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

Jan Van Humbeeck¹ and Sergey Kustov²

¹. Dep. MTM, KULeuven, Kasteelpark Arenberg 44, B-3001 Leuven, Belgium

². Dep. Física, Universitat de les Illes Balears Cra Valldemossa, km 7.5, E-07122 Palma de Mallorca, Spain

Recent achievements have been analysed in designing and application of shape memory alloys as high-damping elements, utilising pseudoelastic hysteresis, transient damping effects in the two-phase state and damping capacity of the martensitic phase. Special attention is paid in the review to composite materials, incorporating shape memory alloys as passive elements and as active parts of  constructions, which properties are subjected to external control.

In the part, dealing with intrinsic damping capacity of martensitic phases, several new observations are described, like “universal” low-temperature high damping properties of ternary Cu-base 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-base 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 to consider

-         density of specific type of defects (intervariant boundaries and internal defects of variants like dislocations, 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 emphasised, since, in a general case, they can be related to different elements of defect microstructure of martensite.