CAUSES OF FATIGUE FAILURE IN AN AEROENGINE COMPONENT

The retaining ring of an aero-engine failed in fatigue mode. Metallurg ical investigations revealed that there was a high density of inclusio ns in the material which are not deformable. During deformation, they disintegrated and formed voids which could act as sharp notches during fatigue loading. Axial surface cracks were visible on the surface of the ring. It is proposed, as found in previous failure analysis studie s, that surface cracks trap lubricants used during the drawing process of the wires, and carburize the region during subsequent annealing. T hese regions can also be potential sites of fatigue crack initiation. (C) 1997 Elsevier Science Ltd.