<p>Previous work has shown how inverse methods, a lumped mass model and shaft torque measurements of the propulsion system of the S.A. Agulhas II can be used to calculate ice induced torque loads. Validation exercises has identified that parameters of the lumped mass model should be optimized so that the predicted time series of the ice induced torque is independent of the measurement location. This paper presents methods in which the stiffness, damping and inertia of the lumped mass model is optimised to decrease the uncertainty of calculated loads. Ansys Twin Builder is used to optimise the parameters and Matlab is used to solve the inverse load estimation. Two methods are utilised to optimise the parameters. The first method optimises the parameters so that the error is minimized between first two natural frequencies of the model and the operational measured natural frequencies. The second method minimizes the error between two time signals. The decrease in load uncertainty is shown as stochastic distributions of the errors. It is shown that both methods provide greater load certainty with the second method proving to be the most effective method of optimising the parameters for this application. The use of this tuned model in a digital twin is discussed briefly.</p>

ON UNCERTAINTY ASSESSMENT OF FATIGUE DAMAGE OF PROPULSION SHAFT UNDER ICE IMPACT

Paper Proceedings: https://asmedigitalcollection.asme.org/OMAE/OMAE2021/volume/85116

OMAE 2021

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