• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.475-476
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• 2008

This paper is an experimental test for the close examination of breakdown causes of glass insulators using at the electric rail-road. The glass insulator is estimated the mechanical performance according to hitting test(ST-100, Sharp-Eng, KOR) that is based on KSC 3810. Insulators is damaged by pendulum weight at the steps of hitting angles. Glass and porcelain insulators are broken at the hitting angle of $72^{\circ}$. From the these results, glass insulator absorbed the impact from the pendulum weight but on the porcelain insulator, it is not transmitted vibration by impact. Hereafter, these results are expected that is used the data for the assessment on breakdown cause of a glass insulator.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.531-536
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• 2004

In-arm type hydropeumatic suspension unit(ISU) is an equipment of armed tracked vehicle to absorb impact load and vibration from the irregular ground. During the operation of ISU, main piston moves forward and backward and oil flowing through damper transmits the external impact load to floating piston. Heat is generated in ISU by the oil pressure drop through the damper orifice and the friction between cylinder wall and two pistons. On the other hand, internal heat dissipatis outside via heat convection. Occurrence of high temperature can deteriorate durability of major components and basic function of ISU. And, it can cause fatal problem in the ISU life time and the sealing performance of piston rings. As well, the spring constant change of nitrogen gas that is caused by the temperature rise exerts the negative effect to the vehicle stability. Therefore, in this paper, we analyze the heat transfer analysis of the entire ISU unit, by finite element method, with the outside flow velocities 8m/s and 10m/s.

• 한국정밀공학회지
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• 제33권8호
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• pp.661-668
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• 2016

Oil deflector prevents oil leakage that occurs in thermoelectric power plant at operating lubricant facilities. Vibration of rotating rotor-induced wear of aluminum tooth in existing oil deflector leads to oil leakage as well as life shortening of the tooth. In this study, an advanced oil deflector was developed for shock absorption and prevention of wear by decreasing clearance (from 0.5 mm to 0.2 mm) between rotor and tooth to minimize oil leakage, and by replacing 2 aluminum teeth in outmost of the oil deflector with hi-performance seal made of engineering plastic. The CFD results were compared between advanced vs. existing oil deflector to determine the amount of oil loss. Structural safety was verified through impact analyses according to the three kinds of engineering plastics, considering cost efficiency, and optimal material of hi-performance seal was chosen.

• 한국구조물진단유지관리공학회 논문집
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• 제6권4호
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• pp.209-217
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• 2002

The effects on structures caused by the replacement of the bridge bearings are investigated in this study. The bearings of the bridge are seriously deteriorated because of the breakage of lower concrete and the corrosion of the bearing itself. Also, the negative reaction states are created at some bearings on the abutment. Then, the bridge has occurred excessive vibrations and severe noise and impact whenever heavy trucks pass the above joints. The existing bearings are replaced using the adjustable bearing. The height of the bearings is adjusted to minimize the level difference of above joint and also to induce the appropriate distribution of live loads The effects of replacing the bearings are investigated by measuring the behaviors of the bridge without and with replacing works. The results without replacing the bearing show that the distribution of displacements and stresses is distorted in comparison with the analytical results. Also the bridge without replacing the bearing shows that the impact and vibration from the heavy trucks are larger than those with replacing the bearing. Load carrying capacity of the bridge increase about 1.8 times through replacing the bearing. The above results show that the structural performance of the bridge is improved by replacing only bridge bearings.

