• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.2
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• pp.56-61
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• 1999

The fine blanking is a process of pressworking which makes possible to produce thick sheet metal parts of finished sheared surface and close dimensional accuracy over whole material thickness in single blanki ng operation. Fine blanked parts in general are characterized by their cleanly sheared surface over the whole sock thickness and accurate size for the specific functions. The fine blanking technology is urgently needed to remove secondary operations which are necessary in conventional blanking operation and cost reduction. In this study, the effect of material texture and vee-ring on parts for automobile is investigated by experimental observation and analysis.

• Transactions of Materials Processing
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• v.12 no.1
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• pp.43-48
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• 2003

The strain state during the continuous confined strip shearing (CCSS) based on ECAP was tackled by means of a two-dimensional FEM analysis. The deformation of AA 1100 sheet in the CCSS apparatus was composed of three distinct processes of rolling, bending and shearing. The pronounced difference in the friction conditions on the upper and lower roll surfaces led to the different variation of the strain component ${epsilon}_13$ throughout the thickness of the aluminum sheet. Strain accompanying bending was negligible because of a large radius of curvature. The shear deformation was concentrated at the corner of the CCSSchannel where the abrupt change in the direction of material flow occurred. The process variables involving the CCSS-die design and frictions between tools and strip influenced the evolution of shear strains during CCSS.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.04b
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• pp.166-171
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• 1993

절삭공구에의한 절삭가공은 오늘날 가장 보편화된 가공기술중의 하나이다. 그런데, 최근들어 각종 첨단산업의발전과 함께 초정밀 부품제작이 필수선결 조건으로 부상하고 있으며, 이에대한 해결방안중의 하나로 초정밀가공 기 술로 크게 대두되고 있다. 최근 컴퓨터 기술의 발달에 따라 구조해석분야의 해석방법론의 개발 및 보완에 힘입어 Klemecki(1973)에 의해유한요소법을 이용한 Chip생성기구 해석에 관한 연구가수행되었으며, Stevenson(1983) 등에의해단열조 건하에서 변형률과 온도 상태에서의 Chip형상, 잔류응결-변형율에 대한 연구가 이루어졌다. 본 연구에서는 유한요소법을 이용하여 미소절삭기구를 모델링하고, 절삭인자규명을 중심으로 응력-변형률 해석을 실시함으로써, 미소절삭시의 Chip 생성기구 및 전단면 생성 원리, 공구와 Chip간의 마찰기구의 고찰을 통해기본 Mechanism 이해와 적절한 절삭유한요소모델 제시의 기초자료로 삼고자 한다. 특히 본 보고서에서는 미소 절삭기구의 적정한 Constitutive Deformation Law 마찰계수 등 주요절삭인자변경에 따른 미소절삭기구 해석에 주안점을 두어 연구한 결과를 기술하였다.

• Transactions of Materials Processing
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• v.13 no.4
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• pp.382-387
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• 2004

The continuous confined strip shearing (CCSS) based on the equal channel angular pressing (ECAP) was modeled by means of a rigid-plastic two-dimensional finite element method (FEM). Parallel to the simulations, samples of AA 1050 sheets were experimentally deformed by CCSS. The CCSS deformation led to the formation of through thickness texture gradients comprising a strong shear texture in the sheet center and weak shear textures in the sheet surfaces. FEM analysis revealed variations in the strain component $\varepsilon_13$ along the sample thickness direction, which gave rise to the evolution of different textures. A high friction between the sample and die surface was responsible for lowering intensities of the shear texture components in thickness layers close to the surfaces.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.987-992
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• 1997

Burrs always come out with the machining of ducterial with small size. Though the size of burrs is small, burrs dominate deterioration of the accuracy of the micro grooves. So the burr generation model especially side burr generation model was investigated to predict the size of the burrs at the given cutting conditions. The side shear plane is introduced to build the burr generation model and the width of side shear plane nomalized with cutting depth is defined with the shear angle. From the theoretical observation, the width of side shear plane can vary up 40% of the cutting depth. To determine the size of burr and stiffness, single groovings were carried out and it was found that there exist a critical depth of cut that the size or stiffness of the burr vary.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.93-96
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• 2004

