FE calculations on a three stage metal forming process of Sandvik Nanoflex

摘要

Sandvik NanoflexTM combines good corrosion resistance with high strength. This steel has good deformability inudaustenitic conditions. It belongs to the group of metastable austenites, which means that during deformation a strain-inducedudtransformation into martensite takes place. After deformation, transformation continues as a result of internal stresses. Bothudtransformations are stress-state and temperature dependent. A constitutive model for this steel has been formulated, basedudon the macroscopic material behaviour measured by inductive measurements. Both the stress-assisted and the strain-inducedudtransformation into martensite have been incorporated in this model. Path-dependent work hardening has also been takenudinto account. This article describes how the model is implemented in an internal Philips FE code called CRYSTAL, which isuda dedicated robust and accurate finite element solver. The implementation is based on lookup tables in combination withudfeed-forward neural networks. The radial return method is used to determine the material state during and after plasticudflow, however, it has been extended to cope with the stiff character of the partial differential equation that describes theudtransformation behaviour.