Dynamic pull-in instability of a thermoelectromechanically loaded micro-beam based on "symmetric stress" gradient elasticity theory

The dynamic pull-in instability of a thermoelectromechanically loaded micro-beam is investigated based on the "symmetric stress" gradient elasticity theory and Euler-Bernoulli beam theory. The beam is subjected to the combined action of an electric voltage, axial static force and a uniform temperature change. By employing Galerkin's method, the nonlinear partial differential governing equation is decoupled into a set of nonlinear ordinary differential equations, which are then solved using Runge-Kutta method. Numerical results show that compared with the size-dependent micro-beam model, the classical elasticity theory in which the size effect is ignored underestimates the pull-in voltage. The effects of size, temperature change, axial force, geometric nonlinearity, fringe effect, initial gap, beam length and width on the pull-in instability of the micro-beam are discussed in detail.