In deep drawing of a cylindrical cup, is it always necessary that there to be tensile circumferential stresses on the element in the cup wall, a shown in Fig. 7.50b? Explain.
The reason why there may be tensile hoop stresses in the already formed cup in Fig. 7.50b
on p. 388 is due to the fact that the cup can be tight on the punch during drawing. That is why
they often have to be stripped from the punch with a stripper ring, as shown in Fig. 7.49a on
p. 387. There are situations, however, whereby, depending on material and process parameters,
the cup is sufficiently loose on the punch so that there are no tensile hoop stresses developed.
