| || Dynamic Yield Strength of Mild Steel under Impact Loading
Author : Manjit Singh;Sood, D.;Gautam, P. C.;Sewak, Bhupinder;Mathew, Thomson;Gupta, R. K.;Kumar, R.;Sharma, A. C.
Source : Defence Science Journal ; Vol:58(2) ; 2008 ; pp 275-284
Keywords : Ball impact;Gas gun;Flash ray;Strain rate;Dynamic yield strength;Autodyn simulation;Strength model;Eulerian solver;Johnson & Cook strength model
Abstract : Dynamic yield strength of mild steel is estimated when impacted by the steel balls launched by two stage-light gas gun in the velocity region 1900-5200 m/s. The ball impact provides a radial momentum to the target material resulting in a crater which spreads out until it is stopped by the target yield strength. The dynamic yield strength of target metal is calculated by incorporating the densities of ball and target material along with experimentally measured crater radius and impact velocity in modified Bernoullis equation. The dynamic yield strength of mild steel has been found to be around 2000 MPa under high velocity impact, causing the material to deform at strain rates > 106 s-1. Impact phenomenon was also simulated on Autodyn 2-D using Euler processor. Simulation results reveal that the target material is subjected to the highest strain rate of 105 - 106 s-1 at the impact point and then decreases as the penetration progresses through the target. Predicted results of crater radius depth, and splash of material match with the experimental measurements.