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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.
131

Inhõ Pyka Já, Inhõ Ba Já Djwy Dja Ba Ijôk Me Py o Utà além do que os olhos vêem: etnogênese, Xikrin-Mebêngôkre e a macrorregião de Marabá

MANAÇAS, Mirtes Emilia Almeida 20 March 2010 (has links)
Submitted by Irvana Coutinho (irvana@ufpa.br) on 2013-10-10T15:37:18Z No. of bitstreams: 2 license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) Dissertacao_InhoPykaJa.pdf: 7792544 bytes, checksum: 80243926012ed4cf29ae36c000b82cf2 (MD5) / Approved for entry into archive by Ana Rosa Silva(arosa@ufpa.br) on 2013-10-10T17:17:47Z (GMT) No. of bitstreams: 2 license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) Dissertacao_InhoPykaJa.pdf: 7792544 bytes, checksum: 80243926012ed4cf29ae36c000b82cf2 (MD5) / Made available in DSpace on 2013-10-10T17:17:47Z (GMT). No. of bitstreams: 2 license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) Dissertacao_InhoPykaJa.pdf: 7792544 bytes, checksum: 80243926012ed4cf29ae36c000b82cf2 (MD5) Previous issue date: 2010 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Partindo de considerações teóricas acerca do conceito de Etnogênese, a dissertação aborda o processo dos Xikrin de REfazer, REestruturar, REconfigurar e REelaborar suas relações políticas, sociais, culturais e econômicas em todas as áreas de sua vida, diante do encontro com o ―outro‖, desencadeando uma nova identidade individual e coletiva. Verifica-se, desde os tempos míticos aos dias atuais, que o processo histórico da relação Xikrin versus ―outro‖, pode ser percebido a partir dos traços existentes em seus corpos através da pintura e ornamentação, sendo a pintura corporal uma das ferramentas utilizadas como arma de resistência, no intuito de manter a existência de sua comunidade da melhor maneira possível, dentro de suas perspectivas de vida. / Based on theoretical considerations on the concept of Ethnogenesis, this dissertation addresses the process of how the Xikrin Indians remake, restructure, reconfigure and reelaborate their political, social, cultural and economic relations in all areas of their lives, when meeting the ―other‖, initiating a new collective and individual identity. One verifies that since the mythical times and until today, the historical process of the Xikrin versus ―the other‖, may be perceived from the their existing body paintings and ornaments, the first being one of the tools used as defense armament, aiming to maintain, in the best way possible, the existence of their community within their live perspectives.
132

Comparação do efeito da fragilização por hidrogênio em aços com resistência à tração acima de 1000 MPa

