This paper presents a finite element analysis of calculating stress intensity factors for Mode I, Mode II and mixed-mode planar fracture problems using the virtual crack extension technique. Results show that whilst the accuracy of the predicted stress intensity factors may be significantly improved upon by adding a small rosette around the crack tip, this improvement is strongly dependent on the size of the rosette. A new procedure is devised to estimate the stress intensity factors by using two calculations with different rosette sizes for a given mesh. The new method provides robust estimating ability, even for very coarse meshes.
Yang, J., Chen, JF., & Holt, GD. (2001). Efficient calculation of stress intensity factors using virtual crack extension technique. Computers & Structures, 79(31), 2705-2715. https://doi.org/10.1016/S0045-7949(01)00146-8