鑄造時의 熱流 現象

朴世蔓,朴明均,柳正烈 명지대학교 산업기술연구소 2005 産業技術硏究所論文集 Vol.24 No.-

Olivine sand, zircon sand and chromite sand are used for the molds of steel castings as well as silica sand. Solidification times of carbon steel castings cast in these sand molds were measured. These times were in proportion to the squared values of the thickness of the castings for each of the different sand molds. The values of the mold constants (cal/㎝²sec^(½)) of the above four kinds of sand molds remained constant while the castings were solidifying. These values were dependent on the kind of sand but independent of the casting thickness. The values of heat diffusivity of the different sand molds which were calculated from the measurement of the solidification time were almost identical with the values obtained from the tests of heat absorption. The fluid length of steel castings becomes shorter as the heat diffusivity of the sand mold increases. The fluid length of steel castings seems to be affected by solidification both at the base and at the top of the flowing metal.

열사이클에 의한 세라믹/금속접합의 잔류응력에 관한 연구

박세만,박명균,정영도 명지대학교 산업기술연구소 2001 産業技術硏究所論文集 Vol.20 No.-

Thermal stresses at ceramic/metal interfaces in ceramic-metal joints are analyzed with emphases on assessing residual stresses produced and retained in the joints during joining processes of ceramics with metals, and evaluating their redistributions under applied thermal cycles. A thermoelastic plastic finite element method is adopted to compute various physical quantities associated with the thermal processes. The computational results demeonstrate that the residual stresses on the ceramic side in the metal-ceramic joints, generally, increase with increasing peak temepratures in the thermal cycles. Also, the higher the peak temperatures are in the thermal cycles, the higher values are obtained for intensities (Q) and coefficients (λ) of stress singularity near the end point along the interface on the ceramic side.

교랑 공사에 동시공학 적용을 위한 체크리스트 도출

박세만,박태일,김형관,Park, Seaman,Park, Taeil,Kim, Hyoungkwan 한국건설관리학회 2013 한국건설관리학회 논문집 Vol.14 No.1

건설프로젝트가 대형화, 복합화, 그리고 장기화됨에 따라, 혁신적인 신공법의 개발과 건설 프로세스의 첨단화에 대한 건설 시장의 요구도 지속적으로 증가하고 있다. 이에 건설 분야에서는, 빠른 상품 개발과 품질향상을 위하여 산업분야에서 널리 쓰였던 동시공학의 건설프로젝트 적용을 고려하게 되었다. 하지만 동시공학의 개념들은 선진화된 관리시스템의 부재 및 개념의 학술적 정립 미비로 인하여, 실제 건설 현장에 충분히 활용되지 못하였다. 이에 본 연구는 대표적인 장기, 대형 프로젝트인 교량공사를 대상으로 성공적인 동시공학 적용을 위한 체크리스트를 도출하였다. 국내 건설 분야에 동시공학 실제 적용 사례와 문헌고찰을 통해 일차적으로 동시공학의 건설 산업적용을 위한 체크리스트를 도출한 뒤, 교량전문가 인터뷰를 바탕으로 이전 단계에 도출된 체크리스트를 교량공사의 특성에 맞게 수정하고 발전시켜 교량공사에 성공적인 동시공학 적용을 위한 체크리스트를 확정하였다. 또한 188 명의 관련 업무 수행자들의 설문조사를 바탕으로 체크리스트의 유용성을 검증하고 중요도 실행도 분석으로 우선적인 관리가 요구되는 필수요소를 확인하였다. 본 연구를 통하여 도출된 체크리스트는 교량건설 프로젝트의 진행에 있어 체계적인 사전검토와 건설 단계별 프로세스의 종합적 분석을 가능케 하여, 동시공학의 실무 활용성을 증대시킨다는 점에서 그 의의가 높다고 판단된다. As construction projects became larger and longer, the need for the construction technologies and innovative construction processes has been continuously increased in construction field. In response to this trend, construction industries tried to adopt the concurrent engineering which had been normally applied for manufacturing industries to develop the products with improved quality in a reduced time. However, the application of the concurrent engineering to construction field was limited due to the lack of advanced management system and incomplete theoretical backgrounds. In this regard, this study attempted to develop a checklist for the successful application of concurrent engineering to bridge projects. To this end, this study presents the checklist for the application of concurrent engineering to construction projects. Further, the checklist was modified and updated to reflect the specific feature of the bridge construction using expert interviews. With the help of additional 188 experts, a questionnaire-based survey was also conducted to validate the checklist. In addition, using importance-performance analysis(IPA), the study identified the factors needed for intensive improvement. Consequently, the proposed checklist is expected to be useful, because it improves the applicability of the concurrent engineering in that it enables managers to monitor construction progress and further to protect the project from potential risks.

두 가지 동적 진동실험을 이용한 Carbon-Epoxy와 Graphite-Epoxy복합재료의 동적 탄성계수 측정

박세만,박명균,최순권 명지대학교 산업기술연구소 2001 産業技術硏究所論文集 Vol.20 No.-

As requirements for the weight reduction and the higher strength of structures in use have become strict composite materials have been frequently utilized in many industrial products. Accordingly, it becomes essential that designs of safe structures are ensured and furthermore their proper inspections should be in order subsequently at any cost. In light of this, accurate measurements of elastic constants, which is one of major mechanical properties, warrant careful considerations. In this research the two dynamic vibratory techniques, acoustic resonance method and impulse method, are employed in parallel to directly compare the two techniques and to evaluate the elastic constants more accurately.