Rosado, Diego Belato January 2011 (has links)
Este trabalho tem por objetivo avaliar os efeitos do hidrogênio em três diferentes tipos de aços de alta resistência mecânica. São descritos os fenômenos de introdução, difusão e aprisionamento de hidrogênio (H) dentro dos metais, em conjunto com os diferentes tipos de danos provocados devido à presença do hidrogênio. Os materiais de estudo são aços da família Advanced High Strength Steels (AHSS): aços Dual Phase (DP 1000 e DP 1200) e aço Martensítico (M 190). A introdução de hidrogênio nos materiais foi realizada através de carregamento catódico, o qual é representativo para as condições industriais a que se destinam. De modo a avaliar a influência do H nas propriedades mecânicas dos aços, os seguintes ensaios foram propostos: ensaio de carregamento com H, para determinar o conteúdo total de H (saturação) e conteúdo de H difusível (suscetibilidade a fragilização); ensaio de tração ao ar, para determinar a tensão no final da região elástica e resistência à tração na região do entalhe e ensaio de tração com carga constante em ambiente hidrogenado, para avaliar os efeitos provocados pela presença do H e determinar o patamar abaixo do qual o H não apresenta efeito crítico sobre o material. Os efeitos provocados pela aplicação de diferentes densidades de correntes (0,2 – 1,0 mA/cm²) foram avaliados nos ensaios de quantificação de H difusível. Conforme os resultados obtidos todos os aços apresentaram perdas na resistência mecânica à tração quando em ambiente hidrogenado, ou seja, sofreram fragilização por H. Os aços DP 1200 e M 190 (de microestrutura predominantemente martensítica) foram fortemente afetados, conforme evidenciado pela notável queda nos valores de tensão necessários para provocar a falha. Por outro lado, o aço DP 1000, de menor resistência mecânica, demonstrou menor suscetibilidade à fragilização, o que é atribuído a menor permeabilidade do H na microestrutura austenítica. / This work aims to evaluate the effects of hydrogen in three high- strength steel grades. The phenomena of hydrogen (H) entry, transport and trapping inside the metals, together with the different types of damages due to the presence of hydrogen are presented. The study materials are a range of AHSS steel grades: Dual Phase Steel (DP 1000 and DP 1200) and Martensitic Steel (M 190). The hydrogen entry was performed by cathodic charging, which is suitable for industrial applications. In order to evaluate the influence of H on the steel mechanical properties, the following tests were done: H charging, to measure total H content (saturation point) and diffusible H content (embrittlement susceptibility); uniaxial tensile test of uncharged samples to determine notched tensile strength values and the strength levels at the end of elastic region and constant load tensile testing carried out in hydrogen environment, to determine the threshold values where hydrogen has an effect on the material. DP 1200 and M 190 were strongly affected by H pre-charging, as shown by the significant drop in stress required to break them. On the other hand, DP 1000 showed a lower embrittlement susceptibility, which is attributed to its lower mechanical strength. The current densities effects (0.2 up to 1.0 mA/cm²) were evaluated during H charging to measure diffusible H content. All steels showed a drop in the tensile strength i.e. experienced hydrogen embrittlement. Steels with higher tensile strength, as DP 1200 and M 190, showed a much bigger drop that is related to the favorable characteristics of martensitic microstructure regarding to the hydrogen permeability and diffusivity.
133

Development of simulation tools, control strategies, and a hybrid vehicle prototype

Pei, Dekun 14 November 2012 (has links)
This thesis (1) reports the development of simulation tools and control strategies for optimizing hybrid electric vehicle (HEV) energy management, and (2) reports the design and testing of a hydraulic hybrid school bus (HHB) prototype. A hybrid vehicle is one that combines two or more energy sources for use in vehicle propulsion. Hybrid electric vehicles have become popular in the consumer market due to their greatly improved fuel economy over conventional vehicles. The control strategy of an HEV has a paramount effect on its fuel economy performance. In this thesis, backward-looking and forward-looking simulations of three HEV architectures (parallel, power-split and 2-mode power-split) are developed. The Equivalent Cost Minimization Strategy (ECMS), which weights electrical power as an equivalent fuel usage, is then studied in great detail and improvements are suggested. Specifically, the robustness of an ECMS controller is improved by linking the equivalence factor to dynamic programming and then further tailoring its functional form. High-fidelity vehicle simulations over multiple drive-cycles are performed to measure the improved performance of the new ECMS controller, and to show its potential for online application. While HEVs are prominent in the consumer market and studied extensively in current literature, hydraulic hybrid vehicles (HHVs) only exist as heavy utility vehicle prototypes. The second half of this thesis reports design, construction, and testing of a hydraulic hybrid school bus prototype. Design considerations, simulation results, and preliminary testing results are reported, which indicate the strong potential for hydraulic hybrids to improve fuel economy in the school bus vehicle segment.
134

