The Mechanisms, Measurement Techniques and Characterization of Shape Memory Alloy

TiNi-based shape memory alloys are being considered for space-related applications due to their damping capacity, as well as shape memory effect (SME) and pseudoelasticity (PE). TiNi SMAs with high damping capacity are used as structural materials for energy dissipation or vibration control applications. The Internal Friction (IF) of TiNi alloys has been investigated by different experimental measurement techniques, to characterize and evaluate the damping capacity, based on related damping models. Damping measurements were conducted on dynamic mechanical thermal analyzer (DMTA), dynamic mechanical analyzer (DMA) and differential scanning calorimetry (DSC) equipment, measuring Tan delta, storage modulus E' and loss modulus E" at different temperature, using different frequency and strain amplitude. It has been found that the damping characteristics were dependent on measurement parameters, change rate of temperature, vibration frequency and vibration amplitude, and it has been found that the high damping capacity is related to a reversible microstructural movement of interfaces, including martensite variant interfaces, twin planes, martensite-perent interfaces, and it is related to the interaction between martensite with precipitates, vacancies, dislocations, impurities and other defects.