• Nuclear Engineering and Technology
• /
• 제55권12호
• /
• pp.4647-4658
• /
• 2023

In this paper, elastic-plastic fracture mechanics analysis is performed to determine the critical crack sizes of the multipurpose canister (MPC) manufactured using austenitic stainless steel under dynamic loading conditions that simulate drop accidents. Firstly, dynamic finite element (FE) analysis is performed using Abaqus v.2018 with the KORAD (Korea Radioactive Waste Agency)-21 model under two drop accident conditions. Through the FE analysis, critical locations and through-thickness stress distributions in the MPC are identified, where the maximum plastic strain occurs during impact loadings. Then, the evaluation using the failure assessment diagram (FAD) is performed by postulating an external surface crack at the critical location to determine the critical crack depth. It is found that, for the drop cases considered in this paper, the principal failure mechanism for the circumferential surface crack is found to be the plastic collapse due to dominant high bending axial stress in the thickness. For axial cracks, the plastic collapse is also the dominant failure mechanism due to high membrane hoop stress, followed by the ductile tearing analysis. When incorporating the strain rate effect on yield strength and fracture toughness, the critical crack depth increases from 10 to 20%.

• 한국융합학회논문지
• /
• 제11권10호
• /
• pp.267-277
• /
• 2020

본 연구는 재창업기업 대표를 대상으로 실패내성이 탐색 활동 및 활용 활동에 미치는 영향과 이러한 활동들이 경영성과에 미치는 영향을 고찰하였다. 최근 재창업을 지원하는 정책적, 사회적 지원이 높아지고 있다. 본 연구는 재창업자의 심리적 요인이 경영성과와 관계가 있는지 검증하고자 한다. 따라서, 심리 및 교육학 변수인 실패내성과 경영학 변수인 경영성과를 융합한 연구모형을 제시하고, 이를 실증 분석하였다. 연구대상은 중소벤처기업진흥공단으로부터 재창업 자금을 지원받은 재창업자를 대상으로 실시하였다. 재창업자의 심리적 특성인 실패내성과 탐색 및 활용 활동에 미치는 영향을 분석한 결과, 모두 긍정적인 영향을 미치는 것으로 나타났고, 탐색 및 활용 활동이 경영성과에 미치는 영향을 분석한 결과, 탐색 활동은 영향을 미치는 않는 것으로 나타났고, 활용 활동은 긍정적인 영향을 미치는 것으로 나타났다. 이 같은 연구 결과를 바탕으로 이론적 시사점과 실무적 시사점을 제공하고자 한다.

• 대한조선학회논문집
• /
• 제41권6호
• /
• pp.75-83
• /
• 2004

Ice rubble pieces broken by the bow impact load and side hull of an icebreaking vessel usually pass along the ship's bottom hull and may hit the propeller/rudder or other stern structures causing serious damage to ship's hull . Therefore it is important to estimate the size of broken ice pieces during the icebreaking process. The dynamic interaction process of icebreaker with infinite ice sheet is simplified as a wedge type beam of finite length supported by elastic foundation. The wedge type ice beam is leaded with vertical impact forces due to the inclined bow stem of icebreaking vessels. The numerical model provides locations of maximum dynamic bending moment where extreme tensile stress arises and also possible fracture occurs. The model can predict a failure length of broken ice sheet given design parameters. The results are compared to Nevel(1961)'s analytical solution for static load and observed pattern of ice sheet failure onboard an icebreaker. Also by comparing computed failure length with the characteristic length, the meaning of ice rubble sizes is discussed.

• 품질경영학회지
• /
• 제40권1호
• /
• pp.25-38
• /
• 2012

Service FMEA may yield several possible corrective actions for each failure mode with large RPN. Corrective actions for each service failure are usually interrelated with the customers and environmental elements of the service system. SWOT analysis can provide an effective way to analyze the inner and outer environmental impacts for each corrective action. In this paper, we suggest a way for selecting and ranking corrective strategy in service operation based on SWOT analysis. Every candidate of corrective action strategy is ranked and evaluated on the basis of the impact factors of the SWOT variables, correlations between possible corrective actions and SWOT variables, and RPNs of service failures. The most desirable set of corrective actions is selected considering the preference score of each corrective action, required resources and budgetary allowance. The proposed methodology is demonstrated with an illustrative example.

• 한국산업정보학회논문지
• /
• 제17권3호
• /
• pp.27-34
• /
• 2012

This paper presents the impact of time dependent dielectric breakdown (TDDB, also called as gate oxide breakdown) failure on nanoscale digital CMOS Circuits. Recently, TDDB for ultra-thin gate oxides has been considered as one of the critical reliability issues which can lead to performance degradation or logic failures in nanoscale CMOS devices. Also, leakage power in the standby mode can be increased significantly. In this paper, TDDB aging effects on large CMOS digital circuits in the 45nm technology are analyzed. Simulation results show that TDDB effect on MOSFET circuits can result in more significant increase of power consumption compared to delay increase.