PREDICTION PAR ELEMENTS FINIS DE LA RUPTURE DES ACIERS DUAL_PHASE EN UTILISANT UN MODELE DE GURSON AVANCE

Fansi, Joseph 02 July 2013 (has links) (PDF)
L'actuelle investigation numérique du Gurson-Tvergaard-Needleman (GTN) modèle avancé est une extension du travail de Ben Bettaieb et al. (2011). Le modèle a été implémenté à l'aide d'une sous routine (VUMAT) contenu dans le code commerciale d'éléments finis Abaqus/explicit. Le modèle d'endommagement améliore l'original en intégrant les trois mécanismes d'endommagement, la nucléation, la croissance, et la coalescence des cavités. Le modèle d'endommagement intègre les lois de nucléation et de croissance basés sur les phénomènes purement physiques. Ces nouvelles contributions incluant l'influence de l'écrouissage cinématique, ont été validées par les résultats de mesures expérimentales de tomographie à rayon X à haute résolution. Aussi, l'implémentation numérique de l'écrouissage cinématique dans le modèle modifié a contraint de proposer et de réarranger la définition de la triaxialité que l'on trouve habituellement dans la littérature. A coté de cela, un second critère d'initiation à la rupture basé sur l'ultime distance inter-cavités a été inclue afin de localiser et de quantifier avec plus de précision la distribution des déformations peu avant que le matériau ne casse complètement. L'actuel modèle d'endommagement a été appliqué dans des conditions industrielles pour prédire l'évolution de l'endommagement, l'état de contraintes, et l'initiation à la rupture pour différentes géométries de tôles et sur des essais d'emboutissage de tôles minces.
135

Comparação do efeito da fragilização por hidrogênio em aços com resistência à tração acima de 1000 MPa

Rosado, Diego Belato January 2011 (has links)
Este trabalho tem por objetivo avaliar os efeitos do hidrogênio em três diferentes tipos de aços de alta resistência mecânica. São descritos os fenômenos de introdução, difusão e aprisionamento de hidrogênio (H) dentro dos metais, em conjunto com os diferentes tipos de danos provocados devido à presença do hidrogênio. Os materiais de estudo são aços da família Advanced High Strength Steels (AHSS): aços Dual Phase (DP 1000 e DP 1200) e aço Martensítico (M 190). A introdução de hidrogênio nos materiais foi realizada através de carregamento catódico, o qual é representativo para as condições industriais a que se destinam. De modo a avaliar a influência do H nas propriedades mecânicas dos aços, os seguintes ensaios foram propostos: ensaio de carregamento com H, para determinar o conteúdo total de H (saturação) e conteúdo de H difusível (suscetibilidade a fragilização); ensaio de tração ao ar, para determinar a tensão no final da região elástica e resistência à tração na região do entalhe e ensaio de tração com carga constante em ambiente hidrogenado, para avaliar os efeitos provocados pela presença do H e determinar o patamar abaixo do qual o H não apresenta efeito crítico sobre o material. Os efeitos provocados pela aplicação de diferentes densidades de correntes (0,2 – 1,0 mA/cm²) foram avaliados nos ensaios de quantificação de H difusível. Conforme os resultados obtidos todos os aços apresentaram perdas na resistência mecânica à tração quando em ambiente hidrogenado, ou seja, sofreram fragilização por H. Os aços DP 1200 e M 190 (de microestrutura predominantemente martensítica) foram fortemente afetados, conforme evidenciado pela notável queda nos valores de tensão necessários para provocar a falha. Por outro lado, o aço DP 1000, de menor resistência mecânica, demonstrou menor suscetibilidade à fragilização, o que é atribuído a menor permeabilidade do H na microestrutura austenítica. / This work aims to evaluate the effects of hydrogen in three high- strength steel grades. The phenomena of hydrogen (H) entry, transport and trapping inside the metals, together with the different types of damages due to the presence of hydrogen are presented. The study materials are a range of AHSS steel grades: Dual Phase Steel (DP 1000 and DP 1200) and Martensitic Steel (M 190). The hydrogen entry was performed by cathodic charging, which is suitable for industrial applications. In order to evaluate the influence of H on the steel mechanical properties, the following tests were done: H charging, to measure total H content (saturation point) and diffusible H content (embrittlement susceptibility); uniaxial tensile test of uncharged samples to determine notched tensile strength values and the strength levels at the end of elastic region and constant load tensile testing carried out in hydrogen environment, to determine the threshold values where hydrogen has an effect on the material. DP 1200 and M 190 were strongly affected by H pre-charging, as shown by the significant drop in stress required to break them. On the other hand, DP 1000 showed a lower embrittlement susceptibility, which is attributed to its lower mechanical strength. The current densities effects (0.2 up to 1.0 mA/cm²) were evaluated during H charging to measure diffusible H content. All steels showed a drop in the tensile strength i.e. experienced hydrogen embrittlement. Steels with higher tensile strength, as DP 1200 and M 190, showed a much bigger drop that is related to the favorable characteristics of martensitic microstructure regarding to the hydrogen permeability and diffusivity.
136

