Investigation and Assessment on Amplitude Parameters of Surface Roughness Based on Profile Method
There are many methods and parameters to assessing surface roughness of machined surface of component.However,there are some problems such as single and improper selection of evaluation parameters in parts design,processing and measurement.Therefore,the amplitude parameters of surface roughness such as Ra,Rq,Rsk and Rku based on profile method are paid more attention to be analyzed.This paper presents that the amplitude parameters represent the 1st~4th or-der origin moments of the profile ordinate value respectively.Meanwhile,they can stand for mean value,standard deviation,skewness and kurtosis of vertical coordinate value respectively in statistics principle.The roughness profile of the joint sur-face and mating surface of ordinary precision structural parts are approximately symmetrical.So it is more reasonable to e-valuate surface roughness of these surfaces in the way of Ra parameter.Furthermore,the roughness profile of guide surface,sealing surface,friction surface and superfinished surface based on functional requirements are significantly asymmetrical.Thus,it is more reasonable to evaluate surface roughness of these surfaces in the combination method of Rq and Rsk parame-ters.Finally,the surface roughness measurement examples of the cylinder liner of the internal combustion engine,the guide rail of the numerical control machine tool and the working surface of the numerical control tool shank are carried out,which results verifies the theoretical analysis.The investigation provides a reference for the design,measurement,analysis and evaluation of the surface roughness of the parts.