본 연구의 목적은 그래핀(Graphene)을 사용하여 폴리우레탄 나노웹(Polyurethane Nanoweb)에 전기전도성을 부여하고, 이를 이용하여 나노웹 기반의 스트레인센서(Strain Sensor)를 개발하는 것이다. 이를 위해 1% 그래핀 잉크를 폴리우레탄 나노웹에 푸어코팅(Pour-coating)한 후 PDMS(Polydimethylsiloxane)로 후처리를 하여 착용 가능한 스트레 인센서를 완성하였다. 시료 표면에 전도성 물질이 잘 코팅되었는지 확인하기 위해 전계방사형 주사전자현미경 (FE-SEM)를 이용하여 시료의 표면 특성을 평가하였다. 시료의 전기적 특성 평가는 멀티미터(Multimeter)를 사용하여 시료의 선저항(Linear Resistance)을 측정하고, 시료를 각각 5%, 10% 인장하였을 때 선저항이 어떻게 변하는지 비교하였다. 또한 시료의 성능을 평가하고자 게이지율(Gauge Factor)을 구하였다. 착의평가 실험은 완성된 스트레인센서를 더미에 착용시킨 후 MP150(Biopac system Inc., U.S.A.)과 Acqknowledge(ver. 4.2, Biopac system Inc., U.S.A.)를 사용해 인장에 따른 호흡신호를 측정하였다. 표면 특성을 평가한 결과, 모든 전도성 나노웹 시료들이 그래핀 잉크로 균일하게 코팅되어있음을 확인하였다. 인장에 따른 저항값 측정 결과, 그래핀을 처리한 시료인 시료 G가 가장 낮은 저항값을, 그래핀을 처리한 후 열처리를 한 시료인 시료 G-H가 가장 높은 저항값을 가졌고, 시료 G와 시료 G-H의 경우 길이가 5%, 10%로 늘어남에도 선저항값의 변화가 안정적으로 증가하는 것으로 나타났다. 저항값 결과와는 달리, 시료 G가 시료 G-H보다 더 높은 게이지율을 보였다. 실제로 착의평가 결과, 시료 G-H를 이용해 만든 스트레인센서가 안정된 Peak값으로 측정되어 좋은 품질의 신호를 얻었다. 그러므로 본 연구를 통해 그래핀 잉크를 처리한 폴리우레탄 나노웹이 호흡 센서로서의 역할을 충분히 수행하는 것을 확인하였다.

The dissertation is on the measurement of the strain caused by the characteristics and the temperature changes of the TIG welded zone which is used with 3D ESPI system that is functionally modified through the laser ESPI system. Experimental results have derived from the fact that the welded zone has micro crack during the various phased of the process such as rolling, alkali cleaning, air cooling and heat processing due to the repetitious up-and-down of the temperature. Especially, both 60℃ and 90℃ are selected to measure the strain on the welded zone which can be effected by these two temperatures in the manufacturing process. The flat plate differences between ESPI and the strain gage are within 2 %, and they are the exactly same with the results from the temperature changes of 60 ℃ and 90 ℃, and also within 3 % and 4 %. As the tensile load increase, the strain of aluminum material increases linearly. Also the same effect are observed as the temperature goes up with irregular-line type. The comparison of the strain by ESPI and the strain gage in the welded specimen is within the 2.6% when it is under the room temperature and low-load conditions, while it is measured within 3 % under the high load condition.

PURPOSES: The purpose of this study is to provide the method of how to measure the coefficient of thermal expansion of concrete using temperature compensation principle of electrical resistance strain gauge. METHODS : The gauge factor compensation method and thermal output(temperature-induced apparent strain) correction method of selftemperature compensation gauge were investigated. From the literature review, coefficient of thermal expansion measurement method based on the thermal output differential comparison between reference material(invar) and unknown material(concrete) was suggested. RESULTS: Thermal output is caused by two reasons; first the electrical resistivity of the grid conductor is changed by temperature variation and the second contribution is due to the differential thermal expansion between gauge and the test material. Invar was selected as a reference material and it、s coefficient of thermal expansion was measured as 2.12×10-6m/m/℃. by KS M ISO 11359-2. The reliability of the suggested measurement method was evaluated by the thermal output measurement of invar and mild steel. Finally coefficient of thermal expansion of concrete material for pavement was successfully measured as 15.45×10-6m/m/℃. CONCLUSIONS: The coefficient of thermal expansion measurement method using thermal output differential between invar and unknown concrete material was evaluated by theoretical and experimental aspects. Based on the test results, the proposed method is considered to be reasonable to apply for coefficient of thermal expansion measurement.

