Dynamics and Fatigue Analysis of Planetary Gear Trains under Random Loading

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Planetary Gear Trains (PGTs) are widely used in industry and many other applications. In some of the applications, the loads to which the PGTs are subjected are random/stochastic. Two representative scenarios where PGTs are used as a transmission unit, and subjected to random loads include wind turbines in wind energy industry and directional drilling in oil and gas industry. Fatigue caused by the vibration in these systems is a outstanding issue in the industries, and has huge economical consequence. However, the random nature of the vibration stresses largely hinders accurate fatigue prediction and proper fatigue management. The proposed research intends to systematically investigate the dynamics of PGTs under random loads, and develop effective fatigue prediction methods. Based on the two cases above, the internal excitations which are common to all PGTs and the external excitations which vary for different applications will be modeled as random processes. Experiments will be carried out to characterize the external excitation in drilling for which little is known at present. Then the statistics of the responses, including displacement, velocity, stresses and strains, could be solved for with numerical and analytic methods. These statistic information constitutes the basis for further fatigue prediction. It is expected that, through this proposed research, the reliability and fatigue life of PGTs in both wind turbines and drilling could be improved. The long term goal is to develop a theoretical framework for random dynamics of PGTs in general random context; thus, the method and algorithms can be applied to and benefit broader applications, such as applications in off-shore engineering and land vehicles.