Yazar "Sofiyev, Abdullah H." seçeneğine göre listele

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    An approach to the solution of nonlinear forced vibration problem of structural systems reinforced with advanced materials in the presence of viscous damping
    (ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD, 24-28 OVAL RD, LONDON NW1 7DX, ENGLAND, 2021) Sofiyev, Abdullah H.; Avey, Mahmure; Kuruoğlu, Nuri
    In this study, the nonlinear forced vibration of composite structural systems such as plates, panels and shells reinforced with advanced materials in the presence of linear viscous damping is investigated. Hamilton principle and von K´ arman-type ´ nonlinear theory are used to obtain the theoretical model of double-curved shells reinforced by carbon nanotubes (CNTs). The nonlinear partial differential equations are reduced to ordinary differential equations using Galerkin method. By using the multiscale method, the frequency-amplitude relation and nonlinear forced vibration frequency of structural systems are obtained for the first time. Since double-curved shells can be transformed into other structural systems such as spherical and hyperbolicparaboloid shells, rectangular plate and cylindrical panel in special cases, the expressions for nonlinear frequencies can also be used for them. In additional, the backbone curve and the nonlinear frequency/linear frequency ratio are determined as a function of the amplitude in primary resonance for the first time. The results are verified by comparing the reliability and accuracy of the proposed formulation with those in the literature. Finally, a systematic study is aimed at controlling the influence of nonlinearity and types of distribution of CNTs on the frequencies and their quantitative and qualitative variation in the presence of external excitation and viscous damping.
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    Buckling analysis of shear deformable composite conical shells reinforced by CNTs subjected to combined loading on the two-parameter elastic foundation
    (KEAI PUBLISHING LTD, 16 DONGHUANGCHENGGEN NORTH ST, BEIJING, DONGCHENG DISTRICT 100717, PEOPLES R CHINA, 2022) Sofiyev, Abdullah H.; Kuruoğlu, Nuri
    The main objective of this study is to investigate the buckling analysis of CCSs reinforced by CNTs subjected to combined loading of hydrostatic pressure and axial compression resting on the twoparameter elastic foundation (T-P-EF). It is one of the first attempts to derive the governing equations of the CCSs reinforced with CNTs, based on a generalized first-order shear deformation shell theory (FSDST) which includes shell-foundation interaction. By adopting the extended mixing rule, the effective material properties of CCSs reinforced by CNTs with linear distributions are approximated by introducing some efficiency parameters. Three carbon nanotube distribution in the matrix, i.e. uniform distribution (U) and V and X-types linear distribution are taken into account. The stability equations are solved by using the Galerkin procedure to determine the combined buckling loads (CBLs) of the structure selected here. The numerical illustrations cover CBLs characteristics of CCSs reinforced by CNTs in the presence of the T-P-EF. Finally, a parametric study is carried out to study the influences of the foundation parameters, the volume fraction of carbon nanotubes and the types of reinforcement on the CBLs.
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    Buckling Behavior of FG-CNT Reinforced Composite Conical Shells Subjected to a Combined Loading
    (MDPI, ST ALBAN-ANLAGE 66, CH-4052 BASEL, SWITZERLAND, 2020) Sofiyev, Abdullah H.; Tornabene, Francesco; Dimitri, Rossana; Kuruoğlu, Nuri
    The buckling behavior of functionally graded carbon nanotube reinforced composite conical shells (FG-CNTRC-CSs) is here investigated by means of the first order shear deformation theory (FSDT), under a combined axial/lateral or axial/hydrostatic loading condition. Two types of CNTRC-CSs are considered herein, namely, a uniform distribution or a functionally graded (FG) distribution of reinforcement, with a linear variation of the mechanical properties throughout the thickness. The basic equations of the problem are here derived and solved in a closed form, using the Galerkin procedure, to determine the critical combined loading for the selected structure. First, we check for the reliability of the proposed formulation and the accuracy of results with respect to the available literature. It follows a systematic investigation aimed at checking the sensitivity of the structural response to the geometry, the proportional loading parameter, the type of distribution, and volume fraction of CNTs.
