferometers, can be used to detect wire strain. These are well-known techniques to those skilled in the art, and the types, models, and arrangements of displacement sensors, as well as their ability to obtain wire displacement data, are not further elaborated herein.

[0084] The force sensor, located between the wire fixture 500 and the tip of the SMA wire 700, collects real-time force data from the SMA wire 700, monitoring changes in force during loading and unloading cycles. This generates a force-time curve and, combined with the strain measured by the displacement sensor, calculates the strain recovery rate. For example, if the strain recovery rate is ≥98%, the SMA wire can be assessed as suitable for high-precision applications such as medical stents.

[0085] In an embodiment of the present invention, an environmental simulation chamber 100 is equipped with a temperature control unit, integrated heating elements, cooling elements, and temperature sensors. A closed detection area is formed within the environmental simulation chamber 100. The heating elements, cooling elements, and temperature sensors are electrically connected to the temperature control unit, which is further electrically connected to a control center. The temperature control unit has a temperature control range of -50°C to 300°C, a heating and cooling rate of 1-10°C / s, and generates a temperature-time curve. As a preferred embodiment of the invention, an airflow guide device is also provided within the environmental simulation chamber 100 to achieve a temperature uniformity error of ≤±1°C within the detection area through forced convection. The airflow guide device can be a conventional combination of an axial fan and sidewall deflectors. The axial fan is positioned at the top of the environmental simulation chamber 100 and cooperates with the sidewall deflectors within the environmental simulation chamber 100 to implement a forced convection system. The present embodiment merely applies to this system and does not improve upon it. For details, reference can be made to the forced convection system structure of existing Binder or Memmert constant temperature chambers, and will not be further described here.

[0086] like Figure 1As shown, a thermostatic bath is provided on the side of the environmental simulation chamber 100 close to the SMA wire 700, with the opening of the thermostatic bath facing one side of the SMA wire 700 so as to be able to cover the wire. Heating elements such as thermocouples are evenly embedded in the parallel and opposite groove walls of the thermostatic bath, and the thermocouples are partially embedded in the groove walls and partially extend into the detection area. They are distributed in a rectangular shape within the detection area, and the distribution effect is similar to the cross-section of the thermostatic bath along the vertical direction, so as to form a constant temperature area in the thermostatic bath. Similarly, cooling elements and temperature sensors are also evenly embedded in the interior of the thermostatic bath, wherein the cooling elements can be commercially available semiconductor refrigeration sheets. The cooling elements are used to start cooling the wire when the system temperature exceeds a preset temperature threshold. For this purpose, other rapid cooling methods can also be used to cool the overheated wire, such as injecting low-temperature inert gas into the environmental simulation chamber 100 to quickly cool the detection area and the SMA wire 700 with the low-temperature inert gas. The temperature sensor monitors the temperature of the test area and provides feedback to the temperature control unit, which adjusts the power of the heating element to maintain a test temperature within the test area between -50°C and 300°C. The temperature sensor records the martensitic transformation temperature and austenitic reverse transformation temperature of the SMA wire 700 in real time to assess compliance with the ASTM F2082 standard, e.g., a phase transition temperature deviation of ≤3°C. To ensure uniform temperature across the test area, the dimensions of the thermostatic bath are specified: specifically, the vertical width ranges from 1 to 30 mm, the horizontal depth ranges from 20 to 300 mm, and the length along the wire extension ranges from 10 to 500 mm.

[0087] To facilitate testing and evaluation of the SMA wire 700, the wire fixture 500 or the environmental simulation chamber 100 can be configured to be movable. In this embodiment of the present invention, the environmental simulation chamber 100 is configured to be movable, while the wire fixture 500 is fixed. Furthermore, if the environmental simulation chamber 100 is simple and lightweight, it can be transported directly. If the wire fixture 500 is not fixed, the SMA wire can also be moved while the environmental simulation chamber 100 remains stationary.

[0088] In order to improve the detection efficiency, the supporting structure is provided with two sets of parallel distributed wire clamps, which can simultaneously detect multiple wires. Each set of clamps is independently connected to the partition control module of the control center 200.

[0089] The present invention also discloses an evaluation method performed by an SMA wire material evaluation system simulating a real application scenario, comprising the following steps:

[0090] (1) Parameter Preset: Analyze the factory performance specifications of the SMA wire to be tested, and set the maximum allowable load, critical temperature rise rate, and strain threshold through the dynamic constraint calculation unit. For example, by scanning the QR code label of the SMA wire, the factory performance parameters are obtained and the application code (such as precision valve drive) is analyzed; the corresponding safety factor is retrieved from the adaptive database, and the dynamic constraint calculation unit calculates the test threshold, such as the maximum allowable load, critical temperature rise rate, and strain threshold; the strain threshold is dynamically adjusted according to the wire diameter.

