• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1994년도 춘계학술대회 논문집
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• pp.80-91
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• 1994

This study aims detecting forming defects for the forming process of bearing rings, which is designed by an industry expert. The designed process consists of one forming operation for the outer ring and four operations for the inner ring. The thickness of the sheet used is 1.6mm, and is in between of thin sheet and bulk material. Here the rigid-plastic finite element method is applied to the analysis and design of the process without considering anisotropy of thin sheet. Thinning and folding defects are detected if the initially designed process is applied for manufacturing. so a new process is designed by referring the results of the FEM. It is confirmed that the industry expert agree the possibility of defects derived from FEM results.

• 소성∙가공
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• 제3권2호
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• pp.189-201
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• 1994

This study aims detecting forming defects for the forming process of bearing rings, which is designed by and industry expert. The designed process consists of one forming operation for the outer ring and four operations for the inner ring. The thickness of the sheet used is 1.6mm, and is in between of thin sheet and bulk material. Here the rigid-plastic finite element method is applied to the analysis and design of the process without considering anisotropy of thin sheet. Thinning and folding defects are detected if the initially designed process is applied for manufacturing. So a new process is designed by referring the results of the FEM. It is confirmed that the industry expert agree the possibility of defects derived from FEM results.

• 소성∙가공
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• 제13권2호
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• pp.129-136
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• 2004

Recently, instead of a matched die forming method requiring a high cost and long delivery term, a multi-point dieless forming method using a pair of matrix type punch array as flexible dies has been developed. Since the conventional multi-point dieless forming method has some disadvantages of difficulty in precise punch control and high-cost of equipment, a new concept of multi-point dieless forming method combined with an elasto-forming method has been suggested in this study. For optimal selection of elastomers, compression tests of rubbers, polyethylene and foams were carried out together with FEM analysis of the deformation behavior during sheet forming process using a rigid punch and elastomers. Compressive strain was concentrated on the upper central area of the elastomer under the punch, and the rubber exhibited higher concentration of the compressive strain than foams. Two-dimensional curved surface was formed successfully by the multi-point elasto-dieless forming method using an optimal combination of rubber and foam materials.

• 소성∙가공
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• 제4권3호
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• pp.222-232
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• 1995

The planar anisotripic FEM analysis for predicting earing profiles and draw-in amounts in the deep-drawing process is introduced. An implicit, incremental, updated Lagrangian formulation with a rigid-viscoplastic constitutive equation is employed. Contact and friction are considered through the mesh-based unit vector and normal contact pressure. The consistent full set of governing relations, which is comprising euilbrium and geometric constraint equations, is appropriately linearized. Barlat's strain-rate potential is employed, whose in-plane anisotropic properties are taken into account with anisotropic coefficients and potential parameters. The linear triangular membrane elements are used for depicting the formed sheet. In the numerical simulations of deep drawing processes of a flat-top cylindrical cup for 2090-T3 aluminum alloy sheet show good agreement with experiments, although some discrepancies were observed in the directional trend of cup height and thickness strains.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1996년도 추계학술대회논문집
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• pp.38-47
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• 1996

Sectional analysis program for plane strain or axisymmetric geometry of aluminum alloy sheet metals was developed. For modeling the anomalous behavior of aluminum alloy, Barlat's strain rate potential and Hill's 1990 non-quadratic yield theory arranged under the plane stress assumption were employed. 2-D rigid-viscoplastic FEM formulation based on the bending-augmented membrane theory was derived, solving simultaneously force equilibrium as well as non-penetration condition. Isotropic hardening law was also assumed for yielding behavior. To verify the validity and availability of the developed program, 2-D stretch/draw forming process for plane strain geometry and cylindrical cup deep drawing process for axisymmetric geometry were simulated.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 제4회 박판성형 심포지엄
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• pp.21-28
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• 2003

