Effects of surface structure deformation on static friction at fractal interfaces

Abstract

The evolution of fractal surface structures with flattening of asperities was investigated using isotropically roughened aluminium surfaces loaded in compression. It was found that asperity amplitude, mean roughness and fractal dimension decrease through increased compressive stress and number of loading events. Of the samples tested, surfaces subjected to an increased number of loading events exhibited the most significant surface deformation and were observed to exhibit higher levels of static friction at an interface with a single-crystal flat quartz substrate. This suggests that the frequency of grain reorganisation events in geomaterials plays an important role in the development of intergranular friction. Fractal surfaces were numerically modelled using WeierstrassMandelbrot-based functions. From the study of frictional interactions with rigid flat opposing surfaces it was apparent that the effect of surface fractal dimension is more significant with increasing dominance of adhesive mechanisms.

The influence of particle surface roughness on elastic stiffness and dynamic response

“…8) and δ1 = 0 (also NT1 = 0 & δT1 = 0) reduces the proposed model to the Cavarretta model and when Sq = 0, the model is identical to Hertzian theory. The model idealises the real physical system: it does not consider yielding, squashing or vibration of asperities or the change in the inter-particle friction due to the plastic compression of asperities (Hanaor et al, 2013).…”

Static friction between rigid fractal surfaces

“…Frictional phenomena at material interfaces are known to be governed both by the atomic interactions occurring at bulk and surface regions in materials and by the multiscale surface structures at regions of apparent contact [11,12]. A linear relationship between normal load and frictional force, captured by the friction coefficient μ, following Amonton's law, is sufficient for the description of most macroscopically observed systems.…”

“…The original idea of Archard was later extended by several authors (Yang and Komvopoulus [31], Ciavarella et al [32], and Gao and Bower [33]), who introduced fractal models for the statistical description of the self-affinity of roughness. These models focused on the fractal properties of the contact areas and the number of contact spots, while the connection between surface roughness and actual friction has been explored only recently [12].…”

Editorial

“…These papers are given free access to all, together with the best paper of the year. In 2013, papers by Festugato et al (2013), Hanaor et al (2013), Andò et al (2013) and Panaguia et al (2013) were selected. The Telford Premium prize is awarded to the best paper of the year and it was decided to select the paper by Panaguia et al Warmest congratulations to the authors of these excellent papers!…”