[0091] (2) Clamping preload: Fix the SMA wire 700 to be tested on the wire clamp 500, apply preload force to eliminate the clamping gap, and establish a stable initial state for the test. For example, select a matching pneumatic clamp according to the wire diameter (0.02-2.0mm), and the clamping surface roughness Ra≤0.8μm to avoid scratching the wire surface. Start the pneumatic clamp and apply preload force in two stages: in the first stage, quickly pressurize to 0.3N to eliminate the assembly gap; in the second stage, slowly increase the pressure to 0.5-1N, and ensure that the clamping force error is ≤±0.05N through real-time feedback from the force sensor. Maintain the preload force for 30s. If the displacement sensor detects that the wire slippage is greater than 5μm, re-clamp. Through the graded loading strategy, the local stress caused by clamping is eliminated while protecting the wire surface.

[0092] (3) Environmental simulation: The temperature of the control environment simulation cabin 100 is adjusted according to a preset temperature curve, and static and / or dynamic loads are applied through the load application mechanism 600 to synchronously reproduce the real working environment of temperature-load coupling.

[0093] Initial stabilization stage: the environment simulation chamber 100 is controlled to cool down at a rate of 2°C / s to 20°C below the martensitic phase transformation starting temperature, maintained for 60-120s, and the forced convection system is started to eliminate the thermal history effect of the material.

[0094] Phase transformation linear scanning stage: heating at a rate of 1-5°C / s to 10°C above the end temperature of austenite reverse transformation, covering the entire phase transformation range.

[0095] Cyclic testing stage: perform three complete heating and cooling cycles (martensite phase transformation start temperature -20℃→austenite reverse phase transformation end temperature +10℃→martensite phase transformation start temperature -20℃), and record the hysteresis characteristic data.

[0096] The temperature rise rate is uniformly controlled by the distributed heating array of the environmental simulation cabin 100, and the dynamic load is accurately generated by electromagnetic drives, etc. The load application includes the following methods:

[0097] The static bias load is applied by a weight set at 50% of the rated load (e.g., 250 MPa for a 500 MPa wire). The dynamic disturbance component is superimposed with one of the following modes: sinusoidal loading with a frequency of 5-200 Hz and an amplitude of 5%-20% of the main load; random vibration loading with a power spectral density (PSD) range of 0.1-500 G² / Hz.

[0098] (4) Data acquisition: The closed-loop control unit receives strain, load, and temperature data from the data acquisition module in real time, dynamically adjusts the output power of the load application mechanism and the heating power of the environmental simulation chamber, and stabilizes the detection parameters within the threshold range set by the dynamic constraint calculation unit. The sampling frequency is ≥1kHz, thereby synchronously acquiring the full-dimensional response data of temperature-strain-load. A displacement sensor, such as a laser interferometer (resolution 0.1μm), monitors the strain of the 10mm gauge length in the middle section of the wire. The force sensor uses a strain gauge sensor (accuracy ±0.1%) with a sampling frequency ≥1kHz. The temperature sensor uses a K-type thermocouple (accuracy ±0.5℃). Three measurement points are arranged along the axial direction of the wire, and the average value of the three points is taken.

[0099] During the specific implementation, a hardware trigger signal is used to ensure that the three-axis data timestamps are aligned and the timing error is ≤1μs; it is transmitted to the control center in real time, and noise interference is eliminated through Kalman filtering to provide a high-precision data source for subsequent performance evaluation procedures.

[0100] (5) Collaborative protection triggering: When the interlock protection unit detects any of the following conditions, it will immediately terminate the detection and execute the protection action: the real-time load exceeds 95% of the maximum allowable load; the temperature rise rate exceeds 80% of the critical temperature rise rate; the strain deviation exceeds ±0.5% of the set threshold; the proportion of microstructure phase transformation grains is greater than 2% (real-time monitoring by fiber optic spectrometer); the area of ​​the phase transformation hysteresis loop exceeds ±15% of the reference value; the local strain concentration is greater than 150% (detected by laser speckle interferometer). The load-temperature collaborative protection mechanism is triggered to restore the material. The interlock protection unit generates a load reduction curve and executes a gradient unloading program. The gradient unloading is divided into three stages: the first stage is unloading at 0.5N / s to 50% of the rated load and maintained for 30s; the second stage is unloading at 0.2N / s to 10%; the third stage is free release, and the temperature maintenance program is executed at the same time. The temperature is adjusted to 5-10℃ above the end temperature of the austenite reverse phase transformation for at least 120s. If the temperature fluctuation in the environmental simulation chamber is greater than 5℃, the multi-stage cooling compensation mechanism is activated to eliminate residual stress. This interlocking protection measure enables immediate action to terminate the test and restore the wire material in the event of an unexpected situation during the test, ensuring that the performance of the SMA wire material is not damaged during the test.

