OBJECTIVES To investigate the static frictional resistance at the bracket/archwire interface in two recently introduced bracket systems and compare them to conventional ceramic and conventional metal bracket systems. Three variables were considered including the bracket system, archwire type and archwire angulation. MATERIAL AND METHODS Four bracket systems were tested in vitro: Self ligating...

Over the past decade, many computational studies have explored the mechanics of normal indentation. Quantitative relationships have been well established between the load–displacement hysteresis response and material properties. By contrast, very few studies have investigated broad quantitative aspects of the effects of material properties, especially plastic deformation characteristics, on the...

The rolling/sliding in the presence of friction of a vibrating elastic body on an elastic substrate is studied. It is shown that the longitudinal components of the velocity of the center of mass of the body and of the resultant frictional force are not affected by the vibration process. However, the normal vibration of the body influences the slip velocities and the distribution of frictional f...

Replacing the Newtonian coupling G by −iG, the Schrödinger—Newton equation becomes “frictional”. Instead of the reversible Schrödinger—Newton equation, we advocate its frictional version to generate the set of pointer states for macroscopic quantum bodies.

C60-terminated self-assembled monolayers (SAMs) were generated on the surface of Au(111) by the adsorption of unsymmetrical disul®des having saturated hydrocarbon backbone structures comprised of six (C-6) and eleven (C-11) carbon atoms. The formation of oriented monolayer ®lms from these adsorbates was con®rmed by ellipsometric thickness and contact angle measurements. The morphologies and fri...

Based on the assumption that fault slip dominates in stress relaxation brittle crust, Coulomb theory allows for crustal estimation with an empirical frictional coefficient. However, natural variability of friction and uncertainty exist Earth's crust. To address extent to which heterogeneous slips influence its evolution, we establish a quasi-static, 2D model represent fractured rock mass. The c...

Recent experiments on microscopic graphite mesas demonstrate reproducible high-speed microscale superlubricity, even under ambient conditions. Here, we explore the same phenomenon on the nanoscale, by studying a graphene flake sliding on a graphite substrate, using molecular dynamics. We show that superlubricity is punctuated by high-friction transients as the flake rotates through successive c...

The interplay between local mechanical strain energy and lateral frictional forces determines the shape of carbon nanotubes on substrates. In turn, because of its nanometer-size diameter, the shape of a carbon nanotube strongly influences its local electronic, chemical, and mechanical properties. Few, if any, methods exist for resolving the strain energy and static frictional forces along the l...

The most general frictional motion in nature involves bimaterial interfaces, when contacting bodies possess different elastic properties. Frictional motion occurs when the contacts composing the interface separating these bodies detach via propagating rupture fronts. Coupling between slip and normal stress variations is unique to bimaterial interfaces. Here we use high speed simultaneous measur...