High strain rate constitutive modeling of aluminum nitride including a first-order phase transformation

This work presents a computational constitutive model for materials exhibit ing a first-order phase transition. The model can represent both recoverabl e and non-recoverable volume loss characterized by first-order phase transi tions. Aluminum Nitride (AlN) is used to demonstrate the model. AlN has a f irst-order phase transition from the wurtzite (hexagonal) structure to the rock salt (cubic) structure. This phase transformation has been observed un der static high pressure testing and inferred to be occurring under high st rain rate shock wave loading. The phase transition begins at an approximate hydrostatic pressure of 16GPa where a 20% volume loss commences. The volum e loss has been inferred to be non-recoverable. The model used for this stu dy was previously developed for crushable materials, but is demonstrated he rein that it can be straightforwardly applied to materials that exhibit a f irst-order phase change. Constants are obtained for the model using AlN tes t data. Plate impact experiments are simulated using the model, demonstrati ng the ability of the model to capture the material behavior. The model is also used to evaluate the recoverability of the volume loss and implies tha t the volume loss is non-recoverable.