Dragos Cristian Achitei

By Petrică Vizureanu and Dragoș-Cristian Achiței

This chapter presents advanced researches about the using of metallic alloys with shape memory properties in construction and exploitation of parts subjected to combined stress by thermal and mechanical fatigue during their functioning. The shape memory alloys (SMAs) have a series of properties much different from the usual metallic materials. Their main characteristic is recovery/returning from plastic deformation by heating, considering that in some cases at temperature changing, the shape modification is reversible. In the case of parts made from SMA, which work in conditions by thermal and mechanical stresses and temperature variations, the resistance evaluation at thermal and mechanical fatigue is absolutely necessary. Like researching domain, regarding thermal and mechanical fatigue behavior, it was selected the shape memory Cu-based alloy. The achieved researches, concerning methodology, investigation equipment, experimental results, allow evaluating and estimating the shape memory properties. Losing the shape memory properties of SMA, in requested conditions, namely amnesia, so to the calculation of fatigue resistance must be taken into account by this fundamental property. The expression of the fatigue state, through losing the memorizing capacity, represents a designing indicator, which ensures the guaranty of properties in fatigue conditions, through applying of fatigue cycles. To determine the fatigue resistance of SMA was necessary specific requests. The properties are guaranteed for a certain number of fatigue cycles. The experimental data, presented in this chapter, offer to scientists some information about the SMAs, Cu-based. These data can be used in designing and manufacturing of new parts for different devices.

Part of the book: Shape-Memory Materials