<p>U disertaciji se prikazuje razvoj sistema za<br />projektovanje i optimizaciju konstrukcije pribora za<br />ma&scaron;insku obradu. Analizirani su različiti prilazi u<br />projektovanu pribora. Prikazana je koncepcija i<br />funkcionisanje razvijenog sistema. Validacija sistema<br />je izvr&scaron;ena na konkternim radnim predmetima za<br />operacije obrade bu&scaron;enja i glodanja. Na kraju su dati<br />odgovarajući zaključci i mogući pravci budućih<br />istraživanja</p> / <p> The dissertation shows the development of<br /> system for fixture design and layout<br /> optimization for machining processi. Different<br /> approaches were analyzed in fixture design.<br /> The concept and functioning of the developed<br /> system is presented. Validation of the system<br /> is made with specific workpieces for drilling<br /> and milling process operations. At the end the<br /> appropriate conclusions and possible<br /> directions for future research are given.</p>

<p>U doktorskoj disertaciji je prikazana nova metodologija za projektovanje<br />i optimizaciju konstrukcije elemenata pribora. Projektovani su i<br />realizovani uređaji koji omogućavaju ispitivanje nosivosti i<br />popustljivosti kontakta između elemenata pribora i radnog predmeta u<br />statičkim i dinamičkim uslovima opterećenja. U istraživanjima je<br />simuliran proces stezanja elementima sa specijalno projektovanim<br />završetkom i praćena je nosivost i popustljivost spoja između<br />elemenata pribora i radnog predmeta. Utvrđeno je da standardni<br />elementi za stezanje sa ravnim čelom u odnosu na specijano<br />projektovane elemente imaju značajno manju nosivost i popustljivost.<br />Pozitivni efekti primene elemenata za stezanje sa specijalno<br />projektovanim završetkom ogledaju se u povećanju pouzdanosti, tačnosti<br />i produktivnosti mašinske obrade.</p> / <p>Presented in this doctoral dissertation is a new methodology for the design and<br />optimization of fixture elements. Special device is designed and manufactured<br />to test load capacity and interface compliance between fixture elements and<br />workpiece under static and dynamic loads during machining. The research<br />process is simulated by specially designed clamping elements and monitored<br />for load capacity and interface compliance between fixture elements and<br />workpiece. It was found that the standard clamping elements with flat clamping<br />surface have a significantly lower load capacity and interface compliance in<br />comparison with the specially designed clamping elements. Application of the<br />specially designed clamping elements results in increased reliability, accuracy<br />and machining productivity.</p>

No description available.

The objective of this research is to develop new stochastic methods based on most probable points (MPPs) for general reliability analysis and reliability-based design optimization of complex engineering systems. The current efforts involves: (1) univariate method with simulation for reliability analysis; (2) univariate method with numerical integration for reliability analysis; (3) multi-point univariate for reliability analysis involving multiple MPPs; and (4) univariate method for design sensitivity analysis and reliability-based design optimization. Two MPP-based univariate decomposition methods were developed for component reliability analysis with highly nonlinear performance functions. Both methods involve novel function decomposition at MPP that facilitates higher-order univariate approximations of a performance function in the rotated Gaussian space. The first method entails Lagrange interpolation of univariate component functions that leads to an explicit performance function and subsequent Monte Carlo simulation. Based on linear or quadratic approximations of the univariate component function in the direction of the MPP, the second method formulates the performance function in a form amenable to an efficient reliability analysis by multiple one-dimensional integrations. Although both methods have comparable computational efficiency, the second method can be extended to derive analytical sensitivity of failure probability for design optimization. For reliability problems entailing multiple MPPs, a multi-point univariate decomposition method was also developed. In addition to the effort of identifying the MPP, the univariate methods require a small number of exact or numerical function evaluations at selected input. Numerical results indicate that the MPP-based univariate methods provide accurate and/or computationally efficient estimates of failure probability than existing methods. Finally, a new univariate decomposition method was developed for design sensitivity analysis and reliability-based design optimization subject to uncertain performance functions in constraints. The method involves a novel univariate approximation of a general multivariate function in the rotated Gaussian space; analytical sensitivity of failure probability with respect to design variables; and standard gradient-based optimization algorithms. In both reliability and sensitivity analyses, the proposed effort has been reduced to performing multiple one-dimensional integrations. Numerical results indicate that the proposed method provides accurate and computationally efficient estimates of the sensitivity of failure probability and leads to accurate design optimization of uncertain mechanical systems.

A flight test program that evaluated the results of a CP140 Aurora cockpit modernization project was conducted between May 2004 and October 2005. This paper uses the results of that test program to show how basic human factors principles were violated which led to the identification of multiple design deficiencies. This paper proposes that the failure to apply good human factors principles when designing aircraft displays can lead to unacceptable deficiencies. The result can be poor modal awareness, confusion in the cockpit, and often negative training for the pilots. In particular, four major deficiencies were analyzed to determine the specific human factors principles that were breached. The violations included a lack of concise and relevant feedback to the pilot, unclear and ambiguous annunciations, poor use of colour coding principles and logic, a lack of suitable attention capture cueing, inappropriate alert cueing, an absence of aural cueing during specific degraded modes of operation, excessive cognitive workload, and a failure to incorporate the pilot as the focal point of the display design, also known as a human centred design philosophy. Recommendations for system design enhancements are provided to ensure safe and effective operations of this prototype system prior to operational implementation. The evaluation of the prototype system design was conducted by a flight test team from the Aerospace Engineering Test Establishment in Cold Lake, Alberta and supported by the Maritime Proving and Evaluation Unit in Greenwood, Nova Scotia. The test program encompassed a thorough review of system design documentation, abinitio training and preliminary testing in a Systems Integration Lab and 40 flight test missions. The recorded deficiencies were based upon the observations of two Qualified Test Pilots.

