Stress intensity factors in a hollow cylinder containing a circumferential semi-elliptical crack subjected to combined loading

The problem of mixed mode fracture induced by a semi-elliptical circumferential crack lying at the outer surface of the cross-section of a hollow cylinder is considered. The cylinder is under the action of axial force, bending moment and torsion. To make the results comprehensive, dimensionless analysis is used, and a large variation limit of parameters that define the crack geometry is considered. Because of the advantages of the sub-modeling technique in problems which need very high mesh density, this method is used. Stress intensity factors in mixed mode condition are determined using three-dimensional finite element modeling with 20 node-isoparametric elements and the singular form of these finite elements at the crack front. The obtained results show to be in good accordance with those cited in the literature for the cases of separate application of axial load and bending moment. However, when torsion is added to tension and bending moment, a non-symmetrical distribution of stress intensity factor along the crack front is observed which can cause non-symmetric fatigue crack propagation.