• International Journal of Aerospace System Engineering
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• 제2권2호
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• pp.24-28
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• 2015

Composite materials are highly sensitive to the presence of manufacturing and service-related defects that can reach a critical size during service condition and thereby may affect the safety of the structure. When the structure undergoes some kind of damage, its stiffness reduces, in turn the dynamic responses change. In order to avoid safety issues early detection of damage is necessary. The knowledge of the vibration behavior of a structure is necessary and can be used to determine the existence as well as the location and the extent of damage.

• 비파괴검사학회지
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• 제35권3호
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• pp.185-192
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• 2015

동적하중에서의 베어링 결함에 대한 실시간 진단기술은 상대적으로 저조하다. 따라서 볼베어링의 이상상태 현상으로 인한 온도 상승 및 진동 증가 등을 사전에 검출하는 기술이 필요하며, 회전체에 대한 운전상태 감시 및 손상 진단을 통해 발전설비의 원활한 운전을 기할 수 있는 검출 기술이 필요하다. 적외선 열화상 실험과 더불어 ANSYS를 이용한 유한요소해석으로부터 실험과 동일한 베어링을 구조 설계 및 해석하여 데이터를 분석함으로써 열화상 기술로 얻은 데이터의 신뢰성을 확보하였다.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2008년도 추계학술발표대회 논문집
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• pp.280-287
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• 2008

In case of low pressure steam turbine used in power plant, it was operated in wet steam and high stress condition. Therefore, it is possible that the corrosion damage of low pressure was induced by this condition. According to previous study, about 30% of total blade failure correspond to corrosion fatigue or SCC(stress corrosion cracking) in low pressure turbine. Especially, LSB(last stage bucket) of low pressure turbine has a higher hardness to prevent erosion damage due to water droplet however, generally this is more dangerous for SCC damage. Therefore, to improve reliability of turbine blade. various methods for SCC evaluation has been developed. In this study, the crack found in LSB during in-service inspection was evaluated using microstructure analysis and stress analysis. From the stress analysis, the optimum size of fillet to remove the crack was proposed. And also, the reliability was evaluated for modified LSB using GOODMAN diagram.

• 대한조선학회논문집
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• 제56권3호
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• pp.231-241
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• 2019

In this study, a simplified analysis method was developed to evaluate the fatigue damage of an ice-going ship under broken ice condition. The global ice load, which is essentially calculated at the design stage of the Arctic vessel, and the hull form information were used to estimate the local ice load acting on the outer-shell of the ship. The local ice load was applied to the finite element analysis model, and the Weibull parameters for the target fatigue point were derived. Finally, fatigue damage was evaluated by applying the S-N curve and the Palmgren-Miner rule. For the verification of the proposed method, numerical analyses using direct approach were performed for the same conditions. A numerical model that implements the interaction between ice and structure was introduced to verify the local ice load and the stress calculated from the proposed method. Finally, the fatigue analyses of the Baltic Sea for actual ice conditions were performed, and the results of the proposed method, the method using numerical analysis, and the LR method were compared.

• Composites Research
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• 제22권1호
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• pp.1-8
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• 2009

본 논문에서는 면내하중을 받는 복합적층판의 저속충격거동과 손상을 해석하였다. 초기부터 존재하는 면내변형률을 고려하여 판의 변위장을 새롭게 가정하고, 이 가정된 변위장에 따른 적층판의 구조거동에 대한 유한요소방정식을 유도하였으며, 유한요소해석 프로그램을 코딩하였다. 유한요소해석을 수행하여 참고문헌의 수치해석 결과와 비교하였으며, 충격에너지는 동일하나 충격체의 질량과 속도가 다른 조건에 대해서도 해석하여 초기 면내하중의 영향을 분석하였다. 바닥으로부터 첫 번째 층간면에서의 잠재적인 층간분리 파손영역을 추정하여 초기 인내하중 및 충격조건에 따른 크기의 변화를 고찰하였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2003년도 사면안정학술발표회
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• pp.3.1-11
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• 2003

