13th International Conference on Fracture June 16–21, 2013, Beijing, China -3- suggested that computer prediction is a useful tool for testing the physics of human ballistic wounding. Many of these studies used LS-DYNA software as the FEA solver [16, 17, 19, 20, 22], and Smooth Particle Hydrodynamics (SPH) [22, 23] was also shown to be useful. Physical experiments can play crucial roles and are essential to understand the complex mechanisms, characterise the associated material behaviour during backspatter, and validate the computational models. For example, the constitutive relations of biological materials, specifically under high strain rates, are often not known, and need to be determined experimentally. In relation to backspatter, the scope and extent of experiments with animals or animal parts are limited because of ethical and practical reasons. Hence there is an urgent need to develop alternative (simulant) material that will enable conducting large number of experiments to understand backspatter and its relationship to the actual events. The key criterion of simulant material is their properties either individually or in combination need to be close to the biological material (skull, tissue, fluid, etc) relevant to backspatter, and thus they are expected to demonstrate similar events under backspatter conditions. This study focuses on understanding the mechanisms of backspatter and evaluates two simulant materials for human skulls to rate their usefulness as a synthetic material for forensic investigations. Secondly, we evaluate the suitability of a mesh-free method called Smoothed Particle Hydrodynamics (SPH) to model the splashing mechanism during backspatter using a medium density fiberboard (MDF) panel, which is compared to the identical experiment. 2. Approach and Methodology Ballistic experiments were conducted at The Royal New Zealand Police College shooting range in the presence of trained firearms experts. The experimental setup is shown in Fig. 1. In the first experiment a series of 100 × 100 mm2 panels made of Medium density fiberboard (MDF) and Polycarbonate (PC) materials were tested. MDF is made up of wood fibers combined with a resin, and made into panels by applying high pressure and temperature. Polycarbonate was also chosen as the material as it is not brittle and thus would not shatter as a result of projectile impact. Figure 1. Experimental setup: the physical model was placed on a Kevlar vest with halogen lighting and recorder using a high speed camera. The assembled physical models were attached to a Kevlar bullet proof vest on a dense foam testing
RkJQdWJsaXNoZXIy MjM0NDE=