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    Domains of Dynamic Instability of FGM Conical Shells Under Time Dependent Periodic Loads
    (Springer Nature, 2016-02) Sofiyev, Abdullah H.; Kuruoğlu, Nuri
    On the basis of the dynamic version of linear Donnell type equations and with deformations before instability taken into account, the dynamic instability of simply supported, functionally graded (FG) truncated conical shells under static and time dependent periodic axial loads is analyzed. Appling Galerkin’s method, the partial differential equations are reduced into a Mathieu-type differential equation describing the dynamic instability behavior of the FG conical shell. The domains of principal instability are determined by using Bolotin’s method. Validation of numerical results was done with those available from previous researches. The influences of various parameters like static and dynamic load factors, volume fraction index, FG profiles and shell characteristics on the domains of dynamic instability of conical shell were investigated.
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    Dynamic behavior of FGM viscoelastic plates resting on elastic foundations
    (SPRINGER WIEN, SACHSENPLATZ 4-6, PO BOX 89, A-1201 WIEN, AUSTRIA, 2020) Sofiyev, Abdullah H.; Zerin, Zihni; Kuruoğlu, Nuri
    The free vibration (FV) and dynamic stability (DS) analysis is presented for functionally graded viscoelastic plates (FGVPs) under compressive load and resting on elastic foundations (EFs). Winkler and Pasternak elastic foundation models are used as elastic foundations. The basic equations of FGVPs interacting with EFs are derived using the concepts of Boltzmann and Volterra. An analytical method for studying the DS and FV of FGVPs interacting with EFs is developed using the integro-differential equations. To solve the current problem, the Galerkin and the Laplace method are used. A technique for the analysis of DS and FV of FGVPs on the EFs is developed. To confirm the proposed formulation, the results are compared with other available solutions. Finally, the influences of EFs, volume fractions and rheological constants on the critical times and frequencies depending on the geometrical characteristics and loading parameters are examined.
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    Influence of elastic foundations and carbon nanotube reinforcement on the hydrostatic buckling pressure of truncated conical shells
    (SHANGHAI UNIV, 149 YANCHANG RD, SHANGHAI 200072, PEOPLES R CHINA, 2020) Sofiyev, Abdullah H.; Pirmamedov, I. T.; Kuruoğlu, Nuri
    In this study, the effects of elastic foundations (EFs) and carbon nanotube (CNT) reinforcement on the hydrostatic buckling pressure (HBP) of truncated conical shells (TCSs) are investigated. The first order shear deformation theory (FOSDT) is generalized to the buckling problem of TCSs reinforced with CNTs resting on the EFs for the first time. The material properties of composite TCSs reinforced with CNTs are graded linearly according to the thickness coordinate. The Winkler elastic foundation (W-EF) and Pasternak elastic foundation (P-EF) are considered as the EF. The basic relations and equations of TCSs reinforced with CNTs on the EFs are obtained in the framework of the FOSDT and solved using the Galerkin method. One of the innovations in this study is to obtain a closed-form solution for the HBP of TCSs reinforced with CNTs on the EFs. Finally, the effects of the EFs and various types CNT reinforcements on the HBP are investigated simultaneously. The obtained results are compared with the results in the literature, and the accuracy of results is confirmed.
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    Influences of elastic foundations and shear deformations on the buckling behavior of functionally graded material truncated conical shells under axial compression
    (Taylor & Francis Inc, 2017) Sofiyev, Abdullah H.; Kadioglu, Fethi; Kuruoglu, Nuri
    This article presents an investigation on the buckling of functionally graded (FG) truncated conical shells under an axial load resting on elastic foundations within the shear deformation theory (SDT). The governing equations are solved using the Galerkin method, and the closed-form solution of the axial buckling load for FG conical shells on elastic foundations within the SDT is obtained. Various numerical examples are presented and discussed to verify the accuracy of the closed-form solution in predicting dimensionless buckling loads for FG conical shells on the Winkler-Pasternak elastic foundations within the SDT.