Comparação do efeito da fragilização por hidrogênio em aços com resistência à tração acima de 1000 MPa

Rosado, Diego Belato January 2011 (has links)
Este trabalho tem por objetivo avaliar os efeitos do hidrogênio em três diferentes tipos de aços de alta resistência mecânica. São descritos os fenômenos de introdução, difusão e aprisionamento de hidrogênio (H) dentro dos metais, em conjunto com os diferentes tipos de danos provocados devido à presença do hidrogênio. Os materiais de estudo são aços da família Advanced High Strength Steels (AHSS): aços Dual Phase (DP 1000 e DP 1200) e aço Martensítico (M 190). A introdução de hidrogênio nos materiais foi realizada através de carregamento catódico, o qual é representativo para as condições industriais a que se destinam. De modo a avaliar a influência do H nas propriedades mecânicas dos aços, os seguintes ensaios foram propostos: ensaio de carregamento com H, para determinar o conteúdo total de H (saturação) e conteúdo de H difusível (suscetibilidade a fragilização); ensaio de tração ao ar, para determinar a tensão no final da região elástica e resistência à tração na região do entalhe e ensaio de tração com carga constante em ambiente hidrogenado, para avaliar os efeitos provocados pela presença do H e determinar o patamar abaixo do qual o H não apresenta efeito crítico sobre o material. Os efeitos provocados pela aplicação de diferentes densidades de correntes (0,2 – 1,0 mA/cm²) foram avaliados nos ensaios de quantificação de H difusível. Conforme os resultados obtidos todos os aços apresentaram perdas na resistência mecânica à tração quando em ambiente hidrogenado, ou seja, sofreram fragilização por H. Os aços DP 1200 e M 190 (de microestrutura predominantemente martensítica) foram fortemente afetados, conforme evidenciado pela notável queda nos valores de tensão necessários para provocar a falha. Por outro lado, o aço DP 1000, de menor resistência mecânica, demonstrou menor suscetibilidade à fragilização, o que é atribuído a menor permeabilidade do H na microestrutura austenítica. / This work aims to evaluate the effects of hydrogen in three high- strength steel grades. The phenomena of hydrogen (H) entry, transport and trapping inside the metals, together with the different types of damages due to the presence of hydrogen are presented. The study materials are a range of AHSS steel grades: Dual Phase Steel (DP 1000 and DP 1200) and Martensitic Steel (M 190). The hydrogen entry was performed by cathodic charging, which is suitable for industrial applications. In order to evaluate the influence of H on the steel mechanical properties, the following tests were done: H charging, to measure total H content (saturation point) and diffusible H content (embrittlement susceptibility); uniaxial tensile test of uncharged samples to determine notched tensile strength values and the strength levels at the end of elastic region and constant load tensile testing carried out in hydrogen environment, to determine the threshold values where hydrogen has an effect on the material. DP 1200 and M 190 were strongly affected by H pre-charging, as shown by the significant drop in stress required to break them. On the other hand, DP 1000 showed a lower embrittlement susceptibility, which is attributed to its lower mechanical strength. The current densities effects (0.2 up to 1.0 mA/cm²) were evaluated during H charging to measure diffusible H content. All steels showed a drop in the tensile strength i.e. experienced hydrogen embrittlement. Steels with higher tensile strength, as DP 1200 and M 190, showed a much bigger drop that is related to the favorable characteristics of martensitic microstructure regarding to the hydrogen permeability and diffusivity.
137

