The optimum use of unconstrained layer damping treatments.

TLDR: In this paper, the effect of concentrating the treatment in the regions of highest bending moment in order to use all the material more effectively was investigated, and three methods of analysis were presented, two of them being approximate but relatively rapid in use.

Abstract: : Since unconstrained layer damping treatments on vibrating plates dissipate energy by undergoing bending strain, the treatment in the vicinity of lines of contra-flexure contributes little to the total damping. This report investigated the effect of concentrating the treatment in the regions of highest bending moment in order to use all the material more effectively. Three methods of analysis were presented, two of them being approximate but relatively rapid in use. The third has been used in extensive digital computer calculations to determine the effectiveness of given quantities of treatment, having given stiffness, when distributed over different proportions of the length of a vibrating, simply supported strip. The effectiveness has been assessed using certain criteria which apply to different problems, e.g. to the problems of reducing harmonic resonant vibration amplitudes, or inertia forces exerted by randomly vibrating panels, etc. Different criteria relate to each problem. It has been shown that very considerable increases of effectiveness are obtained by concentrating the treatment over a proportion of the length or area. For a given quantity and stiffness of treatment, the effectiveness may be maximised by covering certain optimum proportions.