• Nuclear Engineering and Technology
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• 제56권7호
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• pp.2767-2774
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• 2024

In this study, investment casting shell waste successfully utilized to produce cordierite/mullite/zircon composites. Green pellets, consisting of investment casting shell waste, alumina, and magnesia, were prepared and sintered at temperatures between 1250 and 1350 ℃. The influence of the sintering temperature on the crystalline phase composition, densification behavior, flexural strength, microstructure, and radiation shielding properties of the cordierite/mullite/zircon composites is investigated. Phase analysis showed that characteristic cordierite peaks appear at 1250 ℃, but the complete conversation of silica from investment casting shell waste into cordierite requires a sintering temperature of at least 1300 ℃. Notably, the cordierite/mullite/zircon composite sintered at 1350 ℃ exhibited a sixfold increase in flexural strength compared to the ceramic composite directly fabricated from investment casting shell waste at the same sintering temperature. Furthermore, the effect of Y₂O₃ addition on composites' radiation shielding properties is investigated. The results show that the Y₂O₃ addition improves densification behavior, enhancing the shielding capabilities of the composites against fast neutron and gamma radiation. Our findings suggest that the developed ceramic composites show significant potential for gamma-ray and neutron shielding applications.

• Steel and Composite Structures
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• 제2권1호
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• pp.67-84
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• 2002

Traffic decks of steel or composite motorway bridges sometimes provide the opportunity of using the composite action between an existing steel deck and a reinforced concrete plate (RC plate) in the process of rehabilitation, i.e., to increase the load-carrying capacity of the deck for concentrated traffic loads. The steel decks may be orthotropic decks or also unstiffened steel plates, which during the rehabilitation are connected with the RC plate by shear studs, such developing an improved local load distribution by the joint behaviour of the two plate elements. Investigations carried out, both experimentally and numerically, were performed in order to quantitatively assess the combined static behaviour and to qualitatively verify the usability of the structure for dynamic loading. The paper reports on the testing, the numerical simulation as well as the comparison of the results. Conclusions drawn for practical design indicated that the static behaviour of these structures may be very efficient and can also be analysed numerically. Further, the results gave evidence of a highly robust behaviour under fatigue equivalent cyclic traffic loading.

• 한국자동차공학회논문집
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• 제7권9호
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• pp.119-130
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• 1999

This paper deals buckling behavior of laminated composite cylindrical shells subjected to combination of axial compression and torison. Linear and nonlinear finite element analysis are carried out . the influence of load type, load ratio, fiber orientation angle, stacking sequence, and intial imperfect on buckling behavior is discussed.

• 한국생산제조학회지
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• 제6권2호
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• pp.49-58
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• 1997

The objective of this study is to investigate effects of prebuckling on the bucking of laminated compostie cylindrical shells, Both axial compression and lateral pressure are considered for laminated composite cylindrical shells with length to radius ratios. The shell walls are made of a laminate with several symmetric ply orientations. The study was using finite difference energy method, utilizing the nonlinear bifurcation branch with nonlinear prebuckling displacements. The results are compared to the buckling loads determined when membrane prebuckling displacements are considered.

• Bulletin of the Korean Chemical Society
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• 제35권11호
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• pp.3303-3306
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• 2014

A facile and effective approach has been developed to prepare hybrid hollow microspheres, via consecutive processes of pickering mini-emulsion polymerization for core-shell formation, and calcination of the sacrificial core. The resulting hollow composite particles have mono-layered shells. The morphology and size characteristics of synthesized composite particles were investigated, using dynamic light scattering (DLS) and scanning electron microscopy (SEM) measurements.

• 한국구조물진단유지관리공학회 논문집
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• 제8권2호
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• pp.247-258
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• 2004

복합적층 곡선패널의 비감쇠 강제진동문제를 해결하기 위한 쉘 요소를 제안하였다. 본 연구에서는 절점당 6개의 자유도를 갖는 4절점 EAS 쉘요소를 사용하였다. EAS 방법을 이용하여 전단잠김과 면내잠김 현상을 극복하였으며, 전단보정계수를 사용하지 않고 분포형상함수에 의해 두께방향에 따른 전단변형을 포물선으로 분포시킨 수정된 1차전단변형이론을 적용하였다. Newmark 직접적분법이 시간에 관한 운동방정식의 적분과 시간이력을 해결하기 위해 적용되었다. 곡선패널의 기하학적 조건과 화이버 보강각도 및 적층조건 등의 매개변수 변화에 따른 강제진동응답을 분석하였다.

