Investigations Into the Physical Mechanisms That Facilitate Transformation Hysteresis in Shape Memory Alloys

130 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008.Influences of energy dissipative mechanisms are rationalized using a theoretical approach which combines micro-mechanics and thermodynamics into a thermo-mechanical framework. Models are formulated for the thermal and stress hysteresis based on a thermo-mechanical framework so as to shed light into differential hysteresis magnitudes. Current theoretical formulations consider energy dissipation from a phenomenological point view and satisfy the second law of thermodynamics by considering a dissipative potential. In the current study, an earlier thermo-mechanical formulation is advanced beyond phenomenological considerations to include the effects of micro-scale plasticity. With this, the hysteresis models can account for energy dissipation resulting from strain energy relaxation. The current modeling approach provides intuitive predictions of the experimentally observed behavior particularly a growing hysteresis with increasing stress for NiTi alloys.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD