Experimental studying multi-impact phenomena exhibited during the collision of a sphere onto a steel beam

Abstract

The impact of sphere against the beam is one of the basic impact problems in flexible mechanical dynamics. A flexible steel beam supported at the two ends struck by a steel sphere was tested in this article. Multiple sub-impacts were observed during the falling impact process of the steel sphere. The test contact–impact durations of the sub-impacts were compared with that of the theoretic results derived from the Hertz contact law. It is confirmed that the Hertz contact law is still suitable to estimate the impact–contact duration of the first sub-impact. The difference between the test impact–contact durations of the subsequent sub-impacts and that of the theoretic results was explained theoretically by a revised impact theory in consideration of beam’s vibration. The occurrence reason of the sub-impact was systematically discussed. It is concluded in this investigation that the sub-impacts are dominated by local contact–impact deformation, but influenced obviously by the global vibration of the flexible structure. When the sub-impacts occur, the coefficient of restitution shows strong uncertainty.