No abstract

Atomistic molecular dynamics simulation was carried out to study interface interactions between a crystal structure and a plastic bonded explosive (PBX) system. In this work, the polymer is hydroxyl-terminated polybutadiene (HTPB), the plasticizer is dioctyl adipate (DOA) and the crystal phase is hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). Experimental RDX crystallo-graphic data show that (020), (200) and (210) crystal faces usually dominate, and these were therefore only these were studied. Interface models were built and interfacial bonding energies calculated to investigate HTPB/RDX adhesion properties in the (DOA+HTPB)/RDX system. Mechanical properties such as Poisson's ratio, Young, bulk and shear moduli were also predicted. The most favourable interactions occur between HTPB-DOA and the RDX (020) crystal face: obtaining crystals with prominent (020) faces may provide a more flexible mixture, with a lower Young's modulus and an increased ductility.

The process of shaped charge jet formation, fragmentation, and penetration in rolled-homogenous armor steel target plates was investigated using the explicit, nonlinear Lagrangian finite element method. The investigation was conducted in two dimensions utilizing an axisymmetric configuration for a shaped charge with a 40 mm cone diameter. The results obtained using numerical simulations were compared to the experimental results obtained from tests. In addition, the dynamic behavior of the jet was compared to the visual data obtained from X-rays to confirm jet formation and fragmentation predictions. The advanced features of the developed shaped charge model include adaptive remeshing to follow the high deformation pattern of the jet, appropriate constitutive material models and equations of state to account for high strain rate, and restart files to allow the simulation to be performed in stages.

Abstract.A Split Hopkinson bar apparatus is a widely used method to obtain material properties at high strain rates. These properties are essential in the development of new materials as well as their associated constitutive models. During routine tests, the surfaces of the bars at the specimen/bars interface were damaged. To check if the damage influenced the signal response, control tests were done using the well characterized Al 6061-T6. Results showed that artefacts were added to the signal. This paper presents the experimental and numerical approaches developed to understand the effects of surface damage. The approach used consists of introducing series of known gaps between input and output bar to simulate a variation of surface damage. The numerical simulations, performed using a hydrocode, were done to confirm that signal response could not be associated with other several types of error in the system.

No abstract