Fragmentation behavior and fragment size characteristics of metal rings subjected to internal explosive loading of hollow-charge

The dynamic responses of metal rings subjected to high strain-rate loading are important issues in the design of munitions and armaments. However, limited work has been conducted to investigate the fragmentation behavior and fragment size characteristics of metal rings subjected to internal explosive loading of a hollow charge. In the present work, specimens with different thicknesses of metal rings and different radii of hollow cores were experimentally and numerically tested. It was found that, during the expansion of metal rings, some slightly deformed grains formed near the inner surface. These deformed grains made the inner surface of the fragments step-like, and were precursors to rupture. Large and small voids could initiate within some relatively thick rings during the expansion of the rings, and some cracks initiated from these voids and propagated towards the outer surface and inner surface. The circumferential rupture strain decreased dramatically as the radius of the cylindrical hollow core increased. For the specimens with the same hollow-charge, the circumferential rupture strain decreased as the thickness of the metal rings increased. In addition, it was easier to form strain localizations at the inner surface when the specimen had a larger height of the metal rings, resulting in a smaller circumferential width of the fragments for the specimen with a larger height of metal rings. Based on the fragment size characteristics, a modified formula was established and validated experimentally and numerically. The results indicate that the proposed formula is accurate and reliable in predicting the average circumferential width of the fragments from metal rings subjected to internal explosive loading of a hollow charge.