Effect of residual stresses on crack shape of corner cracks at holes in nickel base superalloys

The main objective of this paper is to study the crack shape evolution in double-U and central hole specimens with corner cracks, both representative of gas turbine discs in terms of critical zones with stress concentrations. An automatic crack growth technique is employed, consisting of a three iterative steps: 3D finite element analysis, K calculation and crack propagation. Complementary experimental work was developed in RR1000, a nickel base superalloy applied in turbine disks, in order to obtain crack shapes and fatigue crack growth at elevated temperature. The effect of residual stresses on crack shape is investigated.