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    Influences of elastic foundations and thermal environments on the thermoelastic buckling of nanocomposite truncated conical shells
    (SPRINGER WIEN, SACHSENPLATZ 4-6, PO BOX 89, A-1201 WIEN, AUSTRIA, 2022) Avey, Mahmure; Sofiyev, Abdullah H.; Kuruoğlu, Nuri
    In this study, the combined effects of two-parameter elastic foundation and thermal environment on the buckling behaviors of carbon nanotube (CNT) patterned composite conical shells in the framework of the shear deformation theory (SDT) are investigated. It is assumed that the nanocomposite conical shell is freely supported at its ends and that the material properties are temperature dependent. The derivation of fundamental equations of CNT-patterned truncated conical shells on elastic foundations is based on the Donnell shell theory. The Galerkin method is applied to the basic equations to find the expressions for the critical temperature (CT) and axial buckling loads of CNT-patterned truncated conical shells on elastic foundations and in thermal environments. In the presence of elastic foundations and thermal environments, it is estimated how the effects of CNT patterns, the volume fractions, and the characteristics of conical shells on the buckling load within SDT change by comparing them with the classical shell theory (CST).
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    Influences of elastic foundations on the nonlinear free vibration of composite shells containing carbon nanotubes within shear deformation theory
    (ELSEVIER SCI LTD, THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND, 2022) Avey, Mahmure; Fantuzzi, Nicholas; Sofiyev, Abdullah H.; Kuruoğlu, Nuri
    In this work, the solution of nonlinear free vibration problem of composite shells structures containing carbon nanotubes (CNTs) resting on elastic soils within shear deformation theory (ST) is presented. After modeling the mechanical properties of nanocomposite shell structures containing CNTs and elastic soils, the basic relations, and governing equations of double curved shell structures within the ST are established considering the geometric nonlinearity. The frequencies of nonlinear and linear free vibrations and their ratios for inhomogeneous nanocomposite structures on the soils within the ST are obtained using perturbation method for the first time. After checking the methodology of the research, the effects of soils, nonlinearity, shear strains and patterns of CNT on the frequency-amplitude dependence of nanocomposite shell structures for various geometric parameters are carried out.
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    Influences of material gradient and nonlinearity on the forced vibration of orthotropic shell structures
    (ELSEVIER SCI LTD, THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND, 2021) Sofiyev, Abdullah H.; Turan, Ferruh; Kuruoğlu, Nuri
    In this study, the influences of material gradient and nonlinearity on the forced vibration of orthotropic shell structures under external excitations are investigated for first time. The mathematical model of inhomogeneous orthotropic double?curved shallow shells is built using the Hamilton principle and von Karman?type nonlinearity. The basic equations are reduced to nonlinear ordinary differential equations using the Galerkin procedure. Using the multiscale method, the frequency?amplitude relations of double?curved shallow shells and the nonlinear frequency response of forced vibrations are obtained for first time. The reliability of the obtained expressions is checked by comparison with the literature data. In numerical analysis, the influence of inhomogeneity, orthotropy, nonlinearity, and the external excitation parameter on the frequency of forced vibrations is investigated in detail by performing unique numerical calculations taking into account various profiles of inhomogeneous orthotropic shallow spherical and hyperbolic paraboloidal (or hypar) shells.
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    Modeling and Solution of Large Amplitude Vibration Problem of Construction Elements Made of Nanocomposites Using Shear Deformation Theory
    (MDPI, ST ALBAN-ANLAGE 66, CH-4052 BASEL, SWITZERLAND, 2021) Deniz, Ali; Fantuzzi, Nicholas; Sofiyev, Abdullah H.; Kuruoğlu, Nuri
    The main purpose of the study is to investigate the vibration behaviors of carbon nanotube (CNT) patterned double-curved construction elements using the shear deformation theory (SDT). After the visual and mathematical models of CNT patterned double-curved construction elements are created, the large amplitude stress–strain relationships and basic dynamic equations are derived using the first order shear deformation theory (FSDT). Then, using the Galerkin method, the problem is reduced to the nonlinear vibration of nanocomposite continuous systems with quadratic and cubic nonlinearities. Applying the Grigolyuk method to the obtained nonlinear differential equation, largeamplitude frequency-amplitude dependence is obtained. The expressions for nonlinear frequencies of homogenous and inhomogeneous nanocomposite construction members such as plates, panels, spherical and hyperbolic-paraboloid (hypar) shells in the framework of FSDT are found in special cases. The accuracy of the results of the current study has been confirmed by comparing them with the reliable results reported in the literature. Original analyses are carried out to examine the effects of nonlinearity, CNT patterns and volume fraction changes on frequencies in the framework of shear deformation and classical shell theories.
