Brittle Torsional Fatigue Crack Initiation in an Otherwise Ductile Environment.

摘要

The results of a torsional fatigue test program on marage 250 steel indicate that the usual fatigue failure mechanism occurs as a flat ductile fracture along the cross section of the test specimens. However, a small number of specimens displayed a small penny-shaped crack on the outer surface at a 45-degree helix, typical of brittle torsional failure, before the final ductile failure. Scanning electron microscope examination showed that the brittle failure was caused by a brittle inclusion on the outside surface of the specimen. Keywords: Titanium. (aw)