• 동력기계공학회지
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• 제15권3호
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• pp.65-69
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• 2011

This paper introduces the multi-coil eddy current sensor and its characteristic in magnetic material gas turbine rotor. In the past, magnetic particle inspection method was used for qualitative defect evaluation in magnetic material gas turbine rotor. And the ultrasonic inspection method was used for quantitative defect evaluation. Nowadays, eddy current method is used in magnetic gas turbine rotor inspection due to advanced sensor design technology. We developed multi-coil eddy current sensor for the rotor dovetail inspection. At first, rotor stress is analyzed for the determination of sensor position and number. The sensor coils are designed to cover the stress concentration area of rotor dovetail. We select optimum frequency according to material standard penetration data and experiment results. The rotor mock-up and artificial defects were made for the signal detection and resolution analysis of multi-coil eddy current sensor. The results show that signal detection and resolution capabilities are enhanced in comparison to the commercialized sensor enough for the gas turbine rotor inspection. So, this developed multi-coil eddy current sensor substituted for commercialized one and it applied in real gas turbine rotor inspection.

• 센서학회지
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• 제21권4호
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• pp.276-282
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• 2012

Vessels receive stress during their navigations as well as during their cargo operations. This stress may cause damages to the hull and may result in accidents. So the hull stress monitoring system(HSMS) is recommended in order to prevent these accidents. In this paper, we manufactured fiber Bragg grating(FBG) sensor and the model ship for towing tank experiments. The strain characteristics of the model ship on the water wave were measured through the towing tank experiment. The FBG sensors and electric strain gauges were attached on the connection jig, and then the characteristics of the FBG sensor were compared with those of the electric strain gauge. The strain of model ship was increased according to the increment of the amplitude of water wave. In particular, the largest strain was measured in the center of the model ship. As the wave period increased, the strain of model ship was decreased.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.790-793
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• 2005

In these days, the piezoresistive material has been applied to various sensors in order to measure the change of physical quantities. But the relationship between the sensitivity of a sensor and the position and size of piezoresistor has rarely been studied. Therefore, this paper was focused on the effect of residual stress induced in piezoresistor on the distribution of resistance change ratio and supposed the feasible position of piezoresistor. The resulting are following; The tensile residual stress in the vicinity of piezoresistor decreased the value of resistance change ratio and could not effect on all the area of diaphragm but local area around the piezoresistor. Also, the piezoresistor in the diaphragm type pressure sensor with boss should fabricate in the edge of boss in order to increase the sensitivity of pressure sensor.

• Structural Monitoring and Maintenance
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• 제7권1호
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• pp.1-12
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• 2020

Railway tracks are the direct supporting structures of the trains, which are vulnerable to produce large deformation under the temperature stress or subgrade settlement. The health status of track is critical, and the track should be routinely monitored to improve safety, lower the risk of excess deformation and provide reliable maintenance strategy. In this paper, the distributed optical fiber sensor was proposed to monitor the continuous deformation of the track. In order to validate the feasibility of the monitoring method, two deformation monitoring tests on one steel rail model in laboratory and on one real railway tack in outdoor were conducted respectively. In the model test, the working conditions of simply supported beam and continuous beam in the rail model under several concentrated loads were set to simulate different stress conditions of the real rail, respectively. In order to evaluate the monitoring accuracy, one distributed optical fiber sensor and one fiber Bragg grating (FBG) sensor were installed on the lower surface of the rail model, the strain measured by FBG sensor and the strain calculated from FEA were taken as measurement references. The model test results show that the strain measured by distributed optical fiber sensor has a good agreement with those measured by FBG sensor and FEA. In the outdoor test, the real track suffered from displacement and temperature loads. The distributed optical fiber sensor installed on the rail can monitor the corresponding strain and temperature with a good accuracy.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.229.1-229.1
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• 2014

Tactile sensors have widely been researched in the areas of electronics, robotic system and medical tools for extending to the form of bio inspired devices that generate feeling of touch mimicking those of humans. Recent efforts in adapting the tactile sensor have included the use of novel materials with both scalability and high sensitivity [1]. Graphene, a 2-D allotrope of carbon, is a prospective candidate for sensor technology, having strong mechanical properties [2] and flexibility, including recovery from mechanical stress. In addition, its truly 2-D nature allows the formation of continuous films that are intrinsically useful for realizing sensing functions. However, very few investigations have been carrier out to investigate sensing characteristics as a device form with the graphene subjected to strain/stress and pressure effects. In this study, we present a sensor of vertical forces based on single-layer graphene, with a working range that corresponds to the pressure of a gentle touch that can be perceived by humans. In spite of the low gauge factor that arises from the intrinsic electromechanical character of single-layer graphene, we achieve a resistance variation of about 30% in response to an applied vertical pressure of 5 kPa by introducing a pressure-amplifying structure in the sensor. In addition, we demonstrate a method to enhance the sensitivity of the sensor by applying resistive single-layer graphene.

