This thesis presents a nontraditional treatment for uncertainties in the material, geometry, and load parameters in linear static finite element analysis (FEA) for mechanics problems. Uncertainties are introduced as bounded possible values (intervals). FEA with interval parameters (interval FEA, IFEA) calculates the bounds on the system response based on the ranges of the system parameters. The obtained results should be accurate and efficiently computed. Toward this end, a rigorous interval FEA is developed and implemented. In this study, interval arithmetic is used in the formulation to guarantee an enclosure for the response range. The main difficulty associated with interval computation is the dependence problem, which results in severe overestimation of the system response ranges. Particular attention in the development of the present method is given to control the dependence problem for sharp results. The developed method is based on an Element-By-Element (EBE) technique. By using the EBE technique, the interval parameters can be handled more efficiently to control the dependence problem. The penalty method and Lagrange multiplier method are used to impose the necessary constraints for compatibility and equilibrium. The resulting structure equations are a system of parametric linear interval equations. The standard fixed point iteration is modified, enhanced, and used to solve the interval equations accurately and efficiently. The newly developed dependence control algorithm ensures the convergence of the fixed point iteration even for problems with relatively large uncertainties. Further, special algorithms have been developed to calculate sharp results for stress and element nodal force. The present method is generally applicable to linear static interval FEA, regardless of element type. Numerical examples are presented to demonstrate the capabilities of the developed method. It is illustrated that the present method yields rigorous and accurate results which are guaranteed to enclose the true response ranges in all the problems considered, including those with a large number of interval variables (e.g., more than 250). The scalability of the present method is also illustrated. In addition to its accuracy, rigorousness and scalability, the efficiency of the present method is also significantly superior to conventional methods such as the combinatorial, the sensitivity analysis, and the Monte Carlo sampling method.

In this study, the structural optimization of a cruise missile wing is accomplished for the aerodynamic loads for four different flight conditions. The flight conditions correspond to the corner points of the V-n diagram. The structural analysis and optimization is performed using the ANSYS finite element program. In order to construct the flight envelope and to find the pressure distribution in each flight condition, FASTRAN Computational Fluid Dynamics program is used. The structural optimization is performed for two different wing configurations. In the first wing configuration all the structural members are made up of aluminum material. In the second wing configuration, the skin panels are all composite material and the other members are made up of aluminum material. The minimum weight design which satisfies the strength and buckling constraints are found for both wings after the optimization analyses.

Computer aided auto-construction of various types of folded horns and acoustic analysis of coupled horn and driver systems are presented in this thesis. A new procedure is developed for auto construction of folded horn shapes. Linear graph modeling technique is employed for specification of horn driver output in terms of diaphragm velocity or throat pressure. In the final phase of the design procedure, acoustic analysis of folded horns is carried by means of finite element analysis. A commercial software package MSC.ACTRAN is used to calculate directivity patterns and resulting acoustic pressure in the free field. Horn geometry consisting of linear, exponential, hyperbolic and tractrix shapes is automatically constructed by parallel working of Delphi and finite element analysis program. The enclosure bordering the horn contours are considered rigid in the analyses. Maximum number of folding is limited to two. This study is made possible to evaluate the performance of these four types of horn contours for a specified range of frequencies.

Conventional methods used in the structural analysis are usually insufficient for the analysis of historical structures because of the complex geometry and heterogeneous material properties of the structure. Today&rsquo / s computing facilities and methods make FEM the most suitable analysis method for complex structural geometry and heterogeneous material properties. Even the shrinkage, creep of the material can be considered in the analysis. Because of this reason Finite Element Method (FEM) is used to analyze such structures. FEM converts the structure into finite number of elements with specific degree of freedoms and analyses the structure by using matrix algebra. However, advanced FEM methods considering the inelastic and time dependent behavior of material is a very complex and difficult task and consumes considerable time. Because of this reason, to analyze every historical structure is not feasible by applying advanced inelastic FEM, whereas elastic FEM analysis at low load levels is very helpful in understanding the behavior of the structure.The analysis of a masonry gate in the historical city, Hasankeyf is the case study of this thesis. Different common software are used in FEM to compare the stresses, deformations, modal shapes etc. of the same structure. Besides the inelastic behavior of the structure is investigated and compared with the elastic behavior of the structure. The study is intended to show that at the low load levels elastic FEM analysis is sufficient to understand the response of the structure and is preferable to the inelastic FEM analysis unless a very complex analysis is required

In this study, settlement and seepage behavior of Muratli Dam, which is the first asphalt faced rockfill dam in Turkey, is investigated for the &ldquo / end of construction&rdquo / and &ldquo / reservoir impoundment&rdquo / loading conditions. Two dimensional plane strain finite element analyses are carried out in order to determine the total stresses, displacements and pore water pressures. Hardening soil model is used in order to represent the non-linear, inelastic and stress dependent behavior of rockfill material. Material model parameters are selected mainly referring to the previous studies on the dams consisting of similar materials and then back analyses are done to find the best fit. Calculated stresses, displacements and pore water pressures are compared with the observed values for both end of construction and reservoir filling conditions.

