Bending Model of an Integrated SMA Micro-Actuator

Abstract

In this paper, we give a model of a Shape Memory Alloy (SMA) thin blade working in bending. This work is based on the general study and modeling of an integrated SMA micro-actuator called the “ module”, controled by thermoelectric effect. This module was developed in two versions. The first one is composed of a NiTi thin blade on which are placed two copper elements which play the role of heat sinks. Its temperature is controlled by Joule effect. In the second version, Bismuth Telluride ingots are used instead of copper elements. This second configuration allows the temperature control of the SMA blade by Peltier effect. The model of the bending behavior is based on a general macroscopic description of the thermomechanical behavior of SMA. The self-accommodating (pure thermal effect) and oriented (stress-induced) martensites are taken into account. The thermal boundary conditions used in this paper correspond to the first version of the micro-actuator. The numerical resolution by finite differences leads to the comprehension of phase transformation for pseudo-elastic and thermal cycling bending tests.