[0101] (5) Performance evaluation: Compare the final strain recovery rate with the benchmark value in the adaptive database. When the strain recovery rate is ≥99%, the wire is considered qualified. Alternatively, compare the strain deviation, load fluctuation, and phase transition temperature parameters according to the adaptive database. When the following conditions are met simultaneously: strain deviation (ratio of real-time force standard deviation to mean) ≤±0.5%, load fluctuation ≤±2%, and phase transition temperature deviation (deviation between martensite phase transition start temperature / austenite reverse phase transition end temperature and nominal value) ≤3°C, the wire is considered qualified.

[0102] (6) Secondary verification: After completing the coordinated protection, reload to 50% of the rated load at a rate of 0.1 N / s, continue for 30 s, and then unload. If the strain recovery rate is ≥99.5%, the wire is judged to be undamaged.

[0103] Test and Evaluation Report Generation: Outputs standardized evaluation conclusions and traceability data. The three data items and the judgment results are integrated into a time series graph. The report includes test parameters (temperature curve, loading mode, wire material specifications), raw data segments (including phase transformation hysteresis loops and strain-load curves), judgment conclusions (pass / fail), detailed descriptions of exceeded / failed items, digital signatures, and test log hash values, resulting in an electronic report compliant with ISO / ASTM standards.

[0104] The technical solution of the present invention is illustrated below with reference to specific embodiments:

[0105] Example 1

[0106] Normal detection mode (parameters are far from the safety threshold)

[0107] Test conditions:

[0108] Tested wire: Nickel-titanium based SMA wire, diameter 0.2 mm, nominal phase transition temperature (martensite phase transition temperature As = 65 ° C, austenite reverse phase transition temperature Af = 80 ° C), maximum allowable stress 800 MPa.

[0109] Application: Medical catheter drive wire, safety factor set to 1.8 (medical use mapping value).

[0110] Operation process:

[0111] 1. Parameter setting: The dynamic constraint calculation unit automatically sets the detection threshold according to the safety factor (1.8), maximum allowable load = 800MPa / 1.8≈444MPa; critical temperature rise rate = 3℃ / s (60% of the nominal value); strain threshold = nominal strain recovery rate (99%) × 0.8 = 79.2%.

[0112] 2. Environmental simulation: Temperature curve, initial stage 40℃ (As-20℃) maintained for 90s, heating at 2℃ / s to 90℃ (austenite reverse phase transformation temperature Af+10℃), cycle 3 times.

[0113] 3. Protection mechanism: Real-time monitoring data, temperature rise rate 1.8°C / s, peak load 315MPa, strain recovery rate 82.3%; interlock protection unit was not triggered (all parameters were below 70% of the threshold).

[0114] 4. Data Verification: Strain deviation, ±0.3% (<0.5%); phase transition temperature deviation, As = 64.5°C, Af = 79°C (<3°C). Secondary verification, reloading 400 MPa (50% of rated value), strain recovery rate 99.6%, meeting the qualification standard.

[0115] 5. Report generation: If qualified, generate a test report, including stress-strain curve diagram, such as Figure 4 As shown, each performance meets the factory performance standards and meets the application requirements.

[0116] Example 2

[0117] Extreme working condition simulation test (parameters close to safety thresholds)

[0118] Test conditions:

[0119] Tested wire: Iron-based SMA wire, diameter 1.0 mm, nominal phase transition temperature (As = 120 ° C, Af = 150 ° C), maximum allowable stress 500 MPa.

[0120] Application: Industrial valve drive, safety factor set to 1.3 (industrial use mapping value).

[0121] 1. Parameter setting: The dynamic constraint calculation unit adjusts the threshold to the critical state, the maximum allowable load = 500MPa / 1.3≈385MPa; the critical temperature rise rate = 4.5℃ / s (90% of the nominal value); the strain threshold = nominal strain recovery rate (95%) × 0.9 = 85.5%.

[0122] 2. Environmental simulation: Temperature curve: Initial stage: 100°C (As-20°C) maintained for 60 seconds, then heated to 160°C (Af+10°C) at a rate of 4°C / s; Load application: multi-level step loading (300MPa→350MPa→380MPa, in accordance with the exponential decay law), each level maintained for 30 seconds.

