“Safe life” inspection intervals of railway axles: comparison of crack growth properties of different steel grades

the present paper deals with a defect tolerant approach and the definition of safe life inspection intervals of railway axles, considering the application of two typical steel grades. The first part is dedicated to the comparison of the mechanical behaviour of three steel grades: an European carbon steel grade, namely A1N according to UIC 811, an American carbon steel grade, according to AAR M101 specifications, and an high strength steel grade according to Italian UNI 6787 specification. For each material, an advanced mechanical characterisation is proposed, taking into account also the influence of temperatures of typical in service conditions. In the second part of the paper, an algorithm for the assessment of crack propagation curves, based on a widely used fatigue crack growth software is presented. A comparison of safe life intervals inspection for the considered materials is proposed in the final part showing that a better knowledge of fracture mechanics properties in all the typical temperature range can open new perspectives in reducing TLCC of the wheelsets both for European and North American applications.