• 한국지반환경공학회 논문집
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• 제21권3호
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• pp.5-11
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• 2020

최근 도심지에서 많이 발생되는 지반함몰은 교통흐름에 방해가 될 뿐만 아니라 재산적인 손실과 함께 인명피해도 심각하게 발생되는 등 시민들의 안전을 위협하는 요인이 되고 있다. 따라서 함몰된 지반을 긴급하게 복구하여 추가 피해에 대비하여야 하는데 현재 국내의 지반 함몰에 대한 구체적인 기준이 미흡하고 함몰 원인의 정확한 규명 및 재발생에 대한 대책이 미흡한 실정이다. 함몰된 지반의 복구방법으로는 함몰된 흙을 재사용하여 되메우기를 하거나 기타 성토재료를 사용하여 되메움 한 후 도로를 포장하는 방법을 가장 많이 사용하고 있는데 이는 지반함몰을 일시적으로 방지하는 방법에 불과할 뿐 근본적인 해결책으로 볼 수 없다. 또한 이러한 방법으로 보강된 지반은 되메움재의 불량 및 다짐불량 등으로 인하여 추가적인 지반함몰이 발생될 가능성을 배제할 없다. 이 연구에서는 지반 침하로 발생된 지하공동의 복구에 활용할 수 있는 복구재료로써 개량된 준설점토의 공학적 특성을 분석하기 위하여 친환경고화재(EHSM) 및 화강풍화토의 혼합비율을 변화시켜 제작한 공시체에 대한 일축압축강도시험을 수행하였으며, 복구재료의 환경변화에 따른 강도 특성을 규명하기 위하여 동결융해시험을 수행하고 각 단계별 시험이 종료되면 강도분석을 위하여 일축압축강도 시험 및 동탄성시험을 수행하였다. 또한 복구된 지반의 강도특성을 평가하기 위하여 동평판재하시험을 실시하여 복구된 지반의 개량효과를 검증하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.1235-1242
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• 2006

Viscoelastic damping materials are widely used to reduce noise and vibration because of its low cost and easy implementation, for examples, on the body structure of passenger cars, air planes, electric appliances and ships. To design the damped structures, the material property such as elastic modulus and loss factor is essential information. The four-parameter fractional derivative model well describes the nonlinear dynamic characteristics of the viscoelastic damping materials with respect to both frequency and temperature with fewer parameters than conventional spring-dashpot models. However the identification procedure of the four-parameter is very time-consuming one. An efficient identification procedure of the four-parameters is proposed by using an FE model and a gradient-based numerical search algorithm. The identification procedure goes two sequential steps to make measured FRFs coincident with simulated FRFs: the first one is a peak alignment step and the second one is an amplitude adjustment. A numerical example shows that the proposed method is efficient and robust in identifying the viscoelastic material parameters of fractional derivative model.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.494-499
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• 2007

The ballast, one of a track components, plays an essential role as intermedium in transmitting train traffic-load to subgrade safely, and deterioration of ballast caused by cumulative load effects growth of track irregularity. Especially in the case of Gyeongbu high-speed railway, the deteriorating speed of ballast by dynamic vibration is faster than conventional line because KTX is longer than normal trains in length and it's velocity is very fast with high speed of 300km/h as well. In addition, ballast is a nonlinear material contrary to ordinary metal which has homogeneous property and this property of ballast may cause transformation of ballast. Therefore the theoretical modeling of ballast is quite complicated and it is hard to ensure the reliability of the result. The objective of this paper is to examine the availability of GPR(Ground Penetrating Radar) in estimating the thickness and the degree of deterioration of ballast. First, We figured out the principle of GPR which is the technique of evaluating the condition of ballast and then analyzed data which were measured at Gyeongbu high-speed railway where KTX is running now.

• 대한조선학회 특별논문집
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• 대한조선학회 2008년도 특별논문집
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• pp.46-53
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• 2008

Recently, the synthetic material stern tube bush has been applied by ship owner's requirement because the synthetic material has a merit. That is to say, when stern tube seal is damaged and sea water comes into stern tube, it can work without problem because of water lubricating property. However, the material also has a demerit of temperature rise problem when some factors meets on synthetic material, for example, not sufficient lubrication oil supply and not proper shaft alignment and so on. As known in the world, the RAILKO bush is rampant for synthetic material by some ship owner because of the above mentioned reason. However, the bush has several accidents on large container vessel. Unfortunately or fortunately our yard has a chance to apply the RAILKO bush owing to requirement of specific ship owner. Therefore, it is much more required to approach the accurate shaft alignment analysis. In line with this reason, we had a shaft alignment calculation considering hull deformation and hull flexibility (hull stiffness). Also, in the calculation, we had considered dynamic condition which is reflected he propeller thrust forces and moments and oil film stiffness on the shaft alignment calculation. According to he shaft alignment calculation, bearing slope was applied on the tern tube bush and was measured. The RAILKO bush should be applied the running in procedure according to maker's recommendation for performing the oil film on the bush surface. Finally, the vessels were delivered successfully without any problem with AILKO bush as shown on his paper.

