the aim of this article is study of tool plunge depth (tpd) effects on mechanical properties of friction stir welding of aa1100 aluminium alloy to a441 aisi steel. for this purpose the 0.1, 0.2, 0.4, and 0.6 mm tpd selected and other welding parameters kept constant. the results shows that the frictional heat increases and stir zone grain size decreases with increasing tpd at both base metals. ...

We introduce a simple model to describe the frictional properties of granular media under shear. We model the friction force in terms of the horizontal velocity ẋ and the vertical position z of the slider, interpreting z as a constitutive variable characterizing the contact. Dilatancy is shown to play an essential role in the dynamics, inducing a stick-slip instability at low velocity. We compu...

The effect of C60 molecular rotation on the nanotribological properties of C60 single crystal surfaces has been studied by atomic/frictional force microscopy. The orientational order-disorder phase transition, in which the high temperature C60 free rotation is reduced to a low temperature hindered rotation, is shown to give rise to an abrupt change in friction and adhesion. This change in frict...

The field of tribology defined in Webster’s Dictionary as “a science that deals with the design, friction, wear and lubrication of interacting surfaces in relative motion” has a long and important history in science and technology[1]. The ancient Egyptians, for example, used water to lubricate the path of sleds employed to transport extremely heavy objects. The first scientific studies of frict...

Low-friction surfaces are critical for efficient joint articulation. The tribological properties of articular cartilage have been studied extensively in native tissue and joints. Despite their importance, very few studies have examined the frictional properties of tissue-engineered cartilage. We have therefore reviewed the relationship between composition, structure and friction in tissue-engin...

Wepresent a fundamental study of the frictional performance of silicamicrospheres, either 4, 2, or 0.5 mm in diameter, on a silicon substrate. The tribological properties of these rolling systems were measured with a ball-on-flat tribometer at various loads. The frictional performance of the rolling systems is found to be highly dependent on load and sphere diameter. Rolling motion was confirme...

This paper introduces a smooth control algorithm for controlling fully actuated distributed manipulation systems that operate by frictional contact. The control law scales linearly with the number of actuators and is simple to implement. Moreover, we prove that control law has desirable robustness properties in the presence of the nonsmooth mechanics inherent in distributed manipulation systems...

Using molecular dynamics based on Langevin equations with a coordinate- and velocity-dependent damping coefficient, we study the frictional properties of a thin layer of "soft" lubricant (where the interaction within the lubricant is weaker than the lubricant-substrate interaction) confined between two solids. At low driving velocities the system demonstrates stick-slip motion. The lubricant ma...