• 소음진동
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• 제7권1호
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• pp.61-69
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• 1997

Despite of the development in the finite element method, it is difficult to get the finite element model describing the dynamic characteristics of the complex structure exactly. Therefore a number of different methods have been developed in order to update the finite element model of a structure using vibration test data. This paper outlines the basic formulation for the frequency response function based updating method. One important advantage of this method is that the intermediate step of performing an eigensolution extraction is unnecessary. Using simulated experimental data, studies are conducted in the case of 10 DOF discrete system. The solution of noisy and incomplete experimental data is discussed. True measured frequency response function data are used for updating the finite element model of a beam and a plate. Its applicability to the joint identification is also considered.

• 한국소음진동공학회논문집
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• 제11권5호
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• pp.123-130
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• 2001

The purpose of this paper is to reduce the level of idling vibration on a steering wheel. In some cases, vibration on steering wheel is amplified due to the resonance between the first natural frequency of T-beam and engine idling speed. Using SDM(structural dynamic modification) technique, T-beam is redesigned to reduce its vibration. This paper used FRF(frequency response function) synthesis technique which is entirely dependent on experiment. But this method requires lots of test efforts to enhance its reliability of design. While combining this method with an analytic method. the experimental burden, the major drawback of FRP synthesis method, can be considerably relieved. Using ana1ytic sensitivity analysis, some effective modification regions are preliminarily chosen as candidate Positions where SDM can be applied to modify T-beam\`s dynamic characteristics.

• Journal of Mechanical Science and Technology
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• 제19권10호
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• pp.1891-1901
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• 2005

Recently the authors tried to find damage position only using measured frequency response functions. According to their work, it seems that the algorithm is very practical since it needs only measured frequency responses while other methods require exact analytic model. But when applying the method to a real structure, it requires lots of experiment. The authors, in this time, propose a method to reduce its experimental load by detecting damage within a substructure. This method searches damages not within an entire structure but within substructures. In addition, damage severity was treated in this paper since it is worthy to know damage severity. Optimization technique is used to estimate damage level using measured responses and damage model. Two test examples, a plate and a jointed structure, are chosen to verify the suggesting method.

• 전자공학회논문지SC
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• 제49권2호
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• pp.38-45
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• 2012

선천성 난청으로 태어난 아이를 조기에 진단하여 가능한 빨리 적절한 치료를 해줌으로써 치료 효과를 극대화하고, 이후에 발생되는 사회적 비용을 최소화할 수 있기 때문에 신생아로부터 난청 이상 유무를 객관적으로 판별하는 검사 장비가 필요하다. 대표적인 것으로 청성뇌간반응(auditory brainstem response, ABR) 검사가 있으나 클릭음(click sound)에 대한 반응으로 주파수 특이성이 없고 고주파수 대역에 대한 청력을 주로 반영하는 단점이 있다. 청성지속반응(auditory steady-state response, ASSR) 검사는 주파수 특이도는 좋으나 오진의 가능성이 조금 높다. 이러한 단점을 보완하여 청성뇌간반응 검사와 청성지속반응 검사를 하나의 시스템에서 측정하고, Fsp와 F-test 분석을 통하여 객관적 지표를 보여주는 시스템을 제안하였다. 하드웨어 구성요소를 최소화하고 소프트웨어 역할을 강화하여 추후 하드웨어 수정 없이 소프트웨어의 수정만으로 다양한 검사가 가능하도록 설계하였다. 제안한 시스템의 객관적 평가 기능은 정상인 10명을 대상으로 한 실험을 통하여 검증하였다.

• 대한기계학회논문집A
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• 제24권8호
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• pp.1978-1990
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• 2000

In this study, the free vibrations of the cantilever plate, which is one of the most frequently used elements in various machine structures, are analyzed and further the results are utilized to develop the methodology to predict and control the natural frequencies for designing stabilized systems. The proposed method has three major steps. The first step is the frequency response test to investigate the natural frequencies of some plates, then the database is constituted from experiments and the FEM, and finally the natural frequencies are predicted using the database to be cross-checked by the identification test. The result of this study will help design many different stable structures without any complicated calculations.

