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...

Numerical simulation of sheet metal forming processes has become indispensable in the last decades. Although complexity frictional behaviour is identified as a key factor for prediction accuracy, industry commonly considers constant friction coefficient whole tool. Furthermore, influence roughness distribution tool not yet been addressed. In this study die local an advanced model evaluated thre...

Tire-road friction is the most important piece of information used by active safety systems. However, most conventional friction estimation/ detection methods are accurate only within the non-linear region. In addition, such methods require numerous sensors, such as yaw rate sensors, acceleration sensors, and steering angle sensors. In this paper, a friction estimation method using a tire vibra...

One of the ultimate goals in landslide hazard assessment is to predict maximum landslide extension and velocity. Despite much work, the physical processes governing energy dissipation during these natural granular flows remain uncertain. Field observations show that large landslides travel over unexpectedly long distances, suggesting low dissipation. Numerical simulations of landslides require ...

We propose a simple friction model for isolated polymer chains on a solid substrate. The chains are pulled at constant velocity by one end, the other end can be trapped on the solid substrate on localised sites. We focus on the energy dissipation due to the traps. This simple model leads to non trivial friction laws, depending on the velocity and the distance between traps. Some refinements of ...

[1] Results are presented from a field investigation of near-bed turbulence above degrading waveformed sand ripples in 17-m water depth on the inner shelf. The heights of the 50-cm wavelength primary ripples were about 5 cm at the start of the observation period, and decreased by a factor of 2 within 15 days. The principal degradation mechanism involved fish making pits in the seafloor. Near-be...

A new contribution to friction is predicted to occur in systems with magnetic correlations: Tangential relative motion of two Ising spin systems pumps energy into the magnetic degrees of freedom. This leads to a friction force proportional to the area of contact. The velocity and temperature dependence of this force are investigated. Magnetic friction is strongest near the critical temperature,...

An intriguing feature of granular matter is the close coexistence of solid-like regions and liquid-like flows. We study steady, fully-developped, granular flows confined between parallel vertical sidewalls. The sidewall friction stabilizes the underlaying heap at an inclination exceeding the angle of repose and increasing with flow rate. Our experiments reveal, in agreement with numerical simul...

This paper investigates artificial neural network (ANN) based modelling and compensation of nonlinear friction which is a major cause of performance degradation in servo mechanisms. Different friction modelling and compensation schemes have been reviewed and neural network based hybrid compensation methods are proposed and experimentally tested on a direct drive servo mechanism. Inertial dynami...

The usage of the finite volume method (FVM) for calculation of bulk metal forming working pressure is described in this paper. FVM is applied on two-dimensional orthogonal grids and colocated variable arrangement. The application of the FVM is done in case of solving the plastic flow during extrusion processes with different boundary conditions. The method of involving of the most frequently us...