Abstract: In view of the complex surface properties of 30CrMnSiA dimple fracture, scanning white-light interferometry is used to measure microscopic topography. The Linnik structure is adopted in the system and the 3D image of dimple fracture is rebuilt by spatial frequency analysis. Longitudinal accuracy is better than 5 nm for a scan range of 120 µm in the experiment. The frequency-domain analysis approach exhibits strong abilities of phase extraction and noise suppression. 3D-Motif method for assessing dimple fracture surface is studied, six parameters including depth, length, width, area, direction angle and anisotropy rate are defined, and combination algorithm based on area and depth threshold is proposed. Considering the anisotropy of dimple microtopography, the definition for surface micro-roughness based on aspect ratio is modified. The obtained three-dimensional surface topography is partitioned to extract both single dimple character and statistical parameters, in which the micro-roughness of the fracture surface is tested to be around 0.15～0.70, thereby providing the objective basis for quantitative study on the mechanism of fracture.

Key words: 3D-motif, Dimple fracture, Scanning white-light interferometry