• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.86-95
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• 2006

Brillouin backscatter is a type of reflection that occurs when light is shone into an optical fibre. Brillouin reflections are very sensitive to changes in the fibre arising from external effects, such as temperature, strain and pressure. We report here several case studies on the measurement of strain using Brillouin reflections. A mechanical bending test of an I beam, deployed with both fiber optic sensors and conventional strain gauge rosettes, was performed with the aim of evaluating: (1) the capability and technical limit of the DTSS technology for strain profile sensing; (2) the reliability of strain measurement using fiber optic sensor. The average values of strains obtained from both DTSS and strain gauges (corresponding to the deflection of I beam) showed a linear relationship and an excellent one-to-one match. A practical application of DTSS technology as an early warning system for land sliding or subsidence was examined through a field test at a hillside. Extremely strong, lightweight, rugged, survivable tight-buffered cables, designed for optimal strain transfer to the fibre, were used and clamped on the subsurface at a depth of about 50cm. It was proved that DTSS measurements could detect the exact position and the progress of strain changes induced by land sliding and subsidence. We also carried out the first ever distributed dynamic strain measurement (10Hz) on the Korean Train eXpress(KTX) railway track in Daejeon, Korea. The aim was to analyse the integrity of a section of track that had recently been repaired. The Sensornet DTSS was used to monitor this 85m section of track while a KTX train passed over. In the repaired section the strain increases to levels of 90 microstrain, whereas in the section of regular track the strain is in the region of 30-50 microstrain. The results were excellent since they demonstrate that the DTSS is able to measure small, dynamic changes in strain in rails during normal operating conditions. The current 10km range of the DTSS creates a potential to monitor the integrity of large lengths of track, and especially higher risk sections such as bridges, repaired track and areas at risk of subsidence.

• 한국구조물진단유지관리공학회 논문집
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• 제6권3호
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• pp.193-199
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• 2002

콘크리트 구조물에 발생하는 구조적인 균열은 재하하중에 의하여 콘크리트가 저항할 수 있는 인장강도보다 더 큰 인장강도가 가해졌을 때 콘크리트의 인장영역에서 발생하며, 이는 구조물의 노후화 또는 재하하중에 대한 저항능력이 감소되었음을 의미한다. 그러므로 콘크리트에 발생한 구조적 균열은 구조물에 치명적인 손상을 유발시킬 수 있으며, 구조물의 안전성 확보와 효과적인 유지관리를 위해서는 이를 검출하는 기법에 대한 연구가 반드시 필요한 실정이다. 본 연구에서는 토목계측 분야에서 가장 널리 활용되고 있는 변형률 센서를 철근콘크리트 보에 부착하여 보의 인장부와 압축부의 변형률을 측정하는 실내실험을 수행하였으며, 하중 재하에 따른 변형률의 변화, 측정부위의 탄성계수 변화, 그리고 중립축의 변화 등을 비교 분석하였다. 분석 결과로부터, 측정된 변형률을 이용하여 중립축의 변화 추이를 추정하므로써 가장 효과적으로 균열을 검출할 수 있는 알고리즘을 제시하였다.

• Advances in concrete construction
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• 제11권5호
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• pp.375-386
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• 2021

In this paper, a study of stability and health of a newly-built railway tunnel is presented. The field test was implemented to monitor the secondary lining due to the significant cracking behaviors influenced the stability and health of the tunnel structure. Surface strain gauges were installed for monitoring the status of crack openings, and the monitoring outputs demonstrated that the cracks were still in the developing stage. Additionally, adjacent tunnel and poor condition of surrounding rock were identified as the causes of the lining cracking by systematically characterizing the crack spatial distribution, tunnel site and surrounding rock conditions. Reconstruction of partial lining and reconstruction of the whole secondary lining were designed as the maintenance projects for different cracking regions based on the construction feasibility. For assessing the health conditions of the reinforced lining, embedded strain gauges were set up to continuously measure the strain and the internal force of the reconstructed structures. For the partially reconstructed lining, the outputs show the maximum tensile elongation is 0.018 mm during 227 days, which means the structure has no obvious deformation after maintenance. The one-year monitoring of full-section was implemented in the other two completely reconstructed cross-sections by embedded strain gauge. The outputs show the reconstructed secondary lining has undertaken the pressure of surrounding rock with the time passing. According to the calculated compressive and tensile safety factors, the completely reconstructed lining has been in reliable and safe condition during the past year after reinforcement. It can conclude that the aforementioned maintenance projects can effectively ensure the stability and health of this tunnel.

