06 TRACK SYSTEMSSUPPLEMENT George Kotsikos


RAILECT Project Manager of NewRail – the Centre for Railway Research at Newcastle University


Tamara Colombier


Senior Project Leader in the Non-Destructive Testing Technology Group at TWI and RAILECT Project Co-ordinator


Angélique Raude


Principal Project Leader in the Non-Destructive Testing Technology Group at TWI


RAILECT – DEVELOPMENT OF AN ULTRASONIC TECHNIQUE, SENSORS AND SYSTEMS FOR THE


Volumetric examination of aluminothermic rail welds


There are millions of aluminothermic (AT) welds in-service in Europe’s rail network as the technique is a highly mobile and cost effective joining method that produces a continuous rail track that has vastly improved the travel speed and quality of ride for passenger trains. It is however, a complex welding process which involves a number of steps that can be influenced by the welder’s skills and/or the environmental conditions, which can result in poorer weld performance and the creation of defects within the weld.


Flaws may develop during and shortly after welding and can lead to early failure of a rail that may result in train derailment and disruption to train services, as well as increase costs to the rail network, train operating companies and maintenance operators. An estimated 300,000 to 400,000 new AT welds are made annually throughout Europe. Although weld joint failures due to weld defects are low, they


still account for 20% of all rail failures totalling several hundred weld failures annually. Over the past few years, rail safety has


been the subject of high concern not only due to the increase of high-speed tracks within the European network, but also due to the ageing of the tracks, thus leading to higher frequency of maintenance and inspection operations. To date, a few techniques of inspection have been


adopted with limited success to control the quality of AT welds. Radiographic inspection is sometimes carried out but it is not very common and most of the time only visual inspection is performed. Although visual inspection is a relatively quick and simple technique to use on track, it does not permit the volumetric assess - ment of the weld, which is a major drawback. The conventional ultrasonic inspection tech -


nique is also used but the inspection stand ard requires many probes and scans to be performed because of the complex geometry of the rail profile. In addition, since the welds are made by a casting process, they can be more difficult to inspect than joints made by any other welding processes. This makes ultrasonic inspection both time consuming and expensive.


FIGURE 1 Aluminothermic welding of rail (left and middle) and fractured weld (right)


European Railway Review Volume 18, Issue 2, 2012


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