ABSTRACT
Shape memory alloys (SMAs) are metallic compounds. Th ey exhibit a cubic high-temperature crystal structure, which transforms by martensitic reaction into another crystal structure (tetragonal, orthorhombic, hexagonal, etc.) when temperature decreases. Martensitic transformation enables large shape changes and the
References .......................................................................................................................................... 20-6 20.2 SMAs in Micro-and Nanoscale Engineering Applications ............................................ 20-8
References .........................................................................................................................................20-16 20.3 Mathematical Models for Shape Memory Materials .......................................................20-17
References .........................................................................................................................................20-27 20.4 Shape Memory Alloys ........................................................................................................ 20-28
SMAs and the Martensitic Transformation • SMAs Systems • Functional Properties of SMAs
References .........................................................................................................................................20-35 Bibliography .................................................................................................................................... 20-36 20.5 Smart Materials Modeling ................................................................................................. 20-36
References ........................................................................................................................................ 20-41 20.6 On the Microstructural Mechanisms of SMEs ............................................................... 20-41
Microscopic Mechanisms • Macroscopic Eff ects • Summary Acknowledgments .......................................................................................................................... 20-46 References ........................................................................................................................................ 20-46
shape memory eff ect (SME), but heating and cooling are needed to complete the phase transformation. SME can produce large relative strains and high stress output, but usually small actuation frequency due to the slow cooling process [1-4]. Th e SMAs have typically twinned martensitic structure with mobile twin boundaries. Th e multivariant twin structure can easily be deformed to the single-variant state to yield the maximum SME shape change.