La relativisation prénominale / Prenominal Relative Clause

Wu, Tong 01 December 2011 (has links)
Notre étude porte sur la proposition relative prénominale (Prpré), dans le cadre de la typologique et du modèle minimaliste de la grammaire générative. Le premier chapitre pose pour objets principaux de définir la proposition relaive (PR) et d’établir trois typologies concernant la PR. Le deuxième chapitre spécifie la PRpré et les langues à PRpré. Nous restreindrons notre étude aux langues à PRpré première. Nous resituons ces langues dans leur répartition géographique et leur affiliation linguistique pour montrer que les facteurs géographiques et génériques ne peuvent pas rendre compte de la PRpré. Le troisième chapitre expose en détail les analyses théoriques générativistes sur la PR et rend compte de la possibilité de les intégrer dans le programme minimaliste. Le quatrième chapitre est consacré, dans la première partie, à analyser la PRpré dans une perspective minimaliste suivant Kayne (1994). Nous tentons de proposer des dérivations permettant de linéariser correctement les éléments suivants dans le SD de la PRpré : article défini, démonstratif, PR, relativiseur et nom tête. Le syntagme [SD SDem [D° [SC SN [C° [SI tSN]]]]] sert de base pour les différentes dérivations générant les 16 linéarités des éléments dans SD repérées dans les langues à PRpré. Ensuite, nous analysons les effets de reconstruction en suivant Bianchi (2004). Nous adopterons l’idée de "case-stacking" de Pesetsky (2009a et 2009b) pour le conflit casuel/Casuel et aussi pour le trou syntaxique et l’idée de Boeckx (2003) pour le pronom résomptif. Dans la deuxième section, nous présenterons l’analyse de Cinque (2003/8) pour la PRpré. Le cinquième chapitre expose les caractéristiques typologiques non-intrinsèques de la PRpré. / This study concerns the prenominal relative clause in the framework of typology and of the Minimalist model of Generative Grammar. The first chapter defines the relative clause and establishes three typologies on relative clauses. The second chapter specifies what are "prenominal relative clause" and "primary prenominal relative clause languages". These languages are presented according to their geographic distribution and linguistic affiliation, but the geographic and genetic factors cannot analyze properly the prenominal relative clause, because it can be better analyzed according to its typological properties. The third chapter exposes in detail the generative analyses on relative clauses, i.e. Head External Analysis, Head Raising Analysis and Matching Analysis, and discusses how they can be integrated into the Minimalist Program. The fourth chapter analyzes the prenominal relative clause in the Minimalist framework according to Kayne (1994). It is shown how the following elements in the DP of the prenominal relative clause can be correctly linearized, i.e. definite article, demonstrative, relative clause, relativizer and head noun. The basic structure is [DP DemP [D° [CP NP [C° [IP tNP]]]]]. It can derive the 16 linear orders found in prenominal relative clause languages. The reconstruction effect is analyzed according to Bianchi (2004), the case/Case conflict and the gaps according to Pesetsky (2009a & 2009b) and the resumptive pronoun according to Boeckx (2003). In the last section, another analysis, i.e. Cinque (2003/8), is applied to the prenominal relative clauses. The fifth chapter talks about non-intrinsic typological properties of the prenominal relative clause.
138

