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.

Transition from many domain to single domain martensite morphology in small-scale shape memory alloys

“…For example, we may re-examine the size effect on transformation hysteresis in light of the above discussion, because hysteresis is directly related to transformation obstacles [21,66,67]. During a thermoelastic martensitic transformation the moving interface has to perform an amount of frictional work related to the number and nature of the obstacles it meets [21,67].…”

“…During a thermoelastic martensitic transformation the moving interface has to perform an amount of frictional work related to the number and nature of the obstacles it meets [21,67]. The energy dissipated as heat when the austenitemartensite interface bypasses these obstacles is reflected in the magnitude of the stress hysteresis [67]. As a first order model, the stress hysteresis magnitude, Δσ, is simply proportional to the obstacle number density, n, per unit volume of sample…”

Surface roughness-controlled superelastic hysteresis in shape memory microwires

“…In line with this, hysteresis size has been shown to decrease with increasing degree of crystal perfection [19]. In small scale SMAs, the sampling of obstacles at the wire surface has been put forward as the dominant source of energy damping [2]; as noted in the introduction, the scaling of hysteresis with wire diameter aligns with this proposal for wires below about 100 µm in size scale.…”

Damping Capacities of Ti₅₀Ni_50&minus;<i>_x</i>Cu<i>_x</i> Shape Memory Alloys Measured under Temperature, Strain, and Frequency Sweeps

“…In addition, the calculated n values in Granato-Luecke breakaway model are around 2.53.0, but those in friction type model are around 0.5. 35) Therefore, from the calculated n values shown in Tables 2 and 3, one can find that the characteristics shown in Figs. 2 and 3 are more close to the friction type model.…”