The fundamental theories of heat generation and transfer at the friction interface of a
brake assume either matching or not matching surface temperatures by having a
varying or uniform heat partition ratio respectively. In the research presented the
behaviour of heat partition has been investigated in a fundamental study based on
experimental measurements of temperature and the associated modelling and
simulation of heat transfer in a brake friction pair. For a disc brake, an important
parameter that was identified from the literature study is the interface tribo-layer
(ITL), which has been modelled as an equivalent thermal resistance value based on its
thickness and thermal conductivity. The interface real contact area was also an
important parameter in this investigation, and it has been found to affect heat
partitioning by adding its own thermal resistance.
A 2-dimensional (2D) coupled-temperature displacement Finite Element (FE) model is
presented, based on which a novel relationship which characterises the total thermal
resistance (or conductance) at the friction interface has been characterised based on
the ITL thermal properties, the contact area, and the contact pressure at the interface.
Using the model the effect of friction material wear on the total thermal resistance (or
conductance) at the friction interface was predicted and a comparison of the Archard
and Arrhenius wear laws in predicting the wear of a resin bonded composite friction
material operating against a cast iron mating surface is presented.
A 3-dimensional (3D) model is also presented. This model has represented a small
scale disc brake test rig which has been used in parallel with the simulation for
validation in a drag braking scenario. Two simulation conditions with different pad
surface states were investigated, the first having a nominally flat surface, and the
second an adjusted (worn) pad surface based on bedding-in data. The Arrhenius wear
model was applied to significance of including wear on the total thermal resistance at
the friction interface over a short brake application.
A sensitivity analysis on the interface thermal conductance, the location of heat
generation, and the magnitude of contact pressure has identified the importance of
each factor in determining the total thermal resistance (or conductance) at the friction
interface during any friction brake application. It is concluded that the heat
partitioning is insensitive on the location of heat generation, and that the most
sensitive parameter is the contact pressure. / Institution of Mechanical Engineers (IMechE)
| Identifer | oai:union.ndltd.org:BRADFORD/oai:bradscholars.brad.ac.uk:10454/5489 |
| Date | January 2012 |
| Creators | Loizou, Andreas |
| Contributors | Qi, Hong Sheng, Day, Andrew J. |
| Publisher | University of Bradford, School of Engineering, Design & Technology |
| Source Sets | Bradford Scholars |
| Language | English |
| Detected Language | English |
| Type | Thesis, doctoral, PhD |
| Rights | <a rel="license" href="http://creativecommons.org/licenses/by-nc-nd/3.0/"><img alt="Creative Commons License" style="border-width:0" src="http://i.creativecommons.org/l/by-nc-nd/3.0/88x31.png" /></a><br />The University of Bradford theses are licenced under a <a rel="license" href="http://creativecommons.org/licenses/by-nc-nd/3.0/">Creative Commons Licence</a>. |
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