A tool path generation method for sculptured surfaces defined by triangular meshes is presented in this thesis along with an algorithm that helps determine the best type of cutter geometry to machine a specific surface. Existing tool path planning methods for sculptured surfaces defined by triangular meshes require extensive computer processing power and result in long processing times mainly since surface topology for triangular meshes is not provided. The method presented in this thesis avoids this problem by offsetting each triangular facet individually. The combination of all the individual offsets make up a cutter location surface. A single triangle offsetting results in many more triangles; many of these are redundant, increasing the time required for data handling in subsequent steps. To avoid the large number of triangles, the proposed method creates a bounding space to which the offset surface is limited. The original surface mesh describes the bounding surface of a solid, thus it is continuous with no gaps. Therefore, the resulting bounding spaces are also continuous and without gaps. Applying the boundary space limits the size of the offset surface resulting in a reduction in the number of triangular surfaces generated. The offset surface generation may result in unwanted intersecting triangles. The tool path planning strategy addresses this issue by applying hidden-surface removal algorithms. The cutter locations from the offset surface are obtained using the depth buffer. The simulation and machining results show that the tool paths generated by this process are correct. Furthermore, the time required to generate tool paths is less than the time required by other methods. The second part of this thesis presents a method for selecting an optimal cutter type. Extensive research has been carried out to determine the best cutter size for a given machining operation. However, cutter type selection has not been studied in-depth. This work presents a method for selecting the best cutter type based on the amount of material removed. By comparing the amount of material removed by two cutters at a given cutter location the best cutter can be selected. The results show that the optimal cutter is highly dependent on the surface geometry. For most complex surfaces it was found that a combination of cutters provides the best results.

The environmental and monetary cost of energy has renewed interest in horizontal-axis wind turbines (HAWT). One problem with HAWT design is turbulent winds, which cause cyclic loading and reduced life. Controlling short-term aerodynamic fluctuations with blade pitching or mechanical flaps is limited by the speed of actuation. The objective was to investigate using jet-flap-like fluidic actuators on the 'suction surface' of an aerofoil for rapid aerodynamic control. A NACA 0025 aerofoil was constructed for wind-tunnel experiments. The low Reynolds number (Re) flow was measured non-intrusively with particle image velocimetry (PIV). The jet showed limited effect compared to published work. The sharp trailing edge and distance to the jet were determined to be critical factors. At Re≈100000 the 'suction surface' jet sheet is less useful for control than the conventional 'pressure surface' sheet. The experiment suggests usage near the blade root on truncated aerofoils.

On-the-fly laser drilling provides a highly productive method for producing hole clusters (pre-defined groups of holes to be laser drilled) on freeform surfaced parts, such as gas turbine combustion chambers. Although the process is capable of achieving high throughputs, current machine tool controllers are not equipped with appropriate trajectory functions that can take full advantage of the achievable laser drilling speeds. While the problem of contour following has received previous attention in time-optimal trajectory generation literature, on-the-fly laser drilling presents different technological requirements, needing a different kind of trajectory optimization solution, which has not been studied prior to this thesis. The duration between consecutive hole locations, which corresponds to the laser pulsing period, has to be kept constant, ideally throughout the part program. However, the toolpath between the holes is not fixed and can be optimized to enable the shortest possible segment duration. To preserve the dynamic beam positioning accuracy and avoid inducing excessive vibrations on the laser optics, the axis velocity, acceleration, and jerk profiles need to be limited. Furthermore, to ensure that hole elongation does not violate the given part tolerances, the orthogonal component of part velocity relative to the laser beam needs to be capped. All of these requirements have been fulfilled in the trajectory optimization algorithm developed in this thesis. The hole locations are provided as pre-programmed sequences by the Computer Aided Design/Manufacturing software (CAD/CAM). A time-optimized trajectory for each sequence is planned through a series of time-scaling and unconstrained optimization operations, which guarantees a feasible solution. The initial guess for this algorithm is obtained by minimizing the integral square of the fourth time derivative (i.e. ‘snap’). The optimized trajectories for each cluster are then joined together or looped onto themselves (for repeated laser shots) using a time-optimized looping/stitching (optimized/smooth toolpath to repeat/loop a cluster or connect/stitch between consecutive clusters) algorithm. This algorithm also minimizes the integral square of jerk in the faster axes. The effectiveness of the overall solution has been demonstrated in simulations and preliminary experimental results for on-the-fly laser drilling of a hole pattern for a gas turbine combustion chamber panel. It is shown that the developed algorithm improves the cycle time for a single pass by at least 6% (from kinematic analysis of the motion duration), and more importantly reduces the integral square of jerk by 56%, which would enable the process speed to be pushed up further.

