OBJECTIVE The glycoprotein lubricin (encoded by the gene Prg4) is secreted by surface chondrocytes and synovial cells, and has been shown to reduce friction in vitro. In contrast to man-made bearings, mammalian diarthrodial joints must endogenously produce friction-reducing agents. This study was undertaken to investigate whether friction is associated with wear. METHODS The lubricating abili...

During underground nuclear tests, rocks may fail by plastic yielding, which limits shear strength, or by tensile fracture, wherever maximum principal stress exceeds tensile strength. A third mode of failure exists due to friction along closed fractured surfaces. There, friction affects slipping and can thus limit stress. In this paper, we study the effect of friction on the simulated dynamic re...

A new dynamic friction model for modeling of elliptical vibration assisted turning (EVAT) was developed in this research. The periodic change of the friction force direction is known to be one of the most important causes of this phenomenon. In modeling of machining processes (including the EVAT process), static Coulomb friction model was employed by most of the researchers. Because of the peri...

Based on distributions theory to continuous time systems with friction using the this paper presents a batch on-line method for the parameter identification of the modified LuGre friction model. Mainly it applies the results of the identification procedures based on distributions theory to continuous time systems with friction. There are defined the so called generalized friction dynamic system...

We studied adjustments of digit forces to changes in the friction. The subjects held a handle statically in a three-digit grasp. The friction under each digit was either high or low, resulting in eight three-element friction sets (such grasps were coined the grasps with complex friction pattern). The total load was also manipulated. It was found that digit forces were adjusted not only to the s...

The tribological properties of two-dimensional (2D) atomic layers are quite different from three-dimensional continuum materials because of the unique mechanical responses of 2D layers. It is known that friction on graphene shows a remarkable decreasing behavior as the number of layers increases, which is caused by the puckering effect. On other graphene derivatives, such as graphene oxide (GO)...

In rehabilitation training, high-fidelity simulation environments are needed for reproducing the effects of slippery surfaces, in which potential balance failure conditions can be reproduced on demand. Motivated by these requirements, this article considers the design of variable-friction devices for use in the context of human walking on surfaces in which the coefficient of friction can be con...

In this paper, the tracking problem for robot manipulators in the presence of unknown friction and modeling uncertainties is considered. A composite tracking control scheme is proposed in which an adaptive friction estimation is used to estimate the extent of friction and a robust controller is then designed to enhance the overall stability and robustness. It is shown that the design of the fri...

This paper examines the effect of friction model on the simulation accuracy of a hydraulic cylinder by using three friction models: a steady-state friction model, the LuGre model, and the new modified LuGre model. Hydraulic cylinder’s behaviors were measured under sinusoidal input to the servo valve. Simulations were conducted under the same conditions as the experiments. The comparisons of sim...

Friction forces acting on rotators may promote their alignment and therefore eliminate degrees of freedom in their movement. The alignment of rotators by friction force was shown by experiments performed with different spinners, demonstrating how friction generates negentropy in a system of rotators. A gas of rigid rotators influenced by friction force is considered. The orientational negentrop...