Patents on Superelastic Shape Memory Alloy

Abstract

Innovative investigations, discoveries and recent patents regarding superelastic shape memory alloy (SMA), a novel material, are briefly discussed in this review paper. Known as a functional material, SMA can recover large strains in two ways: shape memory effect (SME) and pseudoelasticity. SME is by virtue of temperature induced martensitic transformation while pseudoelasticity (also called superelasticity) happens because of stress induced martensitic transformation (SIMT). SMA is one of the most widely used functional materials in many adaptive structures, as well as in medical and biomedical applications. Because of SME, SMA can be mainly used for active control of adaptive structures. On the other hand, having pseudoelasticity SMA can be used for passive damping of a vibrating structure. Superelastic SMA is also widely used for applications like: antenna of portable phones, headband of headphones, in the ballpoint pens and eyeglass frames etc. This study will focus mainly on pseudoelasticity of SMA and its potential characteristics. Keywords: Shape memory alloy, stress induced martensitic transformation, pseudoelasticity (superelasticity), nonlinear stress-strain curves, tension-compression asymmetry