• 한국소음진동공학회논문집
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• 제15권2호
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• pp.219-224
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• 2005

Vibration response of the tower structure of a 750kW wind turbine (W/T) generator is investigated by measurement and analysis. Acceleration response of the W/T tower under various operation condition is monitored in real time by the vibration monitoring system using LabVIEW. Resonance state of the tower structure is diagnosed in the operating speed range. Resonance frequency range of the test model is investigated with the wind speed data of the test site. To predict the tower resonance frequency, tower is modeled as an equivalent beam with a lumped mass and Rayleigh energy method is applied. Calculated tower bending frequency is in good agreement with the measured value and the result shows that the simplified model can be used in the design stage of the W/T tower.

• 한국기계가공학회지
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• 제19권9호
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• pp.71-77
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• 2020

In recent years, as a consequence of the technological advancements in the automobile industry and changes in consumer demands, the reduction of noise inside vehicles rather than vehicle performance has increasingly become an important factor of interest. To date, most studies have focused on noise and vibration reduction techniques for the engine and drive system of vehicles. In this research, a comparative analysis for reducing the effect of vehicle seatbelts on the transient response is performed using the test of vehicle conditions and transient response analysis in accordance with seatbelt conditions. After the sensitivity analysis, the specifications for improvement were designed based on the transient response analysis. It was confirmed that the transient response characteristics were improved by the transient response analysis and vehicle conditions test. Through computer-aided engineering, the transient response characteristics of seatbelts were checked with less cost and time.

• 대한건축학회논문집:구조계
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• 제35권11호
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• pp.129-136
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• 2019

Non-structural elements are vulnerable to earthquake ground motion. In this study, an experimental study for the electrical non-structural element was performed using tri-axial shaking table tests. A 100kVA UPS(Uninterruptible Power Supply system) was used as the test specimen. The test specimen was anchored to the concrete slab using the conventional installation detail. The input acceleration were generated in accordance with ICC-ES AC156 code. Scale factors of the input acceleration with respect to the required response spectrum defined in ICC-ES AC156 were from 25% to 600%. Based on the test results, damage and dynamic characteristics of UPS were evaluated and analyzed including natural frequency, damping ratio, acceleration time history response, dynamic amplification factor and relative displacement.

• 한국자동차공학회논문집
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• 제10권4호
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• pp.122-128
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• 2002

In this paper dynamic responses of an engine, which is supported by hydraulic mount, to throttle tip-in/Tip out are analyzed. Because the hydraulic mounts have non-linearity that the characteristics of stiffness and damping vary with frequencies, it is difficult to analyze the dynamic behavior of an engine using general integral algorithms. Convolution integral and relationship between unit impulse response functions and frequency response functions are therefore used to simulate the transient behaviors of an engine indirectly. In time domain, impulse response functions are calculated by two-side discrete inverse courier transform of frequency response function achieved by laplace transform of equations of motion. Considering the fact that the shapes of behavior of an engine simulated by the proposed method are in good agreement with test results, it is confirmed that the proposed method is very effective for the analysis of transient response to throttle tip-in/out of an engine with hydraulic mounts.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집B
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• pp.540-545
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• 2001

In this paper dynamic responses of an engine, which is supported by hydraulic mount, to throttle tip-in/tip out are analyzed. Because the hydraulic mounts have non-linearity which the characteristics of stiffness and damping vary with frequencies, it is difficult to analyze the dynamic behavior of an engine using general integral algorithms. Convolution integrals and relationships between unit impulse response functions and frequency response functions are therefore used to simulate the transient behavior of an engine indirectly. In time domain, impulse response functions are calculated by two-side discrete inverse Fourier transform of frequency response function achieved by Laplace transform of equations of motion. Considering the fact that the shapes of behavior of an engine simulated by the proposed method are in good agreement with test results, it is confirmed that the proposed method is very effective for the analysis of transient response to throttle tip-in/out of an engine with hydraulic mounts.