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Fracture behaviour of aluminium alloy sheet under roller hemming process

Abstract Roller hemming is a tendency for hemming flexibility. While for aluminium alloy sheets, fracture happens easily. According to comparison of flat surface straight line flanging and limit strain under necking theory, the failure mode of aluminium alloy sheet under roller hemming is ductile fracture, with the aid of analysis of cross-section of the fracture location. Then ductile fracture criterion critical parameter is determined by simulation and experiments of uniaxial tensile test. Consequently, forming limit strain curve at fracture could be calculated from the assumptions including stress–strain curve, plane-stress condition, linear strain path, Deformation Theory of Constitutive Equation, Cockcroft–Latham fracture criterion, etc. Finally, the feasibility of ductile fracture criterion and bending effect on roller hemming process are analysed.