Publications

The complex mode indicator function for identifying unit to unit variability

Brink, Adam R.; Rohe, D.; Mayes, R.; Freymiller, J.E.

We propose the use of the Primary Complex Mode Indicator Function (PCMIF), calculated from acceleration frequency response functions, as a response comparison metric to analyze unit-to-unit variability. The PCMIF has an advantage over the traditional dynamic representations of mode shapes, frequencies and damping in that it removes the user and algorithmic error that may be associated with those extractions. In addition, it is customizable according to the interest level. If consistent sets of acceleration measurements from chosen drive points can be acquired from multiple hardware units, the comparison of each unit's PCMIF metric can provide insight. In addition to measured PCMIF, finite element models of the system can predict variability in PCMIF response using known variability of hardware configurations, and this can be compared with experimental PCMIF data. This comparison allows meaningful unit-to-unit comparison even if components and/or system geometries differ from one system to the next.