In this study, the crack problem for a homogeneous orthotropic medium loaded by a sliding rigid f... more In this study, the crack problem for a homogeneous orthotropic medium loaded by a sliding rigid flat punch is considered. The homogeneous orthotropic medium is assumed to be a half-plane and is subjected to both normal and tangential forces through the sliding action of the punch. The crack on the homogeneous orthotropic medium is supposed to a depth of and is parallel to the direction of the normal force. The effect of the geometrical parameters and coefficient of friction on the mixed-mode stress intensity factors (mode I and mode II) is investigated using a computational approach using the finite element method. Augmented Lagrange method is used for the contact algorithm between the rigid flat punch and homogeneous orthotropic half-plane. This study may provide insight to the engineers in understanding the crack mechanisms in orthotropic materials in a comprehensive way and to identify early crack propagations under frictional loadings accurately.
In this study, the crack problem for a homogeneous orthotropic medium loaded by a sliding rigid f... more In this study, the crack problem for a homogeneous orthotropic medium loaded by a sliding rigid flat punch is considered. The homogeneous orthotropic medium is assumed to be a half-plane and is subjected to both normal and tangential forces through the sliding action of the punch. The crack on the homogeneous orthotropic medium is supposed to a depth of and is parallel to the direction of the normal force. The effect of the geometrical parameters and coefficient of friction on the mixed-mode stress intensity factors (mode I and mode II) is investigated using a computational approach using the finite element method. Augmented Lagrange method is used for the contact algorithm between the rigid flat punch and homogeneous orthotropic half-plane. This study may provide insight to the engineers in understanding the crack mechanisms in orthotropic materials in a comprehensive way and to identify early crack propagations under frictional loadings accurately.
The fatigue life of a mount of a device with shock absorber is analyzed in frequency domain and t... more The fatigue life of a mount of a device with shock absorber is analyzed in frequency domain and the accuracy of the analysis was proven by the experiment.
Abstract In this study, interaction of holes in different locations in a tensile loaded composite... more Abstract In this study, interaction of holes in different locations in a tensile loaded composite plate is analysed using Bond-Based Peridynamic (PD) Theory. Moreover, the crack growth behaviour in the plate is investigated. PD simulations are conducted using adaptive dynamic relaxation solution scheme using a code developed in MATLAB. The PD solutions of the crack tip opening displacement is validated with the results obtained through finite element analysis (FEA) using ANSYS. The crack propagation paths and the effect of hole interaction on crack growth behaviour are also investigated using PD theory. Results obtained using PD theory were compared with the results of FEA and Ozaslan et al. (2019). It is found that PD can accurately capture stress, strain and hole interactions in composite laminates.
Owing to innovative developments and the need to satisfy the requirements of engineering applicat... more Owing to innovative developments and the need to satisfy the requirements of engineering applications, new and improved materials are investigated by engineers to compensate for the drawbacks of conventional materials. There is an urgent need for the tribology community to properly investigate the behavior of these materials before utilizing them in real life. In this study, the sliding frictional contact between a monoclinic coating/isotropic substrate system and a rigid cylindrical punch is provided using an analytical formulation and finite element method (FEM). The analytical expressions for the stress and displacement fields are presented, and the resulting singular integral equations (SIEs) are solved numerically. Details of the analytical formulation and the discretization used in the solution method for the SIEs are also presented. For obtaining the numerical solution, an augmented finite element method is used with plane strain conditions and 6-node higher order finite elements. According to the results, the analytical formulation and FEM results are consistent. Using different lamina orientations, coefficient of friction, and geometric/material parameters, provides the tribology community with a highly qualified parametric study that informs surface wear and surface fatigue crack initiation in contact mechanics problems
ZAMM - Journal of Applied Mathematics and Mechanics / Zeitschrift für Angewandte Mathematik und Mechanik, 2019
In this study, the contact problem for a homogeneous orthotropic coating-isotropic substrate syst... more In this study, the contact problem for a homogeneous orthotropic coating-isotropic substrate system is considered. The rigid stamp slides over the orthotropic coating whose bottom surface is bonded to a homogeneous isotropic substrate. The bottom surface of the substrate is fixed to the ground. By using Fourier integral transforms, the partial differential equations are converted to ordinary differential equations (ODEs). The displacement components for coating and substrate are obtained by solving the corresponding ODEs. A numerical study based on finite element analysis (FEA) is also conducted. The results from the analytical formulation are directly compared with the FEA results. The effects of orthotropic and isotropic material properties, coefficient of friction between the sliding surfaces, geometrical properties on the contact stresses and contact widths are presented. The results of this study may help tribology engineers to understand the deformation characteristics of the coating-substrate systems and enhance their knowledge on friction and wear mechanisms of sliding surfaces.
