Measurement of longitudinal rail irregularities and criteria for acceptable grinding

摘要

A portable instrument has been developed with which it is possible to measure longitudinal railhead irregularities to an accuracy of about 1 micron r.m.s. in the 30-100 aM wavelength range, with slightly poorer accuracies in shorter and longer wavelength ranges. Profile data are recorded on an industry-standard laptop computer using a softwave package written for this purpose. This software also provides the means of analyzing data rapidly and routinely to show components of the profile in different wavelength ranges, and to calculate statistical quantities such as the r.m.s. amplitude which can be used to characterize corrugation severity. It is proposed that the fraction of track over which the r.m.s. amplitude of longitudinal irregularities exceeds specified limits is a useful criterion to assess grinding quality. Limits of 3, 7, 7, 45 and 100 microns should be exceeded over less than 5% of the length of ground track in the wavelength ranges 10-30 aM, 30-100 aM, 300-1000 aM and 1000-3000 aM respectively.