INFLUENCE OF FRICTION ON A DOUBLE CASED FRAGMENTING WARHEAD

Abstract

The interface condition between the different casings in a multi-cased fragmentation charge is essential for its fragmentation behaviour. In this study, a double cased controlled fragmentation charge with a smooth outer casing and an internal grooved inner casing is considered. In particular, the influence on friction between the inner and outer casing on the fragmentation behaviour is studied using numerical simulations and experiments. In the numerical simulations, the friction coefficient in the contact between the inner and outer casings is varied. Experiments on charges with different interface treatments between the casings are performed with various diagnostic tools in order to capture the deformation, fragmentation and acceleration of the casings. Three different interface treatments that give rise to different friction coefficients are tested; a shrink-fit joint, a thin layer of lubricant grease between the casings and a Teflon layer on the outside of the inner casing. It is found that the amount of friction between the casings influences both the deformation before fragmentation and the resulting shape of the fragment from the outer casing. For the highfriction conditions, one large and several small fragments are produced for each diamond on the inner casing. The low-friction condition results in long zigzag-shaped stripes of materials originating from the casing material closest to the grooves and many small fragments from the casing material between the grooves.