In the current Navy environment of undersea weapons development, the engineering aspect of design is decoupled from the development of the tactics with which the weapon is employed. Tactics are developed by intelligence experts, warfighters, and wargamers, while torpedo design is handled by engineers and contractors. This dissertation examines methods by which the conceptual design process of undersea weapon systems, including both torpedo systems and mine counter-measure systems, can be improved. It is shown that by simultaneously designing the torpedo and the tactics with which undersea weapons are used, a more effective overall weapon system can be created. In addition to integrating torpedo tactics with design, the thesis also looks at design methods to account for uncertainty. The uncertainty is attributable to multiple sources, including: lack of detailed analysis tools early in the design process, incomplete knowledge of the operational environments, and uncertainty in the performance of potential technologies. A robust design process is introduced to account for this uncertainty in the analysis and optimization of torpedo systems through the combination of Monte Carlo simulation with response surface methodology and metamodeling techniques. Additionally, various other methods that are appropriate to uncertainty analysis are discussed and analyzed. The thesis also advances a new approach towards examining robustness and risk: the treatment of probability of success (POS) as an independent variable. Examining the cost and performance tradeoffs between high and low probability of success designs, the decision-maker can make better informed decisions as to what designs are most promising and determine the optimal balance of risk, cost, and performance. Finally, the thesis examines the use of non-dimensionalization of parameters for torpedo design. The thesis shows that the use of non-dimensional torpedo parameters leads to increased knowledge about the scaleability of torpedo systems and increased performance of Designs of Experiments. The integration of these ideas concerning tactics, robust design with uncertainty, and non-dimensionalization of torpedo parameters has lead to the development of a general, powerful technique by which torpedo and other undersea weapon systems can be fully optimized, thereby increasing performance and decreasing the total cost of future weapon systems.

Thesis (M.S.)--Mississippi State University. Department of Mechanical Engineering. / Title from title screen. Includes bibliographical references.

The market for Insulated Gate Bipolar Transistor (IGBT) is growing and there is a need for techniques to improve the design, modeling and simulation of IGBT. In this thesis, we first developed a new method to optimize the layout and dimensions of IGBT circuits based on device simulation and combinatorial optimization. Our method leads to the optimal IGBT layout consisting of hexagons, which is 6 % more efficient in terms of performance (current per unit area) over that of squares, and up to 80 % more efficient than rectangles. We also explored several techniques to reduce the time used for device simulation. In particular, we developed an accurate Verilog-A description based on the Hefner model. For transient simulation, the time used by SPICE on the Verilog-A model is only 1/10000 of that used by device simulation on the device structure. The SPICE results, though contain some inaccuracies in the details, match device simulation in the general trend. Due to the effectiveness and efficiency of our methods, we propose their application in designing better power electronic circuits and shorter turn-around time.

No description available.

A series of novel algorithms for performing aerostructural shape and topology optimization are introduced and applied to the design of aircraft wings. An isoparametric level set method is developed for performing topology optimization of wings and other non-rectangular structures that must be modeled using a non-uniform, body-fitted mesh. The shape sensitivities are mapped to computational space using the transformation defined by the Jacobian of the isoparametric finite elements. The mapped sensitivities are then passed to the Hamilton-Jacobi equation, which is solved on a uniform Cartesian grid. The method is derived for several objective functions including mass, compliance, and global von Mises stress. The results are compared with SIMP results for several two-dimensional benchmark problems. The method is also demonstrated on a three-dimensional wingbox structure subject to fixed loading. It is shown that the isoparametric level set method is competitive with the SIMP method in terms of the final objective value as well as computation time. In a separate problem, the SIMP formulation is used to optimize the structural topology of a wingbox as part of a larger MDO framework. Here, topology optimization is combined with aerodynamic shape optimization, using a monolithic MDO architecture that includes aerostructural coupling. The aerodynamic loads are modeled using a threedimensional panel method, and the structural analysis makes use of linear, isoparametric, hexahedral elements. The aerodynamic shape is parameterized via a set of twist variables representing the jig twist angle at equally spaced locations along the span of the wing. The sensitivities are determined analytically using a coupled adjoint method. The wing is optimized for minimum drag subject to a compliance constraint taken from a 2g maneuver condition. The results from the MDO algorithm are compared with those of a sequential optimization procedure in order to quantify the benefits of the MDO approach. While the sequentially optimized wing exhibits a nearly-elliptical lift distribution, the MDO design seeks to push a greater portion of the load toward the root, thus reducing the structural deflection, and allowing for a lighter structure. By exploiting this trade-off, the MDO design achieves a 42% lower drag than the sequential result.