• Structural Engineering and Mechanics
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• 제59권1호
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• pp.133-151
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• 2016

Self-Compacting Concrete (SCC) has been originally developed in Japan to offset a growing shortage of skilled labors, is a highly workable concrete, which is not needed to any vibration or impact during casting. The utilizing of fibers in SCC improves the mechanical properties and durability of hardened concrete such as impact strength, flexural strength, and vulnerability to cracking. The purpose of this investigation is to determine the effect of steel fibers on mechanical performance of traditionally reinforced Self-Competing Concrete beams. In this study, two mixes Mix 1% and Mix 2% containing 1% and 2% volume friction of superplasticizer are considered. For each type of mixture, four different volume percentages of 60/30 (length/diameter) fibers of 0.0%, 1.0%, 1.5% and 2% were used. The mechanical properties were determined through compressive and flexural tests. According to the experimental test results, an increase in the steel fibers volume fraction in Mix 1% and Mix 2% improves compressive strength slightly but decreases the workability and other rheological properties of SCC. On the other hand, results revealed that flexural strength, energy absorption capacity and toughness are increased by increasing the steel fiber volume fraction. The results clearly show that the use of fibers improves the post-cracking behavior. The average spacing of between cracks decrease by increasing the fiber volume fraction. Furthermore, fibers increase the tensile strength by bridging actions through the cracks. Therefore, steel fibers increase the ductility and energy absorption capacity of RC elements subjected to flexure.

• Smart Structures and Systems
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• 제3권3호
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• pp.281-298
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• 2007

The load carrying capacity of a bridge needs to be properly assessed to operate the bridge safely and maintain it efficiently. For the evaluation of load carrying capacity considering the current state of a bridge, static and quasi-static loading tests with weight-controlled heavy trucks have been conventionally utilized. In these tests, the deflection (or strain) of the structural members loaded by the controlled vehicles are measured and analyzed. Using the measured data, deflection (or strain) correction factor and impact correction factor are calculated. These correction factors are used in the enhancement of the load carrying capacity of a bridge, reflecting the real state of a bridge. However, full or partial control of the traffic during the tests and difficulties during the installment of displacement transducers or strain gauges may cause not only inconvenience to the traffic but also the increase of the logistics cost and time. To overcome these difficulties, an alternative method is proposed using an excited response part of full measured ambient acceleration data by ordinary traffic on a bridge without traffic control. Based on the modal properties extracted from the ambient vibration data, the initial finite element (FE) model of a bridge can be updated to represent the current real state of a bridge. Using the updated FE model, the deflection of a bridge akin to the real value can be easily obtained without measuring the real deflection. Impact factors are obtained from pseudo-deflection, which is obtained by double-integration of the acceleration data with removal of the linear components on the acceleration data. For validation, a series of tests were carried out on a steel plategirder bridge of an expressway in Korea in four different seasons, and the evaluated load carrying capacities of the bridge by the proposed method are compared with the result obtained by the conventional load test method.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 춘계학술대회 논문집
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• pp.108-108
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• 2009

본 연구의 목적은 바지선에 의해 발생하는 해상풍속측정용 마스트 구조물의 충격손상을 최소화 시키기 위한 것이다. 마스트와 바지선 사이의 충격은 보통 복잡한 형태로 이루어진다. 충격해석은 상용유한요소해석 프로그램인 ANSYS LS-Dyna를 통하여 분석하였다. 바지선속을 변화시켜 다양한 상태의 하중케이스를 고려하였고 충격방지고무의 비선형성을 고려한 시간이력해석을 수행하였으며 변형률 에너지, 전체 변형량, 플라스틱 변형률, 내부충격에너지, 영구손상된 변형량 등을 검토하였다. 해상상태조건인 해양파의 운동과 바지선의 상하방향 운동을 무시하는 것으로 가정하였다. 충격속도에 변화에 따른 영구변형을 확인한 후 자연고무, 복합고무, 네오프렌 등의 고무시험 물성치로부터 구한 Mooney-Rivlin 상수를 적용하여 적절한 충격방지고무의 두께를 제안하였다. 본 연구를 통하여 구조물의 두께와 충격방지고무의 두께비에 대한 경향을 파악할 수 있으며 구조물의 설계에 적용할 수 있게 된다. 추후 해상조건을 고려한 연구를 수행해야 할 것이다.

