Lubrication aspects of the deep drawing of stainless steel, titanium and nickel-base alloys at elevated temperatures

Abstract

This paper reports on the initial stages of a combined experimental and finite element analysis (FEA) of a deep drawing process. The objective of this research is to determine the most important factors influencing a drawing process, utilizing the help of a design of experiments and statistical analysis. The parameters varied include the punch and die radii, the punch velocity, clamping force, friction and draw depth. A deep drawing rig was designed and built for this purpose. Punches and dies of various geometries were manufactured. From previous FEA work and the experimental work performed to date, it seems that the punch/die radii have the greatest effect on the thickness of the deformed mild steel cups compared to blank-holder force or friction. The smaller is the punch/die radii, the greater is the punch force and shorter is the final draw. It has also been observed from the work to date that the speed of drawing plays an interesting role, in so far as, the higher is the speed the further is the draw, which is not entirely as expected. The cause of this will be further investigated. If the blank-holder force is not kept within the upper and lower limit of reasonable range it does have a significant effect on depth of draw, with the punch tearing through the bottom of the cup if the force is too high and if too low wrinkling of the flange area occurs. After observing the anisotropic effects of the rolling process on the sheet material through drawing it and seeing the extent of earing in the flange, some blanks were annealed for stress relief, then the draw depth was compared to that of the original mild steel blanks.