The purpose of this thesis is to search for the best material model for soft biological tissues in general. Different sections of human body exhibit different responses like stress relaxation, creep, hysteresis and preconditioning to external loading conditions. These body sections can be assumed as viscoelastic, poroelastic or pseudoelastic. After making the choice of the material model from one of these for the current study, the finite element model and the material code to be used with this model have been created. The material code has also been tried on a simple finite element model before implementing to the real model to prove the fact that it is working properly. Then, the constants in the code which simulates the in vivo experimental data that was obtained by indenting the elliptic indenter tip into the forearm, medial part as close as possible, have been derived by inverse finite element method. Consequently, the characteristic behaviors of the soft tissue could be simulated. Despite the big size of the finite element model and very long submission times (up to one day for preconditioning simulation), relaxation and creep behaviors could be simulated with the maximum normalized sum of square errors of 0.74 % and 0.43 %, respectively. The number of square errors for the hysteresis and preconditioning behaviors appeared as 2.56 % and 3.89 % which are also acceptable values. These values prove that these material models are well suited for the simulation of the behavior of soft biological tissues. By using different experimental data obtained from other sections of human body, simulation of the behavior of different soft tissues can be achieved by using these material models.

Today, energy has become one of the most indispensable necessities in the world. Most of the wars and the disputes between the countries have been arising because of the increasing scarcity of energy resources. Therefore, like most country, Turkey has also started to develop new energy policies for more efficient production and utilization of energy. In order to help the understanding of more efficient energy utilization, so far there have been some researches made about energy and exergy (available energy) utilization efficiencies of Turkey with the viewpoint of the quality of energy. In this study, it is aimed to examine energy system of Turkey by computing energy and exergy utilization efficiencies between 1990 and 2006 using the first and the second laws of thermodynamics. The utility sector energy efficiencies are found to range from 41% to 47% and the exergy efficiencies to range from 42% and 48% between 1990 and 2006. The energy efficiencies of the end use sectors of Turkey , namely Industrial, Transportation, Agricultural and Residential-Commercial sectors, are respectively 62%, 22%, 27% and 55% on the average with respect to years. On the other hand, their average exergy efficiencies are 33%, 23%, 27% and 7% between the examined years. The total end use energy and exergy efficiencies are 49% and 21% on the average. Overall energy efficiencies of Turkey range between 37% and 41%, whereas overall exergy efficiencies range between 16% and 17%. Within all the sectors, Residential&ndash / Commercial sector is found as the sector having the highest exergetic improvement potential.

The objective of the present work is to investigate the behavior of laminated fiber -reinforced polymer matrix composite shell structures under bending load with the help of a modified finite element computer code which was previously developed for the analysis of pseudo-layered single material shells. The laminates are assumed to be orthotropic and the formulation is adapted to first order shear deformation theory. The aim is to determine the large deformation characteristics numerically, and to predict the modes of failure by the illustration of the critical elements of the model. Therefore, several failure theories are also integrated to the code to detect first ply failure. Triangular shell elements are used and all the related data are generated from the mid-plane. Laminates under transverse loading are analyzed through several boundary conditions and ply orientations. To verify the numerical results obtained, a commercial finite element program is used to compare the outputs of the study, and the comparison is found to have shown good agreement. The onset of damage is investigated by using different failure criteria consisting of maximum stress, Tsai-Wu, and Tsai- Hill theories and close results are obtained.

In this study, a design procedure incorporating a genetic algorithm (GA) is developed for optimization of the wing structure of a two seated trainer aircraft with single turboprop engine. The objective function considered is the total weight of the structure. The objective function is minimized subjected to certain strength requirements. In order to evaluate the design constraints and model the wing structure, finite element analysis is performed by using a conventional finite element solver (i.e. MSC/NASTRAN&reg / ). In addition, MSC/PATRAN&reg / commercial package program is used as preprocessor and postprocessor tool. VISUAL FORTRAN programming language is also utilized as the genetic algorithm implementation tool. Several conclusions drawn from the optimization results are presented.

Soft biological tissues, being live and due to their physiological structures, display considerably complex mechanical behaviors. For a better understanding and use in various applications, first study to be carried out is the tests made particularly as in vivo. An indenter test device developed for this purpose in the METU, Department of Mechanical Engineering, Biomechanics Laboratory is operational. In this study, in order to carry out precise and dependable tests, initially, various tests and improvements were conducted on the device and the software controlling the device. At the end of this study, displacement and load measurement accuracies and precisions were improved. Better algorithms for filtering the noisy data were prepared. Some test protocols within the software were improved and new protocols were annexed. To be able to conduct more dependable tests a new connection system was attached to the device. In order to study the anisotropic behavior of soft tissues ellipsoid tips were designed and produced. In the second phase of the study, tests on medial forearm were carried out. In these tests, hysteresis, relaxation and creep behaviors displaying the viscoelastic v properties of the soft biological tissues were observed. In addition to viscoelastic behaviors, preconditioning (Mullin&amp / #8217 / s) effect and anisotropic response were examined. By using the results of the relaxation and creep tests, parameters of the Prony series capable of modelling these data were determined. With this study, some important conclusions regarding the soft biological tissues were drawn and thus the behaviors of the soft biological tissues were better understood. Besides, the difficulties inherent to in-vivo tests were recognized and actions to reduce these difficulties were explained. Finally, clean experimental data, to be used in the computer simulations, were obtained.

