Treating rotor systems with SMA springs to vibration control: Theoretical model and experimental validation

Abstract

During run-up or run-down, a flexible shaft has to pass through critical speeds where vibration amplitude rises sharply, posing mechanical failure and reduced operational efficiency; hence, vibration control is crucial. In this work, a shaft has been theoretically modeled using the Euler–Bernoulli beam (EBB) considering the rotational effect. In which the use of shape memory alloy’s (SMA) characteristics in springs has been proposed as a novel vibration control mechanism. SMA springs exhibit variable stiffness governed by the martensite volume fraction, allowing tuning of the critical speeds. This stiffness has been evaluated at 31°C–72°C. Utilizing this in theoretical model, first natural frequency shifts by 16%, and amplitude reduced by 45.87%. Verification has been performed via experiments for a shaft supported conventionally by bearings and proposed SMA spring-support. Six SMA springs were arranged to support one shaft end, and thermal actuation achieved through Joule heating. This resulted in the shift of 7% noted from displacement and acceleration signals in the first critical speed during run-up and run-down. At critical speed, the amplitude has been reduced by 50%, indicating that SMA spring tuning enables safe crossover and effective vibration control, thereby can be controlling shaft vibrations.