Question

Necking phenomena do not occur in the process of a cup or deep drawing.

(a) True

(b) False

This question was posed to me at a job interview.

My question comes from Deep Drawing in section Mechanical Working of Metals of Casting-Forming-Welding II

Answer 1

The correct answer is (b) False

For explanation I would say: In deep drawing, necking of metal sheet is a very common phenomena, which occurs near the punch profile due to inducement of tensile stresses in the punch material. The metal sheet under the holding plate experiences compressive hoop stresses and radial tensile stresses due to blank holding plate. In this method, thickness of the cup wall generally increases from the bottom side to the top side.