Analysis and determination of UT POD curves for railway axles

The increasing demand for the reliability assessment of railways components, especially for high speed trains applications, leads to a new definition of safety factor that can be determined by a “defect tolerant” approach and by the evaluation of “safe life” inspection intervals as a function of materials characteristics, propagation models and NDT inspections. The present paper deals with the determination of inspection intervals of railways axles, considering the special application of a typical alloyed steel grade for high speed trains, hollow axles and a specially developed UT device for in-service inspection. Initially, the POD curve of such device has been derived by means of dedicated experimental UT measurements. This curve has then been used together with the crack propagation behaviour of 30NiCrMoV12 steel in order to define inspection intervals of high speed railway axles.