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A Study On The Reliability Analysis During Preliminary Design - A Rocket Motor ExampleBozkaya, Kenan 01 September 2006 (has links) (PDF)
To be competitive in the market, it is very important to design cost effective and reliable products. For this purpose, it is necessary to consider reliability as an integral part of the design procedure. Therefore, reliability which is a design parameter that affects cost and safety of a system should be taken into consideration in early phases since it is very difficult to change design at the later phases.
Reliability of a rocket motor can be evaluated by reliability testing but these tests are very expensive and difficult since the tests are destructive and test sample size is determined by the binomial law. Because of the difficulties in reliability testing, in early design phases reliability can be evaluated by using reliability prediction results.
This thesis report includes application of probabilistic approach for a solid rocket motor design to evaluate its reliability in preliminary design phase. In this study, it is aimed to assess the solid rocket motor ballistic performance reliability and casing structural reliability, determine important parameters affective on the solid rocket motor reliability and find a new design point to improve the reliability. Variations in dimensions and material properties are considered as the sources of failures and the limit states for acceleration, total impulse and maximum stress in the casing are approximated with response surface method by considering these variations. With the response surface functions, Monte Carlo simulation is used to assess failure probability and distributions of the rocket motor performance. Besides the assessment of the reliability, capability of the response surface functions to estimate the rocket motor performance and effects of the input parameters on the rocket motor performance and performance variation are also examined. By considering the effect of the input parameters, a new design point is proposed to decrease the total probability of failure.
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Využití optimalizačních metod při návrhu transsonického křídla s implementací základních konstrukčně pevnostních omezení / Modern Aerodynamic Optimization Methods Application to Transonic Wing Design with Implemented Basic Structural ConstraintsDoupník, Petr January 2010 (has links)
The thesis gives overview of complex aerodynamic optimization approach applied to business-jet aircraft wing design. Response surface method (RSM) potential was explored particularly. The efficiency of RSM approach for CFD based aerodynamic optimization was demonstrated. Basic structural requirements were successfully integrated to optimization – real multidisciplinary problem was solved. Some methods for evaluation of forces distribution along wingspan were explored. Thesis was solving within the frame of 6th EU FP integrated project CESAR.
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Optimering i organisk syntes : betingelser, system, syntesvägarHansson, Lars January 1990 (has links)
This thesis deals with different optimization problems encountered in organic synthesis. The use of response surface, sequential simplex and PLS techniques, for simultanious optimization of yield and suppression of side reactions is investigated. This is illustrated by an example of enamine synthesis, were a side reaction was a serious problem. The problem of efficient screening to find suitable catalysts and solvents in new reactions is also investigated. Here, the use of principal properties as selection criterion, is demonstrated with a new process for the silylation of a,ß-unsaturated ketones. The extension of the new method to bis silylation of 1,2- and 1,3-diketones is demonstrated. The total synthesis of (±)-geosmin is investigated by an approach aimed to reduce the number of necessary steps involved. The suggested strategy, is to find compatible solvents through several transformations in the sequence to accomplish one-pot multistep reactions. In this context an improved method for the preparation of 1,10-dimethyl-l(9)-octalone-2 was established. Comparison with previously reported total syntheses of (±)-geosmin was done. / digitalisering@umu
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Risk Estimation of Nonlinear Time Domain Dynamic Analyses of Large SystemsAzizsoltani, Hamoon, Azizsoltani, Hamoon January 2017 (has links)
A novel concept of multiple deterministic analyses is proposed to design safer and more damage-tolerant structures, particularly when excited by dynamic including seismic loading in time domain. Since the presence of numerous sources of uncertainty cannot be avoided or overlooked, the underlying risk is estimated to compare design alternatives. To generate the implicit performance functions explicitly, the basic response surface method is significantly improved. Then, several surrogate models are proposed. The advanced factorial design and Kriging method are used as the major building blocks. Using these basic schemes, seven alternatives are proposed. Accuracies of these schemes are verified using basic Monte Carlo simulations. After verifying all seven alternatives, the capabilities of the three most desirable schemes are compared using a case study. They correctly identified and correlated damaged states of structural elements in terms of probability of failure using only few hundreds of deterministic analyses. The modified Kriging method appears to be the best technique considering both efficiency and accuracy. Estimating the probability of failure, the post-Northridge seismic design criteria are found to be appropriate.
