• 제목/요약/키워드: shell structure

검색결과 1,063건 처리시간 0.025초

Preparation of Al@Fe2O3 Core-Shell Composites Using Amphiphilic Graft Copolymer Template

  • Patel, Rajkumar;Kim, Sang Jin;Kim, Jin Kyu;Park, Jung Su;Kim, Jong Hak
    • Korean Chemical Engineering Research
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    • 제52권2호
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    • pp.209-213
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    • 2014
  • A graft copolymer of poly(vinyl chloride)-g-poly(oxyethylene methacrylate) (PVC-g-POEM) was synthesized via atom transfer radical polymerization (ATRP) and used as a structure-directing agent to prepare $Al@Fe_2O_3$ core-shell nanocomposites through a sol-gel process. The amphiphilic property of PVC-g-POEM allows for good dispersion of Al particles and leads to specific interaction with iron ethoxide, a precursor of $Fe_2O_3$. Secondary bonding interaction in the sol-gel composites was characterized by Fourier transform-infrared (FT-IR) spectroscopy. The well-organized morphology of $Al@Fe_2O_3$ core-shell nanocomposites was observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Energy dispersive X-ray (EDX) and X-ray diffraction (XRD) were used to analyze the elemental composition and crystallization structure of the composites.

Viscous fluid induced vibration and instability of FG-CNT-reinforced cylindrical shells integrated with piezoelectric layers

  • Bidgoli, Mahmood Rabani;Karimi, Mohammad Saeed;Arani, Ali Ghorbanpour
    • Steel and Composite Structures
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    • 제19권3호
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    • pp.713-733
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    • 2015
  • In this paper, viscous fluid induced nonlinear free vibration and instability analysis of a functionally graded carbon nanotube-reinforced composite (CNTRC) cylindrical shell integrated with two uniformly distributed piezoelectric layers on the top and bottom surfaces of the cylindrical shell are presented. Single-walled carbon nanotubes (SWCNTs) are selected as reinforcement and effective material properties of FG-CNTRC cylindrical shell are assumed to be graded through the thickness direction and are estimated through the rule of mixture. The elastic foundation is modeled by temperature-dependent orthotropic Pasternak medium. Considering coupling of mechanical and electrical fields, Mindlin shell theory and Hamilton's principle, the motion equations are derived. Nonlinear frequency and critical fluid velocity of sandwich structure are calculated based on differential quadrature method (DQM). The effects of different parameters such as distribution type of SWCNTs, volume fractions of SWCNTs, elastic medium and temperature gradient are discussed on the vibration and instability behavior of the sandwich structure. Results indicate that considering elastic foundation increases frequency and critical fluid velocity of system.

Sintering Behavior of Ag-Ni Electrode Powder with Core-shell Structure

  • Kim, Kyung Ho;Koo, Jun-Mo;Ryu, Sung-Soo;Yoon, Sang Hun;Han, Yoon Soo
    • 한국표면공학회지
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    • 제49권6호
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    • pp.507-512
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    • 2016
  • Expensive silver powder is used to form electrodes in most IT equipment, and recently, many attempts have been made to lower manufacturing costs by developing powders with Ag-Ni or Ag-Cu core-shell structures. This study examined the sintering behavior of Ag-Ni electrode powder with a core-shell structure for silicon solar cell with high energy efficiency. The electrode powder was found to have a surface similar to pure Ag powder, and cross-sectional analysis revealed that Ag was uniformly coated on Ni powder. Each electrode was formed by sintering in the range of $500^{\circ}C$ to $800^{\circ}C$, and the specimen sintered at $600^{\circ}C$ had the lowest sheet resistance of $5.5m{\Omega}/{\Box}$, which is about two times greater than that of pure Ag. The microstructures of electrodes formed at varying sintering temperatures were examined to determine why sheet resistance showed a minimum value at $600^{\circ}C$. The electrode formed at $600^{\circ}C$ had the best Ag connectivity, and thus provided a better path for the flow of electrons.

보구조물의 유연이음을 이용한 쉘구조물의 기하학적 비선형해석에 관한 연구 (A Study on the Geometrically Nonlinear Analysis of Shell Structures Using the Flexible Joints of Beam Structures)

  • 김성익;이창훈;민옥기
    • 전산구조공학
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    • 제10권1호
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    • pp.213-223
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    • 1997
  • 복잡한 구조물의 거동을 해석하는 데 있어서 초기 설계단계에서 부터 쉘요소를 사용하여 해석하는 것은 많은 시간과 경비가 요구된다. 이에 경비절감의 측면에서 쉘구조물을 단순 보구조물에 의해 모델링함에 의해 분석하고자 하는 연구가 진행되어왔다. 본 연구에서는 단순화된 보구조물의 결합부에 고려하기 위한 유연도를 나타내는 굽힘회전강성을 결정하는 방법을 제안하고, 제안된 방법을 통해 얻어진 결합부에서의 유연도을 보구조물의 결합부에 적용하여 비선형해석을 수행한다. 수치해석 결과로 쉘구조물에서 나타나는 기하학적 비선형거동을 결합부에서 유연도를 고려하는 단순 보구조물에 의해 작은 오차의 범위안에서 기술할 수 있었다.