This paper presents a study on defects in pearlite lamella structure of high carbon steel by means of finite-element method(FEM) simulation. High-carbon pearlite steel wire is characterized by its nano-sized microstructure feature of alternation ferrite and cementite. The likely fatigue crack is located on interface of the lamella structure where the maximum amplitude of the longitudinal shear stress and transverse shear stress was calculated during cyclic loading. The FEM is proposed for maximum shear stress from loading of lamella structure, and a method is predicted to analyze the likely fatigue crack generation. It is possible to obtain the important basic data which can be guaranteed in the ductility of high carbon steel wire by using FEM simulation.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.757-762
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• 1994

본 연구에서는 정밀진단가공을 위한 파인 블랭킹 기술 개발을 위한 파인 블랭킹용 전용 프레스를 사용 하지 않고 범용 유압 프레스에서 조보 유압 장치에 의해 압력을 조절해가면서 가공특성에 관한 실험적 연구와 이론 해석을 수행한다. 실험을 위해 파인 블랭킹 금형과 유압 장치를 설계 제작하고, 정밀진단 특성에 제일 큰 영향을 미치고 있는 V-돌기( Vee-ring)의 유무와 위치 그리고 스트리핑력 및 카운터 펀 칭력 변화에 따른 제품 정밀도를 조사해 가면서 최적의 정밀도 예측 수단으로 적절함을 확인할 수 있었으며, 실험결과는 작업 조건에 관계없이 모든 제품이 깨끗한 전단면을 나타내고 있으며, 일반적으로 스트리핑력이 감소할수록, 그리고 카운터 펀칭력이 증가할수록 캠버량이 감소하고 특히 카운터 펀칭력에 큰 영향을 받고 있음을 알 수 있었다. 이와같은 현상은 유한 요소해석에 의한 캠버량의 예측에섣고 정성적으로 잘 일치하고 있는 것으로 나타났다.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.409-412
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• 2009

A study is made to put forward the new method of continuous-shear drawing (CSD), and investigate deformation behavior and microstructure evolution of aluminum alloy with a comparison of equal-channel angular (ECA) drawing. In contrast to ECA drawing, the die for CSD deformation can impart an additional strain to the workpiece since the diameter of the exit channel is narrower than that of its entrance channel. Although no significant crack occurs in all conditions during deformation, the sample deformed via CSD method showed better surface quality as compared to ECA drawing. This is mainly ascribed to the fact that the sample is significantly bent rather than sheared when deforming through ECA drawing.

• Journal of Korean Tunnelling and Underground Space Association
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• v.8 no.2
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• pp.183-196
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• 2006

Rock joint roughness obtained from the camera-type 3D scanner was classified into waviness and unevenness. The classification criteria were established in the previous study; digital filtering was used to distinguish one from another. The classified and original profiles were used to produce metal moulds. For accurate machining of the moulds, the WEDM(Wire-cut Electric Discharge Machining) was adopted. Specimens were cast using high strength gypsum, and joint shear tests were performed by varying normal stress from low value to high one. Roughness mobilization characteristics depending on the asperity scale and the applied normal stress were investigated. A new equation was proposed to predict shear strength of rock joint, which can consider the characteristics of roughness mobilization and roughness parameters. The roughness quantification composed of waviness and unevenness was found to be a useful method to predict the joint shear strength.

• Journal of Korean Society of Steel Construction
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• v.15 no.5 s.66
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• pp.591-601
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• 2003

Because of their high out-of-plane and in-planes strength, trapezoidally corrugated plates have been increasingly used in buildings and bridges. If corrugated plates are used as the web of plate girders or prestressed concrete box girders, the flanges take most of the bending stress. On the other hand, the corrugated plate web supports shear stress due to the accordion effect. The corrugated plate web could fail by three different buckling modes: global, local, or interactive shear buckling. To determine the effects of geometric parameters on the buckling capacity of the corrugated plates, a parametric study was performed using finite dement method. The analysis results showed that the buckling capacity and modes depend on individual parameters as well as combinations of parameters.