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Öğe ANALYSIS OF A LONG STRIP CONTAINING AN INTERNAL OR EDGE CRACK USING FEM(Yildiz Technical Univ, 2016) Yaylaci, Murat; Birinci, Ahmet; Adiyaman, Gokhan; Oner, ErdalThis paper presents the elastostatic plane problem of a long strip containing an internal or edge crack perpendicular to its boundaries. The plane problem consists of an infinitely long strip of thickness h. The infinitely long strip is loaded by uniformly distributed load and rests on two simple supports. It is assumed that the effect of gravity is neglected. The finite element model of the problem is constituted using ANSYS software and the two dimensional analysis of the problem is carried out. Normalized stress-intensity factors for the cases with internal and edge crack, and normal stress (sigma(x)) for uncracked layer case are obtained for various dimensionless quantities. Finally, the results obtained from the finite element analysis are verified by comparing with analytical ones and it is seen that the results from finite element analysis indicate a good agreement with the analytical solution.Öğe Analytical approach to contact mechanics of functionally graded orthotropic layers with gravitational considerations(Springer Wien, 2024) Oner, Erdal; Al-Qado, Ahmed Wasfi HasanContact problems involving deformable bodies are widespread in both industrial and everyday situations. They have a crucial impact on structural and mechanical systems, which has led to significant efforts in modeling and numerical simulations. These efforts aim to improve understanding and optimization in various engineering applications. This study examines the contact problem involving a functionally graded (FG) orthotropic layer resting on a rigid foundation, without considering frictional influences. A point load is applied to the layer through a rigid punch on its top surface. Additionally, the gravitational effects of the FG orthotropic layer are considered in the analyses. Material parameters and density of the FG orthotropic layer are presumed to exhibit exponential variations along the vertical axis. The resolution of the problem involves deriving stress and displacement expressions through the application of elasticity theory and integral transformation techniques. By imposing the pertinent boundary conditions onto these expressions, a singular integral equation is formulated, wherein the contact stress under the punch remains unknown. Employing the Gauss-Chebyshev integration method, this integral equation is subsequently numerically solved, particularly for a flat punch profile. The outcomes of this investigation encompass the determination of contact stresses under the punch, the critical separation load, and the critical separation point-marking the initial separation between the FG orthotropic layer and the rigid foundation. Additionally, the analysis yields dimensionless representations of normal stresses along the symmetry axis within the FG orthotropic layer, as well as shear stresses along a designated section proximate to the symmetry axis. Furthermore, it provides insights into the normal stresses along the x axis at the bottom surface of the FG orthotropic layer, contingent upon various parameters and distinct orthotropic material compositions.Öğe Analyzing of continuous and discontinuous contact problems of a functionally graded layer: theory of elasticity and finite element method(Taylor & Francis Inc, 2024) Yaylaci, Murat; Oner, Erdal; Adiyaman, Gokhan; Ozturk, Sevval; Yaylaci, Ecren Uzun; Birinci, AhmetContact mechanics analysis is crucial because such problems often arise in engineering practice. When examining contact mechanics, the material property of the contacting components is a crucially significant aspect. It is more complex to solve the contact mechanics of systems that are composed of materials that do not have a homogenous structure compared to materials that have homogeneous qualities throughout. While many studies on contact problems with homogeneous materials exist, those involving non-homogeneous materials are scarce in the literature. As material technology improves fast, there will be a greater need to solve such problems. In this respect, analytical and finite element method (FEM) solutions of the continuous and discontinuous contact problems of a functionally graded (FG) layer are carried out in this article. The FG layer in the problem rests on a rigid foundation and is pressed with a rigid punch. From the solutions, the contact length, contact stress, initial separation distance, and beginning and ending points of separation were determined, and the results were compared. It has been concluded that the FEM findings are consistent with the analytical results to a satisfactory degree. This study analyzes contact problem using different approaches and accounts for the influence of body force in a contact geometry that has yet to be reported.