Variable amplitude crack growth in railway axles: influence on inspection intervals

Railway axles are designed for infinite life, but occasional failures have been and are observed in service. The failures, which are usually due to fatigue crack propagation, are addressed adopting the concept of “damage tolerance” in order to determine the inspection intervals of the axle depending on the NDT method. The issue open to discussion is the choice of the correct algorithm for simulating crack growth at R=-1 at variable amplitude loading especially when considering typical steels such as A1N and A4T. The aim of the present research, is to discuss the application of crack growth algorithms to the propagation of cracks in railway axles under service conditions. More specifically, the present paper shows some of the results recently obtained at Politecnico di Milano in the frame of the WIDEM European Project on integrity and design of railway wheel-sets.