Calibration of critical speed predictions using experimental measurements

Abstract

Experimental characterization of structures provides information about the real dynamic behavior of machineries. This results in a better estimation of dynamic stress levels, used to predict lifespan, reliability and optimal operating ranges. Experimental results can also be used to improve and calibrate simulations and calculations. In particular, calculation of shaft bending frequencies is needed to define the critical rotation speed. However, natural frequency computation requires a prior knowledge on many subcomponent properties, that are not precisely known in practice. This leads to a great uncertainty on the predicted critical speed. The purpose of this study is to use experimental in-situ measurements as a means to reduce uncertainties on physical properties of the shaft line and increase confidence in the prediction of natural frequencies and critical speed. This involves ambient modal analysis, calibration techniques and statistical approaches to gain insight on the true shaft physical properties.