Study of notched MEMS specimen: elasto-plastic modeling and experimental testing

This paper investigates the effect of stress and strains concentration, due to the notch presence, on the elasto-plastic behavior of gold microstructures subjected to tensile loading under electrostatic actuation. A kinematic model for the test microstructure which relates the experimentally measured deflection to the induced stress in the central specimen with applied electrostatic load is developed. The local maximum stress and strains at the notch root are analytically estimated using the Neuber's rule and verified through a detailed non-linear coupled-field electric-structural finite element method (FEM)-based analysis. Several experimental tests are carried out to analyze the accumulation of plastic strain and the consequent development of plastic hinges induced in the central notched specimen due to repeated cyclic tensile loading by measuring the corresponding deflection with each loading cycle. The comparison between the failure condition observed experimentally in the test notched specimens and the FEM-based simulation results shows that the notch acts as stress and strains raiser fostering the initiation and expansion of plastic hinges in the thin film gold specimen which can lead to the specimen breakdown.