Study on impact behavior for cylindrical tubes with and without pellets

Abstract

The dynamic buckling tests using cylindrical tubes with and without internal pellets were carried out to investigate the impact behavior. Various materials of cylindrical tubes and pellets were used to examine the buckling mode and the maximum loads at several impact velocities. In the case of low Young's modulus and low yield strength pellets, the influence of pellets was small because of the small load share of pellets, so the “W” shape of deformation shapes and the maximum impact loads were almost the same of those of empty tubes. On the other hand, the tubes with high Young's modulus and high yield strength pellets indicated different behaviors compared to the empty tubes because of the large load share of pellets. At low impact velocity, pellets with high yield strength caused the strengthening effect and increased the lateral stiffness for tubes. As a result, the pellets led to increase of impact load, decrease of deformation and change of buckling mode to the “S” shape. At high velocity, the strengthening effect of pellets made the tubes stiffer, but led to fracture by the constraint effect of pellets on plastic deformation. The deformation of tubes was compared to Euler's equation, and it was confirmed that the Euler's equation could be applied at the low impact velocity. However, it was not effective for the high velocity impact because of local deformation at the impact side. FEM analyses will be conducted to clarify the deformation shape, maximum load and the mechanism of fracture at high impact velocity as a further study.