Railway axle design – to be based on fatigue initiation or crack propagation?

Design and standardization of railway axles from the mechanical-strength point of view is discussed and a brief state-of-the-art survey is given. Traditional fatigue design with the ‘safe-life’ approach and a design with the more recent crack-propagation/defect-tolerance approach are described and compared. Axles of a standard freight wheelset (22.5 tonne axle load) and of two heavy haul wheelsets (25 and 31 tonne axle loads) are used for illustration. From the numerical results it is concluded that a crack-propagation/defect-tolerance approach could be a useful complement to the traditional fatigue design method. A result of particular interest is the fairly strong influence of stresses from the press-/shrink-fitting on the residual life of the axles