Stress intensity factor predictions: Comparison and round-off error

Practical steps required to obtain robust finite element triangular meshes for crack path and stress intensity calculation purposes are evaluated, and techniques to use their predictions to calculate fatigue lives, including load interaction effects, are discussed. These steps address: (a) how to simulate efficiently 2D crack paths under bi-axial loading using automatic remeshing schemes; (b) how to choose the best method to calculate stress intensity factors along the crack path; and (c) how the numerical problems associated with excessive FE mesh refinement along the crack path may affect predictions. Various modeling strategies are compared using different crack geometries and mesh refinements to quantify their performance, particularly when the elements around the crack tip are very small compared with the elements far from it. It is shown that, contrary to many other stress analysis applications, excessive mesh refinement may significantly degrade the calculation accuracy in crack problems. A limit for the elements size ratio is clearly established.