ABSTRACT
Vibrations of real mechanical systems (machines and mechanisms, buildings, structures, ships and so forth) produced by different dynamic effects are always accompanied by some thermal losses and dissipation of energy stored in the system to the surrounding medium. If the system has finite dimensions, the internal friction that transforms mechanical energy into thermal determines the dissipation of the energy vibrations, with the exception of those due to resistance of the surrounding medium and constraints imposed on the system. The complexity and variety of internal physical processes associated with internal friction notwithstanding, the latter is outwardly characterised by a few output parameters, whose dependence on material properties and loading conditions can be experimentally studied. In amorphous or quasi-crystalline homogeneous materials, internal friction is caused by complex thermodynamic processes, such as magnetic and thermal diffusion, electron emission etcetera. Maximum attention has been devoted to the theory of frequency- independent internal friction.
