Studying the Effect of Punch Nose Radius on Deep Drawing Operation


This work aims to study the effect of varying punch nose radius used in deepdrawing operation, on produced cup wall thickness, stress and strain distributionacross the wall of the drawn part, hydrostatic pressure ,residual stress developed inthe drawing part after drawing, and the value of work done to form the requiredshape of drawn part.In this work, six types of punches with various nose radii have been used toform a cylindrical cup of (44mm) outer diameter,(28mm) height, and(0.5mm)sheet thickness of mild steel of (0.15%) carbon content. A commerciallyfinite element program code (ANSYS 5.4), was used to perform the numericalsimulation of the deep drawing operation, and the numerical results werecompared with the experimental work.The results show that, the value of work required to form parts with large noseradii ismuch more than the value required to form parts with small punch noseradii. An increase in the punch nose radius, results in an insignificant increase inshear stress and shear strain. These values are very small which can be ignored.The greatest thinning is seen to occur with hemispherical punch (Dome shapedpunch) due to great stretching of the metal over the punch head. The maximumtensile stresses and the maximum thinning of the dome wall occur nearly at theapex of the dome (a friction coefficient nearly equal to zero). In the presence offriction, the position of maximum strain, which corresponds to the location ofmaximum thinning point, moves away from the apex. The larger the friction is,the larger is the distance between the apex and the point of maximum thinning.The frictional force is applied to the metal largely by the edge of the punch andnot by its flat section. Maximum thickening of the cup wall occurs at the flangerim, and this thickening increases with punch stroke.