• 한국의류산업학회지
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• 제14권2호
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• pp.261-268
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• 2012

The purpose of this study is to investigate problems of design, fitness, suitability for movement, and wearing comfort of jumper for Korean military tank drivers through analysis of actual wearing condition by questionnaire and field evaluation and to provide basic data for developing its improved design. The survey was done for 477 military tank drivers and evaluation was performed using thermal manikin to measure insulation. The overall satisfaction for design of jumper for military tank driver was over 3.5(likert scale). The overall satisfaction for fitness of jumper for military tank driver was also over 3.5. The satisfactions for material was between 2.39 and 3.13 and the satisfaction for pilling property was the lowest, followed by static property and shape stability after laundering. The satisfactions for movement suitability were standing(3.81), sitting(3,38), raising hand(forward: 2.90, sideward: 3.01), respectively. In insulation evaluation of jumper for military tank drivers and outwears(jacket, jumper), the insulation of jumper for military tank drivers was lower than outwear(jumper) and same with outwear(jacket). The insulation in dynamic and still condition(without wind) of jumper for military tank driver was 0.37clo and 0.31clo, respectively. Its decreation rate in dynamic condition comparing to still condition was 59% which was lower than jacket(0.73clo) and jumper(1.15clo).

• 한국정밀공학회지
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• 제33권7호
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• pp.587-594
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• 2016

The Split Hopkinson pressure bar (SHPB) test method, which is composed of three cylindrical bars, measuring devices and frames, is known for its reliable technique of acquiring the mechanical properties of specimens under a high strain rate. This paper demonstrates the processing of design and fabrication of SHPB. First of all, numerical analysis is applied in order to determine the design parameters of SHPB apparatus and verify the validity of design for a SHPB facility. Following this, SHPB apparatus were fabricated in accordance with acquired design parameters by simulation. In order to verify the validity of SHPB apparatus, experimental results using Al6061-T6 were compared with numerical data obtained from a corresponding simulation. The result of this comparative study demonstrates the applicability and validity of the fabricated apparatus.

• 대한기계학회논문집A
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• 제38권6호
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• pp.683-689
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• 2014

본 연구에서는 구조해석 시뮬레이션을 통해 저주파 스퀼을 유발하는 여러 요소를 분석하였다. 해석을 위한 프로그램은 ABAQUS 를 사용하였으며 동적 불안정성을 판명하기 위한 방법으로는 복소 고유치 해석을 채택하였다. 스퀼 유발 요소와 관련된 핵심적인 5 가지 인자를 선정하였고 각각 3 수준으로 분류하였다. 이를 분석하기 위해 실험계획법을 적용하였고, 파라미터 영향도 분석에는 평균분석을 적용하였다. 이을 통해 영향도가 큰 인자를 선별하였고 타당한 해석 기법 및 파라미터 영향분석을 수행하였다.

• 한국안전학회지
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• 제32권4호
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• pp.22-27
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• 2017

In this study, the authors aim to evaluate a structural and fatigue safety of a new type anti-loose nut system with dual nuts composed of main nut and outer nut to enhance the long-term workability and durability so as to improve the performance of conventional anti-loose nut system. Also, a three-dimensional finite-element method analysis was performed to consider the actual geometry and material property of anti-loose nut system with dual nuts and the effect of static and dynamic loads and loading directions. The analytical results showed that the overall static and dynamic stress of the components of the anti-loose nut system with dual nuts were found to be less than that of the fatigue limit of Goodman-smith diagram and allowable stress of each materials, therefore the anti-loose nut system with dual nuts was sufficient to ensure a structural and fatigue safety.

• 한국식품과학회지
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• 제23권6호
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• pp.759-763
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• 1991

게살과 구조적으로 유사한 대두단백 섬유는 dope를 방사하여 얻은 것으로, 대두단백의 dispersion이나 dope의 성질에 의존한다. 대두단백섬유의 출발물질인 대두단백의 dispersion과 dope의 동적 물성을 측정함으로서 그들의 점탄성을 조사하였다. 단백질 농도가 증가할때 dispersion이나 dope모두 단백질간의 상호반응이 일어났다. Dispersion에 알칼리 용액을 넣은 dope는 고분자 중합물질에 상호연결된 특성을 나타내었다. 반면에 dispersion에서는 무정형 중합물질의 특성이 나타났다. Dispersion에 대한 화학변형이 동적물성에 미치는 영향도 관찰하였다.

• Smart Structures and Systems
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• 제15권6호
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• pp.1481-1501
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• 2015

MR-TLCD (Magneto-Rheological Tuned Liquid Column Damper) is a new developed vibration control device, which combines the traditional passive control property with active controllability advantage. Based on traditional TLCD governing equation, this study further considers MR-fluid viscosity in the equation and by transforming the non-linear damping term into an equivalent linear damping, a solution can be obtained. In order to find a countable set of parameters for the design of the MR-TLCD system and also to realize its applicability to structures, a series of experimental test were designed and carried out. The testing programs include the basic material properties of the MR-fluid, the damping ratio of a MR-TLCD and the dynamic responses for a frame structure equipped with the MR-TLCD system subjected to strong ground excitations. In both the analytical and experimental results of this study, it is found that the accurately tuned MR-TLCD system could effectively reduce the dynamic response of a structural system.