• 센서학회지
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• 제31권6호
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• pp.411-417
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• 2022

In this paper, we propose a sensor with a C-shaped load cell to detect force change when a person sitting on the chair in an electrical transport-convenience vehicle is pushing ground by both heels. The load cell built in the vehicle is mechanically deformed by the vertical force owing to the human weight and the horizontal force by ground-pushing feet. The deformation rate of the load cell and its distribution are simulated using finite element analysis. In the simulation, the applied loads are preset in the range of 10 kg - 100 kg with a step size of 10 kg, and the ground-pushing force by feet is increased to 40 N with a step size of 5 N with respect to each applied load level. The resistance change of the load cell was observed to be linear in simulation as well as in measurement. the maximum difference between simulation and measurement was 0.89 % when the strain gauge constant was 2.243. The constant has a large influence on the difference. The proposed sensor was fabricated by connecting an instrument amplifier and a microcontroller to a load cell and used to detect the force by ground-pushing feet. To detect foot driving, the reference signal was set to 130% of the load, and the duration of the sensor output signal exceeding the reference signal was set to 0.6 s. In a test of a vehicle built with the proposed sensor, the footpushing force by the worker could be successfully detected even when the worker was working.

• 한국공작기계학회논문집
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• 제13권6호
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• pp.127-134
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• 2004

As the result of reduction of the barrier of national economy on matters of quality assurance of weighing instruments in recently, it is considering in domestic as well as international matters. Therefore, this study is to analysis and compare with international md national measuring standards on the electric self-indicating scale, to improve the quality of electronic machine by providing a reformation plan on currently problems of domestic manufactured, and to identify to introduce in domestic criteria from international standards. I had compared KSC 1313 to OIML R 76-1 as the performance assessment items, such as metrology Properties test, static temperature test, temperature effect testing under the un-load, electronic wave disturbance test, high-tempereature and high-humidity stability test and durability test. Therefore, only one company is passed all items of the test according to the international (reference) standards, but it is possible to improve the quality in general if it should be use the load cell and electric components which is stability of temperature change in order to supplementation to the static temperature test and temperature effect testing under the un-load. It is also possible to apply in the domestic with the OIML 76-1 after correcting the design.

• 산업기술연구
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• 제43권1호
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• pp.7-13
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• 2023

Nowadays, traffic congestion is emerging as a major problem due to the rapid population growth and the increase in automobiles. The train is a convenient means of transportation that can efficiently solve these problems. Trains have been developed in line with human aspirations for a long time, but research on safety is still insufficient. This study aims to check safety by conducting static tests and fatigue tests on bogie frames, and to help develop bogie frames in the future. For the static test, a strain gauge was attached to the point where the local stress concentration was expected beforehand, and the result value was derived, compared with existing theories, and expressed as a Goodman diagram. In the fatigue test, a total of 10 million loads were applied over three stages, and no cracks appeared in the non-destructive test conducted after each stage. Both tests were conducted according to the strict test method of the bogie frame presented by the UIC Code. It satisfied both fatigue life and strength evaluation criteria and was judged to be a bogie frame usable for safe train production.

• Journal of Advanced Marine Engineering and Technology
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• 제40권7호
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• pp.593-598
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• 2016

LNG 선박용 성형 벨로우즈의 성형방법에 따른 특성을 파악하기 위하여 정적시험과 저주기 피로시험을 실시하였다. 벨로우즈의 규정된 수명 사이클인 8,000회를 실시하여 시험전후의 벨로우즈의 각 산에 걸리는 변형률과 응력을 측정하여 성형방법에 따른 벨로우즈간의 차이를 분석하고 산 별 응력분포를 살펴보았다. 본 저주기 피로시험은 x-y방향의 변위가 가능한 유압시스템의 구조시험장비에 성형 벨로우즈를 장착하고 벨로우즈의 각 산에는 스트레인게이지를 장착하고 멀티레코더를 통하여 데이터를 처리하였다. 이를 통하여 벨로우즈가 성형방법에 따른 수명의 차이가 있는지 살펴보았고, 성형방법에 따른 수명의 차이를 주는 원인을 분석하였다.

