Abstract:
Shape memory alloys are a class of smart materials, which have the unique ability to regain their original shape after deformation, when they are subjected to an external stimulus. They are used in various applications, such as actuators, couplings, dampers, orthodontic archwires, eyeglass frames, etc. When shape memory alloys (SMAs) are subjected to cycling, either thermally or mechanically or thermomechanically, their functional properties, such as transformation temperatures, recovery strain, recovery stress, hysteresis width, etc., are affected. The degradation of functional properties of SMAs due to prolonged use, under thermal or mechanical, or thermomechanical cyclic conditions is called functional fatigue. In this seminar, the effects of operating parameters, such as upper cycle temperature (UCT) and the applied stress level, on the functional properties of NiTi SMAs, the newly observed transformation strain arrest phenomenon during partial thermomechanical cycling of NiTi SMAs, and the effect of thermomechanical treatment on the functional fatigue behaviour of an NiTiCu SMA will be presented in detail.