background: friction is usually encountered during sliding technique for orthodontic space closure. this study aims to investigate the effect of fluoride on frictional resistance between stainless steel orthodontic brackets and steel and niti arch wires. materials and methods: a total of 144 standard 022 stainless steel brackets were used in this experimental study. 0.016 and 0.019 × 0.025 inch...

oint friction is one of the major limitations in performing high J precision manipulation tasks. It affects both static and dynamic performances, and may cause instability when coupled to position or force feedback control. Thus, compensating for joint friction has been one of the main research issues in robot design and control over the years. The aim of this paper is to show how friction comp...

We use the existing data of force-extension experiments on F-actin molecules tied into knots to compute a value of 0.15 for the static friction coefficient for contact between different parts of the same molecule with itself. This estimate for protein-protein friction is relevant for the stabilization of the 273 known proteins with knots, one percent of the structures deposited in the Protein D...

The transmission of stress is analysed for static periodic arrays of rigid grains, with perfect and zero friction. For minimal coordination number (which is sensitive to friction , sphericity and dimensionality), the stress distribution is soluble without reference to the corresponding displacement fields. In non-degenerate cases, the constitutive equations are found to be simple linear in the ...

The porosity of uniaxially compacted cohesive powders depends on the applied stress (including gravity). The case, where these stresses are weak, is considered. The compaction results in a porosity which is a function of sliding, rolling and torsion friction. By contact dynamics simulations it is shown that the influences of contact torques (static rolling and torsion friction) on the porosity ...

We study, using fluorescence correlation spectroscopy, translational diffusion in molecularly thin liquids confined within a surface forces apparatus. The diffusion coefficient decreases exponentially from the edges towards the center of the Hertzian contact and further suggests the presence of a small number of distinct diffusion processes. This holds alike a crystallizable fluid (OMCTS) and a...

The earthquakelike model with a continuous distribution of static thresholds is used to describe the properties of solid friction. The evolution of the model is reduced to a master equation which can be solved analytically. This approach naturally describes stick-slip and smooth-sliding regimes of tribological systems within a framework which separates the calculation of the friction force from...

The static friction coefficient between two materials is considered to be a material constant. We present experiments demonstrating that the ratio of shear to normal force needed to move contacting bodies can, instead, vary systematically with controllable changes in the external loading configuration. Large variations in both the friction coefficient and consequent stress drop are tightly link...

A number of problems of dynamic deformation in the presence of moving contact surfaces are considered. A grid characteristic method using a two-dimensional irregular triangular grid and a hybrid scheme with 1-2 order of approximation is adapted. An algorithm for calculating the force of friction and the force of static friction is proposed. The numerical solution to wheel rolling and shear wave...

2 Linear response theory for collective motion 2.1 Intrinsic versus collective response 2.2 Collisional damping of nucleonic motion 2.3 The e ective coupling constant 2.4 Strength distributions 2.5 Transport coe cients and their dependence on T 2.5.1 Friction coe cients in zero frequency limit 2.6 The role of symmetries 2.6.1 Quasi-static properties and the "heat pole" 2.6.2 Consequences for fr...