Finite element analysis for fatigue phenomena in mechatronic shape memory alloy actuator

Abstract

Shape memory alloy (SMA) characterized by several important thermo-mechanical functions. There are becoming a vital actuator in mechatronic systems that can react to electrical current and produce a mechanical action. However, the use of shape memory alloys encounters several challenges in order to integrate these materials in dynamic systems. The need for meticulous precision and short response time is required for the use of SMA actuators in mechatronic applications. On the other hand, the residual deformation cannot be avoided due to the nature of the use of these materials, the phenomenon of fatigue is very frequent that affects the performance and minimizes the life of shape memory alloy actuator. The study proposes a mechatronic system based on two springs of Ni-Ti SMA that controlled by an electric current for ensuring rapid and accurate displacement taking into account fatigue phenomena. Hence, an analysis of fatigue phenomena using a finite element technique has been proposed in order to optimize the usage of shape memory alloy in Mechatronic systems. The proposed model captures both thermo-mechanical behavior that superelasticity and shape memory effect in response to electrical current for SMA actuator. Consequently, the numerical results, analyze the concentration of stress using a finite element method and describe the heat transfer in the system to optimize the response time by improving the heating and cooling times. Model verification was performed using comparison of numerical results with experimental results. The main finding of the current work is the safeguarding of the Ni-Ti superelastic reaction in the proposed system as verified by the variation cycling up to 8% strain, much greater than naturally needed for mechatronic applications. Thus, the response time and the temperature stabilization time of SMA material in response to electric current has been optimized in order to meet the needs of the mechatronic applications.