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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

IKADE : an Intelligent Knowledge Assisted Design Environment incorporating manufacturing and production information

Saggu, J. S. January 1991 (has links)
No description available.
2

Sensitivity applications in structural design synthesis

Jawed, S. M. A. H. January 1985 (has links)
No description available.
3

Dispersed base combat aircraft

Hartland, A. J. January 1989 (has links)
No description available.
4

Evolutionary decomposition of complex design spaces

Bonham, Christopher Richard January 2000 (has links)
This dissertation investigates the support of conceptual engineering design through the decomposition of multi-dimensional search spaces into regions of high performance. Such decomposition helps the designer identify optimal design directions by the elimination of infeasible or undesirable regions within the search space. Moreover, high levels of interaction between the designer and the model increases overall domain knowledge and significantly reduces uncertainty relating to the design task at hand. The aim of the research is to develop the archetypal Cluster Oriented Genetic Algorithm (COGA) which achieves search space decomposition by using variable mutation (vmCOGA) to promote diverse search and an Adaptive Filter (AF) to extract solutions of high performance [Parmee 1996a, 1996b]. Since COGAs are primarily used to decompose design domains of unknown nature within a real-time environment, the elimination of apriori knowledge, speed and robustness are paramount. Furthermore COGA should promote the in-depth exploration of the entire search space, sampling all optima and the surrounding areas. Finally any proposed system should allow for trouble free integration within a Graphical User Interface environment. The replacement of the variable mutation strategy with a number of algorithms which increase search space sampling are investigated. Utility is then increased by incorporating a control mechanism that maintains optimal performance by adapting each algorithm throughout search by means of a feedback measure based upon population convergence. Robustness is greatly improved by modifying the Adaptive Filter through the introduction of a process that ensures more accurate modelling of the evolving population. The performance of each prospective algorithm is assessed upon a suite of two-dimensional test functions using a set of novel performance metrics. A six dimensional test function is also developed where the areas of high performance are explicitly known, thus allowing for evaluation under conditions of increased dimensionality. Further complexity is introduced by two real world models described by both continuous and discrete parameters. These relate to the design of conceptual airframes and cooling hole geometries within a gas turbine. Results are promising and indicate significant improvement over the vmCOGA in terms of all desired criteria. This further supports the utilisation of COGA as a decision support tool during the conceptual phase of design.
5

Design and integration of an unmanned aerial vehicle navigation system

Dittrich, Joerg S. 05 1900 (has links)
No description available.
6

Fatigue crack growth in an aluminium-lithium (8090) alloy

Dodd, A. January 1988 (has links)
No description available.
7

Analytical wing weight prediction/estimation using computer based design techniques

Murphy, N. A. D. January 1987 (has links)
No description available.
8

Development of interactive aircraft design software for use in problem based learning

Al-Shamma, Omran January 2013 (has links)
In the last ten years or so, many interactive aircraft design software packages have been released into the market. One drawback of these packages is that they assume prior knowledge in the field of aircraft design. Also, their main purpose being the preliminary aircraft design in a commercial environment, and are not intended for instructional use. Aircraft Design is an iterative process, and the students in the formative years of training must realise that one year of study is not enough to embrace all the necessary underlying concepts in this field. Most universities present the aircraft design as a classical Problem-Based Learning scenario, where students work in groups, with the group size varying between 5 and 8 students., each with a designated role, to carry out a specific task. The students work through the classical process of preliminary design based largely on textbook methods. Therefore, the need for a preliminary design tool (software) that helps the students to understand, analyse, and evaluate their aircraft design process exists. The developed software does everything that is needed in the preliminary design environment. Students are interactively guided through the design process, in a manner that facilitates lifelong learning. Comprehensive output is provided to highlight the “what if scenarios”. The software consists of many modules such as input (user interface), weight estimation, flight performance, cost estimation, take-off analysis, parametric studies, optimisation, and dynamic stability. Due to the large number of input design variables, a full interactive Graphical-User-Interface (GUI) is developed to enable students to evaluate their designs quickly. Object-Oriented-Programming (OOP) is used to create the GUI environment. The stability and control derivatives computed in this work are largely based on analytical techniques. However, a facility is provided in the software to create the data input file required to run a software package produced by USAF, called DATCOM, that enables computation of the dynamic stability and control derivatives that can be ultimately used in flight simulation work. Amongst all the variables used in aircraft design, aircraft weight is the most significant. A new weight estimation module has been developed to increase the accuracy of estimation to better than 5%. Its output results agree very favourably with the published data of current commercial aircraft such as Airbus and Boeing. Also, a new formula is proposed to estimate the engine weight based on its thrust in the absence of the data available with high degree of accuracy. In order to evaluate the effectiveness of the design under consideration, a comprehensive methodology has been developed that can predict the aircraft price as a function of aircraft weight. The Direct Operating Cost (DOC) is also calculated using methods proposed by ATA, NASA, and AEA. Finally, a walk-through of two case studies are presented, one for large transport aircraft and other for small business jet, to show how typical undergraduate students will proceed with the design and to demonstrate the effectiveness of the developed software.
9

