Process redesign of complex forged parts with the strongly process-correlated index

The forging processes of two typical complex parts were redesigned by using a strongly process-correlated index (SPCI) to achieve better quality and high productivity. This approach involves extracting the cross-sectional area of three-dimensional complex parts, characterizing the variation in this geometric feature using fractal dimension analysis, and computing the volume ratio between the minimum circumscribing cylindrical envelope of the forged part and the forged part itself. Six crankshaft variants were designed to further demonstrate the effectiveness of the SPCI, the larger the SPCI value the poorer the forgeability. To decrease the risk of crack defects on steering arm in T shape generated during the initial process, the forging process with smaller SPCI is redesigned. As expected, a more uniform velocity distribution can be found in critical areas from simulation results, and this will benefit to solve the problem of crack. For the four-cylinder crankshaft part, the SPCI is relatively large because of the quite different shape of the counterbalances. A redesign of combined two parts in one with a smaller SPCI was proposed and the forging process was double checked with simulation from the aspects of forging defects and the capability of forging press. The redesigned crankshaft forging was forged and two qualified crankshafts with required mechanical properties and dimensional accuracy were obtained in one shot.