Abstract
Wind energy is currently one of the most promising and the fastest-growing installed alternative-energy production technologies. It is anticipated that by 2030, at least 20% of the US energy needs will be provided by this form of energy. The economics of wind energy require that wind turbines (convertors of wind energy into electrical energy) be able to operate for at least 20 years, with only regular maintenance. Unfortunately, many wind turbines require major repairs after only 3–5 years in service, mainly due to the failure of their gear boxes. It is this lack of gear box reliability which is currently compromising wind energy economics. In the present work, a multiphysics computational methodology has been developed and used to analyze the problem of white-etch cracking, one of the key processes responsible for the premature failure of gearbox roller bearings. The multiphysics methodology includes: (a) quantum-mechanical calculations of the hydrogen dissolution and the accompanying grain boundary embrittlement phenomena; (b) atomistic-level kinetic Monte Carlo analysis of hydrogen diffusion from the crack wake into the adjacent unfractured material; (c) cohesive zone type modeling of the intergranular fracture processes; and (d) a conventional displacement-based finite element analysis of the kinematic and structural response of the bearing under service loading conditions. The results obtained clearly revealed the operation of the white-etch cracking phenomena and their possible interaction with the conventional rolling-contact fatigue damage processes.
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