An upper bound analysis of a process-induced side-surface defect in forgings: Part 2: Characteristics and criteria curves

Abstract

An upper bound analysis for an axisymmetric forging with a double ram action has been developed. The results of the analysis provide manufacturing conditions that can be used without the development of unacceptable side-surface cracks. There are processing conditions that cause the defective flow pattern to be most favorable. The transition from an energetically-favorable sound flow to an energetically-favorable defect flow is used to determine the criteria curves for the prevention of this side-surface defect. It is found that the formation of the side-surface cracks is promoted by smaller diameter rams, smaller workpiece thicknesses and lower friction. The first paper in this two-part series presents the velocity fields and the individual power terms that were derived based upon these velocity fields, whilst this second paper shows the characteristics of the upper bound solution for the double action forging process. This second paper also presents the criteria for the prevention of the side-surface defects that were determined based upon the upper bound solution.