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윤정환(Yoon, Jeong Whan) 한국소성가공학회 2018 박판성형 심포지엄 Vol.2018 No.3
∙ Constitutive Models should consider both r-value and stress directionalities for accurate prediction of anisotropy. ∙ PEPS diagram can correct the offset from nonlinear strain path in forming limit and can be applied for surface crack. ∙ Stress-based forming limit and fracture model can be successfully used for general fracture applications. ∙ Mean stress contribution in M-C model gives very good correlation with observed experimental data.
김경진(Kyung-Jin Kim),윤정환(Jeong-Whan Yoon),양동열(Dong-Yol Yang) Korean Society for Precision Engineering 2015 한국정밀공학회지 Vol.32 No.11
Recently, the change of mechanical properties and microstructural evolution during severe plastic deformation (SPD), such as Equal Channel Angular Extrusion (ECAE), has been the subject of intensive investigation because of the unique physical and mechanical properties of severely deformed materials. In this study, two types of ECAE processes were considered, dies with intersection angles Φ of 90° and 120°, using experiments and simulations. The decoupled method, in which the rigid-plastic finite element method is incorporated with the rate-independent crystal plasticity model, was applied to predict the texture evolution in commercially pure aluminum during the ECAE processes with 120° and 90° dies. The simulated textures were compared with a measured texture via an EBSD OIM analysis. The comparison showed that the simulated textures generally were in good agreement with the experimentally measured texture.
강소성 가공 공정을 이용한 튜브 형상 재료의 결정립 미세화에 대한 연구
김경진(Kyung-Jin Kim),윤정환(Jeong Whan Yoon),양동열(Dong-Yol Yang) 대한기계학회 2009 大韓機械學會論文集A Vol.33 No.10
A unique process was developed to improve the mechanical properties of a circular tube. In this proposed process, a large amount of strain is applied to the wall of tube, leading to grain refinement in the material. In order to investigate characteristics of microstructural evolution such as the distribution of grain size and misorientation angle during the process, an EBSD OIM analysis was carried out. The analysis confirms that the proposed process can very effectively produce a circular tube with ultrafine-grains.