13th International Conference on Fracture June 16–21, 2013, Beijing, China -4- dummy. The vest and testing dummy was taped to a large flat board to support it and keep the midriff area of the dummy perpendicular to the ground. A table was placed in front of the dummy and the centre of the models taped to the vest 25 cm above the table surface. A 9 mm calibre handgun was used in the experiment with Magtech 9 mm luger centerfire full metal jacket ammunition. The models were shot from a distance of 1 m and fired from a position perpendicular to the model surface. The experiment was filmed with a SA1 high-speed digital video camera with a 55 mm lens and capture rate of 16000 fps. The lighting was achieved with three 1000 W quartz halogen lamps. A large white plastic board was held by clamps behind the model. This board acted as a light reflector to increase the brightness and track the backspatter from the models. Large white sheets of blotch paper were attached for each experiment to the table in front of the models, the plastic board reflector, and the ground immediately around the setup. This was so the spattered particles could be observed and recorded. 3. Computational Simulation Conventional FEA is not suitable for high impact fracture simulations due to a number of factors including capturing the natural crack initiation and propagation, separation of failed elements, maintaining the integrity of elements in highly non-linear deformations, and capturing highly fragmented filamentary crack paths [24]. Consequently, Smooth Particle Hydrodynamics (SPH) was adopted as a suitable method due its mesh free nature. SPH solves a system of partial differential equations with the domain discretised into a series of particles that represent specific material volumes. SPH modelling has been successfully applied to fluid flow problems in the past. More recently there has been a growing interest in modelling solid deformation problems with SPH [24-29]. SPH is ideally suited to modelling the backspatter from a projectile impact due to its proven ability in modelling fractured discrete structures and damage evolution. Figure 2. Computational simulation configuration (dimensions in mm, not drawn to scale) Table 1. Material properties for MDF and polycarbonate used in the computational model Material Density Shear Modulus Yield Stress Bulk Modulus Failure Strain Reference MDF 750 kg/m3 1357 MPa 42 MPa 2778 MPa 0.5% [30, 31] Polycarbonate 1190 kg/m3 785 MPa 62 MPa 3010 MPa 100% [32]
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