Similar as reported in literature for thermal loading, mechanical loading of a rough interface causes high stresses in interfacial roughness peaks and valleys.
Irregularities on the surface were broader and the roughness peaks were bigger (green arrow).
A wall is termed as hydraulically smooth if all the roughness peaks are within the laminar sublayer.
The former can be explained by the sputtering effect due to the ion bombardment, while the latter may be related to the redistribution of material into valleys by eroding surface roughness peaks and ion bombardment enhancing the surface diffusion mechanism, which occurs at high doses [7].
The onset of roughness effects occurs at a maximum peak to trough roughness height, k+t, of ∼10.
The surface roughness for peak shear stress for the aluminum alloys was achieved from grinding with the 240 grit SiC emery papers while that for the steel alloy was from grinding with the 320 grit SiC emery papers.
Three efficiency indicators based on average roughness, average peak-to-valley height and subjective part quality are then used in a case study on vibratory grinding.
In this, Seals is describing more than surface smoothness and roughness, visual peaks and valleys.
The average roughness, extrusions (peaks), and intrusions (valleys) produced by persistent slip bands (PSBs) on the surfaces of the specimens were observed and quantified for different loadings and fatigue life.
