Characterizing mechanical system integrity using structural surface intensity

Abstract

Many structural intensity measurements have been made on simple beam and plate-like structures to determine source strengths and transmission paths. When analyzing more complex structures it is often difficult to compute the intensity throughout the depth of an element. Using a method developed by Pavic [G. Pavic, J. Sound Vib. 115, 405–422 (1987)], the structural surface intensity (SSI) is computed on a gearbox housing using an array of accelerometers and strain gauges. The focus of this research is to use SSI as a machinery fault indicator, with the objective of developing a method that is more sensitive than other conventional diagnostic methods. Experimental data were taken on a gearbox from the Mechanical Diagnostic Test Bed (MDTB) at the Penn State Applied Research Laboratory as the gearbox was run to failure. The changes in energy flow are analyzed and characterized to provide criteria for fault detection. Analysis of the data indicates that significant changes in structural surface intensity occur as geartooth faults develop and that SSI can be more sensitive than other traditional indicators. [This research was supported by the Multidisciplinary University Research Initiative for Integrated Predictive Diagnostics (Grant No. N00014-95-1-0461) sponsored by the Office of Naval Research.]