Helical Coils as Impact Load Dispersers

Abstract

The concept of using tangentially loaded helical coils as impact load dispersers was examined experimentally and theoretically in order to evaluate its effectiveness in minimizing the amplitude of shock loading. It was found that the initial stress pulse decomposed into several pulses of continuously decreasing amplitude as it propagated along the coil. The initial elastic compressive pulse became sinusoidal with frequencies equal to the natural frequencies of the coil shortly after the initial disturbance. It was observed experimentally that there was always a component of the stress pulse which propagated along the helical coil at a velocity close to the bar velocity, (E/ρ)1/2 . The theoretical analysis showed that there are two modes of wave propagation for the radial flexural and tangential deformation. The group velocity for the tangential deformation modes increases quickly from zero to the bar velocity as the wavelength decreases, especially at a large principal radius of the curvature. The group and the phase velocities for the twist and axial flexural deformation of the coil are also given.