Surface flaw stress intensity factor computation with quarter-point elements

The stress intensity factor along the front of a semi-elliptical surface flaw subjected to tension or bending loading is calculated by means of a finite element analysis carried out with twenty node isoparametric three-dimensional elements. The stress and strain singular behaviour in the vicinity of the defect is modelled by moving the finite element midside nodes near the crack front to quarter-point positions. An extensive analysis is carried out by assuming different values of the flaw aspect ratio (0.2., 0.4, 0.6, 0.8, and 1.0), while the relative depth of the crack's deepest point is varied from 0.1 to 0.4. As regards the crack configurations previously tackled in the literature, the agreement between the results of the present study and those obtained by other authors is quite satisfactory, especially for small relative crack depths.