ON THE EVALUATION OF COUPLING EFFECT IN NONCLASSICALLY DAMPED LINEAR-SYSTEMS

The normal coordinates of a nonclassically damped systems are coupled by nonzero off-diagonal elements of the modal damping matrix. In analy zing a nonclassically damped system, one common approximation is to ne glect those damping terms which are nonclassical, and retain the class ical ones. The sufficient conditions justifying the neglect of the off -diagonal terms are that the damping matrix be diagonally dominant and the minimum frequency separation be sufficiently large. But the probl em is that the amount of sufficiently small and sufficiently large is not well defined, thus decoupling approximation technique can hardly b e applied to the real problems. The purpose of this paper is to provid e the method for evaluating the coupling effect of nonclassically damp ed systems. This method does not require matrix inversion nor exact so lution but simply provide a convenient way to determine the feasibilit y of neglecting off-diagonal elements of the modal damping matrix.