Error Estimation in Wheel-Rail Normal Contact Area Measurements Using Pressure Sensitive Film

Pressure measurement films are an efficient tool to validate the shape and size of wheel-rail contact patches predicted by numerical simulations. However, accurate measurements are only possible if the alteration caused by the presence of the film between contact partners is considered. This work investigates the effect of several influential factors on the resulting deviation and presents a procedure to estimate the measurement error in wheel-rail contact.

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This monograph presents a series of research activities with the goal of determining whether pressure measurement films are a suitable tool for a quantitative assessment of the wheel-rail contact area. Firstly, the effect of influential factors such as geometry, applied load and surface roughness on the resulting imprint was thoroughly examined by means of analytically approachable case studies. This allowed a precise determination of the systematic error that alters experimental outcomes. After that, finite element representations of the measurement procedure were explored in order to characterize the measurement deviation based on mechanical principles. By virtue of the excellent reproducibility of the measurement procedure, as well as the meaningful insight obtained from finite element simulations, an empirically calibrated film model that matches experimental outcomes was developed. This was alternately interposed between wheel and rail models to estimate the measurement error originated under typical operation conditions. The results underline the marked dependence of the measurement error on surface roughness but foresee a robust and reliable use of pressure measurement films for validation of wheel-rail contact models as long as both numerical and experimental solutions represent the same reality of interest.