Orientador: Antonio Carlos Bannwart / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-07-20T08:34:29Z (GMT). No. of bitstreams: 1 Rossi_LucianoFernandodosSantos_D.pdf: 31189486 bytes, checksum: b5668903a52a4adff00b0520804c237d (MD5) Previous issue date: 1995 / Resumo: Este estudo teve como objetivo a análise de processos industriais, os mais abrangentes possíveis, visando sua otimização do ponto de vista energético-econômico. Neste intento, buscou-se apresentar não apenas um único ponto de otimalidade, mas um conjunto de opções que permita a um decisor escolher a situação mais conveniente. No desenvolvimento deste estudo foram utilizados um conjunto de Métodos de Otimização, dentre os quais podem ser destacados a Metodologia Pinch de Recuperação de Energia, baseada em uma redistribuição de potenciais térmicos dentro do processo analisado, e os Métodos originários da Programação Matemática, em especial a Programação Linear. Analisou-se em profundidade o caso, relativo à lndúsrtria de refino de Petróleo, de uma etapa de Craqueamento Catalítico da Refinaria de Paulínia, da PETROBRÁS. Entretanto, o conjunto de procedimentos aplicados neste trabalho mostrou-se eficiente quando da análise de outros segmentos industriais, em particular das lndústrias Química, de Alimentos e Petroquímica, como apresentado no decorrer deste trabalho. Este estudo mostra que é perfeitamente possível fazer-se uma análise energética e uma avaliação econômica de sua implantação, de uma maneira muito satisfatória e rápida / Abstract: This work deals with the industrial process analysis, includingvarious types and sizes, looking for their optimization fiom the economic and energetic point of view. Not only a single point of optimality was searched but a set of options which could permit to a decision maker to choose the best situation in each case. ln the development of this study were utilized a set of Optimization Methods, among which it can be mentioned the "Pinch Point Methodology" to heat recovery in networks, which is based in a redistribution of the thermal potentials of the process analyzed, and the methods originated tfom the Mathematics Programming, in special the Linear Programming. A deep analysiswas made on the case relative to an oil refinery.More precisely a part ofthe catalytic cracking of the Paulinia's Oil Refinery of PETROBRAS. The set of procedures applied in this work, it can be shown efficient when the analysis is applied to other industrial branches, in particular in the Chemistry, Food and Petrochemistry industries, as shown in throughout this work. This study shows that is possible to make an energetic analysis and an economic cost evaluation on the implementationof a process, in a fast and sactisfatory manner / Doutorado / Termica e Fluidos / Doutor em Engenharia Mecânica

Concrete is a brittle material prone to cracking due to its low tensile strength. Crack repairs are not only expensive and time-consuming but also increase the carbon footprint. Designing a novel concrete material possessing the ability to self-repair cracks would enhance its sustainability. Self-healing can be defined as a material’s ability to repair inner damage without any external intervention. In the case of concrete, the process can be autogenous, based on an optimized mix composition, or autonomous, when additional capsules containing some healing agent and/or bacteria spores are incorporated into the binder matrix. The first process uses unhydrated cement particles as the healing material while the other utilizes a synthetic material or bacteria precipitating calcite which are released into the crack from a broken capsule or activated by access to water and oxygen. The main disadvantages of the autonomous method are the loss of the fresh concrete workability, worsened mechanical properties, low efficiency, low survivability of the capsules and bacteria during mixing and the very high price. On the other hand, the autogenous self-healing was found to be more efficient, more cost effective, safer, and easier to implement in full-scale applications. Knowledge related to mechanisms and key factors controlling the autogenous