• 동력기계공학회지
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• 제16권3호
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• pp.22-28
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• 2012

Active magnetic bearings(AMBs) present a technology which has many advantages compared to traditional bearing concepts. However, they require backup bearings in order to prevent damages in the event of a system failure. In this study, the dynamics of an AMB supported rotor during impact on backup bearings is studied employing a detailed simulation model. The backup bearings are modeled using an accurate ball bearing model, and the model for a flexible rotor system is described using the finite element approach with the component mode synthesis. Not only the influence of the support stiffness, clearance and friction coefficient on the rotor orbit, but also bearing load are compared for various rotor system parameters. Comparing these results it is shown that the optimum backup bearing system can be applicable for a specific rotor system.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2007년도 추계학술대회 및 제23회 정기총회
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• pp.376-382
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• 2007

항로를 횡단하여 건설된 교량은 부근을 지나던 선박의 기관이나 조타기의 고장 또는 비상한 외력의 영향이나 인위적인 판단오류로 인하여 발생할 수 있는 선박과 교각의 충돌을 예방하고 불가피한 충돌의 경우에도 교량의 붕괴를 방지하는 대책을 마련하여야 한다. 충돌이나 간접 충격에 의하여 교량의 상판이 붕괴되는 경우 많은 인명의 손실과 교량으로 연결되는 간선도로의 장기간 폐쇄는 국가적인 재앙이 될 것이기 때문이다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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• pp.153-154
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• 2015

Voltage Source Converter HVDC (VSC-HVDC) are a better alternative than conventional thyristor based HVDC systems. Unfortunately, VSC-HVDC's full potential cannot be utilized up till now due to absence of suitable HVDC protection. Recently, hybrid HVDC circuit breakers (HDCCB) have been developed and successfully lab tested. However, their application and feasibility in VSC-HVDC needs to be investigated. In this research paper we have modelled an existing HDCCB and evaluated its impact on fault reduction and interruption in VSC-HVDC systems. The HDCCB was applied in Korean Jeju-Haenam VSC-HVDC system model and its impact was analyzed for HVDC line-to-ground and line-to-line faults. HDCCB successfully interrupted the fault current and prevented the damages to costly IGBTs and converter transformers.

• 대한조선학회논문집
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• 제40권3호
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• pp.37-44
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• 2003

In rough seas, bow-flare regions of the sea-going ships are subject to high impact pressures due to the bow-flare slamming and panting. And many ships suffer structural damages in that region, even though they were built under the bow structure strengthening rules of the ship classes. So, a new design method for bow-flare structure is highly required. In this paper, bow-flare damage analysis is performed for 17 ships (total number of damage/non-damage data is 782). Based on this analysis, a new design standard and method for bow-flare structure (shell plate, frame and web frame) is proposed. 80.4% of the present damage/non-damage data were well-explained by this new design standard.

• 한국안전학회지
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• 제27권2호
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• pp.98-104
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• 2012

Current [Guideline for Installation and Management of Sidewalks and Safety Facilities on Roads] suggests that the types of curbs should be Barrier curb ($85^{\circ}$). Although Barrier curbs ($90^{\circ}$) were not specified in the guideline. The curbs installed on the roads currently are Barrier curbs ($90^{\circ}$) which are not specified in the installation standard. Therefore, it is critical to prepare for the installation standard of curbs by researching types of curbs and driving safety. This research have assessed the driving safety throughout Full Scale Crash Test according to type of curbs (Barrier curbs ($85^{\circ}$) and Barrier curbs ($90^{\circ}$)). Barrier curbs ($90^{\circ}$) showed higher figure in Theoretical head Impact Velocity, Post-impact Head Deceleration, Vehicle Damage when Crash, Passenger's Wounds Severity, and every other items than Barrier curbs ($85^{\circ}$). Barrier curbs ($85^{\circ}$) were found to have better Occupant Safety Index. Analysis of Behavior Using Full-Scale Crash Test showed difference depending on the Impact Condition between Barrier curbs ($85^{\circ}$) and Barrier curbs ($90^{\circ}$). Generally, Barrier curbs ($85^{\circ}$) were superior than Barrier curbs ($90^{\circ}$) in terms of protecting the passengers and vehicle damages. When an impact angle increases, Acceleration of Vehicle, Variations of Speed, and Contact Relationship between Wheels and Curbs, two types of curb showed similarity. However, if an impact of an angle decreases, Barrier Curbs ($85^{\circ}$) showed excellence in Driving Safety such as Acceleration of Vehicle, Variations of Speed, and Contact Relationship between Wheels and Curbs.

• 대한조선학회논문집
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• 제54권1호
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• pp.34-42
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• 2017

In rough seas, green water shipped on board may impose quite large impact loads on the structures on deck and sometimes result in structure damages. One of the essential tasks of the naval fluid engineers is to provide the design impact loads which are needed for proper design of the structure strength against the green water impacts. Computation of the design impact load due to green water needs first a process to find the sea condition and the ship cruising condition which cause maximum green water impacts on structures as well as other succeeding processes to compute ship motion responses, green water flows and impact loads. Also, as a bold and practical process, it is needed that the irregular real seas are to be substituted by design regular waves which are equivalent in view points of green water impacts. In this paper, the whole processes to compute the design green water loads acting on bow structure are set up creatively. And the green water design impact loads acting on the box-type structure of a high-speed ship's bow are computed and discussed.

