A systems approach to evaluating rail life

Corus Rail Technologies (CRT) has undertaken a major project involving track studies of Rolling Contact Fatigue (RCF), with support from Manchester Metropolitan University (MMU). The work takes a systems approach and involves the development and application of a suite of numerical models used to investigate the in-service conditions of track components with particular emphasis on RCF. The suite of models, called the Track System Model (TSM), comprises of vehicle dynamics models, developed by MMU, a Global Track model and a rail-wheel Contact model, developed by CRT. The modelling is being complemented through the monitoring of a number of RCF affected sites on the UK network to provide essential empirical data. A total of seven vehicle models have been developed using ADAMS/Rail, including two locomotives, two DMUs, two passenger coaches, and a freight wagon. Vehicle simulations were conducted for a range of UK sites and provided results such as wheel-rail contact forces and contact patch positions. The vehicle models have been validated using track measurements. The results were then used as inputs for the CRT Global Track and Contact models. The Global Track model is a finite element (FE) model that represents a length of railway track and includes the rails, sleepers and ballast. Forces from the vehicle simulations were applied to the Global model in order to predict the bending stresses in the rail head. This was conducted for a number of vehicles at seven sites and the predicted values showed good comparison with track measurements. The Contact FE model is a 3 dimensional (3D) representation of a wheel section rolling on a short length of rail. Wheel loads calculated from the vehicle dynamics simulations were applied to the contact model in order to predict surface and subsurface stresses, including directional and shear, in the rail head. Subsurface stress distribution is of primary importance for understanding the development of RCF and crack growth. The TSM successfully integrates the vehicle and track aspects of the railway system and provides an accurate method of predicting stresses in rails. When used in conjunction with the practical understanding of RCF, through site monitoring, it will enable the development of analytical fatigue life models that can be used by the track engineer to support future decision making for an optimum rail grinding strategy and rail renewal programme.