Large deflections of metallic sandwich and monolithic beams under locally impulsive loading

A rigid-perfectly plastic model is adopted to predict the dynamic response of fully clamped sandwich and monolithic beams subjected to localized impulse. Large deflection effect is incorporated in analysis by considering interaction between plastic bending and stretching. Based on the principle of energy equilibrium, a membrane factor for metallic sandwich beams with nonuniform cross-section thickness is derived to consider the effect of axial force induced by large deflection. Then, the dynamic response solution is obtained for the large deflection of metallic sandwich beams subjected to localized impulse. In addition, tighter 'bounds' of the solutions for sandwich beams are derived by using the inscribed and circumscribed squares of a new yield criterion including the core effect. As a degenerated limit case, solution for the large deflection response of solid monolithic beams is also obtained. The present solutions are in good agreement with finite element (FE) results and lie in the 'bounds' of the solutions. It is demonstrated that the axial (membrane) force associated with stretching plays an important role in the dynamic response of large deflections; in comparison with small deflection solutions, the axial (membrane) forces substantially stiffen the metallic sandwich and monolithic beams.