Detrmining the transitonal area of square cups in oil hydraulic forming process

Abstract

The precise stress distribution in the focus of deformation, i.e. in the square cup flanges (of nonaxis- symmetric parts), during the process of deep drawing is quite difficult to determine, owing to the fact that during the process of their forming three characteristic areas appear on the flange: corner area, side zone and the transitonal area between them. Different stress-strain states appear in the above mentioned areas. There are six possible combinations of the stress- strain state. An attempt to determine the maximum value of normal stress in radial direction, i.e. the drawing force, by means of a single equation has not given good results. This paper provides both a theoretical analyses of the stress-strain state on a square cup and the derivation of the expressions leading to the determining of a transitional area value and also resulting in six different equations enabling calculatng of the force forming the square cups in oilhydraulic process. Practical experimental results have confirmed the validity of the expression enabling determiningthe value of transitional area.