Multiple impact penetration of semi-infinite concrete

An experimental study was performed to gather multiple impact, projectile p enetration data into concrete. A vertical firing range was developed that c onsisted of a 30-06 rifle barrel mounted vertically above a steel containme nt chamber. 0.41 m cubes of an Air Force G mix concrete were suspended in w et sand and positioned in the steel chamber. The concrete targets were subj ected to repeated constant velocity impacts from 6.4 mm diameter steel proj ectiles with an ogive nose shape and a length to diameter ratio of 10. A la ser sight was adapted to the rifle to ensure alignment, and a break screen system measured the projectile velocity. After each impact, the projectile penetration and crater formation parameters were recorded. The penetration and crater formation data were consistent with single impact penetration da ta from previous studies conducted at Sandia National Laboratories. In addi tion, an analytic/empirical study was conducted to develop a model that pre dicted the penetration depth of multiple impacts into concrete targets. Usi ng the multiple impact penetration and crater formation data, a single impa ct penetration model, developed by Forrestal at Sandia National Laboratorie s, was extended to account for the degradation of the target strength with each subsequent impact. The degradation of the target was determined empiri cally and included in the model as a strength-modifying factor. The model r equires geometry parameters of the ogive nose projectile, projectile veloci ty, the number of impacts, and target compressive strength to calculate the overall penetration depth of the projectile. Published by Elsevier Science Ltd.