The methods of analysis used to determine ultimate bearing capacity of piles are applied to a field case in Turkey. During the pile driving works of the Atat&uuml / rk Culture Center in Samsun, Delmag D22-13 and Delmag D-15 diesel pile driving hammers have been used. The ultimate bearing capacity and skin friction values calculated using static formulas have been given as input to the wave equation pile analysis program FADWAVE written by J.E.Bowles. The analytical method used in this program was based on the wave propagation in solids originated in 1962 by E.A.L.Smith. The results obtained from the program are compared with each other.

Modal parameter identification of a structure is done through modal testing and modal analysis using various system identification methods. These methods employ linear input-output relationships to extract the modes of a structure. There are cases where laboratory testing of a structure is not possible or information about the structure under operating conditions is seeked. A set of techniques called Operational Modal Analysis have been developed for modal parameter identification in operating conditions of a structure. These techniques use only response measurements to extract the modes. The aim of this study is to investigate the applicability and use of three selected time-domain methods adapted to operational modal analysis. The algorithms are programmed in Matlab&copy / environment, and various cases are evaluated using computer simulations for each method. Two of the selected methods are evaluated on a laboratory scale test setup.

Mathematical models that are built in order to simulate the behavior of structures, most often, tend to respond differently than the actual structures in their initial state. In order to use the mathematical models and their computational outputs instead of testing the real structure under every possible case, it is mandatory to have a mathematical model that reflects the characteristics of the actual structure in the best possible way. In this thesis, the so called model updating techniques used for updating the mathematical models in order to make them respond in the way the actual structures do are investigated. Case studies using computationally generated test data are performed using the direct and indirect modal updating techniques with the software developed for each method investigated. After investigating the direct and indirect modal updating techniques, two of them, one using frequency response functions and the other using modal sensitivities, are determined to be the most suitable ones for aircraft structures. A generic software is developed for the technique using modal sensitivities. A modal test is carried out on a scaled aircraft model. The test data is used for updating of the finite element model of the scaled aircraft using the modal sensitivities and the usability of the method is thus evaluated. The finite element model of a real aircraft using the modal test data is also updated using the modal sensitivities. A new error localization technique and a model updating routine are also proposed in this thesis. This modal updating routine is used with several case studies using computationally generated test data and it is concluded that it is capable of updating the mathematical models even with incomplete measured data.

Oil feed grooves are implemented in reciprocating compressor piston applications to assure a constant supply of lubricating oil on bearing surfaces and decrease friction loss. In a hermetically sealed compressor, due to small clearances encountered, oil supply becomes critical in order not to operate in boundary lubrication regime. Due to the small size of the piston and small piston &ndash / cylinder clearance, a partial lubrication regime is present. In the current study, a model that solves Reynolds&rsquo / equation for piston-cylinder lubrication and the average Reynolds&rsquo / equation that considers the effect of roughness on partially lubricated bearing for a compressor piston with oil feed grooves is developed. A parametric study is carried out to investigate the effects of piston design parameters and then arrive at an improved piston performance by using alternative designs for oil feed groove and the other design parameters.

Flutter analyses and tests are the major items in flight certification efforts required when a new air vehicle is developed or when a new external store is developed for an existing aircraft. The flight envelope of a new aircraft as well as the influence of aircraft modifications on an existing flight envelope can be safely determined only by flutter tests. In such tests, the aircraft is instrumented by accelerometers and exciters. Vibrations of the aircraft at specific dynamic pressures are measured and transmitted to a ground station via telemetry systems during flutter tests. These vibration data are analyzed online by using a flutter test software with various methods implemented in order to predict the safety margin with respect to flutter. Tests are performed at incrementally increasing dynamic pressures and safety regions of the flight envelope are determined step by step. Since flutter is a very destructive instability, tests are performed without getting too close to the flutter speed and estimations are performed by extrapolation. In this study, pretest analyses and flutter prediction methods that can be used in various flight conditions are investigated. Existing methods are improved and their applications are demonstrated with experiments. A novel method to predict limit cycle oscillations that are encountered in some modern fighter aircraft is developed. The prediction method developed in this study can effectively be used in cases where the nonlinearities in aircraft dynamics and air flow reduce the applicability of the classical prediction methods. Some further methods to reduce the adverse effects of these nonlinearities on the predictions are also developed.

This thesis comprises a study on the kinematic and force analyses of the overconstrained mechanisms. The scope of the overconstrained mechanisms is too wide and difficult to handle. Therefore, the study is restricted to the planar overconstrained mechanisms. Although the study involves only the planar overconstrained mechanisms, the investigated methods and approaches could be extended to the spatial overconstrained mechanisms as well. In this thesis, kinematic analysis is performed in order to investigate how an overconstrained mechanism can be constructed. Four methods are used. These are the analytical method, the method of cognates, the method of combining identical modules and the method of extending an overconstrained mechanism with extra links. This thesis also involves the force analysis of the overconstrained mechanisms. A method is introduced in order to eliminate the force indeterminacy encountered in the overconstrained mechanisms. The results are design based and directly associated with the assembly phase of the mechanism.

