Modelling projectile impact on ballistic helmets

These prototypes are then tested by means of starrdardized drop tests to determine the resulting head accelerations, and thrrs the relative protective capability of the design with respect to applicable standards. If the desired results are not obtained (e.g. the peak headform acceleration is above the performance criteria), a change of design may be called for. This would typically involve producing additional prototype helmets in alternate material densities or shell constractions for further testing. Characteristically, the weight, cost, comfort and health performance are addressed after suitable impact performance is obtained this may require further variation of materials. 

Most computational codes provide automatic element distortion checking, element re-meshing and element elimination, which are necessary when large 

Most of these simulation results correlate well with experimental results when the rate dependency in the material is taken into account. However, none of them considered the effects on the human head in their simulation, due to the limited access to such a finite elements (FE) model. The combination of a detailed FE model of the human head and a good model of the helmet is an important criterion, especially as a design guideline for the helmet. 

Baumgartner and Willinger (2003) have studied the rear effect caused by ballistic impact of a projectile fired towards the helmet of military personnel. They have developed finite element models combining the human head, based on its principal anatomical components, and a ballistic hehnet, and subjected these to the impact of a steel bullet. Average pressures inside the brain, pressure in brain tissue, the force applied to the human head, and the global strain energy of the skull were calculated. A linear fracture of the skull was predieted in the ease of the 

3 The initial meshes for the Kevlar helmet with the 9mm FMJ before impact (Tham et al., 2008). 

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