In this study a centrifugal fan is studied for noise characteristics and measurements in a semi- anechoic room. A semi-anechoic room is constructed inside Fluid Mechanics Laboratory of Mechanical Engineering Department has been qualified with respect to ISO 3745 standard. The fan characteristic is obtained as proposed in AMCA standards 210-75, by simply measuring the voltage and current of the motor during operation and calculating the power consumption of the assembly. Noise measurements are taken using two microphones attached to a multi-channel data acquisition and processing system in the semi anechoic room. Several different configurations of the vacuum cleaner with some parts removed or replaced systematically are considered during the noise measurements. Some of the results showed that the damping material placed inside the motor cover is proved to be very effective in noise reduction. Two different damping materials are examined for comparative evaluation.

Micro-perforated sound absorbers with sub-millimeter size holes can provide high absorption coefficients. Various types of micro-perforated absorbers are now available in literature for different applications. This thesis presents results of work on the development of an effective single layer micro-perforated sound absorber from the commercial composite material Parabeam with micro diameter holes drilled on one side. Parabeam is used as a structural material made from a fabric woven out of a E-glass yarn and consists of two decklayers bonded together by vertical piles in a sandwich structure with piles (thick fibers) woven into the decklayers. The thesis includes, the analytical model developed for prediction of absorption coefficients, finite element solution using commercial software MSC.ACTRAN and experimental results obtained from impedance tube measurements. Different absorption characteristics can be achieved by variations in hole diameter and hole spacing. Based on the developed models, an optimization is performed to obtain an efficient absorber configuration. It has been anticipated that several different and interesting applications can be deduced by combining structural and sound absorption properties of this new micro-perforated absorber along with conventional fibrous absorbers.

Fuel cells are direct energy conversion devices to generate electricity. They have the lowest emission level of all forms of electricity generation. Fuel cells require no combustion of the fuel. The thermal energy gained from fuel cells may be utilized in micro turbines (gas turbines). In this work, first and second law analyses are performed on a hybrid system consisting of a solid oxide fuel cell (SOFC) combined with a micro turbine to be able to find an optimum point of pressure and corresponding mass ratio to gain maximum work output. Also another system with same equipments only without a gas turbine is investigated to see the effects of gas turbine. The analyses are performed utilizing a code written in MATLAB for each of the equipments. Fuel used is biomass with a certain concentration. To be able to use biomass in a fuel cell-micro turbine hybrid cycle, it is gasified and converted into a certain calorific value gas, with the use of gasifiers. In this study fluidized bed gasifier is utilized since it has the advantage of good mixing and high heat transfer leading to a uniform bed condition. Desulphuration and gas filter units will be implemented in order to clean the producer gas before being used in hybrid system. For a certain percentage of the fuel that may pass through the fuel cell without being used, a combustor is utilized. Optimum point mass and pressure ratios for system are MR = 0.6411 and Pr = 8. Gas turbine supplies more power and higher efficiency to the system. There are different choices for fuel selection in hybrid systems. The reason why biomass is examined among these is that it decreases the depletion of energy carriers and reduces the environmental impact.

Aluminum based alloys have wide area of usage in automotive and defense industry and bending processes are frequently applied during production. One of the most important design criteria of bending processes is springback, which can be basically defined as elastic recovery of the part during unloading. To overcome this problem, heat treatment is generally applied to the workpiece material to refine tensile properties. In this study, the effect of heat treatment on springback characteristics of aluminum studied both numerically by using finite element analysis and experimentally. For this purpose, two different materials are selected and various heat treatment procedures are considered. The aluminum sheets having thickness of 1.6 mm, 2 mm and 2.5 mm are bent to 60&amp / #730 / , 90&amp / #730 / and 120&amp / #730 / . The von Mises stress distributions, plastic strain values and punch load values and comparison of the numerical and experimental results are also given.

The atomization problem of high speed viscous jets has many applications in industrial processes and machines. In all these applications, it is required that the droplets have high surface area/volume ratio meaning that the droplets should be as small as possible. This can be achieved with high rates of turbulence and mixing of the flow. In order to constitute a foresight of geometry eects on droplet size, experimental investigation and the determination of flow characteristics in near and far fields of a low-speed air jet have been performed. In order to fulfill this task, three components of instantaneous velocity are measured, using a triple sensor Constant Temperature Anemometer (CTA) system. Through these measurements, mean velocity, Reynolds stress, velocity decay, spreading rate, turbulent kinetic energy, vorticity, and mass entrainment rate values are obtained. Stress-Strain relationship is also observed. Measurements are obtained for a baseline circular nozzle (round jet) as well as for an equilateral triangular and a square nozzle. On the basis of these measurements, the equilateral triangular jet is found to be the best option in order to get highest turbulence and mixing level with smallest core length.