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Öğe Dynamic response of embedded Timoshenko CNTs exposed to magnetic and thermal fields subjected to moving load based on doublet mechanics(Springer Heidelberg, 2023) Ozmen, Ramazan; Esen, IsmailThis paper uses the nanomechanical theory to examine the dynamic behaviour and response of embedded zigzag and armchair carbon nanotubes (CNTs) under moving load in thermal and magnetic fields. The nanoscale size effect of CNTs is imposed using the doublet mechanics theory. The CNTs modelled as a Timoshenko beam structure with shear stress effects. The modified motion and non-classical boundary condition equations of embedded CNTs under moving load and subjected to thermal and magnetic loads are obtained using Hamilton's principle. Navier's analytical solution and Newmark's time integration methods are imposed to obtain the time domain responses of simply supported CNTs. The computational accuracy of the proposed model has been validated and proven by previously published studies for free and forced responses. In the parametric analyses, the influence of the doublet length scale parameter (DMP), armchair and zigzag structures of CNTs, moving load's velocity, magnetic field's intensity, temperature rise, and the stiffnesses of two-parameter Pasternak foundation on dynamic responses of CNTs are considered. It is obtained that the DMP significantly affects CNTs' free and forced vibration under a moving load. The DMP increase reduces system stiffness, lowering the dimensionless frequency and increasing the dynamic amplification factor. Also, the DMP has a greater influence at higher vibration modes and beam aspect ratios. The proposed modelling is helpful for the analysis, design, and remote control of MEMS/NEMS as nano-transport systems, nanosensors, and nano-actuators manufactured from CNTs.Öğe The effects of pre-stressed rods contoured by different bending techniques on posterior instrumentation of L4-L5 lumbar spine segment: A finite element study(Sage Publications Ltd, 2022) Sengul, Emre; Ozmen, Ramazan; Demir, TeyfikPosterior pedicle screw instrumentation (PPSI) is a well-known method in lumbar spine surgery. Understanding how PPSI affects the biomechanics of the lumbar spine is an important issue. In particular, during PPSI operations, surgeons bend rods according to the patients' spinal curvatures based on their own experiences. As a result, residual stresses develop on the rods due to this bending. Although many finite element-based biomechanical studies have been performed for PPSI, studies comparing the effects of residual stresses arising from rod contouring on the construct stresses are lacking. Thus, this study aimed to investigate the effects of residual stress in PPSI using rods contoured with a French bender and an in-situ bender, as well as comparing the differences in stress increment with straight and contoured rods for different physiological motions. Accordingly, a finite element (FE) model of the L4-L5 lumbar spine segment was developed for PPSI and the effects of residual stresses on rods were investigated by using different bending methods. In the simulations, it was found that rods contoured with a French bender with residual stress resulted in significantly more increased stress in PPSI compared to those contoured with an in-situ bender. The results of this study emphasize that increased stress in PPSI due to the residual stresses for different physiological motions may increase the risk of PPSI failures. Additionally, the finite element modeling approach employed here could be used as a fundamental tool for further investigations of topics such as PPSI fatigue life and failure studies.Öğe Free and forced thermomechanical vibration and buckling responses of functionally graded magneto-electro-elastic porous nanoplates(Taylor & Francis Inc, 2024) Esen, Ismail; Ozmen, RamazanThe novelty of this study is to model and investigate the free and forced thermal vibration and buckling behaviors of a porous functionally graded magneto-electro-elastic (MEE) nanoplate made of barium-titanate and cobalt-ferrite and subjected to moving loads. In the modeling, the strains are assumed to originate from classical mechanics, thermal expansion, electroelastic, and magnetostrictive properties, nonlocal elasticity, and strain gradient elasticity, and the motion equations of MEE nanoplate are obtained by Hamilton's principle Considering various cases, the effects of thermal stresses, magneto-electro-elastic coupling, externally applied electric and magnetic field potential, nonlocal properties (nonlocal and material size parameters), porosity volume fraction on the free vibration and buckling behavior have been studied. Additionally, the forced response to the moving load for various cases of the velocity of the load is also investigated. It is observed that the free-response and buckling of the nanoplate vary with the material composition, externally applied electrical and magnetic fields, temperature rise, and porosity volume fraction. Furthermore, it is also noticed that the velocity of the load is the most influential factor in the forced response of the MEE nanoplate. Moreover, the material composition of the nanoplate characterizes the magneto-electro-elastic response depending on the amounts of barium-titanate (electro-elastic) and cobalt-ferrite (magnetostrictive). The stiffness of the MEE nanoplate can be controlled by regulating the intensities of electric and magnetic fields. This property can keep the bending and buckling stability of the nanoplate exposed to severe thermal and high-speed moving loads.