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Devianee Mulliah
Devianee
Mulliah
Molecular dynamics simulations of nanofriction and wear
Loughborough University
2011
untagged
Mathematical Sciences not elsewhere classified
2011-02-14 11:02:25
Thesis
https://repository.lboro.ac.uk/articles/thesis/Molecular_dynamics_simulations_of_nanofriction_and_wear/9376007
This thesis presents simulations of nanometre-scale ploughing friction and wear
behaviour when a pyramidal diamond indenter is ploughed through the surface
of bcc and fcc metals and semiconductors. Parallel molecular dynamics (MD)
simulations of nanoindentation followed by nanoscratching using Newtonian
mechanics have been employed to investigate the different friction mechanisms
occurring at the atomic scale. Three models have been developed to carry
out our investigations on nanofriction, namely the steady-state model, the
spring model and the finite temperature model. Each model allows the study
of distinctive aspects of atomic-scale friction. For instance, the steady-state
model was employed to study the behaviour of the friction coefficient, contact
pressure and scratch hardness of a silver surface as a function of depth. The
effect of indenter orientation has also been investigated with results showing a
diverse range of pile-up behaviour. The work material undergoes both elastic and plastic deformation during the scratching and we have studied these to analyse the origins of friction.
The spring model and the finite temperature model have been employed
to investigate the stick-slip phenomenon at a low temperature of 0K and at
room temperature (i.e. 300 K), respectively. The dynamics of the indenter
and the substrate, including the behaviour of the different forces in action and
the coefficient of friction, at particular stick and slip events have been studied.
The variation of the sliding speed and indentation depth and their effects on
the occurrence of the stick-slip events has also been investigated.
Some qualitative comparisons have been made between the results from
the simulations and experiments where possible. Due to available computer
power, feasible indentation depths and scratch lengths were an order of magnitude
smaller than experiment, while simulation times were several orders of
magnitude shorter. The MD simulations, however, gave a good description of
nanoindentation and nanoscratching and correlated well with the experiments.