Öğe Application of artificial neural networks in the analysis of the continuous contact problem(Techno-Press, 2022) Yaylaci, Ecren Uzun; Oner, Erdal; Yaylaci, Murat; Ozdemir, Mehmet Emin; Abushattal, Ahmad; Birinci, AhmetThis paper investigates the artificial neural network (ANN) to predict the dimensionless parameters for contact pressures and contact lengths under the rigid punch, the initial separation loads, and the initial separation distances of a contact problem. The problem consisted of two elastic infinitely layers (EL) loaded by means of a rigid cylindrical punch and resting on a half-infinite plane (HP). Firstly, the problem was formulated and solved theoretically using the Theory of Elasticity (ET). Secondly, the contact problem was extended based on the ANN. External load, the radius of punch, layer heights, and material properties were created by giving examples of different values used at the training and test stages of ANN. Finally, the accuracy of the trained neural networks for the case was tested using 134 new data, generated via ET solutions to determine the best network model. ANN results were compared with ET results, and well agreements were achieved.Öğe Assessment of different solution methods for receding contact problems in functionally graded layered mediums(Elsevier, 2021) Yaylaci, Murat; Eyuboglu, Aysegul; Adiyaman, Gokhan; Yaylaci, Ecren Uzun; Oner, Erdal; Birinci, AhmetThis paper presents a comparative study of different methods, such as the analytical method, finite element method (FEM), and multilayer perceptron (MLP) for analyzing a frictionless receding contact problem. The problem consists of two layers resting on a Winkler foundation. The top layer is functionally graded (FG) along the depth and pressed using a rigid cylindrical stamp, whereas the bottom layer is homogeneous. We assumed that the contact between the two layers, and that between the FG layer and the rigid cylindrical stamp are frictionless; additionally, compressive normal tractions can be transmitted through the interface. First, the problem was solved analytically using the theory of elasticity and integral transform techniques. Second, the finite element solution of the problem was obtained using ANSYS software. Finally, the problem was extended based on the MLP, which an artificial neural network used for different problem parameters. The results of this study showed that the variations in the contact lengths at the interface between the rigid cylindrical stamp and the FG layer, those between the homogeneous layer and the FG layer, and the maximum contact pressures at these interfaces depended on various dimensionless quantities such as the stamp radius, stiffness parameter, shear modulus ratio, and elastic spring constant ratio. We observed that the results obtained with the three different methods, namely the analytical method, FEM, and MLP, are extremely compatible with each other, thus proving the accuracy of these results.Öğe The contact problem of a functionally graded layer under the effect of gravity(Wiley-V C H Verlag Gmbh, 2023) Adiyaman, Gokhan; Oner, Erdal; Yaylaci, Murat; Birinci, AhmetThis paper considers the continuous and discontinuous contact problems of a functionally graded (FG) layer under the effect of gravity. A finite distributed load is applied to the beam from the top and the beam is placed to the top of a rigid foundation. It is assumed that the shear modulus and mass density of the beam vary exponentially whereas Poisson's ratio remains constant. The problem is solved for both continuous and discontinuous cases. In each case, the governing equations and boundary conditions of the problem are reduced to an integral equation by the help of Fourier integral transform. In the continuous contact, the integral equation solved analytically and critical load that causes initial separation between the layer and the rigid foundation, separation distance and contact pressures are investigated for various non-homogeneity parameters that presents the change in the shear modulus and density and loadings. The singular integral equation in case of discontinuous contact is numerically solved by using corresponding Gauss-Chebyshev quadrature and an iterative scheme. The effect of non-homogeneity parameters and loading on the separation distance between the layer and the foundation and contact pressures are analyzed. All the results are shown in tables and figures. It is seen that increasing stiffness and decreasing density at the top of the layer reduce maximum pressures but increase separation distances. This study aims to fill the deficiency in the mechanical behavior of the coatings under gravity.