Correlation of dynamic compressive properties, adiabatic shear banding, and ballistic performance of high-strength 2139 and 7056 aluminum alloys

Abstract

In this study, laboratory-scale Split Hopkinson pressure bar (SHPB) tests were conducted on commercial armor plates composed of 2139 and 7056 Al alloys to investigate their dynamic compressive properties in relation to adiabatic shear band (ASB) formation. The results were then correlated to those of the ballistic performance as measured from V-50 ballistic impact tests. In the SHPB tests, the 2139 alloy was compressed and flattened with traces of cracking, whereas cracks initiated in a shear mode in the 7056 alloy and propagated to produce several pieces. The cracking behavior was further analyzed by interrupted SHPB tests, which confirmed that shear cracking occurred through the formation of deformed ASBs and subsequent locally transformed ASBs. These processes started much earlier in the 7056 alloy; therefore, it showed a lower critical strain for initiating the ASBs and lower resistance to ASB formation. This result corresponded well with the actual V-50 ballistic impact test results, which confirmed the better ballistic performance of the 2139 alloy. The resistance to dynamic and ballistic deformation was quantitatively discussed using the susceptibility to ASB formation.