抄録
The effects of stress state on ductility and fracture appearance in shear type ductile fracture of aluminium alloys 2017-T4, 5052-0 and a structural steel SM50B were investigated in comparison with those in fibrous ductile fracture. Thin walled cylindrical specimens were used for the tests under combined tension-torsion loading to obtain the shear fracture under various biaxial states of stress. Fractographic observation showed the micro-void nucleation and growth played an important role in shear fracture as well as in fibrous fracture. Ductility in shear fracture varied with the stress triaxiality (or the stress ratio of tension to torsion) and took a smaller value than in fibrous fractures. Shear fracture always occurs preceded by macroscopic shear band formation and the variation of ductility with stress triaxiality can approximately be explained by the micro-void nucleation and growth model in shear band. Whether the shear fracture precedes the fibrous fracture depends on the material and geometrical configuration of the specimen.
