• Advances in Computational Design
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• v.5 no.4
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• pp.349-362
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• 2020

Dynamic characteristics of a scale-dependent porous metal foam cylindrical shell under a traveling load have been explored within this article based on a numerical approach. Within the material texture of the metal foams, uniform and non-uniform porosities may be dispersed. Based upon differential quadrature method (DQM) and Laplace transforms, the equations of motion for a shear deformable scale-dependent shell may be solved numerically. Scale-dependent shell modeling has been provided based upon strain gradient elasticity. Solving the equations will give the shell deflection as a function of load speed. Also, it is reported that shell deflection relies on the porosity dispersion and strain gradient influences.

• International Journal of Naval Architecture and Ocean Engineering
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• v.12 no.1
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• pp.680-690
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• 2020

In ocean environment, the sound speed gradient of seawater has an important influence on far field sound propagation. The FEM/BEM is used to decouple the vibroacoustic radiation of the spherical shell, and the Green function of the virtual source chain is adopted for decoupling. For far field radiated Sound Pressure Level (SPL), the Beam Displacement Ray normal Mode (BDRM) is employed. The vibration and near-/far-field radiated SPL of spherical shell is analyzed in shallow sea uniform layer, negative/positive gradient, negative thermocline environment, and deep-sea sound channel. Results show that the vibroacoustic radiation of spherical shell acted at 300Hz can be analogous to dipole. When the radiated field of the spherical shell is dominated by large-grazing-angle waves, it can be analogous to vertically distributed dipole, and the far field radiated SPL is lower; while similar to horizontally distributed dipole if dominated by small-grazing-angle waves, and the far field SPL is high.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.34 no.6
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• pp.454-460
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• 2021

In this work, we synthesized alloy-core InZnP quantum dots, which are more efficient than single-core InP quantum dots, using a solution process method. The effect of synthesis conditions of alloy core on optical properties was investigated. We also investigated the conditions that make up the gradient shell to minimize defects caused by lattice mismatch between the InZnP core and ZnS is 7.7%. The stable synthesis temperature of the InZnP alloy core was 200℃. Quantum dots consisting of three layered ZnSe gradient shell and single layered ZnS exhibited the best optical property. The properties of quantum dots synthesized in 100 ml and in 2,000 ml flasks were almost equal.

• Advances in materials Research
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• v.8 no.3
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• pp.179-196
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• 2019

This paper researches static and dynamic bending behaviors of a crystalline nano-size shell having pores and grains in the framework of strain gradient elasticity. Thus, the nanoshell is made of a multi-phase porous material for which all material properties on dependent on the size of grains. Also, in order to take into account small size effects much accurately, the surface energies related to grains and pores have been considered. In order to take into account all aforementioned factors, a micro-mechanical procedure has been applied for describing material properties of the nanoshell. A numerical trend is implemented to solve the governing equations and derive static and dynamic deflections. It will be proved that the static and dynamic deflections of the crystalline nanoshell rely on pore size, grain size, pore percentage, load location and strain gradient coefficient.

• Structural Engineering and Mechanics
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• v.62 no.5
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• pp.551-565
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• 2017

Based on the strain gradient theory (SGT), vibration analysis of an embedded micro cylindrical shell reinforced with agglomerated carbon nanotubes (CNTs) is investigated. The elastic medium is simulated by the orthotropic Pasternak foundation. The structure is subjected to magnetic field in the axial direction. For obtaining the equivalent material properties of structure and considering agglomeration effects, the Mori-Tanaka model is applied. The motion equations are derived on the basis of Mindlin cylindrical shell theory, energy method and Hamilton's principal. Differential quadrature method (DQM) is proposed to evaluate the frequency of system for different boundary conditions. The effects of different parameters such as CNTs volume percent, agglomeration of CNTs, elastic medium, magnetic field, boundary conditions, length to radius ratio and small scale parameter are shown on the frequency of the structure. The results indicate that the effect of CNTs agglomeration plays an important role in the frequency of system so that considering agglomeration leads to lower frequency. Furthermore, the frequency of structure increases with enhancing the small scale parameter.

