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

Abstract 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.

[1]  Geraint Williams,et al.  Hole Expansion of Aluminum Alloys for the Automotive Industry , 2011 .

[2]  M. Worswick,et al.  Edge Formability and Material Characterization of Hot-Rolled Multiphase Steels , 2014 .

[3]  Sergey Fedorovich Golovashchenko,et al.  Quality of Trimming and its Effect on Stretch Flanging of Automotive Panels , 2008 .

[4]  Sutasn Thipprakmas,et al.  An investigation of step taper-shaped punch in piercing process using finite element method , 2008 .

[5]  Sergey Fedorovich Golovashchenko,et al.  Analysis of sheared edge formability of aluminum , 2014 .

[6]  Ming Li,et al.  An experimental investigation on cut surface and burr in trimming aluminum autobody sheet , 2000 .

[7]  C. Chiriac,et al.  A Study of the Plastic Deformation of Sheared Edges of Dual Phase 780 Steel , 2010 .

[8]  J. Hatch,et al.  Aluminum: Properties and Physical Metallurgy , 1984 .

[9]  T. Wierzbicki,et al.  A new model of metal plasticity and fracture with pressure and Lode dependence , 2008 .

[10]  W. Johnson,et al.  Paper 5: Further Experiments in Quasi-Static and Dynamic Blanking of Circular Discs from Various Materials , 1965 .

[11]  Taylan Altan,et al.  Material fracture and burr formation in blanking results of FEM simulations and comparison with experiments , 1996 .

[12]  A. Konieczny,et al.  On Formability Limitations in Stamping Involving Sheared Edge Stretching , 2007 .

[13]  Sergey Fedorovich Golovashchenko,et al.  A study on trimming of aluminum autobody sheet and development of a new robust process eliminating burrs and slivers , 2006 .

[14]  Michael J. Worswick,et al.  Predicting Failure during Sheared Edge Stretching Using a Damage-Based Model for the Shear-Affected Zone , 2013 .

[15]  S. Sriram,et al.  Sheared Edge Characterization of Steel Products used for Closure Panel Applications , 2006 .