Response of periodically stiffened shells to a moving projectile propelled by an internal pressure wave

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Response of periodically stiffened shells to a moving projectile propelled by an internal pressure wave

Ruzzene, M. / Baz, A.

The effort dedicated to the analysis of moving loads on elastic structures is justified by the variety of structures subjected to moving loads, which include, for example, bridges, gun barrels, or rails. The vibrations of cylindrical shells induced by a moving projectile propelled by an internal pressure wave are controlled by placing stiffening rings periodically along the length of the shell. An expanding pressure step causes the axisymmetric radial displacement of the shell to be several times higher than that produced by the static application of the same pressure. A critical velocity of the pressure front at which the amplitude of the displacement is maximized can be identified. In addition, the mass of the projectile induces bending vibrations. The shell's response is therefore given by the interaction between the moving projectile, the internal pressure and the shell vibrations. A Finite Element model is developed to predict the transient response of stiffened cylindrical shells loaded by a moving projectile propelled by an internal pressure wave. The model is used to identify the configuration for the stiffening rings that impedes the propagation of waves at critical speed and hence increases the critical velocity, reduces the radial displacement at critical conditions, and therefore stabilizes the overall shell response before and after the projectile leaves the shell. The presented analysis provides guidelines for the design of gun barrels with increased firing velocity, improved accuracy, and enhanced structural stability.