Friction measurements have been performed on microcrystalline, ultrananocrystalline, and diamond-like carbon DLC films with natural diamond counterfaces in the temperature range of 8 K to room temperature. All films exhibit low friction 0.1 in air at room temperature. In ultrahigh vacuum, microcrystalline diamond quickly wears into a high friction state 0.6 , which is independent of temperature...

Frictional forces arise whenever objects around us are set in motion. Controlling them in a rational manner means gaining leverage over mechanical energy losses and wear. This paper presents a way of manipulating nanoscale friction by means of in situ lubrication and interfacial electrochemistry. Water lubricant is directionally condensed from the vapor phase at a moving metal-ionic crystal int...

The melting of an ultrathin lubricant film is studied at friction between atomically flat surfaces. We take into account fluctuations of lubricant temperature, which are defined by the Ornstein-Uhlenbeck process. Phase diagrams and portraits are calculated for secondand first-order transitions (the melting of an amorphous and that of a crystalline lubricants, respectively). It is shown that, in...

Friction is a well-known, but poorly understood, phenomenon that affects virtually all aspects of daily life. In some cases, friction is desirable, e.g., high friction in clutches leads to the effective transmission of forces between an automobile’s engine and its wheels, while in other cases friction is a significant drawback, e.g., friction between the piston and cylinder wall decreases the e...

LuGre friction model is an ordinary differential equation that is widely used in describing the friction phenomenon for mechanical systems. The importance of this model comes from the fact that it captures most of the friction behavior that has been observed including hysteresis. In this paper, we study some aspects related to the hysteresis behavior induced by the LuGre friction model.

Friction plays a key role in how ruptures unzip faults in the Earth's crust and release waves that cause destructive shaking. Yet dynamic friction evolution is one of the biggest uncertainties in earthquake science. Here we report on novel measurements of evolving local friction during spontaneously developing mini-earthquakes in the laboratory, enabled by our ultrahigh speed full-field imaging...

Friction plays an important role in the behavior of flowing granular media. The effective friction coefficient is a description of shear strength in both slow and rapid flows of these materials. In this paper, we study the steady state effective friction coefficient μ in a granular material in two steps. First, we develop a new relationship between the steady state effective friction coefficien...

In this paper, an adaptive robust control (ARC) scheme based friction compensation strategy is presented for a class of mechanical systems in the presence of dynamic friction effects. In contrast to existing deterministic robust control (DRC) and adaptive control (AC) schemes, the proposed ARC scheme utilizes both the structural information of the dynamic friction model and the available prior ...

Direct tyre-road contact friction estimation is essential for future active safety systems. Friction estimation methods were proposed earlier for driving conditions in the presence of a slip angle or slip ratio. However, the estimation of friction from a freely rolling tyre is still an unsolved topic. This study uses three 3-axis accelerometers on the inner liner of a tyre to detect friction po...

In this paper friction induced limit cycles are predicted for a simple motion system of a single motor-driven inertia subjected to friction and a PID-controlled regulator task. The two friction models used, i.e., (i) the dynamic LuGre friction model and (ii) the static Switch friction model, are compared with respect to the so-called hunting phenomenon. Analysis tools originating from the field...