Temperatures at railway tread braking – A parametric study

Paper in proceeding, 2007

A thermal model of railway tread braking has previously been developed for use in calculations of wheel and brake block temperatures. Block(s) and wheel are coupled via a contact interface that controls the heat generation and also the heat partitioning between block and wheel. Heat transfer from the rolling wheel into the rail is accounted for. The thermal model was calibrated using results from both standard brake rig tests and tests when a “rail-wheel” was introduced in the rig. Furthermore, the model was successfully calibrated using results from field studies. In the present work, the thermal model is utilised to study temperatures and partitioning of heating power during different braking set-ups and braking loads. First, the influences from geometrical changes are studied, with parameters such as wheel design, wheel wear and block wear. Also the effect of brake block configuration is studied. Second, the influence from brake block material is considered. Third, the influences from braking parameters are studied. Gradient braking on mountain descents is simulated but also the related case of brake system malfunctioning. Stop braking is studied. Fourth, the importance of rail chill is investigated with respect to shape and size of the contact patch between wheel and rail. A general result from the present parametric study is that rail chill is important for a useful simulation of wheel temperatures and heat partitioning at drag braking. Rail chill consumes a considerable part of the total heat at drag braking and it becomes increasingly important as the tread temperature rises. For example, at the end of a brake cycle at 30 kW per wheel for 30 min with composition brake blocks using a 920 mm wheel, 21 % of the total heat enters the rail.