In this thesis, effects of sonic lateral jets on aerodynamics of missiles and missilelike geometries are investigated numerically by commercial Computational Fluid Dynamics (CFD) software FLUENT. The study consists of two parts. In the first part, two generic missile-like geometries with lateral jets, of which experimental data are available in literature, are analyzed by the software for validation studies. As the result of this study, experimental data and CFD results are in good agreement with each other in spite of some discrepancies. Also a turbulence model study is conducted by one of test models. It is also found out that k-&epsilon / turbulence model is the most suitable model for this kind of problems in terms of accuracy and ease of convergence. In the second part of the thesis, parametric studies are conducted on a generic supersonic missile, NASA TCM, to see the effect of jet parameters on missile and component force and moments in pitch plane. Variable parameters are jet location, jet mass flow rate and angle of attack. As a result, it was found out that downstream influence zone of jet exit is more than the upstream influence zone. Normal force occurring by the interaction of the free stream and jet plume are amplified whenever the jet exit is located between lifting surfaces. Greater pitching moments are obtained when the jet exit moment arm with respect to moment reference center or jet mass flow rate is increased.

Different contact surface parameters and operating characteristics are observed during the deep drawing process. It is not possible to find a formulation that can be used for all lubrication regimes. Therefore, several friction models have been developed in order to overcome this problem. In this study, a math program is developed which combines Wilson&rsquo / s and Khonsari&rsquo / s friction models in a new model in order to increase accuracy and efficiency in friction calculations. By comparing the results of both friction models, the film thickness ratio of 0.035 is introduced for 0.15 &mu / m standard deviation of surface summits. Below the ratio of 0.035, Khonsari&rsquo / s model gives more accurate results since asperity friction is dominant and the model is based on asperity contact. Above the ratio of 0.035, Wilson&rsquo / s model gives more accurate results since hydrodynamic friction is dominant and the model is based on lubricant flow. In this study, a finite element program is used to simulate 50 mm cylindrical and 50.5x50.5 mm square shallow drawing processes which are performed in single stage. The final cup depths are selected as 18 mm and 23 mm for square and cylindrical cup drawing respectively. The FEM model and the program codes developed are verified by the previous studies in literature. After verification, the simulation results of the cylindrical and square cup drawing are input to a math program which calculates local friction coefficients using the combined friction model. Finally, the combined friction model and the results are further discussed.

In order to understand flow characteristics inside a positive displacement pump, every point in the flow field must be carefully observed. Such observations are difficult, expensive and usually time consuming to achieve with physical testing. During tests one can observe flow characteristics only at the locations where the instrument device is attached, not the whole flow domain. This thesis mainly focuses on the evaluation of design and performance characteristics of a positive displacement triplex diaphragm pump. For this purpose not only numerical investigations but also experimental studies were conducted using a positive displacement pump which is supplied by the pump manufacturer and is available in the fluid mechanics laboratory of Middle East Technical University. The effect of valve characteristics on the pump efficiency such as valve spring stiffness, valve displacement, mass of the check valves, and diaphragm shape are investigated in this thesis by using CFD (Computational Fluid Dynamics) technique. The pump performance is analyzed in terms of its volumetric and hydraulic efficiencies. The effect of the valve closure delay is also discussed. After the CFD and experimental results of the current pump model are compared and it is seen that they are in close agreement with each other, parametric studies are performed in computer environment. From analysis results it is observed that using stiffer springs reduces valve closing time and tend to decrease flow reversal effects. Secondly, using heavier check valves increases valve closing and opening times and also increases the stresses on the components of the pump with the increased pressure drop through discharge valve. As a result of this condition, hydraulic and volumetric efficiency reduce. Thirdly, with the longer valve displacement arrangement, more time is required for opening and closing of the check valves therefore efficiency of the pump reduces.

Launchers are military systems that are responsible for communication with munitions, safe seperation and aiming of rockets and missiles to the target. Since they are military equipments, they are used in harsh environments. One of the most important design considerations for military equipment is its maintability and one of the most important parameter which affects the maintability is wear in launchers. Therefore, for predicting the life-time of a launcher, wear should be investigated beside other parameters such as fatigue etc. This thesis study includes experimental and modeling study about dry sliding wear in some mechanical parts of a typical rail launcher that is used in helicopters. Firstly, measurements about the material loss, which is generated during firing of missiles, were made on launcher components which have interfaces with missile. Then, these results were used to simulate the wear phenomenon by using a commercial finite element program, ANSYS. By the help of finite element model, crack initiation period depending on wear is tried to be evaluated without making additional firing tests.

Modern battle tanks are equipped with gun stabilization systems using gyro and encoder data to stabilize the gun barrel, although these systems are very sensitive and reliable, these systems assume the gun barrel as a rigid beam, and do not use information from