In this study, contact problem for a homogeneous orthotropic layer loaded by a rigid cylindrical ... more In this study, contact problem for a homogeneous orthotropic layer loaded by a rigid cylindrical stamp is considered. The rigid cylindrical stamp slides over the contacting medium whose bottom surface is fixed to the ground in all directions. Using the integral transformation technique, the contact problem is formulated analytically into a singular integral equation. The resulting integral equation is converted to algebraic equations by using Gauss-Jacobi integration formulas and solved numerically. In addition to the analytical formulation, a finite element method (FEM) study is also conducted. The results that are obtained using FEM are compared with the results found using analytical formulation. It is found that the results obtained from analytical formulation and FEM study are in good agreement with each other. The primary intention of this paper is to demonstrate the effects of orthotropic material properties, geometrical properties and the coefficient of friction on the stresses generated due to the sliding motion of the rigid cylindrical stamp. The results of this study may provide benchmark results for engineers to be used in tribology applications involving friction and wear mechanisms.
Üretim parametreleri, özellikle havacılık sınıfı polieter keton keton (PEKK)/karbon fiber (CF) ko... more Üretim parametreleri, özellikle havacılık sınıfı polieter keton keton (PEKK)/karbon fiber (CF) kompozitlerde termoplastik kompozitlerin mekanik özelliklerinde önemli bir rol oynamaktadır. Sunulan bu çalışmada, farklı sıcaklık değerlerinde konsolide edilen PEKK/CF kompozitlerinin mekanik özellikleri değerlendirilmiştir. Benzer bir basınç profiliyle, kür sıcaklığının PEKK/CF kompozit laminatın gerilme, laminalar arası kesme dayanımı (ILSS) ve düzlem içi kesme dayanımı (IPSS) üzerindeki etkisini belirlemek için çeşitli kür sıcaklıkları uygulandı. Kompozit laminatlardaki gözeneklilik, delaminasyon ve boşluk içeriği, Ultrasonik Test yoluyla NDT yöntemi kullanılarak karakterize edildi. Bu makale, bir polieter keton keton (PEKK)/karbon fiber (CF) kompozitleri kullanılarak otoklav işlemiyle farklı kürleme sıcaklığı numunelerinin karşılaştırılması için üretim kupon test numunelerinin bazı güncel sonuçlarını sunmaktadır. PEKK/CF'nin gerilme ve laminalar arası kayma mukavemeti özellikleri, sırasıyla 350°C, 375°C ve 400°C'de farklı kürleme sıcaklık geçmişleri ile hazırlanacak şekilde çalışılmıştır. Yapılan testler ideal kürleme sıcaklığını 400°C derece olarak belirlemiştir.
