• Title/Summary/Keyword: side to thickness ratio

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Novel quasi 3D theory for mechanical responses of FG-CNTs reinforced composite nanoplates

  • Alazwari, Mashhour A.;Daikh, Ahmed Amine;Eltaher, Mohamed A.
    • Advances in nano research
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    • v.12 no.2
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    • pp.117-137
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    • 2022
  • Effect of thickness stretching on free vibration, bending and buckling behavior of carbon nanotubes reinforced composite (CNTRC) laminated nanoplates rested on new variable elastic foundation is investigated in this paper using a developed four-unknown quasi-3D higher-order shear deformation theory (HSDT). The key feature of this theoretical formulation is that, in addition to considering the thickness stretching effect, the number of unknowns of the displacement field is reduced to four, and which is more than five in the other models. Two new forms of CNTs reinforcement distribution are proposed and analyzed based on cosine functions. By considering the higher-order nonlocal strain gradient theory, microstructure and length scale influences are included. Variational method is developed to derive the governing equation and Galerkin method is employed to derive an analytical solution of governing equilibrium equations. Two-dimensional variable Winkler elastic foundation is suggested in this study for the first time. A parametric study is executed to determine the impact of the reinforcement patterns, nonlocal parameter, length scale parameter, side-t-thickness ratio and aspect ratio, elastic foundation and various boundary conditions on bending, buckling and free vibration responses of the CNTRC plate.

Bending of FGM rectangular plates resting on non-uniform elastic foundations in thermal environment using an accurate theory

  • Bouderba, Bachir
    • Steel and Composite Structures
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    • v.27 no.3
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    • pp.311-325
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    • 2018
  • This article presents the bending analysis of FGM rectangular plates resting on non-uniform elastic foundations in thermal environment. Theoretical formulations are based on a recently developed refined shear deformation theory. The displacement field of the present theory is chosen based on nonlinear variations in the in-plane displacements through the thickness of the plate. The present theory satisfies the free transverse shear stress conditions on the top and bottom surfaces of the plate without using shear correction factor. Unlike the conventional trigonometric shear deformation theory, the present refined shear deformation theory contains only four unknowns as against five in case of other shear deformation theories. The material properties of the functionally graded plates are assumed to vary continuously through the thickness, according to a simple power law distribution of the volume fraction of the constituents. The elastic foundation is modeled as non-uniform foundation. The results of the shear deformation theories are compared together. Numerical examples cover the effects of the gradient index, plate aspect ratio, side-to-thickness ratio and elastic foundation parameters on the thermo-mechanical behavior of functionally graded plates. Numerical results show that the present theory can archive accuracy comparable to the existing higher order shear deformation theories that contain more number of unknowns.

Design of High Stiffness and Lightweight Body for Stiffness Distribution Ratio (강성 배분비를 고려한 고강성화 경량화 차체 설계)

  • Yang, Hee-Jong;Kim, Ki-Chang;Lim, Si-Hyung;Kim, Chan-Mook;Yim, Hong-Jae
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.17 no.10
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    • pp.901-906
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    • 2007
  • Lightweight body due to the decrease of panel thickness and reinforcing member might cause low stiffness. On the other hand, high stiffness body requires an increase of mass. Front pillar section area has been decreased for increasing the driver's visual field. Global vehicle stiffness is affected by stiffness distribution ratio between upper part and lower part at a side body structure. This paper describes a process used to evaluate the stiffness distribution ratio based on strain energy. In addition, optimum design schemes are presented for high stiffness and lightweight body structure considering the investigated stiffness distribution ratio.

