The actual service life of wind turbine gearboxes is often well below the desired 20 years. One of the prevalent failure modes in gearbox bearing raceways is white structure flaking (WSF) in as little as 6–24 months of operation by the formation of axial cracks and white etching cracks (WECs) with associated microstructural change called white etching areas (WEAs). Despite these failures having been observed for two decades in various industries, the drivers and mechanisms for their formation are still highly contested. Discussed in this review are methods for searching and analysing WECs, mechanisms for WEA microstructural change, WEC initiation and propagation theories, WSF formation drivers and finally technologies and processes offering resistance to WSF. This updated review serves as a recap, comprehensive update on findings, current focus areas and remaining challenges.This paper is part of a Themed Issue on Recent developments in bearing steels.

An updated review: white etching cracks (WECs) and axial cracks in wind turbine gearbox bearings

Definitions and basic properties of the Voronoi diagram generalizations of the Voronoi diagram algorithms for computing Voronoi diagrams poisson Voronoi diagrams spatial interpolation models of spatial processes point pattern analysis locational optimization through Voronoi diagrams.

Spatial tessellations. Concepts and Applications of Voronoi diagrams

Defects as a root cause of fatigue failure of metallic components. III: Cavities, dents, corrosion pits, scratches

Defects as a root cause of fatigue failure of metallic components. II: Non-metallic inclusions

Effect of retained austenite – Compressive residual stresses on rolling contact fatigue life of carburized AISI 8620 steel

Effect of non-metallic inclusions on butterfly wing initiation, crack formation, and spall geometry in bearing steels

Experimental and Numerical Investigation of Torsion Fatigue of Bearing Steel

A Damage Mechanics Approach to Simulate Butterfly Wing Formation Around Nonmetallic Inclusions

Microstructural alterations in bearing steels during rolling contact cycling have been reported in the literature for more than 60 years. These changes appear in different shapes and locations. One class of such alterations is “butterfly wings”: regions of microstructurally transitioned material that appear diagonally around nonmetallic inclusions and may serve as fatigue crack initiation sites. Over the course of the past half a century numerous experimental and multiple analytical efforts have been made to understand and model this phenomenon, yet a lot is to be discovered and understood about root causes and mechanisms leading to butterfly formation. This article presents a comprehensive overview of the crack nucleation phenomena due to butterfly formation, its characteristics, and its negative impact on bearing service life. Significant attempts that have been made to solve the problem over the past half a century are mentioned, with a focus on recent work. Unanswered dilemmas are particularly...

Sina Mobasher Moghaddam

Papers

Effect of non-metallic inclusions on butterfly wing initiation, crack formation, and spall geometry in bearing steels

Experimental and Numerical Investigation of Torsion Fatigue of Bearing Steel

A Damage Mechanics Approach to Simulate Butterfly Wing Formation Around Nonmetallic Inclusions

A Review of Microstructural Alterations around Nonmetallic Inclusions in Bearing Steel during Rolling Contact Fatigue

A 3D numerical and experimental investigation of microstructural alterations around non-metallic inclusions in bearing steel