Dynamic failure of titanium: Temperature rise and adiabatic shear band formation

One of the most important issues related to dynamic shear localization is the correlation among the stress collapse, temperature elevation and adiabatic shear band (ASB) formation. In this work, the adiabatic shear failure process of pure titanium was investigated by dynamic shear-compression tests synchronically combined with high-speed photography and infrared temperature measurement. The time sequence of important events such as stress collapse, ASB initiation, temperature rise and crack formation was recorded. The key characteristics of ASB, such as width, critical strain, temperature, propagation speed and cooling rate were systematically studied. The maximum propagation velocity of ASB is found in this work to be about 1900 m/s, about 0.6C_s (C_s is the shear wave speed). The maximum temperature within ASB is in the range of 350–650 °C, while the material close to ASB is also heated. The cooling rate of ASB is on the order of 10⁶ °C/s, indicating that it needs a few hundreds of microseconds for the ASB to cool down to the ambient temperature. One important observation is that the apparent temperature rise occurs after ASB initiation, which indicates that it might not be the causation but the consequences of ASB. Further efforts are called for confirmation of this notion because of its significance.