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금속 성형 공정의 준정적 변형 예측을 위한 외연적 시간 적분 유한 요소법의 적용에 대한 연구
유요한,양동열,Yoo, Y.H.,Yang, D.Y. 한국정밀공학회 1995 한국정밀공학회지 Vol.12 No.12
In the analysis of metal forming problems, the explicit time integration finite element method, which does not have convergence problems, is frequently used. The present work is to assess the applicability of the explicit time integration finite element method to quasi-static metal forming problems. Compressing analyses of thin-walled tubes and solid cylinders are performed with different loading velocities. The computed buckled profiles of thin walled tubes are compared with the theoretical and experimental ones and it is found that at sufficiently low loading velocity, the explicit time integration finite element method accurately predict quasi-static buckled profiles. When loading volocity is increased, the computed buckled profiles of thin-walled tubes are very sensitive to loading velocity however the computed profiles of solid cylinders are less sensitive to loading velocity. In orther words, the geometrically self-constrained specimens like solid cylinders are less sensitive to loading velocity than the geometrically unconstrained specimens like thin-walled tubes. As a result, it is found that the geometrically self-constrained problems which include the greater part of metal forming problems can be efficiently analyzed with loading velocity control technique.
유요한,전기영,정동택,Yoo, Y.H.,Jeon, G.Y.,Chung, D.T. 대한기계학회 1993 대한기계학회논문집 Vol.17 No.7
The stepped specimen which is subjected to step loading is modeled to study the initiation and growth of adiabatic shear band using explicit time integration finite element method. Three different clearance sizes are tested. The material model for the stepped specimen includes effects of strain hardening, strain rate hardening and thermal softening. It is found that the material inside the fully grown adiabatic shear band experiences three phase of deformation, (1) homogeneous deformation phase, (2) initiation/incubation phase, and (3) fast growth phase. The second phase of deformation is initiated after sudden shear stress drop which occurs at the same time regardless of the clearance size. The incubation time prior to fast growth phase increases, as the clearance size of the stepped specimen increases. Whereas, after incubation period, the growth rate of the adiabatic shear band decreases, as the clearance size decreases. It is also found that two adiabatic shear band may develop instead of one for the smaller clearance size.
다시 태어나 태초로 돌아가기: 소설 『채식주의자』의 원형적 신화 주제 분석
유요한 한국문학과종교학회 2019 문학과종교 Vol.24 No.1
This article articulates mythic ideas suggested in Han Kang’s novel The Vegetarian by analyzing the novel in detail and comparing it with some traditional myths and literary works. The novel develops the two paradigmatic mythic themes of “breaking away from the messy present and returning to the mythic time of the beginning” and “rebirth on a higher level of existence.” Yeong-hye, the heroine of the novel, exerts every effort to escape from a daily life that is filled with violence, suppression and hypocrisy, and to recover the ideal state of the mythic beginning in which animals and humans coexisted harmoniously and human lives were organically united to those of plant. Her desperate endeavors to become a strict vegetarian and later to be a tree can be interpreted as attempts to have her former mode of being die and to be born again as a new being, for which humans have sought persistently for ages through myths. 이 논문은 소설 『채식주의자』를 세밀하게 분석하고 여러 전통신화 및 문학작품들과 비교하여 이 작품에 담겨있는 신화적 사고를 드러낸다. 특히 『채식주의자』의 바탕에 자리 잡고 있는 ‘부조리한 현재를 벗어나 태초의 신화적 시간으로 회귀하기’ 및 ‘죽음을 통해 새로운 존재로 다시 태어나기’라는 두 개의 원형적인 신화 주제에 초점을 맞춘다. 소설의 주인공 영혜는 폭력과 억압이 당연하게 여겨지는 일상을 벗어나, 동물과 인간이 평화롭게 공존할 뿐 아니라 식물과 인간의 생명이 유기적으로 연결되어 있던 신화적 태초를 회복하고자 한다. 영혜가 채식주의자가 되고 나아가 나무가 되고자 하는 처절한 노력은 ‘이전의 존재 양태는 죽고 새로운 존재로 거듭나고자 하는 시도’로 해석될 수 있으며, 이는 인간이 오랜 세월 동안 신화를 통해 천착해왔던 주제이기도 하다. 나무가 되고자 하는 영혜의 갈망은 인간의 생명이 초목에서 유래했고 또한 죽어서 초목이 될 수 있다는 신화적 사고를 계승하고 있다.
관성효과가 고려된 강소성 유한요소법을 이용한 고속변형해석
유요한,박근,양동열,Yoo, Yo-Han,Park, Khun,Yang, Dong-Yol 대한기계학회 1996 大韓機械學會論文集A Vol.20 No.5
The rigid-plastic finite element formulation including the inertia force is derived and then the rigid-plastic finite elemnt program considering the inertia effect is developed. In order to consider the strain hardening, strain rate hardening and thermal softening effects which are frequentrly observed in high-velocity deformation phenomena, the Johnson-Cook constitutive odel is applied. The developed program is used to simulate two high-velocity deformation problemss ; rod impact test and hdigh-velocity compression precess. As a result of rod impact test simulation, it is found that the siulated result has a good agreement with the experimental observation. Through the high-velocity compression process simulation. it is also found that the accuracy of the simulated results is dependent upon the time increment size and mesh size.