ABSTRACT
The shortcomings of the Voight model are associated with the strong frequency dependence of internal friction described by it. They are the source of obvious disparity between the results obtained by the Voight model and the real physical phenomena occurring during vibrations of rigid bodies. The first attempts at developing an internal friction model, generalising the method of quasi-normal co-ordinates, were made by Caughey, Dadeppo and Rasskazovskii. Tseitlin and Guseva presented a rigorous derivation of complex stiffness for systems with frequency-independent absolute and relative losses. In these systems neither the phase nor the amplitude characteristic of the visco-elastic element depend on frequency. In other words, the real as well as the imaginary parts of complex stiffness are frequency-independent. It is important to emphasise the significance of multiplier sign in the imaginary part of complex stiffness.
