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...

Tribological conditions can change drastically during heavy loaded regimes as experienced in metal forming; this is especially critical when lubrication can only be applied at the early stage of the process because the homogeneous lubricant layer can break along the die-workpiece interface. In these cases, adopting a constant friction factor for the lubricant-surface pair may not be a valid ass...

Macroscopic friction coefficients observed in experiments are the result of various types of complex multiscale interactions between sliding surfaces. Therefore, there are several ways to modify them depending on the physical phenomena involved. Recently, it has been demonstrated that surface structure, e.g. artificial patterning, can be used to tune frictional properties. In this paper, we sho...

This paper develops a model to assess the quantitative effect of entry cost and financial friction on cross-country income and total factor productivity (TFP) differences. The main focus is on the interaction between entry cost and financial friction. The model is calibrated to match establishment-level statistics for the U.S. economy assuming a perfect financial market. The quantitative analys...

The sliding of a solid object on a solid substrate requires a shear force that is larger than the maximum static friction force. It is commonly believed that the maximum static friction force is proportional to the loading force and does not depend on the apparent contact area. The ratio of the maximum static friction force to the loading force is called the static friction coefficient µM, whic...

A new insight into the mechanics of belt friction is given. A conceptual and methodological drawback in the presentation of the classical derivation of the force required to pull the belt over a fixed drum against the hold-force and the friction between the belt and a drum is pointed out, corrected and discussed. The total forces due to pressure and friction (P and F ) are evaluated in magnitud...

The major losses of fluid flow in plastic pipes due to friction are usually few or negligible some cases, and this is the assumption that value factor small (small roughness). This work aimed estimate vs Reynolds number compared against previous data, was estimated using an experimental model consisting a polypropylene pipe with nominal outside diameter 16mm length 8.5 meter eighteen elbows con...