Geometrical Design of Insulated Rail Joints

Abstract

Insulated rail joints (IRJs) play a crucial
role in modern railway systems. They serve the critical function of
electrically isolating rail segments through the placement of an insulating
material, known as an end plate, between two rail ends. This insulating
material is necessary to define track segments, which makes it possible to
determine the position of trains within the railway system. Knowing a train’s
position is key to ensuring efficiency, reliability, and safety. While these
joints are highly important, they are also vulnerable. The interruption in rail
geometry results in a complex interaction between wheel and rail, giving rise
to high dynamic impact forces. Traditional IRJs, or squared IRJs, have the cut
between the rail ends orthogonal to the rail. In this thesis, an alternative
design with a non-orthogonal junction angle is analyzed.

The primary goal of this thesis is to
determine how the junction angle influences both the global wheel-rail
interaction and the local contact pressure at the wheel-rail interface. To
achieve this, the thesis is split into two parts: (1) the global wheel-rail
interaction analysis, which studies the influence of the junction angle on the
interaction between the wheel and rail using simplified geometries in a
kinematic approach, and (2) a local wheel-rail interface analysis, which
studies the effect of the junction angle on an assumed uniform contact pressure
between wheel and rail.

The global analysis revealed the
possibility of two distinct contact scenarios, depending on lateral wheel position
and dip angles greater than zero. In contact scenario 1, the effective geometry
and the resulting vertical impulse remained identical to those of squared
joints. However, in contact scenario 2, the active geometry of the joint
changes, leading to an increase in vertical impulse of the wheel’s center of
mass. Additionally, the introduction of the junction angle increased the
likelihood of less favorable contact conditions for contact scenario 1 and
guaranteed less favorable contact conditions for contact scenario 2. The local
analysis showed that uniform contact pressure between the wheel and rail increases
slightly for non-orthogonal junction angles with dip angles near zero. For
small junction angles (resulting in a long cut in the longitudinal direction),
outside of the practical range, the rate of change of the contact pressure was
greatly reduced.

The study has shown that insulated rail
joints with non-orthogonal junction angles within the practical range do not
provide significant improvements in dynamic performance compared to traditional
squared joints. However, due to the assumptions made in this model, the
complexity of the rail geometry was significantly simplified, and material
elasticity was not considered. These limitations are expected to affect the
contact behavior and could affect the results. This should be investigated
further. The second model demonstrates that for junction angles within the
practical range, the assumed uniform contact pressure increased slightly.
However, for very small junction angles, which result in impractically elongated
joints, the rate of change in uniform contact pressure can be greatly reduced.