Öğe Examination of analytical and finite element solutions regarding contact of a functionally graded layer(Techno-Press, 2020) Yaylaci, Murat; Adiyaman, Goekhan; Oner, Erdal; Birinci, AhmetIn this study, the continuous and discontinuous contact problems of functionally graded (FG) layer resting on a rigid foundation were considered. The top of the FG layer was loaded by a distributed load. It was assumed that the shear modulus and the density of the layer varied according to exponential functions along the depth whereas the the Poisson ratio remained constant. The problem first was solved analytically and the results were verified with the ones obtained from finite element (FE) solution. In analytical solution, the stress and displacement components for FG layer were obtained by the help of Fourier integral transform. Critical load expression and integral equation for continuous and discontinuous contact, respectively, using corresponding boundary conditions in each case. The finite element solution of the problem was carried out using ANSYS software program. In continuous contact case, initial separation distance and contact stresses along the contact surface between the FG layer and the rigid foundation were examined. Separation distances and contact stresses were obtained in case of discontinuous contact. The effect of material properties and loading were investigated using both analytical and FE solutions. It was shown that obtained results were compatible with each other.Öğe Frictionless contact mechanics of an orthotropic coating/isotropic substrate system(Techno-Press, 2021) Oner, ErdalThis study has been performed to investigate the receding contact problem of a homogeneous orthotropic coating that is not bonded to a homogeneous isotropic substrate without any interfacial defects. The isotropic substrate is supported on a Winkler foundation. The problem is solved assuming that the contact between the rigid punch and orthotropic coating, and that between the orthotropic coating and isotropic substrate, are frictionless. Additionally, the effect of the body forces is neglected, and only compressive normal tractions can be transmitted through the interfaces. The contact analysis of the orthotropic coating, which is subjected to a contact load using a rigid cylindrical punch, is performed under plane strain conditions. The governing equations are analytically found using the theory of elasticity and Fourier integral transformation techniques. Subsequently, the governing equations are reduced to a system of two singular equations, wherein the unknowns are the contact stresses and contact widths. To numerically solve the resulting singular integral equations, Gauss-Chebyshev integration formulas are employed. It is analyzed the influence of the following parameters on the contact stresses and contact widths: orthotropicmaterial properties, punch radius, load ratio, Winkler foundation stiffness.Öğe THE GENERAL SOLUTION OF A LAYERED MEDIUM RESTING ON A RIGID FOUNDATION(Yildiz Technical Univ, 2018) Adiyaman, Gokhan; Oner, Erdal; Birinci, AhmetIn this study, the general solution of a receding contact problem of layered medium resting on rigid foundation is considered. The layered medium consists of N homogeneous layer with varying material properties and heights. The contact surfaces can be receding or attached. The problem may include M receding contact surfaces. The layered medium is loaded with n concentrated loads transmitted by circular stamps and r distributed loads. The problem is reduced to integral equation system using elasticity theory and Fourier integral transform. The numerical solution of the system is done by using Matlab. A program is written to solve the problem given by the user with any geometry and loading. The program is tested with two studies from the literature and it was shown that the results are compatible.Öğe Investigation of continuous and discontinuous contact cases in the contact mechanics of graded materials using analytical method and FEM(Techno-Press, 2021) Yaylaci, Murat; Adiyaman, Gokhan; Oner, Erdal; Birinci, AhmetThe aim of this paper was to examine the continuous and discontinuous contact problems between the functionally graded (FG) layer pressed with a uniformly distributed load and homogeneous half plane using an analytical method and FEM. The FG layer is made of non-homogeneous material with an isotropic stress-strain law with exponentially varying properties. It is assumed that the contact at the FG layer-half plane interface is frictionless, and only the normal tractions can be transmitted along the contacted regions. The body force of the FG layer is considered in the study. The FG layer was positioned on the homogeneous half plane without any bonds. Thus, if the external load was smaller than a certain critical value, the contact between the FG layer and half plane would be continuous. However, when the external load exceeded the critical value, there was a separation between the FG layer and half plane on the finite region, as discontinuous contact. Therefore, there have been some steps taken in this study. Firstly, an analytical solution for continuous and discontinuous contact cases of the problem has been realized using the theory of elasticity and Fourier integral transform techniques. Then, the problem modeled and two-dimensional analysis was carried out by using ANSYS package program based on FEM. Numerical results for initial separation distance and contact stress distributions between the FG layer and homogeneous half plane for continuous contact case; the start and end points of separation and contact stress distributions between the FG layer and homogeneous half plane for discontinuous contact case were provided for various dimensionless quantities including material inhomogeneity, distributed load width, the shear module ratio and load factor for both methods. The results obtained using FEM were compared with the results found using analytical formulation. It was found that the results obtained from analytical formulation were in perfect agreement with the FEM study.