Integrated approach to the analysis of thermo-mechanical fatigue of dies in hot and warm forging

The paper is focused on the investigation of life assessment of dies in hot and warm forging related to thermo-mechanical fatigue (TMF). The prediction of dies service life can be considered an ambitious target, together with the possibility to compare the TMF behaviour of different materials, effects of process parameters and geometry of die cavities. To these aims an approach has been proposed for the investigation of TMF of dies, where numerical and experimental techniques are integrated. It combines three environments: i) replication of industrial forging in a laboratory pilot plant; ii) numerical simulation of the entire forging cycle; iii)TMF testing on specimens, replicating thermomechanical cycles and thermal gradients. The first environment is the primary source of data (die temperatures) used to refine numerical model and forging simulations. The second one, after the refinement, should predict with reasonable accuracy thermal and mechanical cycles to be considered in the third environment. The third environment is aimed to predict TMF tool life through execution of simulative test in laboratory, replicating the previously determined cycles on new design specimens of die material in the considered operating conditions.