Ömer Civalek | Akdeniz University (original) (raw)

Papers by Ömer Civalek

Applied and Computational Mechanics, 2018

In the present study, the finite element method is developed for the static analysis of nano-beam... more In the present study, the finite element method is developed for the static analysis of nano-beams under the Winkler foundation and the uniform load. The small scale effect along with Eringen's nonlocal elasticity theory is taken into account. The governing equations are derived based on the minimum potential energy principle. Galerkin weighted residual method is used to obtain the finite element equations. The validity and novelty of the results for bending are tested and comparative results are presented. Deflections according to different Winkler foundation parameters and small scale parameters are tabulated and plotted. As it can be seen clearly from figures and tables, for simply-supported boundary conditions, the effect of small scale parameter is very high when the Winkler foundation parameter is smaller. On the other hand, for clamped-clamped boundary conditions, the effect of small scale parameter is higher when the Winkler foundation parameter is high. Although the eff...

Nanomaterials, 2021

This paper presents forced vibration analysis of a simply supported beam made of carbon nanotube-... more This paper presents forced vibration analysis of a simply supported beam made of carbon nanotube-reinforced composite material subjected to a harmonic point load at the midpoint of beam. The composite beam is made of a polymeric matrix and reinforced the single-walled carbon nanotubes with their various distributions. In the beam kinematics, the first-order shear deformation beam theory was used. The governing equations of problem were derived by using the Lagrange procedure. In the solution of the problem, the Ritz method was used, and algebraic polynomials were employed with the trivial functions for the Ritz method. In the solution of the forced vibration problem, the Newmark average acceleration method was applied in the time history. In the numerical examples, the effects of carbon nanotube volume fraction, aspect ratio, and dynamic parameters on the forced vibration response of carbon nanotube-reinforced composite beams are investigated. In addition, some comparison studies we...

International Journal Of Engineering & Applied Sciences, 2015

Aortas are the largest artery in the body and they carry the blood away which is pumped from the ... more Aortas are the largest artery in the body and they carry the blood away which is pumped from the heart. Aorta artery is also the artery which is affected by the highest blood pressure. Its stability has a vital importance to humans and animals. The loss of stability in arteries may lead to arterial tortuosity and kinking. This situation causes to blackouts and serious permanent health problems. In this article, the buckling analysis of aorta artery is investigated by using Euler-Bernoulli beam theory for different boundary conditions. The aorta artery is modeled as a cylindrical tube with different average diameters. Results are presented in figures and table.

Gazi Üniversitesi Mühendislik-Mimarlık Fakültesi Dergisi, 2017

Grafenin serbest titreşim analizi  Grafenin plak olarak modellenmesi  Elastik zemin üzerinde bo... more Grafenin serbest titreşim analizi  Grafenin plak olarak modellenmesi  Elastik zemin üzerinde boyut etkisine bağlı titreşim

Composites Part B: Engineering, 2017

As the parallel to the advancement of technology in nano-sizes, the importance of nanotubes is ri... more As the parallel to the advancement of technology in nano-sizes, the importance of nanotubes is rising every day. The mostly worked and used nanotubes are Carbon Nanotubes (CNT) due to their superior mechanical and electrical properties. On the other hand, the technology always needs better materials with superior mechanical, electrical conductivity and thermal properties. After a couple years of working with Carbon nanotubes, scientists have discovered different types of nanotube such boron nitride and Silicon carbide nanotubes (SiCNTs). In this work, the stability of the Silicon carbide nanotube is investigated in the static buckling case with surface effect. Nonlocal continuum theory is also used in order to see the difference between two higher-order elasticity theories. The stability of nanotubes has an important role since it is used in high-tech equipment. Buckling behavior of SiCNTs is discussed by using the continuum model based on the Euler-Bernoulli beam theory for different boundary conditions in conjunctions with the surface effect and nonlocal elasticity theory. The harmonic differential quadrature method (HDQ) is used for numerical simulations. Some parametric values for critical buckling loads have been obtained with different geometrical quantities of SiCNTs. The size effects on results have been also investigated by the surface elasticity and Eringen's nonlocal elasticity parameters.

International Journal of Computational Methods, 2012

This paper is concerned with the bending analysis of single-walled carbon nanotubes (CNT) based o... more This paper is concerned with the bending analysis of single-walled carbon nanotubes (CNT) based on modified couple stress and strain gradient elasticity theories and Euler–Bernoulli beam theory. The size effect is taken into consideration using the modified couple stress and strain gradient elasticity theories. The governing equations and boundary conditions are derived using the variational approach. Deflections of CNT are obtained and presented in graphical form. Results are presented to show the effect of small-scale effect on bending of CNT. It is the first time in the literature, analytical expression and their solutions for the bending analysis based on strain gradient elasticity and couple stress theories are given for CNT under uniformly distributed load and concentrated end load.