self-healing is rather limited. Therefore, the aim of this research work was to better understand the autogenous self-healing process of concrete and to optimize the mix design and exposure conditions to maximize its efficiency. This licentiate thesis summarizes the main findings of the first 2.5 years of the PhD project. Several factors affecting autogenous self-healing were studied, including the amount of unhydrated cement, mix composition, age of material, self-healing duration and exposure conditions. The process was investigated both externally, at the surface, and deeper inside of the crack, by evaluating the crack closure and chemical composition of formed self-healing products. In addition, the flexural strength recovery was also studied. It was observed that a large amount of cement in the concrete mix does not ensure an efficient autogenous self-healing of cracks. A very dense and impermeable binder microstructure limited the transport of calcium and silicone ions to the crack and diminished the precipitation of the healing products. Addition fly ash increased the crack closure ratio close to the crack mouth, but its presence did not support the recovery of the flexural strength, presumably due to a very limited formation of load bearing phases inside the crack. Calcium carbonate was detected mainly at the crack mouth, whereas calcium silicate hydrate (C-S-H) and ettringite were found deeper inside the crack. The formation of C-S-H and ettringite presumably resulted in a regain of the flexural strength. On the other hand, calcite crystals formed close to the surface of the specimen controlled conditions inside the crack through its external closure. Healing exposure based on pure water appeared to be inefficient even despite the application of different temperature cycles and water volumes. The application of a phosphate-based retarding admixture in the curing water resulted in the highest self-healing efficiency. The admixture presumably inhibited the formation of a dense hydration shell on the surface of the unhydrated cement grains and promoted the precipitation of calcium phosphate compounds inside the crack. In addition, water mixed with microsilica particles caused a regain of the flexural strength through formation of C-S-H in the crack.

No description available.

The thesis deals with hyper duplex stainless austenitic-ferritic steels and their mechanical and castability properties. The evaluation of resistance to pitting corrosion is divided by PRE values. Steels with a PRE value higher than 48 belong to the group of hyper duplex steels. The theoretical part contains an introduction to the chemical composition, structure and properties of these steels. The practical part is focused on the conditions of tendency to crack castings during solidification and cooling. Furthermore, there is evaluated influence of intermetallic phases on mechanical properties.

This thesis discusses the types of bridge expansion joints certified for use in the Czech Republic and their disorders. The first part was a theoretical evaluation of expansion joint failures. The second part focused on clarifying the failure of anchor bolts at the cantilever expansion joint. On the basis of determining the cause was then designed a method for determining the durability of expansion joints. Prognosis life cycles corresponds records according to administrator- repair works.

In the last decades, significant improvements regarding the design, materials and technology of rock drills have been made. Likewise, in sheet metal forming, forming tools experience very high contact pressures when processing high strength steel sheets. In both applications components operate under extremely tough contact conditions that result in an accelerated component failure. Enhancements on mechanical properties of components material subjected to extreme contact conditions are highly required in order to withstand the application loads and prevent severe wear. The present thesis was focused on understanding of machinery component damage mechanisms under severe contact conditions. A case study of worn components used in rock