Modified Zerilli-Armstrong Constitutive Model Describing the Strength and Localizing Behavior of Ti-6A1-4V

摘要

Modeling localizing behavior (e.g., shear instability) of metals such as Ti-6Al-4V has been an important goal for some time in the study of ballistic impact and penetration phenomena. Toward this end, Zerilli and Armstrong proposed a constitutive model for metals with a hexagonal closely packed crystal structure that addressed the shear instability of some of these materials. This model was fit to Hopkinson Bar data obtained at strain rates from 1,000 to 50,000 per second. Several modifications of the model were made in order to fit the data better, although the dominant physics-based aspects of the model were not changed. The fit was excellent, with an average error of only 1% in the predicted stress over the range of experimental strains and strain rates. The modified form of the Zerilli-Armstrong model was installed into the Lagrangian shock-physics code EPIC1 and tested in a series of simulations. Shear localization was predicted in simulations of two experiments where the phenomenon was observed: a Taylor-Anvil experiment and a ballistic limit velocity ( V50 ) experiment. Good agreement was obtained as well in simulations of two series of penetration experiments; impact velocities ranged from 1100 m/s to 2000 m/s.