SHAPE OPTIMIZATION OF UNCONSTRAINED VISCOELASTIC LAYERS USING CONTINUUM FINITE-ELEMENTS

Of the many methods available for achieving effective vibration dampin g, adding viscoelastic lamina is a significant technique for vibration reduction. Recently, the desire to apportion this material in a way t hat will take the greatest advantage of its dissipative characteristic s has led to studies in optimization. Optimal design for viscoelastica lly damped laminated beams and plates undergoing harmonic excitation h as been examined in the literature? both for constrained and unconstra ined damping layers. However, to the authors' knowledge, previous opti mization studies have not used continuum based finite elements to mode l the structure, as is done here. The problem examined is the shape op timization of an unconstrained damping layer on an elastic structure, assuming a constant volume of damping material as a design constraint. The objective is to minimize the peak displacement. Several boundary conditions are examined for beam and plate type structures. The peak d isplacement and the loss factor of the optimized structure are compare d with the uniform layer structure. Also, results obtained using reali stic (frequency dependent) and constant viscoelastic material data are compared. The structures are modelled using continuum based elements in the ABAQUS Finite Element Code. The optimization code uses a Sequen tial Quadratic Programming algorithm. For most of the structures exami ned, order of magnitude improvement is seen as a result of optimizing the shape of the damping layer. Peak displacements are reduced by up t o 98%. These results are quite robust, with the optimized damping laye r achieving significantly better damping performance for a wide variet y of cases examined. (C) 1998 Academic Press.