EVALUATION OF FE MODELS FOR THE CALCULATION OF DIE-CAVITY COMPENSATION

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 o f the dies for such forgings has to take into account the elastic beha viour of the die and the work material during the forging cycle. Sever al numerical approaches for the definition of compensation requirement s are possible. The most comprehensive approach available is based on an interactive, elastic-plastic, FE model which regards the die and th e workpiece as elastic and elastic:plastic bodies, respectively, An al ternative 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 a nd the workpiece and to subject these to the derived contact pressures . These three approaches are compared in this paper by analysing a for ging example. A simplified linear elastic model which uses an experime ntally-defined pressure contour is able to predict the compensation re quirements with sufficient accuracy to discount the need for more comp lex considerations. An alternative to using experimentally-defined pre ssure contours is to derive these using the 'rigid die, erastic/plasti c workpiece' and the 'elastic die, elastic workpiece' analyses.