drilling and sheet metal cold work was carried out. Thread joints from rock drilling and punches from sheet metal pressing were selected for the investigation. For these components, sliding contact under high contact pressure is a common load condition under the components usage. Then, to understand and quantify the influence of contact parameters, load and surface quality on material performance, laboratory simulations were performed. The results were used for a comparative analysis of the typical damage mechanisms observed in the tests and the case study of the components. The case study results showed that the threaded surfaces underwent severe plastic deformation due to the high-pressure sliding contact. The microstructure beneath the worn surface was altered and surface cracks and delamination were frequently observed at the worn surface. The dominant damage mechanism found on the investigated punches was adhesive wear. Material transfer adds friction stresses at the punch surface and ultimately, with repeated punch strokes, it leads to initiation and propagation of fatigue cracks. Wear process in thread joint and punch wear was simulated using the SOFS. The worn specimens tested experimentally showed similar wear mechanisms obtained in the case study. The thread joint wear simulation showed that the total damage at the worn surface was a result of adhesive wear, plastic deformation, and initiation and propagation of fatigue cracks. In addition, the results showed that the type of motion had a significant influence on the worn volume and crack initiation, and more severe wear was observed at reciprocal motion. The punch wear simulation showed that the friction quickly increased as work material from metal sheets transferred to the disc surface. The rate of the material transfer was strongly dependent on the combination of sheet material and tool steel. Further, the present experimental simulations were applicable to characterize and predict wear of components in the application. / Components used in rock drilling and sheet metal forming operate under harsh contact conditions that result in an early-life component failure. Wear and fatigue are considered as the most common damage mechanism for these components. Commonly, the service life of a component is designed based on its fatigue life. However, wear might have a significant effect on the components life too. Wear results in a surface damage that in turn may cause a fatigue crack initiation. Therefore, knowledge about wear of materials and components is a key factor in design and prediction of the lifetime of the components. In order to predict wear of a certain component, a thorough understanding of the component with regards to its material properties, application loads and working environment, and damage mechanisms is required. The overall aim of the present work was to define the typical wear mechanisms occurred on machinery components used in rock drilling and sheet metal forming. A comparative analysis of the case studies and results from performed laboratory tests simulated wear mechanisms in the applications highlighted wear mechanisms and factors influencing severity of wear in the applications. Obtained information is crucial for ranking and selection of the best material in the applications. / <p>The presentation will will be via zoom. PhD student will together with the supervisors will be in Karlstad while the opponent is in Luleå. </p>

The impact of temperatures (up to 1000 °C) with various heating rates of 5 °C/min, 200 °C/min, 300 °C/min, and according to ISO 834 standard fire curve on physical, mechanical, and thermal properties, as well as thermo-mechanical behaviors of granites were investigated. A new methodology was proposed for the heterogeneity characterization of rocks at the grain-size level in numerical simulation. The thermo-mechanical constitutive law is developed by combining the temperature-dependent relations of granite properties with classical Mohr-Coulomb model with strain-softening and tension cut-off. The proposed modelling strategy is able to replicate the thermal induced cracking which results in reduced peak strength, pronounced softening and transition from brittle to ductile behaviour. Research results help to understand the damage mechanisms of granite caused by fire or other high temperature conditions, and can be used to develop guidelines for repair and maintenance as well as assessment of risks of tunnels and historical buildings after fire accidents.

