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Author: Johan Luyckx Publisher: ISBN: Category : Ball-bearings Languages : en Pages : 25
Book Description
Some roller bearing applications are prone to the white etching crack (WEC) failure mode. The applications seem to have in common that they work under dynamic operating conditions. The specific feature of this failure mode is that the subsurface microstructure of a failed bearing contains modified material structures near cracks which are white after a nital etching test. In case of a WEC failure, the real lifetime of the bearing is much lower than the theoretical lifetime calculation. The hypotheses of fatigue overload, hydrogen, and accumulated plastic microstrain are evaluated and a root cause hypothesis is developed based on observations. The white etching material structures are interpreted as adiabatic shear bands generated by an impact load mechanism. We developed the root cause hypothesis that the dynamic operation of a roller bearing is generating a bearing internal pressure peak causing loads at high strain rate which result in material damage and initiate the WEC failure mode. Impact tests reveal a high sensitivity of through hardened martensitic and bainitic bearing steels for the adiabatic shear band failure mode. The origin of the bearing internal pressure peak is further explained based on available ElastoHydrodynamic Lubrication (EHL) experimental and simulation results. The generation of butterflies and WEC networks is interpreted as recrystallisation driven by high stress after many load cycles or a moderate stress combined with a high strain rate loading. The industrial experience is analysed from the perspective of the root cause hypothesis. The Weibull curve of a WEC bearing failure case is explained based on the material parameter full width at half-maximum (FWHM) at the raceway surface. The potential solutions of an optimised microstructure, black oxidized treatment, and hot assembly are identified based on positive industrial experience.
Author: Johan Luyckx Publisher: ISBN: Category : Ball-bearings Languages : en Pages : 25
Book Description
Some roller bearing applications are prone to the white etching crack (WEC) failure mode. The applications seem to have in common that they work under dynamic operating conditions. The specific feature of this failure mode is that the subsurface microstructure of a failed bearing contains modified material structures near cracks which are white after a nital etching test. In case of a WEC failure, the real lifetime of the bearing is much lower than the theoretical lifetime calculation. The hypotheses of fatigue overload, hydrogen, and accumulated plastic microstrain are evaluated and a root cause hypothesis is developed based on observations. The white etching material structures are interpreted as adiabatic shear bands generated by an impact load mechanism. We developed the root cause hypothesis that the dynamic operation of a roller bearing is generating a bearing internal pressure peak causing loads at high strain rate which result in material damage and initiate the WEC failure mode. Impact tests reveal a high sensitivity of through hardened martensitic and bainitic bearing steels for the adiabatic shear band failure mode. The origin of the bearing internal pressure peak is further explained based on available ElastoHydrodynamic Lubrication (EHL) experimental and simulation results. The generation of butterflies and WEC networks is interpreted as recrystallisation driven by high stress after many load cycles or a moderate stress combined with a high strain rate loading. The industrial experience is analysed from the perspective of the root cause hypothesis. The Weibull curve of a WEC bearing failure case is explained based on the material parameter full width at half-maximum (FWHM) at the raceway surface. The potential solutions of an optimised microstructure, black oxidized treatment, and hot assembly are identified based on positive industrial experience.
Author: Reinder Hindrik Vegter Publisher: ISBN: Category : Adiabatic shear band (ASB) Languages : en Pages : 23
Book Description
Wind turbine gearboxes are subjected to a wide variety of operating conditions, some of which may push the bearings beyond their limits. Damage may be done to the bearings resulting in a specific premature failure mode known as white etching cracks (WECs), sometimes called irregular, or white structured flaking (WSF). In this paper, some influencing factors that can lead to WEC failure will be discussed and related to existing root cause hypotheses. From this work, it is clear that a generalized simple root cause is counterproductive, pinpointing the need to carefully evaluate each WEC case in the light of the corresponding application.
Author: Gary L. Doll Publisher: Elsevier ISBN: 0128221747 Category : Technology & Engineering Languages : en Pages : 292
Book Description
Rolling Bearing Tribology: Tribology and Failure Modes of Rolling Element Bearings discusses these machine elements that are used to accommodate motion on or about shafts in mechanical systems, with ball bearings, cylindrical roller bearings, spherical roller bearings, and tapered roller bearings reviewed. Each bearing type experiences different kinds of motion and forces with their respective raceway, retainers and guiding flanges. The material in this book identifies the tribology of the major bearing types and how that tribology depends upon materials, surfaces and lubrication. In addition, the book describes the best practices to mitigate common failure modes of rolling element bearings. Discusses important tribological implications surrounding the performance and durability of rolling element bearings Describes how the different types of roller bearings work Explores the reasons behind the failure of roller bearings and presents information on how to mitigate those failures
Author: Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
A WEC is a particularly aggressive, unpredictable and wide spread rolling element bearing failure mode that is common for large multi-megawatt (MW) wind turbines. WEC is considered the single most expensive failure mode for all wind turbine components, and there is currently no commercial solution. The Technical University of Denmark (DTU) is leading the WhiteWind project to investigate WECs through funding provided by the Innovation Fund Denmark. Other project partners include Vestas, SKF, Expanite, Rheinisch-Westfalische Technische Hochschule Aachen University (RWTH Aachen), and Argonne National Laboratory. The objective of the overall project is to develop a new surface engineered WEC-resistant bearing material using novel surface engineering techniques that shall provide a commercially competitive alternative to existing wind turbine bearings. NREL will support the project by providing existing measured bearing loads and validating models of drivetrain loads.