Öğe Investigation of Microstructure and Mechanical Properties of Layered Material Produced by Adding Al2O3 to 316L Stainless Steel(Mdpi, 2023) Albahlol, Osama Albahl Alshtewe; Elkilani, Rajab; Cug, Harun; Erden, Mehmet Akif; Ozmen, Ramazan; Esen, IsmailThis study developed new advanced composite materials consisting of functional grading of 316L and Al2O3 specially designed for potential biomedical applications. Mechanical properties were characterized by tensile testing, and microstructural properties by optical microscope, scanning electron microscope (SEM), and Energy Dispersive X-Ray (EDX) analyses. The uniform mixture in the material, up to 40% by weight of Al2O3, is uniformly distributed in the 316L matrix that shows disintegration. Then, samples with 2, 3, 4, and 5 layers were produced in functionally graded 6, 7, 8, and 9 material types, respectively. The layer thicknesses were formed with an average of 900 & mu;m. The results show that new composite materials can be produced functionally using 316L and Al2O3 in a layered manner. As a result of the mechanical experiments, it has been observed that the tensile strength of the layered composite structures remains within the range of 91-191 MPa, depending on the layer type. It has been observed that the elongation varies between 3.16 and 12.46%. According to these results, the materials obtained are considered suitable for use as an alternative prosthetic material in biomedical applications. The tensile strength, % elongation of the Composition 7, and yield strength of functionally graded (316 + (316L-10 Al2O3) + (316L-20 Al2O3) + (316L-30 Al2O3)) material are 123 megapascals (MPa), 7.3%, and 111MPa, respectively, and according to the literature, the mechanical strength of human bone is very close to this composition properties.Öğe Investigation of the effect of bolt diameter and end plate thickness change on bolt column-beam connection(Techno-Press, 2024) Dogan, Samet Oguzhan; Gursoy, Senol; Ozmen, RamazanSeveral types of column-beam connections are used in the design of steel structures. This situation causes different cross-section effects and, therefore, different displacements and deformations. In other words, connection elements such as welds, bolts, continuity plates, end plates, and stiffness plates used in steel column-beam connections directly affect the section effects. This matter reveals the necessity of knowing the steel column-beam connection behaviours. In this article, behaviours of bolted column-beam connection with end plate widely used in steel structures are investigated comparatively the effects of the stiffness plates added to the beam body, the change in the end plate thickness and bolt diameter. The results obtained reveal that the moment and force carrying capacity of the said connection increases with the increase in the end plate thickness and bolt diameter. In contrast, it causes the other elements to deform and lose their capacity. This matter shows that optimum dimensions are very important in steel column-beam connections. In addition, it has been seen that adding a stiffness plate to the beam body part positively contributes to the connection's moment-carrying capacity.Öğe An investigation on braking systems used in railway vehicles(Elsevier - Division Reed Elsevier India Pvt Ltd, 2020) Gunay, Mustafa; Korkmaz, Mehmet Erdi; Ozmen, RamazanThe high safety and comfort expectations under varying conditions have required the development of brake systems in railway vehicles. The main factors affecting the performance and function of the brake system are braking force, mass and speed of the vehicles, stopping or braking distance, railway condition and environmental factors. In this work, the brake systems such as disc and tread brakes, dynamic brakes, aerodynamic brakes, vacuum brakes, electro-pneumatic brakes have been reviewed. The braking systems are examined in two main groups as adhesion dependent and independent brakes. Evaluations have been made on brake disc-pad mechanisms which are the most important components in all brake systems in terms of safe operation especially for freight and high-speed trains. In this context, the experimental and numerical analysis studies on the interactions of brake system components including brake disk-pad geometries and material properties have been considered. Accordingly, research and development studies based on finite element modeling and prototype manufacturing is recommended in order to produce high efficiency and safety brake systems compatible with rail system vehicle. The information obtained from these studies will indirectly contribute to sustainability. Furthermore, this review study focused on the detailed analysis of scientific and applied research can contribute to the productivity of institutions and organizations operating in the braking systems of railway vehicles. (C) 2020 Karabuk University. Publishing services by Elsevier B.V.