• Structural Engineering and Mechanics
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• 제4권2호
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• pp.111-124
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• 1996

New active "intelligent" structural systems with integrated self-sensing, diagnosis, and control capabilities can lead to a new design dimension for the next generation high-performance structures and mechanical systems. However, temperature effects to the piezoelectric transducers are not fully understood. This paper is concerned with a mathematical modeling and analysis of a laminated piezothermoelastic cylindrical shell composite exposed to mechanical, electric, and thermal fields. Generic shell equations and solution procedures are derived. Contributions of spatial and time components in the mechanical, electric, and temperature excitations are discussed, and their analytical solutions derived. A laminated cylindrical shell composite with fully distributed piezoelectric layers is used in a case study; its multi-field step and impulse responses are investigated. Analyses suggest that the fully distributed actuators are insensitive to even modes due to load averaging and cancellation. Accordingly, these even modes are filtered from the total response and only the modes that are combinations of m = 1, 3, 5, ${\cdots}$ and n = 1, 3, 5, ${\cdots}$ participating in dynamic response of the shell.

• Advances in materials Research
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• 제7권3호
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• pp.185-194
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• 2018

The mechanism of biological materials structure is very complex and has optimal properties compared to engineering materials. Top Neck mollusks shells, as an example of biological materials, have hierarchical structure, which 95 percent of its structure is Aragonite and 5 percent organic materials. This article detected mechanical properties of the Top Neck mollusks shell as a Nano composite using Nano-indentation method in different situations. Research findings indicate that mechanical properties of the Top Neck mollusks shell including elastic modulus and hardness are higher than a fresh one preserved in -50 centigrade and also a Top Neck mollusks shell preserved in environmental conditions. Nano-indentation test results are so close in range, overall, that hardness degree is 3900 to 5200 MPa and elastic modulus is 70 to 85 GPa.

• 한국정밀공학회지
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• 제22권2호
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• pp.164-171
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• 2005

This study aims to examine an effect of stacking sequence and curvature on the penetration characteristic of a composite laminated shell. For the purpose, we manufactured specimens with different stacking sequences and curvatures, and conducted a penetration test using an air-gun. To examine an influence according to stacking sequence, as flat plate and curvature specimen had more plies, their critical penetration energy was higher, Critical penetration energies of specimen A and C with less interfaces somewhat higher than those of B and D with more interfaces. The reason that with less interfaces, critical penetration energy was higher is pre-impact bending stiffness of composite laminated shell with less interfaces was lower than that of laminated shell with more interfaces, but bending stiffness after impact was higher. And it is because interface, the weakest part of the composite laminated shell, was influenced by transverse impact. As curvature increases, critical penetration energy increases linearly. It is because as curvature increases, resistance to in-plane deformation as well as bending deformation increases, which need higher critical penetration energy. Patterns of cracks caused by penetration of composite laminated shells include interlaminar crack, intralaminar crack, and laminar fracture. A 0$^{\circ}$ply laminar had a matrix crack, a 90$^{\circ}$ply laminar had intralaminar crack and laminar fracture, and interface between 0$^{\circ}$and 90$^{\circ}$laminar had a interlaminar crack. We examined crack length and delamination area through a penetration test. For the specimen A and C with 2 interface, the longest circumferential direction crack length and largest delamination area were observed on the first interface from the impact point. For the specimen B and D with 4 interface, the longest crack length and largest delamination area were observed on the third interface from the impact point.

• 대한기계학회논문집A
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• 제33권1호
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• pp.1-26
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• 2009

Cylindrical shells of isotropic and composite laminated materials are being used many engineering applications. This paper reviews the literature focusing on various aspects of shell research. The aspects of research receiving interest here are the cylindrical theory being used, the stress, buckling analysis and the impact analysis. The vibration analyses and stiffening characteristics of the cylindrical shell are investigated. The design optimizations of the cylindrical shell are reviewed. The studies on the conical and spherical shell are also reviewed. This review aticles contain 236 referencees.