Person: UZUN, BÜŞRA
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UZUN
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BÜŞRA
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Publication Size-dependent nonlinear stability response of perforated nano/microbeams via fourier series(Springer, 2023-10-20) Civalek, Ömer; YAYLI, MUSTAFA ÖZGÜR; UZUN, BÜŞRA; Uzun, Büşra; UZUN, BÜŞRA; Mühendislik Fakültesi; İnşaat Mühendisliği Bölümü; 0000-0003-1907-9479; 0000-0002-7636-7170; 0000-0003-2231-170X; ABE-6914-2020; AAJ-6390-2021In this work, perforated and restrained nanobeams with deformable boundary conditions are modeled based on the non-local strain gradient elasticity theory with the elastic medium effect. In this approach in which the Fourier infinite series and Stokes' transformation are used together, the nanobeam is detached into parts from the two boundary points with the main part. Then using elastic force boundary conditions, a system of linear equations in terms of nonlinearity, elastic medium parameter, spring coefficients and small size effects are derived and the eigenvalue solution of these equations is also presented. The nonlinear stability of restrained nanobeam is examined and the effects of size parameters, perforation and elastic spring coefficients are studied. To reveal the accuracy and effectiveness of the offered model, several numerical applications are solved for the nonlinear stability response of restrained nanobeams with elastic medium effects. The outcomes of this method validated that the presented approach is appropriate for the stability behavior of rigid and restrained nanobeams with perforated cross section.Publication Nonlocal strain gradient approach for axial vibration analysis of arbitrary restrained nanorod(Springer, 2022-11-01) Uzun, Büşra; Civalek, Ömer; Yaylı, Mustafa Özgür; UZUN, BÜŞRA; YAYLI, MUSTAFA ÖZGÜR; Mühendislik Fakültesi; İnşaat Mühendisliği Bölümü; 0000-0002-7636-7170; AAJ-6390-2021; ABE-6914-2020Axial free vibration analysis of small size-dependent nanorod subjected to deformable restrained boundary conditions is carried out in the present work. Unlike previous works, the formulation is rewritten without resorting to any un-deformable boundary conditions neither clamped ends with Navier approximation nor considering nanorod as a compact form without any discontinuities, and the boundary conditions are assumed to be gradually deformable in the axial direction. Within the framework of Fourier sine series and Stokes' transformation, an eigenvalue problem is constructed to obtain the axial vibration frequencies. In addition, the higher-order elasticity model contains a material scale parameter considering the prominence of strain gradient stress field and a nonlocal coefficient considering the prominence of nonlocal elastic stress field. The validity of the presented procedure is checked by comparing the obtained results by giving proper values to elastic spring parameters, and good agreement is achieved. Numerical results and graphical representation are presented to demonstrate the applicability of the presented eigenvalue solution to examine the free axial response of nanorods with arbitrary boundary conditions. Effects of small-scale parameters on the dynamic response of nanorods are discussed in detail.Publication Critical buckling loads of embedded perforated microbeams with arbitrary boundary conditions via an efficient solution method(Walter De Gruyter Gmbh, 2022-11-23) Civalek, Ömer; Yayli, Mustafa Ozgur; YAYLI, MUSTAFA ÖZGÜR; Uzun, Busra; UZUN, BÜŞRA; Mühendislik Fakültesi; İnşaat Mühendisliği Bölümü; 0000-0002-7636-7170; AAJ-6390-2021; ABE-6914-2020In the present work, the small size effects on stability properties of perforated microbeams under various types of deformable boundary conditions are studied considering the Fourier sine series solution procedure and a mathematical procedure known as Stokes' transformation for the first time. The main benefit of the present method is that, in addition to considering both the gradient elasticity and the size effects, the kinematic boundary conditions are modeled by two elastic springs as deformable boundary conditions. The deformable boundary conditions and corresponding stability equation are described using the classical principle which are then used to construct a linear system of equations. Afterward, an eigenvalue problem is adopted to obtain critical buckling loads. The correctness and accuracy of the present model are demonstrated by comparing results with those available from other works in the literature. Moreover, a numerical problem is solved and presented in detail to show the influences of the perforation properties, geometrical, and the variation of small-scale parameters and foundation parameters on the stability behavior of the microbeams. In addition, according to the best knowledge of the authors, there is no study in the literature that examines the buckling behavior of perforated microbeams on elastic foundation with the gradient elasticity theory.Publication Buckling analysis of nanobeams with deformable boundaries via doublet mechanics(Springer, 