• 대한기계학회논문집A
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• 제40권10호
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• pp.857-864
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• 2016

항공산업의 발달로 하늘에는 많은 비행기, UAV, 드론이 비행하고 있다. 비행기와 UAV는 빠른 속도로 비행하며 드론의 프로펠러는 빠른 속도로 회전하고 있다. 이렇게 빠른 속도의 비행체간의 충돌은 비행기 운항과 승객의 안전성을 위협하고, 지상에 있는 인명과 재산에 피해를 줄 수 있다. 비행체의 운항속도는 음속(340m/s) 내외이며, 프로펠러의 회전 속도는 그 보다 작은 속도 영역이다. 현재까지의 충돌 실험은 공기의 힘을 이용한 방식으로 충돌 속도를 얻었고, 공기 팽창에 따른 넓은 공간을 필요로 한다. 하지만 전자기력 발사장치는 그보다 작은 공간에서 충분한 속도를 얻을 수 있다.(~500m/s) 본 논문에서는 전자기력 발사장치의 설계와 이에 따른 제작에 관한 방법을 제시하고자 한다.

• 한국전산구조공학회논문집
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• 제33권5호
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• pp.297-302
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• 2020

대한민국은 산악지형이 많으며 사면붕괴로 인한 도로구조물 및 인명피해가 종종 발생한다. 이러한 사면붕괴로 인한 피해를 줄이기 위해서 낙석방지시설이 필요하다. 국내의 낙석방지울타리는 50kJ의 낙석 충돌 에너지에 저항할 수 있도록 설계되었다. 하지만, 낙석에너지의 크기는 사면의 형태 및 조건에 따라 편차가 크며 약 100kJ에 이르기도 한다. 따라서 효율적인 낙석방지울타리의 설계 및 설치를 위해서 여러 종류의 낙석에너지에 맞는 표준화된 낙석방지울타리가 필요한 실정이다. 본 연구에서는 다양한 낙석에너지에 따른 낙석방지울타리의 표준 단면을 유한요소해석을 통하여 제안하였다. 최종적으로 기존 50kJ 낙석방호울타리 외에 30kJ 및 100kJ급 낙석방지울타리를 제안하였다.

• Ocean Systems Engineering
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• 제9권4호
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• pp.409-422
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• 2019

Sloshing is a phenomenon which may lead to dynamic stability and damages on the local structure of the tank. Hence, several anti-sloshing devices are introduced in order to reduce the impact pressure and free surface elevation of liquid. A fixed baffle is the most prevailing anti-sloshing mechanism compared to the other methods. However, the additional of the baffle as the internal structure of the LNG tank can lead to frequent damages in long-term usage as this structure absorbs the sloshing loads and thus increases the maintenance cost and downtime. In this paper, a novel type of floating baffle is proposed to suppress the sloshing effect in LNG tank without the need for reconstructing the tank. The sloshing phenomenon in a membrane type LNG tank model was excited under sway motion with 30% and 50% filling condition in the model test. A regular motion by a linear actuator was applied to the tank model at different amplitudes and constant period at 1.1 seconds. Three pressure sensors were installed on the tank wall to measure the impact pressure, and a high-speed camera was utilized to record the sloshing motion. The floater baffle was modeled on the basis of uniform-discretization of domain and tested based on parametric variations. Data of pressure sensors were collected for cases without- and with-floating baffle. The results indicated successful reduction of surface run-up and impulsive pressure by using a floating baffle. The findings are expected to bring significant impacts towards safer sea transportation of LNG.

• 비파괴검사학회지
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• 제36권5호
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• pp.391-398
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• 2016

음향방출기법은 구조물에 존재하는 손상 및 손상 메커니즘을 규명하는 가장 유효한 비파괴검사 수단으로 널리 이용되고 있다. 그러나 기존의 손상위치표정 기법은 탄성파 전파 속도에 크게 의존하는 기법의 한계에 의하여 복합재료 또는 이종의 재료로 구성된 구조물에서의 손상을 탐지하기 어려운 한계점을 가지고 있다. 최근 다양한 분야에서 사용되고 있는 압축천연가스(CNG) 저장용기는 무게와 강성의 효율을 위하여 복합재료를 사용하여 외부를 보강하는 새로운 형태의 구조를 사용하고 있다. 이러한 다층 복합소재의 사용으로 기존의 손상탐지기법으로는 저장용기의 외부에서 가해지는 충격 혹은 결함에 의한 저장탱크에 발생한 손상의 측정이 매우 어렵게 되었다. 이러한 한계를 극복하기 위하여 본 연구에서는 선행연구를 통하여 개발된 에너지 기반 contour D/B map 기법을 이용하여 4 가지 형식의 CNG 저장탱크에 발생한 외부 충격 신호의 손상 위치를 측정하였다. 각각의 형식의 저장탱크에서 측정된 손상 위치 결과를 비교 분석하여 새로운 기법의 측정 성능을 알아보았다.