The aim of this essay is to illustrate a modern phenomenon, the Olympic Games, by applying the ideas of Mircea Eliade concerning space, time and myth. This literature study is mainly divided in two parts, one descriptive and one analytic. In the first part Eliade’s ideas and some criticism, which has been pointed against his theoretical approaches as well as his character, are presented. In the second part an analysis is carried out, based on the previously presented ideas and elements essential for the Olympics; the idea of the Olympics, the place, the ceremonies, the competition and the concept of individual idolism. I have discussed what seems like gnostic tendencies in Eliade’s ideas, in the sense that both Eliade’s ideas and the concept of Gnosticism argue that knowledge is a necessary condition for salvation, as well as the fact that Eliade and his ideas have not always a pro-Christian approach. I have also shown that incoherency exists in his theoretical approach concerning the manifestation of the sacred. I have found that Mircea Eliade’s ideas, with some difficulties, very well can reflect a modern phenomenon such as the Olympic Games. I have also put forth the idea of translating Eliade’s conception of axis mundi into an ideological landscape; the Olympic values become an analogy to axis mundi. Furthermore, I have also shown that modern man in different ways desires to be close to the sacred, and how this fact to some extent may explain people’s devotion to and worship of sport heroes, and thus why not only athletes but also billions of spectators are inclined to attend the Olympics. Finally, I show that, according to Eliade’s ideas, the Olympics might facilitate the process of creating modern myths.

This thesis aims to investigate the performance of a horizontal water turbine in ocean current. The design of the water turbine is based on the Blade Element Momentum theory to begin with. As the water current flows past a single turbine, the water inflow velocity and the rotational speed are the parameters to be investigated. Furthermore, the interaction of more than two turbines due to the relative distance is also discussed. The relative distance encompasses both the front and the back. The results show that the water inflow velocity and the turbine rotational speed influence the performance of the turbine. When two turbines function simultaneously, the flow field is different from the one of a single turbine and thus influences the performance of the other turbines in the vicinity. Lastly, the site arrangement of three turbines is discussed, and it is revealed that a proper arrangement can enhance the performance of the turbines.

This investigation examines a novel means of integrating high-performance AlN piezoelectric thin films with a flexible stainless steel substrate (SUS 304) to fabricate a double-sided piezoelectric transducer. Various sputtering parameters, such as sputtering pressure, substrate temperature, nitrogen concentration, and RF power, were investigated to improve the piezoelectric characteristics of AlN thin films. Scanning electron microscopy and X-ray diffraction of AlN piezoelectric film reveal a rigid surface structure and highly c-axis-preferring orientation. The maximum output power per unit thickness was discussed, and the optimal sputtering parameters were determined. The double-sided piezoelectric transducer is constructed by depositing AlN piezoelectric thin films on both the front and the back sides of SUS 304 substrate. The titanium (Ti) and platinum(Pt) layers were deposited using a dual-gun DC sputtering system between the AlN piezoelectric thin film and the SUS 304 substrate. The optimal deposition parameters for AlN thin films are sputtering pressure of 5 mTorr, substrate temperature of 300 ¢J, nitrogen concentration of 40 %, and RF power of 250 W. The maximum open circuit voltage of the transducer under the vibrational frequency of 80 Hz, vibration amplitude of 4mm, and mass loading of 0.5g, is approximately 20 V, or 5.3 V/£gm. After full-wave rectification and filtering through a 33 nF capacitor, a specific output power of 1.462 £gW/cm2 is obtained from the transducer with a load resistance of 7 M£[.

