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Contact stresses and crack mechanisms in rolling/sliding contacts
Dissertation (M. Ing.) -- University of Stellenbosch, 1990.
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| Other Authors: | |
| Format: | Thesis |
| Language: | English |
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Stellenbosch : Stellenbosch University
2012
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| _version_ | 1867613809788583936 |
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| access_status_str | Open Access |
| author | Coutlakis, John |
| author2 | Endres, W. |
| author_browse | Coutlakis, John Endres, W. |
| author_facet | Endres, W. Coutlakis, John |
| author_sort | Coutlakis, John |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Dissertation (M. Ing.) -- University of Stellenbosch, 1990. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/68692 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:42:03.173Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2012 |
| publishDateRange | 2012 |
| publishDateSort | 2012 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/68692 Contact stresses and crack mechanisms in rolling/sliding contacts Coutlakis, John Endres, W. Stellenbosch University. Faculty of Engineering. Dept. of Mechanical & Mechatronic Engineering. Rolling contact Gearing -- Lubrication Bearings (Machinery) Mechanical wear Dissertations -- Mechanical engineering Dissertation (M. Ing.) -- University of Stellenbosch, 1990. The purpose of this dissertation was to study the phenomenon of pitting in rolling and rolling/sliding contacts, such contacts being found in gears and rolling element bearings. A literature survey revealed that, even after fifty five years of research on this subject, there was no conclusive evidence and agreement as to the basic causes and mechanism of the phenomenon. Pitting only occurs in lubricated contacts. The typical textbook explanation is that some lubricant is trapped in a crack which must have a suitable orientation to the rolling direction. A high hydraulic pressure then develops and causes the crack to propagate. However, this widely accepted theory was based on pure rolling conditions. In addition, practical evidence of crack propagation orientations when sliding is present suggests that the direction of crack propagation is determined by the direction of the applied surface shear stress. The lubricant entrapment mechanism cannot logically explain this observation. A photoelastic experiment was carried out to verify if the direction of crack propagation was determined by the direction of the applied surface shear stress. The experiment showed that, with the contact surfaces loaded with both normal and tangential forces, a simulated crack, positioned in the region of tensile principal stress caused by the applied shear, has a tensile stress at the crack tip (without any lubricant). This crack could thus be expected to propagate. The orientation of this crack corresponds with observed orientations found in practice. However, the experiment cannot be conclusive, since a lubricated contact could not be simulated for comparison purposes. There is no evidence to disprove an hydraulic pressure mechanism theory which is dependant on the directions of both rolling velocity and applied shear stress. There is agreement among all investigators that a lubricant is not necessary for the initiation of a crack. The effect of a lubricant on crack propagation is not clear. However it appears that a lubricant is necessary for pit formation. Masters 2012-08-27T12:26:43Z 2012-08-27T12:26:43Z 1990 Thesis http://hdl.handle.net/10019.1/68692 en Stellenbosch University 186 pages : ill. application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Rolling contact Gearing -- Lubrication Bearings (Machinery) Mechanical wear Dissertations -- Mechanical engineering Coutlakis, John Contact stresses and crack mechanisms in rolling/sliding contacts |
| title | Contact stresses and crack mechanisms in rolling/sliding contacts |
| title_full | Contact stresses and crack mechanisms in rolling/sliding contacts |
| title_fullStr | Contact stresses and crack mechanisms in rolling/sliding contacts |
| title_full_unstemmed | Contact stresses and crack mechanisms in rolling/sliding contacts |
| title_short | Contact stresses and crack mechanisms in rolling/sliding contacts |
| title_sort | contact stresses and crack mechanisms in rolling sliding contacts |
| topic | Rolling contact Gearing -- Lubrication Bearings (Machinery) Mechanical wear Dissertations -- Mechanical engineering |
| url | http://hdl.handle.net/10019.1/68692 |
| work_keys_str_mv | AT coutlakisjohn contactstressesandcrackmechanismsinrollingslidingcontacts |