After verifying the proposed method, a Site-Specific seismic safety assessment method for nonlinear structural systems is proposed to generate a suite of ground excitation time histories. The information of risk is used to design a structure more damage-tolerant. The proposed procedure is verified and showcased by estimating risks associated with three buildings designed by professional experts in the Los Angeles area satisfying the post-Northridge design criteria for the overall lateral deflection and inter-story drift. The accuracy of the estimated risk is again verified using the Monte Carlo simulation technique. In all cases, the probabilities of collapse are found to be less than 10% when excited by the risk-targeted maximum considered earthquake ground motion satisfying the intent of the code. The spread in the reliability indexes for each building for both limit states cannot be overlooked, indicating the significance of the frequency contents. The inter story drift is found to be more critical than the overall lateral displacement. The reliability indexes for both limit states are similar only for few cases. The author believes that the proposed methodology is an alternative to the classical random vibration and simulation approaches. The proposed site-specific seismic safety assessment procedure can be used by practicing engineers for routine applications.
The proposed reliability methodology is not problem-specific. It is capable of handling systems with different levels of complexity and scalability, and it is robust enough for multi-disciplinary routine applications.
In order to show the multi-disciplinary application of the proposed methodology, the probability of failure of lead-free solders in Ball Grid Array 225 surface-mount packaging for a given loading cycle is estimated. The accuracy of the proposed methodology is verified with the help of Monte Carlo simulation. After the verification, probability of failure versus loading cycles profile is calculated. Such a comprehensive study of its lifetime behavior and the corresponding reliability analyses can be useful for sensitive applications.
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A Method For Robust Design Of Products Or Processes With Categorical ResponseErdural, Serkan 01 December 2006 (has links) (PDF)
In industrial processes decreasing variation is very important while achieving the targets. For manufacturers, finding out optimal settings of product and process parameters that are capable of producing desired results under great conditions is crucial. In most cases, the quality response is measured on a continuous scale. However, in some cases, the desired quality response may be qualitative (categorical). There are many effective methods to design robust products/process through industrial experimentation when the response variable is continuous. But methods proposed so far in the literature for robust design with categorical response variables have various limitations.
This study offers a simple and effective method for the analysis of categorical response data for robust product or process design. This method handles both location and dispersion effects to explore robust settings in an effective way. The method is illustrated on two cases: A foam molding process design and an iron-casting process design.
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A multi-configuration approach to reliability based structural integrity assessment for ultimate strengthKolios, Athanasios 11 1900 (has links)
Structural Reliability treats uncertainties in structural design systematically,
evaluating the levels of safety and serviceability of structures. During the past
decades, it has been established as a valuable design tool for the description of
the performance of structures, and lately stands as a basis in the background of
the most of the modern design standards, aiming to achieve a uniform
behaviour within a class of structures. Several methods have been proposed for
the estimation of structural reliability, both deterministic (FORM and SORM) and
stochastic (Monte Carlo Simulation etc) in nature.
Offshore structures should resist complicated and, in most cases, combined
environmental phenomena of greatly uncertain magnitude (eg. wind, wave,
current, operational loads etc). Failure mechanisms of structural systems and
components are expressed through limit state functions, which distinguish a
failure and a safe region of operation. For a jacket offshore structure, which
comprises of multiple tubular members interconnected in a three dimensional
truss configuration, the limit state function should link the actual load or load
combination acting on it locally, to the response of each structural member. Cont/d.