Diese Arbeit befasst sich mit der katalytischen Umsetzung von oxygenierten Kohlenwasserstoffen in einem Strömungsrohrreaktor bei 500 °C an mikroporösem Alumosilicat ZSM-5, an dem mesoporösem Alumosilicat Al-MCM-41 sowie an deren Mischphasen. Anhand der katalytischen Untersuchungen ist es möglich, für verschiedene Anforderungen an das Produktspektrum Empfehlungen an die Eigenschaften des zu verwendeten Katalysatorsystems zu formulieren. Hierfür wurden Untersuchungen zum Einfluss relevanter Syntheseprozessparameter auf die Zusammensetzung von Al-MCM-41/ZSM-5-Mischphasen vorgenommen. Die Synthese solcher Mischphasen wurde über einen 'Zwei-Template/Ein-Schritt“-Ansatz durchgeführt, der es erlaubte, die an das Katalysatorsystem gestellten Anforderungen durch eine geeignete Wahl der Syntheseparameter zu genügen. Während der Synthese der Al-MCM-41/ZSM-5-Mischphasen beobachtet man drei sich gegenseitig beeinflussenden Vorgänge, die durch, in der wässrigen Syntheselösung vorliegende, alumosilicatische Komponenten miteinander verknüpft sind: Die Auflösung und anschließende Restrukturierung einer nicht-porösen amorphen Phase, die Auflösung und Restrukturierung einer mesoporösen Al-MCM-41-Phase und die Kristallisation einer mikroporösen ZSM-5-Phase. Durch die Erhöhung des Al-Anteils im Synthesegel werden die ZSM-5-Kristallisation verlangsamt und der Schwerpunkt des Gleichgewichts dieser drei Vorgänge für einen gegebenen Reaktionszeitpunkt in Richtung der Bildung der mesoporösen Al-MCM-41-Phase verlagert. Der Einfluss des, in das jeweilige Katalysatorsystem eingebauten Aluminiums auf die katalytische Umsetzung von Oxygenaten manifestiert sich für die beiden Alumosilicate ZSM¬ 5 und Al MCM-41 auf verschiedene Weise. Eine Erhöhung des Al-Anteils in einem mikroporösen ZSM-5-Katalysatorsystem begünstigt den Verlauf von bimolekularen Reaktionen. Dies äußert sich in einem verstärkten Auftreten von Paraffin-bildenden Raktionen wie die Wasserstoff-Transfer-Reaktionen und/oder die Carboniumionen-Spaltung sowie in einer Dominanz von Aromaten-bildenen Reaktionen wie die Cyclisierung mit anschließender Dehydrierung und Aromatisierung. Dieser Effekt kann bei einer Erhöhung des Al-Anteils in einem mesoporösen Al-MCM-41-Katalysatorsystem nur im geringen Maße beobachtet werden. Jedoch nimmt mit sinkendem Si/Al-Verhältnis in beiden Katalysatorsystemen der Anteil an Produkten mit drei oder vier Kohlenstoffatomen zu. Zudem kann dabei eine beginnende Unabhängigkeit des gebildeten Produktspektrums von der Kettenlänge und der funktionellen Gruppe des umgesetzten Oxygenats beobachtet werden.:Inhaltsverzeichnis 1 Einleitung und Problemstellung 1 2 Grundlagen 4 2.1 Hydrothermale Synthese von Alumosilicaten 4 2.1.1 WÄSSRIGE CHEMIE UND HYDROTHERMALE BEHANDLUNG VON ALUMOSILICATEN 4 2.1.2 STRUKTUR UND BILDUNGSMECHANISMUS VON AL-MCM-41 5 2.1.3 STRUKTUR UND BILDUNGSMECHANISMUS VON ZSM-5 6 2.2 Katalytische Spaltung von Kohlenwasserstoffen an Alumosilicaten 9 2.2.1 NATUR UND LOKALISIERUNG VON SÄUREZENTREN 9 2.2.2 KOHLENWASSERSTOFF-POOL-MECHANISMUS UND VERKOKUNG 10 3 Experimentelles Vorgehen und analytische Messverfahren 14 3.1 Syntheseroute zur Herstellung von Al MCM 41/ZSM 5-Mischphasen, Al MCM 41 und ZSM-5 14 3.1.1 AL MCM 41/ZSM 5 MISCHPHASEN 14 3.1.2 AL-MCM-41 17 3.1.3 ZSM-5 17 3.2 Datenerhebung und -auswertung relevanter physikalisch-chemischer und festkörperanalytischer Charakterisierungsmethoden 17 3.2.1 PULVER-RÖNTGENDIFFRAKTOMETRIE 17 3.2.2 N2-PHYSISORPTION 19 3.2.3 TEMPERATUR-PROGRAMMIERTE AMMONIAK-DESORPTION 21 3.2.4 ELEMENTARANALYSE 23 3.2.5 27AL MAS NMR 24 3.2.6 THERMOGRAVIMETRISCHE ANALYSE 25 3.3 Katalytische Austestung und Analyse der Messdaten 26 3.3.1 VERSUCHSDURCHFÜHRUNG 26 3.3.2 ANALYSE UND AUSWERTUNG KATALYTISCHER MESSDATEN 27 3.3.3 DURCHGEFÜHRTE KATALYTISCHE