• Title/Summary/Keyword: shear stability index

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A numerical method for dynamic characteristics of nonlocal porous metal-ceramic plates under periodic dynamic loads

  • Abdulrazzaq, Mohammed Abdulraoof;Kadhim, Zeyad D.;Faleh, Nadhim M.;Moustafa, Nader M.
    • Structural Monitoring and Maintenance
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    • v.7 no.1
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    • pp.27-42
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    • 2020
  • Dynamic stability of graded nonlocal nano-dimension plates on elastic substrate due to in-plane periodic loads has been researched via a novel 3- unknown plate theory based on exact position of neutral surface. Proposed theory confirms the shear deformation effects and contains lower field components in comparison to first order and refined 4- unknown plate theories. A modified power-law function has been utilized in order to express the porosity-dependent material coefficients. The equations of nanoplate have been represented in the context of Mathieu-Hill equations and Chebyshev-Ritz-Bolotin's approach has been performed to derive the stability boundaries. Detailed impacts of static/dynamic loading parameters, nonlocal constant, foundation parameters, material index and porosities on instability boundaries of graded nanoscale plates are researched.

A New Code for Relativistic Hydrodynamics

  • Seo, Jeongbhin;Kang, Hyesung;Ryu, Dongsu
    • The Bulletin of The Korean Astronomical Society
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    • v.45 no.1
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    • pp.55.1-55.1
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    • 2020
  • In an attempt to investigate the nonlinear dynamics such as shock, shear, and turbulence associated with ultra-relativistic jets, we develop a new relativistic hydrodynamics (RHD) code based on the weighted essentially non-oscillatory (WENO) scheme. It is a 5th-order accurate, finite-difference scheme, which has been widely used for solving hyperbolic systems of conservation equations. The code is parallelized with MPI and OpenMP. Through an extensive set of tests, the accuracy and efficiency of different WENO reconstructions, and different time discretizations are assessed. Different implementations of the equation of state (EOS) for relativistic fluid are incorporated, As the fiducial setup for simulations of ultra-relativistic jets, we adopt the EOS in Ryu et al. (2006) to treat arbitrary adiabatic index of relativistic fluid, the WENO-Z reconstructions to minimize numerical dissipation without loss of stability, and the strong stability preserving Runge-Kutta (SSPRK) method to achieve stable time stepping with large CFL numbers. In addition, the code includes a high-order flux averaging along the transverse directions for multi-dimensional problems, and the modified eigenvalues for the acoustic modes to effectively control the carbuncle instability. We find that the new code performs satisfactorily simulations of ultra-relativistic jets.

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Dynamic stability and nonlinear vibration of rotating sandwich cylindrical shell with considering FG core integrated with sensor and actuator

  • Rostami, Rasoul;Mohamadimehr, Mehdi;Rahaghi, Mohsen Irani
    • Steel and Composite Structures
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    • v.32 no.2
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    • pp.225-237
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    • 2019
  • In this research, the dynamic stability and nonlinear vibration behavior of a smart rotating sandwich cylindrical shell is studied. The core of the structure is a functionally graded material (FGM) which is integrated by functionally graded piezoelectric material (FGPM) layers subjected to electric field. The piezoelectric layers at the inner and outer surfaces used as actuator and sensor, respectively. By applying the energy method and Hamilton's principle, the governing equations of sandwich cylindrical shell derived based on first-order shear deformation theory (FSDT). The Galerkin method is used to discriminate the motion equations and the equations are converted to the form of the ordinary differential equations in terms of time. The perturbation method is employed to find the relation between nonlinear frequency and the amplitude of vibration. The main objective of this research is to determine the nonlinear frequencies and nonlinear vibration control by using sensor and actuator layers. The effects of geometrical parameters, power law index of core, sensor and actuator layers, angular velocity and scale transformation parameter on nonlinear frequency-amplitude response diagram and dynamic stability of sandwich cylindrical shell are investigated. The results of this research can be used to design and vibration control of rotating systems in various industries such as aircraft, biomechanics and automobile manufacturing.

