• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.6
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• pp.1205-1215
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• 1992

The solidification rate is of special importance in determining the casting structures and properties. The heat transfer characteristics at the interface between the mold and the casting is one of the major factors that control the solidification rate. The thermal resistance exists due to the air-gap formation at the mold/casting interface during the freezing process. In this study two-dimensional Stefan problem with air-gap resistance in the rectangular mold is considered and the heat transfer characteristics is numerically examined by using the enthalpy method. The effects of the major parameters, such as mold geometry, thermal conductivity, heat transfer coefficient, and initial temperature of casting, on the thermal characteristics are investigated.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.1
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• pp.121-128
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• 2016

A furan mold design and machining system for marine propeller casting was developed. In general, a large marine propeller is produced by casting in a foundry, where the upper and lower molds are constructed of cement or other materials like furan. Then, the cast workpiece is machined and manually ground. Currently, furan mold construction requires a series of manual tasks. This introduces a fairly large amount of stock allowances, which require a considerable number of man-hours for later machining and grinding, and also increase the work processes. A mold design and off-line robot programming software tool with a six-axis robot hardware system was developed to enhance the shape accuracy and productivity. This system will be applied in a Korean ship building company.

• Polymer(Korea)
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• v.27 no.2
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• pp.142-151
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• 2003

PMMA panels are made by two fabrication methods; cell molding and belt molding processes. But these methods have disadvantages in productivity and cost. So plastic processing engineers are very interested in developing a new production method for PMU panels using plastic films as molds because the new method can reduce production cost of belt molding method as well as can improve productivity of cell molding method. To give a solution for developing such a new molding method, the effects of melthyl methacrylate compound composition and curing reaction condition on the processability and mechanical strength of PMMA panels were investigated in this study. Poly(vinyl acetate) film was used as molds in producing PMMA panels. To determine an MMA compound showing good processability and good mechanical properties after curing, ingredients and their compositions were optimized step by step. Acrylic acid, as a coupling agent and a modifier, played an important role in increasing mechanical strength of PMMA panels.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.1
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• pp.87-95
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• 2011

A rational method for determination of initial cable forces in cable-stayed bridges without complicated nonlinear analysis is presented. Initial shape analysis for cable-stayed bridges should be able to find optimizated initial cable forces and unstrained length that minimize deflection and vending moments of the deck and pylon. A presented method utilizing the idea of force equilibrium organizes initial shape analysis for each types of cable-stayed bridges. The results of that analysis were compared to several existing methods for 2D numerical examples. And for 3D actual bridges, the improved TCUD method was performed to demonstrate the accuracy of this study.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.533-536
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• 2008

It is on increasing trend to employ H-rolled beams as main flexural members of bridges and of temporary structures owing to their handiness for construction, maintenance, and management. But in the case of applying H-rolled beams to bridges, maximum length of bridge span is around 20m. Therefore, to develop simplified steel-concrete composite bridge having long span using H-rolled beam needs new cross girder system at internal supports, optimization of bridge system without cross beams between supports and steel-concrete composite bridge deck. This study performs mechanical analysis of cross girder system for H-rolled beam steel-concrete composite bridge with long span and verifies its usefulness.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 1997.11a
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• pp.303-308
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• 1997

전기설비에서 광범위하게 사용하고 있는 유압변압기는 연소성과 환경오염의 문제등으로 인하여 에폭시 수지를 주재로한 진공주형형 몰드변압기로 발전하였다. 따라서 현재는 건축물의 옥내에는 광범위하게 사용되고 있다. 본 논문에서는 에폭시 수지를 사용한 진공주형형 몰드변압기를 시료로 사용하여 전기실과 유사한 환경에서 연소시험에 의한 난연성과 자기소화성을 확인하여 몰드변압기로 인한 소화설비의 불필요성을 입증하였고, 청정소화 약제의 하나인 NAF S-III소화제로서 소화실험을 시행하여 그 소화시간을 측정하고 연소 시험의 결과와 비교 평가하였다. (중략)

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.6
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• pp.945-952
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• 1987

In this paper, Crack molding method called "Teflon crack Molding Method" is developed. With help of this method, we can mold a crack which is very similar to the natural crack, which has the tip radius of about 20.mu. the vertical and horizontal quality of crack excellent. In addition to these, by using this method in photoelastic experiment we can obtain the clear crack tip location and Isochromatic fringe pattern boundary, therefore the precise in the experimental data can be improved. improved.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.2
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• pp.376-381
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• 1990

An interactive computer program to design a mold cavity with the proper rigging system has been developed. In addition to the pattern and the risers generated in part 1 of this work, the various components of the gating system are generated in complete three dimensional models by a rational approach. Then they are laid interactively by the user, and united together with the pattern and the risers to result in the three dimensional model of the mold assembly. Finally, the vents and the mold box are constructed following the user's interactive specification and then the mold cavity is completed in a three dimensional geometric model by subtraction the mold assembly and the vents from the mold box. The three dimensional model of a mold cavity is useful for many related applications such as the solidification simulation for mold evaluation and the NC tool path generation for mold production.

• 기계와재료
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• v.21 no.2
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• pp.122-135
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• 2009

타이타늄은 경량성, 고강도성, 내화학성, 인체친화성, 내환경성 등의 물성을 이용하여 다양한 산업분야에 활용되고 있다. 다양한 산업분야에 정형부품으로 타이타늄을 가공하는 기술 중에서 가장 경제성이 높은 분야로 주조공정을 들 수 있다. 주조공정으로 부품을 제조하면 복잡한 형상을 기계가공하지 않고 거의 정형으로 제조할 수 있으며, 기계적 물성 또한 단조품에 버금가는 제품을 생산할 수 있다. 또한 다량의 제품을 생산할 수 있기 때문에 경제성에서도 유리하다. 이와 같은 주조품을 제조하는데는 진공에서 불순물의 유입을 최소화 할 수 있는 특수용해공정과 주형과의 반응을 최소화 할 수 있는 주형재료와 주조방안이 필수적이다. 본 고에서는 반응성이 높은 타이타늄을 용해하는 기술과 주형과의 반응이 최소활 될 수 있는 주형재료의 선정, 그리고 실 제품에 활용하기 위한 다양한 후처리 기술에 대하여 요약하였다.

• Horticultural Science & Technology
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• v.31 no.4
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• pp.467-472
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• 2013

Twenty and 16 accessions of the countrywide weedy melon (Cucumis melo var. agrestis) collections were evaluated in 1986 and 1990, respectively. There was a good variation in the plant height and their leaves were small in general. In sex expression, 30 of the accessions were andromonoecious, 4 were monoecious and 2 were hermaphrodite. Female flower set on main stems was extremely rare except for on hermaphrodite. On andromonoecious and monoecious plants, abundant female flowers set at the 1st and 2nd node of branch vines. Bitter taste was found in the young fruits of all the accessions tested. Mature fruits were dark yellow, yellow, light yellow or milky white in color, small in size, and very low in sweet taste. The number of seeds per fruit varied from 50.6 to 158.4 showing the characteristics of wild species for perpetuation in wild.