The paper is concerned with the dissipative behavior due to multi-freq
uency excitation. It is shown both theoretically and experimentally th
at it is possible to treat the frequencies separately. Practically, th
is leads for instance to the conclusion that the material damping in a
rotor with anisotropic bearings can be treated as a complex stiffness
, which simplifies the calculations dramatically. (C) 1997 Academic Pr
ess Limited.