A macroscopic description of shape memory alloy functional fatigue

Shape memory alloys (SMAs) are smart materials employed in several applications including medical devices, aerospace components, robotics, among others. In many of these applications, devices are subjected to cyclic loading conditions. Based on this, a proper comprehension of fatigue phenomenon is essential for suitable design of systems involving SMA elements. In general, SMAs exhibit two kinds of fatigue: functional fatigue, related to the decrease of the functional properties; and structural fatigue, associated with the nucleation and growth of microcracks that lead to fracture. This paper presents a macroscopic three-dimensional constitutive model to describe functional fatigue on shape memory alloys considering continuum damage perspective. Numerical simulations are compared with experimental results showing the capabilities of the proposed model. In addition, numerical simulations are presented in order to explore the general thermomechanical aspects of SMA functional fatigue, allowing a proper comprehension of phenomenological aspects.