• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11a
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• pp.167-172
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• 2001

구조최적화는 기계구조물의 동특성을 변경하기 위하여 필수적으로 수행되어야 할 요소이다. 어떠한 방법을 택하여 보다 효율적으로 수행할 것 인지가 엔지니어의 관심일 것이다. 구조최적화는 설계변수에 따라 치수최적화, 물성치최적화 형상최적화 등으로 나눌 수 있다. 형상 최적화는 구조물의 유한요소모델을 기본으로 경계의 형상이나 절점의 형상, 회전 등을 설계 변수로 삼는 것이다. 고유진동수를 높이거나 모드형상을 제어하기 위하여 평판에 보강재를 붙이는 경우가 있다. 이때 보강재의 위치나 치수 형상 등이 중요한 변수가 될 수 있다. 본 논문에서는 평판의 고유진동수를 극대화 하기위해 보 보강재를 붙이는 문제에서 보의 회전을 설계 변수로 삼아 최적설계를 수행 할 것이다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.311-318
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• 1998

In this paper, the power flow analysis(PFA) method is applied to the prediction of the vibrational energy density and intensity of coupled co-planar plates. To cover the energy transmission and reflection at the joint of the plates, the wave transmission approach is introduced with the assumption that all the incident waves are normal to the joint. By changing the frequency ranges and internal loss factors, we have obtained the PFA results, and compared them with the analytical exact solutions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.4
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• pp.376-381
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• 2010

The structural strength tests are usually performed to evaluate the structural strength and to verify the structural design and analysis of the vehicle structures. In this paper, the development of a compressed loading type apparatus to load distributed force over the surface of vehicle structure subjected to external loads was described. This apparatus is for structural materials which are easily to fail because of concentrated stresses. This apparatus can apply loads to specimens without any damage on the test specimen's surfaces by using flexible membrane and can be applicable to several kinds of surface profile of structures. The structural strength tests for the flat structure and curved structure with this apparatus were successfully performed, and the test results showed that this type of loading apparatus can be adequate to verify the structural integrity of the fragile structures.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.5
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• pp.401-407
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• 2017

This paper describes wavenumber filtering for damage detection using single-frequency standing wave excitation and laser scanning sensing. An embedded piezoelectric sensor generates ultrasonic standing waves, and the responses are measured using a laser Doppler vibrometer and mirror tilting device. After scanning, newly developed damage detection techniques based on wavenumber filtering are applied to the full standing wave field. To demonstrate the performance of the proposed techniques, several experiments were performed on composite plates with delamination and aluminum plates with corrosion damage. The results demonstrated that the developed techniques could be applied to various structures to localize the damage, with the potential to improve the damage detection capability at a high interrogation speed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.314-315
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• 2009

• Proceedings of the Korean Nuclear Society Conference
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• 2002.05a
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• pp.327-327
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• 2002

• Composites Research
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• v.18 no.6
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• pp.9-18
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• 2005

With the wide applications of fiber-reinforced composite material in aero-structures and mechanical parts, the design of composite joints have become a very important research area because the joints are often the weakest areas in composite structures. This paper presents an analytical study of the stress distributions in mechanically single-fastened and multi-fastened composite laminates. The finite element models which treat the pin and hole contact problem using a contact stress analysis are described. A dimensionless stress concentration factor is used to compare the stress distributions in composite laminates quantitatively In the case of single-pin loaded composite laminate, the effects of stacking sequence, the ratio of a hole diameter and the width of a laminate (W/D ratio), the ratio of hole diameter and distance from edge to hole (E/D ratio), friction coefficient and clamping force are considered. In the case of multi-pin loaded composite laminate, the influence of the number of pins, pitch distance, number of rows, row spacing and hole pattern are considered. The results show that P/D ratio and E/D ratio affect more on stress distributions near the hole boundary than the other factors. In the case of multi-pin loaded composite laminate, the stress concentration in the double column case is better than the other cases of multi-pin loaded composite laminate.

• Composites Research
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• v.18 no.2
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• pp.46-51
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• 2005

An active inspection system using Lamb waves for structural health monitoring was considered in this paper. In order to understand the characteristics of the Lamb waves propagating in a composite plate, the experiment was performed for a quasi-isotropic composite plate with thickness variation. Lamb waves were generated and received by the thin PZT transducers bonded on the surface. In this test, a simple new technique was tried for characterizing the Lamb waves propagating across the discontinuity due to the thickness variation. The results showed that Lamb waves were more sensitive to the thinner plate with faster group velocity and that the thickness change in composite plate was detectable. Consequently, the potential of applying this technique to structural health monitoring was verified.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.5
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• pp.9-14
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• 2002

A higher order zig-zag plate theory is developed to accurately predict fully coupled mechanical, thermal, and electric behaviors. Both the in-plane displacement and temperature fields through the thickness are constructed by superimposing linear zig-zag field to the smooth globally cubic varying field. Smooth parabolic distribution through the thickness is assumed in the transverse deflection in order to consider transverse normal deformation. Linear zig-zag form is adopted in the electric field. The layer-dependent degrees of freedom of displacement and temperature fields are expressed in tern-is of reference primary degrees of freedom by applying interface continuity conditions as well as bounding surface conditions of transverse shear stresses and transverse heat flux. The numerical examples of coupled and uncoupled analysis demonstrate the accuracy and efficiency of the present theory. The present theory is suitable for the predictions of fully coupled behaviors of thick smart composite plate under mechanical, thermal, and electric loadings combined.

• Journal of KSNVE
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• v.8 no.6
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• pp.1053-1061
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• 1998

In this paper. the power flow analysis(PFA) method is applied to the prediction of the vibrational energy density and intensity of coupled co-planar plates. To cover the energy transmission and reflection at the joint of the plates. the wave transmission approach is Introduced with the assumption that all the incident waves are normal to the joint. By changing the frequency ranges and internal loss factors. we have obtained the reliable PFA results. and compared them with the analytical exact solutions.