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Investigations into the accuracy of the light damping approximation

This presentation surveys a variety of representative case studies in an effort to better understand and predict the accuracy of the light damping approximation. For viscously damped systems, the light damping approximation ignores the off-diagonal elements of the transformed damping matrix. When the approximation is valid, it presents profound advantages for numerical simulations. The most obvious of these is uncoupling of the equations of motion. A less obvious advantage is the ability to estimate the viscous damping matrix from a knowledge of the modal loss factors and undamped eigenvectors. The presentation begins by defining error metrics for quantifying the accuracy of the approximation in time and frequency domains. Next, case studies are designed to understand how statistical properties of the structure control the accuracy of the approximation. These investigations make two fundamental contributions. The first contribution is the knowledge required to estimate the accuracy of the approximation without significant computational expense. The second contribution is identification of statistical properties that are important to the construction of model libraries used in training machine learning algorithms.