Fracture analysis of a low pressure steam turbine blade

(in lingua inglese)

FEA predicts the local mean stress sm higher than 500 MPa at the edge of the turbine blade root in un-notched condition caused by the rotor speed. In notched condition, FEA showed that the pitting hole increased the local stress above yield. The spatial stress increase due to the pitting hole was larger than microstructure features, such as the prior austenite grain size. The superposition of Dsb causes the fatigue crack to grow from micro-structurally small to large.