Experimental Investigation of Dynamic Characteristics of Metal Coated Buckled Micro-Beams with Electrothermal Modulation of Residual Stress

Buckled beams show interesting dynamic behaviour due to geometric nonlinearities present in them. They present a novel platform for study of nonlinear phenomena. Since the buckled deflection is governed by the magnitude of residual stress present in the beam, incorporating a provision for tweaking the state of stress can facilitate experimental investigation of nonlinear behaviour. In this work, we use metal-coated, buckled, micromechanical beams as the structural platform and by applying an appropriate voltage to the thin metal layer, we alter their state of stress. We measure the natural frequencies of the beam at each applied voltage and study how the frequencies evolve with change in the resulting residual stress. As the applied voltage increases, the first and second natural frequency shift close to each other and a crossover occurs between them. Near the crossover point, the mode shapes are distorted as a result of modal interactions.