The purpose of this thesis is to study the c-axis inclined ZnO films to produce dual-mode thin-film piezoelectric transducer. The cantilever beam vibration theory as a power generation mode in adopted to verify that the transducer is in suitable for the application in the environment for low-frequency vibration. In order to develop dual-mode thin-film piezoelectric transducer, this study uses radio-frequency magnetron sputtering method with off-axis growth to deposit ZnO films on Pt/Ti/stainless steel substrate(SUS304), the effects of deposition parameters on the characteristict of ZnO films are studied. Because zinc oxide thin-film is grown with c-axis tilt, so the piezoelectric transducer exhibits longitudinal-mode and shear-mode characteristics. The physical characteristics of ZnO thin films were obtained by the analyses of the scanning electron microscopy (SEM) and X-ray diffraction (XRD) to discuss the surfaces, cross section and crystallization of ZnO thin films. Finally, the vibration test equipment in used for the measurement of electrical properties. The open and loaded voltages of the transducers were obtained by the measurement system. The optimal deposition parameters for ZnO thin films are sputtering pressure of 5 mTorr, RF power of 150W, substrate temperature of room temperature and oxygen concentration of 50%, which were determined by physical characteristics and voltage analysis. Under the optimal parameters, the ZnO thin-films are deposited with maximum shear-mode and tilting angles of 35¢X.The transducer was one-sid loaded with a piece of metal of 0.5 g load to enhance the cantilever vibration amplitude. As the input vibration of 65 Hz and vibration amplitude of 1mm were set, the maximum output power was obtained. The maximum open circuit voltage of 19.4 V was obtained. When the output of the transducers was recetified and filtered through a 1NN5711 Schottky diode bridge rectifier and a 33nF capacitor, the maximum power of 2.05£gW/cm2 was achieved with the load resistance of 5M£[.

Impellers are important components in the field of aerospace, energy technology, and precision machine industries. Considering the high accuracy and structural integrity, impellers might be manufactured by cutting. Due to their complex geometries and high degrees of interference in machining, multi-axis machines are requested to produce impellers. The object of this thesis is to improve 5-axis tool paths for surface quality of impellers by smoothing point cutting tool paths in terms of linear segments and B-Splines and by using flank milling technologies with linear segment and B-Splines tool paths. Experimental results show that the surface quality of impeller blades can be improved by point cutting with smoothed tool paths and by flank milling. Moreover, the required milling time can be reduced by 18 percent and 13percent based on smoothed linear tool paths and smoothed B-Splines tool paths, respectively.

ABSTRACT DESIGN AND CONSTRUCTION OF A SIX DEGREE OF PLATFORM G&uuml / rb&uuml / z, Sarper M.S., Department of Mechanical Engineering Supervisor: Prof. Dr. Tuna BALKAN Co-Supervisor: Prof. Dr. M. A. Sahir ARIKAN November 2006, 83 pages In this thesis a six degree of freedom (DOF) parallel manipulator is designed, developed and simulated virtually. The platform, which is specified and focused on in this thesis, is the specific solution for the generating the required data to simulate a land, airborne or sea vehicle&amp / #8217 / s motion trajectory in the laboratory environment. After explaining the need for such platforms for the military industry, the existing devices will be presented and discussed. Then the design period will be explained while pointing out the key performance criteria. The gathered performance values of the first design iteration will be presented and the modifications done in order to get to the expected performance will be given. Finally an investigation, in order to find the maximum payload that the platform can handle, is performed and presented. It is too hard to get to the desired performance values in mechanical design and manufacturing without using the CAD (Computer Aided Design) and CAM (Computer Aided Manufacturing) programs. In this thesis ProEngineer Wildfire&reg / is used for solid modeling the components, the sub-assemblies and the final assembly, ANSYS Workbench&reg / is used for investigating the modal behavior of the components, ADAMS&reg / 2003 is used for the dynamic simulation of the mechanism, ADAMS/Flex&reg / , ADAMS/AutoFlex&reg / and ADAMS/Durability&reg / are used to analyze the results when flexibility is embedded into the system. At the end of the thesis in Appendix section five technical drawings with the nominal dimensions are given in order to clarify the construction period. By the regulations that must be obeyed in ASELSAN only the nominal dimensions are given in the technical drawings. All the dimensional and geometrical tolerances are given in the approved technical drawings that are proprietary of ASELSAN. Keywords: 6-Axis Motion Platform, Application of CAD and analysis programs, Electromechanical Design, Stewart Platform

An aerodynamic design and optimization tool for wind turbines is developed by using both Blade Element Momentum (BEM) Theory and Genetic Algorithm. Turbine blades are optimized for the maximum power production for a given wind speed, a rotational speed, a number of blades and a blade radius. The optimization variables are taken as a fixed number of sectional airfoil profiles, chord lengths, and twist angles along the blade span. The airfoil profiles and their aerodynamic data are taken from an airfoil database for which experimental lift and drag coefficient data are available. The BEM analysis tool developed is first validated with the experimental data for low wind speeds. A 100 kW wind turbine, which is used in the validation, is then optimized. As a result of the optimization, the power production is improved by 40 to 80 percent. The optimization methodology is then employed to design a 1MW wind turbine with a 25m radius.