Eddy current test for operation-induced damaging on rails

The railway network of Deutsche Bahn AG (German Rail) is subjected to conti nuous monitoring and inspection. As the load on the network will continue t o grow, there is a need for new and improved testing techniques which, on t he one hand, guarantee the highest possible safety standard and, on the oth er hand, enable highly economical maintenance of the railway network. The development of testing methods for localisation of defective rails was initiated by an accident in the USA in 1911. As a result non-destructive te sting methods, such as ultrasonic methods, have been used for the inspectio n of installed rails since many years. Eddy current testing is still quite uncommon here. So far investigations have not been able to demonstrate this method's advantages over other techniques in the detection of operation-in duced damages. However, in on-line testing applications during the producti on of rails eddy current methods have proved very successful in the detecti on of near-surface defects. Tests were carried out to determine the suitabi lity of sensors for on-site detection of near-surface defects on installed rails. Especially the spacial and depth resolution of the instruments turne d out to be critical factors. For the first time the participating engineer s and scientists could make a quantitative assessment of damages by head ch ecks. In the future it will therefore be possible to use this method on rai l inspection trains.