• Steel and Composite Structures
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• v.36 no.6
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• pp.631-642
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• 2020

This paper studies nonlinear stability behavior of a nanocrystalline silicon curved nanoshell considering strain gradient size-dependency. Nanocrystallines are composite materials with an interface phase and randomly distributed nano-size grains and pores. Imperfectness of the curved nanoshell has been defined based on an initial deflection. The formulation of nanocrystalline nanoshell has been established by thin shell theory and an analytical approach has been used in order to solve the buckling problem. For accurately describing the size effects related to nano-grains or nano-pores, their surface energies have been included. Nonlinear stability curves of the nanoshell are affected by the size of nano-grain, curvature radius and nano-pore volume fraction. It is found that increasing the nano-pore volume fraction results in lower buckling loads.

• Steel and Composite Structures
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• v.28 no.3
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• pp.381-388
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• 2018

In this paper, forced vibration of micro cylindrical shell reinforced by functionally graded carbon nanotubes (FG-CNTs) is presented. The structure is subjected to transverse harmonic load and modeled by beam model. The size effects are considered based on strain gradient theory containing three small scale parameters. The mixture rule is used for obtaining the effective material properties of the structure. Based on sinusoidal shear deformation theory of beam, energy method and Hamilton's principle, the motion equations are derived. Applying differential quadrature method (DQM) and Newmark method, the frequency curves of the structure are plotted. The effect of different parameters including, CNTs volume percent and distribution type, boundary conditions, size effect and length to thickness ratio on the frequency curves of the structure is studied. Numerical results indicate that the dynamic deflection of the FGX-CNT-reinforced cylindrical is lower with respect to other type of CNT distribution.

• Advances in concrete construction
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• v.16 no.5
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• pp.243-254
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• 2023

Microtubules in the cell are influenced by internal and external stimulation and play an important part in conveying protein substances and in carrying out medications to the intended targets. Waves are produced during these functions and in order to control the biological cell functions, it is important to know the wave velocities of microtubules. Owing to cylindrical shell shaped and mechanically elastic and orthotropic, cylindrical shell model based on gradient elasticity theory has been used. Wave velocities of the protein microtubule are carried out by considering Love's thin shell theory and Navier solution. Also the effect of size parameter and other variables on the results are investigated.

• Smart Structures and Systems
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• v.22 no.5
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• pp.527-546
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• 2018

This article presents an analysis into the nonlinear forced vibration of a micro cylindrical shell reinforced by carbon nanotubes (CNTs) with considering agglomeration effects. The structure is subjected to magnetic field and transverse harmonic mechanical load. Mindlin theory is employed to model the structure and the strain gradient theory (SGT) is also used to capture the size effect. Mori-Tanaka approach is used to estimate the equivalent material properties of the nanocomposite cylindrical shell and consider the CNTs agglomeration effect. The motion equations are derived using Hamilton's principle and the differential quadrature method (DQM) is employed to solve them for obtaining nonlinear frequency response of the cylindrical shells. The effect of different parameters including magnetic field, CNTs volume percent and agglomeration effect, boundary conditions, size effect and length to thickness ratio on the nonlinear forced vibrational characteristic of the of the system is studied. Numerical results indicate that by enhancing the CNTs volume percent, the amplitude of system decreases while considering the CNTs agglomeration effect has an inverse effect.

• Journal of Power System Engineering
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• v.9 no.4
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• pp.220-224
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• 2005

The thermal elasto-plastic analysis for the prediction of welding distortion of a 3 dimensional large-scaled ship structure is a very time-consuming work since the analysis is a nonlinear problem, and a lot of finite elements are needed to simulate the large ship hull block. Generally, 3-D finite elements have been used in the 3-D welding distortion problem to assess precisely the temperature gradient through the thickness direction of the welding plate. As a result of the adoption of 3-D element, degrees of freedom are rapidly increased in the problem to be solved. In this study, to improve the time efficiency of welding thermal elasto-plastic analysis, a layered shell element was proposed to simulate 3-D temperature gradient, and the results were compared with the experiment. The experiments were carried out for the type of bead-on-plate welding, and we found the measured data have a good agreement with the FEA results.