Gearbox condition monitoring in wind turbines: A review

With the mounting application of carburized or case-hardening gears and higher requirements of heavy-load, high-speed in mechanical systems such as wind turbines, helicopters, ships, etc., contact fatigue issues of gears are becoming more preponderant. Recently, significant improvements have been made on the gear manufacturing process to control subsurface-initiated failures, hence, gear surface-initiated damages, such as micropitting, should be given more attention. The diversity of the influence factors, including gear materials, surface topographies, lubrication properties, working conditions, etc., are necessary to be taken into account when analyzing gear micropitting behaviors. Although remarkable developments in micropitting studies have been achieved recently by many researchers and engineers on both theoretical and experimental fields, large amounts of investigations are yet to be further launched to thoroughly understand the micropitting mechanism. This work reviews recent relevant studies on the micropitting of steel gears, especially the competitive phenomenon that occurs among several contact fatigue failure modes when considering gear tooth surface wear evolution. Meanwhile, the corresponding recent research results about gear micropitting issues obtained by the authors are also displayed for more detailed explanations.

https://www.mdpi.com/2079-6412/9/1/42/pdf

A Review on Micropitting Studies of Steel Gears

Effects of case hardening properties on the contact fatigue of a wind turbine gear pair

A model to predict initiation and propagation of micro-pitting on tooth flanks of spur gears

An improved-accuracy method for fatigue load analysis of wind turbine gearbox based on SCADA

Experimental and analytical study of gear micropitting initiation and propagation under varying loading conditions

Wind turbine gearbox operates under a wide array of highly fluctuating and dynamic load conditions caused by the stochastic nature of wind and operational wind turbine controls. Micropitting damage...

Prediction of Wind Turbine Gear Micropitting under Variable Load and Speed Conditions Using ISO/TR 15144-1: 2010

This study investigates the probabilistic risk of gear tooth flank micro-pitting in wind turbine (WT) gearboxes and shows how relatively slow rate of supervisory control and data acquisition (SCADA) data, recorded during operation, can be used to analyse the onset of gear surface damage. Field measured time series of SCADA signals, including wind speed, generator power and rotational speed, were used to obtain the statistical variation of gear shaft torque and rotational speed. From the SCADA data obtained over a 2.2 year period random number datasets of smaller sizes were selected. Based on these random number datasets the effect of gear shaft torque and rotational speed variations on the probabilistic risk of gear micro-pitting was investigated. Determinations of the gear tooth flank contact stress and lubricant film thickness were based on the technical report of gear micro-pitting, ISO/TR 15144-1 (2010). The study has shown that the considered pinion gear is subjected to high load conditions resulting in high contact stresses. The variation of rotational speed causes greater sliding between the gear teeth. The results of specific lubricant film thicknesses have shown that there is considerable risk of gear micro-pitting under the operational conditions recorded from the SCADA field data.

Probabilistic analysis of gear flank micro-pitting risk in wind turbine gearbox using supervisory control and data acquisition data

This paper presents an investigation of the effect of load variation on gear tooth surface micropitting, for an application in planet gears in a wind turbine gearbox. To study the effect of load variation, two methods are employed: an experimental testing of gear micropitting under variable loading and a probabilistic analysis of gear contact stress and specific lubricant film thickness variations using the ISO Technical Report ISO/TR 15144-1:2010. The load variation of wind turbine gearbox is derived from SCADA (Supervisory Control and Data Acquisition) data recorded in operation. Both experimental and analytical results show that high levels of contact stress, load variations and repeated load cycles are determinant factors for the initiation and propagation of micropitting of gear tooth surfaces.

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I.S. Al-Tubi

Papers

Experimental and analytical study of gear micropitting initiation and propagation under varying loading conditions

Prediction of Wind Turbine Gear Micropitting under Variable Load and Speed Conditions Using ISO/TR 15144-1: 2010

Probabilistic analysis of gear flank micro-pitting risk in wind turbine gearbox using supervisory control and data acquisition data

Analytical and Experimental Study of Gear Surface Micropitting Due to Variable Loading