This study focuses on the external configuration design of a tactical missile based on maximizing flight range while minimizing the radar signature which is a crucial performance parameter for survivability. It is known that shaping of a missile according to aerodynamic performance may have significant negative effects on the radar cross section. Thus, the impact of the geometry changes on the aerodynamic performance and the radar cross section is investigated. Suggorage models for the flight range, control effectiveness and the radar cross section (RCS) at an X band frequency are established by employing Genetic Algorithm. Accuracies of surrogate models are discussed in terms of statistical parameters. Seventeen geometrical parameters are considered as the design variables. Optimum combinations for the design variables are sought such that flight range is maximized while the radar cross section is minimized. The multi objective optimization problem is solved by imposing the static stability margin as a hard nonlinear constraint. Weighted sum approach is utilized to compare results with known missile configurations. Weights for flight range and Radar Cross Section are varied to obtain Pareto optimal solutions.

In this research, we developed an ontology based reuse infrastructure for trajectory simulation and investigated the use of ontologies and domain engineering practices to develop a formalized methodology to make use of the experience and knowledge leveraged from the past trajectory simulation projects. Trajectory simulation in this context is a computational tool to calculate the flight path and other parameters of munition such as its orientation or angular rates during its operation In this thesis, engineering knowledge to simulate the trajectory of a munition is captured in an ontology called Trajectory Simulation ONTology (TSONT). Concepts of trajectory simulation and the relation among these concepts are captured by using Web Ontology Language and presented as a domain model that is available for reuse. Using the formalized domain knowledge, reuse infrastructure specifications are constructed to enable the reuse of software artifacts for two main programming paradigms, which are object oriented programming and function oriented programming. UML and application frameworks are used when constructing for object oriented paradigm. And data flow diagrams are used to formalize the design of the function oriented simulations to compute the trajectory of munition. Object oriented and function oriented platform independent designs are constructed to specify the infrastructure using the knowledge captured in TSONT and made available for reuse. With constructing two different designs for two different paradigms by using the same domain model, evidence of knowledge reuse were produced. Three different case studies were carried out as infrastructure implementation. In the first case study, an object oriented application framework was developed in MATLAB for six degrees of freedom trajectory simulation using platform independent object oriented design. This framework is reused to develop two different simulations. Using the developed framework for two applications produced evidence of code reuse. In the second case, a point mass trajectory simulation framework is designed to be implemented in C# reusing the same platform independent object oriented design. This case produced the evidence of design reuse. In the last case study, a MATLAB Simulink Blockset is developed for point mass unguided trajectory simulations and two different simulations are built using the Blockset. By this case, we collected the evidence of code reuse also in function oriented paradigm.

In this thesis, a two node nonlinear elastic-plastic beam finite element is developed to analyze large deformations. The system of equations are derived from virtual work principle, and the updated Lagrangian formulation is used. Material is assumed to be isotropic and rate insensitive obeying J2-flow rule. Work hardening characteristics of material is considered and all nonlinear terms are included. For the two node iso-parametric beam element a layered model is used to analyze through-the-thickness distribution of elastic and plastic zones. A finite element program is developed and the numerical outcomes are compared with the experimental results. A good agreement is achieved between numerical and experimental results.

&ldquo / Numerically Controlled&rdquo / (NC) machine tools, which are automatically operated by encoded (digital) commands, are capable of machining components with quality and quantity. Manufacturing industry heavily depends on these machines. Many different control architectures have been adapted in today&rsquo / s CNC technology. Centralized control system is quite popular in industry due to its ease of implementation. If the number of controlled axes on a CNC machine tool (&gt / 3), increases so does the computational burden on the central processors. Hence, more powerful processors are needed. An alternative architecture, which is not commonly used in CNC technology, is the decentralized (distributed) control. In this topology, the tasks handled by the distributed controllers that are interconnected to each other by a communication network. As the need arises, a new controller can be added easily to the network without augmenting the physical configuration. Despite its attractive features, this architecture has not been fully embraced by the CNC industry. Synchronization among the axes in the coordinated motion is proven to be quite challenging. In this thesis, alternative distributed controller architecture was proposed for CNC machine tools. It was implemented on a 3-axis CNC milling machine. Open-loop control performance was investigated under various conditions. Different communication protocols along with different physical communication interfaces and a number of controller hardware were devised. An industry-standard network (RS-485) was set up by interconnecting these distributed controllers. Different data transmission protocols were devised in order to establish appropriate communication methods. Also, computer software (a.k.a. graphical user interface), which can coordinate the interconnected controllers, interpret NC part programs and generate reference position data for each axis, was designed within the scope of this thesis.