Modeling non-eroding perforation of an oblique aluminum target using the Eulerian CTH hydrocode

In the past, Eulerian hydrocodes were not able to treat rigid body penetration/perforation problems very well. This was attributed to several factors. Velocities are defined either at the cell faces or cell corners, and all other flow-field variables are defined at the cell center. The implication is that materials in a mixed cell (cells containing more than one material) have the same velocity field and are therefore treated as welded or bonded so that sliding does not occur. Additionally, one strength is defined for a mixed cell so that in a cell containing both a hard and a soft material, the hard material can more easily deform since its strength is some average of the hard and soft material. To overcome these deficiencies, a boundary layer interface algorithm for sliding interfaces (BLINT) model was incorporated into the Eulerian CTH hydrocode for two-dimensional problems only. The BLINT model has been extended to three dimensions in later versions of the CTH hydrocode. This paper examines the ability of the CTH hydrocode, using the three-dimensional (3-D) BLINT model, to predict the experimental results in which a non-eroding projectile perforates an oblique aluminum target. The experiments consisted of a hemispherical nose 4340 steel penetrator with a length of 88.9 mm and a diameter of 12.9 mm perforating a 26.3 mm thick 6061-T651 aluminum plate at 30° obliquity and a nominal impact velocity of 400 m/s. Hydrocode predictions are compared to the experimental results. Strengths and weaknesses of the 3-D BLINT model are discussed.