Evaluation of FE models for the calculation of die-cavity compensation

Abstract

Engineering components which are defined by complex surfaces and those which are manufactured in high-strength materials are often forged to net-form to eliminate the need for subsequent machining. The design of the dies for such forgings has to take into account the elastic behaviour of the die and the work material during the forging cycle. Several numerical approaches for the definition of compensation requirements are possible. The most comprehensive approach available is based on an interactive, elastic—plastic, FE model which regards the die and the workpiece as elastic and elastic/plastic bodies, respectively. An alternative is to regard the die as perfectly rigid whilst the workpiece is subjected to an elastic-plastic analysis over the forging cycle. A further approach is to create linear elastic models of both the die and the workpiece and to subject these to the derived contact pressures. These three approaches are compared in this paper by analysing a forging example. A simplified linear elastic model which uses an experimentally-defined pressure contour is able to predict the compensation requirements with sufficient accuracy to discount the need for more complex considerations. An alternative to using experimentally-defined pressure contours is to derive these using the 'rigid die, elastic/plastic workpiece' and the 'elastic die, elastic workpiece' analyses.