M. A. da Fonte  M. M. de Freitas       

Anales de la Mecánica de la Fractura, nº 13 . 1996 . Pág. 357 -362
Ver (.pdf): Anales13-060

Resumen: This paper presents a study about the propagation of semi-elliptical surface cracks in round bars subjected to the rotating and reversed bending combined with steady torsion. Tests were performed on two different fatigue machines: one does carry out rotating bending and another one reversed bending, both combined with steady torsion. Cylindrical specimens of DIN CK45k steel were used. Test results were compared in these different loading conditions. A significant reduction of crack growth rates is obtained for the same mixed mode (.ó.K1 + Km) load conditions. It has been suggested that crack growth phenomena can be related with the crack closure effect as result of rubbing between surface cracks and abrasion debris, giving rise to the plastic zone size at the crack front due to the mode III effect. This work hopes to give a contribute for a better understanding fracture mechanisms associated to the steady mode III loading in order to obtain an accurate fatigue lifetime prediction for precracked shafts.

Localización: Luso, Portugal

Departamento de Máquinas Marítimas, Escola Náutica, 2780 Oeiras, Portugal.
ICEMS, Instituto Superior Técnico, Av. Rovisco Pais, 1096 Lisboa Codex, Portugal.