Some selected FEM analyses of motion of a bullet with imperfections while interacting with the barrel

The intended aim of studies on the modelling of a bullet interacting with a barrel is to generale a virtual, computer-based model, experimentally verified for some selected mating conditions, and to become able to predict -with strong probability - processes and phenomena that take place within a system with imperfections. In the case under consideration the problem of contact between the barrel and the bullet has been described with the calculation method based on the penalty function. Calculations were made using the so-called direct-integration procedurę, colloquially called the ,,explicit integration ". Preliminary analysis has been carried out on the effect of the shift of the centre ofmass of the bullet moving in the barrel. Simulation included the bullet displacement along the barrel's axis, with the assumed positions of the centre ofmass -5% and +5% as measured from the bottom and referred to the initial model (0%). Results ofnumerical calculations suggest the effect of shift of the bullet's centre of mass, which -when exposed to complex states of loading - experiences oscillating movements of the bottom and the tip. Additionally, this analysis proves that there is a complex state of stress due to compression, torsion, and bending of the bullet while interacting with the inner part of the barrel. Numerical solutions may support the analytically approached solving of such mechanical system. They may also offer more precise determination of, e.g. initial and boundary conditions for the bullet 's free flight, which is of great significance to the accuracy of fire, and therefore, to the weapons effectiveness.