Modal Testing for Add-on Damping System Evaluations- a Poor Man’s Approach

This paper will describe how experimental modal testing can be used for designing and determining the effectiveness of add-on damping systems for small structures or substructures. These add-on damping systems, also known as surface damping treatments. have been in use for over 30 years as a means of reducing the response of a structure subjected to vibratory loads. By adding damping to the structure, the reduction of vibratory response has prevented ultimate failure, increased fatigue life, and/or reduced structural-borne noise. In many cases through the years, the integration of an add-on damping system to a structure has involved both analytical and experimental processes; in particular, for complex structures and situations requir ing an optimum design for a damping treatment due to the need to reduce cost, weight, etc. However there are times when the response of a small structure or substructure needs to be reduced and this can be done with the use of add-on damping treatment designed with only experimental modal data. For this paper, two examples will show how impact modal tests verified the effectiveness of add-on damping systems for small payloads developed by the Marshall Space Flight Center. The dynamic response of both payloads was significantly reduced by the damping systems. Particular emphasis will show that materials for add-on damping systems are readily available and that small channel count impact modal testing can be quickly used for applying add-on damping systems to these structures.