• 대한전자공학회논문지SD
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• 제48권3호
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• pp.18-24
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• 2011

본 논문에서는 double boss 구조의 저압용 압력 센서의 다이아프램 브리지 모서리에 홈을 형성함으로서 압력센서의 내압특성을 향상시킬 수 있음을 확인하였다. 저압용 실리콘 압력센서에서는 일반적으로 boss구조가 널리 사용되고 있으나 칩에서의 제한된 다이아프램의 사이즈와 두께로 인하여 좋은 감도를 얻을 수는 없다. 특히, double boss구조는 다이아프램의 브리지 모서리 응력이 크게 작용함에 따라서 크랙이 생겨 다이아프램의 파괴가 진행되어 센서의 감도는 우수하지만 동작영역의 범위가 줄어들어 신뢰성에 문제가 있다는 단점을 가진다. 기존 double boss구조 압력센서 다이아프램 브리지에 모서리 홈의 길이를 $0.5{\sim}10{\mu}m$로 변화시키며 ANSYS 시뮬레이션을 시행하여 다이아프램 브리지 모서리와 브리지의 가장자리 그리고 압저항 소자가 위치하는 곳의 최대응력을 확인하였다. 그 결과 브리지 모서리의 길이가 6${\mu}m$이상인 경우, 브리지 모서리에서 발생하는 응력은 압저항 소자에 작용하는 응력보다 적다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.2061_2062
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• 2009

Within serviced period of time in transformer, thermal stress is the most influential parameter affecting the aging behavior of an insulation system. The thermal stress on the insulation system may occur from operation in a high temperature environment due to Joule's heat at winding coils. This paper describes a development of capacitive sensor and preventive diagnosis techniques for electrical insulating oil, widely used for power and distribution transformer. To survey the dielectric properties of the virgin and used mineral insulating oil, we utilized the highly precise measuring system of KRISS. And the results were used to determine the design factors of the sensor. To evaluate diagnosis by the sensor, we performed accelerated aging test about insulating oils. The condition of aged specimens were investigated by measurements of relative permittivity i.e. capacitance change by capacitive sensor.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 춘계학술대회 논문집
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• pp.588-595
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• 2014

In this paper, analysis of the vibration Characteristic for the Mine Detectable Test Platform is described. The test platform system is the multi-sensor mine detectable vehicle. This multi-sensor mine detectable unit is more efficient detection performance than other conventional methods. The test platform system has five subsystems, the UWB(Ultra Wide Band) sensor scanner, the MD(Metal Detector) sensor scanner, the neutron sensor scanner, and the detectable vehicle. We perform the vibration tests for the test platform and analyze the vibration characteristic, such as the max displacement, the max deformation and the max Von-Misses Stress.

• 한국소음진동공학회논문집
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• 제24권12호
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• pp.927-934
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• 2014

In this paper, analysis of the vibration characteristic for the mine detectable test platform is described. The test platform system is the multi-sensor mine detectable vehicle. This multi-sensor mine detectable unit is more efficient detection performance than other conventional methods. The test platform system has five subsystems, the UWB(ultra wide band) sensor scanner, the MD(metal detector) sensor scanner, the ND(neutron detector) sensor scanner, and the detectable vehicle. We perform the vibration tests for the test platform and analyze the vibration characteristic, such as the max displacement, the max deformation and the max Von-Misses stress.

• Journal of Mechanical Science and Technology
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• 제20권1호
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• pp.76-84
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• 2006

Arrayed ultrasonic sensors based on the piezoelectric thin film (lead-zirconate-titanate: Pb($Zr_{0.52}Ti_{0.48})O_{3}$) having composite membrane structure are fabricated. Different thermal and elastic characteristics of each layer generate the residual stress during the high temperature deposition processes, accomplished diaphragm is consequently bowing. We present the membrane deflection effects originated from the residual stress on the resonant frequencies of the sensor chips. The resonant frequencies ($f_r$) measured of each sensor structures are located in the range of $87.6{\sim}111\;kHz$, these are larger $30{\sim}40\;kHz$ than the resultant frequencies of FEM. The primary factors of $f_r$ deviations from the ideal FEM results are the membrane deflections, and the influence of stiffness variations are not so large on that. Membrane deflections have the effect of total thickness increase which sensitively change the $f_r$ to the positive direction. Stress generations of the membrane are also numerically predicted for considering the effect of stiffness variations on the $f_r$.