Thermomechanical behavior and resistance sensing properties of ultrafine NiTi shape memory alloy wires

Abstract

Shape memory alloys (SMAs) are promising smart actuators, offering advantages such as the shape memory effect (SME), large deformation capability, and high power-to-weight ratio. This study investigates the driving and resistance characteristics of 25 μm-diameter NiTi SMA ultrafine wires under varying conditions of voltage, training cycles, and pre-strain. Experimental data were used to establish a resistance thermal driving model through curve fitting. The results reveal that SMA wires achieve rapid actuation with a response time as low as 0.3 s, where higher voltages further reduce response time. Stable performance is attained after 15–20 thermal–mechanical training cycles. Additionally, applying optimal pre-strain enhances recovery force and driving displacement, while minimizing hysteresis in the resistance thermal driving relationship. These findings provide valuable insights and a robust experimental foundation for the development of ultrafine NiTi SMA-based actuation and sensing systems.