Damage tolerance of railway axles

Failure of railway axles has been the problem which gave origin to the studies about 'fatigue'. The modern approach to the structural integrity of these safety components is to complement the traditional designwith a 'damage toleranc' analysis.

A Special Issue just appeared onto Eng. Fracture Mechanics presents some of the most recent research.

This special issue is the result of a ESIS-TC24 meeting held at Politecnico di Milano, Dipartimento di Meccanica, on 13-14th
October 2008. The meeting hosted 70 attendees (most of them from the industry) and 16 technical presentations which gave
a precise overview of the research projects that, at the time, were closing their activities (WIDEM, DEUFRAKO, UK Axle) and
of the approaches adopted in some countries. Some of the presentations were then selected for the inclusion in this special issue, which presents some important new results in different topics related to the structural integrity assessment of railway axles (sensitivity analysis, load spectra, multiaxiality, crack growth rates of the axle steels, crack growth in presence of fretting).

I would like to especially draw the attention to some important new results that had been commonly found by the different projects, that found a support in the discussion at the TC24 meeting:
- the validation of simulated load spectra by means of an extensive campaign of experimental measurements;
- the presence of a significant ‘scale effect' which makes crack growth in full-scale specimens much slower than the predictions
obtained in conventional fracture small scale specimens;
- different SIF solutions that have been compared and condensed.

The ‘emersion' of these important results acknowledges once again the need of exchanging and comparing the approaches
in order to find new and common solutions to improve the know-how. Details of ESIS-TC24 activity can be found at: TC24.

The presence of the 'scale effect' in crack properties is espieacially challenging: I hope that some Imechanica readers can suggest some interesting comments.