This licentiate thesis deals with the influence of transient loading, at high pressures, on the pressure-dilatation relation and frictional properties of lubricants. A Split-Hopkinson pressure bar and a Ball and Bar apparatus have been used for the experiments. Both methods share the same type of evaluation approach: evaluation by analysis of wave propagation in structures. The advantage with this method is that results are presented as function of time, i.e. every experiment yields a history of the studied event, not just a single value. Different theoretical evaluation methods have been used and refinements have been made by introducing compensation terms in order to enhance accuracy. Several lubricants have been studied and an empirical second-degree polynomial has been suggested, for a naphthenic mineral oil and a synthetic 5P4E oil, describing the pressure-dilatation relation over a wide pressure range. It is found that 5P4E exhibits lower compressibility, i.e. higher stiffness than the naphthenic oil. Curves representing friction coefficient as function of time for different lubricants at different pressures are included. It is evident that the Naphthenic- and Paraffinic mineral oils have the highest friction coefficient followed by Polyglycol, Polyalphaolefin and Rape seed oil. The observed distinctions agree well with the expected outcome on basis of molecular structure and pressure variation and correlates well with other density and friction investigations. A general trend of decreasing friction coefficient with increasing pressure is discovered. / Godkänd; 2000; 20070318 (ysko)
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:ltu-26507 |
| Date | January 2000 |
| Creators | Åhrström, Bert-Olof |
| Publisher | Luleå |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Licentiate thesis, comprehensive summary, info:eu-repo/semantics/masterThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | Licentiate thesis / Luleå University of Technology, 1402-1757 ; 2000:13 |
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