• Structural Engineering and Mechanics
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• v.31 no.3
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• pp.277-296
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• 2009

The paper investigates the dynamic behaviour of stiffened panels. The coupled differential equations for eccentric stiffening configuration are first derived. Then a semi-analytical procedure for dynamic analysis of stiffened panels is presented. Unlike finite element or finite strip methods, where the plate is discretized into a set of elements or strips, the plate in this procedure is treated as a single element. The potential energy of the structure is first expressed in terms generalized functions that describe the longitudinal and transverse displacement profiles. The resulting non-linear strain energy functions are then transformed into unconstrained optimization problem in which mathematical programming techniques are employed to determine the magnitude of the lowest natural frequency and the associated mode shape for pre-selected plate/stiffener geometric parameters. The described procedure is verified with other numerical methods for several stiffened panels. Results are then presented showing the variation of the natural frequency with plate/stiffener geometric parameters for various stiffening configurations.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.1
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• pp.87-93
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• 2001

이 논문은 사하중에 의한 정적 처짐을 갖는 변단면 보의 자유진동에 관한 연구이다. 사하중이 작용하는 변단면 보의 자유진동을 지배하는 상미분방정식을 유도하고 이를 수치해석하여 최 저차 3개 모드의 고유진동수 및 진동형을 산출하였다. 수치해석 예제에서는 선형 변단면과 등분포 사하중을 채택하였다. 지점조건으로는 회전-회전, 회전-고정, 고정-고정 보를 채택하였다. 수치해석의 결과로 하중강도, 세장비 및 단면비가 고유진동수에 미치는 영향을 분석하였다. 사하중의 영향을 고려한 경우와 고려하지 않은 경우의 진동형을 서로 비교하였다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.459-466
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• 2006

The objective of this study is to improve the accuracy of damage detection using natural frequency and modal strain energy. The following approaches are used to achieve the goal. First, modal strain energy is introduced and newly GA-based damage detection technique using natural frequency and modal strain energy is proposed. Next, to verify efficiency of the proposed technique, damage scenarios for free-free beams are designed and the vibration modal tests as damage cases are conducted. Finally, feasibility of proposed technique is verified in comparison with a GA-based damage detection technique using natural frequency and mode shape.

• Journal of KSNVE
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• v.9 no.1
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• pp.131-140
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• 1999

A method to reconstruct the sound field around a Korean bell is developed. The sound radiation problem is formulated based on the boundary element method by using the algorithm of the acoustical holography. Sound pressures at the hologram surface are measured and used as input data for the analysis program that was developed in this study. An error minimization scheme is presented to overcome difficulties that arise in the backward reconstruction of the BEM-based acoustical holography In the model fictitious source surfaces were also introduced to reduce the complexity stemmed from the source shape. The sound field associated with the (4.0) vibrational mode of the Korean bell was visualized and verified experimentally.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.102-108
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• 2000

Due to the rapid increase of long-distance transportation, particular attentions have been paid to truck tires, especially to their dynamic characteristics. In this research, experimental modal analysis on two kinds of light-truck tires, i.e., radial tire and bias tire, are performed by using GRFP(global rational fraction polynomial) method to investigate differences of the dynamic behavior of the two tires. The test results have shown that the modal frequencies of bias tire are much higher than their corresponding values of radial tire with a similar mode shape, which is in accordance with the fact that the radial rigidity of bias tire is higher than that of radial tire. And most of the modal decay rates of bias tire are larger than those of radial tire within the scope of this experiment. In the frequency domain range of test, the bias tire has extra modes, which do not occur in the radial tire. This difference is based on the fact that the circumferential rigidity of the bias tire is quite low whereas that of radial tire is so high that the frequencies of the corresponding modes are out of the frequency range of test.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.2
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• pp.66-72
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• 2012

Ultrasonic metal welder is consisted of power supply, transducer, booster, and horn. Precise designing is required since each part's shape, length and mass can affect driving frequency and vibration mode. This paper gives a description of an experimental study of the ultrasonic welding of metals. A horn suitable for 40,000Hz was attached to the ultrasonic metal welder in order to weld Cu sheet. The Cu sheet welding was done with different amplitude, pressure and welding time, and its maximum tension was measured. Maximum tension of 177.99N was obtained when the pressure was 2.5bar, amplitude was 80%, and welding time was 0.34sec. Therefore, excessive welding condition negatively influences maximum tension measurement result.

• Computational Structural Engineering
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• v.11 no.3
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• pp.155-164
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• 1998

이 논문은 변단면을 고려한 수평 곡선보의 자유진동에 관한 연구이다. 진동시 곡선보 요소에 작용하는 합응력과 관성력의 동적평형방정식을 이용하여 변단면 원호형 수평 곡선보의 자유진동을 지배하는 상미분방정식을 유도하였다. 이 미분방정식을 원형 단면을 갖는 선형변변단면에 적용하여 고유진동수, 진동형 및 합응력을 산출하였다. 수치 해석예에서는 양단고정 및 양단회전 곡선보를 채택하였으며, 수치해석 결과로서 고유진동수와 단면비, 세장비 및 중심각 사이의 관계를 그림에 나타내었다. 또한 실험실 규모의 실험을 통하여 본 연구결과의 타당성을 보였다.

• Magazine of the Korean Society of Agricultural Engineers
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• v.38 no.6
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• pp.42-50
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• 1996

이 논문은 step기둥의 자유진동 및 좌굴하중에 관한 연구이다. 축하중을 받는 변단면 기둥의 자유진동을 지배하는 편미분방정식을 이용하여 축하중을 받는 step기둥의 자유진동을 지배하는 상미분방정식을 유도하였다. 또한 이 자유진동을 지배하는 미분방정식을 이용하여 step기둥의 좌굴하중을 지배하는 상미분방정식을 유도하였다. 유도된 미분방정식들을 Heun방법과 Regula-Falsi방법을 이용하여 고유진동수 및 좌굴하중을 산출할 수 있는 수치해석방법을 개발하였다. 실제 수치해석 예에서는 2개의 step구간을 갖는 회전-회전, 회전-고정, 고정-고정 기둥에 대한 무차원 고유진동수화 무차원변수들과의 관계 및 무차원 좌굴하중과 무차원 변수들과의 관계를 그림에 나타내었다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.33-36
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• 1998

This paper is a study on a linear ultrasonic motor with a first longitudinal$(L_1)$ and fourth bending $(B_4)$ double-mode rectangular plate. The stator vibrator is composed of an elastic material plate and of a piezo-ceramic element having a motion by electrical excitation. Each strain vector differs by $90^{\circ}$ generate travelling wave with the elliptical displacement motion of a point on the surface. To magnify displacement of longitudinal direction in elliptical displacement motion, the motor has a mechanism of the.displacement enlargement. In this paper, the vibration shape of the stator is simulated using the finite element method. A detailed model considered of the piezoelectric effect and of the exact geometry of the stator is used to calculate the displacement. The position of displacement mechanism is decided by the maximum displacement.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.9 no.6
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• pp.140-151
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• 2000

Springs for vehicle suspension control the vibration of a car and influence on the ridability, safety, and life of a car. in the paper, the computer aided design program has been developed, which design the leaf spring shape from the given specifications using basic theory and the expert\`s knowledge, and the design results are checked by the analysis theory in order to increase the accuracy, and feed back to the design input. For the purpose of easy use, this program consists of pull-down menu and interactive input mode. To prove the effectiveness of this program, two springs, of which one is symmetric, other asymmetric, are designed and analyzed, and the outputs are compared to the experiments. Considering the tolerance of the given specifications, the results are good.