Contact area

About: Contact area is a research topic. Over the lifetime, 12358 publications have been published within this topic receiving 256401 citations. The topic is also known as: contact patch & contact region.

Fractal Crushing of Ice and Brittle Solids

Abstract: A significant `scale effect' is observed when sea ice forces on structures are measured at field scale: the force per unit contact area is not independent of area, but decreases with increasing area Fragments of broken materials are found to have a fractal size distribution, with a fractal dimension close to 25 over a remarkably wide range of fragment size The research described in this paper brings these two observations together, and shows that they can be explained by a simple model of crushing, which incorporates the relation between fragment size and splitting force predicted by linear elastic fracture mechanics The model indicates a special role for the fractal dimension of 25, and predicts a relation between force and area, consistent with field observations

Metallic Bond-Enabled Wetting Behavior at the Liquid Ga/CuGa2 Interfaces

Abstract: Interface interaction can strongly modify contact angle, adsorption energy, interfacial tension, and composition of the contact area. In particular, the interfaces between gallium-based liquid metal (LM) and its intermetallic layer present many mysterious and peculiar wetting phenomena, which have not been fully realized up to now. Here in this study, we found that a gallium-based liquid metal droplet can quickly transform into a puddle on the CuGa2 surface through a spreading–wetting procedure. The mechanism lying behind this phenomenon can be ascribed to the formation of an intermetallic CuGa2 on Cu plate surface, which provides a stable metallic bond to induce the wetting behavior. For a quantitative evaluation of the interface force, a metallic bond-enabled wetting model is established on the basis of the density functional theory. The first-principles density functional calculations are then performed to examine the work function, density of states, and adsorption energy. The predicted results show t...

Linking energy loss in soft adhesion to surface roughness

Abstract: A mechanistic understanding of adhesion in soft materials is critical in the fields of transportation (tires, gaskets, and seals), biomaterials, microcontact printing, and soft robotics. Measurements have long demonstrated that the apparent work of adhesion coming into contact is consistently lower than the intrinsic work of adhesion for the materials, and that there is adhesion hysteresis during separation, commonly explained by viscoelastic dissipation. Still lacking is a quantitative experimentally validated link between adhesion and measured topography. Here, we used in situ measurements of contact size to investigate the adhesion behavior of soft elastic polydimethylsiloxane hemispheres (modulus ranging from 0.7 to 10 MPa) on 4 different polycrystalline diamond substrates with topography characterized across 8 orders of magnitude, including down to the angstrom scale. The results show that the reduction in apparent work of adhesion is equal to the energy required to achieve conformal contact. Further, the energy loss during contact and removal is equal to the product of the intrinsic work of adhesion and the true contact area. These findings provide a simple mechanism to quantitatively link the widely observed adhesion hysteresis to roughness rather than viscoelastic dissipation.