The dry frictional contact between two solid surfaces is well known to obey Coulomb friction laws. In particular, the static friction force resisting the relative lateral (tangential) motion of solid surfaces, initially at rest, is known to be proportional to the normal force and independent of the area of the macroscopic surfaces in contact. Experimentally, the static friction force has been o...

Sliding parts in nanosystems such as nanoelectromechanical systems and nanomotors increasingly involve large speeds, and rotations as well as translations of the moving surfaces; yet, the physics of high-speed nanoscale friction is so far unexplored. Here, by simulating the motion of drifting and of kicked Au clusters on graphite--a workhorse system of experimental relevance--we demonstrate and...

In this paper, efficient algorithms for contact problems with Tresca and Coulomb friction in three dimensions are presented and analyzed. The numerical approximation is based on mortar methods for nonconforming meshes with dual Lagrange multipliers. Using a nonsmooth complementarity function for the three-dimensional friction conditions, a primal-dual active set algorithm is derived. The method...

Active valves are most effective tools to control gas flow in compressors if fast transitions between the open mode and closed mode are needed. Unfortunately, an accurate model including several nonlinear effects and in particular the resistance and gas flow forces is not available, and this prevents the use of standard model based approaches for time optimal control. However, the repetitive na...

introduction: the purpose of this study was to compare the accuracy of the torque wrenches used in different dental implant systems. methods: we evaluated 42 torque wrenches used in different dental clinics in mashhad, iran, using a digital torque meter (mark 10). high (25, 30 and 35 n·cm) and low (15 n·cm) levels of torque were examined. ten tests were performed on each wrench, and the mean va...

A discrete-time sliding mode control design for a ball-screw driven positioning table is presented. The basic feature of this design is that high speed and high positioning accuracy can be met despite of the fact that the controlled process suffers from friction and mechanical flexibility. Disturbance rejection, in the form of friction compensation and vibration suppression, is the main focus o...