Recently, instead of a matched die forming method requiring a high cost and long deliverly ten a multi-point dieless forming method using a pair of matrix type punch array as flexible dies has been developed. As this multi-point dieless forming method has some disadvantage of difficulty in precise punch control and high-cost of equipment, a new concept of multi-point dieless forming method combined with elastomer forming was suggested in this study. For optimal selection of elastomers, compression tests of rubbers, polyethylene and foams were carried out together with FEM analysis of the deformation behavior during sheet forming process using a rigid punch and elastomers. Compressive strain was concentrated on the upper central area of the elastomer under the punch, and the rubber exhibited higher concentration of the compressive strain than foams. Two-dimensional curved surface was formed successfully by the multi-point elasto-dieless forming method using an optimal combination of a rubber and foam.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2001년도 봄 학술발표회 논문집
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• pp.138-145
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• 2001

This paper presents F.E.M. analysis result about the behavior of R.C. beam repaired with steel plate and fiber sheet. The effect of repairing varies with reinforcement ratio of R.C. beam, plate thickness, numbers of fiber sheet, and repairing length, etc. F.E.M. analysis using a program, DIANA, was carried out taking these factors as parameter in this study. Analysis result shows that repaired R.C. beam behaves differently according to parameters and certain cases imply that repairing is useless or may lay structure in dangerous condition. F.E.M. model considers that interfacial behavior between different two parts of repaired beam is rigid based on an assumption that adhesive failure does not appear before yielding of reinforcement and its analysis shows the result coincides with that of experiment.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1994년도 추계학술대회 논문집
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• pp.44-54
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• 1994

A variational formulation and the associated finite elemet equations have been derived for general three-dimensional deformation of a planar anisotropic rigid-plastic sheet metal which obeys the strain-rate potential proposed by BARLAT et al [13]. By using the natural convected coordinate system, the effect of geometric change and the rotation of planar anisotropic axes are considered efficiently. In order to check the validity of present formulation, a cylindrical cup and a square cup deep drawing test was modeled. good agreement was found between the FE simulation and the experiment. The results have shown that the present formulation for planar anisotropic deformation can be efficiently applied to the analysis of sheet metal working processes for planar anisotropic nonferrous metals.

• 대한기계학회논문집A
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• 제20권11호
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• pp.3387-3397
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• 1996

The Hub is an auto mobile component used as aircon clutch. The important aspects in cold forging of the Hub with complex geometry are the design of an initial shape of the workpiece, the possibility of the forming by one-stage operation and the determination of number of performs, etc. Based on the systematic procedure of process sequence design, in this paper, the forming operation of cold forged part of the Hub is designed by the rigid-plastic finite element method. The two design criterion of geometrical filling without defect and an even distribution of effective strain in final product are investigated in controlling the initial shape of the workpiece and preform configuration. It is noted that one preforming operation is required in order to obtain final product of the Hub.

• 한국지반공학회지:지반
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• 제1권2호
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• pp.27-40
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• 1985

본고는 기약지반변형해석에 이용될 범용 program을 개발하고 이를 이용하여 성토부끝에 sheet pile을 타설하거나 혹은 성토부아래의 연약정토지반을 개취하였을 때의 변형억제효과를 연구한 것이다. 본고에 적용된 압밀리론으로서 Biot의 압밀방정식과 구성방정식으로서 탄소성리론에 근거한 modified Cam-clay 이론을 적용하였고 유한요소해석으로서는 Christian-Boehmer계를 도입하여 program화한 것이다. 그 주요한 결론은 다음과 같다. 1. 속변지반의 침하효과에 관해서는 sheet pile이나 심우혼합처새깊이를 자지층까지 관입하여 시공하고 그 자신의 침하가 없을 경우에만 유효하다. 2. 흔히 사용되는 sheet pile대책공법은 통상의 steel sheet pile의 각성으로서는 성토직후의 봉기, 측방변위의 억제효과는 기대할 수 없다. 3. Sheet pile에 대한 예상론인 사용방법은 성토하부에 세밀을 촉진하기 위해 vertical drain을 설치하고 점증재하 방법만이 확실한 효과가 있다. 4. 체층혼합처리공법은 예상한 바와 같이 그 자종가 강성이 클수록 침하억제핵과가 있다. 특히 grouting을 통한 지반강화가 곧장 주변지반의 변형억제효과가 있다고 단정하는 것은 그 강성 까 관련하여 신중히 고려하여 결정해야 한다.