in this paper, the direct extrusion process of bimetallic rods in conical dies is analyzed by an improved upper bound method. the deformation zone is subdivided into six smaller zones and by considering a non-spherical entrance boundary to the deformation zone, a velocity field is presented which is different from velocity fields employed in previous studies. the total power consumption of the ...

The origin of friction comes from the atomic interaction at interfaces. Analytic theories indicated that there is no static friction on clean incommensurate interfaces, while a recent experiment revealed that the static friction coefficient was anisotropic with respect to the lattice orientation, but did not vanish on two clean Ni(100) mis-orientated surfaces. To understand this friction anisot...

in this research, an apparatus was made and utilized to determine the friction coeffi-cient of chickpea grains on steel surfaces. experiments were carried out on two black and galvanized surfaces and at four sliding velocities of 5, 20, 100 and 500 mm/min, at three moisture content of 7.5%, 15% and 21% wet basis (w.b.) and at three vertical pressure values of 14.28, 100 and 150 kpa. the followi...

The most prominent feature of sheet material forming process is an elastic recovery phenomenon during unloading which leads to springback and side wall curl. Therefore evaluation of springback and side wall curl is mandatory for production of precise products. In this paper, the effects of some parameters such as friction coefficient, sheet thickness, yield strength of sheet and blank-holder fo...

We propose a mean field (MF) theory for a homogeneously driven granular gas of inelastic particles with Coulomb friction. The model contains three parameters, a normal restitution coefficient rn, a maximum tangential restitution coefficient r m t , and a Coulomb friction coefficient μ. The parameters can be tuned to explore a wide range of physical situations. In particular, the model contains ...

This paper presents a method of determining the friction coefficient in metal forming using multilayer artificial neural networks based on experimental data obtained from strip drawing test. The number of input variables of the artificial neural network has been optimized using genetic algorithm. This process is based on surface parameters of the sheet and dies, sheet material parameters and cl...

In this paper, by applying analytical method and using experimental method data, the effect of sliding velocity on friction coefficient for contact of copper with copper is investigated. Some equations for obtaining friction coefficient as a function of sliding velocity for contact of copper with copper by applying second analytical method and using experimental method data are achieved. The re...

Two-layer metallic sheets have wide applications in aerospace, marine, automotive and domestic industries due to their superlative characteristics. In this paper, the formability of two-layer sheet is investigated through analytical, experimental and numerical approaches. An analytical model is developed based on Marciniak-Kuczynski method associated Hill’s non-quadratic yield criterion. Formin...