Relation between flange fracture and blankholder force in the process of cylindrical deep drawing of AZ31B rolled magnesium alloy sheets

The fracture occurring at the flange edge in the process of cylindrical deep drawing of AZ31B magnesium alloy sheets was investigated. The fractures were simulated under a uniaxial in-plane compression test to classify the fracture types while the blankholder force of the sheet was varied. Two types of fractures, out-of-plane shear fracture (OPSF), and in-plane shear fracture (IPSF), were observed. The fracture types changed from OPSF to IPSF as the blankholder force increased to a drawing ratio of approximately 1.5-1.6. This implies that the fracture type could be controlled by changing the blankholder force. The transition from OPSF to IPSF increased the fracture strain, because the out of plane buckling of the alloy sheets was suppressed by the blankholder force. The results confirmed that, in cylindrical deep drawing, the limiting drawing ratio could be increased by restraining the flange edge of the alloy sheets with the sufficient blankholder force.