Analysis of bearing steel exposed to rolling contact fatigue

K T Hansen,S Fæster,H K Danielsen,A Natarajan,D Juul Jensen,O V Mishin,P Klit

doi:10.1088/1757-899x/219/1/012024

Abstract

The objective of this work is to characterize fatigue damage in roller bearings under conditions of high load and slippage. A test rig constructed for rolling contact fatigue tests of rings is described, and test results are presented for rings taken from two spherical roller bearings. The preparation of the rings and the loading situation are explained. Test conditions are chosen with the aim of achieving pitting formation at the contacting surfaces. During testing the contact pressure, torque and the rotational speed are monitored and recorded. After testing the tested rings have been characterized using X-ray tomography and scanning electron microscopy. The observations confirm that rolling contact fatigue testing at high loads leads to pitting failure at the contacting surfaces. The pitting mostly appears on one side of the contact, attributed to a non-uniform contact pressure in the axial direction.

Highlights

Bearings in wind turbine drivetrains operate under highly dynamic conditions, even during normal operation
A test rig constructed for rolling contact fatigue tests of rings is described, and test results are presented for rings taken from two spherical roller bearings
Rolling contact fatigue test data The force applied from the hydraulic loading arrangement during the rolling contact fatigue (RCF) test is shown in figure 3

Summary

Introduction

Bearings in wind turbine drivetrains operate under highly dynamic conditions, even during normal operation. This is due to the interaction of the wind turbine rotor with wind turbulence, wind shear and yaw, which result in varying cyclic loads on the main shaft. The drivetrain configuration can be based on either a 3-stage high speed geared transmission, a medium speed transmission or a direct drive (gearless). The main shaft is connected to the rotor hub through one or two main bearings. In some large direct drive gearless configurations, the main bearing, along with the generator, is bolted to the hub, front-mounting the entire drivetrain to reduce deflections [1]. The main bearings and/or gearbox bearings are always loaded dynamically in the axial and radial directions

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