A FE Billet Model and a Spring-Mass-Damper Model for the Simulation of Dynamic Forging Process: Application to a Screw Press

In forging processes, the determination of blow efficiency is very important, as it quantifies the part of the stroke energy actually transmitted to the billet. Thus, forging processes should be deeply analyzed in order to better understand the stroke energy conversion, accurately estimate blow efficiency, and thus better predict process parameters. In this paper, a spring-mass-damper vibration model is proposed to describe forming operations of a screw press. Parameters specially adapted to the machine-tools system are identified, thanks to a stroke without billet. Thereafter, the experimental upsetting of a copper cylinder is realized, and two independent numerical simulations are performed. First, the billet upsetting is simulated by FE simulation with no consideration of the elastic and damping effect due to the machine-tools behavior in order to determine a relation between the load and the billet height. Then, forging load from the FE simulation is used to perform another simulation of the forging process with the spring-mass-damping model. Results show that the model is relevant to simulate load and ram displacement. Moreover, simulation can predict the distribution of the energy during the simulation and the blow efficiency can be calculated. This new way to obtain blow efficiency might improve productivity in process development and provide a better understanding of energy-driven machines.