Fatigue growth of three dimensional cracks in an elbow

In the assessment of structural integrity and the analysis for damage tolerance of structures, the calculation of fracture parameters for three-dimensional cracks remains as an important task because they occupy majority of cracks generated in the industrial field. The finite element alternating method (FEAM) has been presented and used effectively to solve two and three dimensional crack problems. The method alternates between the FEM solution for a finite body without a crack and the solution for a crack in an infinite body. Nikishkov, Park and Atluri presented another FEAM procedure, in which the crack solution for an infinite body is obtained by using the symmetric Galerkin boundary element method (SGBEM). By using the methods, the analysis of three-dimensional planar or non-planar cracks embedded in an infinite or a finite body can be performed more efficiently and more accurately. And the FEAM is particularly efficient for modeling of fatigue crack growth since the finite element mesh for the uncracked body and the boundary mesh for the crack are completely independent. In this paper, with the use of the proposed procedure the stress intensity factors are calculated about some of three dimensional cracks embedded in infinite and finite body. And the stress intensity factors for arbitrarily shaped three-dimensional cracks are calculated to simulate the crack growth