MULTI-DEGREES OF FREEDOM MODEL FOR DYNAMIC BUCKLING OF AN ELASTIC-PLASTIC STRUCTURE

The dynamic elastic-plastic buckling phenomenon is studied using a mul ti-degrees-of-freedom model which retains the influences of axial and lateral inertia and the effects of initial geometrical imperfections. The process of buckling is considered as a quasi-bifurcation of an ela stic-plastic discrete system together with an analysis of the post-bif urcation behaviour. A lower bound to the initial kinetic energy causin g a quasi-bifurcation of the model is defined as the initial kinetic e nergy at the transition between the response, when governed only by a uniform compression, and a response which involves an overall bending as well as compression. The critical impact energy is defined as an en ergy causing a loss of dynamic stability of the model. The final buckl ing shapes and the corresponding critical quasi bifurcation times are determined for a model with a particular set of parameters and subject ed to several impact masses having different initial impact velocities . The range of application of a quasi-static method of analysis for th e considered model is discussed. The initiation of buckling predicted by the model is compared with some experimental results on the high ve locity collision of metal rods, reported previously in the literature. Copyright (C) 1996 Elsevier Science Ltd.