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CN-121978162-A - Shape memory strain test method for shape memory alloy material

CN121978162ACN 121978162 ACN121978162 ACN 121978162ACN-121978162-A

Abstract

The invention provides a shape memory strain testing method of a shape memory alloy material, which comprises the steps of firstly obtaining the phase transformation end temperature of the material through a differential scanning calorimetry method, then respectively preserving heat for a certain time at two constant temperature points which are 5-30 ℃ higher than the austenite phase transformation end temperature and 5-30 ℃ lower than the martensite phase transformation end temperature, measuring the size of the material, and finally calculating the shape memory strain based on the size difference of two phases. The method is not limited by the form of the material, is suitable for wires, pipes, plates and special-shaped components, can flexibly select whether to apply load or not, truly reflects the strain capacity of the material under the actual working condition, and provides a high-efficiency and reliable test means for the performance evaluation and device design of the shape memory alloy.

Inventors

  • SUN YALING
  • WANG MEIMEI

Assignees

  • 上海钛忆科技有限公司

Dates

Publication Date
20260505
Application Date
20260130

Claims (10)

  1. 1. A shape memory strain testing method of a shape memory alloy material, which is characterized in that the shape memory alloy material is provided with a first phase in a high temperature state and a second phase in a low temperature state; the test method comprises the following steps: (1) Acquiring a first phase transition end temperature and a second phase transition end temperature of the shape memory alloy material; (2) Preserving heat for a first preset time at a first preset temperature higher than a first phase transition ending temperature to enable the shape memory alloy material to be completely converted into the first phase, and measuring a first size of the shape memory alloy material when the shape memory alloy material is in the first phase; (3) Preserving heat for a second preset time at a second preset temperature lower than a second transformation ending temperature to enable the shape memory alloy material to be completely transformed into the second phase, and measuring a second dimension of the shape memory alloy material at the same position as that in the step (2) when the shape memory alloy material is in the second phase; (4) Based on the first dimension and the second dimension, a shape memory strain of the shape memory alloy material is calculated.
  2. 2. The method according to claim 1, wherein the first preset temperature is set to be 5-30 ℃ higher than the first transformation ending temperature.
  3. 3. The method according to claim 1, wherein the second preset temperature is set to be 5-30 ℃ lower than the second transformation ending temperature.
  4. 4. The method of claim 1, wherein in the step (1), the step of obtaining the first phase transition end temperature and the second phase transition end temperature includes: (1.1) testing the shape memory alloy material using differential scanning calorimetry, the testing process comprising at least one complete thermal cycle, obtaining a DSC profile; (1.2) calibrating the first phase transition end temperature and the second phase transition end temperature based on the obtained DSC profile.
  5. 5. The method of claim 4, wherein the method of calibrating the first phase transition end temperature and the second phase transition end temperature comprises at least one of a tangent method and an extrapolation method.
  6. 6. The method for testing the shape memory strain of the shape memory alloy material according to claim 4, wherein when the differential scanning calorimetry is adopted, the temperature rise rate and the temperature fall rate are both 5-10K/min or less and V T -10min or less.
  7. 7. The method of claim 4, wherein the testing process comprises at least one complete thermal cycle, comprising: performing 2-3 times of complete thermal cycles, and taking the temperature at which the phase transition of the first phase of the first thermal cycle is finished and the temperature data at which the phase transition of the second phase is finished as the first phase transition finishing temperature and the second phase transition finishing temperature respectively; Or taking the average value of the temperature at which the phase transition of the first phase is ended and the average value of the temperature at which the phase transition of the second phase is ended in a plurality of times of thermal cycles as the first phase transition ending temperature and the second phase transition ending temperature respectively.
  8. 8. The method for testing the shape memory strain of the shape memory alloy material according to claim 1, wherein the first preset time is 10-30 min, and the second preset time is 10-30 min.
  9. 9. The method according to claim 1, wherein a predetermined load or no load is applied to the shape memory alloy material according to an application situation or a requirement during the measurement of the first dimension and/or the second dimension; If no load is applied, the first preset temperature is set to be 5-10 ℃ higher than the first phase change ending temperature, and the second preset temperature is set to be 5-10 ℃ lower than the second phase change ending temperature; and if the load is applied, setting the first preset temperature to be 10-30 ℃ higher than the first phase change ending temperature, and setting the second preset temperature to be 10-30 ℃ lower than the second phase change ending temperature.
  10. 10. The method of claim 1, wherein the shape memory alloy material comprises a wire, a rod, a tube, a plate, or a profiled member.

