Numerical determination of stress intensity factors: J-integral and modified virtual crack closure technique

Abstract

Together with the development of numerical tools for stress-strain analysis, approaches to deal with fracture mechanics problems have been the object of continuous improvement. For linear-elastic fracture mechanics problems, the determination of Stress Intensity Factors (SIF) is available as a post-processing possibility in most commercial finite element software packages such as Ansys and Abaqus, allowing the users to perform straightforward assessments of cracked mechanical parts or structures. However, available techniques for SIF determination in post-processing of these commercial solutions are almost limited to the so-called displacement extrapolation and J-integral techniques. In the present work, the implementation of the J-integral technique is revised considering a new finite element software, labeled as Omicron. Furthermore, a more recent technique, the modified Virtual Crack Closure Technique (mVCCT) is also implemented and evaluated. For results assessment, finite element models were built in Omicron and SIFs were determined considering the J-integral and mVCCT approaches. From this study, it is concluded that the mVCCT implementation is simpler than the J-integral and it allows to determine accurately SIFs. Nevertheless, this technique is not straightly available in the current versions of the commercial packages for finite element modeling, which require separate post-processing for SIF determination.