[0123] 3. Collaborative protection trigger:

[0124] Real-time monitoring data: During the third-stage loading phase, the load was 382 MPa (99.2% overload) and the temperature rise rate was 4.3°C / s. The interlock protection unit responded, generating an exponential load reduction curve, reducing the load to 320 MPa within 10 seconds. Secondary cooling compensation was initiated, and the temperature decreased from 160°C to 145°C (Af -10°C) at a rate of 6°C / s, maintaining this temperature for 120 seconds.

[0125] 4. Damage blocking:

[0126] like Figure 2 As shown in the figure, microstructure monitoring shows an austenite phase ratio of 98.2% (±1% fluctuation allowed), with no abnormal grain growth. Gradient unloading was performed at a rate of 0.8 N / s to 50 MPa, while maintaining the temperature at 145°C to relieve residual stress.

[0127] 5. Report generation: If the critical condition is determined to be qualified (load fluctuation ﹢1.9%, close to the threshold but controllable), it will be recorded as "applicable to marginal conditions". Its stress-strain curve is as follows: Figure 5 shown.

[0128] Example 3

[0129] Recovery from unexpected interruption (emergency treatment of heating failure)

[0130] Test conditions:

[0131] Tested wire: copper-based SMA wire, diameter 0.5 mm, nominal phase transition temperature (As = 120 ° C, Af = 150 ° C).

[0132] Abnormal event: The heating element of the environmental simulation cabin malfunctioned, and the temperature rose to 110°C (Af+15°C) and then stagnated.

[0133] Operation process

[0134] 1. Abnormal Detection: If the temperature sensor detects a temperature fluctuation greater than 5°C (target value 95°C → actual value 72°C → 11°C) within 120 seconds, the abnormal detection unit will determine it as "heating runaway" and trigger a three-level alarm (audio and visual prompts + log recording).

[0135] 2. Emergency response: The interlock protection unit executes: forced start of the semiconductor refrigeration plate, cooling the temperature to 85°C (Af-10°C) at 8°C / s; the load application mechanism switches to the free state, releasing the external mechanical constraints; and generates an event report (including temperature mutation curve, timestamp, and operation log hash value).

[0136] 3. Wire recovery: Perform gradient unloading, unloading from the current load of 510MPa to 0MPa at 0.5N / s, while maintaining the temperature at 85℃, and reloading to 250MPa (about 50% of the rated value), with a strain recovery rate of 99.3% (baseline value 99.5%).

[0137] 4. Data analysis: The surface morphology of the wire was obtained by metallographic microscope. Grayscale analysis showed that the martensite phase was 62% (normal range 60%-65%) and there was no irreversible phase change. Figure 3 The stress relaxation model is updated, the online learning module marks the abnormal data, and the temperature control parameter weights are corrected.

[0138] 5. Report generation: Determine that "the accidental interruption did not cause damage" and generate repair suggestions (replace the heating element, calibrate the temperature control unit), and its stress-strain curve diagram, such as Figure 6 shown.

[0139] While the present invention has been disclosed above with reference to preferred embodiments, this is not intended to limit the present invention. Persons skilled in the art will readily appreciate that various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. An SMA wire evaluation system simulating a real application scenario, comprising a load-bearing structure, provided with a wire clamp (500) and a load applying mechanism (600), wherein the wire clamp (500) is configured to clamp one end of an SMA wire (700) to be tested, and the load applying mechanism (600) is configured at the free end of the SMA wire (700) and applies a test load; and an environmental simulation cabin (100) covering a test area of ​​the SMA wire (700) and provided with a temperature control unit, characterized in that: Also includes: A data acquisition module, comprising a displacement sensor, a force sensor (800) and a temperature sensor, for respectively monitoring the strain, load response and temperature data of the SMA wire (700); Control Center (200), integrating: An adaptive database storing stress relaxation characteristic data of SMA wires (700) of different specifications and a safety factor mapping table associated with the usage; a dynamic constraint calculation unit that automatically sets a maximum allowable load, a critical temperature rise rate, and a strain threshold based on the factory performance description of the SMA wire (700); A closed-loop control unit, which calls the stress relaxation characteristic data stored in the adaptive database to dynamically adjust the load and temperature parameters; An interlock protection unit is configured to trigger a load-temperature coordinated protection mechanism when the real-time monitored load, temperature rise rate, or strain data exceeds a threshold value set by the dynamic constraint calculation unit; The system ensures that the residual plastic strain of the SMA wire (700) is ≤0.1% and the microstructure has no phase change-induced defects during the detection process through the coordinated action of a closed-loop control unit and an interlocking protection unit; The interlock protection unit performs the following operations: Generate a load reduction curve and execute the unloading procedure. The load reduction rate is negatively correlated with the real-time temperature rise rate. The temperature of the environmental simulation cabin (100) is forcibly maintained in a stable range of 5-10°C above the end temperature of the austenite reverse phase transformation of the SMA wire, for a duration of ≥120s; When the temperature fluctuation in the environmental simulation cabin (100) is greater than 5°C, a multi-stage cooling compensation program is started.

