This study describes the process of performing structural optimization using ANSYS. In the first part, the general concepts in optimization and optimization algorithms for different type of optimization problems are covered. Also finite element method is introduced briefly in this part. In the second part, important definitions in structural optimization are mentioned. Then the optimization methods available in ANSYS are explained with their theories. Necessary steps to perform optimization with ANSYS are described at the end of this part. In the next part, sample problems found from scientific papers are solved using ANSYS and the results are compared. At the end of the study, the results obtained from the example problems are discussed whether they came out as expected or not. Also conclusions are made about solving optimization problems and performing structural optimization with ANSYS.

In this study, an ignition unit was designed and constructed for a new design engine with eight cylinders and sixteen pistons. The ignition coils with two high voltage outputs were used to ignite sixteen spark plugs on the system. They were driven by PIC16F628A based igniter circuits triggered with digital signals. The igniter circuits receive ignition signals in a square wave form from a main control circuit / they open or close primary voltage of the induction coils to ignite spark plugs. This main control circuit is based on PIC16F877A / and there are two of them. The duty of main control circuit is to determine ignition advance according to engine speed and cooling water temperature, and send proper ignition signals to the igniter circuits. This main control circuit receives engine speed from the other main circuit (secondary control circuit) with serial communication and reads cooling water temperature and then it reads advance value from external eeprom memory according to engine speed and temperature. The main control circuit receives cylinder position signals from the secondary control circuit and adds advance value on them to form ignition timing signals which triggers igniter circuits. The secondary control circuit reads engine speed and determines cylinder positions with two magnetic pick-ups and LM2907 circuits on a gear wheel. This gear wheel was used to simulate disks on the crank shaft of the cars, and driven with an electric motor. The ignition unit was tested for different engine speeds, and its proper working was proved.

In this thesis, rapid transfer alignment algorithm for a helicopter launched guided munition is studied. Transfer alignment is the process of initialization of a guided munition&rsquo / s inertial navigation system with the aid of the carrier platform&rsquo / s navigation system, which is generally done by comparing the navigation data of missile and carrier&rsquo / s navigation data. In the literature, there are different studies of transfer alignment, especially for aircraft launched munitions. One important problem in transfer alignment is the attitude uncertainty of lever arm between munition&rsquo / s and carrier&rsquo / s navigation systems. In order to overcome this problem, most of the studies in the literature do not use carrier&rsquo / s attitude data in the transfer alignment, only velocity data is used. In order to estimate attitude and related inertial sensor errors, specific maneuvers of carrier platform are required which can take 1-5 minutes. The purpose of this thesis is to compensate the errors arising from the dynamics of the Helicopter, lever arm, mechanical vibration effects and inertial sensor error amplification, thus designing a transfer alignment algorithm under real environment conditions. The algorithm design begins with observability analysis, which is not done for helicopter transfer alignment in literature. In order to make proper compensations, characterization and modeling of vibration and lever arm environment is done for the helicopter. Also, vibration based errors of MEMS based inertial sensors are experimentally shown. The developed transfer alignment algorithm is tested by simulated and experimental data

Skid-steer loaders are also called mini loaders. Skid-steer loaders are capable of zero turning radiuses, which make them extremely maneuverable and suitable for confined spaces. The aim of this thesis study is to design the loader mechanism for skid-steer loaders. Primarily, the loader mechanism synthesis will be performed to determine the basic link dimensions for the mechanism of the loader. Genetic algorithm will be used in the design process. Besides, the hydraulic cylinders dimensions and working pressure of the loader mechanism will be chosen according to the forces that will be applied. After the link dimensions of the loader are determined, 3D modeling of the loader mechanism will be performed. Afterwards, the finite element analysis of the system will be carried out. Finally, improvements will be made on the model according to the results of the analysis.

The aim of this thesis is to investigate buckling, post-buckling behaviors and failure characteristics of composite laminated plates under compressive loading with the help of finite element method and experiments. In the finite element analyses, eigen value extraction method is used to determine the critical buckling loads and nonlinear Riks and Newton-Raphson methods are employed to obtain post-buckling behaviors and failure loads. The effects of geometric imperfection amplitude on buckling and post-buckling are discussed. Buckling load, post buckling loaddisplacement relations, out of plane displacements and end shortening of the plates are determined numerically. Furthermore, the numerical results are compared with experimental findings for two different laminates made of woven fabric and unidirectional tapes where buckling, post-buckling behavior and structural failure of laminated plates were determined. The comparisons show that there is a good agreement between numerical and experimental results obtained for buckling load and post-buckling range. However, 15 % - 22 % differences are predicted between the experimental and numerical results for failure of laminates made of woven fabric whereas the laminates with uni-directional tapes show good agreement.

