R. Matthews, A. Dey, Y. Zhao, VEXTEC, Brentwood, TN; R. Tryon, VEXTEC Corporation, Brentwood, TN

Summary:

Fatigue specimens were cut from a Waspaloy gas turbine rotor. All of the specimens were tested with the same cyclic loading. Eleven crack nucleation sites were identified and monitored during the test. One crack nucleation site was at an inclusion, the others appeared to be transgranular. The geometry of the surface microstructure in the vicinity of each of the crack nucleation sites was measured. The geometry included the size, shape, orientation and relative location the grains. A cellular automaton based finite element model of each crack nucleation sites was created and the local stresses were simulated. The stresses, including the shear stresses resolved onto the available slip systems, were investigated along with the sympathetic slip systems affect on misorientation within the crack nucleation neighborhood.