The Dynamic Behaviour of Mild Steel

Abstract

<p> Multiple impact tests were performed on mild steel. The pulse durations ranged from 15 to 250 milliseconds. Peak stresses extending to 135,000 p.s.i. were attained. </p> <p> A dynamic model, based on dislocation dynamics, was derived for polycrystalline metals and made specific to mild steel. The model provided a means of indirectly determining the dislocation velocity-stress exponent 𝑛 by experiment. </p> <p> An empirical flow function was evaluated which related dynamic load conditions to plastic deformation. This function is a further extension of the dynamic model. Several dislocation parameters are grouped together to pennit experimental evaluation of the strain rate effect on crystalline material. </p> <p> Experimental studies indicated that a given strain: </p> <p> 1) if produced by a single pulse, can be estimated by evaluation of the flow function for that load-time trace, or, </p> <p> 2) if produced by multiple impacts, can be estimated by the cumulative flow function, a summation of the flow functions for all impact traces. </p> <p> The multiple impact tests established the flow function as an equation of state. The plastic deformation could then be determined for a given dynamic load as long as the strain history is known. </p> <p> The theoretical model was used to support the experimental findings. </p>