Missile navigation systems rely on hybrid INS/GPS systems to employ lower grade inertial sensors for the sake of cost and availability. Current inertial navigation systems on missiles can perform accurately for a limited time without GPS aiding. However, GPS is the most likely system that is going to be jammed in a crisis or war by low cost jammers by any opposing force. Missiles do not have adequate equipment to maintain accuracy when GPS is jammed completely in the battle area. In this thesis, a new method is proposed to improve performance of INS systems onboard missiles and autonomous aerial vehicles with EO sensors in a GPS denied environment. Previously laid ground based beacons are used by the missile EO/IIR seeker for bearing-only measurements and position updates are performed by the use of modified artillery survey algorithms based on triangulation techniques which involve angle measurements. For mission planning, two main problems are identified as deployment problem and path planning problem and a tool for the optimal laying of beacons for a given desired trajectory and optimal path planning for a given network of beacons is developed by using evolutionary algorithms and results for test scenarios are discussed.

Mobile robots are commonly used to achieve tasks involving tracking a desired trajectory and following a predefined path in different types of terrains that have different surface characteristics. A mobile robot can perform the same navigation task task over different surfaces if the tracking performance and accuracy are not essential. However, if the tracking performance is the main objective, due to changing the characteristics of wheel-ground interaction, a single set of controller parameters or an equation of motion might be easily failing to guarantee a desired performance and accuracy. The interaction occurring between the wheels and ground can be integrated into the system model so that the performance of the mobile robot can be enhanced on various surfaces. This modeling approach related to wheel-ground interaction can also be incorporated into the motion controller. In this thesis study, modeling studies for a two wheeled differential drive mobile robot and a steerable four-wheeled robot vehicle are carried out. A strategy to achieve better tracking performance for a differential drive mobile robot is developed by introducing a procedure including the effects of external wheel forces / i.e, traction, rolling and lateral. A new methodology to represent the effects of lateral wheel force is proposed. An estimation procedure to estimate the parameters of external wheel forces is also introduced. Moreover, a modeling study that is related to show the effects of surface inclination on tracking performance is performed and the system model of the differential drive mobile robot is updated accordingly. In order to accomplish better trajectory tracking performance and accuracy for a steerable four-wheeled mobile robot, a modeling work that includes a desired trajectory generator and trajectory tracking controller is implemented. The slippage is defined via the slip velocities of steerable front and motorized rear wheels of the mobile robot. These slip velocities are obtained by using the proposed slippage estimation procedure. The estimated slippage information is then comprised into the system model so as to increase the performance and accuracy of the trajectory tracking tasks. All the modeling studies proposed in this study are tested by using simulations and verified on experimental platforms.

Ground-borne vibrations from railway systems not only pose threats to structural integrity of nearby buildings and cause annoyance on people but also contribute into environmental noise levels. It is of utmost importance to predict these vibrations at the design stage of such systems. This thesis attempts to reach this goal through finite elements analysis. Commercial software is used to develop a finite element model of an existing railway system. The model is based on the work of Forrest and Hunt [11]. It is also aimed to perform transient analysis in time domain to complement vibration information already obtained in frequency domain. The model is validated by checking maximum element size and comparing results with the infinite boundary condition case. Parametric studies are designed to investigate effects of soil type, railpad type and train speed on vibrations induced by underground train traffic. Results acquired through the finite element analysis are found to be in good harmony with the ones by existing numerical methods. The study demonstrates that the approach can be applied to predict ground-borne vibration from any configuration of railway systems.

Compressed air is widely used particularly in industry. In order to increase the quality of the process and lifetime of the machine, the compressed air should be dried. Therefore the air is used after compression and drying processes. The most commonly used machines that do this process are called &ldquo / Refrigerant Air Dryers&rdquo / . These air dryers are designed to cool and dehumidify the moist air. The process of decreasing temperature is carried out by a refrigerant, R134a. Unlike design conditions, dryers are working in variable loads (variable compressed air flow rates). An experimental setup is prepared for analyzing the variance on the machine and the performance under these variable loads. This thesis includes the design, preparation and the modification of the refrigeration experimental setup for refrigerant air dryers. The setup is tested under three different conditions and the results are compared.

ABSTRACT FINITE ELEMENT ANALYSIS OF CORNERING CHARACTERISTICS OF ROTATING TIRES ErSahin, Mehmet Akif Ph. D., Department of Mechanical Engineering Supervisor: Prof. Dr. Y. Samim &Uuml / nl&uuml / soy September 2003, 157 pages A finite element model is developed to obtain the cornering force characteristics for rotating pneumatic tires which combines accuracy together with substantially reduced computational effort. For cord reinforced rubber sections such as the body plies and breaker belts, continuum elements with orthotropic material properties are used to improve solution times. Drastic reductions in computational effort are then obtained by replacing the continuum elements with truss elements which do not require orientation of element coordinate system to model textile body plies. With these simplifications, new model can be used produce a complete carpet plot of cornering force characteristics in substantially reduced solution times. The finite element model is used to obtain the cornering force characteristics of a tire, simulating the experiments on a tire test rig where the tire rotates on a flywheel. Results from both models are compared with each other and with the experimental results. It is concluded that the model developed provides results at least as accurate as the previously published models with a clear superiority in stability of solution.