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Description
The Yoshida-Uemori model is a combined hardening model coupled with the elastic evolution modulus which depends on the equivalent plastic strain. This model is implemented in the most used FEA stamping codes with occasionally some variations in the form of material cards. The material cards are requested regularly by the car manufacturers, in order to get a more accurate prediction of springback by numerical simulation, when compared to the prediction with a purely isotropic hardening mode. ArcelorMittal can provide material cards to its customers, thanks to an in-house methodology to identify the Yoshida-Uemori parameters in a very precise and robust manner.
The method used for the identification of the two material parameters governing the evolution of the elastic modulus can be further improved. The method is based on the use of experimental data coming from hysteresis loops conducted between 0.2% of plastic deformation and uniform elongation (Uel). During the unloading path of the loop, the force decreases until 5N. Several methods for defining the unloading elastic module have been tested and evaluated in this paper:
- Today, the elastic modulus is the slope deducted from the linear regression on all points of unloading path.
- The elastic modulus is the slope deducted from the linear regression on a part of unloading path.
- The elastic modulus is the chord modulus