Today many simulation routines concerning railway dynamics employ rather
primitive contact models which
are not necessarily suited for the specific wheel/rail contact problem.
The objective of the present thesis is to derive a more flexible
contact model which can be applied on a variety of
contact problems.
When it comes to the modelling of the wheel/rail contact it is always a
compromise between computational speed and accuracy. Many numerical
methods provide a very good accuracy, but
since most railway simulations necessitates the evaluation of
many consecutive contact situations the relative slow computational
speed is extremely
critical. To avoid this problem the present model is based on an
analytical approach.
The model derived in the thesis is a two-dimensional contact
model based on elastic half spaces. It is demonstrated that the
solution to a three-dimensional contact problem with no spin has many
similarities with the two-dimensional solution. Thus, the results
obtained with the present model can qualitatively be extended to the
three-dimensional contact problem.
The thesis is divided into two parts: one containing the derivation of
the contact model and one containing examples of application. The model
is applied on four different types of contact problems which cannot
be treated with the most common contact models:
- contact between corrugated surfaces
- contact with velocity dependent friction coefficient
- contact between rough surfaces
- non-steady contact
The calculations demonstrate with much clearness that the solution to
the contact problem is very sensitive to the choice of
contact model. This illustrates how crucial it is to employ an adequate
contact model in a given simulation routine in order to obtain a
realistic result. If the assumptions of the contact model do not
fulfill the actual contact situation the result can be most erroneous
and thus misleading.
