Correlating Spectral Measurements

In a recent paper (Richardson-6), we introduced a new metric for comparing two operating .deflection shapes called the Shape Difference Indicator (SDI). In another previous paper (Richardson et al. (2017) Using modal parameters for structural health monitoring, In: IMAC XXXV, January 30-February 2), we used SDI to measure the difference in modal frequencies resulting from a joint stiffness change in a mechanical structure. In this paper we use SDI in two new ways. In the first application, SDI is used to ensure that a repeatable impact is applied to a structure during a Roving Response ODS or Modal test. In the second application, SDI is used to measure the difference between currently acquired and Baseline Auto spectrum measurements over prescribed frequency band. We have implemented SDI together with a search method for ranking currently acquired and archived data based upon their numerical differences. We call this new method Fault Correlation Tools (FaCTs (TM)). FaCTs (TM) is useful in multiple applications, including route-based machine condition monitoring, structural health monitoring, production qualification testing, machinery recertification following scheduled maintenance, and noise & vibration monitoring in public places such as building construction sites to comply with local ordinances.