• The Journal of Engineering Geology
• /
• v.26 no.4
• /
• pp.583-591
• /
• 2016

Vibrating wire (VW) strain gauges are widely used for the evaluation of pipeline safety in extreme cold region. The development of VW strain gauges for the low temperature environment is necessary because of the high cost of gauges sold in developed countries. Thermistors embedded in the regular VW strain gauges and PT 100 sensors embedded in the gauges specially manufactured for this study have gone through credibility tests for temperature measurements. The use of PT 100 is recommended at low temperature environments because thermistors have low credibility at temperatures below $-15^{\circ}C$. Strain measurements using regular VW strain gauges also show low accuracies as temperature goes down. VW strain gauges manufactured using inconel give high credibility of strain measurements at low temperatures. More reliable VW strain gauges for the low temperature environment will be developed in the near future.

• The Journal of Engineering Geology
• /
• v.18 no.2
• /
• pp.153-158
• /
• 2008

Vibrating-wire strain gauges are widely used for the tunnel instrumentation because of the long-term stability at humid environments. Domestic strain gauges are mainly used in Korea due to the high cost of the foreign strain gauges. The credibility of the domestic strain gauges is not properly proven even though strain gauges produced by many different companies are available in the markets. The purpose of this paper is to investigate the credibility of the 2.5" strain gauges by using a laboratory compression test.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2009.04a
• /
• pp.93-96
• /
• 2009

바퀴동력계는 차량에 지면으로부터 전달되는 힘과 모멘트를 측정하는 로드셀이다. 본 연구에서 개발한 바퀴동력계는 스트레인 게이지식 로드셀로써 이러한 로드셀을 설계하는데 있어서 몇가지 고려해야 하는 사항이 있다. 우선 스트레인 게이지를 부착하기 쉬운 구조가 되어야 하고 조립시의 오차를 줄이기 위하여 한 몸체로 제작되어야 한다. 이와 동시에 가장 중요하게 고려되어야 하는 인자로 감도를 위해 재료가 허용하는 응력내에서 되도록 큰 변형률이 발생해야 하고 상호 간섭 오차가 발생하지 말아야 한다. 본 연구에서는 수식을 이용하여 이론적으로 상호 간섭 오차를 0으로 만들 수 있었다. 또한 설계 변수 및 재료 물성치의 산포를 고려한 신뢰성 기반 최적설계 기법을 사용하였으며, 이를 통해 허용 응력하에서 최대의 변형률이 발생하는 바퀴동력계를 설계하였다.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.38 no.10
• /
• pp.1049-1056
• /
• 2014

Microelectronics components contain various materials with different coefficients of thermal expansion (CTE). Although a large amount of published data on the CTE of standard materials is available, it occasionally becomes necessary to measure this property for a specific actual material over a particular temperature range. A change in the temperature of a material causes a corresponding change in the output of the strain gage installed on the specimen because of not only the mechanical load but also the temperature change. In this paper, a detailed technique for CTE measurement based on these thermal characteristics of strain gages is proposed and its reliability is evaluated. A steel specimen, aluminum specimen, and copper specimen, whose CTE values are well known, were used in this evaluation. The proposed technique was successfully applied to the measurement of the CTE of a coreless package substrate composing of electronics packages.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 1999.10a
• /
• pp.21-21
• /
• 1999

파괴인성의 정량적 평가는 균열이 내재할 수 있는 구조물의 설계 및 사용중 건전성 확보를 위하여 필요하다. 파괴인성의 측정은 광탄성법, 코스틱법 및 모아레법 등에 의하여 주로 평가되고 있으나 고가의 장비가 필요하고 실험으로 구현하는데 어려움이 있기 때문에, 실험이 비교적 간단하고 신뢰성이 있는 스트레인 게이지법에 관한 연구가 최근에 이루어지고 있다. 본 연구는 항공기나 로켓의 추진기용 구조재로 사용되는 마레이징강과 티타늄 합금을 이용하여 파괴인성시험을 수행하였다. 균열선단의 변형률장은 Westergaard 응력 함수를 사용한 다중변수해로 표현하였고, 스트레인게이지에서 얻은 변형률을 대입하여 파괴인성치를 산출하였다. 스트레인게이지법에 의한 파괴인성치는 ASTM E399의 규정에 의한 실험결과들과 비교하여 그 유용성을 제시하였다.

• Composites Research
• /
• v.14 no.5
• /
• pp.12-19
• /
• 2001

In aircraft composite structures, structural defects such as matrix cracks, delaminations and fiber breakages are hard to detect if they are breaking out in operating condition. Therefore, to assure the structural integrity, it is desirable to perform the real-time health monitoring of the structures. In this study, a fiber optic sensor was applied to the composite beams to monitor failure and strain in real-time. To detect the failure signal and strain simultaneously, laser diode and ASE broadband source were applied in a single EFPI sensor using wavelength division multiplexer. Short time courier transform and wavelet transform were used to characterize the failure signal and to determine the moment of failure. And the strain measured by AEFPI was compared with the that of strain gage. From the result of the tensile test, strain measured by the AEFPI agreed with the value of electric strain gage and the failure detection system could detect the moment of failure with high sensitivity to recognize the onset of micro-crack failure signal.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.12
• /
• pp.918-923
• /
• 2018

The main function of a fuel tank is to store fuel. On the other hand, the structural soundness of the fuel tank is related directly to the survival of the crew in an emergency situation, such as an aircraft crash, and the relevant performance is demonstrated by a crash impact test. Because crash impact tests have a high risk of failure due to the high impact loads, various efforts have been made to minimize the possibility of trial and error in the actual test at the beginning of the design. Numerical analysis performed before the actual test is a part of such efforts. For the results of numerical analysis to be reflected in the design, however, the reliability of numerical analysis needs to be ensured. In this study, the results of numerical analysis and actual test data were compared to ensure the reliability of numerical analysis for the crash impact test of a rotorcraft fuel tank. For the numerical analysis of a crash impact test, LS-DYNA, crash analysis software, was used and the ALE (arbitrary Lagrangian Eulerian) technique was applied as the analysis method. To obtain actual test data, strain gages were installed on the metal fittings of the fuel tank and linked to the data acquisition equipment. The strain and stress of the fuel tank fitting were calculated by numerical analysis. The reliability of the numerical analysis was enhanced by assessing the error between the strain measurement of the upper fitting obtained from an actual fuel tank and the strain calculated from numerical analysis.

• Journal of the Korean Geosynthetics Society
• /
• v.14 no.4
• /
• pp.87-96
• /
• 2015

Geosynthetics are widely used in different ways such as reinforcement of structures in road, railway, harbor and dam engineering, drainage, separation and erosion prevention. They are especially applied to reinforced retaining wall and slope or ground reinforcement. Recently, geosynthetics reinforced pile supported (GRPS) embankment was developed to improve stability and construability of embankments in railway engineering. Extension strains are usually measured by strain gauges adhered to geosynthetics to evaluate the stability of geosynthetics. However, the measurements are influenced by manufacturing method and stiffness of geosynthetics and also adherence of strain gauge. In this study, wide-width tensile strength tests were performed on three types of geosynthetics including geogrid, woven geotextile and non-woven geotextile. During the test, strains of geosynthetics were measured by both video extensometer and strain gauges adhered to the geosynthetics and the measured results were compared. Results show that the measured results by strain gauges have high reliability in case of large stiffness geosythetics like geogrid and woven geotextile, whereas they have very low reliability for small stiffness geosythetics like non-woven geotextile.