SCRATCHING SURFACES IN ROUGHNESS MEASUREMENTS

S. Z. Zahwi, A. M. Mekawi

Abstract

The calibration of the stylus type surface texture measuring instruments is usually carried out using a precision reference specimen of regular or random pattern of irregularities. These precision specimens are produced with hardened surfaces in order to minimize the scratching effect of the stylus on their certified values. The continual tracing on these surfaces is expected to deteriorate their quality. An experimental investigation on one of these specimens having a sinusoidal pattern of irregularity has been carried out. The specimen was traced several times on exactly the same position. Up to 350 traces were taken. Form each trace a calibration constant for the measuring instrument was computed. Sets of three consecutive traces were taken and the average calibration constants obtained form each set was computed. The behavior of the results was studied, where it has been found that the mean values of the calibration constants continually decrease. After tracing the specimen for about 250 times a loss of more than 6% of its original value was obtained. The plots of the results as well as photographs of the scratches, taken using the Scanning Electron Microscope (SEM), are given.

Keywords

instruments, measurements, roughness, scratching, stylus

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IMEKO-WC-2000-TC14-P411.pdf

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IMEKO TC

TC14 - Measurement of Geometrical Quantities

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