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Öğe Biomechanical analysis and solution suggestions of screw replacement scenarios in femoral neck fracture surgeries: Finite element method(WILEY, 2025) Güvercin, Yılmaz; Yaylacı, Murat; Dizdar, Ayberk; Özdemir, Mehmet Emin; Ay, Sevil; Uzun Yaylacı, Ecren; Karahasanoğlu, Ümitcan; Uygun, Hüseyin; Peker, GökhanObjective: Despite several surgical options, there has yet to be a consensus on the best treatment for femoral neck fracture (FNF) due to higher complication rates compared to other bone fractures. This study aims to examine the possible consequences and solution suggestions of changing screws during surgery for various reasons in FNF surgical treatment from a biomechanical perspective. Method: FNF and treatment materials were analyzed biomechanically using a package program based on the finite element method (FEM). This study created a solid model with images of femur bone tomography. Dynamic hip screws (DHS), cannulated screws (CCS), and medial buttress plates (MBP) were obtained by making three-dimensional designs. The required elements for the models were assigned, and the material properties of the elements were defined. The solutions were obtained as crack distance and deformation results after defining the boundary conditions and applying the necessary loading. Results: The strain and crack distance values created by six models on the fracture line under different parameters were obtained, and the numerical results were evaluated. The DHS and CCS models produced the highest crack distance and deformation values when all screws were loose. The lowest values were obtained in the intact-85 model when all CCS were tight. When the results are evaluated, it is seen that the MBP has a decreasing effect on the results. Mechanical evaluation of six different options used in femoral neck fractures was performed. 85 mm CCS applied to our standard model gave the best results, while the use of 80 mm CCS in the same model showed promising results compared to other models. It is understood that CCS have the best stability even in loosening models with the medial support plate. Different models are from intact-85 mm DHS+1CS+MBP to DHS+1CS, which was worked with LSR+USR-2, according to decreasing stability. Conclusion: This study offers various biomechanical solutions to possible intraoperative problems in FNF treatment. The following results were obtained from the study data. When the CCS needs to be lengthened or replaced, it is appropriate to use the CCS with the MBP. A single anti-rotation screw is sufficient for lag screw extensions of the DHS plate, and the MBP may be a savior procedure in surgery.Öğe Biomechanical analysis of odontoid and transverse atlantal ligament in humans with ponticulus posticus variation under different loading conditions: finite element study(Elsevier, 2022) Güvercin, Yılmaz; Yaylacı, Murat; Dizdar, Ayberk; Kanat, Ayhan; Uzun Yaylacı, Ecren; Ay, Sevil; Abdioğlu, Ahmet Atilla; Şen, AhmetPurpose: Ponticulus posticus (PP) is a variation of the bone bridge that appears in the first cervical vertebra and through which the vertebral artery passes. Odontoid fractures are common spinal bone fractures in older people. This study aims to investigate the effect of neck movements on the odontoid and transverse atlantal ligament (TAL) of people with PP variation from a biomechanical view. Method: C1, C2, and C3 vertebrae of the occipital bone were analyzed using the finite element method (FEM). In this study, solid models were created with the help of normal (N), incomplete (IC), and asymmetric complete (AC) PP tomography images. The necessary elements for the models were assigned, and the material properties were defined for the elements. As boundary conditions, models were fixed from the C3 vertebra, and 74 N loading was applied from the occipital bone. Stress and deformation values in the odontoid and transverse atlantal ligament were obtained by applying 1.8 Nm moment in flexion, extension, bending, and axial rotation directions. Results: The stress and deformation values of all three models in odontoid and TAL were obtained, and numerical results were evaluated. In all models, stress and deformation values were obtained in decreasing order in rotation, bending, extension, and flexion movements. The highest stress and strain values were obtained in AC and the lowest values were obtained in N. In all movements of the three models, the stress and deformation values obtained in the TAL were lower than in the odontoid. Conclusion: The greatest stresses and deformations obtained in spines (AC) with PP were found in the odontoid. This may help explain the pathogenesis of odontoid fractures in older people. First, this study explains the mechanism of the formation of neck trauma in people with PP and the need for a more careful evaluation of the direction of impact. Secondly, the study reveals that the rotational motion of the neck independent of PP has more negative effects on the odontoid.