Yazar "Sofiyev A.H." seçeneğine göre listele
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Öğe Analytical solution of stability and vibration problem of clamped cylindrical shells containing functionally graded layers within shear deformation theory(Elsevier, 2022) Sofiyev A.H.; Fantuzzi N.The aim of the study is to present a new approach to the analytical solution of the vibration and stability problem of clamped sandwich cylindrical shells (SCSs) covered by functionally graded (FG) coatings under an axial compressive load in the framework of shear deformation theory (ST). After modeling the micro and macro mechanical properties of FG coated SCSs with various configurations, the constitutive relations and basic equations are derived depending on the stress, deflection and two angles of rotation functions using modified Donnell type theory. An attempt is made to analytically solve the fundamental differential equations for SCSs covered by FG coatings using novel approximation functions satisfying the clamped boundary conditions. Three different shear stress functions (SSFs) such as parabolic shear stress function (Par-SSF), cosine-hyperbolic shear stress function (Cos-Hyp-SSF) and uniform shear stress function (USSF) are used in the analysis. After confirming the accuracy of the obtained results, the influences of coating profiles, volume fractions and layer arrangement variations on the critical parameters for three different transverse shear stress functions are investigated in detail.Öğe Buckling analysis of shear deformable composite conical shells reinforced by CNTs subjected to combined loading on the two-parameter elastic foundation(China Ordnance Industry Corporation, 2022) Sofiyev A.H.; Kuruoglu N.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 two-parameter 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.Öğe Buckling behavior of multilayer cylindrical shells composed of functionally graded nanocomposite layers under lateral pressure in thermal environments(Elsevier, 2023) Avey M; Fantuzzi N.; Sofiyev A.H.; Zamanov A.D.; Hasanov Y.N.; Schnack E.In this study, the stability behavior of multilayer cylindrical shells made of functionally graded nanocomposite layers (FG-NCLs) subjected to the lateral pressure in thermal environments is investigated. It is postulated that nanocomposite layers forming layered cylindrical shells are made of single-walled carbon nanotube (SWCNT)- reinforced polymers that have four types of profiles based on the uniform and linear distributions of mechanical properties. The material properties of SWCNTs are assumed to be dependent on location as well as temperature and are obtained from molecular dynamics simulations. The governing equations are derived as partial differ ential equations within shear deformation theory (SDT) and solved in a closed form, using the Galerkin pro cedure, to determine the lateral critical pressure (LCP) in thermal environments. The numerical representations relate to the buckling behavior of multilayer cylindrical shells made of functionally graded nanocomposite layers under the uniform lateral pressure for different CNT patterns and temperatures within SDT and Kirchhoff-Love theory (KLT).Öğe Generalized Heat Equation with the Caputo–Fabrizio Fractional Derivative for a Nonsimple Thermoelastic Cylinder with Temperature-Dependent Properties(Pleiades Publishing, 2023) Abouelregal A.E.; Sofiyev A.H.; Sedighi H.M.; Fahmy M.A.Abstract: In the current paper, a generalized thermoelastic model with two-temperature characteristics, including a heat transfer equation with fractional derivatives and phase lags, is proposed. The Caputo–Fabrizio fractional differential operator is used to derive a new model and to solve the singular kernel problem of conventional fractional models. The suggested model is then exploited to investigate responses of an isotropic cylinder with variable properties and boundaries constantly exposed to thermal or mechanical loads. The elastic cylinder is also assumed to be permeated with a constant magnetic field and a continuous heat source. The governing partial differential equations are formulated in dimensionless forms and then solved by the Laplace transform technique together with its numerical inversions. The effects of the heat source intensity and fractional order parameter on the thermal and mechanical responses are addressed in detail. To verify the integrity of the obtained results, some comparative studies are conducted by considering different thermoelastic models.Öğe Influences of elastic foundations and thermal environments on the thermoelastic buckling of nanocomposite truncated conical shells(Springer, 2022) Avey, Mahmure; Sofiyev A.H.; Kuruoglu N.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).Öğe Modeling of Functionally Graded Coatings and Applications in Sandwich Structures(International Astronautical Federation, IAF, 2023) Sofiyev A.H.The most important application areas of sandwich composites are in industries that require advanced technology. The biggest disadvantage of sandwich structures made of traditional composites is that delamination cannot be prevented due to different material properties on contact surfaces of core and coatings. To prevent such disadvantages in sandwich construction elements, functionally graded materials (FGMs) have been used in recent years. FGMs belong to new class of heterogeneous materials consisting of mixture of ceramics and metals, characterized by smooth and continuous change of mechanical properties. Due to the excellent properties of FGMs, they are applied in spacecraft, rocket technology, nuclear reactors etc. In this study, after modeling the micro and macro mechanical properties of sandwich shells covered by functionally graded (FG) coatings under external pressure, the stability problem is formulated and solution method is presented as example within shear deformation theories.Öğe A new approach to solution of stability problem of heterogeneous orthotropic truncated cones with clamped edges within shear deformation theory(Elsevier, 2022) Sofiyev A.H.In this study, the stability problem of heterogeneous orthotropic (HTO) truncated conical shells with clamped edges subjected to external pressures (lateral and hydrostatic) within shear deformation theory (ST) is solved using a new approach. After the mathematical and visual design of HTO-truncated conical shells, modified Donnell-type governing equations including transverse shear stresses are derived for them. Stability equations are solved analytically for the first time in this study by constructing new approximation functions depending on an unknown parameter for stress, deflection and two angles of rotation functions under clamped boundary conditions. In addition, the unknown parameter contained in the analytical formulas for the clamped HTOtruncated conical shells within ST is found from the minimum conditions of the critical external pressures. After confirming the accuracy of the results, the influences of shear stresses, orthotropy, heterogeneity and conical shell characteristics on critical lateral and hydrostatic pressures are examined in detail in the presence of clamped boundary conditions.