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Vibrational behavior of exponentially graded joined conical-conical shells

  • Rezaiee-Pajand, Mohammad;Sobhani, Emad;Masoodi, Amir R.
    • Steel and Composite Structures
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    • 제43권5호
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    • pp.603-623
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    • 2022
  • This article is dedicated to predict the natural frequencies of joined conical shell structures made of Functionally Graded Material (FGM). The structure includes two conical segments. The equivalent material properties are found by using the rule of mixture based on Voigt model. In addition, three well-known patterns are employed for distribution of material properties throughout the thickness of the structure. The main objective of the present research is to propose a novel exponential pattern and obtain the related equivalent material properties. Furthermore, the Donnell type shell theory is used to obtain the governing equations of motion. Note that these equations are obtained by employing First-order Shear Deformation Theory (FSDT). In order to discretize the governing system of differential equations, well-known and efficient semi-analytical scheme, namely Generalized Differential Quadrature Method (GDQM), is utilized. Different boundary conditions are considered for various types of single and joined conical shell structures. Moreover, an applicable modification is considered for the continuity conditions at intersection position. In the first step, the proposed formulation is verified by solving some well-known benchmark problems. Besides, some new numerical examples are analyzed to show the accuracy and high capability of the suggested technique. Additionally, several geometric and material parameters are studied numerically.

A modified shell-joint model for segmental tunnel dislocations under differential settlement

  • Jianguo Liu;Xiaohui Zhang;Yuyin Jin;Wenyuan Wang
    • Geomechanics and Engineering
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    • 제35권4호
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    • pp.411-424
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    • 2023
  • Reasonable estimates of tunnel lining dislocations in the operation stage, especially under longitudinal differential settlement, are important for the design of waterproof gaskets. In this paper, a modified shell-joint model is proposed to calculate shield tunnel dislocations under longitudinal differential settlement, with the ability to consider the nonlinear shear stiffness of the joint. In the case of shell elements in the model, an elastoplastic damage constitutive model was adopted to describe the nonlinear stress-strain relationship of concrete. After verifying its applicability and correctness against a full-scale tunnel test and a joint shear test, the proposed model was used to analyze the dislocation behaviors of a shield tunnel in Shanghai Metro Line 2 under longitudinal differential settlement. Based on the results, when the tunnel structure is solely subjected to water-earth load, circumferential and longitudinal joint dislocations are all less than 0.1 mm. When the tunnel suffers longitudinal differential settlement and the curvature radius of the differential settlement is less than 300 m, although maximum longitudinal joint dislocation is still less than 0.1 mm, the maximum circumferential joint dislocation is approximately 10.3 mm, which leads to leakage and damage of the tunnel structure. However, with concavo-convex tenons applied to circumferential joints, the maximum dislocation value reduces to 4.5 mm.

동심축류가 유도되는 미세유체 소자 기반 Collagen Type I 미세섬유의 제작 (Fabrication of Collagen Type I Microfiber based on Co-axial Flow-induced Microfluidic Chip)

  • 이수경;이광호
    • 대한의용생체공학회:의공학회지
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    • 제37권5호
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    • pp.186-194
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    • 2016
  • In this study, a co-axial flow induced microfluidic chip to fabricate pure collagen type I microfiber via the control of collagen type I and Na-alginate gelation process. The pure collagen type I microfiber was generated by selective degradation of Ca-alginate from 'Core-Shell' structured hydrogel microfiber. To make 'Core-Shell' structure, collagen type I solution was introduced into core channel and 1.5% Na-alginate solution was injected into side channel in microfluidic chip. To evaluatethe 'Core-Shell' structure, the red and green fluorescence substances were mixed into collagen type I and Na-alginate solution, respectively. The fluorescence substances were uniformly loaded into each fiber, and the different fluorescence images were dependent on their location. By immoblizing EpH4-Ras and C6 cells within collagen type I and Na-alginate solution, we sucessfully demonstrated the co-culture of EpH4-Ras and C6 cells with 'Core-Shell' like hydrogel microfiber for 5 days. Only to produce pure collagen type I hydrogel fiber, tri-sodium citrate solution was used to dissolve the shell-like Ca-alginate hydrogel fiber from 'Core-Shell' structured hydrogel microfiber, which is an excellent advantage when the fiber is employed in three-dimensional scaffold. This novel method could apply various application in tissue engineering and biomedical engineering.

