The Hugoniot equation of state, elastoplastic transition, and spall behavior of the Fe–36Ni Invar alloy were systematically investigated over a pressure range of 3–33 GPa. The Hugoniot elastic limit was determined to be between 0.8 and 1.0 GPa. Within the investigated pressure range, the shock velocity (Us)–particle velocity (Up) relation is linear, expressed as Us=3.703+1.888Up. The spall strength of Invar, determined using the acoustic method, is found to increase with shock stress, ranging from 2.5 to 3.7 GPa.
Li et al. (Wed,) studied this question.