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Surrogate model-based design optimization of a mobile deployable structure for overpressure load and vehicular impact mitigationTellkamp, Daniela F 09 December 2022 (has links) (PDF)
Artificial Neural Network (ANN) ensemble and Response Surface Method (RSM) surrogate models were generated from Finite Element (FE) simulations to predict the overpressure load and vehicle impact response of a novel rapidly deployable protective structure. A Non-dominated Sorting Genetic Algorithm-II (NSGA-II) was used in conjunction with the surrogate models to determine structure topology input variable configurations which were suited to produce the optimal balance of minimum mass, minimum rotation angle, minimum displacement, and maximum total length of the deployable structure. The structure was designed to retract into a container, be lightweight to facilitate transportation, and be able to adapt to varying terrain slopes. This research demonstrates that, in comparison to the RSM, ANN ensembles can more accurately and efficiently be used for identifying optimal design solutions for multi-objective design problems when two surrogate models from the same method corresponding to separate FE models are used simultaneously in a NSGA-II.
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A multi-configuration approach to reliability based structural integrity assessment for ultimate strengthKolios, Athanasios Ioannis January 2010 (has links)
Structural Reliability treats uncertainties in structural design systematically, evaluating the levels of safety and serviceability of structures. During the past decades, it has been established as a valuable design tool for the description of the performance of structures, and lately stands as a basis in the background of the most of the modern design standards, aiming to achieve a uniform behaviour within a class of structures. Several methods have been proposed for the estimation of structural reliability, both deterministic (FORM and SORM) and stochastic (Monte Carlo Simulation etc) in nature. Offshore structures should resist complicated and, in most cases, combined environmental phenomena of greatly uncertain magnitude (eg. wind, wave, current, operational loads etc). Failure mechanisms of structural systems and components are expressed through limit state functions, which distinguish a failure and a safe region of operation. For a jacket offshore structure, which comprises of multiple tubular members interconnected in a three dimensional truss configuration, the limit state function should link the actual load or load combination acting on it locally, to the response of each structural member. Cont/d.
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Optimization and analysis by CFD of mixing-controlled combustion concepts in compression ignition enginesHernández López, Alberto 11 June 2018 (has links)
El trabajo presentado en esta Tesis está motivado por la necesidad de
los motores de combustión interna alternativos de reducir el consumo de combustible y
las emisiones de CO2 mientras se satisfacen las cada vez más restrictivas regulaciones
de emisiones contaminantes. Por lo tanto, el objetivo principal de este estudio es
optimizar un sistema de combustión de encendido por compresión controlado por
mezcla para probar su potencial como motores de futura generación. Con esta
meta se ha desarrollado un sistema automático que combina CFD con métodos de
optimización avanzados para analizar y entender las configuraciones óptimas.
Los resultados presentados en este trabajo se dividen en dos bloques principales.
El primero corresponde a la optimización de un sistema de encendido por compresión
convencional alimentado con diésel. El segundo se centra en un concepto de
combustión avanzado donde se ha sustituido el fuel por Dimetil-eter. En ambos casos,
el estudio no sólo halla una configuración óptima sino que también se describen las
relaciones causa/efecto entre los parámetros más relevantes del sistema de combustión.
El primer bloque aplica métodos de optimización no-evolutivos a un motor
medium-duty alimentado por diésel tratando de minimizar consumo a la vez que se
mantienen las emisiones contaminantes por debajo de los estándares de emisiones
contaminantes impuestos. Una primera parte se centra en la optimización de la
geometría de la cámara de combustión y el inyector. Seguidamente se extiende el
estudio añadiendo los settings de renovación de la carga de y de inyección al estudio,
ampliando el potencial de la optimización. El estudio demuestra el limitado potencial
de mejora de consumo que tiene el motor de referencia al mantener los niveles de
emisiones contaminantes. Esto demuestra la importancia de incluir parámetros de
renovación de la carga e inyección al proceso de optimización.
El segundo bloque aplica una metodología basada en algoritmos genéticos al
diseño del sistema de combustión de un motor heavy-duty alimentado con Dimetileter.