In this thesis, firstly, the equilibrium adsorption capacity of water on a natural zeolite at several zeolite temperatures and water vapor pressures has been experimentally determined for adsorption and desorption processes. Additionally, the modified Dubinin-Astakhov adsorption equilibrium model has been fitted to experimental data and separate correlations are obtained for adsorption and desorption processes as well as a single correlation to model both processes. Experimental results show that the maximum adsorption capacity of natural zeolite is nearly 0.12 kgw/kgad for zeolite temperatures and water vapor pressures in the range 40-150 C and 0.87-7.38 kPa. Secondly, a thermally driven adsorption cooling prototype using natural zeolite-water as working pair has been built and its performance investigated experimentally at various evaporator temperatures. Under the experimental conditions of 45 C adsorption, 150 C desorption, 30 C condenser and 22:5 C, 15 C and 10 C evaporator temperatures, the COP of the adsorption cooling unit is approximately 0.25 and the maximum average volumetric specific cooling power density (SCPv) and mass specific cooling power density (SCP) of the cooling unit are 5.2 kWm-3 and 7 Wkg-1, respectively. Thirdly, in order to investigate the dynamic heat and mass transfer behavior of the adsorbent bed of an adsorption cooling unit, a transient local thermal non equilibrium model that accounts for both internal and external mass transfer resistances has been developed using the local volume averaging method. Finally, the influence of several design parameters on the transient distributions of temperature, pressure and amount adsorbed inside the cylindrical adsorbent bed of an adsorption cooling unit using silica-gel/water have been numerically investigated for the one and two dimensional computational domains. Moreover, validity of the thermal equilibrium model assumption has been shown under the given boundary and design conditions. Generally, for the conditions investigated, the validity of the local thermal equilibrium and spatially isobaric bed assumptions have been confirmed. To improve the performance of the bed considered, eorts should be focused on reducing heat transfer resistances and intra-particle mass transfer resistances but not inter-particle mass transfer resistances.

A dynamically dexterous legged robot platform generates specific acoustic signals during the interaction with the ground and the environment. These acoustic signals are expected to contain rich information that is related to the interaction surface as a function of the position of the legs and the overall contact process mixed with the actuator sounds that initiate the movement. As the robot platform walks or runs in any environment, this convolved acoustic signal created can be processed and analyzed in real time operation and the interaction surface can be identified. Such an utilization of acoustic data can be possible for various indoor and outdoor surfaces and with this can be useful in adjusting gait parameters that play an essential role in dynamic dexterity. In this work, surface type identification is achieved with using the several popular signal processing and pattern classification methods not on the robot platform but off-line. The performances of the selected features and the algorithms are evaluated for the collected data sets and these outputs are compared with the expectations. Depending on the off-line training and experiment results, the applicability of the study to an embedded robot platform as a future application is found quite feasible and the surface type as an input to the robot sensing is expected to improve the mobility of the robot in both indoor and outdoor environment.

Dental implant is an artificial dental root that is used to construct dental restorations, similar to the original teeth, in order to regain the function of missing teeth of patients experiencing tooth loss. At the interface between the jawbone and the roots of natural teeth, a thin, elastic, shock absorbing tissue, called the periodontal ligament (PDL), forms a cushion which provides certain mobility to the natural teeth. The restorations supported by dental implants, however, involve completely rigid structures. This causes overloading of the implant while bearing functional loading together with neighboring natural teeth, which leads to high local stresses within the implant system and in the jawbone. The aim of this thesis study was to develop a novel dental implant model involving resilient components in the upper structure (abutment) in order to mimic the mechanical behavior of the PDL. Within the scope of the study, a complete mechanical design of a new dental implant model was made. The proposed model was optimized based on the design objectives by using Finite Element Method. The optimal design was verified to overcome the problem of loosening of the abutment screw (a common complication in previous designs), yield very similar axial mobility behavior as that of a natural tooth and withstand biomechanical loads without failure. In addition, as a support of a dental bridge in combination with a natural tooth, the proposed design was demonstrated to provide uniform load sharing with the natural tooth and substantially reduced magnitude of peak stresses within the construction, compared to a rigid counterpart.

Although a component satisfies all operating static requirements, failures can still occur due to vibration induced fatigue. Vibration induced fatigue is a frequent phenomenon, in cases where the natural frequencies of the structures are excited by the loading. Hence, the methods which consider all dynamic characteristic of the structure should be used to obtain accurate fatigue life predictions. These methods in frequency domain are called vibration fatigue methods which give accurate, reliable and fast results. In this thesis, a numerical code is developed in order to predict fatigue life of structures and it is used for a bracket that is installed on an air platform. However, for verification of the numerical code, a cantilever beam is used as a case study at the beginning. First, finite element model of the cantilever beam is constructed and experimental analyses are performed to verify the finite element model. Then fatigue life is calculated using the numerical code and it is verified comparing the results obtained by both commercial software and performed fatigue tests. For predicting fatigue life of the bracket, flight test is performed in order to obtain acceleration loading. Finite element modeling of bracket and verification of it by experimental analyses are performed and finally, accelerated fatigue life of the bracket is obtained by the developed numerical code, commercial software and fatigue test. It is concluded that the results obtained from the fatigue analyses and fatigue test are considerably close enough to justify that the analysis is significantly accurate.

The pitch trim actuator is a hydraulic powered electro-mechanical flight control device of UH-60 helicopters which converts a mechanical input and an electrical command into a mechanical output with trim detent capabilities. In this thesis study, pitch trim actuator is investigated and a mathematical model is developed. From these mathematical equations, the actuator is modeled in MATLAB Simulink environment. While constructing the mathematical model, pressure losses in hydraulic transmission lines and compressibility of hydraulic oil are considered. To achieve a more realistic model for valve torque motor, particular tests are carried out and the torque motor current gain and the stiffness of torque motor flexure tube and the flapper displacement are obtained. Experimental data to verify the Simulink model is acquired with KAM-500 data acquisition system. A test fixture is designed for acquiring the experimental data. This test fixture can also be used to test the pitch trim actuator during depot level maintenance and overhaul. To verify the consistency of Simulink model, acquired experimental data is implemented in Simulink environment. The output of Simulink model simulation and the experimental data are compared. The results of comparison show that the model is good enough to simulate the steady state behavior of the actuator.