Öğe Investigation of the solution for discontinuous contact problem between a functionally graded (FG) layer and homogeneous half-space(Springer, 2020) Oner, Erdal; Birinci, AhmetIn this study, the discontinuous contact problem between a functionally graded (FG) layer, which is loaded symmetrically with point loadPthrough a rigid block, and a homogeneous half-space was solved using the theory of elasticity and integral transform techniques. The shear modulus and density of the layer addressed in the problem vary with an exponential function along with its height. The half-space is homogeneous, and no binder exists on the contact surface containing the FG layer. In the solution, the body force of the FG layer was considered, whereas that of the homogeneous half-space was neglected. The Poisson's ratios of both the FG layer and homogeneous half-space were assumed to remain constant. Additionally, all the surfaces addressed in the problem were assumed to be frictionless. Using the theory of elasticity and integral transform techniques, the discontinuous contact problem was reduced to two integral equations, wherein the contact stress under the rigid block and the slope of the separation, which occurred at the interface of the FG layer and homogeneous half-space, are unknown. These integral equations were solved numerically for the flat condition of the rigid block profile using the Gauss-Chebyshev integration formula. Consequently, the stress distributions, start-end points of the separation region, and separation displacements between the FG layer and homogeneous half-space were obtained for various dimensionless quantities.Öğe Investigation of the solution for discontinuous contact problem between a functionally graded (FG) layer and homogeneous half-space (Aug, 10.1007/s00419-020-01750-y, 2020)(Springer, 2020) Oner, Erdal; Birinci, Ahmet[Abstract Not Available]Öğe Investigation of time-history response of a historical masonry minaret under seismic loads(Elsevier Science Inc, 2021) Yurdakul, Muhammet; Yilmaz, Fatih; Artar, Musa; Can, Omer; Oner, Erdal; Daloglu, Ayse T.This study presents an investigation of the seismic performance of a historical masonry minaret which was built in the 12th century in Bayburt. The minaret was built as masonry with regional stones and handmade bricks. The most important feature of the minaret is its longitudinally conical geometry. An experimental investigation was made to obtain the mechanical properties of the regional stone used in the historical minaret. A three-dimensional Finite Element Model of the historical minaret was created in SAP2000. Three earthquake ground motions such as Erzincan, Kocaeli-Duzce, and Van-Ercis were used to investigate the seismic performance of the historical minaret. The results show that Erzincan, Kocaeli-Duzce and Van-Ercis earthquakes may cause some damages in the same zone of the minaret body since the tensile stresses occurred due to the earthquakes exceed the limit tensile stress of the masonry brick. The use of the data obtained from the experimental investigation of the Bayburt yellow stone in the analysis is important for the reliability of the results.Öğe Mechanical Properties of Conventional Concrete Produced With Different Type of Aggregates in Bayburt Region(Gazi Univ, 2017) Tekin, Ilker; Kotan, Turkay; Yurdakul, Muhammet; Oner, ErdalIn this study, the limestone, natural aggregate, serpentine and Bayburt stone located in the province of Bayburt used as aggregate in conventional concrete production. In the experiments, the cement dosage and workability were kept constant. Slump, Ve-Be, unit weight and the highest temperature values in first 2 hours of the fresh concrete were measured. The concrete samples prepared with Bayburt stone were cured for 90 days and the others were cured for 28 days in lime-saturated water. Strain-stress data and water absorption values were measured on the hardened concretes at 7 and 28th days age through the records of stress and strain data during compressive strength tests. According to results of this study, the compressive strengths of the concrete samples with limestone, natural aggregate and serpentine were on average of 40, 35 and 5 MPa, respectively, on the 28th day. Also, in concrete samples with Bayburt stone, the compressive strengths were reached to 16 MPa for 28 days and to 22 MPa for 90 days.