Recently the problems related to the failure of the retaining wall structure has become great concern since the damage to the properties and human losses have occurred in the rainy season. However, a detail guideline on safety inspection and appropriate diagnosis on the retaining wall structure have not yet proposed and therefore, the inspection process and results are mainly dependant upon the engineers. The objective of this study is to propose objective and quantitative evaluation method for the condition based on the damage shapes and material types. In this purpose, composing materials of retaining wall are divided Into concrete, gabion, stone and reinforced earth, and then the evaluation items and method are suggested on the basis of the materials and structural characteristics of the retaining wall.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.465-466
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• 2002

In any mechanical system consisting of gears, shafts and/or bearings, the majority of metallic particles deposited into and carried by the lubrication system originate from the deterioration of oil-wetted working surfaces, even in proper lubrication system, due to failure mechanism (s) such as wear, fatigue and fretting corrosion. Determination of the point at which transition from normal to abnormal or to actual damage occurs has become a focus of attention in research activities for years, because it has been recognized that reliable, economic operation can be achieved through appropriate preventative measures. Known collectively from 'all size wear debris analysis' as early failure detection, the methods of testing for damage differ considerably, range from a micron or a submicron size debris analysis to Magnetic Chip Detector (MCD) ferrous debris analysis. This paper will be focused on the utilization of the low-cost analysis techniques for evaluation of industrial machinery condition.

• 대한기계학회논문집A
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• 제27권6호
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• pp.981-986
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• 2003

In order to investigate the possibility of processing of brittle material by ball impact, the effects of boundary conditions about impact damage of soda-lime glass by small spheres were evaluated experimentally. It was investigated that crack appearance developed in soda-lime glass with boundary conditions of without sealing, single-sealing and double-sealing by impact velocity. The double-sealing was most effective in the development of perfect cone than other boundary condition. In case of double-sealing condition, PVC and Polyurethane sealing were more effective in producing a perfect cone formation than other sealing materials. The impact velocity range over which perfect cones were formed was influenced by both the contact area and diameter of impact particle.

• 고문화
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• 64호
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• pp.111-131
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• 2004

대학박물관에서 전시 또는 수장되는 유물들은 현재의 시설 및 환경조건에서도 미생물(세균, 곰팡이)에 의 한 손상과 훼손을 방지하여 보존되어야 한다. 그러기에, 대학박물관의 보존환경 실태를 분석, 파악하여 박물관 내 전시 및 수장유물에의 생물학적 환경을 조사하고 이에 대한 이상적이고, 최적의 보존환경을 설정하여야 한다. 이에 지역별 대학박물관(대구한의대학교, 부산대학교, 성신여자대학교, 숭실대학교, 연세대학교, 용인대학교, 전북대학교, 전주대학교, 조선대학교, 한림대학교, 한양대학교)을 선정하여 전시실과 유물 및 수장고의 보존환경을 조사하여 이를 평가 분석하여 최적의 보존환경 보존 지침(Guide Line)을 설정하고자 하였다. 그 결과, 수장고에서 문화재의 유물을 손상시키는 유해미생물을 분리하였고, 전시실 및 수장고에서 근무하는 근무자들에게 호흡기 및 피부질환을 일으킬 수 있는 병원미생물을 분리하여 그 특성을 규명하였으며, 이와 같은 생물학적 열화 예방을 위하여 대학박물관의 가장 효율적인 방제 방안을 설정하고자 이 연구를 수행하였다.

• Corrosion Science and Technology
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• 제20권3호
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• pp.143-151
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• 2021

In this study, optimal shot peening process conditions were investigated for improving the cavitation erosion resistance of gray cast iron under a marine environment. Shot peening was performed with variables of injection pressure and injection time. The durability was then evaluated through cavitation erosion test which was conducted according to the modified ASTM G-32 standard. The tendency of cavitation erosion damage according to shot peening process condition was investigated through weight loss rate, surface and cross-sectional analysis of the specimen before and after the test. As a result, the shot peening process condition that could minimize cavitation erosion was when the injection pressure was the lowest and when the injection time was the shortest. This was because the flake graphite exposed on the gray cast iron surface could be easily removed under such condition. Therefore, the notch effect can be prevented by surface modification. In addition, the cavitation erosion damage mechanism of gray cast iron was discussed in detail.