• 한국지반환경공학회 논문집
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• 제15권12호
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• pp.71-77
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• 2014

집중호우는 사면의 붕괴와 사회 기반시설물의 파괴 등을 포함하는 다수의 재해를 유발한다. 이러한 관점에서 강우재현 원심모형실험은 지반구조물의 안정성을 평가하기 위한 합리적인 수단이 될 수 있다. 원심모형실험에서 모형의 변위를 취득하기 위하여 일반적으로 LVDT 또는 레이저 변위계가 사용된다. 그러나 강우모사 시 LVDT는 모형지반으로의 과다 침윤의 문제가 있으며, 레이저 변위계는 레이저의 산란에 의해 계측치의 정확성이 저하된다. 따라서 본 연구에서는 강우재현 원심모형실험에 적용하기 위한 수평변위 계측장치를 개발하였다. 본 연구를 통하여 탄성의 박철판과 스트레인 게이지를 이용하여 제작된 본 장치는 관입을 위한 말단부를 고정시켜 수행한 검정 결과로부터 정확한 변위-변형률 관계를 나타냄을 확인하였다.

• 대한소아치과학회지
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• 제33권4호
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• pp.606-614
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• 2006

이 연구의 목적은 이장재의 종류에 따른 광중합형 복합레진 충전 후 중합수축을 비교함으로써 중합수축 감소를 보이는 좀 더 우수한 재료의 조합을 모색하고자 시행되었다. 이장재로는 유동형 레진, 컴포머, 광중합 글래스아이오노머를 사용하였고 수축응력을 측정하기 위해 스트레인 게이지를 사용하였다. 표본은 광원의 종류, 이장재의 종류에 따라 8개의 군으로 나눠졌다. 스트레인 게이지를 아크릴릭 링에 부착하고 strainmeter에 연결한 후 각 군에 따라 이장재 적용 후 광중합 하고 이장재 중합 후 750초간 수축응력을 측정하였다. 결과는 Repeated measures ANOVA와 Tukey test를 이용해 통계학적으로 분석하였다. 이상의 실험을 통해 얻은 결과는 다음과 같다. 1. 이장재를 사용하지 않은 군보다 이장재를 사용한 군의 중합수축이 적었으나 Ionosit을 사용한 군에서는 유의한 차이는 없었다(p>0.05). 2, Tetric flow 또는 Vitrebond를 이장재로 사용하는 것이 Ionosit을 사용하는 것보다 중합 수축이 적었다(p<0.05). 3. Tetric flow 이장재를 한 군은 광원에 따른 수축력의 차이가 적었고 Vitrebond와 Ionosit 이장재를 한 군은 할로겐 광원보다 LED 광원에서 수축응력이 컸으나 유의한 차이는 없었다(p>0.05).

• Tribology and Lubricants
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• 제19권6호
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• pp.321-328
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• 2003

In the present study, the residual stresses can have a significant on the life of structural engineering components. Residual stresses are created by the surface treatment such as shot peening or deep rolling. The objective of this experimental investigation is to study the influence of friction and wear characteristics due to residual stress under dry sliding condition. Friction and wear data were obtained with a specially designed tribometer. Test specimens were made of SUP9 (leaf spring material) after they were created residual stress by shot peening treatment. Residual stress profiles were measured at surface by means of the X­ray diffraction. Sliding tests were carried out different contact pressure and same sliding velocity 0.035 m/s (50 rpm). Leaf spring assembly test used to strain gauge sticked on leaf spring specimen in order to measure interleaf friction of leaf spring. Therefore, we were obtained hysteresis curve. As the residual stresses of surfaces increased, coefficient of friction and wear volume are decreased, but the residual stresses of surfaces are high, and consequently wear volume do not decreased. Coefficient of friction obtained from leaf spring assembly test is lower than that obtained from sliding test. From the results, structural engineering components reduce coefficient of friction and resistant wear in order to have residual stresses themselves.