A Scalable, Parallel Approach for Multi-point, High-fidelity Aerostructural Optimization of Aircraft Configurations

Kenway, Gaetan Kristian Wiscombe 08 August 2013 (has links)
This thesis presents new tools and techniques developed to address the challenging problem of high-fidelity aerostructural optimization with respect to large numbers of design variables. A new mesh-movement scheme is developed that is both computationally efficient and sufficiently robust to accommodate large geometric design changes and aerostructural deformations. A fully coupled Newton-Krylov method is presented that accelerates the convergence of aerostructural systems and provides a 20% performance improvement over the traditional nonlinear block Gauss-Seidel approach and can handle more flexible structures. A coupled adjoint method is used that efficiently computes derivatives for a gradient-based optimization algorithm. The implementation uses only machine accurate derivative techniques and is verified to yield fully consistent derivatives by comparing against the complex step method. The fully-coupled large-scale coupled adjoint solution method is shown to have 30% better performance than the segregated approach. The parallel scalability of the coupled adjoint technique is demonstrated on an Euler Computational Fluid Dynamics (CFD) model with more than 80 million state variables coupled to a detailed structural finite-element model of the wing with more than 1 million degrees of freedom. Multi-point high-fidelity aerostructural optimizations of a long-range wide-body, transonic transport aircraft configuration are performed using the developed techniques. The aerostructural analysis employs Euler CFD with a 2 million cell mesh and a structural finite element model with 300000 DOF. Two design optimization problems are solved: one where takeoff gross weight is minimized, and another where fuel burn is minimized. Each optimization uses a multi-point formulation with 5 cruise conditions and 2 maneuver conditions. The optimization problems have 476 design variables are optimal results are obtained within 36 hours of wall time using 435 processors. The TOGW minimization results in a 4.2% reduction in TOGW with a 6.6% fuel burn reduction, while the fuel burn optimization resulted in a 11.2% fuel burn reduction with no change to the takeoff gross weight.
10

A Scalable, Parallel Approach for Multi-point, High-fidelity Aerostructural Optimization of Aircraft Configurations

Kenway, Gaetan Kristian Wiscombe 08 August 2013 (has links)
This thesis presents new tools and techniques developed to address the challenging problem of high-fidelity aerostructural optimization with respect to large numbers of design variables. A new mesh-movement scheme is developed that is both computationally efficient and sufficiently robust to accommodate large geometric design changes and aerostructural deformations. A fully coupled Newton-Krylov method is presented that accelerates the convergence of aerostructural systems and provides a 20% performance improvement over the traditional nonlinear block Gauss-Seidel approach and can handle more flexible structures. A coupled adjoint method is used that efficiently computes derivatives for a gradient-based optimization algorithm. The implementation uses only machine accurate derivative techniques and is verified to yield fully consistent derivatives by comparing against the complex step method. The fully-coupled large-scale coupled adjoint solution method is shown to have 30% better performance than the segregated approach. The parallel scalability of the coupled adjoint technique is demonstrated on an Euler Computational Fluid Dynamics (CFD) model with more than 80 million state variables coupled to a detailed structural finite-element model of the wing with more than 1 million degrees of freedom. Multi-point high-fidelity aerostructural optimizations of a long-range wide-body, transonic transport aircraft configuration are performed using the developed techniques. The aerostructural analysis employs Euler CFD with a 2 million cell mesh and a structural finite element model with 300000 DOF. Two design optimization problems are solved: one where takeoff gross weight is minimized, and another where fuel burn is minimized. Each optimization uses a multi-point formulation with 5 cruise conditions and 2 maneuver conditions. The optimization problems have 476 design variables are optimal results are obtained within 36 hours of wall time using 435 processors. The TOGW minimization results in a 4.2% reduction in TOGW with a 6.6% fuel burn reduction, while the fuel burn optimization resulted in a 11.2% fuel burn reduction with no change to the takeoff gross weight.

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