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On tribological design in gear tooth contacts
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.ORCID iD: 0000-0003-4447-3363
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The correct tribological design will have a considerable effect on a gear’s service life and efficiency. The purpose of this thesis is to clarify the impact of variation in the gear tooth flank tribological system on the gear contact load capacity – to increase the understanding of how surface topography and lubricant interact.

In this thesis the variation in surface topography inherent in the manufacturing method has been shown, by experimental work and computer simulations, to be an important factor for the contact condition in the early life of gears. Surface analysis revealed that the formation and composition of surface boundary layers depends strongly on the chemical composition of the lubricant, but also on pre-existing surface boundary layers. Additionally, surface boundary layers play a major role in frictional behaviour, wear and in allowing the lubricant to react properly with the surfaces.

Paper A presents the current ISO 6336 calculation of surface durability. A robust design approach was used to investigate the extent to which the current standard for calculation of surface durability allows for manufacturing variations and the choice of lubricant.

Paper B investigates the extent to which a logarithmical profile modification can increase gear contact pressure robustness compared to traditional lead profiles for gears.

Paper C compares different gear manufacturing methods and their as-manufactured (fresh unworn) surface topographies, using measured surface topographies as input to a contact simulation program.

Paper D examines surface boundary layer formation and the corresponding wear in relation to different anti-wear additives in an environmentally adapted base oil.

Papers E and F make use of specimens with surface topographies imitating two gear manufacturing methods (grinding and superfinishing) to be used in a twin-disc and barrel-on-disc machine respectively. The contacts are analysed by friction measurements and simulations combined with methods for surface analysis.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. , 40 p.
Series
Trita-MMK, ISSN 1400-1179 ; 2012:18
Keyword [en]
friction, gear contact, gear manufacturing, surface boundary layers, surface topography, wear
National Category
Mechanical Engineering Other Mechanical Engineering Tribology
Identifiers
URN: urn:nbn:se:kth:diva-102742ISBN: 978-91-7501-493-7 (print)OAI: oai:DiVA.org:kth-102742DiVA: diva2:556276
Public defence
2012-10-15, Studion Gladan, Brinellvägen 85, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20120925

Available from: 2012-09-25 Created: 2012-09-24 Last updated: 2012-09-25Bibliographically approved
List of papers
1. Influence of gear surface roughness, lubricant viscosity and quality level on ISO 6336 calculation of surface durability
Open this publication in new window or tab >>Influence of gear surface roughness, lubricant viscosity and quality level on ISO 6336 calculation of surface durability
2009 (English)Report (Other academic)
Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2009. 25 p.
Series
Trita-MMK, ISSN 1400-1179 ; 2009:17
National Category
Tribology
Identifiers
urn:nbn:se:kth:diva-74603 (URN)
Note
QC 20120213Available from: 2012-02-13 Created: 2012-02-03 Last updated: 2012-09-25Bibliographically approved
2. Logarithmical Crowning for Spur Gears
Open this publication in new window or tab >>Logarithmical Crowning for Spur Gears
2010 (English)In: Strojniski vestnik, ISSN 0039-2480, Vol. 56, no 4, 239-244 p.Article in journal (Refereed) Published
Abstract [en]

Gear tooth modifications, such as lead crowning, are often recommended to compensate for misalignment (e.g. assembly deviations). Lead crowning means that the tooth centre is slightly thicker than the tooth edges and is usually described as a circular arc profile. The use of crowning shifts the peak load from the tooth flank edges and, therefore, reduces the risk for high contact pressures at the edges, which can otherwise result in a shortened service life. In this study a logarithmical lead profile was compared with traditional lead profile modifications for gears. The profiles were applied on a spur gear pair and a numerical method for contact analysis was used to calculate the contact pressure distribution at the pitch diameter. All lead profiles were optimised with respect to low contact pressure at a specific normal load, a specified maximum misalignment in the plane of action and a tooth flank edge contact criteria. The results show that the logarithmical profile responds differently to misalignments compared to the traditional lead profile modifications. The logarithmical profile resulted in lower maximum contact pressures for small misalignments and is, therefore, of further interest in terms of achieving a robust gear design. (C) 2010 Journal of Mechanical Engineering. All rights reserved.

