Modeling of stick-slip phenomena using molecular dynamics

Molecular dynamics simulations are performed to investigate the atomic-scale stick-slip phenomenon of a pyramidal diamond tip inserted into the Ag(010) surface. The mechanisms behind the stick-slip events are investigated by considering sliding speeds between 1.0 and 5.0 ms-1 and vertical support displacements of 5 and 15 Å. The analysis of the dynamic features of the substrate shows that dislocations are extrinsically linked to the stick events, with the emission of a dislocation in the substrate region near the tip, when slip occurs after stick. For small vertical displacements, the scratch in the substrate is not continuous because the tip can jump over the surface when slipping, whereas at 15 Å, a continuous scratch is formed. The dynamic friction coefficient increases from ∼0.13 to ∼0.46 with increasing depth, but the static friction coefficient increases only from ∼0.32 to ∼0.54. At the larger depths the tip does not come to a halt during stick as it does for shallow indents. Instead the tip motion is more continuous with stick and slip manifested by periods of faster and slower motion. Although the exact points of stick and slip depend on the sliding speed, the damage to the substrate, the atomistic stick-slip mechanisms, and the friction coefficients are relatively independent of speed over the range of values considered

Nanoscratch behavior of multi-layered films using molecular dynamics

Molecular dynamics simulations are performed to study the plastic deformation, stress and chip formation of scratched multi-layered films. The results showed that stick–slip and work-hardening behaviors were observed during the scratching process. There was a pile-up of amorphous disordered debris atoms and shear rupture ahead of the probe and a clear side-flow on the lateral sides of the probe when the probe moved forward. Both the plastic energy and the adhesion increased with an increase in the scratching depth. The glide band of the interface was on the {111}?110? slip system with a maximum width of the glide band of about 1 nm. The strain energy stored in the deformed structure caused a higher stress region in the material in front of the tool edge, with a maximum stress of about 10 GPa. In addition, the mechanical response and thermal softness phenomenon are discusse

Friction and nonlinear dynamics

The nonlinear dynamics associated with sliding friction forms a broad interdisciplinary research field that involves complex dynamical processes and patterns covering a broad range of time and length scales. Progress in experimental techniques and computational resources has stimulated the development of more refined and accurate mathematical and numerical models, capable of capturing many of the essentially nonlinear phenomena involved in friction