Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Vibration Analysis of a Plate With Piezoelectric Layers(Izmir Institute of Technology, 2018) Ağar Demir, Nuriye; Yardımoğlu, BülentIn this thesis, vibration analyses of a rectangular plate with piezoelectric layers are studied by using ANSYS. Computer codes for various cases related with the geometry of the piezoelectric layers are developed by using ANSYS Parametric Design Language (APDL) in ANSYS with SOLID5 and SOLID45 for piezoelectric patches and plate, respectively. The effect of the piezoelectric layer on active control of vibrations of plate is investigated.Master Thesis Noise and Vibration Analysis of a Drum Brake Used in Heavy Commericial Trucks(Izmir Institute of Technology, 2018) Akdağ, Osman; Yardımoğlu, BülentHeavy commercial duty vehicles have been used to for many years. High energy dissipation is required to stop these types of vehicles. Selection of brake type is related with the brake resists to this physical and environment conditions and also comfortability of drivers and passengers. Brake squeal is the most common costumer complaint for brake systems. This problem is main interest and tackled in many ways. In this thesis, vibration characteristics of the heavy commercial duty brake system, which is a drum brake, is studied by Finite Element Method to analyze the brake squeal. Natural frequencies and mode shapes of drum and shoe which are in frictional contact are determined by using ANSYS. Block Lanczos solver is preferred for this analysis. Experimental modal tests are accomplished to compare finite element results with experimental ones. Then, the noise characteristics of the brake system are obtained by performing a series dynamometer tests. In these experiments, four parameters are selected to investigate the decreasing and eliminating the noise. The selected parameters are deceleration rate, pressure, temperature and friction coefficients. The results are presented in tables and graphs.Master Thesis Effects of Stiffeners on Vibrations of Fiber-Reinforced and Laminated Composite Shells(Izmir Institute of Technology, 2018) Sarı, Tansel; Yardımoğlu, BülentVibration characteristics of fiber-reinforced and laminated composite paraboloidal shells with stiffeners are studied by Finite Element Method. The effects of stiffeners on natural frequencies are investigated by using a developed code in ANSYS. The developed code is verified by using several case studies on special cases of the present problem due to the lack of the present case in the reachable literature. Case studies are related with determination of natural frequencies of composite square plate, composite cylindrical shell, stiffened isotropic square plate, and isotropic paraboloidal shell of revolution. Aftervalidation of the developed computer code, effects on number of stiffener and cross-section of the stiffener on natural frequencies of fiber-reiforced and laminated composite paraboloidal shells are presented.Master Thesis Modeling and Analyses of Pretwisted Beams Having Piezoelectric Smart Materials(Izmir Institute of Technology, 2017) Akari, Merve; Yardımoğlu, BülentIn this study, modeling and analyses of pretwisted beams having piezoelectric smart materials are acomplished by using Finite Element Method. A computer program is developed by using APDL (ANSYS Parametric Design Language) in ANSYS with SOLID45 and SOLID5 for pretwisted beam and piezoelectric layer, respectively. The effects of the pretwist angle on electric field are analyzed.Master Thesis Analysis of Electromechanical Behavior of Piezoelectric Smart Curved Beams(Izmir Institute of Technology, 2017) Aras, Tunç; Yardımoğlu, Bülent; Yardımoğlu, BülentIn this study, electromechanical behavior of piezoelectric smart curved beam with variable radius of curvature is investigated using Finite Element Method. Firstly, a background of beam theories is provided as well as a discussion on the history of piezoelectric materials and the development of smart beams and smart curved beams. The deformations of curved beams, the differential equations for in-plane bending of curved beam with and without piezoelectric patch are presented. Finite element modeling of smart curved beam is done using ANSYS. The mesh size correctness and numerical accuracy is controlled by an equivalent straight cantilever beam having the same length, cross-section and loaded from its tip with the same amount of force that will be applied to the curved beam model. Tip displacement comparisons are done using an analytical and finite elements approach. The model is verified by comparing the analytical results of piezoelectric constitutive equations with results of finite elements method for a rectangular prism shaped piezoelectric patch. After the verification is complete, the consequent tip displacements on x direction and generated electric fields are observed after the loads of different magnitudes applied to the tip of piezoelectric curved beam. Finally, results are discussed.Master Thesis Vibration Control of a Smart Curved Beam With