Measuring Structural Evolution in the Dynamic Plasticity of FCC Metals

Above uniaxial strain rates of 10(4) s(-1), FCC metals exhibit a rapid increase in strength. Accurate modelling above this behavioural transition is hindered by an absence of measurements which can be used to separate the instantaneous and more permanent, structural contributions to strength. In this paper we present a direct impact Hopkinson pressure bar system, with photon Doppler velocimetry applied to the striker bar, allowing explicit verification of both the rise and equilibration times in the experiment. The system presented is capable of performing interrupted tests at strain rates up to 10(5) s(-1), well above the transition.