Wind turbine gearbox bearings fail with the service life is much shorter than the designed life.Gearbox bearings are subjected to rolling contact fatigue(RCF)and they are observed to fail due to axial cracking,surface...Wind turbine gearbox bearings fail with the service life is much shorter than the designed life.Gearbox bearings are subjected to rolling contact fatigue(RCF)and they are observed to fail due to axial cracking,surface flaking,and the formation of white etching areas(WEAs).The current study reviewed these three typical failure modes.The underlying dominant mechanisms were discussed with emphasis on the formation mechanism of WEAs.Although numerous studies have been carried out,the formation of WEAs remains unclear.The prevailing mechanism of the rubbing of crack faces that generates WEAs was questioned by the authors.WEAs were compared with adiabatic shear bands(ASBs)generated in the high strain rate deformation in terms of microstructural compositions,grain refinement,and formation mechanism.Results indicate that a number of similarities exist between them.However,substantial evidence is required to verify whether or not WEAs and ASBs are the same matters.展开更多
Sub-surface crack networks in areas of altered microstructure are a common cause for bearing failures.Due to its appearance under light microscopy,the damage pattern is referred to as White Etching Cracks(WEC).The roo...Sub-surface crack networks in areas of altered microstructure are a common cause for bearing failures.Due to its appearance under light microscopy,the damage pattern is referred to as White Etching Cracks(WEC).The root causes leading to the formation of WEC are still under debate.Nevertheless,it has already been shown that atomic hydrogen can have an accelerating effect on the formation and propagation of WEC.In addition to hydrogen pre-charging,hydrogen can be released and absorbed during rolling/sliding due to the decomposing of the lubricant and water.The current work focuses on the analysis of the hydrogen content of cylindrical roller thrust bearings after testing in a FE8 type test rig using two different lubricants.Within the framework of this work,two different hydrogen analysis methods were used and assessed regarding their applicability.The results show that the so-called Hydrogen Collecting Analysis(HCA)is more suitable to investigate the correlation between lubricant chemistry and hydrogen content in the test bearings than the Local Hydrogen Analysis(LHA).The measurements with the HCA show a continuously increasing freely movable and diffusible hydrogen content under tribological conditions,which leads to the formation of WEC.Comparative tests with an oil without hydrogen showed that the tendency of the system to fail as a result of WEC can be reduced by using a lubricant without hydride compounds.展开更多
基金This work was financially supported by the National Natural Science Foundation of China(Grant No.51275225).
文摘Wind turbine gearbox bearings fail with the service life is much shorter than the designed life.Gearbox bearings are subjected to rolling contact fatigue(RCF)and they are observed to fail due to axial cracking,surface flaking,and the formation of white etching areas(WEAs).The current study reviewed these three typical failure modes.The underlying dominant mechanisms were discussed with emphasis on the formation mechanism of WEAs.Although numerous studies have been carried out,the formation of WEAs remains unclear.The prevailing mechanism of the rubbing of crack faces that generates WEAs was questioned by the authors.WEAs were compared with adiabatic shear bands(ASBs)generated in the high strain rate deformation in terms of microstructural compositions,grain refinement,and formation mechanism.Results indicate that a number of similarities exist between them.However,substantial evidence is required to verify whether or not WEAs and ASBs are the same matters.
基金The authors would like to thank the ResearchAssociation for Drive Technology (FVA) for thefunding and support from the research work throughthe research project FVA 707 IV
文摘Sub-surface crack networks in areas of altered microstructure are a common cause for bearing failures.Due to its appearance under light microscopy,the damage pattern is referred to as White Etching Cracks(WEC).The root causes leading to the formation of WEC are still under debate.Nevertheless,it has already been shown that atomic hydrogen can have an accelerating effect on the formation and propagation of WEC.In addition to hydrogen pre-charging,hydrogen can be released and absorbed during rolling/sliding due to the decomposing of the lubricant and water.The current work focuses on the analysis of the hydrogen content of cylindrical roller thrust bearings after testing in a FE8 type test rig using two different lubricants.Within the framework of this work,two different hydrogen analysis methods were used and assessed regarding their applicability.The results show that the so-called Hydrogen Collecting Analysis(HCA)is more suitable to investigate the correlation between lubricant chemistry and hydrogen content in the test bearings than the Local Hydrogen Analysis(LHA).The measurements with the HCA show a continuously increasing freely movable and diffusible hydrogen content under tribological conditions,which leads to the formation of WEC.Comparative tests with an oil without hydrogen showed that the tendency of the system to fail as a result of WEC can be reduced by using a lubricant without hydride compounds.