Öğe On the plane receding contact between two functionally graded layers using computational, finite element and artificial neural network methods(Wiley-V C H Verlag Gmbh, 2022) Oner, Erdal; Sengul Sabano, Bahar; Uzun Yaylaci, Ecren; Adiyaman, Gokhan; Yaylaci, Murat; Birinci, AhmetThe frictionless double receding contact problem for two functionally graded (FG) layers pressed by a uniformly distributed load is addressed in this paper. The gradation in the layers is assumed to follow an exponential variation through the height with constant Poisson's ratios. The lower layer rests on a homogeneous half-plane (HP). There is no adhesion between the FG layers or between the lower layer and the HP. The body forces of the FG layers and HP are ignored. First, the governing equations are reduced to a system of two singular integral equations with contact pressures and contact lengths as unknowns using Fourier transform techniques and boundary conditions. The integral equations are solved numerically using the Gauss-Chebyshev integration formula. Then, a parametric finite element analysis is performed using the augmented contact method. Finally, the problem was extended based on the multilayer perceptron (MLP), an artificial neural network used for different problem parameters. The effects of stiffness parameters, the normalized load length, the ratio of shear moduli, the ratio of FG layer heights to the normalized contact lengths, and normalized maximum contact pressures are explored. The results of finite element analysis and the MLP approach are used to validate the normalized maximum contact pressures and contact lengths obtained from an analytical method based on elasticity theory, and finally, good agreement between these three methods results is obtained. The obtained results could help in designing multibody indentation systems with FGMs.Öğe A STUDY ON THE CONTACT PROBLEM OF A LAYER CONSISTING OF FUNCTIONALLY GRADED MATERIAL (FGM) IN THE PRESENCE OF BODY FORCE(Mathematical Science Publ, 2023) Adiyaman, Gokhan; Oner, Erdal; Yaylaci, Murat; Birinci, AhmetOne of the most important components of the early design process for layered systems is gaining a knowledge of the behavior of materials under varied contact situations. Functionally graded materials (FGMs) have grown in popularity in layered systems as a result of their numerous benefits, such as permitting the reduction of local stress concentrations and thermal stresses often experienced in traditional composites. This paper suggests an analytical approach to solving the continuous and discontinuous contact problems of a functionally graded (FG) layer subjected to a distributed load. Elasticity theory and integral transform methods provide the basis of the aforementioned analytical approach. The FG layer rests on a half-plane that is homogeneous, and there is no adhesion or bonding at the contact surface. For this problem, we assume an exponentially varying shear modulus and mass density in the FG layer. In the solution, the body force of the FG layer is considered. The problem is solved analytically by applying boundary conditions for both continuous and discontinuous contact cases. The presented results show the effects of load factor, amplitude of distributed load, inhomogeneity parameters, and interface material property mismatch on contact stress distributions, initial separation load (critical load), initial separation distance, starting and end point of separation, and separation interval.Öğe TWO-DIMENSIONAL FRICTIONLESS CONTACT ANALYSIS OF AN ORTHOTROPIC LAYER UNDER GRAVITY(Mathematical Science Publ, 2021) Oner, ErdalAn analytical method for solving the two-dimensional frictionless continuous contact problem of an orthotropic layer pressed by a rigid stamp is presented in this paper. The orthotropic layer lies on a rigid foundation, and plane-strain orthotropy prevails in the layer, which is not bonded to the rigid foundation. An external load was applied to the orthotropic layer through a rigid stamp. The profiles of flat and cylindrical stamps as stamp shapes were handled separately. The orthotropic layer was assumed to be subjected to uniform vertical body forces owing to the effect of gravity. For values of the resultant compressive force P acting on the stamp vertically that were lesser than a critical value, the continuous contact along the orthotropic layer-rigid foundation interface was maintained. By assuming plane-strain conditions, the governing equations corresponding to the mentioned contact problem were extracted separately in the presence and absence of the body force of the orthotropic layer using the theory of elasticity and the Fourier integral transformation technique. Subsequently, the mixed boundary value problem was reduced to a singular integral equation, and the numerical solution of this singular integral equation was obtained by applying the Gauss-Chebyshev integration formulas. Numerical results reveal the effect of the orthotropic material parameters, stamp length (in the case of a flat stamp), stamp radius (in the case of a cylindrical stamp), applied load on the contact stress distributions, contact length, initial separation load and initial separation distance. The results of this study may provide insights for engineers in fields closely related to contact mechanics.