Separation of the elastic waves' system in pre-stretched bar devices

Abstract

The loading mode generated by Kolsky bars apparatus is limited due to physical reasons to a duration time of around 0.4 ms. This is not suited in the characterization of high ductility metallic alloys up to fracture at moderate strain rates, since the duration time is too short. The pre-stretched bar device is a good candidate to characterize these materials up to the moderate strain rates. Unfortunately, the elastic waves are generally not separated in time at measurements points in the input bar, and post treatment leads to assumptions. A configuration of the pre-stretching conditions that ensures no superposition of the elastic waves' system developed along the input bar is thus proposed so as to fulfill standard data analysis requirements, i.e. without any assumptions. However, a drawback of the proposed device is that one of its hydraulic devices generates a loosen tail. This statement comes from a FE numerical model of the whole set-up including the generation of the loosen tail. Finally, an analytical correction to cancel the loosen tail is proposed and validated with respect to a numerical model featuring ideal pre-loading conditions.