Investigation of subsurface microcracks causing premature failure in wind turbine gearbox bearings

Abstract

One of the reasons behind the low rate of expansion of power production driven by wind turbines is the premature failure of their gearbox bearings, which fail within the first quarter of their designed life. The leading causes of fatigue damage in wind turbine gearbox bearings (WTGBs) are not well recognized despite the massive studies in this field. The damage initiates as subsurface microcracks, propagating to a macro scale and reaching the contact surface. For that, studying the microcracks in the early initiation stage (1–15 μm) significantly impacts the bearing damage trigger. This study is based on evaluating the role of non-metallic inclusions and voids on crack initiation, revealing the varying parts of (maximum shear stress, Von-Mises stress, and traction force) in crack initiation. The results indicated that the effect of inclusion is relatively limited on cracking initiation regardless of their sizes, other than voids, which probably have a considerable role in crack initiation and propagation. The three factors (Von-Mises stress, maximum shear stress, and traction force) played significant roles in the initiation of cracks. However, there is an urgent need to improve the design and manufacturing of WTGBs to decrease the formation of voids and carbides and revise the design standards for both (bearing life and contact stress) to consider the actual relative effects of the severe operating events.