An Upper Bound Elemental Technique for Load Prediction of Axisymmetric Hot Forged Specimens

Forging is a metal forming process involving shaping of metal by the application of compressive forces using hammer or press. Forging load of equipment is an important function of forging process and the prediction of the same is essential for selection of appropriate equipment. In this study a hot forging material i.e. 42CrMo4 steel is selected which is used in automotive components like axle, crank shaft. Hot forging experiments at 750°C are carried out on cylindrical specimens of aspect ratio 0.75 and 1.5 with true height strain (ln (h_o/h_f)) of 0.6. Forging load for the experiments is calculated using slab and upper bound deformation models as well as Metal forming simulation using commercially available FEA software. The upper bound models with 30% deviation from the simulation results are found to be more accurate compared to the slab models. The gap between theoretical and simulation results are bridged using an advanced upper bound solution called Upper Bound Elemental Technique wherein velocity field with optimization parameter is proposed and using these velocity fields the load prediction is carried out for each element of the specimen. The elemental loads are summed up together to get the final forging load whose accuracy is 10%.