Stresses due to frictional sliding contact between a rigid cylinder and laminated glass fiber com... more Stresses due to frictional sliding contact between a rigid cylinder and laminated glass fiber composites are calculated in this study. A novel analytical formulation based on Cholesky decomposition, Fourier transforms, and singular integral equation is presented to solve the stress and displacement fields both at the contact patch and sub-surface, which can take into account transition of laminae with different fiber angle. An augmented finite element algorithm having an adaptive mesh refinement algorithm is also developed to verify the results of the analytical formulation. A perfect match between these results reveals the success of the new analytical formulation. Then, the formulation is implemented for various loading types and composite-related parameters to reveal the effects of those on the surface and sub-surface stresses. The results and discussions presented can be beneficial for the structural design of laminated composites under severe contact conditions. Keywords Frictional sliding contact • Laminated composite • Augmented finite element algorithm • Singular integral equation 1 Introduction Understanding the mechanical behavior and performance of materials used in industry is quite important in engineering mechanics field and surface, coating, and film sub-field. Tribology can be named as a science which seeks to fathom and improve the mechanical behavior and performance of surfaces that are in contact. The word tribology has first appeared in a technical report, where its scope was generally related to research and evaluation of friction, lubrication, and wear mechanisms [1]. High energy consumption, carbon dioxide emissions, and excessive performance degradation have always been important issues in industrial applications due to the effects of these mechanisms (see [2] for the impact of these on the economical perspective). In past decades, more research was focused on conventional materials involving metal/metal and metal/ceramic-based contacts. Nowadays, using unconventional materials for metal/polymer and polymer/polymer-based contacts in industry assures many advantages as one conventional material can outperform others by combining one or more positive properties of different conventional materials. Many corporations and corporate-related institutions in marine, defense, construction, automotive, and aerospace industries require unconventional materials to improve the performance characteristics of their products mechanical-wise. For this reason, contact and material behavior of these materials need to be further explored by means of tribology. Flexures, composite housings and bearings, turbine blade coatings, armored plates, composite car parts, propeller shafts, brake systems, and water proof ceilings are some important examples of products manufactured using unconventional materials [3-5].
With the increasing research in the field of contact mechanics, different types of contact models... more With the increasing research in the field of contact mechanics, different types of contact models have been investigated by many researchers by employing various complex material models. To ascertain the orthotropy effect and modeling parameters on a receding contact model, the double frictional receding contact problem for an orthotropic bilayer loaded by a cylindrical punch is taken into account in this study. Assuming plane strain sliding conditions, the governing equations are found analytically using Fourier integral transformation technique. Then, the resulting singular integral equations are solved numerically using an iterative method. The weight function describing the asymptotic behavior of the stresses are investigated in detail and powers of the stress singularities are provided. To control the trustworthiness and correctness of the analytical formulation and to compare the resulting stress distributions and contact boundaries, a numerically efficient finite element method was employed using augmented Lagrange contact algorithm. The aim of this paper is to investigate the orthotropy effect, modeling parameters and coefficients of friction on the surface and interface stresses, surface and interface contact boundaries, powers of stress singularities, weight function and to provide highly parametric benchmark results for tribological community in designing wear resistant systems.
Journal of Structural Engineering & Applied Mechanics, 2019
In this paper, the moving contact problem between the punch and a layer supported by a Winkler ty... more In this paper, the moving contact problem between the punch and a layer supported by a Winkler type foundation is considered under plane strain conditions. The cylindrical punch moves smoothly with constant velocity over the homogeneous layer. With the use of Galilean transformation and Fourier integral transform, the plane contact problem is converted into a Cauchy type singular integral equation. The singular integral equation is solved numerically by performing the appropriate collocation method, and the contact width, the contact and in-plane stresses are calculated. The results show that the stiffness of the Winkler foundation and the moving velocity have a significant effect on the contact width and the behavior of the stress field.
A new computational method based on the Jk-integral is put forward for the purpose of conducting ... more A new computational method based on the Jk-integral is put forward for the purpose of conducting fracture analysis of orthotropic materials subjected to hygrothermal stresses. By utilizing the constitutive relations of plane orthotropic hygrothermoelasticity, an alternative expression for the Jk-integral is derived to replace the general limit definition. A numerical procedure is developed and integrated into a finite element analysis
International Journal of Mechanical Sciences, 2017
This study investigates the plane frictional contact problem of a cylindrical punch on a function... more This study investigates the plane frictional contact problem of a cylindrical punch on a functionally graded orthotropic medium (FGOM). Both analytical and computational methods are developed to obtain the contact stresses. The elastic modulus is assumed to vary exponentially and the principal axes of orthotropy are assumed to be aligned with the global coordinates. In the analytical formulation, plane elasticity equations are converted to Cauchy-type singular integral equation of the second type by using Fourier Transform technique. The resulting integral equations are then solved numerically to obtain the contact stresses throughout the medium for plane stress condition. In the computational model, the elastic modulus of each finite element is specified at its centroid by using the predefined functional variation. The results obtained from the finite element analysis is verified by comparing the results obtained using the analytical formulation. The results of this study can guide tribology engineers in determining the contact stresses that have a great effect on the wear resistance of mating components.
