Investigation of Cracked Propeller Blades on an Icebreaker

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Authors
  1. Pussegoda, L.N.
  2. Malik, L.
Corporate Authors
Fleet Technology Ltd, Kanata ONT (CAN);Defence Research Establishment Atlantic, Dartmouth NS (CAN)
Abstract
Examination of two blades of a four bladed CP propeller, from the port shaft of an icebreaker that had through thickness fractures is discussed. The fractures propagated radially from the blade tip part way down the blade before arresting. The direction of the chevrons on the fracture surface indicated that the fracture initiation sites were located in the tip region of the blade. The other two port propeller blades with major portions lost in operation also had fracture initiation sites at the tip region. Metallography revealed that extensive multi-pass weld build up and weld repairs had been carried out in the blade tip regions. These regions also displayed lack of fusion and porosity type flaws. In the initiation region, the cracks propagated in stages displaying run-arrest events. The main through thickness crack did not occur until the crack propagation reached the un-refined as-cast microstructure. This is because of the superior toughness of the refined microstructure in the repair region. The fracture features of the initiation region in blade 1 demonstrated loading from both sides of the CP blade. This opened up the possibility of fatigue crack propagation in that region. Finally, recommendations and suggestions were presented aimed at avoiding such failures in the future.
Report Number
DREA-SR-1999-162-PAP-24 — CONTAINED IN CA000150
Date of publication
01 Oct 1999
Number of Pages
9
DSTKIM No
CA000174
CANDIS No
511898
Format(s):
Hardcopy;Document Image stored on Optical Disk

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