Thermal buckling response of functionally graded sandwich plates with clamped boundary conditions

  • Abdelhak, Zohra;Hadji, Lazreg;Daouadji, T. Hassaine;Adda Bedia, E.A.
    • Smart Structures and Systems
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    • v.18 no.2
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    • pp.267-291
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    • 2016
  • In this research work, an exact analytical solution for thermal buckling analysis of functionally graded material (FGM) sandwich plates with clamped boundary condition subjected to uniform, linear, and non-linear temperature rises across the thickness direction is developed. Unlike any other theory, the number of unknown functions involved is only four, as against five in case of other shear deformation theories. The theory accounts for parabolic distribution of the transverse shear strains, and satisfies the zero traction boundary conditions on the surfaces of the plate without using shear correction factor. A power law distribution is used to describe the variation of volume fraction of material compositions. Equilibrium and stability equations are derived based on the present refined theory. The non-linear governing equations are solved for plates subjected to simply supported and clamped boundary conditions. The thermal loads are assumed to be uniform, linear and non-linear distribution through-the-thickness. The effects of aspect and thickness ratios, gradient index, on the critical buckling are all discussed.

A novel higher order shear deformation theory based on the neutral surface concept of FGM plate under transverse load

  • Daouadji, Tahar Hassaine;Benferhat, Rabia;Adim, Belkacem
    • Advances in materials Research
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    • v.5 no.2
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    • pp.107-120
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    • 2016
  • The static analysis of the simply supported functionally graded plate under transverse load by using a new sinusoidal shear deformation theory based on the neutral surface concept is investigated analytically in the present paper. No transversal shear correction factors are needed because a correct representation of the transversal shearing strain is given. The mechanical properties of the FGM plate are assumed to vary continuously through the thickness according to a power law formulation except Poisson's ratio, which is kept constant. The equilibrium and stability equations are derived by employing the principle of virtual work. Results are provided for thick to thin plates and for different values of the gradient index k, which subjected to sinusoidal or uniformly distributed lateral loads. The accuracy of the present results is verified by comparing it with finite element solution. From the obtained results, it can be concluded that the proposed theory is accurate and efficient in predicting the displacements and stresses of functionally graded plates.

Physical Properties of Acetylated Sweet Potato Starches as Affected by Degree of Substitution (치환도가 초산 고구마전분의 물리적 특성에 미치는 영향)

  • Yoo, Byoung-Seung;Lee, Hye-Lin
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.40 no.7
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    • pp.1048-1052
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    • 2011
  • This study examined the flow properties, paste clarity, freeze-thaw stability and gel strength of acetylated sweet potato starch (ASPS) pastes and gels as a function of degree of substitution (DS). ASPS showed high shear-thinning flow behaviors with high Casson yield stress ($\sigma_{oc}$). Consistency index (K), apparent viscosity ($\eta_{a,100}$) and $\sigma_{oc}$ values of ASPS increased with an increase in DS. In the temperature range of $25{\sim}70^{\circ}C$, ASPS followed an Arrhenius temperature relationship. The activation energies (Ea=13.2~14.3 kJ/mol) of the ASPS samples were much lower than that (18.1 kJ/mol) of the native sweet potato starch (SPS). ASPS gels showed better freeze-thaw stability with a significant decrease in syneresis (%) compared to SPS gel. The gel strength values of ASPS were much lower than that of SPS, and significantly decreased with an increase in DS. The clarity of native SPS paste increased after acetylation.

The Flow Properties and Stability of O/W Emulsion Composed of Various Mixed Nonionic Surfactants 1. The Phase Behavior and Flow Properties of O/W Emulsion Prepared with the Inversion Emulsification Method (혼합비이온계면활성제의 조성에 따른 O/W 에멀젼의 유동특성 및 안정성 1. 반전유화법을 이용한 O/W 에멀젼의 상거동 및 유동특성)