El estudio tiene dos objetivos, primero la optimización de un sistema de
combustión convencional controlado por mezcla con el objetivo de lograr mejorar
el consumo y reducir las emisiones contaminantes hasta niveles inferiores a los
estándares US2010. Segundo la optimización de un sistema de combustión trabajando
en condiciones estequiométricas acoplado con un catalizador de tres vías buscando
reducir consumo y controlar las emisiones contaminantes por debajo de los estándares
2030. Ambas optimizaciones incluyen tanto la geometría como los parámetros más
relevantes de renovación de la carga y de inyección. Los resultados presentan un
sistema de combustión convencional óptimo con una notable mejora en rendimiento y
un sistema de combustión estequiométrica que es capaz de ofrecer niveles de NOx
menores al 1% de los niveles de referencia manteniendo niveles competitivos de
rendimiento.
Los resultados presentados en esta Tesis ofrecen una visión extendida de las
ventajas y limitaciones de los motores MCCI y el camino a seguir para reducir las
emisiones de futuros sistemas de combustión por debajo de los estándares establecidos.
A su vez, este trabajo también demuestra el gran potencial que tiene el Dimetil-eter
como combustible para futuras generaciones de motores. / The work presented in this Thesis was motivated by the needs of
internal combustion engines (ICE) to decrease fuel consumption and CO2 emissions,
while fulfilling the increasingly stringent pollutant emission regulations. Then, the
main objective of this study is to optimize a mixing-controlled compression ignition
(MCCI) combustion system to show its potential for future generation engines. For
this purpose an automatic system based on CFD coupled with different optimization
methods capable of optimizing a complete combustion system with a reasonable time
cost was designed together with the methodology to analyze and understand the new
optimum systems.
The results presented in this work can be divided in two main blocks, firstly an
optimization of a conventional diesel combustion system and then an optimization of
a MCCI system using an alternative fuel with improved characteristics compared
to diesel. Due to the methodologies used in this Thesis, not only the optimum
combustion system configurations are described, but also the cause/effect relations
between the most relevant inputs and outputs are identified and analyzed.
The first optimization block applies non-evolutionary optimization methods in two
sequential studies to optimize a medium-duty engine, minimizing the fuel consumption
while fulfilling the emission limits in terms of NOx and soot. The first study targeted
four optimization parameters related to the engine hardware including piston bowl
geometry, injector nozzle configuration and mean swirl number. After the analysis of
the results, the second study extended to six parameters, limiting the optimization
of the engine hardware to the bowl geometry, but including the key air management
and injection settings. The results confirmed the limited benefits, in terms of fuel
consumption, with constant NOx emission achieved when optimizing the engine
hardware, while keeping air management and injection settings. Thus, including air
management and injection settings in the optimization is mandatory to significantly
decrease the fuel consumption while keeping the emission limits.
The second optimization block applies a genetic algorithm optimization
methodology to the design of the combustion system of a heavy-duty Diesel engine
fueled with dimethyl ether (DME). The study has two objectives, the optimization
of a conventional mixing-controlled combustion system aiming to achieve US2010
targets and the optimization of a stoichiometric mixing-controlled combustion system
coupled with a three way catalyst to further control NOx emissions and achieve
US2030 emission standards. These optimizations include the key combustion system
related hardware, bowl geometry and injection nozzle design as input factors, together
with the most relevant air management and injection settings. The target of the
optimizations is to improve net indicated efficiency while keeping NOx emissions, peak
pressure and pressure rise rate under their corresponding target levels. Compared to
the baseline engine fueled with DME, the results of the study provide an optimum
conventional combustion system with a noticeable NIE improvement and an optimum
stoichiometric combustion system that offers a limited NIE improvement keeping
tailpipe NOx values below 1% of the original levels.
