Title:
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An optimised wheel-rail contact model for vehicle dynamics simulation
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The wheel-rail interface is a complex component of the dynamic railway vehicle-track
system. The wheel-rail interface governs the motion of a railway vehicle and is
responsible for wheel and track damage such as wear and rolling contact fatigue. Wheelrail
contact models are used extensively in railway engineering to calculate contact forces
and stresses, in order to evaluate dynamic vehicle behaviour or assess track damage.
Due to the complexity of the wheel-rail interaction, and computational limitations,
all wheel-rail contact models make simplifying assumptions so that solutions may be
obtained in an acceptable time.
This thesis presents a survey of current wheel-rail contact models and theories, and
associated literature, focussing on the various simplifications made by the different
approaches. In order to allow an informative comparison of contact model performance
a wheel-rail contact benchmark has been established, detailing carefully defined, challenging
contact conditions. Interested parties were invited to submit solutions for the
contact benchmark cases, and results from ten contributors were received and compared.
From the analysis of current contact models and the contact benchmark results, a new
wheel-rail contact model has been developed. The model is based on a novel relationship
between the normal contact force and the intersecting volume found from virtually
penetrating two, three dimensional contacting bodies. Results from the new contact
model, named the 'Rectified Interpenetration method', were compared favourably to
the recognised methods of Hertz and Kalker.
To aid future validation of wheel-rail contact model and understanding of the wheel.
rail interaction, a feasibility study of a new wheel-rail contact measurement technique
has been undertaken. The technique is based on an established ultrasound method
capable of measuring the normal contact pressure distribution for machined wheel and
rail samples in laboratory conditions. The new technique aims to advance the state of
the art to allow wheel-rail contact measurements under rolling conditions. The study
concluded that there is scope for further development of the technique, and discusses
the transitional difficulties in advancing the static method to rolling contacts.
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