  • Lee, Ho-Sik;Kim, Jum-Sik
    • Applied Chemistry for Engineering
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    • v.4 no.1
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    • pp.196-203
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    • 1993
  • Emulsions were prepared with the inversion emulsification method which adopted the agent-in-oil method-dissolving the mixed surfactants composed of the glycerin monostearate, polyoxyethylene(100) monostearate, and polyoxyethylene(20) sorbitan monostearate into mixtures of liquid paraffin and beeswax, and adding the aqueous solution of propylene glycol, gradually-and then their phases and viscosities behaviors in the emulsifying process were investigated. The fine and homogeneous o/w emulsions were formed in the HLB region (HLB 10.1~12.3), showing liquid crystalline phase and white gel phase in the emulsifying process. The phase inversion steps in the emulsifying process appeared as follows, i.e., oil continuous phase${\rightarrow}$liquid crystalline phase${\rightarrow}$white gel phase${\rightarrow}$o/w emulsion. Shear rate-shear stress curves of the prepared emulsions had the yield values which pointed out the existence of inner structure between emulsion particles, and the hysteresis loop which showed that the inner structure wasbroken irreversibly by the shear. The area of hystersis loop, an index of breakdown of inner structure, was increased with the decreasing of the HLB value of emulsifier, Shear time-shear stress curves showed the time dependence of plastic viscosity, and the relaxation time in time thinning behavior(${\lambda}$) indicated that the stability of emulsions prepared with the inversion emulsification method was decreased with the increasing of HLB values of emulsifier and was higher than that of emulsions prepared by homomixer.

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A new and simple HSDT for thermal stability analysis of FG sandwich plates

  • Menasria, Abderrahmane;Bouhadra, Abdelhakim;Tounsi, Abdelouahed;Bousahla, Abdelmoumen Anis;Mahmoud, S.R.
    • Steel and Composite Structures
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    • v.25 no.2
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    • pp.157-175
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    • 2017
  • The novelty of this work is the use of a new displacement field that includes undetermined integral terms for analyzing thermal buckling response of functionally graded (FG) sandwich plates. The proposed kinematic uses only four variables, which is even less than the first shear deformation theory (FSDT) and the conventional higher shear deformation theories (HSDTs). The theory considers a trigonometric variation of transverse shear stress and verifies the traction free boundary conditions without employing the shear correction factors. Material properties of the sandwich plate faces are considered to be graded in the thickness direction according to a simple power-law variation in terms of the volume fractions of the constituents. The core layer is still homogeneous and made of an isotropic material. The thermal loads are assumed as uniform, linear and non-linear temperature rises within the thickness direction. An energy based variational principle is employed to derive the governing equations as an eigenvalue problem. The validation of the present work is checked by comparing the obtained results the available ones in the literature. The influences of aspect and thickness ratios, material index, loading type, and sandwich plate type on the critical buckling are all discussed.

Design and Theoretic Analysis of 3D Tactile Sensor (3D 촉각 센서의 설계와 이론적인 해석)

  • Sim Kwee-Bo;Hwang Han-Kun
    • Journal of the Korean Institute of Intelligent Systems
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    • v.15 no.7
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    • pp.870-874
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    • 2005
  • This paper presents capacitive tactile sensor that can detect normal and shear forces. This tactile sensor consists of index plate, sensing plate, and elastic dielectric layer. The calculated sensing character is based on the changes of space between two horizontal plate. Larger overlap areas and narrow space between top and bottom plate guarantees higher sensitivity. Tactile sense information can be calculated from the changes of phase of output signal. The symmetric arrangement of sensing plates makes the manufacturing process easier and guarantees the stability of the structure. In this paper, the sensor structure is designed, the mechanism of the Proposed sensor is theoretically explained, and the simulated result is presented.

Nonlinear thermal vibration of pre/post-buckled two-dimensional FGM tapered microbeams based on a higher order shear deformation theory

  • Hendi, Asmaa A.;Eltaher, Mohamed A.;Mohamed, Salwa A.;Attia, Mohamed A.;Abdalla, A.W.
    • Steel and Composite Structures
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    • v.41 no.6
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    • pp.787-803
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    • 2021
  • The size-dependent nonlinear thermomechanical vibration analysis of pre- and post-buckled tapered two-directional functionally graded (2D-FG) microbeams is presented in this study. In the context of the modified couple stress theory, the formulations are derived based on the parabolic shear deformation beam theory and von Karman nonlinear strains. Different thermomechanical material properties are assumed to be temperature-dependent and smoothly vary in both length and thickness directions using the power law and the physical neutral axis concept is employed. The nonlinear governing equations are derived using the Hamilton principle and the resulting variable coefficient equations of motion are solved using the differential quadrature method (DQM) and iterative Newton's method for clamped-clamped and simply supported boundary conditions. Comparison studies are presented to validate the derived model and solution procedure. The impacts of induced thermal moments, temperature power index, two gradient indices, nonuniform cross-section, and microstructure length scale parameter on the frequency-temperature configurations are explored for both clamped and simply supported microbeams.