Publications Details
Penetration in metal targets: A numerical and experimental study of the metal-tack fastener applied to high strength steels
A dynamic finite element analysis was performed to study the penetration mechanics of a commercial fastener called Metal-Tack{reg sign}. This study evaluated the fastener and identified parametric changes required for attachment to AISI 1070 steel (R{sub c} = 26), a material harder than the fastener was designed for. A set of baseline calculations was performed to evaluate the fastener's performance in yellow brass, a much softer material. The analysis indicated that a driving energy of 3.03 ft{center dot}lbs was required to drive the tack into yellow brass. Excellent correlation of this model with experimental data provided confidence for applying the model to AISI 1070 steel. Tack performance was investigated with respect to variations in driving energy and tack strength. The results demonstrated that increasing driving energy was not sufficient for a successful attachment in the steel. An increase in tack strength was also required. Higher tack strength was obtained by increasing the heat treat specification of the tack material, Carpenter R.D.S. steel, to obtain a hardness of R{sub c} = 60. With this increase in strength and a driving energy of 20.8 ft{center dot}lb, the results indicated that the tack would attach but develop high plastic strain (21.5%) during attachment. The calculations were confirmed with tests using a high energy pyrotechnic driver developed to attach the tack. Finally, a geometry modification intended to reduce stress concentrations in the tack was evaluated experimentally but not computationally. The experimental results indicated an improvement in the tack strength and attachment quality. 4 refs., 19 figs., 4 tabs.