The problem to be dealt with in the present work is the forced
vibration problem of the mechanical system shown in Fig. 1a. It
consists of a cantilevered Bernoulli–Euler beam with a tip mass M
to which an axially vibrating visco-elastic rod with tip mass M is
attached in span. The axially vibrating visco-elastic rod with tip
mass corresponds to a conventional helical spring-mass system,
where the spring is subjected to internal damping. It is assumed
that the features of the visco-elastic rod fit the Kelvin–Voigt model
and further, that the combined system vibrates only in the plane of
the paper.