계장화 샤피충격시험기를 이용한 재료의 동적파괴특성에 관한 연구

박명균,김길수,김기동,박세만 明知大學校 産業技術硏究所 1996 産業技術硏究所論文集 Vol.15 No.-

This investigation determines dynamic fracture characteristics of metals such as SM45C, SM20C and SS41. One of the dynamic characteristics, dynamic fracture toughness, was evaluated by conducting instrumented charpy impact tests. Specially, in this study signals obtained from the strain gage implanted in the impact tup is transformed to Load-Time data by digital signal processing. To obtain appropriate dynamic fracture toughness, the Load-Time data is critically reviewed and tested based on three criteria; inertia effect, limited frequency response and energy levels. This procedure ensures the reliability of the data. The data is then, examined in view of topological aspects of fractured surfaces of the metals to reveal dynamic natures of materials failure.

복합 재료의 내부 감쇠와 복소탄성계수의 오일러 방정식과 티모센코 방정식에 의한 실험적 비교

이재혁,이동식,김형삼,박세만 明知大學校 産業技術硏究所 1999 産業技術硏究所論文集 Vol.18 No.-

Damping is a property for materials and systems to dissipate energy during periodic deformations. Generally, damping causes stiff decrease in amplitudes and shifts in phase. Also, even at resonance, amplitudes are substantially attenuated. This phenomenon of damping helps in reducing stresses developed during vibrations and consequently improves fatigue lives of materials. In this work internal damping and complex moduli are experimentally determined. an impulse technique os utilized in experiments and cantilever beams are selected as test subjects for the measurements of flexural vibrations since the beams lend themselves easily as simplistic ideal models. Also, Moduli of Elasticity represented by Euler-Bernoulli beam theory and Timoshenko beam theory are compared.

자동차용 축열시스템의 설계에 대한 연구

송영길,차경옥,박세만 明知大學校 産業技術硏究所 1994 産業技術硏究所論文集 Vol.13 No.-

A study was conducted to design automotive thermal energy storage for reduction in exhaust emission and enhancing the passenger's comfortability. Ba(OH)2 8H2O was chosen, based on its thermodynamic characteristics and a series of test, as a base material for the energy storage system. Sr(OH)2 8H2O and H2O were added to the base material to protect degradation that is appeared during the cycling test of the pure base material. Thermal storage were, then designed to provide 2,000 kJ of energy within a few minutes of engine ignition with the computer simulation results.

열충격이 부가된 Carbon-Epoxy 복합재료의 탄성계수 변화에 관한 연구

이동식,박세만 明知大學校 産業技術硏究所 2000 産業技術硏究所論文集 Vol.19 No.-

Composite materials have been recognized for continuing increase in their usages and applications in automotive and aircraft industries. This trend inevitable calls for extensive researches in the materials. Carbon-epoxy composites. one of the foremost composites are selected for investigations to determine their thermal characteristics. Being subjected to thermal shocks consisting of repeated heatings and cooling the carbon-epoxy composites show variations in elastic constants revealing the thermal nature of the composites. In this study the values of E₁are observed to increase and the values of G13 are observed to decrease as thermal shocks are applied. However the values of E₂decrease initially, but later recover gradually. Unlike E₁, E₂and G13 another elastic constant G23 exhibits very different behavior with increasing temperatures.

열피로가 부가된 Carbon-Epoxy 복함재료의 탄성계수 변화에 관한 연구

김형삼,이동식,이재혁,박세만 明知大學校 産業技術硏究所 1999 産業技術硏究所論文集 Vol.18 No.-

Composite materials have been increasingly used in automotive and aircraft industries, naturally leading to active researches on the materials. Carbon-epoxy composites, one of major composite materials, are investigated to determine their thermal characteristics. Under conditions of thermal fatigues composed of repeated heatings and coolings, variations of elastic constants are studied for the carbon-epoxy composite to reveal the thermal nature of the composites. In general, composite materials are known to have decreasing elastic constants with increasing temperatures. However, in contrary to this commonly observed behavior, the results obtained in this investigation for the elastic constants of the carbon-epoxy composites show unexpected phenomena in that the elastic constants initially increase with increasing temperatures to certain point and decrease later with further increase in temperatures when the carbon-epoxy composites are subjected to thermal fatigues.

원형구멍이있는 띠모양평판에서의 광탄성 실험법에 의한 應力해석

박세만,박명균,정재진,백범선,김용주 明知大學校 産業技術硏究所 1994 産業技術硏究所論文集 Vol.13 No.-

A stress analysis on a strip with a circular hole was carried out by the computer assisted photoelastic experimental method. A stress concentration phenomenon around the hole of a strip under axial loading was carefully investigated through this study. The result shows that it well agrees with the results of finite element method and photoelasticity. We suggest that computer assisted photoelasticity experiment is very efficient method for data analysis compared to conventional experimental stress analysis method.