抄録
Impact vibrations of cantilever beam that has very narrow clearance between a beam and an impact wall, and that is excited around 2nd natural frequency, was investigated from the point of view of the sub-harmonic vibration of 1st mode. The followings are made clear. (1) A widely spread attractor with the bending type impact vibration, i.e. the beam bend like a clamped - simply supported beam while the beam is almost contact with the wall, is caused by a nonlinearity that the system is piecewise linear. (2) It is suggested that an essential mechanism of the bending type impact vibration is explained by a model using relatively a few modes. It is also made clear that even if a system is piecewise linear, i.e. the system is consisted of several linear systems, and each systems has linear modes, an analytical model using linear modes for each systems have inappropriate restrictions caused by characteristics of linear modes at connections of each linear systems.