The results presented in this Thesis provide an extended view of the advantages
and limitations of MCCI engines and the optimization path required to achieve future
emission standards with these engines. Additionally, this work showed how DME is a
promising fuel for future generation engines since it is able to achieve future emission
standards while maintaining diesel-like efficiency / El treball presentat en esta Tesi està motivat per la necessitat dels
motors de combustió interna alternatius de reduir el consum de combustible i les
emissions de CO2 mentres se satisfan les cada vegada mes restrictives regulacions
d'emissions contaminants. Per tant, l'objectiu principal d'este estudi es optimitzar
un sistema de combustió d'encesa per compressió controlat per mescla per a provar
el seu potencial com a motors de futura generació. Amb esta meta s'ha desenrotllat
un sistema automàtic que combina CFD amb mètodes d'optimització avançats per a
analitzar i entendre les configuracions òptimes. Els resultats presentats en este treball
es dividixen en dos blocs principals. El primer correspon a l'optimització d'un sistema
d'encesa per compressió convencional alimentat amb dièsel. El segon se centra en un
concepte de combustió avançat on s'ha substituït el fuel per Dimetil-eter. En ambdós
casos, l'estudi no sols troba una configuració òptima sinó que també es descriuen les
relacions causa/efecte entre els paràmetres més rellevants del sistema de combustió.
El primer bloc aplica mètodes d'optimització no-evolutius a un motor mediumduty
alimentat per dièsel tractant de minimitzar consum al mateix temps que
es mantenen les emissions contaminants per davall dels estàndards d'emissions
contaminants impostos. Una primera part se centra en l'optimització de la geometria
de la cambra de combustió i l'injector. A continuació s'estén l'estudi afegint els
settings de renovació de la càrrega de i d'injecció a l'estudi, ampliant el potencial de
l'optimització. L'estudi demostra el limitat potencial de millora de consum que té el
motor de referència al mantindre els nivells d'emissions contaminants. Açò demostra
la importància d'incloure paràmetres de renovació de la càrrega i injecció al procés
d'optimització.
El segon bloc aplica una metodologia basada en algoritmes genètics al disseny del
sistema de combustió d'un motor heavy-duty alimentat amb Dimetil-eter. L'estudi té
dos objectius, primer l'optimització d'un sistema de combustió convencional controlat
per mescla amb l'objectiu d'aconseguir millorar el consum i reduir les emissions
contaminants fins nivells inferiors als estàndards US2010. Segon l'optimització d'un
sistema de combustió treballant en condicions estequiomètriques acoblat amb un
catalitzador de tres vies buscant reduir consum i controlar les emissions contaminants
per davall dels estàndards 2030. Ambdós optimitzacions inclouen tant la geometria
com els paràmetres més rellevants de renovació de la càrrega i d'injecció. Els resultats
presenten un sistema de combustió convencional òptim amb una notable millora en
rendiment i un sistema de combustió estequiomètrica que és capaç d'oferir nivells
de NOx menors al 1% dels nivells de referència mantenint nivells competitius de
rendiment.
Els resultats presentats en esta Tesi oferixen una visió estesa dels avantatges i
limitacions dels motors MCCI i el camï que s'ha de seguir per a reduir les emissions
de futurs sistemes de combustió per davall dels estàndards establits. Al seu torn, este
treball també demostra el gran potencial que té el Dimetil-eter com a combustible
per a futures generacions de motors. / Hernández López, A. (2018). Optimization and analysis by CFD of mixing-controlled combustion concepts in compression ignition engines [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/103826 / TESIS
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Metoda odezvových ploch ve spojení s CFD pro tvarovou optimalizaci / Response surface method in connection with CFD for shape optimizationPleva, František January 2021 (has links)
This thesis is focused on shape optimization of Venturi´s nozzle with optimization method called response surface method. The first part of this work is concerned with the description of this method as well as explaining the basic principle. Furthermore, there is an explanation of the application of this method in synchronicity with CFD and its operating algorithm. The second part of this thesis is then focused on simple example with plane wing and simplified optimization of Venturi´s nozzle in which this method was tested. In the third part there is described full multiparameter shape optimalization of the nozzle for two geometries.
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