• Journal of Advanced Marine Engineering and Technology
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• v.22 no.1
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• pp.7-15
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• 1998

An upper bound elemental technique(UBET) program has been developed to analyze forging load, die-cavity filling and effective strain distribution for flash and flashless forgings. The program consists of forward and backward tracing processes. In the forward program, flash, die filling and forging load are predicted. In backward tracing process, the optimum dimensions of initial billet in conventional forging are determined from the final-shape data based on flash design. And the analysis is described for merit of flashless precision forging. Experiments are carried out with pure plasticine billets at room temperature. The theoretical predictions of forging load and flow pattern are in good agreement with the experimental results.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1994.10a
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• pp.118-132
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• 1994

This paper investigates a new method to design blocker geometry in rib-web type closed die forging. By examining various forging and blocker geometries, it was found that blocker geometry can be generated by eliminating high frequency mode from finisher geometry. In order to formalize the procedure, low pass filters, which can convert finisher to blocker geometry, are proposed. Also discrete Fourier transform is used for computational efficiency. The blocker geometry designed by the present method are compared with the one by an experienced designer. The blocker geometries are also validated by using FEM simulation. Present results shows that the frequency approach may offer a promising method to design blocker automatically.

• Journal of Advanced Marine Engineering and Technology
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• v.21 no.2
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• pp.117-125
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• 1997

상계요소 해석(UBET) 프로그램은 비대칭 단조공정에서의 다이 충만과정과 단조 하중등을 예측하기 위하여 개발되었다. 보다 용이하게 단조 공정을 해석하기 위하여 비대칭 형상의 단조공정을 평면변형부(길이 부분)과 축대칭변형부(라운딩 부분)으로 나누었다. 평면변형부와 축대칭 변형부의 경계는 전단에너지를 고려하여 결합하는 빌딩 블록 방법(building block method)을 이용하였다. 그리고 본 연구의 비대칭 형상을 단조하는데 최적의 초기시편 형상으로 아령형의 시편(dumbbell-typed billet)을 제시하였다. 또한 실험은 상온에서 플라스티신을 사용하여 수행되었고 수치해석 결과와 실험결과는 비교적 잘 일치하였다.상계요소 해석(UBET) 프로그램은 비대칭 단조공정에서의 다이 충만과정과 단조 하중등을 예측하기 위하여 개발되었다. 보다 용이하게 단조 공정을 해석하기 위하여 비대칭 형상의 단조공정을 평면변형부(길이 부분)과 축대칭변형부(라운딩 부분)으로 나누었다. 평면변형부와 축대칭 변형부의 경계는 전단에너지를 고려하여 결합하는 빌딩 블록 방법(building block method)을 이용하였다. 그리고 본 연구의 비대칭 형상을 단조하는데 최적의 초기시편 형상으로 아령형의 시편(dumbbell-typed billet)을 제시하였다. 또한 실험은 상온에서 플라스티신을 사용하여 수행되었고 수치해석 결과와 실험결과는 비교적 잘 일치하였다.

• Journal of the Korean Society for Precision Engineering
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• v.9 no.3
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• pp.83-101
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• 1992

A systematic method of remeshing is required due to severe mesh distortion after some finite deformation in the finite element analysis of practical forging processes. In order to cope with the problem of mesh degeneracy during deformation, the proper design of meshes plays an improtant role in the analysis. In so-called "Modular Remeshing", the physical characteristics of metal flow and geometric characteristics are incorporated in "Module", which can be applied to the mesh design for a certain mode of deformation in so far as the topology of deforming region remains the same. For the purpose of more effective and systematic use of the modular remeshing scheme, an expert system has been developed in the framework of the proposed remeshing schemel. In oredr to show the effectiveness of the method, the rib-web type forging with axial relief or radial relief and spike forging are simulated. It has been thus shown that the proposed method of automatic remeshing by using modular remeshing and expert system can be futher extended and applied to various forging problems with complicated geometrical configurations.ical configurations.

• International journal of steel structures
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• v.18 no.5
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• pp.1801-1817
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• 2018

This paper presents the numerical parametric analysis on the loading capacity of Channel purlins with screw-fastened sheeting, in which the effects of anti-sag bar and corrugated steel sheet on the ultimate capacity are studied. Results show that the setup of anti-sag bars can reduce the deformations and improve the ultimate capacity of C purlins. The traditional method of setting the anti-sag bars in the middle of the web is favorable. The changing of sheeting type, sheeting thickness and rib spacing has significant effects on the ultimate capacity of C purlins without anti-sag bars, compared with those with anti-sag bars. The proposed design formulas are relatively consistent with the calculations of EN 1993-1-3:2006, which is different from those of GB 50018-2002.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.2 s.42
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• pp.59-69
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• 2005

Employing the classical beam theory for the design of welded steel moment connections has been brought into question by several researchers since the 1994 Northridge earthquake. In this study, the load transfer mechanism in various welded steel moment connections is comprehensively reviewed mainly based on recent studies conducted by the writer. Available analytical and experimental results showed that the load path in almost all the welded steel moment connections is completely different from that as predicted by the classical beam theory. Vertical plates near the connection such as the beam web, the web of the straight haunch, and the rib act as a strut rather than following the classical beam theory. The shear force transfer in the RBS connection is essentially the same as that in PN type connection. Some simplified analytical models that can be used as the basis of a practical design procedure are also presented.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.2
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• pp.285-299
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• 1993

The objective of the present study is to analyze material flow in the metal forming processes by using computer simulation and experiment with model material, plasticine. A UBET program is developed to analyze the bulk flow behaviour of various metal forming problems. The elemental strain-hardening effect is considered in an incremental manner and the element system is automatically regenerated at every deforming step in the program. The material flow behavior in closed-die forging process with rib-web type cavity are analyzed by UBET and elastic-plastic finite element method, and verified by experiments with plasticine. There were good agreements between simulation and experiment. The effect of corner rounding on material flow behavior is investigated in the analysis of backward extrusion with square die. Flat punch indentation process is simulated by UBET, and the results are compared with that of elastic-plastic finite element method.