DESCRIBING DISTRIBUTION SHAPE - R(K) AND CENTRAL MOMENT APPROACHES COMPARED

An investigation is reported into characterisation techniques for mult i-stratum bearing surfaces such as those produced by plateau-honing. E xperiments have been undertaken to determine whether the information p resented by the recently introduced DIN 4776 R(k) parameters can be ad equately inferred from the existing central moment parameters of the h eight distribution; R(q), R(sk) and R(ku). Measured values of these ce ntral moment parameters are used to fit model continuous distribution curves using the Pearson system of distributions. The bearing ratio re presentations of these curves are analysed to derive their DIN 4776 R( k) parameters. These simulated R(k) parameters are then compared with those obtained by direct measurement from the profile. It is shown tha t for surfaces with moderate degrees of skewness this modelling proced ure allows the R(k) parameters to be inferred with reasonable accuracy . For highly skewed surfaces, however, the continuous distributions fi tted by Pearson techniques cannot adequately model the upper portions of the profile height distribution and so R(pk) values cannot be estim ated at all and the accuracy with which the other DIN 4776 parameters can be inferred is poorer.