Numerical simulation of sheet metal blanking based on fully coupled elastoplasticity-damage constitutive equations accounting for yield surface distortion-induced anisotropy

This paper deals with the numerical simulation of sheet metal blanking process based on fully coupled elastoplastic model accounting for the induced anisotropies due to the kinematic hardening and the yield surface distortion. The yield surface distortion is assumed to be controlled by the kinematic hardening leading additional extra hardening which enhances the predictive capabilities of the model. Series of finite element-based numerical simulations of blanking process with four kinds of assumed distortional hardening parameters have been conducted. Through the comparison between the experimentally observed responses and the numerically predicted ones with and without the yield surface distortion effect, the significance of the yield surface distortion-induced anisotropy on the estimation of the blanking edge quality has been investigated.

Multiaxial ratcheting modeling with incorporation of a yield surface distortion model

Correct determination of ratcheting strain is very important in cyclic loading. A new simple yield surface distortion model is presented and its effect on cyclic loading and ratcheting prediction is investigated in this research. Model of Baltov and Sawczuk was modified in order to be able to consider directional distortion of the yield surface. Movement of the yield surface center is modeled by Chaboche's nonlinear kinematic hardening model. Isotropic hardening was also considered. A triangular function is used and necessary cyclic plasticity relations are developed. Convexity of the proposed model is discussed and verified. Performance of the proposed model in ratcheting strain prediction is investigated in multiaxial non proportional loadings under different paths. Experimental results with stress, strain and combined stress-strain control paths are compared with the proposed model results. Incorporation of the yield surface distortion of this new model, predicts better ratcheting strain for different stress, strain and stress-strain paths.

Using of Anisotropic Continuum Damage Mechanics to Describe Yield Surface Distortion

In this paper, yield surface distortion was studied by considering the combination of nonlinear kinematic hardening model of Chaboche and a new anisotropic continuum damage evolution model. The constitutive relations for anisotropic damage of elastoplasic materials were developed based on irreversible thermodynamics. The internal state manifold which consists of internal variables to specify the thermodynamic state of solids was described by a 2nd rank symmetric damage tensor, the kinematic hardening tensor and tensor of movement of damage potential surface. In order to describe the damage state, the fictitious continuum domain was considered and the consistent relations between real and fictitious domains were developed. It was indicated that the combination of the Chaboche’s model and model of anisotropic continuum damage leads to the well description of the subsequent yield surface.