Secondary yielding of forged components due to unloading

Secondary yielding of the workpiece material is a new phenomenon recently r ecognised, which can occur in some bulk metal forming operations. It is cau sed by contracting dies as a result of unloading. Since secondary yielding involves dimensional changes of the workpiece, it becomes one of the factor s which should be taken into account when attempting net-shape forming. This paper contains a comprehensive study of secondary yielding. A simplifi ed theoretical model will serve as a means of explaining the notion of seco ndary yielding. It will also be used to predict dimensional changes of the workpiece. Experimental verification of these results will be presented. Ob served discrepancies will be rectified by an improved analysis using the fi nite element technique and thoroughly discussed. (C) 2001 Elsevier Science B.V. All rights reserved.