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Solid Mechanics & Materials Engineering Group |
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Current Research Projects of Prof. David Nowell
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Fretting Fatigue and Fretting WearFretting fatigue occurs when contacting surfaces are subjected to oscillating loading and can be responsible for premature failure in components such as spline joints, bolted and rivetted connections and dovetail joints between aircraft engine blades and discs. Research in this area has been taking place in Oxford for a number of years and we have four dedicated rigs for experiments on fretting fatigue and fretting wear. Recent work in this area included participation in a joint EPSRC project with the University of Nottingham, which developed improved life prediction methods by combining models of the fretting wear and fretting fatigue processes. A number of smaller experimental projects are also being carried out, including work on fretting fatigue of composites (Rolls-Royce), and high temperature fretting (Rolls-Royce/TSB). Research student Rodolfo Fleury started in 2011 and is looking at fretting fatigue problems involving single crystal materials.
FrictionWork on fretting has led to a more fundamental interest in the origins and modelling of frictional behaviour. An EPSRC project is being carried out with Imperial College, aimed at developing a more predictive approach to the incorporation of friction in larger scale models, e.g. for the prediction of vibration or structural integrity. The initial phase of the work focussed on developing a robust method of measuring interface response which is largely independent of macroscopic geometry. More recent work has examined the pressure dependence of tangential stiffness and fundamental modelling of asperity interaction.
Modelling and Prediction of
Residual Stress
David Nowell has been involved in a number of projects involving the
prediction and measurement of residual stress and/or the consequences
of such stress fields for structural integrity. An EPSRC project
with the University of Bristol developed analytical tools for use with
the deep hole drilling method of residual stress measurement.
Another project, funded by Rolls-Royce and the DTI, involved the
modelling of residual stress fields induced by the inertia welding
process. The approach adopted employed a distribution on misfit
strains (eigenstrains) to capture the fundamental deformation induced
by the process. An EPSRC project is now underway in collaboration
with the Universities of Manchester and Swansea which will generate
improved understanding of the Laser Shock Peening process, used to
induce compressive surface residual stress. Research at Oxford is
building on the earlier eigenstrain work in order to develop a robust
and validated model of the peening process |