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    Nonlinear vibration of multilayer shell-type structural elements with double curvature consisting of CNT patterned layers within different theories
    (ELSEVIER SCI LTD, THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND, 2021) Avey, Mahmure; Fantuzzi, Nicholas; Sofiyev, Abdullah H.; Kuruoğlu, Nuri
    In this article, the nonlinear vibration of moderately thick multilayer shell?type structural elements with double curvature consisting of carbon nanotube (CNT) patterned layers is investigated within different shell theories. The first order shear deformation theory has been generalized on the motion for moderately thick multilayer shell?type structural elements with double curvature consisting of CNT patterned layers for the first time. Then, by applying Galerkin and semi?inverse perturbation methods to motion equations, and the frequency? amplitude relationship is obtained. From these formulas, the expressions for nonlinear frequencies of multilayer spherical and hyperbolic?paraboloid shells, rectangular plate and cylindrical panels patterned by CNTs within shear deformation and classical shell theories are obtained in special cases. The reliability of obtained results is verified by comparison with other results reported in the literature. The effects of transverse shear strains, volume fraction, sequence and number of nanocomposite layers on nonlinear frequency are discussed in detail.
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    On the free vibration of orthotropic and inhomogeneous with spatial coordinates plates resting on the inhomogeneous viscoelastic foundation
    (TAYLOR & FRANCIS INC, 530 WALNUT STREET, STE 850, PHILADELPHIA, PA 19106, 2019) Haciyev, V. C.; Sofiyev, Abdullah H.; Kuruoğlu, Nuri
    The paper developed the closed-form solution for the free vibration problem of inhomogeneous orthotropic rectangular plates (IHORPs) resting on the inhomogeneous viscoelastic foundation (IHVEF). The Young’s moduli and density of the orthotropic plate vary continuously with respect to three spatial coordinates, while the characteristics of the viscoelastic foundation vary depending on the in-plane coordinates. The relevant motion equation is obtained using the classical plate theory (CPT) and solved using method of separation of variables. The influences of inhomogeneity of orthotropic materials, inhomogeneity of viscoelastic and elastic foundations on the non-dimensional frequencies (NDFs) of plates are studied in detail.
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    On the primary resonance of non-homogeneous orthotropic structures with viscous damping within shear deformation theory
    (ELSEVIER SCI LTD, THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND, 2022) Sofiyev, Abdullah H.; Turan, Ferruh; Kuruoğlu, Nuri
    This study is one of the first attempts on the nonlinear forced vibration behaviors of nonhomogeneous orthotropic (NHO) structural members with linear viscous damping at primary resonance within the shear deformation theory (SDT). First, mechanical properties of double curved systems consisting of NHO materials are mathematically modeled and nonlinear basic relations are established. Using these relations, nonlinear basic partial differential equations are derived and reduced to ordinary differential equations with second and third order nonlinearities by Galerkin procedure. Multiple-scales method is used to obtain the nonlinear forced vibration frequency–amplitude dependence of double curved NHO structural members with damping. After testing the correctness of the proposed methodology, the influences of non-homogeneity, damping, transverse shear deformations and anisotropy on nonlinear forced vibration frequencies for various structural members at the primary resonance are investigated and interpreted in detail.
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    Primary resonance of double-curved nanocomposite shells using nonlinear theory and multi-scales method: Modeling and analytical solution
    (PERGAMON-ELSEVIER SCIENCE LTD, THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND, 2021) Avey, Mahmure; Sofiyev, Abdullah H.; Fantuzzi, Nicholas; Kuruoğlu, Nuri
    In this article, the forced vibration of double-curved nanocomposite shells under a time dependent excitation is studied using nonlinear shell theory and multi-scales method in primary resonance. The nanocomposite representative volume element consists of two phases, including carbon nanotube (CNT) and matrix. By generalizing the Ambartsumyan’s first order shear deformation shell theory (FSDT) to the heterogeneous nanocomposite shells, the nonlinear partial differential equations are derived. Then, the problem is reduced to the nonlinear forced vibration of damped nanocomposite shells with quadratic and cubic nonlinearities. For the occurrence of the primary resonance, the damping, nonlinearity, and excitation terms in the disturbance circuit are reduced to the same order. Applying the multi-scales method to nonlinear ordinary differential equation, nonlinear frequency–amplitude dependence in primary resonance is obtained.