Abstract
The forming limit curve (FLC) is used in sheet metal forming analysis to determine the critical strain or stress values at which the sheet metal is failing when it is under the plastic deformation process, e.g. deep drawing process. In this paper, the FLC of the AA6061-T6 aluminum alloy sheet is predicted by using a micro-mechanistic constitutive model. The proposed constitutive model is implemented via a vectorized user-defined material subroutine (VUMAT) and integrated with finite element code in ABAQUS/Explicit software. The mechanical behavior of AA6061-T6 sheet is determined by the tensile tests. The material parameters of damage model are identified based on semi-experience method. To archive the various strain states, the numerical simulation is conducted for the Nakajima test and then the inverse parabolic fit technique that based on ISO 124004-2:2008 standrad is used to extracted the limit strain values. The numerical results are compared with the those of MK, Hill and Swift analytical models.
Highlights
O ver many years, the aluminum alloy sheets was widely applied in automotive and civil industries because of their outstanding advantages in high strength and light weight
The forming limit curve (FLC) curve is usually predicted by the Marciniak-Kuczynski (M-K) theory model [1] that based on an inconsistency in sheet
The parameters q1, q2 are proposed by Tvergaard and Needleman [12], n is hardening exponent of matrix material, e is Hill’48 equivalent stress, f * is function of void volume fraction (VVF), ij is delta Kronecker
Summary
O ver many years, the aluminum alloy sheets was widely applied in automotive and civil industries because of their outstanding advantages in high strength and light weight. Beside the FLC theory prediction, the Nakajima deep drawing model is applied widely in experiment and numerical simulation to determine the forming limit curve. The Nakajima test is usually conducted for the several specimens to find the various strain paths that presents forming response of material from uniaxial to biaxial stretched loading state. In this method, the limit strains are determined by an inverse parabolic fit [2, 3] or time-dependent technique [2, 4] at or after the onset of necking. The present results are compared with the those of theory FLC models
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