A class of strongly non-linear vibrating systems composed of linear elastic
structures under absolutely rigid constraints condition is considered. Imp
act mode exact solutions an expressed through a saw-tooth time argument and
, as a result, represented in a closed unit form. Based on this special rep
resentation, sufficient conditions of existence and also non-existence for
the impact modes are formulated and interpreted on the spectral axes. In pa
rticular, it was shown that impact modes exist when their basic frequencies
are shifted into the right small neighborhood of any natural frequency of
the linearized (no barriers) system. The frequencies of the localized impac
t mode solutions are located at the right of the linear spectrum and have n
o upper boundary. (C) 2001 Elsevier Science Ltd. All rights reserved.