EFFECT OF SURFACE ROUGHNESS FOR WORKPIECE an‎d TAPER DIE ON FULL ELASTO HYDRODYNAMIC LUBRICATION (FEHL) IN ALUMINUM COLD DIRECT EXTRUSION WITH MAXIMUM REDUCTION

To reduce friction effects in extrusion process, the contact surfaces must be separated by lubricant film .One of the technique is FEHL, in which the oil film produces from plastic and elastic deformation for workpiece and die respectively along working zone, and this process happens if the extrusion speed equals or greater than critical speed. The surface roughness for workpiece and die in extrusion process represent significant parameters on this technique. So that it must be limited a range in which FEHL is commences. In present work the range of surface roughness degrees are estimated in direct extrusion of 1060.1 aluminum alloy by using taper die made from alloy steel with maximum extrusion ratio (Ao /Ai) equals to 2.77. Calculations of plastic deformation in billet of aluminum at each point along working zone are done by using a numerical modeling of hydrodynamic lubrication. This modeling is based on finite difference method, and that leads to find out the distribution of pressure along forming zone distance, and new variation of film thickness.