Damage initiation and evolution in silicon nitride under unlubricated and lubricated rolling contact fatigue

0450462 - ÚFM 2016 RIV ES eng A - Abstrakt
Raga, R. - Khader, I. - Chlup, Zdeněk - Kailer, A.
Damage initiation and evolution in silicon nitride under unlubricated and lubricated rolling contact fatigue.
14th International Conference European Ceramics Society. Toledo: ECERS, 2015. ISBN 978-84-606-9257-7.
[ECERS 14 - International Conference of the European Ceramic Society /14./. 21.06.2015-25.06.2015, Toledo]
Institucionální podpora: RVO:68081723
Klíčová slova: silicon nitride * rolling contact fatigue * damage initiation
Kód oboru RIV: JL - Únava materiálu a lomová mechanika

This study focuses on the damage mechanisms in silicon nitride undergoing non - conforming contact. The study arose in order to understand the damage involved in hybrid contact (e.g., ceramic - metal co ntact in hybrid bearings). Damage under rolling contact loading is a complex phenomenon due to contacting surfaces undergoing alternating cyclic tension - compression stress fields. In lubricated case the mating partners are sufficiently separated by a lubri cant film under the action of elastohydrodynamic lubrication (EHL); where as in unlubricated rolling the mating partners comes in direct contact. The damage manifested could differ substantially under lubricated and unlubricated rolling contact for same lo ading conditions. Understanding damage under different loading conditions is essential in order to prevent premature failure of the material in service. To get an insight into the prevailing damage modes comparable to those in real application is to test t he material experimentally. A rolling contact experiment was designed in order to mimic the contact conditions appearing in hybrid bearings at contact pressures ranging from 3 to 6 GPa; the experiments were run without slip. Extensive surface and subsurfac e damage analysis were performed with conventional ceramographic as well as with focused ion beam (FIB) cross - sectioning to understand the failure modes. Additionally Finite element simulations were carried out to illustrate the stress state under differen t loading conditions. The rolling contact experiments showed considerable wear under dry conditions even without gross slip between the contact partners. With increasing load change in contact conformity was observed due to progressive wear. Cracks initiat ed from surface as well as subsurface were detected.
Trvalý link: http://hdl.handle.net/11104/0252337