Spall behavior and mechanisms of tantalum under ramp wave unloading: Investigating the causes and occurrence of multi-spallation

Le résumé fourni par la source

Spallation is a typical fracture phenomenon in materials under dynamic loading, with its behavior significantly influenced by stress history, particularly strain rate. Exploring the mechanisms of spallation damage under different stress history and establishing corresponding failure models remain critical challenges in this field. This study investigates spallation in tantalum (Ta) under ramp wave unloading, revealing distinct damage mechanisms influenced by stress history. Unlike isentropic unloading, ramp waves generate segmented unloading and non-uniform strain rates, resulting in milder, widely distributed spallation damage. At flyer velocities exceeding 400 m/s, Ta exhibits multi-spallation with an anomalous 8.6% decrease in spall strength (5.8 GPa to 5.3 GPa). Wave propagation analysis shows interacting rarefaction waves create extended tensile regions, promoting dispersed damage and multi-spallation. Although spallation follows classical void nucleation-growth models, significant differences in void size/density emerge between spallation zones due to localized strain rate variations (higher rates suppress void growth). These findings highlight stress history’s critical role in governing damage distribution and failure modes, demonstrating how ramp wave-specific loading paths alter microvoid evolution dynamics. The work advances understanding of rate-dependent spallation mechanisms and provides a framework for modeling material failure under complex dynamic loading.

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