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RISS 인기검색어
- 검색키워드
- 저자 : R. D. Firouz-Abadi (검색결과 3 건)
- 무료
- 기관 내 무료
- 유료
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R. D. Firouz-Abadi,M. M. Fotouhi,M. R. Permoon,H. Haddadpour 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.2
The small-scale effect on the natural frequencies and buckling of pressurized nanotubes is investigated in this study. Based on the firstorder shear deformable shell theory, the nonlocal theory of elasticity is used to account for the small-scale effect and the governing equations of motion are obtained. Applying modal analysis technique and based on Galerkin's method a procedure is proposed to obtain natural frequencies of vibrations. For the case of nanotubes with simply supported boundary conditions, explicit expressions are obtained which establish the dependency of the natural frequencies and buckling loads of the nanotube on the small-scale parameter and natural frequencies obtained by local continuum mechanics. The obtained solutions generalize the results of nano-bar and -beam models and are verified by the literature. Based on several numerical studies some conclusions are drawn about the small-scale effect on the natural frequencies and buckling pressure of the nanotubes.
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A. R. Askarian,H. Abtahi,R. D. Firouz-Abadi,H. Haddadpour,E. H. Dowell 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.7
In the present study, dynamic stability of a viscoelastic cantilevered pipe conveying fluid which fluctuates harmonically about a mean flow velocity is considered; while the fluid flow is exhausted through an inclined end nozzle. The Euler-Bernoulli beam theory is used to model the pipe and fluid flow effects are modelled as a distributed load along the pipe which contains the inertia, Coriolis, centrifugal and induced pulsating fluid flow forces. Moreover, the end nozzle is modelled as a follower force which couples bending vibrations with torsional ones. The extended Hamilton's principle and the Galerkin method are used to derive the bending-torsional equations of motion. The coupled equations of motion are solved using Runge-Kutta algorithm with adaptive time step and the instability boundary is determined using the Floquet theory. Numerical results present effects of some parameters such as fluid flow fluctuation, bending-to-torsional rigidity ratio, nozzle inclination angle, nozzle mass and viscoelastic material on the stability margin of the system and some conclusions are drawn.
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Shell-like instability of large diameter single-walled carbon nanotubes conveying fluid
H. R. Ali-Akbari,R. D. Firouz-Abadi,H. Haddadpour,M. A. Noorian 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.11
The instability of large diameter single-walled carbon nanotubes (SWCNTs) conveying fluid is investigated based on the molecular mechanics. Using the modal expansion for structural displacements, the governing equations of coupled fluid-structural dynamics of SWCNTs are derived. The natural frequencies and mode shape of the SWCNTs are obtained based on the molecular structural mechanics to account for the effect of chirality and discrete nature of SWCNTs. The results show that the vibrational behavior of large diameter SWCNTs conveying fluid is size dependent, but the effect of chirality is negligible. The obtained results are compared with the equivalent continuum-based model in the literature and in some cases remarkable deviations between the results are observed. Accordingly,proper values for the equivalent wall thickness and Young’s modulus of SWCNTs are proposed to adopt the results of continuum-based model with the molecular mechanics predictions.
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