Elucidating the Mechanisms of White Etching Crack Failures Within Wind Turbine Gearbox Bearings PDF Download
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Author: Benjamin J. Gould Publisher: ISBN: 9781392010020 Category : Languages : en Pages : 224
Book Description
Finally, Chapter 10 investigated the effect that a proposed mitigation technique, namely case-carburization, had on the formation of WECs. It is found that employing case-carburization led to a 2.3x elongation in the time until WEC-induced failure.
Author: Benjamin J. Gould Publisher: ISBN: 9781392010020 Category : Languages : en Pages : 224
Book Description
Finally, Chapter 10 investigated the effect that a proposed mitigation technique, namely case-carburization, had on the formation of WECs. It is found that employing case-carburization led to a 2.3x elongation in the time until WEC-induced failure.
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: 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: Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
The most common failure mode in wind turbine gearboxes is axial cracking in intermediate and high-speed-stage bearings, also commonly called white-etching cracks (WECs). Although these types of cracks have been reported for over a decade, the conditions leading to WECs, the process by which this failure culminates, and the reasons for their apparent prevalence in wind turbine gearboxes are all highly debated. This paper summarizes the state of a multipronged research effort to examine the causes of WECs in wind turbine gearbox bearings. Recent efforts have recreated WECs on a benchtop test rig in highly loaded sliding conditions, wherein it was found that the formation of a dark etching microstructure precedes the formation of a crack, and a crack precedes the formation of white-etching microstructure. A cumulative frictional sliding energy criterion has been postulated to predict the presence of WECs. Bearing loads have also been measured and predicted in steady state and transient drivetrain operations in dynamometer testing. In addition, both loads and sliding at full scale will be measured in planned uptower drivetrain testing. If the cumulative frictional sliding energy is the dominant mechanism that causes WECs, understanding the amount of frictional sliding energy that wind turbine bearings are subjected to in typical operations is the next step in the investigation. If highly loaded sliding conditions are found uptower, similar to the examined benchtop levels, appropriate mitigation solutions can be examined, ranging from new bearing coatings and improved lubricants to changes in gearbox designs and turbine operations.
Author: Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
The most prevalent failure modes in wind turbine drivetrains are main bearing failures stemming from micropitting, white etching or axial cracks in gearbox bearings, and generator bearing failures. These failures are neither well understood nor accounted for in design standards; consequently, the mitigation strategies being developed and fielded may only partially address the physics of failure and can take years to assess. The U.S. Department of Energy continues to support research programs to investigate the influence of rolling element sliding on the formation of bearing axial cracks and main bearing micropitting.
Author: Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Failures in gearbox bearings have been the primary source of reliability issues for wind turbine drivetrains, leading to costly downtime and unplanned maintenance. The most common failure mode is attributed to so-called axial cracks or white-etching cracks, which primarily affect the intermediate and high-speed-stage bearings. The high-speed-shaft and bearing loads and sliding will be measured with a specially instrumented gearbox installed in a 1.5-megawatt turbine at the National Wind Technology Center in an upcoming test campaign. Additional instrumentation will also measure the tribological environment of these bearings, including bearing temperatures, lubricant temperature and water content, air temperature and humidity, and stray electrical current across the bearings. This paper fully describes the instrumentation package and summarizes initial results.
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: Benjamin J. Gould
Author: Benjamin J. Gould
Author: Reinder Hindrik Vegter
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Author: David Vaes
Author: David Vaes
Author: Ningxin Zhao
Author: Johan Luyckx