Forging temperature is one of the basic considerations in forging processes. In warm forging, the metals are forged at temperatures about the recrystallization temperature and below the traditional hot forging temperature. Warm forging has many advantages when compared to hot and cold forging. Accuracy and surface finish of the parts is improved compared to hot forging while ductility is increased and forming loads are reduced when compared to cold forging. In this study, forging process of a part which is currently produced at the hot forging temperature range and which needs some improvements in accuracy, material usage and energy concepts, is analyzed. The forging process sequence design with a new preform design for the particular part is proposed in warm forging temperature range and the proposed process is simulated using Finite Element Method. In the simulations, coupled thermal mechanical analyses are performed and the dies are modeled as deformable bodies to execute die stress analysis. Experimental study is also carried out in METU-BILTIR Center Forging Research and Application Laboratory and it has been observed that numerical and experimental results are in good agreement. In the study, material wastage is reduced by proposing using of a square cross section billet instead of a circular one, energy saving and better accuracy in part dimensions is achieved by reducing the forging temperature from the hot forging to the warm forging temperature range.

Combination of high strength with light weight which is the prominent property of aluminum alloy forgings has led aluminum forgings used in rapidly expanding range of applications. In this study, to produce a particular 7075 aluminum alloy part, the forging process has been designed and analyzed. The forging process sequence has been designed by using Finite Volume Method. Then, the designed process has been analyzed by using Finite Element Method and the stress, strain and temperature distributions within the dies have been determined. Five different initial temperatures of the billet / 438, 400, 350, 300 and 250 degree Celsius have been considered in the thermo-mechanically coupled simulations. The initial temperatures of the dies have been taken as 200 degree Celsius for all these analyses. Finite volume analysis and finite element analysis results of the preform and finish part have been compared for the initial billet temperature of 400 oC. Close results have been observed by these analyses. The experimental study has been carried out for the range of the initial billet temperatures of 251&amp / #8211 / 442 degree Celsius in METU-BILTIR Center Forging Research and Application Laboratory. It has been observed that the numerical and the experimental results are in good agreement and a successful forging process design has been achieved. For the initial die temperature of 200 degree Celsius, to avoid the plastic deformation of the dies and the incipient melting of the workpiece, 350 degree Celsius is determined to be the appropriate initial billet temperature for the forging of the particular part.

Forging operation is one of the most commonly used manufacturing techniques in defense industry. The products of forging operation have higher material strength when comparing to traditional manufacturing operations. Especially, for the mass production, it is a beneficial method considering metal and cost saving. The commonly used part named Fin Connector Rod in defense industry requires high material strength due to working conditions. In this thesis, manufacturing of this part by hot forging operation is accomplished after analyzing by using the finite element method. Two alternative forging processes are compared and the applicable alternative method is selected by using a finite element program. Dies are designed for applied processes. The stress distribution and the current temperature variation within the parts analyzed to evaluate the results. The fin connector rod is manufactured according to the results of the finite element analysis. It has been observed that, manufacturing of the fin connector rod by hot forging is succeeded and the waste material and cost is reduced when compared to the machining operation which is being used currently.

In this study, the structural design and analysis of a wing having mission-adaptive control surfaces were conducted. The wing structure was designed in order to withstand a maximum aerodynamic loading of 5 g due to maneuver. The structural model of the wing was developed by using MSC/PATRAN package program and that structural model was analyzed by using MSC/NASTRAN package program. The designed wing was then manufactured by Turkish Aerospace Industries Inc. (TUSAS-TAI). The finite element analysis results were verified by conducting ground vibration tests on the manufactured wing. The comparative results were used to tune the finite element model and the results obtained showed that the modeling was very successful.

Due to their practical application, flat-plates have been commonly used slab type in constructions in recent years. According to the investigations that were performed since the beginning of the 20th century, the vicinity of the slab-column connection is found to be susceptible to punching failure that causes serious unrepairable damage leading to the collapse of the structures. The objective of this study is to enhance the punching shear strength of slab-column connections in existing deficient flat plate structures. For this purpose, an economical and easy to install strengthening method was applied to &frac34 / scale flat-slab test specimens. The proposed strengthening scheme employs the use of in house-fabricated Carbon Fiber Reinforced Polymer (CFRP) dowels placed around the column stubs in different numbers and arrangements as vertical shear reinforcement. In addition, the effect of column aspect ratio on strengthening method was also investigated in the scope of this study. Strength increase of at least 30% was obtained for the CFRP retrofitted specimens compared to the companion reference specimen. Three-dimensional finite element analyses of test specimens were conducted by using the general purpose finite element analyses program. 3-D finite element models are successful in providing reasonable estimates of load-deformation behavior and strains. The experimental punching shear capacities and observed failure modes of the specimens were compared with the estimations of strength and failure modes given by punching shear strength provisions of ACI 318-08, Eurocode-2, BS8110-97 and TS500. Necessary modifications were proposed for the existing provisions of punching shear capacity in order to design CFRP upgrading.