A novel quadratic yield model to describe the feature of multi-yield-surface of rolled sheet metals

Since Hill’s quadratic yield model [Hill, R., 1948. A theory of the yielding and plastic flow of anisotropic metals. Proc. Roy. Soc. Lond. A193, 281–297] cannot address enough experimental results for fairly describing the “anomalous” yield behavior as observed in some of rolled sheet metals, a new quadratic yield model is proposed. As the concept of multiple yielding systems is introduced into the new quadratic yield model, seven commonly used experimental results, three uniaxial tension stresses, one equibiaxial tension stress and three strain ratios, can all be taken into account for characterizing the anisotropy of rolled sheet metals. If more experimental results are extra needed for further improving the prediction, this yield model is still workable. As the experimental parameters are defined as functions of loading direction of corresponding test separately from the major part of yield model, the increase of experimental results regarding the same test does not vary the quadratic form of yield model. The representation of this yield model with axes of principal stresses demonstrates the similar form to Hill’s quadratic model. Therefore, many previous studies developed from Hill’s quadratic yield model can be directly upgraded by the new model to reach a higher accurate level.