Thermomechanical performance analysis and experiment of electrothermal shape memory alloy helical spring actuator

Yang Xiong,Ruizhi Shu,Jin Huang

doi:10.1177/16878140211044651

Yang Xiong, Ruizhi Shu + Show 1 more

Open Access

https://doi.org/10.1177/16878140211044651

Copy DOI

Abstract

In this paper, an electrothermal shape memory alloy helical spring actuator constructed from shape memory alloy with copper-cored enameled wire is presented and fabricated. Based on the shear constitutive model of a shape memory alloy, the Thermo equilibrium equation and the geometrical equation of helical spring establish the thermomechanical theoretical model of helical spring actuator with electrothermal shape memory alloys under different scenarios. The thermomechanical behaviors of the actuator were verified by numerical simulation with experimental tests, and the actuator thermomechanical properties were derived from the analysis with current, temperature, response time, restoring force, and axial displacement as parameters. The experimental results show that the actuator produces a maximum recovery force of 70.2 N and a maximum output displacement of 7.7 mm at 100°C. The actuator response time is 26 s at a current of 3A. It is also demonstrated that the theoretical model can effectively characterize the complex thermo-mechanical properties of the actuator due to the strong nonlinearity of the shape memory alloy. The experimental temperature-force response and temperature-displacement response, as well as the force-displacement response at different temperatures, provide references for the design and fabrication of electrothermal shape-memory alloy coil spring actuators.

Highlights

Shape memory alloys (SMA) are a class of smart alloy materials with shape memory effect (SME) and superelasticity
The process by which SMA produces shape memory effect is that loading SMA transforms the austenite phase to stable non-twinned martensite phase when SMA is below the austenite phase transition temperature, heating SMA after unloading brings it to the austenite phase finish transition temperature, SMA reverses from non
The volume fraction and shape memory factor of martensite in SMA increase gradually at this time; After finishing loading, the temperature of the electrothermal SMA helical spring is T = 25°C (T \AS), No phase transformation occurs in the SMA non-twinned martensite during unloading, and after the end of unloading, the recoverable non-linear strain of the SMA transforms to the residual strain; In the heating stage, the current is applied to make the temperature of SMA spring rise to T = 100°C (T .Af )

Summary

Introduction

Shape memory alloys (SMA) are a class of smart alloy materials with shape memory effect (SME) and superelasticity. The volume fraction and shape memory factor of martensite in SMA increase gradually at this time; After finishing loading, the temperature of the electrothermal SMA helical spring is T = 25°C (T \AS), No phase transformation occurs in the SMA non-twinned martensite during unloading, and after the end of unloading, the recoverable non-linear strain of the SMA transforms to the residual strain; In the heating stage, the current is applied to make the temperature of SMA spring rise to T = 100°C (T .Af ).

Af À As

Experimental setup

Conclusions