Multiscale surface texture and fractal analysis of straight bevel gears finished by PECH and PECF process

The present work was conducted to provide insights for an in-depth understanding of the straight bevel gears finished by pulsed-electrochemical-honing (PECH) and pulsed-electrochemical-finishing (PECF), using multi-scale surface texture and fractal analysis in order to give manufacturers a competitive edge when improving their tools. Unfinished bevel gears and bevel gears finished by PECF and PECH were analyzed on their surface texture characteristics and material properties. Surface characteristics of 20MnCr5 alloy steel gears were evaluated by computing four locations on regions of each sample. Field emission scanning electron microscopy (FESEM) was applied for surface material characterization. It was found that it can be discriminated between the PECF and PECH-finished bevel gears surface regions of samples and unfinished samples, using area-scale analysis and surface texture characteristics. The surface micro-morphology results can be applied in studies about improving the lifetime of tools and for mathematical modeling of lubrication processes between tool and workpiece

Fractal Analysis of AFM Images of the Surface of Bowman’s Membrane of the Human Cornea

The objective of this study is to further investigate the ultrastructural details of the surface of Bowman's membrane of the human cornea, using atomic force microscopy (AFM) images. One representative image acquired of Bowman's membrane of a human cornea was investigated. The three-dimensional (3-D) surface of the sample was imaged using AFM in contact mode, while the sample was completely submerged in optisol solution. Height and deflection images were acquired at multiple scan lengths using the MFP-3D AFM system software (Asylum Research, Santa Barbara, CA), based in IGOR Pro (WaveMetrics, Lake Oswego, OR). A novel approach, based on computational algorithms for fractal analysis of surfaces applied for AFM data, was utilized to analyze the surface structure. The surfaces revealed a fractal structure at the nanometer scale. The fractal dimension, D, provided quantitative values that characterize the scale properties of surface geometry. Detailed characterization of the surface topography was obtained using statistical parameters, in accordance with ISO 25178-2: 2012. Results obtained by fractal analysis confirm the relationship between the value of the fractal dimension and the statistical surface roughness parameters. The surface structure of Bowman's membrane of the human cornea is complex. The analyzed AFM images confirm a fractal nature of the surface, which is not taken into account by classical surface statistical parameters. Surface fractal dimension could be useful in ophthalmology to quantify corneal architectural changes associated with different disease states to further our understanding of disease evolution