A screw thread is cold rolled on a 1015 low-carbon steel bolt of 6.25 mm diameter. Observation shows that the length of the contact zone between die and screw blank is L = 1.25 mm. The average strain hardening during rolling corresponds to a strain of μ= 0.4.
Calculate:(a) the applicable flow stress, and(b) the average interface pressure in the contact zone.
Determine:(c) if there is any danger of internal fracture (make a sketch to illustrate the point).