Modelling of a nitrogen alloyed steel with application to armour penetration

摘要

The mechanical properties of a nitrogen alloyed steel (HNS) are investigated and material parameters for the Johnson and Cook (J&C) material model are determined. The implementation of the J&C model in Autodyn (AD) 4.1.13 is tested and it is found that the strain rate effect on the J&C flow stress is not appropriately handled. A user developed subroutine is shown to improve the numerical solution. Simulations of the ballistic limit for a 5.56mm AP versus a HNS plate is done and compared to experimental results. It is found that the original AD 4.1.13 implementation gives a considerably lower ballistic limit than the result from the user developed subroutine. The calculated ballistic limit using AD 4.2.02 with the included optional strain rate correction is close to the one obtained with the user subroutine and agrees reasonable well with the experimentally found ballistic limit.