Barriers to Near-miss Reporting in the Maritime Domain

Köhler, Fredrik January 2010 (has links)
The catastrophic accident of the ferry Herald of Free Enterprise made it clear that the development of accident prevention in the maritime domain must not only rely on negative events but rather on proactive measures.Near-miss reporting is becoming widespread as a proactive tool for accident prevention in various domains. This thesis aims to examine and identify barriers to near-miss reporting through studying the national reporting system INSJÖ and local company specific systems in the Swedish maritime domain.Interviews with representatives from Swedish shipping companies (designated persons responsible for safety work in each company and officers responsible for the reporting at sea) were conducted as a means of data collection. Based on the data two separate analyses were made; one in a naturalistic fashion and one using a framework of barriers and incentives derived from various social technical domains in which near-miss reporting has been institutionalized.The results of the two analyses highlight differences regarding how and with whom information should be shared. The therapeutic factor, to teach and learn from others was emphasized as important by the majority of the interviewees. Further, potential external influences, issues concerning anonymity and the risk of rehearsed benefits of reporting are also made visible. Finally, critique against the accident-ratio models, that introduced the near-miss concept, is presented and it is argued that these models might be too simplistic to explain why accidents occur.It is concluded that, in order to create effective reporting systems and to decrease the risk of creating a disparity between rehearsed benefits and how the system is used in reality, it is important to give the personnel ownership of their own reporting system and the knowledge of how and why to use it. Nevertheless, near-miss reporting might be used as a powerful tool and incentive for proactive work and accident prevention.
139

Route Based Optimal Control Strategy for Plug-In Hybrid Electric Vehicles

Almgren, Johan, Elingsbo, Gustav January 2017 (has links)
More restrictive emission legislations, rising fuel prices and the realisation that oil is a limited resource have lead to the emergence of the hybrid electric vehicles.To fully utilise the potential of the hybrid electric vehicles, energy management strategies are needed. The main objective of the strategy is to ensure that the limited electric energy is utilised in an efficient manner.This thesis develops and evaluates an optimisation based energy management strategy for plug-in hybrid electric vehicles. The optimisation methods used are based on a dynamic programming and ECMS approach. The strategy is validated against Vsim, Volvo Cars' performance and fuel consumption analysis tool as well as against strategies where parts of the optimisation is replaced by logic. The results show that the developed strategy consumes less fuel both compared to the corresponding Vsim strategy and the logic strategies.
140

Modelling of plasticity and fracture behaviors of dual-phase steel / Modélisation de la plasticité et la rupture de l’acier à double phase

