Deep rolling is a powerful tool to increase the fatigue life of railway axles. The application introduces compressive residual stresses into the area near the surface, which are the most effective positive influence on the fatigue behaviour and the remaining service life in the presence of a crack.
This paper investigates the remaining service life of deep rolled railway axles. Previous research studies are used as basis for this work whereas, firstly, an elaborated crack growth model for the application on railway axles applicable for common railway axle steels was developed. This model is based on the NASGRO equation considering crack closure as well as load sequence effects and local residual stress conditions. Secondly, a numerical deep rolling simulation model validated with experimental residual stress measurements to determine the introduced residual stress state and to investigate the influence of various process parameters such as deep rolling force, feed rate, friction coefficient and tool geometry on the introduced residual stress state.
In this study, the comprehensive outcome of both studies is connected in order to evaluate and compare the residual fatigue life with the presence of different deep rolling-induced in-depth residual stress distributions at the railway axles. The crack growth study involves combinations of different deep rolling parameters, load amplitudes as well as initial crack sizes and compares the residual life results. Finally, the study further leads to an evaluation of optimal deep rolling parameters in regard to the remaining service life which facilitates an elaborated fatigue design of railway axles.