COMPREHENSIVE STUDY OF PARAMETERS FOR CHARACTERIZING 3-DIMENSIONAL SURFACE-TOPOGRAPHY .2. STATISTICAL PROPERTIES OF PARAMETER VARIATION

The main objective of the paper is to understand and interpret statistical properties of parameter variation on practical engineering surfaces where surface features may be involved and ergodicity or stationarity or non-stationarity is applied. The understanding of the causes, the mechanism and the statistical properties of parameter variation of practical engineering surfaces is essential for developing an effective approach to describe characteristics and functional performance of three-dimensional surface topography. This paper treats parameters as random variables, and simulates a practical engineering surface with a random process. The concepts of stationarity and ergodicity of engineering surfaces are presented and quantitative analysis of parameter variation for theoretically modelled non-stationary surfaces is carried out. In addition statistical properties of parameter variation from three kinds of ''typical'' engineering surfaces are discussed, and the influences of non-stationarity, surface features and correlation of sampled profiles on the properties are specified.