Modelling of anisotropic hardening behavior for the fracture prediction in high strength steel line pipes

• New yield function (M-Hill48) is proposed to represent steel anisotropic behavior.
• The function is calibrated by experimental tensile and torsion tests.
• New function has been included into a commercial finite element code.
• New function, can reproduce the steel hardening in different direction.
• New formulation provide a very good matching with small and full scale test.

With the aim of improving prediction capabilities of FE simulation of anisotropic materials, a new plasticity model is proposed, based on Hill(48) criterion. The model provides a 3D description of the anisotropic behavior to represent the ductile hardening in all directions up to fracture; a Lode angle effect is also introduced, which allows a description of shear stress states. The model has been implemented into a commercial finite element code and calibrated with dedicated experimental laboratory methodology for high grade steel pipelines. A preliminary validation of the plasticity model, on a full scale a pipe burst test, is also provided.