2021-09-07) Civalek, Ömer; Uzun, Büşra; Yaylı, Mustafa Özgür; UZUN, BÜŞRA; YAYLI, MUSTAFA ÖZGÜR; Mühendislik Fakültesi; İnşaat Mühendisliği Bölümü; 0000-0002-7636-7170; 0000-0003-2231-170X; AAJ-6390-2021; ABE-6914-2020Buckling analysis of nanobeams with deformable boundary conditions is researched within the framework of doublet mechanics. This theory is an alternative nanomechanics theory for continuum modeling of the granular micromaterials. Doublet mechanics theory takes into consideration the small size parameter due to dealing with also granular nanosized structures. In many studies, rigid supporting conditions are explored in the nanomechanical analysis of beams. Even though the supporting conditions are accepted as undeformable, it is not possible to provide the desired rigidity in practice. A few studies have been conducted to explore the effects of deformable boundaries. In the present work, Fourier sine series as well as Stokes' transformation are utilized to attain the eigenvalue formulation and eigenvector characteristics of the problem. The combination of these two methods is a new approach in applied mechanics; at the same time, it is planned to create a bridge between rigid and deformable boundary conditions. By solving various examples, the accuracy of the proposed method has been tested and an excellent agreement has been achieved with the literature. In addition, the effect of the springs in the boundaries on the critical buckling load has been examined and given in a series of graphs.Publication Free vibration analysis of BNNT with different cross-sections via nonlocal FEM(Univ Tehran, Danishgah-i Tihran, 2018-12-01) Numanoğlu, Hayri Metin; Civalek, Omer; Uzun, Büşra; UZUN, BÜŞRA; Mühendislik Fakültesi; İnşaat Mühendisliği Bölümü; 0000-0002-7636-7170; ABE-6914-2020In the present study, free vibration behaviors of carbon nanotube (CNT) and boron nitride nanotube (BNNT) have been investigated via Eringen's nonlocal continuum theory. Size effect has been considered via nonlocal continuum theory. Nanotubes have become popular in the world of science thanks to their characteristic properties. In this study, free vibrations of Boron Nitride Nanotube (BNNT) and Carbon Nanotube (CNT) are calculated using the Nonlocal Elasticity Theory. Frequency values are found via both analytical and finite element method (FEM). Galerkin weighted residual method is used to obtain the finite element equations. BNNT and CNT are modeled as Euler - Bernoulli Beam and solutions are gained by using four different cross-section geometries with three boundary conditions. Selected geometries are circle, rectangle, triangle, and square. Frequency values are given in tables and graphs. The effect of cross-section, boundary conditions and length scale parameter on frequencies has been investigated in detail for BNNT.Publication Porosity dependent torsional vibrations of restrained fg nanotubes using modified couple stress theory(Elsevier, 2022-07-20) Uzun, Büşra; Yaylı, Mustafa Özgür; UZUN, BÜŞRA; YAYLI, MUSTAFA ÖZGÜR; Mühendislik Fakültesi; İnşaat Mühendisliği Bölümü; 0000-0002-7636-7170; ABE-6914-2020; GPV-6940-2022In the present study, size-dependent static and free torsional vibration responses of functionally graded porous nanotubes are examined using Fourier sine series and Stokes' transformation for the first time. The boundary conditions of functionally graded porous nano-sized tubes are defined by the two elastic torsional springs at the both ends. A power law rule is utilized to describe the distribution of functionally graded material and this distribution is considered through the radius of nanotube. The governing equations of the mechanical response of porous nanotubes with elastic boundary conditions and subjected to torsion are accomplished via the modified couple stress theory. The purpose of the presented work is to construct an eigen value solution including the small scale parameter based on the modified couple stress theory, torsional spring coefficients representing the boundaries of the porous nanotubes, functionally graded index caused by power law rule and porosity volume fraction.Publication Finite element formulation for nano-scaled beam elements(Wiley, 2021-12-02) Civalek, Ömer; Uzun, Buşra; Yaylı, Mustafa Özgür; YAYLI, MUSTAFA ÖZGÜR; UZUN, BÜŞRA; Mühendislik Fakültesi; İnşaat Mühendisliği Bölümü; 0000-0003-1907-9479; 0000-0003-2231-170X; ABE-6914-2020; AAJ-6390-2021In the present study, size-dependent buckling and free vibration behaviors of single-walled boron nitride nanotube (SWBNNT) are performed in conjunction with various size-dependent elasticity theories. Modified couple stress theory (MCST) and Eringen's nonlocal elasticity theory are used for size-dependent models of SWBNNT. Also, the buckling loads and frequencies are obtained by using local theory to emphasize the effects and differences of these size-dependent theories. Consequently, three different elasticity theories (two non-classical and one classical) are utilized to achieve the detailed buckling and vibration analyses of SWBNNT. In this study, the buckling loads and frequencies of SWBNNTs are obtained via presented finite