Fatigue crack growth of rails for railways

Fatigue crack growth rates of rails from four European rail manufacturers are presented. The tests performed, on which the present paper is based, are part of the contribution to a project on the fatigue crack growth rate qualifying criteria of rails for railways-SMT4-CT98-2240-partfunded by the European Union. Six different laboratories were involved in measuring the scatter in fatigue crack growth rates. The tests were carried out under a stress ratio of 0.5, with test temperature and relative humidity recorded but not controlled beyond the ambient laboratory condition. The cyclic test frequency was either 10 or 15 Hz. The crack length was measured manually (optical microscope) which requires interruptions to the test overnight. Statistical analysis revealed that interruptions to tests may cause interference with the results. The data were analysed by three procedures: formal methods used were the secant method and the seven-point incremental polynomial technique; in addition, statistical analysis of a more investigative type using running regressions was utilized. It was found that there was no significant difference between the crack growth rate in samples from four different manufacturers.