Nucleation and growth of creep voids in circumferentially notched specimens

Several creep damage tests of pure aluminum were carried out using circumferentially notched bars, which can easily produce multiaxial state of stress near net section. The surface of notch root and longitudinal section with central axis were inspected to observe the growth of creep voids and cracks by means of scanning electron microscopy and optical microscopy. Experimental results show that: the maximum length of the largest creep void/crack on the notch surface can be expressed as an exponential function of lifetime ratio. This will help to predict residual lifetime of components with these notches. However, a great care is required not to miss the maximum creep defect, because only a part of creep voids and cracks appears on the surface of notch root and most of the creep defects lie inside the notch root.