THE USE OF AN ECTOPLASM TO PREDICT FREE-VIBRATIONS OF PLATES WITH CUTOUTS

A formulation using the new concept of ''Ectoplasm'' that allows predi ction of high order eigenfrequencies and mode shapes of a simply suppo rted plate with cut-outs of any shape is presented. Hamilton's princip le is used with a functional basis that does not depend on the shape o f the cut-outs (boundary conditions for stresses around the holes do n ot matter). Such a basis allows easy computation but leads to a non-un ique problem with ill-conditioned mass and stiffness matrices. The use of ''Ectoplasm'' overcomes these problems without increasing numerica l calculation. Extreme examples of holes can be treated and high order modes can be calculated. The convergence of the method is studied and criteria are given to enable its use with a good accuracy. The method is validated by comparison with a finite element approach and previou sly published results. (C) 1996 Academic Press Limited