The aim of this work was to inform the requirements for the welding processes and finishing techniques to be developed by;
- defining metallurgical and geometric requirements for welds;
- establishing links between the metallurgical and geometric weld properties and damage and degradation modes to better understand what constitutes a ‘good’ weld, and to help demonstrate the advantages of the developed WRIST welding techniques.
A comprehensive literature review was undertaken, covering the properties of available rail steels, existing rail welding techniques (and those of analogous industries) and rail and weld profile measurement techniques.
Developed methodology for controlling finished weld profile to protect against rail surface damage to be applicable to rail fatigue failure from excessive bending stress.
Recommendations for optimum and pragmatic weld profile:
- Optimised to protect against high bending stresses as a result of imperfect longitudinal weld geometry
- Included the effects of: speed, track support stiffness, rail section, temperature and axle load
- Recommended that the relevant EuroNorms (EN 14730-2 and EN 14587-1) be updated to included:
- Existing best practice in Netherlands by ProRail (RLN00127 -1&2) to protect against rail surface damage
- WRIST developed methodology to protect against rail fatigue from bending stress
Investigated the effects of non-homogenous material properties on rail plastic deformation and differential wear.
- Finite element analyses investigated the potential effects of significantly reducing the size of the heat affected zone, without reducing variation in material properties – as could occur with the orbital friction welding process .
Discontinuities in surface and subsurface stresses were observed
- An iterative wear simulation demonstrated that a perfectly finished rail weld with non-homogeneous material properties could develop a ‘cupped’ profile as a result of wear.
A new profile measurement tool was developed to capture the three-dimensional weld profiles – to date longitudinal and lateral profiles are only routinely measured in isolation.
- Three-dimensional profile data enabled the effects of changes to both normal and tangential forces to be investigated.
- A methodology for relating the 3D quality of the weld to rail surface damage was founded, by evaluating the change in rolling radius difference to steering forces and wear and rolling contact fatigue degradation modes.
- Further development of the methodology remains the scope of future work.