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롤피어싱 공정에서 발생하는 Mannesmann 효과의 정량화
이장호(J. H. Lee),조재민(J. M. Cho),정승원,문호근(H. K. Moon),전만수(M. S. Joun) 한국소성가공학회 2014 한국소성가공학회 학술대회 논문집 Vol.2014 No.5
Mannesmann effect is studied, analyzing a hole expansion phenomenon in artificial roll piercing of a hollow cylindrical material by two barrel-type rolls without any mandrel and guiding tools. A rigid-thermoviscoplastic finite element method is employed with a special mesh generation scheme which can control the mesh density especially on the small hole surface. No damage model is used to soften the material and the hole expansion simulation is conducted without any additional assumptions about material and process. Artificial roll piercing processes for a wide range of hole diameters with outer diameter fixed are simulated with emphasis on hole expansion. It has been shown that the hole expansion ratio of the maximum hole diameter to the initial hole diameter increases as the initial hole diameter decreases, indicating that the hole expansion phenomenon is next to the Mannesmann effect occurring in actual roll piercing. It has been also shown that the hole expansion is related to the cavity formation occurring just after the material passes the mandrel nipple, which leads to the decrease in the pushing force exerted on the mandrel in an actual roll piercing process.
엄재근(J. G. Eom),이민철(M. C. Lee),이장호(J. H. Lee),최영길(Y. G. Choi),김동환(D. H. Kim),전만수(M. S. Joun) 한국소성가공학회 2015 한국소성가공학회 학술대회 논문집 Vol.2015 No.5
In this paper, finite element prediction of die wear is conducted using non-isothermal finite element analysis of an actual hot forging process for a commercialized crankshaft. The Archard wear model with a law of hybrid friction is utilized. The non-isothermal finite element method is employed and the predictions are also compared with isothermal finite element predictions with emphasis on the metal flow lines.
이광휘(K. H. Lee),김동환(D. H. Kim),정승원(S. W. Jeong),이장호(J. H. Lee),전만수(M. S. Joun) 한국소성가공학회 2016 한국소성가공학회 학술대회 논문집 Vol.2016 No.4
An approach to non-steady-state prediction of temperature in drawing of a long tube/pipe with high accuracy is presented in this paper. A fine mesh system near the contacting area is employed to keep appropriate contact between material and dies, which is of great importance because contact region is inherently quite small in tube/pipe drawing. Once the end of refined mesh region passes a certain point located at before the deformation effective region, a new refined mesh system is generated by a special remeshing scheme. During remeshing, the entry region is rebuilt with initial material while the material at the exit side which is far away from the deformation effective region. An application example is given, which shows the characteristics of the presented scheme.
4각 딥드로잉 클래드판재 성형공정의 탄소성 유한요소해석
이민철(M. C. Lee),홍석무(S. M. Hong),황지훈(J. H. Hwang),심재원(J. W. Sim),이장호(J. H. Lee),정완진(W. J. Chung),전만수(M. S. Joun) 한국소성가공학회 2015 한국소성가공학회 학술대회 논문집 Vol.2015 No.5
In this paper, three-dimensional elastoplastic finite element approach to simulating a clad-metal sheet metal forming process is presented. The approach is based on a layered finite element mesh system with tetrahedral elements and a force imposing die to deal with blanking holder force. The predictions are compared with experiments, revealing that they are in a good agreement with each other.
금형의 탄성변형을 고려한 포트홀 압출공정의 유한요소해석
정석환(S. H. Chug),이장호(J. H. Lee),이민철(M. C. Lee),전만수(M. S. Joun) 한국소성가공학회 2016 한국소성가공학회 학술대회 논문집 Vol.2016 No.4
In this paper, non-steady state finite element simulation of a porthole extrusion process for manufacturing a radiation pipe under isothermal assumption is conducted with emphasis on effect of elastic deformation of dies. Effect of die elastic deformation on forming load and deformed shape of material is investigated, revealing that consideration of die elastic deformation is inevitable for precision or optimized die orifice design in extrusion of aluminum bars with complicated cross-sections. It is shown that extrusion simulation considering die elastic deformation is numerically stable, compared with forging simulation. It is, of course, due to steady-state behavior of forming load in extrusion.