Underlying mechanism of periodical adiabatic shear bands generated in Ti-6Al-4V target by projectile impact

Periodical adiabatic shear bands are universally observed in titanium alloy targets subjected to a projectile penetration; however, the underlying mechanism is not very clear. In this letter, the response of a Ti-6Al-4V plate against a 12.7-mm armor piercing projectile is investigated, both experimentally and computationally. By introducing a newly developed stress/strain coupling accumulation failure criterion, the cratering, ductile hole enlargement, and spalling processes are simulated, showing agreement with the experimental observations. The failures of the cratering and back spalling are due to the circumferential and tensile stress accumulation damage, whereas the ductile hole enlargement occurs as a result of the periodic loading-unloading cycle of the hydrostatic pressure, thus leading to a periodic array of shear bands. Further studies show that the von Mises stress is relatively stable during the penetration, and therefore the periodic change of hydrostatic pressure leads to the periodic stress triaxiality in the target, causing the periodic strain accumulation.