A physically-based simulation method for the bearing ring creeping failure mode for 2TRB rotor main bearings exceeding the current state-of-the-art
Dr.-Ing. Daniel Billenstein
Summary
The increasing power rating of multi-megawatt wind turbines and the simultaneous growing size of rotor main bearings pose challenges to ensure long-term reliability of the entire powertrain. One critical key issue for non-bolted 2TRB bearing applications is the so called "bearing ring creeping", whereby a bearing ring incrementally rotates relative to its adjacent component during operation. This failure mode can lead in the very first stage to fretting corrosion and/or abrasive wear between the clamped bearing ring and the shaft or housing. At a later stage, the functionality of the powertrain and here in particular the structural integrity of the bearing ring and/or the companion structure like the shaft is at high risk.
The validated, advanced numerical simulation method for the creeping analysis covers both underlying damage mechanisms: roller- and structural-induced creeping. Based on this physical simulation setup, the simultaneous presence and complex interaction of both creeping mechanisms is investigated in detail revealing their mutual influences on the creeping behavior. Unlike other calculation approaches, this simulation method requires no calibration against empirical data making it a robust and generally applicable tool independent form the bearing ring size and loading. The successful validation against independent experimental data confirms its predictive accuracy and its quantifiable output using a novel Creeping Scale metric. This scale enables detailed assessment of creeping intensity and safety buffer, allowing designers to evaluate and especially prioritize countermeasures quantitatively, which is showcased in this paper.
Future outlooks highlight recommendations for a failure-mode specific load preparation and component strength assessment ultimately leading to design principles of higher creeping-resistance that ensure structural drivetrain integrity under operational conditions to enhance the long-term reliability of modern wind turbines.