Fatigue failure of a centrifugal compressor

A single stage centrifugal type compressor failed during operation and a blade detached. Failure analysis was carried out to delineate the cause of the failure.Investigation shows that multiple fatigue cracks were generated during service from forging defects in the root area of the blade. When they grew to a critical size under (high cycle fatigue) HCF, the blade detached from the root in an over load manner. At the high rpm of the engine, the detached blade collided with other rotating part of the engine and entangled between the compressor and multiplier assembly. This resulted in the subsequent damage in the engine.