Dynamic Rigid-Plastic Response

Abstract

Static deformation of elastoplastic structures applies only if the loading magnitude is less than the plastic collapse force Fc. With impact or explosive blast loading however, the structure can be subjected to an intense but short-duration pressure or force pulse that exceeds the plastic collapse force and initiates structural collapse. Here we begin with the simplest structural model — a rigid-perfectly plastic cantilever — and explain how characteristics of intense loads (F >F c) influence the structural deformation. The analysis of this deformation uses dynamic equations of motion rather than the equilibrium equations used in previous chapters. First, the dynamic behavior of a rigid-perfectly plastic cantilever subjected to a load or a force pulse at the tip is examined. Then the slightly different response of a cantilever struck by a colliding body is studied in detail to reveal an additional transient phase of deformation. For both steady loads and impacts, an elementary model based on the rigid-perfectly plastic constitutive approximation is used to calculate the deformed shape as well as the energy dissipation during the process of deformation.