In this paper, an enhanced numerical method for forming tool design optimisation in three-dimensional (3D) sheet metal forming applications is presented. The applied procedure enables a determination of appropriate forming tool geometry so that the manufacture of a sheet metal product inside specified tolerances would be ensured. In addition to the springback that occurs in the formed part after removal of the forming tools, the impact of the thinning of the sheet metal during the forming process is considered in the method, and both effects are correspondingly compensated for an iterative procedure. Computational efficiency in the E-DA-3D method is achieved mainly because the improved accuracy of the communicated data established corresponding interrelations between the discretised topologies used in the definition of the prescribed product geometry, the current tool geometry, and on this basis actually computed product geometry which is achieved by means of additional point topology mappings. The potential and effectiveness of the method is demonstrated by considering two cases of the forming tool design optimisation that are also experimentally validated.
COBISS.SI-ID: 13403419
The paper deals with constitutive modeling of highly anisotropic sheet metals and presents FEM based earing predictions in a round cup drawing simulation of highly anisotropic aluminum alloys where morethan four ears occur. For that purpose the BBC2008 yield criterion, which is a plane-stress yield criterionformulated in the form of a finite series, is used. Thus defined criterion can be expanded to retain more orless terms, depending on the amount of given experimental data. To be used in sheet metal formingsimulations the constitutive model, derived in accordance with the associated flow theory of plasticity,has been implemented in a general purpose finite element code ABAQUS/Explicit via VUMAT subroutine,considering alternatively different number of parameters in the BBC2008 yield criterion, where possiblenumber of parameters are any multiple of number 8. For the integration of the constitutive model theexplicit NICE (Next Increment Corrects Error) integration scheme has been used. The CPU time consumptionfor an explicit deep drawing simulation, which is based on the developed constitutive model,has been proven to be, due to effectiveness of the used integration scheme, fully comparable to theperformance experienced when the simulation is performed with ABAQUS built-in constitutive modelsand implicit integration schemes. Two aluminum alloys, namely AA5042-H2 and AA2090-T3, have beenconsidered for a validation of the constitutive model. The respective BBC2008 model parameters havebeen identified for both alloys with a developed numerical procedure, based on a minimization of thespecified cost function. For both materials, the simulation predictions based on the BBC2008 model proveto be in very good agreement with the experimental results. Further, in order to show the flexibility ofthe BBC2008 model in modeling of highly anisotropic sheet metal response, we have introduced a highlyanisotropic fictitious material which yields, according to the theory, twelve ears in cup drawing. As it isshown in the paper the BBC2008 model is able to predict twelve ears in cup drawing simulation with theformulation containing 16 parameters for anisotropy description only. The flexibility and accuracy of theconstitutive model together with the robust identification and integration procedure guarantee theapplicability of the BBC2008 yield criterion in industrial applications.
COBISS.SI-ID: 13311771
The paper presents a derivation of the consistent tangent operator (CTO) for the cutting-plane algorithm (CPA). For a class of plasticity models that are suitable to be integrated using CPA, an explicit recursive expression is analytically derived and is updated in each iteration of the CPA integration procedure to yield the final value of the CTO when the CPA is converged.
COBISS.SI-ID: 13311515