• Title/Summary/Keyword: dissipation effects

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Thermoelastic interaction in functionally graded nanobeams subjected to time-dependent heat flux

  • Zenkour, Ashraf M.;Abouelregal, Ahmed E.
    • Steel and Composite Structures
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    • v.18 no.4
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    • pp.909-924
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    • 2015
  • This paper investigates the vibration phenomenon of a nanobeam subjected to a time-dependent heat flux. Material properties of the nanobeam are assumed to be graded in the thickness direction according to a novel exponential distribution law in terms of the volume fractions of the metal and ceramic constituents. The upper surface of the functionally graded (FG) nanobeam is pure ceramic whereas the lower surface is pure metal. A nonlocal generalized thermoelasticity theory with dual-phase-lag (DPL) model is used to solve this problem. The theories of coupled thermoelasticity, generalized thermoelasticity with one relaxation time, and without energy dissipation can extracted as limited and special cases of the present model. An analytical technique based on Laplace transform is used to calculate the variation of deflection and temperature. The inverse of Laplace transforms are computed numerically using Fourier expansion techniques. The effects of the phase-lags (PLs), nonlocal parameter and the angular frequency of oscillation of the heat flux on the lateral vibration, the temperature, and the axial displacement of the nanobeam are studied.

Comparisons on Dielectric and Peizoelectric Proeprties of Rhombohedral, Tetragonal and Morphotropic Phase Boundary in Pb(Ni1/3Nb2/3)O3-PbTiO3-PbZrO3 System with MnO2 Addition (Pb(Ni1/3Nb2/3)O3-PbTiO3-PbZrO3계의 삼방정, 정방정 및 상경계조성에서의 MnO2 첨가에 따른 유전 및 압전특성에 비교)

  • 전구락;손정호;김정주;조상희
    • Journal of the Korean Ceramic Society
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    • v.25 no.5
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    • pp.488-494
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    • 1988
  • Effects of MnO2 addition on themicrostructure, dielectric and piezoelectric properties of Rhombohedral, Tetragonal and Morphotropic phase boundary(MPB) in Pb(Ni1/3Nb2/3)O3-PbTiO3-PbZrO3 system were investigated and respectively the amount of MnO2 addition was 0, 0.2, 0.5, 1.0, 3.0wt%. In the tetragonal region, compared with the Rhombohedral and Morpotropic phase boundary, Mechanical quality factor(Qm), Curie temperature(Tc) and Dissipation factor were promoted by addition of MnO2. According to the results of the microstructure, dielectric and piezoelectric properties, the solid solution range of MnO2 addition in this system was 0.2-0.5wt%.

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NUMERICAL ANALYSIS OF FLOW AROUND A SUBMERGED BODY NEAR A PYCNOCLINE USING THE GHOST FLUID METHOD ON UNSTRUCTURED GRIDS (비정렬 격자에서 Ghost Fluid 법을 이용한 밀도약층 주위 수중운동체에 의한 유동 해석)

  • Shin, Sang-Mook
    • Journal of computational fluids engineering
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    • v.10 no.3 s.30
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    • pp.70-76
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    • 2005
  • A two-layer incompressible time-accurate Euler solver is applied to analyze flow fields around a submerged body moving at a critical speed near a pycnocline. Discontinuities in the dependent variables across the material interface are captured without any dissipation or oscillation using the ghost fluid method on an unstructured grid. It is shown that the material interlace has significant effects on forces acting on a submerged body moving near a pycnocline regardless of the small difference in densities of two layers. Contrary to the shallow water waves, a submerged body can reach a critical speed at very low Froude number due to the small difference in the densities of the two layers.

Submerged Membrane Beakwaters II: A Rahmen Type System Composed of Horizontal and Vertical Membranes

  • Kee S.T.
    • Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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    • 2004.08a
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    • pp.150-159
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    • 2004
  • In the present paper, the hydrodynamics properties of a Rahmen type flexible porous breakwater with dual fixed-pontoon system interacting with obliquely or normally incident small amplitude waves are numerically investigated. This system is composed of dual vertical porous membranes hinged a the side edges of dual fixed pontoons, and a submerged horizontal membrane that both ends are hinged at the steel frames mounted pontoons. The dual vertical membranes are extended downward and hinged at bottom steal frame fixed into seabed. The wave blocking and dissipation mechanism and its effects of permeability, Rahmen type membrane and pontoon geometry, pre-tensions on membranes, relative dimensionless wave number, and incident wave headings are thoroughly examined.

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Effects of Energy-Dissipation by Stepped Gabion Slope in Rapidly Varied Flow (계단식 Gabion의 경사에 따른 급변류의 에너지 소산효과)

  • Kuem, Do-Hun;Lee, Chang-Yun;Bae, Sang-Soo;Lee, Seung-Yun;Jee, Hong-Kee
    • Proceedings of the Korea Water Resources Association Conference
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    • 2006.05a
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    • pp.1605-1610
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    • 2006
  • 계단식 Gabion 낙차공은 다공체 구조물로서 시공하기 쉽고 안정적이며, 하천유수에 대하여 저항성이 있어 하천구조물로서 널리 자주 사용되고 있다. Gabion은 다공체로서 유수력을 쉽게 흡수함으로써 감세지 계단표면의 위치에너지를 소산시키는데 매우 효과적이다. Stephenson은 1/10 축적을 가진(투수성이 있고 하천낙차공에만 적용되는 투수성 상류면을 가진 높이 4m까지의) 계단식 Gabion을 월류 실험한 바가 있으며, 그 연구결과가 실무에서 인용되고 있다. 그러나 본 연구에서는 급변류의 에너지 소산효과를 조사하기 위하여 중력이 다른 힘들보다 지배적이므로 Froude 상사법칙을 이용하고 1/1, 1/2, 1/3 경사를 가진 계단을 적용하였다. 실험에서는 경사를 가진 높이 4m 계단식 위어와 게비온 감세지 실험, 계단모형실험(보통구조, 층상구조, 끝단이 올라간 구조, 턱을 가진 구조), 격리수맥흐름, 부분수맥흐름으로 제안하여 경사에 따른 급변류의 에너지 소산효과에 대한 결과를 얻을 수 있었다.

