Shape Memory Alloy Actuator: A Thermal Heat Engine

A Nitinol coil spring is trained to a short "memory" length in its high-temperature austenite phase. Cooled and stretched, it stays long and soft as twinned martensite; heated past its transformation range it snaps back to the trained shape, lifting a real hanging weight. This simulator models that cycle with the cosine (Liang–Rogers) austenite-fraction transformation law, complete with the thermal hysteresis loop between heating and cooling, and renders the spring as a live 3D coil whose pitch and length respond in real time. Tune heater power, ambient cooling rate and load mass, or flip on the thermostat Auto-Cycle to watch the actuator run itself as a continuous heat engine, converting electrical/thermal energy into mechanical lift.