• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.311-314
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• 2007

The experimental method of measuring dynamic properties of structures was presented. The method is based on the flexural wave propagation characteristics. Using the method, change in structural dynamic properties due to damage is measured. The crack has much more significant impact on the strain energy than the inertial effects. From this, the sensitivity of the dynamic stiffness on the crack location is estimated by calculating the strain energy. When the wave propagates, the strain and kinetic energies shows cyclic changed over space. The crack that occurred at locations where the wave energy is in the form of the potential energy affected most significantly the wave propagation characteristics. The effects of crack location on the wave propagation were used to determine the crack location.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.739-742
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• 2014

In the process of MLCC manufacturing, MLCC stacking process is the key process of making high quality MLCC. Since MLCC is small components, the entire process of MLCC stacking process is minute and sensitive to micro errors. To prevent micro error, we suggest condition-based monitoring which quantifies error based on feature extraction and quantifying error method. As results, it has been shown that the suggested algorithm has effectiveness of condition based monitoring of MLCC stacker.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.619-624
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• 2004

In this research, the structural health monitoring method using wavelet packet analysis and artificial neural network (ANN) is developed. Wavelet packet Transform (WPT) is applied to the response acceleration of a 3 element-cantilever beam which is subjected to impulse load and Gaussian random load to decompose the response signal, then the energy of each component is calculated. The first ten largest components in magnitude among the decomposed components are selected as input to an ANN to identify the damage location and severity. This method successfully predicted the amount of damage in the structure when the structure is subjected to impulse load. However, when the beam is subjected to Gaussian random load which can be considered as ambient vibration it did not yield satisfactory results. This method is applicable to structures such as machinery gears that are subjected to repetitive loads.

• Proceedings of the Korea Information Processing Society Conference
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• 2014.11a
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• pp.33-36
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• 2014

철도로 인한 소음 문제는 최근 국민의 정온한 환경에 대한 권리의식 증대와 삶의 질에 대한 높은 관심으로 철도 소음에 대한 민원이 급증하여 지역 갈등을 초래하고 막대한 사회적 비용 부담으로 철도 산업을 저해하는 요소이다. 이에 따라, 철로 부근의 진동 및 소음에 대한 모니터링 시스템의 필요성이 증대되고 있으나, 레일의 조도상태 및 방진재 사양 등 철도진동소음에 영향을 주는 인자를 충분히 포함하지 못하고 있으며, 측정 및 분석 데이터의 체계적인 관리, 축적 구조를 갖지 못하는 문제가 있다. 또한, 연구기관의 인위적인 데이터 양식의 사용으로 실용적이고 개방적인 구조를 갖추지 못해 실제 엔지니어링 현장에서 활용하기 어렵다. 이에, 본 논문에서는 실제 엔지니어들이 현장에서 취득하는 정보를 체계적이고 지속가능한 형태로 데이터베이스화 하는 일체의 시스템 구축에 대해 논한다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.261-262
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• 2013

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.880-885
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• 2007

Diesel engines have been widely used in ships and power plants because of its higher thermal efficiency, mobility and durability compared to other prime movers. Though these merits, diesel engine including main components are sometimes vibrated due to higher combustion pressure in cylinders. Especially torsional, axial and structural vibrations in propulsion shafting may be severely manifested by the malfunction of torsional and axial dampers and misfiring and unbalanced load in cylinder. The structural vibration of main body and turbocharger core hole are also occurred by the loosen top bracing and excess wear-out or failure of turbocharger's bearings. The marine diesel engine should be safely designed from these vibrations. This paper introduces experimental methods to develop the prototype of integrated vibration monitoring system for marine diesel engine.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.2 s.119
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• pp.114-120
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• 2007

Vibration performance of a 6 kW stand-alone wind turbine(W/T) generator is investigated under the wind environment of Daegwanryung mountain area. In the W/T, wind condition, power performance and structural stability are correlated each other An integrated monitoring system which consists of accelerometers, anemometers, power meters and auxiliary sensors for atmospheric data are constructed to measure the required data simultaneously. Based upon the data acquired over a long period of time, vibration performance of the W/T structure is estimated with annual wind data and generating power performance. Within the operating speed range, possibility of severe nitration is diagnosed. Vibration sources are identified and countermeasures are proposed. The goal of the study is to offer the basic information on W/T vibration performance at the design stage of a small stand alone W/T structure.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.11 no.5
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• pp.108-122
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• 2001

As bridge design is advancing toward the performance-based design. it becomes increasingly important to monitor and re-evaluate the long-term structural performance of bridges. Such information is essential in developing performance criteria for design. In this research. sensor systems for long-term structural performance monitoring have been installed on two highway bridges. Pre1iminary vibration measurement and data analysis have been performed on these instrumented bridges. On one bridge, ambient vibration data have been collected. based on which natural frequencies and mode shapes have been extracted using various methods and compared with those obtained by the preliminary finite element analysis. On the other bridge, braking and bumping vibration tests have been carried out using a water truck In addition to ambient vibration tests. Natural frequencies and mode shapes have been derived and the results by the breaking and bumping vibration tests have been compared. For the development of a three dimensional baseline finite element model, the new methodology using a neural network is proposed. The proposed one have been verified and applied to develop the baseline model of the bridge.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.2
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• pp.155-161
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• 2009

Engine builders have separately developed and applied torsional, axial and structural vibration monitoring system on most marine engines. These systems displayed their results for engine or ship operation engineers and were not regularly stored at the hardware of computer. So, the history and trend of various engine and hull vibrations were not supported for preventive maintenance and to protect the failure of these activity or function. The integrated vibration or stress monitoring system(EVAMOS : engine vibration analysis and monitoring system) in marine diesel engine, its accessories and hull structure have been developed by the dynamics laboratory of Mokpo Maritime University during last 3 years. This paper introduces the design conception and ability of commercial software EVAMOS with field data on several actual tests.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.241-245
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• 2005

This study introduces the wind turbine (W/T) noise evaluation procedure required in the international standard (IEC 61400-11) and monitoring system for the evaluation. Noise emission characteristics of a 750kW W/T generator is investigated. Test and evaluation are performed on J48 W/T model which is under operation in Daekwanryung Wind Test Site. With the noise signal, meteorological data and W/T operational data are monitored in real time by the integrated monitoring system using LabVIEW. From the measured noise data, acoustic power level and tonality of the W/T are estimated under the wind speeds required by the international standard.