Abstract：The sub-impact behavior of a simply supported beam struck by a round-nosed mass, including the sub-impact phenomenon, sub-impact durations and sub-impact conditions, were tested by a set of sub-impact experimental device self-designed, simulated numerically by the three-dimensional dynamic finite element method and analyzed by the Hertz impact theory. The sub-impact phenomenon was observed by the tests and simulations. By comparing the results of test, simulation and theoretical analysis, it is found that the first sub-impact process is dominated by local impact-contact deformation and can be described by the Hertz impact theory. The subsequence sub-impacts have much different characteristics from the first sub-impact, and their impact durations vary random in large ranges. The further investigation has found that the processes of the subsequence sub-impacts are dominated together by the local impact-contact deformation and the beam vibrations, and the impact force responses become complicated because of the beam vibrations. The numerical simulations show that the first vibration mode of the beam decreases its amplitude suddenly and changes its phase angle obviously when sub-impacts taken place. The numerical simulations also show that the sub-impact conditions relate to the ratio of the round-nosed mass to the beam equivalent mass, initial impact velocity, impact position, initial impact momentum, length and thickness of test beam. It is found that the sub-impact conditions can be represented by a mass ratio threshold. The present investigation illustrates that the couple mechanical effect of local impact deformation and structural vibration make a plenty of sub-impact behavior. It is necessary to further investigate the phenomenon of sub-impact by test, numerical simulation and theoretical analysis, so as to have a comprehensive understand of impact behavior of flexible systems.
2014, Vol. 35 
