Residual stresses caused by the indentation phase of rotary forging

An end surface of a cylindrical workpiece was deformed using a conical rotary-forging die to produce a sectorial indent. The residual stresses over the un-indented surface were measured using an X-ray diffraction method. Radial stresses are zero at the workpiece circumference and close to zero near to the indent edge. Between these sites, they go through a maximum tension. Circumferential stresses are tensile near to the indent edge and compressive near to the workpiece circumference. The line of zero circumferential stress varies in distance from the circumference on going round the indent shape. Regions near this line will experience stress reversals when the indent is caused to rotate by the precession of a rotary forging die. Circumferential cracking at near the half-radius position during rotary forging probably is caused by high-strain fatigue.