Author: Lester E. Alban Publisher: ASM International ISBN: 9781615031771 Category : Technology & Engineering Languages : en Pages : 252
Book Description
Explores the detailed steps necessary to determine the causes of failure. First, the physical characteristics of a gear are studied: where the stress points are, from what directions the forces are applied, where the movement of material progresses, and where strain patterns exist. Second, all external conditions and forces are considered. With this background information, a systematic examination is described from beginning to end, the end being a conclusion about the mode and cause of failure.
Author: Publisher: ISBN: Category : Languages : en Pages : 14
Book Description
White etching cracks (WECs) have been identified as a dominant mode of premature failure within wind turbine gearbox bearings. Though WECs have been reported in the field for over a decade, the conditions leading to WECs, and the process by which this failure culminates, are both highly debated. In previously published work, the generation of WECs on a benchtop scale was linked to sliding at the surface of the test sample, it was also postulated that the generation of WECs was dependent on the cumulative energy that had been applied to the sample over the entirety of the test. In this paper, a three ring on roller bench top test rig is used to systematically alter the cumulative energy that a sample experiences through changes in normal load, sliding, and run time, in an attempt to correlate cumulative energy with the formation of WECs. It was determined that, in the current test setup, the presence of WECs can be predicted by this energy criterion. The authors then used this information to study the process by which WECs initiate. Lastly, it was found that, under the current testing conditions, the formation of a dark etching microstructure precedes the formation of a crack, and a crack precedes the formation of white etching microstructure.
Book Description
Despite constant expansion and engineering progress, wind turbines still present unexpected failures of heavy duty mechanical components drastically affecting the cost of energy. Among the most prevalent tribological failures in wind turbine rolling element bearings, a peculiar rolling contact fatigue mode has been associated to broad subsurface three-dimensional branching crack networks bordered by white etching microstructure, and thus named White Etching Cracks (WEC). Compared to conventional microstructural alterations, WECs tend to develop at moderate loads and cycles eventually leading to premature failures that remain unpredictable using fatigue life estimations. Far from being generic to specific manufacturers, WECs occur in various industrial applications, for various bearing types, components, lubricants, steels grades and heat treatments. As WEC occurrences present no common evident denominator, they remain delicate to reproduce on laboratory test rigs without prior artificial hydrogen charging, so that no consensus on WEC formation mechanisms have been confirmed yet. In this study, a thorough tribological analysis of WEC formation mechanisms has been led. Expertise protocols have been established to best reveal and observe WECs that commonly develop at unconventional locations versus the contact area. First analysis of WEC reproductions on standard rolling element bearings either hydrogen precharged or kept neutral have signified that artificial hydrogen charging, commonly employed to apprehend the failure mode, results in similar WEC morphologies but tends to alter WEC tribological initiation. In consequence, WEC reproductions in remarkably different configurations but without hydrogen charging have been compared in order to propose a better understanding of WEC surface-affected formation mechanisms: first, initiation via tribochemical hydrogen permeation at nascent steel surfaces formed either directly at the raceway or at surface microcracks flanks and second, propagation by local hydrogen embrittlement at crack tips function of the stress state. An extensive root cause analysis have then been led suggesting that WEC may be associated to various combinations of macroscopic operating conditions that often interact and come down to similar tribological parameters including high sliding energy thresholds, specific lubricant formulations and tribochemical drivers such as water contamination and/or electrical potentials. Further investigations on a minimalist twin-disc fatigue tribometer have provided additional evidence that WEC influent drivers are non-self-sufficient, supporting that WEC formation mechanisms rely on a subtle equilibrium between tribo-material, tribo-mechanical and tribo-chemical drivers that all should be mastered to design efficient and durable countermeasures.
Author: IEEE Staff Publisher: ISBN: 9781728192987 Category : Languages : en Pages :
Book Description
SDEMPED aims to provide a high level international forum for researchers, professionals, professors, PhD students and in general for specialists in diagnostics and monitoring of electrical systems, including machines, power electronics, adjustable speed drives, fuel cells and electrolysers, dielectric materials, signal processing methods, and related areas
Author: Johan Luyckx
Author: Johan Luyckx
Author: Reinder Hindrik Vegter
Author: John M. Beswick
Author: Gary L. Doll
Author: 
Author: Lester E. Alban
Author: 
Author: Lauralice de Campos Franceschini Canale
Author: Arnaud Ruellan Du Créhu
Author: IEEE Staff