TESTMESSUNGEN 29 4 Untersuchungen zum Bildungsmechanismus von Al MCM 41/ZSM 5-Mischphasen 33 4.1 Mechanistische Deutung 33 4.1.1 VORBETRACHTUNG 33 4.1.2 REAKTIONSABLAUF 34 4.1.3 UNTERSUCHUNG DER MESOPOROSITÄT 39 4.1.4 MORPHOLOGISCHE BETRACHTUNG 43 4.2 Wechselwirkungen der „Beeinflussungsfaktoren“ 45 4.2.1 EFFEKT VERSCHIEDENER AUTOKLAV-TYPEN 45 4.2.2 EFFEKT DES AL-ANTEILS IM SYNTHESEGEL 48 4.2.3 SYMBIOTISCHE EINFLUSSNAHME VON ALUMINIUM UND TENSIDEN 50 5 Charakterisierung verwendeter Katalysatormaterialien 52 5.1 ZSM-5 52 5.2 Al-MCM-41 57 5.3 Physikalische Mischungen aus Al-MCM-41 und ZSM-5 60 6 Katalytisches Spalten von Oxygenaten an ZSM 5 64 6.1 Katalytisches Spalten von Alkohol-Oxygenaten an ZSM 5 in Abhängigkeit des Si/Al Verhältnisses 64 6.1.1 PRODUKTANALYSE ANHAND DER KOHLENSTOFFANZAHL IM PRODUKTMOLEKÜL 65 6.1.2 PRODUKTANALYSE ANHAND EINZELNER STOFFGRUPPEN 68 6.2 Katalytisches Spalten von Carbonyl-Oxygenaten an ZSM 5 in Abhängigkeit des Si/Al Verhältnisses 71 6.2.1 PRODUKTANALYSE ANHAND DER KOHLENSTOFFANZAHL IM PRODUKTMOLEKÜL 72 6.2.2 PRODUKTANALYSE ANHAND EINZELNER STOFFGRUPPEN 76 6.3 Ableitung eines Kohlenwasserstoff-Pool Mechanismus zur Beschreibung des katalytischen Spaltens von Oxygenaten an ZSM 5 80 6.3.1 VEREINHEITLICHUNG DES OXYGENAT FEEDS ÜBER DESSEN DEOXYGENIERUNG 81 6.3.2 ASSIMILATION KURZKETTIGER OLEFINE DURCH EINEN KATALYTISCH AKTIVEN BEREICH 83 6.3.3 EINFLUSS DES PORENSYSTEMS UND AL-ANTEILS IM KATALYSATORSYSTEMS 85 6.3.4 BESCHREIBUNG DER PRODUKTBILDUNG EINZELNER STOFFGRUPPEN IN ABHÄNGIGKEIT WESENTLICHER REAKTIONSBEDINGUNGEN 87 7 Katalytisches Spalten von Triacylglyceriden an Al MCM 41 und physikalischen Mischungen aus Al-MCM-41 und ZSM-5 92 7.1 Gegenüberstellung des katalytischen Spaltens von Ethyloctanoat an Al MCM 41 und ZSM 5 in Abhängigkeit des Si/Al Verhältnisses 92 7.2 Anwendung des Kohlenwasserstoff-Pool Mechanismus zur Beschreibung des katalytischen Spaltens von Triacylglyceriden an physikalischen Mischungen aus Al MCM-41 und ZSM-5 97 7.3 Synthese-Struktur-Wirkungsprinzip 103 8 Zusammenfassung und Ausblick 106 Literatur 112 Abbildungsverzeichnis 127 Tabellenverzeichnis 139 Abkürzungsverzeichnis 141 Anhang 142 Veröffentlichungen 165 Eidesstattliche Erklärung 168

Nickel-based superalloys, an alloy system bases on nickel as the matrix element with the addition of up to 10 more alloying elements including chromium, aluminum, cobalt, tungsten, molybdenum, titanium, and so on. Through the development and improvement of nickel-based superalloys in the past century, they are well proved to show excellent performance at the elevated service temperature. Owing to the combination of extraordinary high-temperature mechanical properties, such as monotonic and cyclic deformation resistance, fatigue crack propagation resistance; and high-temperature chemical properties, such as corrosion and oxidation resistance, phase stability, nickel-based superalloys are widely used in the critical hot-section components in aerospace and energy generation industries. The success of nickel-based superalloy systems attributes to both the well-tailored microstructures with the assistance of carefully doped alloying elements, and the intently developed manufacturing processes. The microstructure of the modern nickel-based superalloys consists of a two-phase configuration: the intermetallic precipitates (Ni,Co)3(Al,Ti,Ta) known as γ′ phase dispersed into the austenite γ matrix, which is firstly introduced in the 1940s.  The recently developed additive manufacturing (AM) techniques, acting as the disruptive manufacturing process, offers a new avenue for producing the nickel-based superalloy components with complicated geometries. However, γ′ strengthened nickel-based superalloys always suffer from the micro-cracking during the AM process, which is barely eliminated by the process optimization. On this basis, the new compositions of γ′ strengthened nickel-based superalloy adapted to the AM process are of great interest and significance. This study sought to design novel γ′ strengthened nickel-based superalloys readily for AM process with limited cracking susceptibility, based on the understanding of the