First project route:
Current design standards are only taking into account a constant factor that depends on the static load used for all types of applications (from high speed trains to freight wagon applications). A beam calculation is performed on critical sections previously defined by the designer. Stress values are compared to permissible limits (including safety criteria based on experience). These relate to maintenance practices but have no real link with the main defects observed in service.
The fatigue limits are established for a limited number of grades in close relation with field experience. In addition, existing standards specify the criteria to qualify steel grades and their testing but do not allow the determination of fatigue limits, especially for new steel grades applied for high speed train axles. Therefore, current standards do not leave room for innovation to propose improved or indeed breakthrough solutions.
The EURAXLES project plans to improve the definition of loads applied on structures for the freight and conventional main train categories.
The collective load will be used in Finite Element Analysis models, which provide more accurate results for complex structures such as power axles with many radius transitions. Multi-axial fatigue criteria will be used to validate a design (including material properties) with new steel grades and coating solutions used to protect the axle against corrosion.
A probabilistic treatment of data will then allow a comparison between stresses and the strength of the structure, which will help determining the safety margin of the system. As a result, EURAXLES allows the development of innovative solutions based on risk analysis and not only on field experience.
Second project route:
The fatigue resistance of railway axles depends on the surface conditions. EURAXLES plans to advance beyond the state-of-the-art by resolving the problems associated with existing surface coating methods (corrosion, damage) through improved adhesion and new innovative coating and treatment processes while considering the real service conditions and environmental requirements*. These developments will lead to improved fatigue resistance of railway axles currently undermined by existing paint adhesion problems. No previous or ongoing research or standardisation activities are known in this area.
In view of their experience, axle producers will analyse the current EN standard, EN 13261, and determine its limitations in terms of testing and validation of protective coatings. Particular attention will be given to the operating conditions of wheelsets in service, and where necessary, alternative test methods will be proposed.
Third project route:
Wheelsets are the most critical component for safety; for this reason they are periodically inspected to guarantee their structural integrity to prevent failure and vehicle accidents. EURAXLES plans to improve the currently used ultrasonic techniques for inspecting the complete volume of the axle, thus reducing the risk of human error and increasing the precision and optimising the periodicity of the inspection. The fatigue testing shall make use of readily available cracked axles.
In addition, promising innovative techniques that might allow accurate inspection (including corrosion detection in the hidden spot of the axle) without the train stopping for several days will also be investigated.
The EURAXLES consortium comprises the main actors in the rail sector, all of whom have a strong desire to promote railway transportation as the safest land transport mode by putting together the necessary critical mass to overcome the existing knowledge gaps. The EURAXLES partners will lay down the knowledge foundations necessary to enable the development of innovative safe solutions for railway wheelsets with improved reliability in a cost effective way.
EURAXLES’ project objectives are:
1. to commonly agree at European level on an innovative axle design approach, including a risk analysis method which, similar to limit state analysis, could offer a simple design route by combining loads with difference occurrences including loading specificity of vehicles and service conditions together with the axles resistances (fatigue limit, fatigue life, fatigue under corroded conditions due to coating failure), including new materials and methods in order to predict the ‘failure probability’.
2. to develop (i) improved axle protection against corrosion, including ex post facto protection of already corroded axles; (ii) improved adhesion of coatings with a study of the roughness influence (adhesion and fatigue behaviour); and (iii) new, innovative coating solutions, developed in public-private partnership between companies and universities. The new solutions have also to fulfil environmental requirements to avoid or limit VOC emissions.
3. to evaluate new/improved Non Destructive Testing inspection methods that allow the in-service inspection of axles in order to guarantee safe service conditions with a low impact on the vehicle availability. This work will mostly be based on a benchmark of existing and/or innovative solutions.
RAMS and LCC analyses undertaken in this research project will allow a cost benefit comparison of the proposed solutions for an optimised market uptake.
With the achievement of its objectives, EURAXLES will allow reliable decisions to be made on axle maintenance and critical safety service intervals. This will also have positive impacts on the environment and on the European industries’ competitiveness as highlighted in the ERRAC SSA 2020: “The safety of the European railways is of prime importance not just in terms of the loss of life when a major rail accident causes, but also in terms of the operational cost of degraded mode after accidents and incidents even when no one is injured which undermines the business case for railways”.
Even though axle failures mainly concern freight wagons, the EURAXLES objectives are extended also to passenger trains and also the end-users like European passengers will finally benefit of a more reliable and safer mode of transport.
*Current protection systems involve solvent-based paint systems, which present a high VOC level released in the environment.