A phenomenological form of the q2 parameter in the Gurson model

Continuum damage mechanics is applied to compute fracture J-initiation and the J-resistance (J-R) curve for SA333 Gr.6 carbon steel material. A parametric study is carried out to assess the effects of variation of Gurson material parameters on the J-R curve. A difficulty is experienced to obtain a set of Gurson parameters that can compute J-initiation as well as the entire J-R curve close to the measured values. It has been found that a phenomenological form of the q2 parameter, used in the Gurson constitutive model, based on experimental observation helps to overcome this difficulty. The new form of q2 has an exponential spatial variation near the crack tip and has two constants. These additional constants help analysts to compute the complete J-R curve (including J-initiation) close to experimental data. The same set of constants has also been found to be useful for other fracture specimens, materials and two piping components of a nuclear plant.