Numerical studies on non-shear and shear flows past a 5:1 rectangular cylinder

  • Zhou, Qiang;Cao, Shuyang;Zhou, Zhiyong
    • Wind and Structures
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    • v.17 no.4
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    • pp.379-397
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    • 2013
  • Large Eddy Simulations (LES) were carried out to investigate the aerodynamic characteristics of a rectangular cylinder with side ratio B/D=5 at Reynolds number Re=22,000 (based on cylinder thickness). Particular attention was devoted to the effects of velocity shear in the oncoming flow. Time-averaged and unsteady flow patterns around the cylinder were studied to enhance understanding of the effects of velocity shear. The simulation results showed that the Strouhal number has no significant variation with oncoming velocity shear, while the peak fluctuation frequency of the drag coefficient becomes identical to that of the lift coefficient with increase in velocity shear. The intermittently-reattached flow that features the aerodynamics of the 5:1 rectangular cylinder in non-shear flow becomes more stably reattached on the high-velocity side, and more stably separated on the low-velocity side. Both the mean and fluctuating drag coefficients increase slightly with increase in velocity shear. The mean and fluctuating lift and moment coefficients increase almost linearly with velocity shear. Lift force acts from the high-velocity side to the low-velocity side, which is similar to that of a circular cylinder but opposite to that of a square cylinder under the same oncoming shear flow.

Mechanical and hygrothermal behaviour of functionally graded plates using a hyperbolic shear deformation theory

  • Laoufi, Imene;Ameur, Mohammed;Zidi, Mohamed;Bedia, El Abbes Adda;Bousahla, Abdelmoumen Anis
    • Steel and Composite Structures
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    • v.20 no.4
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    • pp.889-911
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    • 2016
  • Using the hyperbolic shear deformation plate model and including plate-foundation interaction (Winkler and Pasternak model), an analytical method in order to determine the deflection and stress distributions in simply supported rectangular functionally graded plates (FGP) subjected to a sinusoidal load, a temperature and moisture fields. The present theory exactly satisfies stress boundary conditions on the top and the bottom of the plate. No transversal shear correction factors are needed because a correct representation of the transversal shearing strain is given. Materials properties of the plate (elastic, thermal and moisture expansion coefficients) are assumed to be graded in the thickness direction according to a simple power-law distribution in terms of the volume fractions of the constituents. Numerical examples are presented and discussed for verifying the accuracy of the present theory in predicting the bending response of FGM plates under sinusoidal load and a temperature field as well as moisture concentration. The effects of material properties, temperature, moisture, plate aspect ratio, side-to-thickness ratio, ratio of elastic coefficients (ceramic-metal) and three distributions for both temperature and moisture on deflections and stresses are investigated.

Hygro-thermo-mechanical bending of S-FGM plates resting on variable elastic foundations using a four-variable trigonometric plate theory

  • Beldjelili, Youcef;Tounsi, Abdelouahed;Mahmoud, S.R.
    • Smart Structures and Systems
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    • v.18 no.4
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    • pp.755-786
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    • 2016
  • The hygro-thermo-mechanical bending behavior of sigmoid functionally graded material (S-FGM) plate resting on variable two-parameter elastic foundations is discussed using a four-variable refined plate theory. The material characteristics are distributed within the thickness direction according to the two power law variation in terms of volume fractions of the constituents of the material. By employing a four variable refined plate model, both a trigonometric distribution of the transverse shear strains within the thickness and the zero traction boundary conditions on the top and bottom surfaces of the plate are respected without utilizing shear correction factors. The number of independent variables of the current formulation is four, as against five in other shear deformation models. The governing equations are deduced based on the four-variable refined plate theory incorporating the external load and hygro-thermal influences. The results of this work are compared with those of other shear deformation models. Various numerical examples introducing the influence of power-law index, plate aspect ratio, temperature difference, elastic foundation parameters, and side-to-thickness ratio on the static behavior of S-FGM plates are investigated.