Keyword
spur gear, lead crowning, misalignment, contact pressure
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-27228 (URN)000279265400003 ()2-s2.0-77952772204 (Scopus ID)
Note
QC 20101217Available from: 2010-12-17 Created: 2010-12-09 Last updated: 2017-12-11Bibliographically approved
3. Influence of real surface topography on the contact area ratio in differently manufactured spur gears
Open this publication in new window or tab >>Influence of real surface topography on the contact area ratio in differently manufactured spur gears
2012 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 56, 72-80 p.Article in journal (Refereed) Published
Abstract [en]

Surface topography measurements from spur gears produced using four different manufacturing methods were used as input to a contact analysis programme. All test gears were case-hardened, two gears were machined in the hardened state using honing and grinding respectively, and two gears were machined in the non-hardened state using hobbing and hobbing followed by green-shaving respectively. The results show that the surface topography caused by the manufacturing methods has a large influence on the real contact area in the early life of the gear. The green-shaved gear surfaces and the honed gear surfaces have the highest contact area ratio after manufacturing (as-manufactured), which could be advantageous for future gear life with respect to e.g. the running-in process.

Keyword
Surface topography, Contact mechanics, Spur gears, Finishing
National Category
Tribology
Identifiers
urn:nbn:se:kth:diva-102738 (URN)10.1016/j.triboint.2012.06.014 (DOI)000308284000009 ()2-s2.0-84864052908 (Scopus ID)
Funder
Vinnova
Note

QC 20120925

Available from: 2012-09-25 Created: 2012-09-24 Last updated: 2017-12-07Bibliographically approved
4. Wear in environmentally adapted lubricants with AW technology
Open this publication in new window or tab >>Wear in environmentally adapted lubricants with AW technology
2008 (English)In: Journal of Synthetic Lubrication, ISSN 1557-6841, Vol. 25, no 4, 137-158 p.Article in journal (Refereed) Published
Abstract [en]

The purpose of the study was to examine the tribofilm formation and the corresponding wear occurring in the boundary lubrication regime in environmentally adapted lubricants, i.e. when using synthetic ester base fluids with different anti-wear additives. AW additives of the following types were studied: phosphorus, sulphur–phosphorus and sulphur–nitrogen together with an additive based on carbon, hydrogen, oxygen and nitrogen chemistry. In addition, the base fluid itself was tested.Wear was studied in a pin-on-disc-machine giving the wear coefficient. The surfaces were analysed by glow discharge-optical emission spectroscopy, revealing the surface reactions formed by the additives. The results indicate that the wear number decreases with increasing reacted surface layer depth as well as with increasing oxide layer depth. Also, the results indicate that a highly polar base fluid give relatively low wear numbers even without additives.

Keyword
tribology, environmentally adapted labricants, additives, surface analysis
National Category
Tribology
Identifiers
urn:nbn:se:kth:diva-78644 (URN)10.1002/jsl.57 (DOI)2-s2.0-57149142254 (Scopus ID)
Note
QC 20120217Available from: 2012-02-08 Created: 2012-02-08 Last updated: 2012-09-25Bibliographically approved
5. Effect of gear surface and lubricant interaction on mild wear
Open this publication in new window or tab >>Effect of gear surface and lubricant interaction on mild wear
2010 (English)Conference paper, Published paper (Refereed)
National Category
Tribology
Identifiers
urn:nbn:se:kth:diva-74584 (URN)
Conference
International Tribology Congress - ASIATRIB 2010 Perth, Australia, 5-9 December 2010
Note
QC 20120206Available from: 2012-02-06 Created: 2012-02-03 Last updated: 2012-09-25Bibliographically approved
6. Study of surface roughness and surface orientation onfriction in rolling/sliding contacts: barrel-on-disc versustwin-disc
Open this publication in new window or tab >>Study of surface roughness and surface orientation onfriction in rolling/sliding contacts: barrel-on-disc versustwin-disc
(English)Manuscript (preprint) (Other academic)
National Category
Tribology
Identifiers
urn:nbn:se:kth:diva-102740 (URN)
Note

QS 2012

Available from: 2012-09-25 Created: 2012-09-24 Last updated: 2013-10-31Bibliographically approved

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