2. The SMA wire material evaluation system simulating real application scenarios according to claim 1 is characterized in that: The adaptive database includes: Gradient safety factor table based on SMA wire diameter; Phase transformation temperature-load correlation matrix based on SMA wire alloy composition; The online learning module extracts features from the stress relaxation curve in each batch of test data and updates the stress relaxation model parameters every 24 hours.

3. The SMA wire material evaluation system simulating real application scenarios according to claim 1, characterized in that: The bearing structure is provided with at least two groups of parallel distributed wire clamps (500) and corresponding load applying mechanisms (600).

4. The SMA wire material evaluation system simulating real application scenarios according to claim 1, characterized in that: The load applying mechanism (600) comprises: Static loading module, which applies a constant load through a weight set; Dynamic loading module supports sinusoidal wave loading, random vibration loading and multi-level step loading modes.

5. The SMA wire material evaluation system simulating real application scenarios according to claim 1, characterized in that: The data acquisition module further comprises a microstructure monitoring unit configured to acquire phase change grain ratio data of a detection area of ​​the SMA wire (700) in real time; The control center (200) further comprises an abnormality detection unit, which is connected to the data acquisition module and the interlock protection unit via bus communication and is configured as follows: receiving stress and phase change grain ratio data from the data acquisition module in real time; When any of the following situations is identified, an abnormal interrupt instruction is generated and sent to the interlock protection unit: The proportion of microscopic phase transformation grains is greater than 2%; The phase change hysteresis area exceeds ±15% of the benchmark value in the adaptive database; Local strain concentration>150%; The interlock protection unit triggers a load-temperature coordinated protection mechanism in response to the abnormal interruption instruction.

6. A method for evaluating SMA wires that simulates real application scenarios, using the system according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) Parameter presetting: analyzing the factory performance description of the SMA wire (700) to be tested, and setting the maximum allowable load, critical temperature rise rate and strain threshold through the dynamic constraint calculation unit; (2) Clamping preload: Fix the SMA wire (700) to be tested to the wire clamp (500), and apply a preload force to eliminate the clamping gap; (3) Closed-loop regulation detection: a. controlling the temperature of the environment simulation chamber (100) according to a preset temperature curve, and applying a static or dynamic load through the load applying mechanism (600); b. The closed-loop control unit receives strain, load, and temperature data from the data acquisition module in real time and dynamically adjusts the output power of the load application mechanism and the heating power of the environmental simulation chamber to stabilize the detection parameters within the threshold range set by the dynamic constraint calculation unit; (4) Collaborative protection triggering: When the interlock protection unit detects any of the following conditions, it will immediately terminate the detection and execute the protection action: the real-time load exceeds 95% of the maximum allowable load; the temperature rise rate exceeds 80% of the critical temperature rise rate; the strain deviation exceeds ±0.5% of the set threshold; (5) Performance evaluation and verification: Compare the final strain recovery rate with the benchmark value in the adaptive database. When the strain recovery rate is ≥99%, the wire is judged to be qualified.

7. The SMA wire material evaluation method simulating a real application scenario according to claim 6, characterized in that: The preset temperature curve in step (3) includes: Initial stabilization stage: maintain at 20°C below the phase transition starting temperature for 60-120s; Phase transition linear scanning stage: heating at a rate of 1-5°C / s to 10°C above the end of phase transition; Cycle detection phase: Perform at least three complete phase change cycles.

8. The SMA wire material evaluation method simulating a real application scenario according to claim 6, characterized in that: The conditions for immediately terminating the test in step (4) also include: the proportion of microscopic phase transformation grains is greater than 2%; the area of ​​the phase transformation hysteresis loop exceeds ±15% of the reference value; the local strain concentration is greater than 150%; The execution protection action includes: a gradient unloading program, a temperature maintenance program and a multi-stage cooling compensation program.

9. The SMA wire material evaluation method simulating a real application scenario according to claim 6, characterized in that: After step (4), execute: Secondary verification: Reapply 50% of the rated load and verify that the strain recovery rate is ≥99.5%.

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