A linear complementarity formulation for dynamic multi-rigid-body contact problems with Coulomb friction is presented. The formulation, based on explicit Euler integration and polygonal approximation of the friction cone, is guaranteed to have a solution for any number of contacts and contact con guration. A model with the same property is formulated for impact problems with friction and nonzer...

The microstructure and residual stresses of an AA6040 Al to AZ31B Mg friction stir weld are studied using scanning electron microscopy and X-ray diffraction. The complex material flow promoted by the friction stir welding process results in a fine grained structure in the stir zone of both materials due to dynamic/recovery recrystallization. The interface between the materials is characterized ...

A kind of 2.5-dimensional C/C-SiC composites was fabricated by using Isothermal Chemical Vapour Infiltration process (ICVI). Frictional properties of this material were evaluated by using MM-1000 under dry condition. Average dynamic friction coefficient of it was 0.16, static friction coefficient and average coefficient stability were 0.15 and 0.56, respectively. However, weight wear rate was l...

We have constructed a sliding block cryotribometer designed to measure friction at cryogenic temperatures and UHV conditions. An optical cryostat and high speed video was used to monitor the motion of the block. The temperature range of the measurements was 4–460 K. Both the static and dynamic friction coefficients were determined for a steel ball on stainless steel, sapphire, and PTFE (Teflon)...

The initial results of a research aimed at investigating to what extent high resolution encoders, which are getting available for common industrial motion control and robotics applications, can be exploited to compensate for non linear friction terms are presented in this paper. The 22 bits resolution sensor used allowed a neat analysis of the dynamic behavior of friction forces in the preslidi...

We conducted experiments in which steel and silicon or quartz are clamped together. Even with the smallest tangential forces we could apply, we always found reproducible sliding motions on the nanometer scale. The velocities we study are thousands of times smaller than in previous investigations. The samples first slide and then lock up even when external forces hold steady. One might call the ...

In this paper we study a one-dimensional dynamic model of dry friction with slip velocity dependent coefficient. In many cases, this model has more than one solution. We introduce a perturbed friction condition which allows us to regain the uniqueness of the solution. We show that the perturbed problem's solutions pointwise converge to a particular solution of the initial problem when the pertu...

Two adaptive nonlinear friction compensation schemes are proposed for second-order nonlinear mechanical systems with a partially known nonlinear dynamic friction model to achieve asymptotic position and velocity tracking. The first scheme has auxiliary filtered states so that a simple open-loop observer can be used. The second one has a dual-observer structure to estimate two different nonlinea...

Traditionally the positioning of pneumatic actuators has been limited to movement between preset stops or switches. The restricting factors preventing the use of pneumatic cylinders for accurate servo-control arise from highly nonlinear dynamic properties such as air compressibility and friction effects, which combine to severely degrade time response and positional accuracy. Many real systems ...

The background and necessity of application of numerical simulation method in research on friction materials of automotive brake are analysed. The numerical analysis methods of conversion of braking energy, distribution of friction heat, transfer of friction heat and thermal mechanical coupling, are discussed. The dynamic temperature field and thermal stress field of the same brake disc and two...