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A study of the running-in and efficiency of ground gears
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.ORCID iD: 0000-0003-2489-0688
(English)Manuscript (preprint) (Other academic)
Keyword [en]
Running-in, gears; efficiency, surface roughness
National Category
Tribology
Research subject
Machine Design
Identifiers
URN: urn:nbn:se:kth:diva-152696OAI: oai:DiVA.org:kth-152696DiVA: diva2:751460
Note

QS 2014

Available from: 2014-10-01 Created: 2014-10-01 Last updated: 2014-10-06Bibliographically approved
In thesis
1. Influence of running-in on gear efficiency
Open this publication in new window or tab >>Influence of running-in on gear efficiency
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
gears; gear manufacturing; running-in; efficiency, friction, surface topography
National Category
Tribology
Research subject
Machine Design
Identifiers
urn:nbn:se:kth:diva-152699 (URN)978-91-7595-258-1 (ISBN)
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
2. Churning losses and efficiency in gearboxes
Open this publication in new window or tab >>Churning losses and efficiency in gearboxes
2014 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Efficient transmissions systems are key to producing competitive motor vehicles that have a smaller environmental impact. Gears are the main components in vehicle transmissions and although they are already highly efficient, there is still room for improvement. In this study, the focus falls on the lubricant used to create separating films between gears and todissipate heat. When driving, the gears churn this lubricant, giving rise to power losses that are related to the amount and properties of the lubricant. However, any attempt to reduce these losses must not compromise the required lubrication and heat dissipation. Paper A reports on the use of an FZG gear test rig to investigate power losses and heat generation for different gear immersion depths, surface roughness and coatings. The results show that lower gear roughness reduces gear mesh losses and heat generation. A polishing affect was obtained when a non-coated gear ran against a coated gear.The aim of the research reported in paper B was to increase the accuracy of efficiency testing. It investigated how and whether repeated disassembly and re-assembly of the same test equipment, as well as test performance and rig conditions, affect the measured torque loss in an FZG gear test rig. It was shown that the measured torque loss changes between one assembly and another. Repeatability between tests is crucial for accurate conclusions.The aim of the research reported in paper C was to study whether gear efficiency could be increased by a running-in procedure, which would reduce the need for a coolant. A back-to-back gear test rig was used to test two running-in loads. Higher gear mesh efficiency was seen when a higher running-in load was used.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. 22 p.
Series
TRITA-MMK, ISSN 1400-1179 ; 2014:11
Keyword
gears, efficiency, temperature, running-in, assembly, torque loss, surface roughness
National Category
Tribology
Identifiers
urn:nbn:se:kth:diva-152914 (URN)978-91-7595-277-2 (ISBN)
Presentation
2014-10-23, Sal B242, Brinellvägen 85 KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Energy Agency
Note

QC 20141006

Available from: 2014-10-06 Created: 2014-10-02 Last updated: 2014-10-06Bibliographically approved

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