Noise and Vibration Measurement Methods for Large Diameter Single-Piece Aluminum Propeller Shafts

This paper describes recently developed test methods and instrumentation to address the specific noise and vibration measurement challenges posed by large-diameter single-piece tubular aluminum propeller (prop) shafts with high modal density. The prop shaft application described in this paper is a light duty truck, although the methods described are applicable to any rotating shaft with similar dynamic properties. To provide a practical example of the newly developed methods and instrumentation, impact FRF data were acquired in-situ for two typical prop shafts of significantly different diameter, in both rotating and stationary conditions. The example data exhibit features that are uniquely characteristic of large diameter single-piece tubular shafts with high modal density, including the particular effect of shaft rotation on the measurements. Observed differences in the data between the static and rotating operating conditions are examined, and observed frequency shifts are explained by coordinate transformation from the stationary sensor locations to the rotating shaft. Empirically-adjusted frequency shift equations are then provided and compared to the measured data. As a final note, the suitability of the experimental and theoretically predicted data for CAE model correlation is discussed.