Variable Curvature(Izmir Institute of Technology, 2017) Kavuncu, Ali Vâlâ; Yardımoğlu, BülentIn this study, vibration control of smart curved beam with variable curvature under in plane vibration is studied. The current problem is mathematically represented by differential eigenvalue problem with variable coefficients. Since the solution of these types of problem is based on the functions of the variable coefficients, Finite Element Method is used to reduce the differential eigenvalue problem to discrete eigenvalue problem. A computer code is developed in ANSYS to model the geometry and solve the vibration control problem by using APDL (ANSYS Parametric Design Language). Vibration control is performed by displacement feed-back algorithm. The effects of control parameters on time response are investigated.Master Thesis Dynamic Analysis of Bolted Joints Under Axial and Transverse Loads(Izmir Institute of Technology, 2016) Güler, Birtan; Yardımoğlu, BülentThroughout their lifetime, fasteners are exposed to a large number of repeated vibrations which cause self-loosening. This situation causes security problem for bolted joints. In this study, novel self-loosening formulations are derived for bolted joints. By using the solution of the differential equation of a tensioned cantilever beam under the lateral tip load and bending moment, transverse displacement distribution along the bolt axis due to the transverse excitation is obtained. Therefore, radial slip amplitudes of the all engaged threads are found by using transverse displacement distribution along the bolt axis. Finally, loosening of bolted joint due to progressive circumferential displacement is discussed.Master Thesis Design and Production of Vibration-Resistant Bolt Produced by Cold Forging(Izmir Institute of Technology, 2016) Yaldız, Gökay; Yardımoğlu, BülentThroughout their lifetime, fasteners are affected from vibrations. Thus, bolted joints have gradual loosening which causes security problems. In this thesis, improving the loosening situation of bolts under transverse vibration is studied by designing new bolt thread forms which have high vibration resistance. In the first step, the possible thread forms are drawn in 2-D and 3-D by considering the elastic contact. Secondly, static finite element simulations in contact regions are performed for different thread forms designed in the first step. After finding the thread forms within the gap tolerances between bolt and nut threads, thread rolling tools are designed and manufactured to verify them experimentally. Finally, numerous tests on transverse vibration and torque-tension are conducted to test the performance of the new thread forms.Master Thesis Dynamic Modelling and Analysis of Elevator Systems(Izmir Institute of Technology, 2016) Berber, Onur; Yardımoğlu, BülentCities began to grow unexpected size after the industrial revolution. Then, so many new problems like public health, transportation, housing, food requirement etc appeared. Those problems initiated new scientific fields. Engineering diciplines also solved some of those problems and also provided many benefit to people. Different approaches at elevator technology were effected by requirements such as hight travel distances and high load capacities. If the new elevators are compared with the old elevators, it is seen that new ones are more silent, faster, safer and even more efficient. Although the elevator technology goes further and further, its applications become more complex. In this study, in order to find the transient time response of elevator car of the most common elevator types, finite element models of them are developed in ANSYS by using APDL (ANSYS Parametric Design Language). In the analysis, acceleration and deceleration of elevator car are used as input parameters. Time response plots of elevator car are presented.Master Thesis Dynamic Analysis of Non-Circular Curved Beam Subjected To Moving Loads(Izmir Institute of Technology, 2017) Emre, Melih; Yardımoğlu, BülentIn this thesis, analysis of the dynamic responses of non-circular curved beams subjected to moving loads is studied by using ANSYS which is Finite Element software. An APDL (ANSYS Parametric Design Language) code is developed for a parabolic curved beams having fixed-fixed boundary conditions. The moving load is acted on the curved beam as a single load with constant speed during the movement of the load. First of all, the proper number of finite element used in the developed APDL code for curved beam is determined by convergence test. In order to verify the mass and stiffness matrices of the curved beam, natural frequencies are found and compared with the results available in the literature. Then, moving load algorithm used in the developed APDL code is validated by using a straight beam model which has exact solution. After validations, static deflections of curved beam under slowly moving load and dynamic deflections under moving load are presented. Finally, discussion of numerical results are given.
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