31 KB566 KB28 KB199920252008Halilovič, MiroslavŠtok, BorisVrh, Markoštevilka:4letnik:549 stranistr. 288-296ISSN:0039-2480COBISSID:10528795URN:URN:NBN:SI:doc-TALQXY9HenAssociation of Mechanical Engineers and Technicians of Slovenia et al.Zveza strojnih inženirjev in tehnikov Slovenije et al.Strojniški vestnikelastičnostpločevinapreoblikovanje kovinvlečenjeImpact of Young's modulus degradation on springback calculation in steel sheet drawing|The aim of the paper is to demonstrate, based on the results of respective numerical simulations of a drawing process, how springback of a steel sheet drawn part is affected by stiffness degradation, which results from the material damage evolved during the forming process. For the purpose of the presented paper the GTN (Gurson-Tvergaard-Needleman) damage constitutive modelcoupled with Mori-Tanaka approach has been implemented in ABAQUS/Explicitvia VUMAT user material subroutine, while integration of the constitutive model is performed with a numerical scheme developed recently by the authors. Parameters of the constitutive model are identified, for authenticity of the paper, from the measurement data obtained from classical tensile tests of cold rolled stainless steel EN 1.4301, as well as from the measured stiffness degradation, as a function of the plastic strain. From a comparative analysis of numerical results of the springback behaviour, investigated on the Demeri springback cup test under assumption of different constitutive models, it can be concluded, that stiffness degradation should be incorporated in simulations of sheet metal forming. Its influence on a predicted final shape of a steel sheet drawn part is namely too significant tobe neglectedPričujoč prispevek prikazuje vpliv upoštevanja zmanjšanja togosti v materialu,ki je posledica razvoja poškodbe med preoblikovanjem, na rezultate računalniške simulacije elastične povračljivosti globoko vlečenega izdelka. Za ta namen je GTN (Gurson-Tvergaard-Needleman) poškodbeni model, ki smo ga ustrezno nadgradili z Mori-Tanaka modelom, s pomočjo podprograma VUMAT vnesen v programsko kodo ABAQUS/Explicit. Integracija konstitutivnega modela je izvedena z numerično shemo, ki je bila nedavno razvita s strani avtorjev. Zaradi avtentičnosti studije smo identificirali parametre konstitutivnega modela iz rezultatov meritev običajnega nateznega preizkusa ter meritev zmanjšanja elastičnega modula za nerjavno jeklo EN 1.4301. Na osnovi izvedene primerjalne analize numeričnih rezultatov elastične povračljivosti lahko sklepamo, da je potrebno zmanjšanje togosti materiala vključiti v simulacije preoblikovanja pločevine. Vpliv le-te na izračunano končno geometrijo preoblikovanega izdelka je namreč prevelik, da bi ga smeli zanemaritiTEXTznanstveno časopisjejournalsSlovenian National E-content AggregatorNational and University Library of SloveniaUniverza v Ljubljani, Fakulteta za strojništvo