FORGING PREFORM DESIGN WITH SHAPE COMPLEXITY CONTROL IN SIMULATING BACKWARD DEFORMATION

This paper presents a preform design method which employs an alternati ve boundary node release criterion in the finite element simulation of backward deformation of forging processes. The method makes use of th e shape complexity factor which provides an effective measure of forgi ng difficulty. The objective is to release die contacting nodes in a s equence which will minimize the geometric complexity throughout the ba ckward deformation simulation. This is done by calculating the effect of releasing each of a select group of boundary element nodes at each finite element solution step. The particular detached node which resul ts in the minimum shape complexity factor will be released for the cur rent step. This process continues for each backward step until the las t few nodes remain in contact. This design method is demonstrated thro ugh the simulated forging of an integrated blade and rotor turbine dis k blank. A preform shape developed by this method is compared with an empirically designed preform. Performance parameters for comparison in clude die fill, flash volume, effective strain variance; frictional po wer and die load. Comparing the results of the forward simulations ind icates improved performance of the preform design using FEM based back ward deformation method over that of the empirical design.