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

Abstract

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