Ballistic Limit Predictions with Quasi-Static Cavitation Fields

Recent work on ductile hole enlargement under plane-stress conditions has revealed that while the internal pressure does not reach a saturation level, the energy increment required to create a nominal hole volume increment admits a finite asymptotic value. This specific cavitation energy, which is identified with the cavitation pressure required for plane-strain and spherical cavitation patterns, suggests a possible new view of cavitation states in energetic terms. Based on the specific cavitation energy the ballistic limits of monolithic targets are estimated from a simple energy balance and residual velocities are found from the Recht-Ipson formula. This plate perforation model is independent of projectile head profile and neglects friction. Albeit the simplicity, comparison with experimental and numerical data from various sources, for conical and ogival-nose projectiles, shows good agreement. In fact, over a practical range of h/D ratio, residual velocities are bounded between plane-stress and plane-strain predictions, gradually shifting from plane-stress limit to plane-strain bound as h/D increases. Spherical cavitation fields are also discussed in conjunction with limits of validity of cavity expansion models and connection between plane-stress cavitation and the ultimate tensile stress is demonstrated.