element formulation. In the finite element procedures based on two different size-dependent elasticity theories, matrices containing the small size parameter are derived. With these matrices containing the small size parameters, eigenvalue problems for buckling and free vibration analyses are formed. The buckling loads and frequency values of the SWBNNTs under the size effect are obtained. The influences of the dimensionless nonlocal parameter, dimensionless material length scale parameter, length-to-diameter ratio and boundary conditions on nanotube's buckling and vibration characteristics are investigated. In addition to these influences, the rotary inertia effect neglected in many other studies is also examined.Publication A hardening nonlocal approach for vibration of axially loaded nanobeam with deformable boundaries(Springer Wien, 2023-01-31) Civalek, Ömer; YAYLI, MUSTAFA ÖZGÜR; Uzun, Büşra; UZUN, BÜŞRA; Mühendislik Fakültesi; İnşaat Mühendisliği Bölümü; 0000-0002-7636-7170; 0000-0003-1907-9479; 0000-0003-2231-170X; ABE-6914-2020; AAJ-6390-2021The dynamic response of nanobeams has attracted noticeable attention in the scientific community. Boundary conditions and other effects on the element are very important in the dynamic behavior of these elements. To the authors' knowledge, there is no paper that provides a general solution for the vibration of a nanobeam with deformable boundary conditions and subjected to a point load according to the hardening nonlocal approach. The present study reports an efficient solution method based on the Stokes' transformation which can investigate the impacts of deformable boundary conditions and axial point load on the transverse vibration of a nanobeam restrained with lateral springs. In this study, an eigenvalue problem obtained by using Fourier sine series and Stokes' transform can be used to easily analyze the frequencies of nanobeam applications subjected to vibration and axial force at both rigid and non-rigid boundaries. It is seen from the presented problem that axial load intensity, nanoscale parameter, boundary condition and length are important variables in the vibration of nanobeams. Also, it should be noted here that the present analytical method can be applicable to a variety of nanotechnology structures and machines, especially micro-electromechanical systems and nano-electromechanical systems.Publication Porosity effects on the dynamic response of arbitrary restrained fg nanobeam based on the mcst(Walter De Gruyter Gmbh, 2023-11-28) UZUN, BÜŞRA; Yaylı, Mustafa Özgür; YAYLI, MUSTAFA ÖZGÜR; Mühendislik Fakültesi; İnşaat Mühendisliği Bölümü; 0000-0002-7636-7170; 0000-0003-2231-170X; AAJ-6390-2021; ABE-6914-2020In this study, two different general eigenvalue problems for nanobeams made of functionally graded material with pores in their sections according to Rayleigh beam theory using modified couple stress theory are established. Fourier sine series and Stokes transformation are used for the solution. First, the partial differential equation of motion of the problem is discretized into an ordinary differential equation. Then, the Fourier sine series of infinite series is substituted into this ordinary differential equation to determine the Fourier coefficient. Using the force boundary conditions of the system, Stokes' transformation is performed at both ends to include elastic spring parameters. The unknown displacement terms are discretized to form two eigenvalue problems. By solving these eigenvalue problems, vibration frequencies for different boundary conditions can be found analytically. The variations of some parameters are discussed in a series of graphs.Publication Thermomechanical vibration analysis of a restrained nanobeam(Springer Heidelberg, 2023-09-25) Civelek, Ömer; Uzun, Büşra; UZUN, BÜŞRA; Yaylı, Mustafa Özgür; YAYLI, MUSTAFA ÖZGÜR; Mühendislik Fakültesi; İnşaat Mühendisliği Bölümü; 0000-0003-1907-9479; 0000-0002-7636-7170; 0000-0003-2231-170X; ABE-6914-2020; AAJ-6390-2021In this study, thermomechanical vibration analysis of a nanobeam model of boron nitride nanotube is performed. Displacement is allowed by placing elastic springs in the boundary conditions. The end displacements are represented by two different coefficients and the variable in the region is represented by an analytical Fourier sine function. The Stokes' transformation is used to force the boundary conditions to resemble the desired support shape. It is aimed in this study, a general eigenvalue problem that gives the thermal vibrational frequencies of a single-walled boron nitride nanotube under deformable boundary conditions is established. Unlike the studies with rigid boundary conditions found in the literature, in this study, there is no need to re-derive the system equations for each boundary condition change. The results are compared with similar results in the literature and excellent agreement is obtained. In addition, the effects of thermal load, elastic springs, small-scale parameters and elastic foundation are investigated and it is found that these effects have a negligible influences on the vibration frequencies of boron nitride nanotubes.