dynamic strain gage와 12bit AD(analog to digital converter)를 이용한 새로운 제진특성 측정 장치를 제작하였다. 이 장치를 이용하여 일반재료와 고제진재료의 제진특성을 연구하였다. 또한 열처리 조건, 초기 진동 진폭, 그리고 내부응력의 변화에 따른 SDC(specific damping capacity)변화에 관하여 연구하였다. 일반재료와 제진재료의 비교에서, 제진재료는 진동을 가한 후 0.4초 이내에 진동 진폭이 거의 사라졌지만, 같은 시간에 일반재료의 진동 진폭은 거의 감소하지 않았다. Fe-16wt. %Cr계 합금의 제진 특성은 노냉일 때 SDC max 가 40%이상이었고, Fe-5.5wt.%Ai합금의 제진 특성은 공냉일 때 SDC max값이 30%이상이었다. 초기 진동 진폭이 증가할수록 최대 제진 특성치는 낮은 진동 진폭 영역으로 이동하였다. 제진 특성은 내부 응력이 증가할수록 급격한 감소를 보였으며, 본 연구에서 개발한 제진측정 장치는 낮은 진동 진폭의 영역에서 정확한 제진 특성 측정이 가능하였다.

This study presents a technique for measuring the local strain of RC columns using high strength materials. A acrylic rod with strain gauges at intervals of 5 mm were embedded in high-strength RC columns. Under uniaxial compression loading, the local strain of the column was measured with strain gauges attached to the acrylic rod. It was confirmed from experimental results that the technique applied in this study is very effective in measuring the local strain of high-strength RC columns and the compressive failure of the high-strength RC columns is concentrated in some local regions.

Distributed optical fiber sensors have been developed to detect the occurrence of structural anomalies such as excessive stresses, cracks, and leaks at arbitrary locations in the facility. In this paper, we demonstrate fiber optic OFDR (Optical Frequency Domian Reflectometry) sensor to measure strain and temperature through the sensing optical fiber. A PVC pipe was prepared to show the strain measurement performance with a sensing optical fiber attached on the pipe. Also, a temperature test was performed with a sensing optical fiber located in a temperature chamber. In the results, this sensor can operate to resolve 14.2 micro strain and 1.62 degree temperature at the condition of 5 cm spatial resolution.

Recently, an indirect displacement estimation method using data fusion of acceleration and strain (i.e., acceleration-strain-based method) has been developed. This paper proposes an improved displacement estimation method that can be applied to more general types of bridges by building the mapping using the finite element model of the structure. An experimental validation of the proposed method was carried out on a prestressed concrete girder bridge, and the method provides the best estimate for dynamic displacements.

Strain gauges is the most common device for measuring strain. Since the electric resistance of strain gauge changes only a little, strain gauges are almost always used in a bridge configuration with a excitation source. In this study, a strain measuring method, which calculate strain by reading a resistance of strain gauge, are investigated and verified.

It is very important to measure and monitor hull stress which is caused by a buoyant force and a weight of cargo for safety of ship. However, an exact measurement of hul stress, using the traditional strain gage which is made of metal or semiconductor, is very difficult, because a ship would be exposed by the severe temperature environment of -20 ℃ to 80 ℃. This paper propose a new concept strain gage which can improve accuracy and compensage effectively affects due to temperature. The strain gage is consists of two parts. One is the Hull Deformation Amplifier which introuce several lever and link system, and another is a transducer converting distance into voltage signal. The HDA measure the amount of deformation and amplify it. And a lever and link system of the HDA is introduced for compensating temperature deformation by installing in perpendicular direction without stress. This paper also reports on the results of the experiments to verify linearity of the strain gage.