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Influence of running-in on gear efficiency
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements. KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The general trend in gear industry is an increased focus on gear transmission efficiency. This thesis focuses on the understanding of how different gear manufacturing methods – particularly the contribution of the running-in process – affect the surface characteristics and friction response, with the purpose of increasing gearbox efficiency. The thesis consists of a summary and five appended papers.

The research hypothesis in paper A and paper B was that the dry elastic 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. The emphasis in paper B is the changes that occur during running-in and correlating these changes to design requirements. Paper C examines the influence of manganese phosphate coating and lubricants, with respect to friction and the risk of scuffing at the initial contact. Paper D examines the effect of running-in load on the friction response for different surfaces. In paper E, the question of whether the load during running-in influences the gear mesh efficiency is further expounded.

The main conclusions of this thesis are that the running-in influences the gear mesh efficiency; a high running-in load enhances the gear mesh efficiency. The difference in mesh efficiency is in the range of one tenth of a per cent. Thus, the influence of running-in cannot be neglected because it is in the same order of magnitude as reported for other gear efficiency enhancements. Furthermore, the dry elastic contact area ratio presents a descriptive measure of how surface topography influences the contact, 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. Shaving was found to have the highest contact area ratio, and would therefore be the best choice if deviations from case hardening could be minimised. It was also confirmed that surfaces coated with manganese phosphate raise the limiting load for scuffing failure up to 13 times compared to the uncoated ground equivalent.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. , 56 p.
Series
TRITA-MMK, ISSN 1400-1179 ; 2014:09
Keyword [en]
gears; gear manufacturing; running-in; efficiency, friction, surface topography
National Category
Tribology
Research subject
Machine Design
Identifiers
URN: urn:nbn:se:kth:diva-152699ISBN: 978-91-7595-258-1 (print)OAI: oai:DiVA.org:kth-152699DiVA: diva2:751491
Public defence
2014-10-24, Sal B242, Brinellvägen 83, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20141002

Available from: 2014-10-02 Created: 2014-10-01 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
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
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
(English)Manuscript (preprint) (Other academic)
Keyword
gears, scuffing, lubrication, case-hardened steel, manganese phosphate
National Category
Mechanical Engineering Tribology
Research subject
Machine Design
Identifiers
urn:nbn:se:kth:diva-152698 (URN)
Note

QS 2015

Available from: 2014-10-01 Created: 2014-10-01 Last updated: 2015-02-23Bibliographically approved
4. Analysis of running-in using Stribeck curves, with application to gear mesh
Open this publication in new window or tab >>Analysis of running-in using Stribeck curves, with application to gear mesh
(English)Manuscript (preprint) (Other academic)
Keyword
Running-in, Surface topography, Friction, Lubrication regimes
National Category
Mechanical Engineering Tribology
Research subject
Machine Design
Identifiers
urn:nbn:se:kth:diva-152697 (URN)
Note

QS 2014

Available from: 2014-10-01 Created: 2014-10-01 Last updated: 2014-10-02Bibliographically approved
5. A study of the running-in and efficiency of ground gears
Open this publication in new window or tab >>A study of the running-in and efficiency of ground gears
(English)Manuscript (preprint) (Other academic)
Keyword
Running-in, gears; efficiency, surface roughness
National Category
Tribology
Research subject
Machine Design
Identifiers
urn:nbn:se:kth:diva-152696 (URN)
Note

QS 2014

Available from: 2014-10-01 Created: 2014-10-01 Last updated: 2014-10-06Bibliographically approved

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