MODAL-ANALYSIS OF PLATES USING THE DUAL RECIPROCITY BOUNDARY-ELEMENT METHOD

This paper presents a new method for determining the natural frequenci es and mode shapes for the free vibration of thin elastic plates using the boundary element and dual reciprocity methods. The solution to th e plate's equation of motion is assumed to be of separable form. The p roblem is further simplified by using the fundamental solution of an i nfinite plate in the reciprocity theorem. Except for the inertia term, all domain integrals are transformed into boundary integrals using th e reciprocity theorem. However, the inertia domain integral is evaluat ed in terms of the boundary nodes by using the dual reciprocity method . In this method, a set of interior points is selected and the deflect ion at these points is assumed to be a series of approximating functio ns. The reciprocity theorem is applied to reduce the domain integrals to a boundary integral. To evaluate the boundary integrals, the displa cements and rotations are assumed to vary linearly along the boundary. The boundary integrals are discretized and evaluated numerically. The resulting matrix equations are significantly smaller than the finite element formulation for an equivalent problem. Mode shapes for the fre e vibration of circular and rectangular plates are obtained and compar ed with analytical and finite element results.