By considering the elastic effect and large deflection,this paper studies the dynamic response of an elastic,perfectly plastic hinged-free beam,of which one end is hinged and the other end free,subjected to a transverse strike by a travelling rigid mass at the mid-span using finite difference method.Attention is focused on the instantaneous distributions of bending moment and curvature as well as the deformation history.It is shown that the interactions between the elastic flexural wave and the plastic flexural wave make some different characteristics when compared with results based on a rigid,perfectly plastic model.The response process can be divided into several deformation stages and there exits stationary and travelling plastic bending hinges,some of which is similar with the classical rigid,perfectly plastic analysis.There is a dangerous high curvature region between the two travelling plastic hinges,in which the local plastic collapse may take place.The results can provide an approximate estimation of local plastic failure position and deformation profile of hinged-free structures subjected to impact loading.