In this study, the crack problem for a homogeneous orthotropic medium loaded by a sliding rigid f... more In this study, the crack problem for a homogeneous orthotropic medium loaded by a sliding rigid flat punch is considered. The homogeneous orthotropic medium is assumed to be a half-plane and is subjected to both normal and tangential forces through the sliding action of the punch. The crack on the homogeneous orthotropic medium is supposed to a depth of and is parallel to the direction of the normal force. The effect of the geometrical parameters and coefficient of friction on the mixed-mode stress intensity factors (mode I and mode II) is investigated using a computational approach using the finite element method. Augmented Lagrange method is used for the contact algorithm between the rigid flat punch and homogeneous orthotropic half-plane. This study may provide insight to the engineers in understanding the crack mechanisms in orthotropic materials in a comprehensive way and to identify early crack propagations under frictional loadings accurately.
In this study, the crack problem for a homogeneous orthotropic medium loaded by a sliding rigid f... more In this study, the crack problem for a homogeneous orthotropic medium loaded by a sliding rigid flat punch is considered. The homogeneous orthotropic medium is assumed to be a half-plane and is subjected to both normal and tangential forces through the sliding action of the punch. The crack on the homogeneous orthotropic medium is supposed to a depth of and is parallel to the direction of the normal force. The effect of the geometrical parameters and coefficient of friction on the mixed-mode stress intensity factors (mode I and mode II) is investigated using a computational approach using the finite element method. Augmented Lagrange method is used for the contact algorithm between the rigid flat punch and homogeneous orthotropic half-plane. This study may provide insight to the engineers in understanding the crack mechanisms in orthotropic materials in a comprehensive way and to identify early crack propagations under frictional loadings accurately.
The fatigue life of a mount of a device with shock absorber is analyzed in frequency domain and t... more The fatigue life of a mount of a device with shock absorber is analyzed in frequency domain and the accuracy of the analysis was proven by the experiment.
Abstract In this study, interaction of holes in different locations in a tensile loaded composite... more Abstract In this study, interaction of holes in different locations in a tensile loaded composite plate is analysed using Bond-Based Peridynamic (PD) Theory. Moreover, the crack growth behaviour in the plate is investigated. PD simulations are conducted using adaptive dynamic relaxation solution scheme using a code developed in MATLAB. The PD solutions of the crack tip opening displacement is validated with the results obtained through finite element analysis (FEA) using ANSYS. The crack propagation paths and the effect of hole interaction on crack growth behaviour are also investigated using PD theory. Results obtained using PD theory were compared with the results of FEA and Ozaslan et al. (2019). It is found that PD can accurately capture stress, strain and hole interactions in composite laminates.
Owing to innovative developments and the need to satisfy the requirements of engineering applicat... more Owing to innovative developments and the need to satisfy the requirements of engineering applications, new and improved materials are investigated by engineers to compensate for the drawbacks of conventional materials. There is an urgent need for the tribology community to properly investigate the behavior of these materials before utilizing them in real life. In this study, the sliding frictional contact between a monoclinic coating/isotropic substrate system and a rigid cylindrical punch is provided using an analytical formulation and finite element method (FEM). The analytical expressions for the stress and displacement fields are presented, and the resulting singular integral equations (SIEs) are solved numerically. Details of the analytical formulation and the discretization used in the solution method for the SIEs are also presented. For obtaining the numerical solution, an augmented finite element method is used with plane strain conditions and 6-node higher order finite elements. According to the results, the analytical formulation and FEM results are consistent. Using different lamina orientations, coefficient of friction, and geometric/material parameters, provides the tribology community with a highly qualified parametric study that informs surface wear and surface fatigue crack initiation in contact mechanics problems
ZAMM - Journal of Applied Mathematics and Mechanics / Zeitschrift für Angewandte Mathematik und Mechanik, 2019
In this study, the contact problem for a homogeneous orthotropic coating-isotropic substrate syst... more In this study, the contact problem for a homogeneous orthotropic coating-isotropic substrate system is considered. The rigid stamp slides over the orthotropic coating whose bottom surface is bonded to a homogeneous isotropic substrate. The bottom surface of the substrate is fixed to the ground. By using Fourier integral transforms, the partial differential equations are converted to ordinary differential equations (ODEs). The displacement components for coating and substrate are obtained by solving the corresponding ODEs. A numerical study based on finite element analysis (FEA) is also conducted. The results from the analytical formulation are directly compared with the FEA results. The effects of orthotropic and isotropic material properties, coefficient of friction between the sliding surfaces, geometrical properties on the contact stresses and contact widths are presented. The results of this study may help tribology engineers to understand the deformation characteristics of the coating-substrate systems and enhance their knowledge on friction and wear mechanisms of sliding surfaces.
