Investigation of pressing process for large and thick blades of Francis turbines

Hot pressing process is very popular for thin plates in metal forming. However, the process mechanism for thick plates of high strength steel at high temperature deserves more investigations. The process is characterized by thermo-mechanical behaviors, three-dimensional unsteady deformations and high nonlinearity. In this paper, the model of the process for manufacturing large and thick blades of Francis turbines is proposed. The process analysis is based on finite element method under ANSYS and LS-DYNA platforms to get better understanding of the process. The whole process consists of the pressing forming of a blade from a flat blank, the springback after the forming and the cooling of the pressed blade from high temperature to room temperature. Investigation of the stress evolution is also performed.