A complete structural vibration source model for a class of rotating machines with internal force generating mechanisms

An experimental methodology for modeling the vibration source characteristics of a class of dynamically complex machines has been developed. The dynamic behavior of the machine, including internal forcing and structural dynamic response, is modeled with a compact representation.; Previous studies have shown that a vibration source can be represented by two parameters measured at the interface points of the source: the source mobility, and the free velocity or blocked force. These source descriptors have not been previously consolidated into a concise form which constitutes a complete dynamic model. In addition, practical methods have not been previously developed for the inclusion of rotational coordinates in both the source free velocity and mobility measurements.; The source descriptor that has been developed uses rigid body degrees of freedom to represent the vibration of an elastic source. The modeling methodology inherently includes rotational coordinates in the free velocity and the source mobility. So-called rigid body free vibration vectors, and free interface extended rigid body modes, aid in understanding the internal forcing patterns and the dynamic response characteristics of the source. Effective force and vibrational power descriptors are defined from the rigid body free vibration and the effective free interface rigid body dynamic response. The developed modeling methodology is shown to be accurate, subject to one primary condition that must be satisfied over the frequency range of interest. While the machine operates in an effectively isolated state, the motion of the interface points must be able to be accurately described by the motion of a single rigid body. A vector norm rigidity index has been developed to quantify the accuracy of the rigid body assumption.; The modeling methodology is demonstrated analytically with a planar, multi-body system. The effects of various modeling errors are demonstrated using the analytical model. The modeling methodology is fully demonstrated on a dynamically complex rotating machine. The source descriptor model is developed for the machine and coupled to an FEA model of a mounting bracket. The model of the coupled system is shown to accurately predict the measured vibration of the actual system.