DETERMINATION OF THE CRITICAL EFFECTIVE STRAIN OF AA1050-O ALLOY TO PREDICT NECKING UNDER COLD PLASTIC DEFORMATION

The aim of this paper is to determine the strain hardening limit of aluminium alloy AA1050-O using the critical effective strain value as determined by the ductile fracture criterion proposed by Cockroft-Latham. A numerical simulation of the Erichsen cupping test using the Cockroft-Latham ductile fracture criterion was performed to predict the onset of necking. To verify the prediction of necking, an experimental procedure involving Erichsen necking tests until predicted necking, annealing, and subsequent Erichsen necking tests until sample destruction was performed. The simulation results predicted that necking would occur at a critical effective strain of 0.37, which corresponds to a critical Cockroft-Latham damage parameter of 0.53. By combining numerical simulations of the cold plastic deformation process with the experimental procedure and using the Cockroft-Latham ductile fracture criterion, the critical effective strain value of AA1050-O alloy can be determined.