Electro‐thermo‐mechanical characterization of shape memory alloy wires for actuator and sensor applications—Part 1: The effects of training

Abstract

So far shape memory alloys (SMA) are mostly characterized by theirthermo-mechanical behavior due to the underlying thermal effect. In technicalapplications however, where their benefits like low weight and compact designbecome relevant, they are activated electrically. This work presents methods fora thorough and systematic characterization of SMA wire samples under Jouleheating with the focus on aspects relevant for applications. The goal is to achievea precise understanding of the sensor and actuator properties of SMA wire sam-ples with different trainings under varying loads. All experiments are conductedon a custom designed test bench with a commercially available NiTi wire with72 μm diameter, which enables the direct comparisons of tensile tests to actua-tion tests. The characterization consists of tensile tests and actuator tests withvarying load and heating power for differently trained wire samples. The resultsvividly represent the influence of heating power, training and changing loadson stroke output, working point and the functional stability of SMA actuatorwires. Especially, the evolution of the resistance signal and the influence of theR-phase on self-sensing is discussed. The proposed method enables to compareand choose the best suitable alloy with a fitting training for a desired application.