• 한국통신학회논문지
• /
• 제42권1호
• /
• pp.88-97
• /
• 2017

With the increasing of the penetration rate of large-scale wind farms, a reliable, highly available and cost-effective communication network is needed. As the failure of a WF communication network will significantly impact the control and real-time monitoring of wind turbines, network reliability should be considered into the WF design process. This paper analyzes the network reliability of different WF configurations for the Southwest Offshore project that is located in Korea. The WF consists of 20 WTs with a total capacity of 60 MW. In this paper, the performance is compared according to a variety of indices such as network unavailability, mean downtime and network cost. To increase the network reliability, partial protection and full protection were investigated as strategies that can overcome the impact of a single point of failure. Furthermore, the reliability performances of different network architectures are analyzed, evaluated and compared.

• 한국해양공학회지
• /
• 제1권2호
• /
• pp.52-59
• /
• 1987

극 지역용 중력식 해양구조물의 설계시 고려되어야 할 문제중의 하나가 구조물의 유빙(ice)과 충돌시 야기되는 foundation붕괴 현상인데, 본 논문에서는 정적 해석을 위해 sliding 및 bearing failure 현상에 대하여만 연구하였고, 또한 동적 해석을 위하여 soil과ice의 특성으로부터 structure-ice-soil의 상호 작용 운동 방정식을 설정하여 구조물과 ice의변위, 속도, 가속도와 ice force와 soil force의 history를 시간영역 해법으로 풀었다. 한 예제로 Beaufort Sea의 37 feet수심과 granular soil 상태에서 구조물의 최대변위는 0.4 feet이고 가속도는 약 0.3kg이며 이때 구조물이 sliding에 대하여 안전하다는 것이 입증되었다.

• Ocean Systems Engineering
• /
• 제9권2호
• /
• pp.135-155
• /
• 2019

One of the safest and the most economical methods to transfer oil and gas is pipeline system. Prediction and prevention of pipeline failures during its assessed lifecycle has considerable importance. The dropped object is one of the accidental scenarios in the failure of the submarine pipelines. In this paper, using Monte Carlo Sampling, the probability of damage to a submarine pipeline due to a box-shaped dropped object has been calculated in terms of dropped object impact frequency and energy transfer according to the DNV-RP-F107. Finally, Reliability sensitivity analysis considering random variables is carried out to determine the effect intensity of each parameter on damage probability. It is concluded that impact area and drag coefficient have the highest sensitivity and mass and add mass coefficient have the lowest sensitivity on probability of failure.

• 폴리머
• /
• 제26권2호
• /
• pp.270-278
• /
• 2002

저밀도 2-D 탄소/탄소 복합재료의 저속 충격에 의한 파괴 거동과 첨가제에 따른 충격 에너지 흡수 경향을 연구하였다. 저속 충격시험은 mini tower 낙추 충격 시험기를 이용하였으며, 흑연, 카본블랙, 분쇄탄소섬유를 첨가제로 선택하였다. 흑연의 첨가는 최대하중값을 증가시켰으며, 전체적인 관통이 일어나기까지 응력을 오랫동안 유지시키는 효과를 나타내었다. 특히 9 vol%의 함량에서 흑연이 첨가되지 않은 씨편보다 약 42%의 충격 흡수 개선을 보였다. 약 0.4 J의 낮은 충격에너지에 의한 충격 회수에 따른 실험에서 첨가제가 첨가되지 않은 시편의 경우, 충격에너지는 층간분리에 의해 소모되고, 흑연의 함량이 증가함에 따라 파괴 경향은 시편의 관통으로 변화함을 관찰할 수 있었다.

• Nuclear Engineering and Technology
• /
• 제55권3호
• /
• pp.981-988
• /
• 2023

A seismic event caused an accident at the Fukushima Nuclear Power Plant, which further resulted in simultaneous accidents at several units. Consequently, this incident has aroused great interest in the safety of nuclear power plants worldwide. A reasonable safety evaluation of such an external event should appropriately consider the correlation between SSCs (structures, systems, and components) and the probability of failure. However, a probabilistic safety assessment in current nuclear industries is performed conservatively, assuming that the failure correlation between SSCs is independent or completely dependent. This is an extreme assumption; a reasonable risk can be calculated, or risk-based decision-making can be conducted only when the appropriate failure correlation between SSCs is considered. Thus, this study analyzed the effect of the failure correlation of SSCs on the safety of the system to realize rational safety assessment and decision-making. Consequently, the impact on the system differs according to the size of the failure probability of the SSCs and the AND and OR conditions.