An atomic view on spall responses of release melted lead induced by decaying shock loading

Knowledge of spallation behaviors of partially melted metals, as well as the ones of solids and liquids, is critical for understanding the complete spall responses of metals to a wide range of loading strengths. However, compared with traditional spallation in solids, the spallation of liquids, especially of partially melted metals, receives considerably less attention despite some advancements in recent years. In the present work, spallation behaviors of partially melted/completely melted Pb under various decaying shock loadings are investigated. The effects of peak free surface velocity on the incipient spall strength of the partially melted Pb are uncovered, which is attributed to the difference of melting degree. Our results suggest that the incipient spall strength decreases with the growing melting degree for the partially melted Pb. Besides, incipient spall criterion, as well as damage evolutions at the later stage, is discussed. It is found that, after the incipient spall takes place, the total void volume linearly increases with time evolutions regardless of the detailed void mechanism for the volume increment. The increasing rate grows with the promoting melting degree even under the same tensile strain rate and initial temperature. For a liquid Pb, the increasing rate is governed by the tensile strain rate. Physical reasons for the different behaviors between partially and completely melted metals are analyzed.