Property-Controlled Multi-Stage Hot Sheet Metal Forming

In multi-stage hot sheet metal forming the final microstructure and part geometry result from the thermo-mechanical history throughout the process. With the aim of implementing a closed-loop control for these properties, control-oriented property models are derived. As a general basis a process chain in a progressive die is assumed in which a sheet metal blank is first heated and then hot-formed and simultaneously quenched in several stages (see Figure a). For a real-time estimation of thinning during hot stretch drawing in the described multi-stage setup an element-based, time-discrete property model is developed. This model is coupled with a soft sensor that estimates the temperature distribution in the sheet on the basis of thermometric data for every calculation time step of the property model. For a first validation of the property model the temperature drop during hot stretch drawing (see Figure b) is experimentally determined and passed on to the property model. A comparison of thinning calculated with the property model shows good agreement with the experimental data (see Figure c).