Öğe Kinematical considerations related to prosthesis position and core radius on the biomechanics of the C5-C6 functional spinal unit(Elsevier - Division Reed Elsevier India Pvt Ltd, 2019) Ozmen, Ramazan; Gunay, MustafaTotal disc arthroplasty (TDA) is one of the most preferred surgical procedure instead of fusion in the treatment of a degenerated disc. In this study, the effects of changing position and core radius of an artificial disc prosthesis, placed in the C5-C6 functional spinal unit (FSU), on the range of motions (ROM) of the FSU was investigated via the finite element method. Firstly, three-dimensional CAD models of C5 and C6 vertebrae was obtained from a computerized tomography images of healthy male neck. Finite element model of a healthy C5-C6 FSU was created containing vertebrae, intervertebral discs, tissues and facet joints considering the normal anatomical features. In modelling of TDA method, the core radius of artificial prostheses was assumed as 4 mm, 6 mm and 8 mm, and their positions were changed to anterior, posterior and lateral according to their neutral positions. Finally, the effects of core radius and position changes of the prosthesis on the biomechanical properties of the FSU were investigated by the finite element simulations. It was found that the flexion and extension ROM of the implanted FSU was increased with changing the rotation center of the prosthesis from anterior to posterior and increasing the core radius from 4 to 8 mm. However, displacing the rotation center of the prosthesis in lateral direction did not change the ROM of the model for all motion types. (C) 2018 Karabuk University. Publishing services by Elsevier B.V.Öğe A study on graphene-reinforced magneto-electro-elastic laminated nanoplate's thermomechanical vibration behaviour based on a higher-order plate theory(Elsevier, 2024) Ozmen, Ramazan; Esen, IsmailSandwich nanostructures incorporating piezoelectric and magneto-electro-elastic properties have emerged as promising candidates for next-generation smart devices and composites. Due to their exceptional design, fabrication, and energy conversion capabilities, these structures are extensively utilised as sensors and actuators in nano-electromechanical systems. Accordingly, in this article, the free vibration behaviour of a multifunctional laminated (MFL) nanoplate with piezoelectric PZT5-H and magnetostrictive CoFe2O4 (cobalt-ferrite) face layers and a graphene-reinforced core layer is investigated by applying a higher-order sinusoidal shear deformation theory (HSDT). In addition, two different material cases consisting of Ti6Al4V and ZrO2 materials and two foam models, uniform and symmetric, are considered for the foam core layer. Hamilton's principle is used to obtain the plate's governing equations. Navier's solution approach is utilised to get the natural frequencies of the laminated nanoplate under thermal load and electric and magnetic fields. A parametric study is performed to determine the effects of volumetric graphene content, the foam model and its pore ratio, face/core material content, external electric and magnetic potential, and thermal load on the free vibration response of the MFL nanoplate. The obtained numerical results can be a reference point for future research on layered porous MEE structures, especially for micro/nano-sized systems.Öğe Thermal vibration and buckling of magneto-electro-elastic functionally graded porous nanoplates using nonlocal strain gradient elasticity(Elsevier Sci Ltd, 2022) Esen, Ismail; Ozmen, RamazanThis study models and examines the thermal vibration and buckling behaviours of a porous nanoplate made of functional grading of barium-titanate and cobalt-ferrite. The porosity in the nanoplate is modelled with uniform and symmetrical porosity distribution functions. In the constitutive equation of the nanoplate, the strains are assumed to originate from classical mechanics, thermal expansion, electroelastic and magnetostrictive properties, nonlocal elasticity, and strain gradient elasticity. The motion equations of magneto-electro-elastic (MEE) nanoplate is obtained by Hamilton's principle. The study investigated the effects of thermal stresses, magnetoelectro-elastic