Procedure:
- The rotor was visually inspected and photo documented.
- The rotor was cut so that the fracture face could be visually inspected.

Conclusion:
The primary cause of failure was the residual stress state induced by terminating two welds in close proximity.  This close placement of the termination points created a tensile stress in the shaft.  Poor penetration of the welds was also exhibited, which acted as a stress riser.

Figures 1 and 2  – Visual inspection of the fracture face indicated that the fracture initiation site occurred between two weld termination points. Top View followed by Side View of weld zone.