• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 춘계학술대회논문집
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• pp.789-794
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• 2008

The damage identification in a flexible system requires modal informations which is represented by FRF(Frequency response function) or modal parameters. In this paper, energy isoclines are introduced to access the prediction of fatigue damage on a flexible component exposed mainly to the exciting source rather than external forces. After deriving the concerned function, energy isoclines, from the investigation of the relationship between energy and damage, its practical application is explained by the simple uni-axial excitation test for the notched round bar.

• 한국소음진동공학회논문집
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• 제17권1호
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• pp.80-87
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• 2007

In this paper, a method for identifying the location and extent of a damage in a structure using residual forces was presented. Element stiffness matrix reduction parameters in a finite element model were used to describe the damaged structure mathematically. The element stiffness matrix reduction parameters were determined by minimizing a global error derived from dynamic residual vectors, which were obtained by introducing a simulated experimental data into the eigenvalue problem. Genetic algorithm was used to get the solution set of element stiffness reduction parameters. The proposed scheme was verified using Euler-Bernoulli beam. The results were presented in the form of tables and charts.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 II
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• pp.1182-1188
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• 2001

The objective of this paper is to show the effectiveness of the wavelet transform by means of its capability to estimate the Lipschitz exponent. In particular, we show that the magnitude of the Lipschitz exponent can be used as a useful tool estimating the damage extent. An effective method based on the Lipschitz exponent is proposed and we present the results investigated both numerically and experimentally. The continuous wavelet transform by a Mexican hat wavelet having two vanishing moments is utilized for the estimation of the Lipschitz exponent.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.612-615
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• 2005

This studies presented truss frame which use aluminum beam by damage model. Truss frame which each joint part is contracted by bolt contracted conclusion of each bolt by 3.0 N/m. And measured impedance change that appear making bolt 0.5 N/m on damage condition 8 times. Compares impedance change of 5 segments that was set by measurement area and displayed result. To measure torque change of bolt, other damage model did not apply.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1998년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Spring 1998
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• pp.131-138
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• 1998

Structural damage is used to be modeled through reductions in the stiffness of structural elements for the purpose of damage estimation of structural system. In this study, the concept of joint damage is employed for more realistic damage assessment of a steel structure. The joint damage is estimated damage based on the mode shape informations using neural networks. The beam-to-column connection in a steel frame structure is represented by a rotational spring at the fixed end of a beam element. The severity of joint damage is defined as the reduction ratio of the connection stiffness with respect to the value of the intact joint. The concept of the substructural identification is used for the localized damage assessment in a large structure. The feasibility of the proposed method is examined using an example with simulated data. It has been found that the joint damages can be reasonably estimated for the case with the measurements of the mode vectors subjected to noise.

• Smart Structures and Systems
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• 제21권2호
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• pp.235-248
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• 2018

An efficient method utilizing the multi-stage improved differential evolution algorithm (MSIDEA) as an optimization solver is presented here to detect the multiple-damage of structural systems. Natural frequency changes of a structure are considered as a criterion for damage occurrence. The structural damage detection problem is first transmuted into a standard optimization problem dealing with continuous variables, and then the MSIDEA is utilized to solve the optimization problem for finding the site and severity of structural damage. In order to assess the performance of the proposed method for damage identification, an experimental study and two numerical examples with considering measurement noise are considered. All the results demonstrate the effectiveness of the proposed method for accurately determining the site and severity of multiple-damage. Also, the performance of the MSIDEA for damage detection compared to the standard differential evolution algorithm (DEA) is confirmed by test examples.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1998년도 춘계학술대회논문집; 용평리조트 타워콘도, 21-22 May 1998
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• pp.377-380
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• 1998

Basting vibration and air blast were measured by particle velocity and overpressure as well as environmental unit, dB(V) and dB(A). Variables for vibration and noise show good relationship and proportional equations are suggested. But there are some variations, and it means that predictions by design variables are not valid for human damage estimation or limit application of regulations.

• 한국소음진동공학회논문집
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• 제14권11호
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• pp.1166-1175
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• 2004

People in the advanced society have deep interest in such environmental problems as noise, air quality, water pollution, etc. This paper submits the result of the research on the noise In the surroundings of the butane can explosion location. First, the noise level measured in a residential area, 245 meters' away from the butane can explosion location, was 59.3 dB. Also, the noise level measured in the IGUP (International Graduate University of Peace), 300 meters' away from the explosion site, was 52.5 dB. Second, the above noise levels are lower than the level specified In the Environmental Standard (65 dB), which represented that the experiment was safe. Third, the noise level in a place away from the butane can explosion location varied in accordance with the direction of the wind. Consequently, the noise in all locations (the places where damage to people is expected) surrounding the experimental butane can explosion location was measured to identify the effect of the wind irection.

• Earthquakes and Structures
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• 제15권5호
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• pp.463-471
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• 2018

The virtual forces of the original local flexibility method are restricted to inducing stress on the local parts of a structure. To circumvent this restriction, we developed a pseudo local flexibility (PLFM) method that can successfully detect damage to hyperstatic beam structures using fewer modes. For this study, we further developed the PLFM so that it could detect damage in plate structures. We also devised the theoretical background for the PLFM with non-local virtual forces for plate structures, and both the lateral and rotary degree of freedom (DOF) measurements were considered separately. This study investigates the effects of the number of modes, the actual location that sustained damage, multiple damage locations, and noise in modal parameters for the damage detection results obtained from damaged numerical plates. The results revealed that the PLFM can be used for damage detection, localization, and quantification for plate structures, regardless of the use of the lateral DOF and/or rotary DOF.

• 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.