Abstract
Our understanding of the mechanics of contact behaviour for interacting particles has been developed mostly assuming that surfaces are smooth. However, real particles of interest in engineering science are generally rough. While recent studies have considered the influence of roughness on the normal force–displacement relationship, surface roughness was quantified using only a single scalar measure, disregarding the topology of the surface. There are some conflicting arguments concerning the effect of roughness on the tangential or shear force–displacement relationship. In this study, optical interferometry data are used to generate the surface topology for input into a 3D finite element model. This model is used to investigate the sensitivity of the normal force–displacement response to the surface topology by considering different surfaces with similar overall roughness values. The effect of surface roughness on the tangential force–displacement relationship and the influence of loading history are also explored. The results indicate that quantifying roughness using a single value, such as the root mean square height of roughness, Sq, is insufficient to predict the effect of roughness upon stiffness. It is also shown that in the absence of interlocking, rough particle surfaces exhibit a lower frictional resistance in comparison with equivalent smooth surfaces.
Highlights
Analytical expressions for the force–displacement relationships between contacting grains are required for accurate discrete element method (DEM) simulations
In an experimental study using interparticle loading tests, Senetakis et al [5] noted that tangential stiffness might not be significantly affected by surface roughness and Cavarretta et al [3] observed a higher friction for rough contacts
The contact behaviour of rough particles was investigated here using a combined discrete finite-element approach coupled with optical interferometry
Summary
Analytical expressions for the force–displacement relationships between contacting grains are required for accurate discrete element method (DEM) simulations. The Hertz–Mindlin model, which is used in many DEM studies, assumes that the contacting particles are smooth While this model can capture key elements of contact mechanics, it is clear that surface roughness has a measurable influence on the force–displacement relationship, for normal loading and small deformation levels [2,3,4,5]. The numerical model and the effect of surface roughness on the normal and tangential force–displacement relationships are described prior to considering the effect of loading history and contact area on friction. This is followed by a comparison between analytical and numerical estimates of contact area
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