Estimation of the Plastic Zone Size from the Multi-Parameter/Generalized Form of Fracture Criteria on Various Mode I Geometries

Three cracked geometries loaded in mode I are investigated and the plastic zone size calculated. For estimation of the plastic zone size, two fracture criteria are used (Rankine and von Mises). Whereas the classical criteria give the same results (the stress intensity factor being identical for each geometry), the data from numerical simulations exhibit differences for various geometries. It is shown that the multi-parameter form of the criteria enables to obtain results that agree better to the numerical ones. Particularly, the Williams expansion is utilized for approximation of the stress components that serve as inputs for the fracture criteria. It is concluded that taking into account several more initial terms of the series can help to predict the plastic zone size more accurately.