• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집B
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• pp.341-348
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• 2001

In this study, a method is presented to find out a relationship between modes of a substructure and those of the system structure. Superelement analysis is performed for a full vehicle system, where the bus is partitioned by six parts. In this study, Modal Assurance Criteria(MAC) which is to represent the correlation between two mode shapes is used to investigate the contribution factor of each substructure for the full system. The proposed participation factor can be used for design of substructures to meet the design target of the total structural system.

• 한국지진공학회논문집
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• 제6권4호
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• pp.15-22
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• 2002

이 연구는 원자력발전소 구조물의 확률론적 내진성능을 평가하는 수단으로 이용되고 있는 지진취약도분석 기법에 대하여 소개하고, 지진취약도분석에 입력자료로 제공되는 기본변수의 특성에 대하여 논의하였다. 특히, 지진취약도 분석결과에 지대한 영향을 미칠 수 있는 입력변수의 하나인 응답스펙트럼형태계수의 정의 방법을 개선하였다. 새로운 응답스펙트럼형태계수는 구조물의 고유진동모드별 기여도가 전체 구조응답에 미치는 영향을 고려할 수 있도록 모드별 기여도를 이용하여 표현하였다. 대표적인 원자력발전소 구조물을 대상으로 예제분석을 수행하고, 제안된 응답스펙트럼형태계수의 유용성 및 적용성을 검증하였다. 특히, 이 논문의 방법은 복합모드감쇠특성을 갖는 구조물의 경우에도 효과적으로 적용될 수 있음을 확인하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 추계학술대회논문집
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• pp.604-605
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• 2008

Modal participation factor (MPF) is a widely used in a mode-coupling squeal noise problem for finding the most sensitive component over a complex brake system in a vehicle using eigenvectors of sub-components. This methodology requires the problematic total response of system by the unstable squeal noise at a specific frequency as well as eigenvectors of each component belonging to brake system. In this paper, a unit-force response analysis is performed for intact total system to obtain eigenvectors of each component and then such data is directly used for the contribution analysis of a squeal noise problem. Since the eigenvectors of each component induced from virtual unit-excitation is most reliable owing to the intact boundary condition, it can be expected that the corresponding contribution analysis with MPF also provides a trustworthy result.

• Smart Structures and Systems
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• 제17권3호
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• pp.413-429
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• 2016

The recent research on proper orthogonal decomposition (POD) has revealed the linkage between proper orthogonal modes and linear normal modes. This paper presents an investigation into the modal identifiability of an instrumented cable-stayed bridge using an adapted POD technique with a band-pass filtering scheme. The band-pass POD method is applied to the datasets available for this benchmark study, aiming to identify the vibration modes of the bridge and find out the so-called deficient modes which are unidentifiable under normal excitation conditions. It turns out that the second mode of the bridge cannot be stably identified under weak wind conditions and is therefore regarded as a deficient mode. To judge if the deficient mode is due to its low contribution to the structural response under weak wind conditions, modal coordinates are derived for different modes by the band-pass POD technique and an energy participation factor is defined to evaluate the energy participation of each vibration mode under different wind excitation conditions. From the non-blind datasets, it is found that the vibration modes can be reliably identified only when the energy participation factor exceeds a certain threshold value. With the identified threshold value, modal identifiability in use of the blind datasets from the same structure is examined.

• 대한기계학회논문집
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• 제16권1호
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• pp.13-21
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• 1992

본 연구에서는 구조-음향모드 연성계수를 이용하여 심각한 소음문제가 발생하 는 경우의 효과적인 소음저감 방안을 제시하고, 제작된 차실모델에 대한 소음저감 시 뮬레이션을 수행한 후 그 결과를 실험치와 비교함으로써 수립된 소음저감 방안의 신뢰 도와 유용성을 확인하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 춘계학술대회 논문집
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• pp.835-841
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• 2013

Modern solid-state gyroscopes (HRG) with hemispherical resonators from high-purity quartz glass and special surface superfinishing and ultrathin gold coating become the best instruments for precise-grade inertial reference units (IRU) targeting long-term space missions. Designing of these sensors could be a notable contribution into development of Korea as a space nation. In participial, 40mm diameter thin-shell resonator from high-purity fused quartz, fabricated as a single-piece with its supporting stem has been designed, machined, etched, tuned, tested, and delivered by STM Co. (ATS of Ukraine) several years ago; an extremely-high Q-factor (upto 10~20 millions) has been shown. Understanding of the best way how to match such a unique sensor with inner glass assembly of the gyro means how to use the high potential in a maximal extent; and this has become the urgent task. Inner quartz glass assembly has a very thin indium (In) layer soldered the resonator and its silica base (case), but effects of internal resonances between operational modal pair of the shell-cup and its side (parasitic) modes can notable degrade the potential of the sensor as a whole, instead of so low level of resonator's intrinsic losses. Unfortunately, there are special combinations of dimensions of the parts (so-called, "resonant sizes"), when intensive losses of energy occurs. The authors proposed to use the length of stem's fixture as an additional design parameter to avoid such cases. So-called, a cyclic scheme of finite element method (FEM) and ANSYS software were employed to estimate different combinations of gyro assembly parameters. This variant has no mismatches of numerical origin due to FEM's discrete mesh. The optimum length and dangerous "resonant lengths" have been found. The special attention has been paid to analyses of 3D effects in a cup-stem transient zone, including determination of a difference between the positions of geometrical Pole of the resonant hemisphere and of its "dynamical Pole", i.e., its real zone of oscillation node. Boundary effects between the shell (cup) and 3D short "beams" (inner and outer stems) have been ranged. The results of the numerical experiments have been compared with the classic model of a quasi-hemispherical shell band with inextensional midsurface, and the solution using Rayleigh's functions of the $1^{st}$ and $2^{nd}$ kinds. To guarantee the truth of the recommended sizes to a designer of the real device, the analytical and FEM results have been compared with experimental data for a party of real resonators. The consistency of the results obtained by different means has been shown with errors less than 5%. The results notably differ from the data published earlier by different researchers.