Studying the effect of punch nose radius on deep drawing operation

Abstract EN

This work aims to study the effect of varying punch nose radius used in deep drawing operation, on produced cup wall thickness, stress and strain distribution across the wall of the drawn part, hydrostatic pressure, residual stress developed in the drawing part after drawing, and the value of work done to form the required shape of drawn part.

In this work, six types of punches with various nose radii have been used to form a cylindrical cup of (44mm) outer diameter, (28mm) height, and (0.5mm) sheet thickness of mild steel of (0.15 %) carbon content.

A commercially finite element program code (ANSYS 5.4), was used to perform the numerical simulation of the deep drawing operation, and the numerical results were compared with the experimental work.

The results show that, the value of work required forming parts with large nose radii is much more than the value required forming parts with small punch nose radii.

An increase in the punch nose radius, results in an insignificant increase in shear stress and shear strain.

These values are very small which can be ignored.

The greatest thinning is seen to occur with hemispherical punch (Dome shaped punch) due to great stretching of the metal over the punch head.

The maximum tensile stresses and the maximum thinning of the dome wall occur nearly at the apex of the dome (a friction coefficient nearly equal to zero).

In the presence of friction, the position of maximum strain, which corresponds to the location of maximum 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 and not by its flat section.

Maximum thickening of the cup wall occurs at the flange rim, and this thickening increases with punch stroke.