In this study, contact problem for a homogeneous orthotropic layer loaded by a rigid cylindrical ... more In this study, contact problem for a homogeneous orthotropic layer loaded by a rigid cylindrical stamp is considered. The rigid cylindrical stamp slides over the contacting medium whose bottom surface is fixed to the ground in all directions. Using the integral transformation technique, the contact problem is formulated analytically into a singular integral equation. The resulting integral equation is converted to algebraic equations by using Gauss-Jacobi integration formulas and solved numerically. In addition to the analytical formulation, a finite element method (FEM) study is also conducted. The results that are obtained using FEM are compared with the results found using analytical formulation. It is found that the results obtained from analytical formulation and FEM study are in good agreement with each other. The primary intention of this paper is to demonstrate the effects of orthotropic material properties, geometrical properties and the coefficient of friction on the stresses generated due to the sliding motion of the rigid cylindrical stamp. The results of this study may provide benchmark results for engineers to be used in tribology applications involving friction and wear mechanisms.
Üretim parametreleri, özellikle havacılık sınıfı polieter keton keton (PEKK)/karbon fiber (CF) ko... more Üretim parametreleri, özellikle havacılık sınıfı polieter keton keton (PEKK)/karbon fiber (CF) kompozitlerde termoplastik kompozitlerin mekanik özelliklerinde önemli bir rol oynamaktadır. Sunulan bu çalışmada, farklı sıcaklık değerlerinde konsolide edilen PEKK/CF kompozitlerinin mekanik özellikleri değerlendirilmiştir. Benzer bir basınç profiliyle, kür sıcaklığının PEKK/CF kompozit laminatın gerilme, laminalar arası kesme dayanımı (ILSS) ve düzlem içi kesme dayanımı (IPSS) üzerindeki etkisini belirlemek için çeşitli kür sıcaklıkları uygulandı. Kompozit laminatlardaki gözeneklilik, delaminasyon ve boşluk içeriği, Ultrasonik Test yoluyla NDT yöntemi kullanılarak karakterize edildi. Bu makale, bir polieter keton keton (PEKK)/karbon fiber (CF) kompozitleri kullanılarak otoklav işlemiyle farklı kürleme sıcaklığı numunelerinin karşılaştırılması için üretim kupon test numunelerinin bazı güncel sonuçlarını sunmaktadır. PEKK/CF'nin gerilme ve laminalar arası kayma mukavemeti özellikleri, sırasıyla 350°C, 375°C ve 400°C'de farklı kürleme sıcaklık geçmişleri ile hazırlanacak şekilde çalışılmıştır. Yapılan testler ideal kürleme sıcaklığını 400°C derece olarak belirlemiştir.
