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On the running-in of gears
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements. (KUGG)
2010 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The general trend in gear industry, today, is an increased focus on gear transmission efficiency. Gear transmission efficiency losses arise from loaded and unloaded gear contacts, seals, lubricant and bearings. One way of minimising the losses is to lower the lubricant viscosity. This will reduce the speed dependent losses. However, the load dependent losses might increase. To avoid this, the ratio between lubricant film thickness and surface roughness must be maintained, which can be fulfilled by producing smoother gear surfaces. As a starting point for this realisation process, the present manufacturing processes, the design tools and the characteristics of the gear flank interface must be further investigated and developed. This must be achieved with an emphasis on economic production.

This thesis focuses on our understanding of how different gear manufacturing methods —particularly the contribution of the running-in process—affect the surface characteristics, with the view of increasing gearbox efficiency. The thesis consists of a summary and three appended papers.

Paper A and paper B discuss the relationship between design parameters and real gear wheel surfaces manufactured with different manufacturing methods. The research hypothesis was that the contact area ratio is a descriptive parameter for the contact condition. Paper A deals with the influence of manufacturing method on the initial contact conditions and also serves as a validation of the simulation program used. The emphasis in Paper B is the changes that occur during running-in, and to correlate these changes to design requirements. Paper C approaches the influences of manganese phosphate-coating and lubricants with respect to friction and the risk of scuffing at the initial contact.

The main conclusions of this thesis are that the contact area ratio presents a descriptive measure of how surface topography influences the contact, seen at both a global (form deviation) and local (roughness) level. The surface topography caused by the manufacturing method has a significant influence on the contact area ratio. This is an important result, since neither national standards nor commercially available gear evaluation programs handle surface topography on the local scale. Shaving was found to have the highest contact area ratio, and should therefore be the best choice if deviations from case hardening could be minimised. It is also confirmed that gear-like surfaces coated with manganese phosphate have a low coefficient of friction, and raise the limiting load for scuffing failure enormously compared to the ground equivalent.

Place, publisher, year, edition, pages
Stockholm: KTH , 2010. , 39 p.
Series
TRITA-MMK, ISSN 1400-1179 ; 2010:03
Keyword [en]
gears, gear manufacturing, running-in, surface topography, contact area ratio, manganese phosphate
Identifiers
URN: urn:nbn:se:kth:diva-12750ISBN: 978-91-7415-656-0 (print)OAI: oai:DiVA.org:kth-12750DiVA: diva2:318704
Presentation
2010-05-31, Seminar room B242, Brinellvägen 83, KTH Maskinkonstruktion, 10:00 (Swedish)
Opponent
Supervisors
Projects
KUGGSustainable gear transmission realization
Note

QC 20100518

Available from: 2010-05-18 Created: 2010-05-10 Last updated: 2014-10-02Bibliographically approved
List of papers
1. 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
2008 (English)In: Proceedings of Tribology 2008: Surface Engineering of Automotive Powertrains for Environmentally Friendly Transport, 2008Conference paper, Published paper (Refereed)
Identifiers
urn:nbn:se:kth:diva-12900 (URN)
Note
QC 20100518Available from: 2010-05-18 Created: 2010-05-18 Last updated: 2012-02-14Bibliographically approved
2. The influence of manufacturing method on the running-in of gears
Open this publication in new window or tab >>The influence of manufacturing method on the running-in of gears
2011 (English)In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 225, no 10, 999-1012 p.Article in journal (Refereed) Published
Abstract [en]

Striving for higher gear transmission efficiency by using a low-viscosity transmission lubricant affects the lubricant film thickness. To keep the K-ratio (the ratio between the film thickness and the surface roughness) intact, more effort must be put on the surface topography. This paper presents a study of how running-in affects the dry elastic contact area ratio in spur gears using real surface topographies from three common manufacturing methods (green-shaving, honing, and grinding). The test gears were manufactured in case-hardened steel, similar to 20MnCrS5. Surface topography measurements were used as input to a contact analysis boundary element software program. An important hypothesis used in this work is that the dry elastic contact area ratio, i.e. the ratio between real and nominal contact area, can be used as a measure of the contact conditions in gears. It is concluded that running-in differs significantly for the studied manufacturing methods and that the dry elastic contact area ratio gives a consistent description of these changes. The shaved gears have the highest dry elastic contact area ratio after running in, where the ground gears have the lowest dry elastic contact area ratio. The increase in dry elastic contact area ratio is about 30 per cent for the shaved gears, 12 per cent for the honed gears and less than 5 per cent for the ground gears. Extreme value parameters, such as R(p) and R(z), showed relatively good correlation to dry elastic contact area ratio. However no genuine correlation could be found between dry elastic contact area ratio and two-dimensional (2D) surface roughness parameters. Furthermore, traditional gear metrology form parameters do not serve as a good measure on the changes occurring during the running-in.

Keyword
spur gears, running-in, gear manufacturing, shaving, grinding, honing, surface metrology, gear metrology, dry elastic contact, contact area ratio
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-46181 (URN)10.1177/1350650111414471 (DOI)000295284900004 ()2-s2.0-81255136624 (Scopus ID)
Note

Updated from "Manuscript" to "Article"

QC 20111103. QC 20111215

Available from: 2011-11-03 Created: 2011-11-02 Last updated: 2017-12-08Bibliographically approved
3. Scuffing resistance of gear surfaces: influence of manganese phosphate and lubricants
Open this publication in new window or tab >>Scuffing resistance of gear surfaces: influence of manganese phosphate and lubricants
2009 (English)In: Proceedings of 2nd European Conference on Tribology: ECOTRIB 2009, 2009Conference paper, Published paper (Refereed)
Identifiers
urn:nbn:se:kth:diva-12902 (URN)
Note
QC 20100518Available from: 2010-05-18 Created: 2010-05-18 Last updated: 2012-03-21Bibliographically approved

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