Öğe Nonlinear forced response of doubly-curved laminated panels composed of cnt patterned layers within first order shear deformation theory(Elsevier, 2023) Sofiyev A.H.In this study, the solution of the nonlinear forced vibration (NFV) problem of double curvature panels consisting of inhomogeneous (INH) nanocomposite (NC) layers is discussed within first order shear deformation theory (FSDT), taking into account the viscous damping effect. First, the mechanical properties of laminated double curvature panels composed of carbon nanotube patterned layers are modeled mathematically. Then, based on FSDT with a von K´ arman-type ´ nonlinearity derived the nonlinear basic relationships and partial differential equations (PDEs). The expression for the NFV frequency of multilayer panels made of inhomogeneous nano composite layers (INHNCLs) is obtained within FSDT, using the multi-scale method to the nonlinear PDEs for the first time. Finally, the influences of the external excitation, nonlinearity, transverse shear strains, number and arrangement of layers and CNT-models on the forced vibration frequencies are studied in detail.Öğe On the primary resonance of non-homogeneous orthotropic structures with viscous damping within shear deformation theory(Elsevier Ltd, 2022) Sofiyev A.H.; Turan F.; Kuruoğlu N.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.Öğe ON THE TORSIONAL BUCKLING MOMENT OF CYLINDRICAL SHELLS CONSISTING OF FUNCTIONALLY GRADED MATERIALS RESTING ON THE PASTERNAK-TYPE SOIL(Oil Gas Scientific Research Project Institute, 2022) Sofiyev A.H.; Kadioglu F.; Khalilov I.A.; Sedighi H.M.; Vergul T.; Yenialp R.In this study, the buckling analysis of cylindrical shells made of functionally graded materials (FGMs) under the torsional moment resting on the Pasternak-type soil is performed. After establishing the linear constitutive relations of FGM cylindrical shells within the framework of the modified Donnell type shell theory, the governing equations of FGM cylindrical shells under the torsional moment are derived considering the influence of Pasternak-type soil. Analytical formula for the torsional moment is obtained by choosing the approximation functions that satisfies the boundary conditions in an integral sense. From the obtained formula, the formulas for the critical torsional moment in the presence of Winkler soil and absence of soils are obtained as a special case. Variations of critical torsional moment for different soil coefficients, volume fraction ratio and shell characteristics are investigated in detail.Öğe Thermal Analysis of a Rotating Micropolar Medium Using a Two-Temperature Micropolar Thermoelastic Model with Higher-Order Time Derivatives(Pleiades Publishing, 2023) Abouelregal A.E.; Alanazi R.; Sofiyev A.H.; Sedighi H.M.In this work, the propagation of planar waves in a homogeneous micropolar thermoelastic medium is studied while the entire body rotates with a uniform angular speed. The coordinate system of the rotating medium is assumed to be stationary, and therefore the kinematic equations have two additional terms, na mely, the gravitational and the Coriolis accelerations. The problem is addressed based on the two-tempera ture thermoelastic model with higher-order time derivatives and dual-phase lag, which can explain the effect of microscopic features in nonsimple materials. With certain boundary conditions and the normal mode approach, the variations in temperature, displacement, microrotation, and thermal stresses induced by heating are derived. In the absence of rotation and two-temperature factor, comparison is made with the results of classical thermoelastic models.Öğe Thermoelastic stability of CNT patterned conical shells under thermal loading in the framework of shear deformation theory(Taylor and Francis Ltd., 2022) Avey M.; Fantuzzi N.; Sofiyev A.H.This study presents the thermoelastic stability of carbon nanotube (CNT) patterned composite conical shells in the framework of shear deformation theory (ST). The study includes two different boundary value problems. As the material properties are independent of temperature, the truncated conical shell is assumed to be under thermal load, and when the material properties are temperature dependent, the conical shell is assumed to be under axial compressive load. The modified Donnell-type shell theory is used to derive the basic equations for CNT patterned truncated conical shells. The Galerkin method is applied to the basic equations to find the critical temperature and critical axial load expressions of CNT patterned composite truncated conical shells in the framework of ST. The effect of changes in CNT patterns, volume fraction, radius-to-thickness and length-to-thickness ratios, as well as the half-peak angle on critical parameters within the ST, are estimated by comparison with classical shell theory (CT).Öğe Vibration of laminated functionally graded nanocomposite structures considering the transverse shear stresses and rotary inertia(Elsevier Ltd, 2022) Avey M.; Fantuzzi N.; Sofiyev A.H.The aim of this study is to determine the fundamental frequencies of laminated double-curved nanocomposite structures considering transverse shear stresses (TSSs) and rotary inertia (RI). The basic equations of laminated double-curved structures composed of CNT patterned layers based on the Donnell type shell theory are derived within TSSs and considering RI. By applying the Galerkin technique, the fundamental equations are transformed into frequency-dependent sixth-order algebraic equations, and this equation is solved numerically to find the fundamental frequency for laminated double curved structures consisting of CNT patterned layers considering TSSs and RI. In addition, when the rotary inertia is neglected, analytical expressions for frequencies are obtained in the framework of shear deformation theory (ST) and classical theory (CT). Finally, the influences of the volume fraction, CNT patterns, array of nanocomposite layers, TSSs and RI on the fundamental frequency are examined.
