CHAPTER 9 - EVALUATING THE DAMPING LOSS FACTOR

Abstract

This chapter discusses the experimental, analytical, and empirical methods for evaluating the modal damping loss factor η in a variety of statistical energy analysis (SEA) subsystem types. The damping loss factor is an important parameter in all types of dynamical analyses, including SEA. For many subsystems, the overall response level is inversely proportional to the damping level. In many cases, experiments are the only available approach because of the lack of analytical or empirical information about the damping of a particular subsystem configuration. There are some analytical methods and empirical data available for some common, simple subsystem configurations. The two most common methods for experimentally determining the damping loss factor of a subsystem are the decay rate and the half-power bandwidth methods. Damping mechanisms are often complicated and nonlinear, and most damping models and measurements are approximate with an accuracy no better than about 20%.