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Shape Memory Alloys (SMAs) are a unique class of intermetallic alloys thatcan cyclically sustain large deformations and recover a designed geometrythrough a solid-to-solid phase transformation. SMAs provide favorable actuationenergy density properties, making them suitable for engineering applicationsrequiring a significant, repeated, work output. To facilitate the developmentand validation of an SMA constitutive model considering the evolvinganisotropic material response for High-Temperature SMA (HTSMA), uniaxial andpure bending actuation cycling tests on HTSMA specimens are performed by acustom-built testing frames. The phase transformation characteristics forNi$_{50.3}$TiHf$_{20}$ HTSMA under uniaxial tension/compression and four-pointbending actuation cycles are investigated. The experimental results show thatthe polycrystalline HTSMAs has a strong tension-compression asymmetry underuniaxial actuation cycling loading conditions. Furthermore, the four-point beambending test shows that there is an intrinsic phenomenon when HTSMAs aresubjected to cyclic actuation bending conditions, i.e., the zero-strain neutralaxis shifts as a result of the asymmetric tension-compression phasetransformations and the asymmetric generation of TRIP strains on differentsides of the beam. The conducted experiments provide invaluable information todevelop and improve the SMA constitutive model considering tension-compressionasymmetry and TRIP strain generation within a unified modeling effort. Asfuture work, additional experiments on other HTSMA components, such as torquetubes and specimens with notches or cutouts, under actuation cycling wouldprovide more comprehensive validation data and component performance forHTSMA-based actuators.

Phase Transformation Characteristics of High-Temperature Shape Memory Alloy under Tension, Compression, and Bending Actuation Cycling