coupling, externally applied electric and magnetic field potential, nonlocal properties (nonlocal and material size parameters), and porosity volume fraction and function of porosity variation across thickness in free vibration and buckling behaviour of the nanoplate. According to the analysis results, the dimensionless frequencies decrease as the barium-titanate ratio in the nanoplate increases, and the frequencies increase as the cobalt-ferrite ratio increases, depending on the material grading index. While temperature increased and porosity ratio decreased dimensionless frequencies, external magnetic potential increased dimensionless frequencies. On the other hand, the application of electric potential causes a slight increase in dimensionless frequencies compared to the effect of magnetic potential.Öğe Thermomechanical flexural wave propagation responses of FG porous nanoplates in thermal and magnetic fields(Springer Wien, 2023) Ozmen, Ramazan; Esen, IsmailThis study uses higher-order plate and nonlocal strain gradient elasticity theories to investigate the thermo-mechanical bending wave propagation of porous functionally graded embedded nanoplates in thermal and magnetic fields. The wave propagation equation is derived using Hamilton's principle, including the external forces from the thermal, Lorentz, and viscoelastic medium. The porosity in the nanoplate was considered with four different models due to its ceramic and metal composition. All of the factors influencing the bending wave propagation properties of the nanoplate, such as the porosity density (volume fraction) and its dispersion form, magnetic field intensity, thermal load, and the visco-elastic foundation stiffnesses, have been thoroughly investigated. This study demonstrated that the magnetic field's strength and visco-elastic bases could be used to control the frequency, wave propagation, and phase velocity properties of porous nanoplates exposed to thermal loads. These findings will aid in the precise design of nanosensor systems that can withstand extreme temperature differences in aerospace applications while performing their intended functions.Öğe Thermomechanical vibration and buckling response of magneto-electro-elastic higher order laminated nanoplates(Elsevier Science Inc, 2023) Ozmen, RamazanThis study investigated the free vibration and buckling behavior of a magneto-electroelastic (MEE) sandwich porous nanoplate under nonlinear thermal loads and electric and magnetic potentials. The equation of motion of the nanoplate consisting of barium-titanate and cobalt-ferrite components, with a functionally graded (FG) porous core and two face plates, was modeled by a sinusoidal higher-order shear (SHSDT) and the nonlocal strain gradient (NSGT) theories. Due to the significant effect of the temperature in the dynamics of the magneto-electro-elastic nanoplate, the temperature-dependent material properties of barium-titanate (BaTiO3) and cobalt ferrite (CoFe2O4) were defined and applied to the modeling for the first time in the literature. The laminated plate consists of upper and lower surface auxiliary plates and a main FG core plate. The core plate consists of functionally grading cobalt-ferrite and barium-titanate, while face plates can be in three different material compositions consisting of pure cobalt-ferrite, pure barium-titanate, or a combination of the two. It has been shown in this study that the dynamic behavior of the core plate, exposed to high temperatures, can be controlled through auxiliary surface plates. Especially in nanosensor applications, the disadvantage of thermal load can be reduced by the electric and magnetic field's strength applied to the surface plates. This study will make an essential contribution to the design and application of nanosensor or nanoelectromechanical systems, especially by controlling nanosensor responses in high-temperature applications.& COPY; 2023 Elsevier Inc. All rights reserved.Öğe Thermomechanical vibration and buckling response of nonlocal strain gradient porous FG nanobeams subjected to magnetic and thermal fields(Taylor & Francis Inc, 2024) Ozmen, Ramazan; Kilic, Recep; Esen, IsmailThis study investigates the free vibration and thermal buckling behavior of functionally graded porous nanobeams in magnetic and thermal fields using high-order trigonometric shear stress and nonlocal strain gradient elasticity theories. The results demonstrated the effects of nonlocal differential and strain gradient elasticities on softening and stiffness enhancements, respectively. Additionally, the Lorentz force induced by the magnetic field makes nanobeam's vibratory motion difficult, causing the natural frequencies to increase. This situation can contribute to the dynamic stability of nanobeams exposed to the nonlinear temperature distribution. This study's results will assist in designing and implementing micro/nanoelectromechanical systems.