• 한국구조물진단유지관리공학회 논문집
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• 제19권4호
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• pp.18-24
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• 2015

콘크리트구조물의 진단에 사용되는 비파괴실험법들은 구조물에 손상을 입히지 않고 구조물의 결함이나 강도를 추정할 수 있다는 장점이 있지만 추정값에 대한 신뢰성이 떨어진다는 문제점이 있다. 본 연구에서는 이러한 문제점을 해결하기 위해 2가지 배합으로 총 180개의 공시체를 제작하였고, P파와 S파에 의한 초음파속도 측정, 종진동과 변형진동에 의한 충격공진법 총 4가지의 비파괴실험을 실시하였다. 그리고 실제압축강도 측정을 통해 비파괴실험 결과값의 신뢰성을 비교 분석하였다. 각 비파괴실험법의 결과값에 대한 통계적 분석결과 변동계수값이 가장 낮은 실험법은 S파에 의한 초음파속도법으로 가장 안정적인 관측이 가능한 것으로 나타났다. 한편, 실제압축강도와의 관계를 통해 압축강도 4개의 압축강도 추정식을 제안하였으며 S파에 의한 초음파속도법의 결정계수값이 가장 높은 것으로 나타났다. 향후 다양한 배합조건에 따른 비파괴실험 신뢰성에 대한 보완 연구가 필요할 것으로 판단된다.

• 한국구조물진단유지관리공학회 논문집
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• 제21권5호
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• pp.30-41
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• 2017

소음 저감을 목적으로 설치되는 방음벽은 크게 흡음판과 방음판으로 나뉘며, 일조 및 경관을 저해하는 방음벽의 문제점을 해결하고자 투명 방음벽을 설치하는 것이 일반적 추세이다. 방음벽에 사용되는 투명 방음판의 소재는 여러 가지가 있으나 경우에 따라서는 황변현상과 재질변형 등으로 인해 투명도가 떨어지고 오염이 심해져 오히려 도시미관을 해하기도 한다. 따라서 이러한 단점을 보안하기 위하여 투명 방음판의 재질을 접합강화유리로의 대체가 가능하다. 본 논문은 메트로 지하철 고가교 상에서의 열차 유발진동에 따른 접합강화유리 방음판의 진동 및 풍하중에 의한 안전성을 분석하고, 접합강화유리 시스템 및 재료에 대한 휨능력 성능시험, 압축강도 및 탄성계수 시험, 충격시험 등을 수행하여 접합강화유리의 방음판으로서의 적정성을 평가하는 데 목적이 있다.

• Archives of Plastic Surgery
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• 제43권6호
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• pp.570-574
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• 2016

Background Fractional $CO_2$ laser is an effective treatment for scars, but most patients complain about sharp burning pain, even after the application of lidocaine ointment. This study analyzed the impact of a vibrating device to nonpharmacologically reduce the acute pain of laser treatment, in accordance with the gate control theory of pain management. Methods This is a prospective study performed from May 2013 through March 2014. Fifty-three patients (mean age, 26.7 years; range, 16-44 years) who had donated livers for liver transplantation were treated with a fractional $CO_2$ laser (10,600 nm; model $eCO_2$, Lutronic Corp) for their abdomen scars. Laser treatment was applied 4 months after surgery. A commercially available, locally applied vibrating device (model UM-30M, Unix Electronics Co. Ltd.) was used, in an on-and-off pattern, together with the $CO_2$ laser. A visual analogue scale (VAS; 0, no pain; 10, most severe pain) of pain sensation was assessed and statistically analyzed using a paired t-test. Results The average VAS score for pain with the vibrating device was 4.60 and the average VAS score without the vibrating device was 6.11. The average difference between scores was 1.51 (P=0.001). Conclusions A locally applied vibrating device was demonstrated to be effective in reducing pain when treating with a fractional $CO_2$ laser. Vibration treatment could be helpful when treating scars with fractional $CO_2$ laser in pain-sensitive patients, particularly children.