Acoustic emissions in broadband vibration as an indicator of bearing stress

Wideband vibration measurements from seeded fault testing conducted at Pratt and Whitney have been examined to determine the practicality of using such measurements to monitor bearing stress. The measurements were taken using a robust laser interferometer (RLI) in support of technology investigations conducted for prognostic health monitoring (PHM) for the Joint Strike Fighter (JSF) Program. Data from Bearing 1 was examined, where the changes in bearing stress resulted from: changes in operational speed; seeded physical faults and changes in lubrication availability and quality. The RLI measurements were made by measuring the bearing vibrations that were transmitted from the outer race (and its housing) through, or along, the scavenge oil pipe to the outer surface of the engine. Bearing stress and the general health of the 1 bearing were examined from a variety of viewpoints, including the observation of the existence of and character of time series shock pulses, the measurement of enveloped detection bearing fault frequencies, and changes in the amplitude and character of spectrums. While remaining work is required for both RLI system refinement and the development of appropriate analytical tools, it has been demonstrated that acoustic emissions in broadband vibrations should be expected to provide a viable indication of bearing stress.