Optimum Layout of Passive Constrained Layer Damping Treatment Using Genetic Algorithms

Abstract

The passive constrained layer damping (CLD) treatments have been used widely for vibration suppression of various flexible structures. Fully covered CLD treatment is extensively used to depress the vibration over a wide frequency range in engineering applications. In most of these treatments it is required that the CLD treatment should not significantly increase the weight or volume. This paper focuses on damping optimization of fully coating beam with a constrained viscoelastic layer. The governing equation of motion of a CLD covered beam is derived using an energy approach and Lagrange’s method. The assumed modes method is employed in solving the equation to obtain the modal loss factors which are used as the objective of optimal layout. A genetic algorithm with large-scale mutation method is employed to search for the optima of the thicknesses of both the constraining layer (CL) and the viscoelastic layer (VL) and the shear modulus of the viscoelastic material (VEM) with the restriction of added volume of the total CLD treatment. Numerical results show that the optima of three design variables, the thicknesses of the CL and the VL and the shear modulus of its viscoelastic material, are highly relevant to each other. The softer or thinner constraining layer requires a softer viscoelastic material for an optimal damping treatment, and high value of the elastic modulus of the base beam matches high shear modulus of the viscoelastic material. The variation of the CL thickness decreases slowly and that of the VL thickness increases with the increase of the thickness of the CLD treatment. Stiffer constraining layer assure greater modal loss factors.