Experimental analysis of dynamic behavior of elastic visco-plastic beam under repeated mass impacts

Abstract

Repeated impact behaviors of an elastic visco-plastic steel beam struck by a hard sphere are experimentally examined in this paper. The interaction between impact bodies, behaviors of sub-impacts, wave propagations and dynamics of the beam are tested to get a better understanding into the mechanism of repeated impacts. At the four different impact locations on the beam, thirty repeated-mass-impact tests are conducted for each impact location under identical initial conditions except for the accumulated deformations. The effects of repeated impacts and impact location on the sub-impact behaviors, local contact deformations, wave propagations, high-frequency vibrations and long-term beam responses are analyzed. The sub-impact phenomenon is observed. The deterministic and random features of the influences of repeated impacts on the behaviors of sub-impacts are observed. The deterministic feature similar to the elastic shakedown phenomenon is found to occur for the first sub-impact behaviors, such as the kinetic coefficient of restitution, residual deformations and early wave propagations. The random feature is found to occur for the second sub-impact behaviors as well as the vibrational modes and long-term stress and displacement responses. The couplings of sub-impacts, wave propagation and high-frequency vibrations make the repeated impact behaviors of flexible structure much more complicated than single impact.