Numerical Estimation of Frictional Effects in Equal Channel Angular Extrusion

Abstract

The purpose of this study is to numerically estimate the friction coef cient for equal channel angular extrusion with and without back pressure. Three-dimensional nite element analysis is employed to estimate the coef cient of friction from the maximum pressing load, a crucial variable in die design. The nite element model consists of a billet, a plunger, a ram, and a die, where the interface between the billet and the die is modeled by the Coulomb friction model with truncated shear stress. The numerical model was validated by comparing the grid deformation patterns in the extrusion symmetry plane, and by comparing the load versus stroke curves for the ram (pressing load) and for the plunger (back pressure). Results indicate that the coef cient of friction can be accurately estimated from the maximum pressing load, but it is necessary to modify the traditional Coulomb friction model.

A novel equal channel angular pressing design to eliminate punch deflection and to reduce the pressing force

“…The Coulomb friction law (Equation 1) is applied for most of engineering problems. However, there is several evidences in literature that Coulomb friction law is not valid for high contact pressure systems and the friction forces in high contact regimes vary exponentially by changes in applied load (Equation 2) [19,20].…”

“…The Coulomb friction law (Equation 1) is applied for most of engineering problems. However, there is several evidences in literature that Coulomb friction law is not valid for high contact pressure systems and the friction forces in high contact regimes vary exponentially by changes in applied load (Equation 2) [19, 20]. $$$\vcenter{\openup.5em\halign{$\displaystyle{#}$\cr {F}_{friction}=\mu \cdot N\hfill\cr}}$$$ $$$\vcenter{\openup.5em\halign{$\displaystyle{#}$\cr {F}_{friction}=a\hskip0.17em\cdot{}\hskip0.17em{e}^{b.\mu }\hfill\cr}}$$$ …”

Experimental and Numerical Investigation of the Frictional Forces in Equal Channel Angular Pressing

“…Besides, the effect of friction value on the results of numerical analysis of the ECAP process was investigated in a work by Balasundar and Raghu (2010). Souza, et. al.…”