Modelling of Dynamic Behaviour of Elastic-Plastic Structures under Impact

It is much more difficult to predict the dynamic behaviour of elastic-plastic structures compared with the corresponding quasi-static one because of complicated loading conditions and the effect of inertia. By assuming that the quasi-static structural and interface behaviour of a structure is specified and its dynamic deformation mode is similar to the quasi-static one, two mechanical models, namely the Stick Model and the Non-Stick Model, are proposed in order to predict the dynamic behaviour of the structure under a rigid-body impact. Each model contains two lumped masses and two linear/non-linear springs. Whilst spring 2 represents the mechanical property of the interface between the structure and the impinger, spring 1 represents the elastic-plastic behaviour of the structure, no matter the latter is strain-hardening, perfectly plastic or strain-softening in the plastic stage. With the complicated deformation history involving loading, unloading and reversed loading being taken into account, the large dynamic deformation process can be completely traced and the final deformation can be predicted by these models. Finally, to verify the validity of the mechanical models proposed for real structures, impact tests on simply supported beams were conducted and the agreement is good.