Description

Shape memory strain test method for shape memory alloy material Technical Field The invention relates to the technical field of shape memory alloy material testing, in particular to a shape memory strain testing method of a shape memory alloy material. Background The shape memory alloy material has unique shape memory effect and superelasticity, and has wide application in the fields of aerospace, biomedical treatment, precise driving and the like. Shape memory strain (or recoverable strain) is a key parameter for measuring shape memory performance of the shape memory alloy device, and directly affects the electrical control parameters, structural design and operational reliability of the shape memory alloy device. At present, a unified and efficient method for testing the shape memory strain of the shape memory alloy is not available. The relevant standards only define the two-way memory recovery strain, but specific testing methods and operation details are not specified, so that the actual testing lacks standard basis. In the prior art, part of research adopts dynamic thermo-mechanical analysis (DMA) to acquire shape memory strain through a temperature-strain curve, but the method generally requires extremely low temperature rise and fall rate (for example, lower than 3K/min), long test time consumption and low efficiency, and is difficult to meet the requirement of rapid evaluation engineering application. In addition, the existing test method has poor adaptability to the shape and the size of the sample, and is difficult to be applied to shape memory alloy materials with different shapes such as wires, pipes, special-shaped members and the like. If the temperature control is inaccurate or the phase change state is not determined clearly in the test process, the shape memory strain measurement result is easy to deviate from the true value, and further the performance evaluation of the material and the rationality of the device design are affected. If the shape memory strain value according to the design of the device is inaccurate, serious problems are caused, namely if the design value is larger than the strain actually provided by the material, excessive driving current is often required to be applied to achieve the aim, so that the material damages a microstructure due to instantaneous overheating and accelerates fatigue performance attenuation, and if the design value is far smaller than the actual potential of the material, the utility of the material cannot be fully exerted, and the volume redundancy and the space utilization of the device are reduced. Therefore, a method capable of rapidly and accurately measuring the shape memory strain is developed, and the method has important significance for material evaluation and device engineering design. Disclosure of Invention The invention aims to provide a shape memory strain testing method of a shape memory alloy material, which is limited by the measured shape and the measured size, and has the advantages of high adaptability, high operability, high executable performance and high efficiency. In order to achieve the above purpose, the present invention proposes the following technical scheme: A shape memory strain testing method of shape memory alloy material, the shape memory alloy material has a first phase in a high temperature state and a second phase in a low temperature state; the test method comprises the following steps: (1) Acquiring a first phase transition end temperature and a second phase transition end temperature of the shape memory alloy material; (2) Preserving heat for a first preset time at a first preset temperature higher than a first phase transition ending temperature to enable the shape memory alloy material to be completely converted into the first phase, and measuring a first size of the shape memory alloy material when the shape memory alloy material is in the first phase; (3) Preserving heat for a second preset time at a second preset temperature lower than a second transformation ending temperature to enable the shape memory alloy material to be completely transformed into the second phase, and measuring a second dimension of the shape memory alloy material at the same position as that in the step (2) when the shape memory alloy material is in the second phase; (4) Based on the first dimension and the second dimension, a shape memory strain of the shape memory alloy material is calculated. As a preferable technical scheme of the invention, the first preset temperature is set to be 5-30 ℃ higher than the first phase transition ending temperature. As a preferable technical scheme of the invention, the second preset temperature is set to be 5-30 ℃ lower than the second phase change ending temperature. As a preferred embodiment of the present invention, in the step (1), obtaining the first phase transition end temperature and the second phase transition end temperature includes: (1.1) testing the shape memory alloy material