A theoretical and numerical study on the perforation of thin metallic plates by high speed long rods

Abstract

An understanding of the response and perforation of thin plates to high speed rod impact is very important for design and assessment of protective structures such as whipple shields for spacecrafts and spaced armors in tanks/armoured vehicles. To this end, a theoretical and numerical study is presented herein on the perforation of thin metallic plates struck normally by long rods at velocities greater than 1.5 km/s approximately. Firstly, a theoretical model for erosion length of a long rod perforating a thin metallic plate is developed on the basis of the laws of conservation of mass, momentum and energy, which can be viewed as an extension of the previous work. In particular, an empirical equation for α (angle of relaxation) is first derived on the basis of the analysis of numerical results obtained in the present study and then verified against available test data. Secondly, an overview is presented of the existing equations for hole diameter. Finally, an empirical equation for hole diameter in thin metal plates is developed by means of dimensional analysis. It transpires that the theoretically predicted erosion lengths are in good correlation with the numerical (SPH) results for long rods perforating thin metallic plates both of which are made of different materials at impact velocities greater than 1.5 km/s approximately. It also transpires that the newly developed dimensionless formula for hole diameter produces better and more consistent results than those from the existing equations in a wider range of impact conditions.