Active and passive damping of noise and vibrations through shape memory alloys: applications and mechanisms

Abstract

Recent achievements have been analysed in designing and application of shape memory alloys as high-damping elements, utilizing pseudoelastic hysteresis, transient damping effects in the two-phase state and damping capacity of the martensitic phase. Dealing with intrinsic damping capacity of martensitic phases, several new observations are described, like ‘universal’ low-temperature high-damping properties of ternary Cu-based alloys, high non-linear damping capacity of a binary NiTi in R phase and high linear damping of binary hydrogen-charged NiTi. Based on the analysis of results of recent studies of damping in NiTi (B19’ martensite, R phase) and Cu-based families of alloys (Cu–Al–Ni, Cu–Zn–Al, Cu–Al–Be), we try to introduce a guideline relating desired damping properties of a SMA with its structural characteristics. Among the parameters determining the contribution of specific defect species to damping we suggest considering • density of specific type of defects (intervariant boundaries and internal defects of variants like dislocations and twins); • their mobility (determined by crystallography and geometrical factors, like accommodation and size of martensitic variants); • concentration and type of obstacles impeding the motion of defect species and, thus, producing damping (concentration, mobility and distribution of quenched-in/point-like defects, precipitates, etc). The importance of distinguishing linear and non-linear components of damping is emphasized, since, in a general case, they can be related to different elements of defect microstructure of martensite.