Stresses due to frictional sliding contact between a rigid cylinder and laminated glass fiber com... more Stresses due to frictional sliding contact between a rigid cylinder and laminated glass fiber composites are calculated in this study. A novel analytical formulation based on Cholesky decomposition, Fourier transforms, and singular integral equation is presented to solve the stress and displacement fields both at the contact patch and sub-surface, which can take into account transition of laminae with different fiber angle. An augmented finite element algorithm having an adaptive mesh refinement algorithm is also developed to verify the results of the analytical formulation. A perfect match between these results reveals the success of the new analytical formulation. Then, the formulation is implemented for various loading types and composite-related parameters to reveal the effects of those on the surface and sub-surface stresses. The results and discussions presented can be beneficial for the structural design of laminated composites under severe contact conditions. Keywords Frictional sliding contact • Laminated composite • Augmented finite element algorithm • Singular integral equation 1 Introduction Understanding the mechanical behavior and performance of materials used in industry is quite important in engineering mechanics field and surface, coating, and film sub-field. Tribology can be named as a science which seeks to fathom and improve the mechanical behavior and performance of surfaces that are in contact. The word tribology has first appeared in a technical report, where its scope was generally related to research and evaluation of friction, lubrication, and wear mechanisms [1]. High energy consumption, carbon dioxide emissions, and excessive performance degradation have always been important issues in industrial applications due to the effects of these mechanisms (see [2] for the impact of these on the economical perspective). In past decades, more research was focused on conventional materials involving metal/metal and metal/ceramic-based contacts. Nowadays, using unconventional materials for metal/polymer and polymer/polymer-based contacts in industry assures many advantages as one conventional material can outperform others by combining one or more positive properties of different conventional materials. Many corporations and corporate-related institutions in marine, defense, construction, automotive, and aerospace industries require unconventional materials to improve the performance characteristics of their products mechanical-wise. For this reason, contact and material behavior of these materials need to be further explored by means of tribology. Flexures, composite housings and bearings, turbine blade coatings, armored plates, composite car parts, propeller shafts, brake systems, and water proof ceilings are some important examples of products manufactured using unconventional materials [3-5].
With the increasing research in the field of contact mechanics, different types of contact models... more With the increasing research in the field of contact mechanics, different types of contact models have been investigated by many researchers by employing various complex material models. To ascertain the orthotropy effect and modeling parameters on a receding contact model, the double frictional receding contact problem for an orthotropic bilayer loaded by a cylindrical punch is taken into account in this study. Assuming plane strain sliding conditions, the governing equations are found analytically using Fourier integral transformation technique. Then, the resulting singular integral equations are solved numerically using an iterative method. The weight function describing the asymptotic behavior of the stresses are investigated in detail and powers of the stress singularities are provided. To control the trustworthiness and correctness of the analytical formulation and to compare the resulting stress distributions and contact boundaries, a numerically efficient finite element method was employed using augmented Lagrange contact algorithm. The aim of this paper is to investigate the orthotropy effect, modeling parameters and coefficients of friction on the surface and interface stresses, surface and interface contact boundaries, powers of stress singularities, weight function and to provide highly parametric benchmark results for tribological community in designing wear resistant systems.
Journal of Structural Engineering & Applied Mechanics, 2019
In this paper, the moving contact problem between the punch and a layer supported by a Winkler ty... more In this paper, the moving contact problem between the punch and a layer supported by a Winkler type foundation is considered under plane strain conditions. The cylindrical punch moves smoothly with constant velocity over the homogeneous layer. With the use of Galilean transformation and Fourier integral transform, the plane contact problem is converted into a Cauchy type singular integral equation. The singular integral equation is solved numerically by performing the appropriate collocation method, and the contact width, the contact and in-plane stresses are calculated. The results show that the stiffness of the Winkler foundation and the moving velocity have a significant effect on the contact width and the behavior of the stress field.
A new computational method based on the Jk-integral is put forward for the purpose of conducting ... more A new computational method based on the Jk-integral is put forward for the purpose of conducting fracture analysis of orthotropic materials subjected to hygrothermal stresses. By utilizing the constitutive relations of plane orthotropic hygrothermoelasticity, an alternative expression for the Jk-integral is derived to replace the general limit definition. A numerical procedure is developed and integrated into a finite element analysis
International Journal of Mechanical Sciences, 2017
This study investigates the plane frictional contact problem of a cylindrical punch on a function... more This study investigates the plane frictional contact problem of a cylindrical punch on a functionally graded orthotropic medium (FGOM). Both analytical and computational methods are developed to obtain the contact stresses. The elastic modulus is assumed to vary exponentially and the principal axes of orthotropy are assumed to be aligned with the global coordinates. In the analytical formulation, plane elasticity equations are converted to Cauchy-type singular integral equation of the second type by using Fourier Transform technique. The resulting integral equations are then solved numerically to obtain the contact stresses throughout the medium for plane stress condition. In the computational model, the elastic modulus of each finite element is specified at its centroid by using the predefined functional variation. The results obtained from the finite element analysis is verified by comparing the results obtained using the analytical formulation. The results of this study can guide tribology engineers in determining the contact stresses that have a great effect on the wear resistance of mating components.
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