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Experimental Study of High Strength Concrete Beam-Column-Slab Connections subjected to cyclic loading (고강도 콘크리트 보-기둥-슬래브 접합부의 반복하중 실험)

  • 오영훈;오정근;장극관;김윤일
    • Proceedings of the Korea Concrete Institute Conference
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    • 1995.04a
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    • pp.339-344
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    • 1995
  • In the design of ductile moment-resisting frames (DMRFs) following the strong column-weak beam dsign philosophy, it is desirable that the joint and column remain essentially elastic in order to insure proper energy dissipation and lateral stability of the structure. The joint has been identified as the "weak link" in DMRFs because any stiffness or strength deterioration in this region can lead to substantial drifts and the possibility of collapse due to P-delta effects. Moreover, the engineer is faced with the difficult task of detailing an element whose size is determined by the framing members, but which must resist a set of loads very different from those used in the design of the beams and columns. Four 2/3-scale beam-column-slab joint assemblies were designed according to existing code requirements of ACI 318-89, representing interior joints of DMRFs with reinforced high strength concrete. The influence on aseismic behavior of beam-column joints due to monolithic slab, has been investigated.estigated.

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Effects of Fluid Resistance Coefficient on Wave Characteristics around Permeable Submerged Breakwater

  • Kim, Namhyeong;Woo, Sumin;Ko, Yongsu
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • 2014.06a
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    • pp.244-245
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    • 2014
  • Recently, the studies on submerged breakwater are increased due to needs considering the quality of water and the scenic view. In this paper, waves coming to permeable submerged breakwater coming with oblique angle are computed numerically by using wave pressure function. The wave pressure function throughout the analytical region including the fluid and submerged breakwaters is used. An unknown quantity expressed by the wave pressure function is simulated by boundary element method. The maximum reflection coefficient shows the tendency of decrease with the increase of oblique angle and The reflection coefficient shows the tendency of increase with the increase of the values of the linear dissipation coefficient and the added mass coefficient. It is means that the reflection coefficients are strongly dependent on the oblique angle and resistance coefficients.

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Electrical and Mechanical Properties of Gamma-ray Irradiated LDPE/EVA Blends (${\gamma}$-선 조사에 따른 LDPE/EVA 블랜드의 전기적, 기계적 특성)

  • Lee, Chung;Kim, Ki-Yup;Kim, Gyu-Baek;Jung, Sang-Ho;Ryu, Boo-Hyung
    • Journal of the Korean Society of Safety
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    • v.21 no.4 s.76
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    • pp.55-59
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    • 2006
  • The radiation effects on electrical and mechanical properties of LDPE/EVA blends with various vinyl acetate contents were investigated. Radiation degradation of LDPE/EVA blends were studied by using gelation, volume resistivity, permittivity, dissipation factor, elongation at break, and E-modulus. As vinyl acetate contents increased in LDPE/EVA blends, electrical insulation characteristics were deteriorated, but flexibility was improved. As irradiation doses increased, electrical insulation characteristics were improved, but flexibility was deteriorated.

Stochastic analysis of elastic wave and second sound propagation in media with Gaussian uncertainty in mechanical properties using a stochastic hybrid mesh-free method

  • Hosseini, Seyed Mahmoud;Shahabian, Farzad
    • Structural Engineering and Mechanics
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    • v.49 no.1
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    • pp.41-64
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    • 2014
  • The main objective of this article is the exploitation of a stochastic hybrid mesh-free method based on stochastic generalized finite difference (SGFD), Newmark finite difference (NFD) methods and Monte Carlo simulation for thermoelastic wave propagation and coupled thermoelasticity analysis based on GN theory (without energy dissipation). A thick hollow cylinder with Gaussian uncertainty in mechanical properties is considered as an analyzed domain for the problem. The effects of uncertainty in mechanical properties with various coefficients of variations on thermo-elastic wave propagation are studied in details. Also, the time histories and distribution on thickness of cylinder of maximum, mean and variance values of temperature and radial displacement are studied for various coefficients of variations (COVs).

Effect of the laser pulse on transient waves in a non-local thermoelastic medium under Green-Naghdi theory

  • Sarkar, Nantu;Mondal, Sudip;Othman, Mohamed I.A.
    • Structural Engineering and Mechanics
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    • v.74 no.4
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    • pp.471-479
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    • 2020
  • This paper aims to study the effect of the elastic nonlocality on the transient waves in a two-dimensional thermoelastic medium influenced by thermal loading due to the laser pulse. The bounding plane surface is heated by a non-Gaussian laser beam. The problem is discussed under the Eringen's nonlocal elasticity model and the Green-Naghdi (G-N) theory with and without energy dissipation. The normal mode analysis method is used to get the exact expressions for the physical quantities which illustrated graphically by comparison and discussion. The effects of nonlocality and different values of time on the displacement, the stresses, and the temperature were made numerically. All the computed results obtained have been depicted graphically and explained.