A simple analytical model for free vibration and buckling analysis of orthotropic rectangular plates

  • Sellam, Souad;Draiche, Kada;Tlidji, Youcef;Addou, Farouk Yahia;Benachour, Abdelkader
    • Structural Engineering and Mechanics
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    • v.75 no.2
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    • pp.157-174
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    • 2020
  • In the present paper, a simple analytical model is developed based on a new refined parabolic shear deformation theory (RPSDT) for free vibration and buckling analysis of orthotropic rectangular plates with simply supported boundary conditions. The displacement field is simpler than those of other higher-order theories since it is modeled with only two unknowns and accounts for a parabolic distribution of the transverse shear stress through the plate thickness. The governing differential equations related to the present theory are obtained from the principle of virtual work, while the solution of the eigenvalue problem is achieved by assuming a Navier technique in the form of a double trigonometric series that satisfy the edge boundary conditions of the plate. Numerical results are presented and compared with previously published results for orthotropic rectangular plates in order to verify the precision of the proposed analytical model and to assess the impacts of several parameters such as the modulus ratio, the side-to-thickness ratio and the geometric ratio on natural frequencies and critical buckling loads. From these results, it can be concluded that the present computations are in excellent agreement with the other higher-order theories.

A Study on the Properties of Porous Concrete For Kelp Forest Regeneration Using Cement Coating Granular Fertilizer (시멘트 코팅 입상비료를 이용한 조장조성용 포러스콘크리트의 특성에 관한 연구)

  • Park Seong Bum;Lee Jun;Kim Jeong Hwan;Seo Dae Seuk;Lee Byung Jae;Song Jae Lib
    • Proceedings of the Korea Concrete Institute Conference
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    • 2005.05b
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    • pp.489-492
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    • 2005
  • The Purpose of this study is to develope the method for early recovery of the biodiversity in the oligotrophical costal area. The result of this study, the dissolution ratio is superior in the case which the cement coating thickness of the granular fertilizer is below 1mm. From the failure-side it is judged with the fact that appropriate to use the separate charging method and vibration compaction method. For the cases of the mixing ratio of cement coating granular fertilizer, there was not any clear tendency for the change of the strength up to 20$\%$ of the mixing ratio. However, at the 30$\%$ mixing ratio, decrease of the strength was noticed. So it can be concluded that the stability can be achieved in the range of 20$\%$ and below.

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Polarization splitting characteristics of the side-polished fiber coupler with a thin metal interlayer (금속층이 포함된 측면 연마 광섬유 결합기의 편광 분리 특성)

  • 김광택;황보승
    • Korean Journal of Optics and Photonics
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    • v.13 no.3
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    • pp.228-234
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    • 2002
  • We report theoretical investigation on the polarization selective coupling characteristics of a side-polished fiber directional coupler with a thin metal interlayer. Based on normal mode theory the coupling properties of the device under various structural conditions are analyzed. It is shown that the coupling strength between TE modes weakens rapidly with increase or metal interlayer thickness, whereas that between TM modes becomes stronger. The design conditions of the polarization splitter using the coupler to achieve high extinction ratio and low insertion loss are presented.

Free Convective Heat Transfer in a Vertical Channel with Heat Source at the Wall (벽에서 열원이 있는 수직채널안의 자연대류열전달)

  • Pak, Hi-Yong;Doo, Min-Soo
    • The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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    • v.14 no.2
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    • pp.108-117
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    • 1985
  • In this study, a numerical analysis was performed for the natural convection heat transfer in a vertical channel which was consisted of two finite-thickness vertical walls with heat source. The ratio of the thermal conductivity of wall to air played an important role in the analysis. The case for which one side wall has protrusion resistances was also examined. The governing equations for the system was discretized by control volume formulation and solved by SIMPLE method. As the result of this study, it was found that the uniform heat flux boundary condition could be applied when the conductivity ratio was below approximately 50 and the uniform temperature boundary condition could be used when the conductivity rat io was over approximately 15,000. However, when the conductivity ratio was between 50 and 15,000, the thermal conductivity ratio value should be considered for the analysis. It was also found that the existence of protrusion resistance influenced the thermal field up to the distance of 3-4 times of the protrusion length.

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