소방.가스안전용 헬멧의 강도안전성에 관한 연구 (A Study on the Strength Analysis of the Helmets for Fire and Gas Safety)

  • 김한구;심종현;김청균
    • 한국가스학회지
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    • 제12권3호
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    • pp.31-37
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    • 2008
  • 본 본문에서는 유한요소법을 사용하여 여러 가지 헬멧 모델의 강도안전에 관한 응력과 변형률을 해석하였다. 차세대 헬멧은 작업자의 안전성과 작업성을 높일 수 있도록 제작되어야 하고, 오랫동안 착용해도 불편함이 없으면서 머리를 보호할 수 있어야 한다. 결국 헬멧은 안전하고, 착용성이 좋아야 하며, 헬멧의 모체 구조물을 가볍게 제작해야 한다. 따라서 헬멧은 화재나 가스폭발과 같은 가혹한 작업조건에 잘 견딜 수 있어야 한다. FEM 해석결과에 의하면, 외부의 충격력이 헬멧모체 구조물의 정상부 지역에 가해졌을 경우 최대응력과 변형률은 하중이 작용되는 지점부위에서 발생하였다. 따라서 헬멧의 모체 구조물에는 보강뼈대를 설치하고 두께를 늘려서 강도안전성을 확보하는 것이 중요하다. 반면에 헬멧의 일반적인 균일한 두게는 줄여서 헬멧의 경량화를 추구하는 것도 중요하다.

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Feasibility study on the wide and long 9%Ni steel plate for use in the LNG storage inner tank shell

  • Chung, Myungjin;Kim, Jongmin;Kim, Jin-Kook
    • Steel and Composite Structures
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    • 제32권5호
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    • pp.571-582
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    • 2019
  • This study aimed to assess the feasibility on the wide and long 9%Ni steel plate for use in the LNG storage inner tank shell. First, 5-m-wide and 15-m-long 9%Ni steel plates were test manufactured from a steel mill and specimens taken from the plates were tested for strength, toughness, and flatness to verify their performance based on international standards and design specifications. Second, plates with a thickness of 10 mm and 25 mm, a width of 4.8~5.0 m, and a length of 15 m were test fabricated by subjecting to pretreatment, beveling, and roll bending resulting in a final width of 4.5~4.8 m and a length of 14.8m with fabrication errors identical to conventional plates. Third, welded specimens obtained via shield metal arc welding used for vertical welding of inner tank shell and submerged arc welding used for horizontal welding were also tested for strength, toughness and ductility. Fourth, verification of shell plate material and fabrication was followed by test erection using two 25-mm-thick, 4.5-m-wide and 14.8-m-long 9%Ni steel plates. No undesirable welding failure or deformation was found. Finally, parametric design using wide and long 9%Ni steel plates was carried out, and a simplified design method to determine the plate thickness along the shell height was proposed. The cost analysis based on the parametric design resulted in about 2% increase of steel weight; however, the construction cost was reduced about 6% due to large reduction in welding work.

초음파를 이용한 구리-은 코어-쉘의 합성 및 전도성 페이스트 적용 (Sonochemical Synthesis of Copper-silver Core-shell Particles for Conductive Paste Application)

  • 심상보;한종대
    • 공업화학
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    • 제29권6호
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    • pp.782-788
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    • 2018
  • 서브 미크론 구리-은 코어-쉘 Cu@Ag 입자를 초음파화학과 결합된 금속교환 반응으로 합성하고 인쇄용 전자부품을 위한 저렴한 전도성 페이스트 적용을 평가하였다. 코어-쉘의 합성을 위한 반응에서 코어로 사용된 $Cu_2O/Cu$ 복합체의 $Cu_2O$는 초음파화학 반응으로 Cu로 환원되고 Cu 원자는 Ag의 금속교환 반응의 환원제로 작용하여 코어 표면에 Ag가 코팅된 코어-쉘 구조를 얻었다. TEM-EDS와 TG-DSC를 이용하여 서브 미크론 입자의 코어-쉘 구조를 확인하였다. 70 wt% Cu@Ag를 용매에 분산시킨 전도성 페이스트를 결합제와 습윤제를 사용하여 제조하고, 스크린 인쇄법을 사용하여 폴리아미드 필름상에 코팅하였다. Ag 함량이 8 at%와 16 at%인 Cu@Ag 입자를 함유하는 인쇄된 페이스트 필름은 공기 중의 $180^{\circ}C$에서 소결한 후 각각 96.2와 $38.4{\mu}{\Omega}cm$의 낮은 비저항 값을 나타내었다.