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가이드 롤의 모델링 및 이를 이용한 링롤링 공정의 해석
진호태(H. T. Jin),김경률(K. R. Kim),김응주(E. J. Kim),최무호(M. H. Choi),전만수(M. S. Joun) 한국소성가공학회 2015 한국소성가공학회 학술대회 논문집 Vol.2015 No.5
In this paper, a ring rolling simulation technique based on full three-dimensional model discretized by tetrahedral elements with emphasis on a new guide roll model is presented. The new guide roll model is devised to reflect spring-like behaviors in real situations. The technique is assisted by a powerful mesh system specialized optimally for ring rolling simulation and parallel processing technique to reduce computational time and applied to an artificial profile ring rolling process modified from a real ring rolling process.
그립의 기능을 강조한 롤단조 공정의 유한요소모델링 및 적용
진호태(H. T. Jin),남태현(T. H. Nam),강석순(S. S. Kang),전만수(M. S. Joun) 한국소성가공학회 2016 한국소성가공학회 학술대회 논문집 Vol.2016 No.4
In this paper, a finite element model of grip in roll forging is presented, which is believed to have a deep influence on both finite element predictions and real process. A fraction of roll separating force is exerted on the front end of the material to be pulled. The pulling force during forming is considered as surface traction at the end. Effect of the pulling force is examined, revealing that the predictions of final length and major deformed region have a distinct function of the fraction of the pulling force with respect to the roll separating force, which can be a characteristic property of the process. The approach is applied to aluminum roll forging of manufacturing an optimized perform for a stepped bar.
진호태(H. T. Jin),최상도(S. D. Choi),전만수(M. S. Joun) 한국소성가공학회 2015 한국소성가공학회 학술대회 논문집 Vol.2015 No.10
In this paper, experimental and numerical study on cold forging of an aluminum auto part is conducted to identify a proper conditions for the process. The flow stress of the material is obtained by a tensile test based material identification algorithm and the frictional condition is also evaluated by a compression test. The experimentally obtained conditions are used to simulate a complicated three stage cold forging process of an aluminum auto part for a truck, which has some region of free surface. The predictions are compared with experiments in terms of shape.
유동응력, 마찰, 온도, 속도 등이 단조 중 단류선의 유한요소예측에 미치는 영향
최무호(M. H. Choi),진호태(H. T. Jin),전만수(M. S. Joun) 한국소성가공학회 2014 한국소성가공학회 학술대회 논문집 Vol.2014 No.10
In this paper, effect of flow stress, friction, temperature and velocity on finite element predictions of metal flow lines in upsetting. An actual three-stage hot forging process involving an upsetting process is utilized and experimental metal flow lines are employed to study the effect. It has been found that appropriate friction, temperature and velocity has little influence on metal flow lines located especially deep inside material but that flow stress has direct influence on them and a pure power law cannot reflect the real flow stress of hot material because it underestimate the flow stress around the dead-metal zone. It is thus recommended that a proper bottom limit of flow stress be assumed to deviate from the problem.
남찬희(C. H. Nam),진호태(H. T. Jin),손일헌(I. H. Son),전만수(M. S. Joun) 한국소성가공학회 2014 한국소성가공학회 학술대회 논문집 Vol.2014 No.10
In this paper, two-dimensional finite element approach of prediction the plastic deformation of tiny pinhole defects on the initial bloom surface, which were formed during continuous casting process of the base material of bloom. The initial pinhole shapes of which plastic deformations are to be traced are assumed V-shaped and U-shaped. Two different kinds of pass schedule of consecutive rolling stages are assumed to investigate the defect closing or lapping behaviors, i.e., one pass schedule of two forward rolling stages and another pass schedule of reverse rolling stage after forward rolling stage. The dimensions of the processes and the sizes of pinholes are also assumed to reflect the actual three-dimensional rolling processes. It has been shown that most plastic deformation occurs at the entry side and lapped or closed defects slightly open when they pass through the exit side. It is noteworthy that the reverse rolling decreases the lapped defect formed in the previous pass, implying that there exists an optimized pass schedule design to minimize the surface defect.