Simulation of ductile behaviour of 20MnMoNi55 steel using unsaturated G(fr )values for short crack growth estimated by introduction of correction factor to critical fracture energy, G(fr)

摘要

Marie and Chapuliot proposed a new fracture parameter, critical fracture energy, G(fr), to characterise stable crack growth. The idea of critical fracture energy was re-investigated and it was found that the critical fracture energy is not a single valued parameter, when estimated for short crack growth. It was claimed that the values of G(fr) increases and then saturates to a single value when a large crack growth is reached. In the present work, it is found that the saturated value of G(fr) is the critical fracture energy, G(fr) and is a material property. However, the increasing unsaturated values of G(fr) obtained from ductile stretch is not a material property. Therefore, an attempt is made to introduce a correction factor to this saturated value of G(fr). The correction factor is found to be a function of saturated value of G(fr). (material property) CTOD and crack growth. The values of increasing G(fr )obtained, using this correction factor is then used to predict the load versus load line displacement curve which matches well with experimental load versus load line displacement curve. The work is carried out for different a/W ratios and for both half CT and full CT.