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Friction and heat generation in rolling/sliding contacts in the elastohydrodynamic lubrication regime

Almail, Salem 2020. Friction and heat generation in rolling/sliding contacts in the elastohydrodynamic lubrication regime. PhD Thesis, Cardiff University.
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Abstract

This thesis presents both experimental and theoretical investigations to study the friction and heat generation in the rolling/sliding contacts in the elastohydrodynamic lubrication (EHL) regime, using a twin-disc test rig that was previously built and used for this purpose. An experiment was carried out, where the data recorded were analysed using a numerical model that was developed during this work to find the heat transfer coefficient h and the heat partition β, and to compare the results of this numerical model with those measured during the EHL experiment. The downhill simplex method for error minimisation was used in this work, which was able to calculate the minimum total error between measurement and model temperatures of both discs for the same given (  , hs) combination, rather than for each disc individually. Some uncertainties showed up during these analyses, which led to extensive investigations made by modifying the numerical model and re-designing some test rig hardware (shafts and thermocouple amplifiers). The differences between model and measured temperatures were analysed to identify whether or not the individual thermocouple measurements were consistent with each other and the fundamental conduction equation. This showed that at least two measurements were unreliable on each disc. Synthesised experiments were then constructed using the model and measured lower boundary temperatures from the EHL experiments. These were used to assess the influence of noise in the data on the results, to find the optimum position of thermocouples, and to investigate the resolution of the thermocouples and logging recorders. The test rig was also subjected to further developments. Firstly, new integral shafts and test discs were designed in order to replace the existing components in order to eliminate the uncertainty of thermal asymmetry in the shaft and disc configurations. Secondly, new on-shaft thermocouple amplifiers were commissioned to adapt the test rig so as to overcome the uncertainties revealed in the previous investigations.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Engineering
Uncontrolled Keywords: Elastohydrodynamic; EHL Contact; Hertzian Contact; Heat Partition in EHL; Temperature Measurements in EHL; Rolling/Sliding contacts in EHL.
Date of First Compliant Deposit: 22 July 2020
Last Modified: 22 Jul 2020 08:16
URI: http://orca.cf.ac.uk/id/eprint/133639

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