Shear bands formation in different engineering materials subjected to dynamic compression

During dynamic compression tests, different mechanisms occur at the micro-structural level, resulting in a competition among strain hardening, strain rate hardening and thermal softening. The softening effect is due to dynamic recovery and dynamic recrystallization. If the hardening effects become less effective than softening ones, the material could become unstable, forming narrow bands in which the deformation concentrate involving (quasi) adiabatic conditions and an unpredicted catastrophic failure occurs. These narrow bands are called Adiabatic Shearing Bands (ASB). This type of instability can be observed in different type of materials: polymeric materials due to combination between temperature and strain rate, and in Titanium alloy and Aluminum alloy due to strain rate effects. In this work, an analysis about adiabatic shear bands on three different types of materials is described. Compression tests of Titanium alloy (Ti-4Al-6V), Aluminum alloy (AA 7075-T6) and Polymeric material (Polypropylene) have been carried out in quasi-static and dynamic condition, the lasts ones by a Split Hopkinson Bar.