The paper deals with constitutive modelling of highly anisotropic sheet metals. It presents FEM based earing predictions in cup drawing simulation of highly anisotropic aluminium alloys where more than four ears occur. For that purpose the BBC2008 yield criterion, which is a plane-stress yield criterion formulated in the form of a finite series, is used. Thus defined criterion can be expanded to retain more or less terms, depending on the amount of given experimental data. In order to use the model in sheet metal forming simulations we have implemented it in a general purpose finite element code ABAQUS/Explicit via VUMAT subroutine, considering alternatively eight or sixteen parameters (8p and 16p version). For the integration of the constitutive model the explicit NICE (Next Increment Corrects Error) integration scheme has been used. Due to the scheme effectiveness the CPU time consumption for a simulation is comparable to the time consumption of built-in constitutive models. Two aluminium alloys, namely AA5042-H2 and AA2090-T3, have been used for a validation of the model. For both alloys the parameters of the BBC2008 model have been identified with a developed numerical procedure, based on a minimiyation of the developed cost function. For both materials, the predictions of the BBC2008 model prove to be in very good agreement with the experimental results. The flexibility and the accuracy of the model together with the identification and integration procedure guarantee the applicability of the BBC2008 yield criterion in industrial applications.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 12130075The paper focuses on a reliable identification of the hardening curve of sheet metal after the onset of necking by means of a purposely developed shear test. The main comparative advantage of the test is its simple implementation needing no further development of the experimental equipment used in standard tensile testing. In addition, in order to achieve more flexible hardening curve description from those given by the classical analytical hardening laws, the paper presents the hardening curve approximation based on the cubic spline technique. The identified hardening curves are validated and compared to the analytically extrapolated ones obtained by a continuation of classical hardening laws for large plastic strain. It is shown, that due to large difference in response the analytical extrapolation is seriously disputable.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 11923739The aim of this work is to present a modelling approach to thermo-mechanical analysis of the solidifying shell in the primary zone, as met in thin slab continuous casting process with the mould of non-constant cross-section subjected to oscillation. The thermo-mechanical problem considered in the Eulerian reference frame is treated as uncoupled, with the temperature and stress-strain fields being steady-state and cyclic steady-state, respectively. For validation of the developed numerical model the respective process simulation results are compared with the available measurements. Considering that great capability of the model in achieving a better physical insight into the complex thermo-mechanical behaviour in continuous casting is confirmed, the model can be used not only for direct analysis purposes, but above all for an advanced technology design involving a process parameters prescription and the mould's internal geometry determination, as well as corresponding optimization tasks.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 11992091