Öğe Examination of the impact of lignin sulfonate based structure chemicals on fresh and hardened concrete(Pamukkale University, 2016) Ekinci, Cevdet Emin; Ay, Sevil; Baykuş, Nurdan; Ay, AdemIn this study, the impact of the addition of lignin sulfonate based chemicals on the properties of fresh and hardened concrete were examined. For C25/30 and C20/25 target class concretes, cement and chemical additive amounts were constant; changes were made only to water and aggregate amounts. Compressive strength values of the concretes were taken on the 1st, 7th and 28th days. Increases of compressive strength values were observed on days 1, 7, and 28. In the 1st study, in which C25/30 strength class was targeted for Cem I 42.5 R type cement provided by firm CF1, it was revealed that a 10.8% decrease in mixed water amount may occur. In the 2nd study, in which C20/25 strength class was targeted for Cem II 32.5 N type cement provided by firm CF2, it was revealed that a minimum 8.1% decrease may occur. In conclusion, although changes to viscosity, heat and unit weight of fresh concrete are caused by usage of lignin sulfonate based chemicals, they had no adverse effect on compressive strength of the concrete in this study.Öğe Examining the contact problem of a functionally graded layer supported by an elastic half-plane with the analytical and numerical methods(John Wiley and Sons Ltd, 2024) Yaylacı, Murat; Yaylı, Müjgen; Öztürk, Şevval; Ay, Sevil; Özdemir, Mehmet Emin; Uzun Yaylacı, Ecren; Birinci, AhmetThis study offers a comparative study of the analytical and numerical methods for investigating a contact problem. The contact problem comprises a functionally graded layer supported by a half-plane and loaded with a distributed load from the top surface. First, the analytical and numerical solutions to the problem are acquired by utilizing a theory of elasticity and finite element method, respectively. The problem is transformed into a system of integral equations in which the contact stress is an unknown function. The solution of the integral equation was achieved with Gauss–Jacobi integration formulation. The finite element model of the problem is created using ANSYS software, and the two-dimensional analysis of the problem is performed. Results were obtained from the samples for different material properties and loading conditions. The distributed load width and non-homogeneity parameters significantly impact on contact mechanics. The results indicate that the contact area and the contact stress obtained from finite element method (FEM) are close to the analytical results. As a result, acceptable error rates were obtained. Finally, this study provides evidence of a good agreement between the two methods.Öğe Implementation of finite element and artificial neural network methods to analyze the contact problem of a functionally graded layer containing crack(TECHNO-PRESS, 2022) Yaylacı, Murat; Uzun Yaylacı, Ecren; Özdemir, Mehmet Emin; Ay, Sevil; Özturk, SevvalIn this study, a two-dimensional model of the contact problem has been examined using the finite element method (FEM) based software ANSYS and based on the multilayer perceptron (MLP), an artificial neural network (ANN). For this purpose, a functionally graded (FG) half-infinite layer (HIL) with a crack pressed by means of two rigid blocks has been solved using FEM. Mass forces and friction are neglected in the solution. Since the problem is analyzed for the plane state, the thickness along the z-axis direction is taken as a unit. To check the accuracy of the contact problem model the results are compared with a study in the literature. In addition, ANSYS and MLP results are compared using Root Mean Square Error (RMSE) and coefficient of determination (R2), and good agreement is found. Numerical solutions are made by considering different values of external load, the width of blocks, crack depth, and material properties. The stresses on the contact surfaces between the blocks and the FG HIL are examined for these values, and the results are presented. Consequently, it is concluded that the considered non-dimensional quantities have a noteworthy influence on the contact stress distributions, and also, FEM and ANN can be efficient alternative methods to time-consuming analytical solutions if used correctly.Öğe Research of the crack problem of a functionally graded layer(Techno-Press, 2024) Yaylacı, Murat; Uzun Yaylacı, Ecren; Turan, Muhittin; Özdemir, Mehmet Emin; Öztürk, Şevval; Ay, SevilIn this study, the two-dimensional crack problem was investigated by using the finite element method (FEM)based ANSYS package program and the artificial neural network (ANN)-based multilayer perceptron (MLP) method. For this purpose, a half-infinite functionally graded (FG) layer with a crack pressed through two rigid blocks was analyzed using FEM and ANN. Mass forces and friction were neglected in the solution. To control the validity of the crack problem model exercised, the acquired results were compared with a study in the literature. In addition, FEM and ANN results were checked using Root Mean Square Error (RMSE) and coefficient of determination (R2), and a well agreement was found. Numerical solutions were made considering different geometric parameters and material properties. The stress intensity factor (SIF) was examined for these values, and the results were presented. Consequently, it is concluded that the considered non-dimensional quantities have a noteworthy influence on the SIF. Also FEM and ANN can be logical alternative methods to time-consuming analytical solutions if used correctly.
