Compensation of billet variabilities through metamodel-based optimization in open die forging

Closed-die forging preforms are usually made by open die forging operations, which are subject to significant variabilities. A sensitivity study covering a wide range of influencing parameters has highlighted the predominant influence of the initial billet geometry. The forging die strokes were also highly influential, while their fidelity is sufficient to use them as control parameters in order to compensate the geometrical dispersions of the billet. Consequently, their optimization was performed by taking a nominal preform geometry as the target. Polynomial surrogate models have been constructed to enable real-time optimization. A specific preform was used as a demonstrator in this study, while the approach was generic. The surrogate models were built using data from finite element simulations, which were first validated with an experimental campaign. On the one hand, this approach introduced agility by allowing changes in the billet geometry, and on the other hand, it allowed individual customization of the specific route to each billet.