Advances in Engineering Software, 2009

9. Akgöz, B., Strain gradient elasticity and couple stress theories for buckling and vibration an... more 9. Akgöz, B., Strain gradient elasticity and couple stress theories for buckling and vibration analysis of micro-scaled plates and beams, Ph.D. Thesis. 10. Erdinç MC., Mechanical analysis of graphene sheets in biomedical applications, M.Sc.Thesis. 11. Baltacıoğlu, AK., Free vibration analysis CNT-reinforced and FGM plates and shells, Ph.D. Thesis. 12. Çakirtaş, S., Bending and vibration of single-layer graphene sheets on elastic foundation via nonlocal elasticity, 2015. 13. Mercan K., Size dependent buckling analysis of aorta artery using nonlocal elasticity theory and surface elasticity theory and its finite element model, M.Sc. Thesis, 2017. 14. Solmaz, S., Optimal design based on nonlocal elasticity of static loaded nanobeams, M.Sc. Thesis, 2017. To appear 13. Demir, Ç., Nonlocal elasticity theory for lattice dynamics applications, Ph.D. Thesis, 2017. 15. Gök, Ö. Free vibration ad bending analysis of shells and panels with FGM via FEM and DSC methods, 2017. 16. Aydın, B., Optimum design of micro and nano scaled mechanical systems, 2017. 17. Uysal S. , Nonlocal finite element method for vibration analysis of microelectro mechanical components under piezoelectricity and thermal effect, 2017 COURSES THOUGHT Undergraduate Courses: 1-Static (Mechanics) 2-Strength of Materials-I and II 3-Dynamics (Mechanics) Graduate Courses: 1-Theory of elasticity 2-Numerical solutions of plates and shells 3-Mathematical modeling and numerical analysis in engineering 4-Theory of elastic stability 5-Engineering analysis 9. Ömer Civalek; Harmonic Differential Quadrature-Finite Differences Coupled Approaches for Geometrically Nonlinear Static and Dynamic Analysis of Rectangular Plates on Elastic Foundation;

Pamukkale University Journal of Engineering Sciences, 2017

Bu çalışmada grafen tabakaların membran gibi modellenerek serbest titreşim analizleri yapılmıştır... more Bu çalışmada grafen tabakaların membran gibi modellenerek serbest titreşim analizleri yapılmıştır. Membranlar eğilmeye ya da burkulmaya karşı rijitliği olmayan ince plaklardır. Yanal güçleri eksenel ve merkezi kesme kuvvetleri ile taşırlar. Böyle yük taşımaları, aşırı incelikleri ve moment taşıma kapasitelerinin ihmal edilebilir olmasından dolayı gergin kablo ağlarına benzetilebilirler. Grafen tabakalar dikdörtgen ve kare geometriye sahip olmak üzere değişik boyutlarda modellenmiştir. Elde edilen denklemin çözümünde hem ayrık tekil konvolüsyon yöntemi ve hem de analitik yöntem kullanılmıştır. Literatürde bulunan plak modeli ile ilk defa yapılan membran modelinin sonuçları karşılaştırılmıştır. Bulunan değerler grafik ve tablo halinde sunulmuştur. In this present study vibration analysis of graphene sheets have been carried out by modeling as membrane model. Membranes are thin plates without the stiffness against bending and buckling. They carry lateral forces with axial and central shear forces. This specification, its extreme thinness and negligible moment capacity of membranes can be likened to the tense cable network. Graphene sheets are modeled in square and rectangular geometry. The resulting equation have been solved both analytically and the method of discrete singular convolution. The firstly obtained membrane results have been compared with results obtained by plate models in the literature. Results are given in graphics and tables.

Mathematical and Computational Applications, 2010

The equations of motion and bending of Euler-Bernoulli beam are formulated using the nonlocal ela... more The equations of motion and bending of Euler-Bernoulli beam are formulated using the nonlocal elasticity theory for cantilever microtubules (MTs). The method of differential quadrature (DQ) has been used for numerical modeling. The size effect is taken into consideration using the Eringen's non-local elasticity theory. Frequencies and deflections of MTs are obtained. Numerical results are presented to show the effect of small-scale effect on bending and vibration of MTs.

Materials & Design, 2009

This paper presents the discrete singular convolution (DSC) method for the free vibration analysi... more This paper presents the discrete singular convolution (DSC) method for the free vibration analysis of laminated trapezoidal plates. The plate formulation is based on first-order shear deformation theory (FSDT). The straight-sided trapezoidal domain is mapped into a square domain in the computational space using a four-node element by using the geometric transformation. The frequency parameters are obtained for symmetric angle-ply and cross-ply laminated trapezoidal plate. The accuracy of the present method is demonstrated by comparing with numerical and analytical solutions available in the literature.

