Thesis. 1976. M.S.--Massachusetts Institute of Technology. Dept. of Civil Engineering. / Microfiche copy available in Archives and Engineering. / Includes bibliographical references. / M.S.

This paper studies the geometrically non-linear bending behavior of functionally graded beams subjected to buckling loads using the finite element method. The computational model is based on an improved first-order shear deformation theory for beams with five independent variables. The abstract finite element formulation is derived by means of the principle of virtual work. High-order nodal-spectral interpolation functions were utilized to approximate the field variables which minimizes the locking problem. The incremental/iterative solution technique of Newton's type is implemented to solve the nonlinear equations. The model is verified with benchmark problems available in the literature. The objective is to investigate the effect of volume fraction variation in the response of functionally graded beams made of ceramics and metals. As expected, the results show that transverse deflections vary significantly depending on the ceramic and metal combination. / Revisión por pares

This thesis presents a research project and results of design and optimization of a composite wing structure for a large aircraft in flying wing configuration. The design process started from conceptual design and preliminary design, which includes initial sizing and stressing followed by numerical modelling and analysis of the wing structure. The research was then focused on the minimum weight optimization of the /composite wing structure /subject to multiple design /constraints. The modelling, analysis and optimization process has been performed by using the NASTRAN code. The methodology and technique not only make the modelling in high accuracy, but also keep the whole process within one commercial package for practical application. The example aircraft, called FW-11, is a 250-seat commercial airliner of flying wing configuration designed through our MSc students Group Design Project (GDP) in Cranfield University. Started from conceptual design in the GDP, a high-aspect-ratio and large sweepback angle flying wing configuration has been adopted. During the GDP, the author was responsible for the structural layout design and material selection. Composite material has been chosen as the preferable material for both the inner and outer wing components. Based on the derivation of structural design data in the conceptual phase, the author continued with the preliminary design of the outer wing airframe and then focused on the optimization of the composite wing structure. Cont/d.

Islamic design is a rich art form with spiritual and meditative meaning expressed through its infinite pattern. The iterative process of creating pattern, unified yet diverse, is an intri-cate geometric path conveying conceptual exploration. Process of form development in Is-lamic patterns defines its growing design, seeking explicit relationships between unity and multiplicity. As the grid expands and patterns unfold, new concepts are introduced for pat-tern exploration and formation. Reoccurring focal points of the Islamic geometries mark significant moments in which these patterns take form. By fusing traditional Islamic design fundamentals with contemporary concepts for interiors, I expand the realm of this rich art form from a two dimensional form to a three dimensional structure.

ABSTRACT DESIGN OF A DEMOLITION BOOM &Ccedil / etin, Bet&uuml / l M.S, Department of Mechanical Engineering Supervisor : Prof. Dr. Eres S&Ouml / YLEMEZ August 2007, 96 pages Excavators are used for many purposes. Some of these are digging, drilling, breaking and demolition. A demolition excavator boom consists of 3-piece boom which is different in form and construction from a 2-piece boom used in standard excavator. The aim of this thesis is to design a demolition boom for hydraulic excavator with operation weight of 30 ton. With this construction a higher reach is gained. Design of the demolition boom consists of three stages. Firstly the mechanism design is performed to determine the basic link dimensions. In the second step the structural shape of the boom is estimated to perform static stress analysis. The EXCEL program is chosen due to the ease of repetative calculations and applying the changes in structure parameters. The demolition boom is modeled by PRO-ENGINEER, and consequently the model is analyzed by using a Finite Element Analysis (FEA) in MSC.Marc-Mentat. According to the FEA results the model is revised. Keywords: Demolition Excavator, Mechanism Design, Structural design

In this study, equipment rack structure for a medium transport aircraft was designed and finite element analysis of this design was performed. The equipment rack structure, which was designed for a modernization project, was positioned and dimensions were determined by regarding the geometry of primary structures of the aircraft. The structure was designed such that it satisfies the pre-defined margin of safety values. Design of the structure was prepared in Unigraphics, and the finite element modeling and analysis phases were carried out using MSC.Patran and MSC.Nastran programs. For the fastener analysis, which is usually carried out by hand calculations, two analysis tools were prepared by using FORTRAN and Microsoft Office Excel programs. These tools were found to greatly facilitate the analysis and save time. As these tools can be used in other finite element analyses, in which MSC.Patran and MSC.Nastran programs are used, user manuals were prepared.

This thesis aims to present the design and analysis of a structural component of a heavy transport aircraft. The designed component is the &ldquo / coupling&ldquo / which is the interface member connecting two frames or two stringers in the fuselage assembly. The &ldquo / frames&rdquo / , which are the circumferential stiffeners, are joined together by the &ldquo / frame couplings&rdquo / . The &ldquo / stringers&rdquo / , which are the longitudinal stiffeners, are joined together by the &ldquo / stringer couplings&rdquo / . At the preliminary design phase / the structural design principles of the frame and the stringer coupling parts are explained / which are based on the company experiences that were gained from previous aircraft projects. Afterwards, conceptual design phase is performed by structural analysis of the components. The structural analysis methods are defined and illustrated by analyzing typical examples of the frame and the stringer coupling parts. Moreover, the critical load case selection process for the structural components is explained and brief information about the load cases that the structural components will be subjected to in their service life are also given in order to have a feeling about flight regime of the aircraft. The applied loads used in structural analysis of the frame coupling and the stringer coupling components are obtained from the global finite element model of the aircraft. The verification process of the part of global finite element model where the developed components are located is also explained in the thesis. Finally, the general conclusions of the thesis are specified and the recommendations for future work are proposed for similar design and analysis efforts.

This thesis investigates the effects of camber change on the mission adaptive wing of a structurally designed unmanned aerial vehicle (UAV). The commercial computational fluid dynamics (CFD) software ANSYS/FLUENT is employed for the aerodynamic analyses. Several cambered airfoils are compared in terms of their aerodynamic coefficients and the effects of the camber change formed in specific sections of the wing on the spanwise pressure distribution are investigated. The mission adaptive wing is modeled structurally to observe the effect of spanwise pressure distribution on the wing structure. For the structural design and analysis of the UAV under this study, commercial software MSC/PATRAN and MSC/NASTRAN are used. The structural static and dynamic analyses of the unmanned aerial vehicle are also performed under specified flight conditions. The results of these analyses show that the designed structure is safe within the flight envelope. Having completed aero-structural design and analysis, the designed unmanned aerial vehicle is manufactured by TUSAS Aerospace Industries (TAI).

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This thesis aims at Multi-Objective Optimization under Uncertainty in structural design. We investigate Polynomial Chaos Expansion (PCE) surrogates which require extensive training sets. We then face two issues: high computational costs of an individual Finite Element simulation and its limited precision. From numerical point of view and in order to limit the computational expense of the PCE construction we particularly focus on sparse PCE schemes. We also develop a custom Latin Hypercube Sampling scheme taking into account the finite precision of the simulation. From the modeling point of view,we propose a multifidelity approach involving a hierarchy of models ranging from full scale simulations through reduced order physics up to response surfaces. Finally, we investigate multiobjective optimization of structures under uncertainty. We extend the PCE model of design objectives by taking into account the design variables. We illustrate our work with examples in sheet metal forming and optimal design of truss structures.