Studying the Effect of Punch Nose Radius on Deep Drawing Operation
Engineering and Technology Journal,
2008, Volume 26, Issue 1, Pages 55-73
AbstractThis 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 to form parts with large nose
radii ismuch more than the value required to form 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.
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