Mechanism of fracture of aluminum blanks subjected to stretching along the sheared edge

The objective of this study was to investigate the mechanisms of fracture of aluminum blanks subjected to shearing and stretching along the sheared edge. In this study, a new imaging technique was implemented to track the stretching of the sheared edge until fracture. A 1 mm square grid was etched onto the sheared samples and a video of the sheared surface was taken incrementally during tensile test of the sample.The influence of cutting clearance in the trimming operation on sheared edge stretchability and mechanism of fracture of sheared surface during its stretching were investigated. Excessive plastic deformation of the burr area during the trimming operation was identified as a major factor leading to early fracture initiation from the tip of the burr. Deburring or solution heat treatment of samples trimmed with excessive clearance may increase stretchability to the level observed for the samples trimmed with accurate alignment of the tools. Roughening of the sheared surface produced with 5% cutting clearance did not have any significant effect on elongation of the sheared edge.Trimming process with scarp support eliminated burrs on the sheared edge for a large range of cutting clearances and substantially improved sheared edge stretchability.