Mixed mode crack propagation in cold drawn tubes subjected to torsional fatigue

摘要: In a previous work by the authors, torsional fatigue of micronotched - cold drawntubes had been analized. Specimens with longitudinal shallow notches showed adominant mode III propagation ( throughout tube thickness) even if I (at thedefect edges) was present. Indeed, II crack along axis wasobserved in second stage.In this work, reason for peculiar is furtherinvestigated. particular, relationship between some ‘equivalent’ stress intensityfactors proposed literature and growth rates analysed. With aim,alternating tests have carried out on notched tubularspecimens, being trough-thickness both transversedirection, order to analyse possible influence material anisotropy.Mixed pure paths observed. The wereanalysed through FE analysis actual intensity factorand discussed.