THE EFFECTS OF TRANSVERSE PROFILE ON THE EXCITATION OF WHEEL/RAIL NOISE

At the Fifth International Workshop on Railway Noise in 1995, two papers reported apparently conflicting results relating to the effects of transverse profiles on noise. Remington and Webb reported theoretical results showing that conforming profiles could lead to a reduction in noise generation. Dings and Dittrich reported experimental results which showed apparently inconsistent roughness-to-noise behaviour between wheels with different braking systems. They suggested that these results could be explained by an increase in noise for a given roughness level when the profiles are conforming. This paper describes a new analytical investigation of the effects of transverse profiles which aims to resolve this conflict. It is based on new very detailed roughness measurements. The data were analyzed first using a discrete point reacting spring model (DPRS). The transverse profiles of the wheel and rail were replaced with circular transverse profiles of different radii of curvature. It was found that the average roughness across the contact zone decreased as the width of this zone was increased, but that these reductions were only modest. The DPRS predictions showed little or no decrease in interaction force with increasingly conforming profiles. The TWINS model has been used to perform calculations which confirmed that, for the roughness data examined, little noise reduction benefit could be expected from a conforming wheel, and in some circumstances it could lead to an increase in noise. TWINS was also used to study the effects of the actual transverse profiles in an attempt to explain more fully the measured results. Some useful conclusions are drawn, but a full explanation of the measured results has not yet been obtained as all three types of braking system lead to some degree of conforming profiles.