Using Series-Series Iwan-Type Models for Understanding Joint Dynamics

Abstract

In many structures of great engineering importance, such as air frames or jet engines, the primary source of vibration damping is often just the frictional damping of interfaces associated with mechanical joints. This damping is associated with slip in outer regions of the contact patches and is known to be strongly amplitude dependent (and hence nonlinear) (1-2). These mechanisms have traditionally been accommodated in structural dynamics only indirectly. For instance, one may use a finite element code to deduce modes and frequencies but then wait for data taken from a prototype tested at amplitudes of interest to obtain nominal values for modal damping coefficients.