Dynamic Compression Behavior Of AISI 4340 Steel Under Various Strain Rates And Temperatures

Abstract

In this study, dynamic compression behavior of AISI 4340 steel alloy was investigated with split-Hopkinson and Taylor impact tests and numerical studies. Dynamic compression tests at strain rates of 725, 1500, 2000 s-1 at room temperature and at high temperatures of 150 and 250 °C were done using split-Hopkinson pressure bar. Taylor impact tests with the impact velocities of 245, 324 and 336 ms-1 were performed with cylindirical specimens to observe dynamic deformation behavior at impact conditions. Numerical studies using Ls-Dyna 3D finite element method were conducted to investigate temperature and stress distribution of specimens during Taylor impact tests. Experimental results revealed that as strain rate increased, yield and ultimate compressive strengths and total strains increased at room temperature at dynamic compression tests. At elevated test conditions, both strengths decreased and total strains increased due to softening effect. Taylor impact test results showed that all the specimens exhibited mushroomed deformation and increase of impact velocity led to shear crack and fracture at the end of deformation process. Numerical results indicates that highest temperatures were obtained at the impact surfaces for three impact velocities. In addition, the increase of impact velocity enhanced the stress distribution at deformed regions near impact surfaces.