3. Inspection of the rotor fracture
Preliminary study of structure led to the view that fracture may have been caused by sharp corners,however, non-failed rotor structures also show similar structural features. Hence it is considered that the cause of failure was unlikely to be sharp corners alone, but their contribution to the failure cannot be underestimated due to presence of stress concentrations.
The rotor was broken up into four separate parts and did not bear any indication of fatigue crack growth when the fracture surface was examined, indicating that the failure was of a brittle type of fracture. As shown in Figs. 2 and 3, all fractures seem to start at a corner radius because of the high stress concentration at this