Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - WRIST (Innovative Welding Processes for New Rail Infrastructures)

Teaser

The WRIST project will deliver a step change in the joint performance and reliability for rails, therefore resulting in an extended in-service life. This will result in a significant cost reduction for the maintenance of track, but also free up more capacity for rail traffic...

Summary

The WRIST project will deliver a step change in the joint performance and reliability for rails, therefore resulting in an extended in-service life. This will result in a significant cost reduction for the maintenance of track, but also free up more capacity for rail traffic, including less unforeseen maintenance, and thus less delays for passengers and freight.

In order to do this, within the project two flexible and cost-effective joining processes for rails are being developed, that also recognise also recognise the move of the industry toward higher speeds and axle loads and the need to increase capacity.

The following objectives are defined within the project:

1. To develop two innovative methods (automatic forged aluminothermic welding and orbital friction welding) for joining rails, with the aim of having a smaller weld zone, and minimised loss of mechanical properties in the weld zone.

2. To facilitate an increased use of bainitic rail steel grades that possess greater resistance to the key degradation mechanism of rolling contact fatigue.

3. To permit the achievement of lower life cycle costs for track maintenance and renewal by eliminating the source of higher dynamic forces at “cupped” or irregular geometry welds that are responsible for the more rapid loss of track geometry and necessitate expensive maintenance tamping intervention.

4. To enable an increased use of more environmental friendly joining processes, such as friction welding.

5. To deliver environmental benefits by reducing the use of carbon fuels and gas, reduction of exposure to noise, dust and vibrations by automating and incorporating in-process monitoring of the aluminothermic welding process, more efficient preheating and reduction in remedial grinding to achieve the required straightness.

Work performed

In the first period of the project the focus has been on developing and designing the new welding processes, as well the modelling needed to assist in the experimental work for period 2.

The vehicle-track interaction dynamics modelling has defined the requirements in terms of weld geometries , this can be used to simulate the effect of changes in material properties, or the effect of geometry changes in/around the weld on the rail damage.
The two new joining processes, as defined in the project proposal, have been developed. The hot forge aluminothermic (AT) welding process has been developed up to an industrial first module. Compared to the conventional aluminothermic welding process it can already be stated that this more automated process, coupled with in-process monitoring, reduces the reliance on operator skills, and maximises productivity. For the orbital friction welding process, this will be a complete step change in type of technologies used for rail infrastructure, but this being a more energy efficient and environmentally friendly technique compared to the conventional rail joining technologies, this process should assist in attaining the sustainability goals for transport infrastructure. The orbital friction welding principle has been fully developed; the machine has been designed, with independent controls on the design. Currently this machine is being assembled. Both processes should result in welds which need less repair welding or replacements, as these are automated processes, with full process control, therefore the reliability and the life span of the infrastructure will be enhanced.
To assist the development of both welding processes, finite element models have been made, that are being used to assist the choice of parameters for welding, but also the final design possibilities in the orbital friction welding machine. A lot of work has gone into finding the right material data to include in the models, and this will continue for the rest of the project duration, to further improve the model results
Exploitation and dissimination has focuess on getting the project known in the rail infrastructure community, with good results, as shown by the Exploitation Board meeting at the Innotrans Fair. The first contacts for exploitation outside the project have already started, there has been for instance a clear interest in the cooling module developed for the hot forge aluminothermic welding process, this module could also be used coupled with other welding processes.

Significant results so far:

- Vehicle-track interaction dynamic model, able to assess influences of geometry changes across the weld
- Definition of desired weld geometry across the welded region to minimise dynamic forces
- prototypes of:
- equipment able to apply controlled compressive forces to AT weld
- enhanced cooling system for AT welding
- weld finishing tool with new technology
- Design of equipment capable of orbital welding of rails, including design of clamping system and control system
- FE models for the two process have been created.
- FE model for AT process has been verified for temperature
- Exploitation Board organised at InnoTrans (rail exhibition)
- Dissimination presentation given at various industry and technical body meetings.

Final results

WRIST will :
1. Develop two innovative methods (automatic forged aluminothermic welding and orbital friction welding) for joining rails. These innovations will also deliver increased reliability, a longer lifetime of the rails and welds, combined with a reduction of the maintenance cost.
• A revolutionary methodology for hot forged AT welding will be developed, which enhances the internal integrity by modifying the cast structure. /Also reducing the the total delivery time, and ensuring process control and quality verification.
• Aa new variant of the orbital friction welding process, for welding rails will be developed. It will be demonstrated that this process is a valuable alternative for realising high-performance rail joints.
2. Facilitate an increased use of bainitic rail steel grades that possess greater resistance to the key degradation mechanism of rolling contact fatigue. Since the proposed welding techniques in WRIST have the capability to minimize the HAZ at either side of the joint, it is also expected to limit the damage to the original bainitic microstructure through tempering. The use of bainitic rails will become easier and more cost effective for rail operators.
3. Permit the achievement of lower life cycle costs for track maintenance and renewal by eliminating the source of higher dynamic forces at “cupped” or irregular geometry welds that are responsible for the more rapid loss of track geometry and necessitate expensive maintenance tamping intervention.
4. Enable an increased use of more environmental friendly joining processes, such as friction welding. This process does not require fluxes or shielding gases, produces no harmful smoke, fumes or slag, which will reduce the overall environmental impact of track construction and maintenance. The much reduced rate of degradation due to the small HAZ and the resultant longer life span of the track will also be a key contributor to lowering the carbon footprint of railway transportation.
5. Deliver environmental benefits by reducing the use of carbon fuels and gas, reduction of exposure to noise, dust and vibrations by automating and incorporating in-process monitoring of the aluminothermic process, more efficient preheating and reduction in remedial grinding to achieve the required straightness.