Friction between ordered, atomically smooth surfaces at the nanoscale (nanofriction) is often governed by stick-slip processes. To test long-standing atomistic models of such processes, we implement a synthetic nanofriction interface between a laser-cooled Coulomb crystal of individually addressable ions as the moving object, and a periodic light-field potential as the substrate. We show that s...

This work studies the dynamics of a 3D dimer bouncing upon a horizontal plate undergoing a vertical harmonic vibration. Despite complex interactions within the system due to impacts and friction, numerical simulation shows that, under certain conditions prescribed for the dynamics, the center of mass of the dimer, when projected onto a horizontal plane, will follow a circular orbit. The phenome...

We present a theoretical, numerical, and experimental study about the sliding motion of an angular particle down a vibrated smooth plane. The model is based on a Coulomb's friction law with a unique friction coefficient. The model is solved numerically and is tested with controlled experiments. Different motion regimes are identified and the particle behavior is governed by two dimensionless pa...

We derive an effective boundary condition for dense granular flow taking into account the effect of the heterogeneity of the force network on sliding friction dynamics. This yields an intermediate boundary condition which lies in the limit between no slip and Coulomb friction; two simple functions relating wall stress, velocity, and velocity variance are found from numerical simulations. Moreov...

We study the discretized problem of the shape optimization of three-dimensional elastic bodies in unilateral contact. The aim is to extend existing results to the case of contact problems obeying the Coulomb friction law. Mathematical modelling of the Coulomb friction problem leads to an implicit variational inequality. It is shown that for small coefficients of friction the discretized problem...

Traditional analyses of slip at corners of contacts, based on linear elasticity and a Coulomb friction law, are very sensitive to the details of local geometries, owing to the effects of elastic singularities. Following the use of cohesive-zone models to address such issues in mode-II fracture, we present analyses of slip and wear at corners of contacts when a finite interfacial shear strength ...

The effect of a height-dependent asperity radius of curvature is accounted for in a recently developed scaledependent model of contact and friction. The contact and friction model includes the effects of adhesion, using the Maugis model, and of scale-dependent friction, using the Hurtado and Kim single asperity friction model. This multiasperity model has been modified to include the effect of ...

We show that the static friction force which must be overcome to render a sticking contact sliding is reduced if an external torque is also exerted. As a test system we study a planar disk lying on a horizontal flat surface. We perform experiments and compare with analytical results to find that the coupling between static friction force and torque is nontrivial: It is not determined by the Cou...

This paper focuses on the state-periodic adaptive compensation of cogging and Coulomb friction for permanent magnet linear motors (PMLM) executing a task repeatedly. The cogging force is considered as a position dependent disturbance and the considered Coulomb friction is non-Lipschitz at zero velocity. The key idea of our disturbance compensation method is to use one trajectory-period past inf...

In this paper we announce some new mathematical results on the stability of quasistatic paths of a single particle linearly elastic system with Coulomb friction and persistent normal contact with a flat obstacle.A quasi-static path is said to be stable at some value of the load parameter if, for some finite interval of the load parameter thereafter, the dynamic solutions behave continuously wit...