Secondary yielding of forged components due to unloading

Secondary yielding of the workpiece material is a new phenomenon recently recognised, which can occur in some bulk metal forming operations. It is caused by contracting dies as a result of unloading. Since secondary yielding involves dimensional changes of the workpiece, it becomes one of the factors which should be taken into account when attempting net-shape forming. This paper contains a comprehensive study of secondary yielding. A simplified theoretical model will serve as a means of explaining the notion of secondary yielding. It will also be used to predict dimensional changes of the workpiece. Experimental verification of these results will be presented. Observed discrepancies will be rectified by an improved analysis using the finite element technique and thoroughly discussed.