Composite Structures, 2014

In this paper, mechanical responses of isolated microtubules are investigated. Microtubules can b... more In this paper, mechanical responses of isolated microtubules are investigated. Microtubules can be defined as bio-composite structures that are a component of the cytoskeleton in eukaryotic cells and play important roles in cellular processes. They have superior mechanical properties such as high rigidity and flexibility. In order to model the microtubules such as a hollow beam, a trigonometric shear deformation beam model is employed on the basis of modified strain gradient theory. The governing equations and related boundary conditions are derived by implementing Hamilton's principle. A detailed parametric study is performed to investigate the influences of shear deformation, material length scale parameterto-outer radius ratio, aspect ratio and shear modulus ratio on mechanical responses of microtubules. It is observed that microstructure-dependent behavior is more considerable when material length scale parameters are closer to the outer diameter of microtubules. Also, it can be stated that effects of shear deformation become more significant for smaller shear modulus and aspect ratios.

International Journal of Pressure Vessels and Piping, 2009

Free vibration analysis of rotating cylindrical shells is presented. Discrete singular convolutio... more Free vibration analysis of rotating cylindrical shells is presented. Discrete singular convolution (DSC) method has been proposed for numerical solution of vibration problem. The formulations are based on Love's first approximation shell theory, and include the effects of initial hoop tension and centrifugal and Coriolis accelerations due to rotation. Frequencies are obtained for different types of boundary conditions and geometric parameters. In general, close agreement between the obtained results and those of other researchers has been found.

International Journal of Engineering Science, 2012

This paper comments on the recently published work dealing with the static and dynamic analysis o... more This paper comments on the recently published work dealing with the static and dynamic analysis of micro beams by using the strain gradient elasticity theory (International Journal of Engineering Science, 47, 487-498, 2009) by Kong et al. (2009). The authors give the nonzero elements related to deviatoric stretch gradient tensor and higher-order stress. The values of g ð1Þ 131 and s ð1Þ 131 are taken as zero by Kong et al. (2009). We present the non-zero terms in this comment. Consequently, we presented some results for cantilever beam in order to show the effect of these non-zero terms on the tip deflections of micro-sized beam.

International Journal of Engineering Science, 2011

A class of higher-order continuum theories, such as modified couple stress, nonlocal elasticity, ... more A class of higher-order continuum theories, such as modified couple stress, nonlocal elasticity, micropolar elasticity (Cosserat theory) and strain gradient elasticity has been recently employed to the mechanical modeling of micro-and nano-sized structures. In this article, however, we address stability problem of micro-sized beam based on the strain gradient elasticity and couple stress theories, firstly. Analytical solution of stability problem for axially loaded nano-sized beams based on strain gradient elasticity and modified couple stress theories are presented. Bernoulli-Euler beam theory is used for modeling. By using the variational principle, the governing equations for buckling and related boundary conditions are obtained in conjunctions with the strain gradient elasticity. Both end simply supported and cantilever boundary conditions are considered. The size effect on the critical buckling load is investigated.

Communications in Numerical Methods in Engineering, 2009

Circular plates are important structural elements in modern engineering structures. In this paper... more Circular plates are important structural elements in modern engineering structures. In this paper a computationally efficient and accurate numerical model is presented for the study of free vibration and bending behavior of thick circular plates based on Mindlin plate theory. The approach developed is based on the discrete singular convolution method and the use of regularized Shannon's delta kernel. Frequency parameters, deflections and bending moments are obtained for different geometric parameters of the circular plate. Comparisons are made with existing numerical and analytical solutions in the literature. It is found that the DSC method yields accurate results for the free vibration and bending problems of thick circular plates.

Composite Structures, 2010

ABSTRACT In this paper, large deflection analysis of laminated composite plates is analysed. Nonl... more ABSTRACT In this paper, large deflection analysis of laminated composite plates is analysed. Nonlinear governing equation for bending based on first-order shear deformation theory (FSDT) in the von Karman sense is presented. These equations have been solved by the method of discrete singular convolution (DSC). Regularized Shannon’s delta (RSD) kernel and Lagrange delta sequence (LDS) kernel are selected as singular convolution to illustrate the present algorithm. The effects of plate aspect ratio, fiber orientation, boundary conditions, thickness-to-side ratio, and applied load on the nonlinear static response of the laminated plate are investigated.

Archive of Applied Mechanics, 2011

Bending analysis of micro-sized beams based on the Bernoulli-Euler beam theory is presented withi... more Bending analysis of micro-sized beams based on the Bernoulli-Euler beam theory is presented within the modified strain gradient elasticity and modified couple stress theories. The governing equations and the related boundary conditions are derived from the variational principles. These equations are solved analytically for deflection, bending, and rotation responses of micro-sized beams. Propped cantilever, both ends clamped, both ends simply

Advances in Engineering Software, 2010

Buckling analysis of rectangular plates subjected to various in-plane compressive loads using Kir... more Buckling analysis of rectangular plates subjected to various in-plane compressive loads using Kirchhoff plate theory is presented. The method of discrete singular convolution has adopted. Linearly varying, uniform and non-uniform distributed load conditions are considered on two-opposite edges for buckling. The results are obtained for different types of boundary conditions and aspect ratios. Comparisons are made with existing numerical and analytical solutions in the literature. The proposed method is suitable for the problem considered due to its simplicity, and potential for further development.