Fatigue Crack Growth from Notches: A Numerical Analysis

Abstract

A numerical approach based on plastic crack tip opening displacement (CTOD) was followed to study fatigue crack growth (FCG) from notches. The identification of fundamental mechanisms was made considering notched and unnotched models, with and without contact of crack flanks. Di erent parameters were studied, namely, notch radius, crack length, stress state, and material. The notch increases the plastic CTOD, and therefore fatigue crack growth rate, da/dN, as expected. The reduction of notch radius increases da/dN but reduces the notch a ected zone. Ahead of the notch a ected zone, da/dN increases linearly with crack growth, with a rate that increases linearly with the plastic CTOD. The crack closure phenomenon has a dramatic e ect under plane stress conditions but a limited e ect on plane strain conditions. In the former case, the contact of crack flanks reduces substantially the e ect of notch radius and the size of the notch a ected zone. These trends are associated with the increase of crack closure level with notch radius. The material does not a ect the global trends, but the reduction of yield stress increases the level of plastic deformation and therefore da/dN. The e ect of material, and also of stress state, is mainly associated with crack closure.