The effect of friction in the thermal convection instability of granular fluids is studied by means of molecular dynamics simulations. It is found that the transitions between different convective states (zero, one, and two rolls) are primarily governed by the average energy loss per collisions and not by the friction and restitution coefficients separately, and can be roughly described in term...

Time-stepping methods using impulse-velocity approaches are guaranteed to have a solution for any friction coefficient, but they may have nonconvex solution sets. We present an example of a configuration with a nonconvex solution set for any nonzero value of the friction coefficient. We construct an iterative algorithm that solves convex subproblems and that is guaranteed, for sufficiently smal...

Hot ring rolling is a highly nonlinear, unsteady-state and asymmetry process which is affected by many parameters. The friction coefficient between the ring ,the driver roll and the idle roll is one of the problems, which has significant effect on the quality of final product. In this study, the effect of these two parameters on hot ring rolling was investigated based on a 3D coupled-thermo mec...

An experiment is conducted in which a free-standing bicycle wheel is given an initial angular speed and then allowed to slow down to rest. Measurements of the wheel speed, using a magnetic sensor, during the decay are compared to predictions from a model accounting for a combination of viscous and dry friction at the wheel bearing. The time history data indicate two dynamic regimes: (i) a highe...

A calibration process is developed to determine the parameter values. Three-axial compressions tests in laboratory and neural network are used to determine the material internal friction angle and stiffness, respectively. These tests are repeated numerically using PFC models with different sets of particle friction coefficients and particle stiffness values. Three-axial compressions tests are f...

The frictional behaviors of fullerenes C60 and C70 were studied because they were speculated to be solid lubricants. For the sublimated pure C60 films on Si(001), a high friction coefficient (0.55–0.8) was observed under different loads and pin materials. For the C70 film, the friction coefficient showed a pin dependence, which changed from 0.5 with an Al2O3 pin to about 0.9 with a 440 stainles...

The menisci protect the articular cartilage by reducing contact pressure in the knee. To restore their function after injury, a new silk fibroin replacement scaffold was developed. To elucidate its tribological properties, friction of the implant was tested against cartilage and glass, where the latter is typically used in tribological cartilage studies. The silk scaffold exhibited a friction c...

In the hot compression test friction has a detrimental influence on the flow stress through the process and therefore, correcting the deformation curve for real behavior is very important for both researchers and engineers. In this study, a series of compression tests were simulated using Abaqus software. In this study, it has been employed the Taguchi method to design experiments by the factor...

Deformation of the material during cyclic expansion extrusion (CEE) is investigated using upper-bound theorem. The analytical approximation of forming loads agrees very well with the FEM results for different amounts of chamber diameter, friction factor and also for lower die angles. However, the difference between analytical and numerical solution increases at higher die angles which are expla...

Thin solid lubricating coatings of Pb-Mo-S were deposited on steel substrates via ion-beam deposition. Coating endurance and friction coefficients under dry air sliding conditions were monitored with ball-on-disk tests; additional tribological testing was performed using a ball-on-flat reciprocating test rig to investigate intermediate sliding distances (100-32000 cycles). Rutherford backscatte...