cracking mechanisms. A two-parameter model is developed to predict the additive manufacturability for any given composition of a nickel-based superalloy. One materials index is derived from the comparison of the deformation-resistant capacity between dendritic and interdendritic regions, while another index is derived from the difference of heat resistant capacity of these two spaces. By plotting the additive manufacturability diagram, the superalloys family can be categorized into the easy-to-weld, fairly-weldable, and non-weldable regime with the good agreement of the existed knowledge. To design a novel superalloy, a Cr-Co-Mo-W-Al-Ti-Ta-Nb-Fe-Ni alloy family is proposed containing 921,600 composition recipes in total. Through the examination of additive manufacturability, undesired phase formation propensity, and the precipitation fraction, one composition of superalloy, MAD542, out of the 921,600 candidates is selected. Validation of additive manufacturability of MAD542 is carried out by laser powder bed fusion (LPBF). By optimizing the LPBF process parameters, the crack-free MAD542 part is achieved. In addition, the MAD542 superalloy shows great resistance to the post-processing treatment-induced cracking. During the post-processing treatment, extensive annealing twins are promoted to achieve the recrystallization microstructure, ensuring the rapid reduction of stored energy. After ageing treatment, up to 60-65% volume fraction of γ′ precipitates are developed, indicating the huge potential of γ′ formation. Examined by the high-temperature slow strain rate tensile and constant loading creep testing, the MAD542 superalloy shows superior strength than the LPBF processed and hot isostatic pressed plus heat-treated IN738LC superalloy. While the low ductility of MAD542 is existed, which is expected to be improved by modifying the post-processing treatment scenarios and by the adjusting building direction in the following stages of the Ph.D. research. MAD542 superalloy so far shows both good additive manufacturability and mechanical potentials. Additionally, the results in this study will contribute to a novel paradigm for alloy design and encourage more γ′-strengthened nickel-based superalloys tailored for AM processes in the future. / <p>Additional funding agencies: Agora Materiae Graduate School for multidisiplinary PhD students at Linköping University, and Stiftelsen Axel Hultgren.</p>

This thesis aims to reveal the correlation between stress corrosion cracking propagation behavior and Schmid and Taylor factor mismatch using EBSD analysis. <div><br></div><div>Chloride induced stress corrosion cracking (CISCC) is one of the most vulnerable weaknesses for the widely used austenitic stainless steel in many industries. The complex nature of CISCC involves mechanical, electrochemical, and microstructural perspectives. The objective of this thesis is to assess CISCC phenomenon in austenitic stainless steel from the mechanical and crystallographic perspective, specifically on the effect of local strain and stress and anisotropic plastic deformation. Austenitic stainless steel 304L test coupons are bent in four-point bending fixtures to obtain tensile stress for CISCC, followed by corrosion experiment in boiling magnesium chloride solution. Stress state of the sample is evaluated by finite element analysis (FEA) and X-ray Diffraction Crystallography (XRD) prior corrosion test. Cross section of the cracked region are analyzed with Electron Backscatter Diffraction (EBSD) to analyze the relationship between CISCC behaviors and crystallographic features in the sample. Schmid factor and Taylor factor are used to quantitatively evaluate CISCC initiation and propagation behavior. It is learned that in polycrystalline FCC stainless steel, mismatch of Schmid factor and Taylor factor values in adjacent grains along crack path governs CISCC propagation susceptibility and path selection. Crack propagation factor competition model is proposed based on observations from EBSD maps, incorporating Schmid factor and Taylor factor mismatch, electrochemical condition of crack tip, and anisotropic properties. <br></div>