Hou, Yuliang 26 October 2016 (has links)
L’acier à double phase (DP) a été développé par l'industrie automobile pour le but de réduire le poids, l'amélioration de la performance de la sécurité et l'efficacité énergétique. Habituellement, l'acier DP contient des îlots de martensite dure noyée dans une matrice de ferrite doux. La synergie entre ces deux phases avec la microstructure inhomogène présente d'excellentes propriétés mécaniques. Les propriétés mécaniques (comportements de plasticité et de dégâts) d'acier DP sont principalement dérivés de sa microstructure, par exemple, la fraction de volume, la taille, la distribution et la morphologie de chaque phase constituante. Les approches micromécaniques sont largement appliquées pour prédire la plasticité et d'autres propriétés mécaniques de l'acier DP selon divers scénarios de chargement. Dans ce travail, la modélisation micromécanique de l'acier DP a été réalisée en utilisant des microstructures réelles ou artificielles. Une véritable microstructure est obtenue à partir de l'image métallographique, tandis qu'un générateur de microstructure artificielle à l'aide d'un algorithme d'affectation de phase améliorée basée sur l'optimisation de la topologie matériau est proposé d'étudier les propriétés mécaniques. Dans ce générateur artificiel, un processus d'affectation de phase est réalisé sur une mosaïque de Voronoï modifié pour obtenir une mesure représentative de l'élément de volume (VER) avec une bonne convergence. La méthode proposée comprend également une réduction appropriée décomposition orthogonale (POD) des courbes de débit (instantanés), qui sont calculés en utilisant le schéma asymptotique homogénéisation d'extension (AEH), pour identifier le contrôle des paramètres optimaux pour l'acier DP. Cette méthode numérique est vérifiée en utilisant DP590 et DP980 aciers qui indiquent un bon accord avec la contrainte d'écoulement à partir de mesures et prédiction de RVE basés sur de vraies microstructures. Les prédictions des modèles de déformation plastique, y compris des bandes de cisaillement en utilisant la microstructure artificielle ressemblent étroitement le comportement mécanique réel dans des conditions de chargement similaires. En outre, une interpolation a été adoptée pour obtenir une corrélation entre ces paramètres de contrôles basés sur l'identification des différents aciers DP. En outre, un modèle de substitution bi-niveau réduit est élaboré et présenté pour identifier les paramètres matériels du critère de rupture de Mohr-Coulomb (MMC). En utilisant cette méthode, le processus d'identification devient possible avec un nombre limité de tests Expérimentaux. La méthode combine des éléments critiques locaux associés à des modèles globaux. Le modèle de substitution de la souche de fracture construit en utilisant l'approximation diffuse et les éléments locaux, réduit le coût de calcul pour la recherche des paramètres matériels. Des simulations de fracturation sont effectuées globales pour mettre à jour la déformation à la rupture de la cible et pour calculer le déplacement de l'apparition de la panne correspondante. Des résultats probants sont obtenus par application successive de la conception de l'expérience (DOE) et l'amélioration des algorithmes de transformation de l'espace de conception. Le protocole d'identification proposée est validé avec de l'acier DP590. Robustesse de la méthode est confirmée par des valeurs initiales différentes. Ces investigations numériques fournissent nouvelle direction pour les simulations multi-échelles de la plasticité et de dégâts des comportements d'acier DP. De plus, ils contribuent efficacement à combler le fossé entre la recherche scientifique et à l'application de l'ingénierie des matériaux hétérogènes. / Dual-phase (DP) steel has been developed by automotive industry for the purpose of weight reduction, improvement in safety performance and fuel efficiency. Usually, DP steel contains hard martensite islands embedded in a soft ferrite matrix. Synergy between these two phases with the inhomogeneous microstructure exhibits excellent mechanical properties. The mechanical properties (plasticity and damage behaviors) of DP steel are mostly derived from its microstructure, e.g., volume fraction, size, distribution and morphology of each constituent phase. Micromechanical approaches are vastly applied to predict plasticity and other mechanical properties of DP steel under various loading scenarios. In this work, micromechanical modelling of DP steel has been performed using real or artificial microstructures. A real microstructure is obtained from metallographic image, while an artificial microstructure generator with an enhanced phase assignment algorithm based on material topology optimization is proposed to investigate the mechanical properties. In this artificial generator, phase assignment process is performed on a modified Voronoï tessellation to achieve the tailored representative volume element (RVE) with a good convergence. The proposed method also includes a proper orthogonal decomposition (POD) reduction of flow curves (snapshots), which are computed using the asymptotic extension homogenization (AEH) scheme, to identify the optimal controlling parameters for DP steel. This numerical method is verified using DP590 and DP980 steels that indicate a good agreement with the flow stress from measurements and RVE prediction based on real microstructures. Predictions of plastic strain patterns including shear bands using the artificial microstructure closely resemble the actual mechanical behavior under similar loading conditions. Moreover, an interpolation has been adopted to obtain a correlation between these controlling parameters based on the identification for various DP steels. Additionally, a bi-level reduced surrogate model is developed and presented to identify the material parameters of the Mohr-Coulomb (MMC) fracture criterion. Using this method, the identification process becomes feasible with a limited number of experimental tests. The method combines local critical elements associated with global models. The surrogate model of fracture strain constructed using the diffuse approximation and the local elements, reduced the computational cost for searching material parameters. Global fracture simulations are performed to update the target fracture strain and to compute the corresponding failure onset displacement. Convincing results are obtained via successive application of design of experiment (DOE) and enhanced design space transformation algorithms. The proposed identification protocol is validated with DP590 steel. Robustness of the method is confirmed with different initial values. These numerical investigations provide new direction for multiscale simulations of the plasticity and damage behaviors of DP steel. Moreover, they efficiently contribute to bridge the gap between scientific research and engineering application of heterogeneous materials.

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