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고속변형률 조건을 고려한 단열전단밴드의 해석에 관한 연구
황두순(Doo Soon Hwang),이병섭(Byoung Seob Lee),윤수진(Su Jin Yun),홍성인(Sung In Hong) 대한공업교육학회 1999 대한공업교육학회지 Vol.24 No.2
Adiabatic shear band is widely observed in a plastically deformed body for a thermally rate-dependent material, especially at very high strain rates. The localized shear band stems from the evolution of a narrow region in which intensive plastic flow occurs. The shear band often plays as the precursor of ductile fracture during a forming process. The objectives of this study is to investigate the localization behavior and predict the failure by using numerical method. Because of the ease of convergence and the numerical stability, the implicit finite difference scheme is employed in this work. This study considered an isotropic hardening as well as thermal softening as a deformation behavior of material. Furthermore, this paper suggests that a kinematic hardening constitutive equation should be required to predict more accurate strain level wherein a shear band occurs.
이병섭,황두순,홍성인 충남대학교 산업기술연구소 2003 산업기술연구논문집 Vol.18 No.1
It is difficult to predict material behavior of forming process, because the plastic instable flow happens in practical forming process, i. e. upsetting, backward extrusion, piercing, indentation. In view of the direct relationship between material flow and defects of the products, we should find out its mechanism. In this study, we introduced the plastic spin and the kinematic hardening and considered the kinematic hardening constitutive equation for rate-dependent material. Also analysis of upset forging is carried out using the rigid plastic FEM with Al7075. Then, the results from the numerical analysis shows that kinematic hardening model results in more significant strain localiztion than isotropic hardening model.