Fracture mechanics of the three-dimensional crack front: vertex singularity versus out of plain constraint descriptions

The effect of a free surface on stress distribution along the three-dimensional crack front is discussed. Generalized stress intensity factor methodology and out-of-plane constraint based procedure are used for a reliable estimation of the stress state in front of the crack tip. The two present methodologies are discussed and compared. The out-of plane, in-plane constraint parameters and generalized stress intensity factor were estimated. It is shown significant changes of the singularity exponents and fracture parameters values close to the free surface. Therefore, conventional methodologies can lead to inaccurate description of the stress state and cannot be used for reliable description of fatigue crack propagation in this area. (C) 2010 Published by Elsevier Ltd.