Volume 5, Issue 7 (July 2008)
Analysis of Crack Growth at R=−1 Under Variable Amplitude Loading on a Steel for Railway Axles
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 typically positioned at the press fits which correspond to the wheels, gears, brakes, or they appear at the axle body close to the notches and transitions. The way to addressing this problem is to adopt 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 mild steels such as A1N. The aim of the present research is to discuss the application of state-of-the-art algorithms to estimate the effect of block loading at R=−1 (derived from real load spectra experienced by the axle) upon constant crack growth rate. More specifically the current research addresses: (i) crack growth experiments at R=−1 under constant amplitude loading on two novel types of small-scale specimens; (ii) crack growth experiments under block loading on small-scale specimens; and (iii) the prediction of the experimental evidences by well-known and wide-spread analytical tools.