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Author: W. Steven Johnson Publisher: ISBN: Category : Angled pre-crack Languages : en Pages : 13
Book Description
An important application of nickel base superalloys is in the industrial gas turbine (IGT) industry, where the high temperature capabilities of these alloys are exploited. Extensive testing has focused on the tensile and fatigue properties of single crystal versions of these alloys. The single crystals are utilized in the hottest parts of the turbine, where a detailed knowledge of material behavior is critical to design and life assessment. However, studies on the effects of temperature on fracture toughness have largely been absent in both past and present literature. Therefore, the goal of this research is to characterize the fracture toughness properties of a second-generation single crystal nickel superalloy at elevated temperatures. The experimental methods follow ASTM guidelines, as does the analysis for the elastic (K) and plastic (J integral) deformation. The toughness values were invalid for plain strain fracture toughness, but this should be expected from a structural material. In spite of this fact, both the K- and J- based analyses reveal consistent trends. Increased plasticity at elevated temperatures results in an overall increase in toughness as temperature increases. Unusual cases with inclined pre-cracks and microstructural defects did not technically yield valid results, although they were consistent with the nominal cases. Overall, the results indicate that the toughness of single crystal nickel alloys is actually quite high. Thus, the lack of work in this subject is understandable. However, it would seem that any design and lifing work would benefit from an understanding of such a fundamental property.
Author: W. Steven Johnson Publisher: ISBN: Category : Angled pre-crack Languages : en Pages : 13
Book Description
An important application of nickel base superalloys is in the industrial gas turbine (IGT) industry, where the high temperature capabilities of these alloys are exploited. Extensive testing has focused on the tensile and fatigue properties of single crystal versions of these alloys. The single crystals are utilized in the hottest parts of the turbine, where a detailed knowledge of material behavior is critical to design and life assessment. However, studies on the effects of temperature on fracture toughness have largely been absent in both past and present literature. Therefore, the goal of this research is to characterize the fracture toughness properties of a second-generation single crystal nickel superalloy at elevated temperatures. The experimental methods follow ASTM guidelines, as does the analysis for the elastic (K) and plastic (J integral) deformation. The toughness values were invalid for plain strain fracture toughness, but this should be expected from a structural material. In spite of this fact, both the K- and J- based analyses reveal consistent trends. Increased plasticity at elevated temperatures results in an overall increase in toughness as temperature increases. Unusual cases with inclined pre-cracks and microstructural defects did not technically yield valid results, although they were consistent with the nominal cases. Overall, the results indicate that the toughness of single crystal nickel alloys is actually quite high. Thus, the lack of work in this subject is understandable. However, it would seem that any design and lifing work would benefit from an understanding of such a fundamental property.
Author: Eric S. Huron Publisher: John Wiley & Sons ISBN: 1118516400 Category : Technology & Engineering Languages : en Pages : 952
Book Description
A superalloy, or high-performance alloy, is an alloy that exhibits excellent mechanical strength at high temperatures. Superalloy development has been driven primarily by the aerospace and power industries. This compilation of papers from the Twelfth International Symposium on Superalloys, held from September 9-13, 2012, offers the most recent technical information on this class of materials.
Author: Roger C. Reed Publisher: Cambridge University Press ISBN: 1139458639 Category : Technology & Engineering Languages : en Pages : 363
Book Description
Superalloys are unique high-temperature materials used in gas turbine engines, which display excellent resistance to mechanical and chemical degradation. This book introduces the metallurgical principles which have guided their development. Suitable for graduate students and researchers, it includes exercises and additional resources at www.cambridge.org/9780521859042.
Author: Christian Busse Publisher: Linköping University Electronic Press ISBN: 9179299830 Category : Languages : en Pages : 55
Book Description
This dissertation was produced at the Division of Solid Mechanics at Linköping University and is part of a research project, which comprises modelling, microstructure investigations and material testing of cast nickel-base superalloys. The main objective of this work was to deepen the understanding of the fracture behaviour of single-crystal nickel-base superalloys and to develop a model to predict the fatigue crack growth behaviour. Frequently, crack growth in these materials has been observed to follow one of two distinct cracking modes; Mode I like cracking perpendicular to the loading direction or crystallographic crack growth on the octahedral {111}-planes, where the latter is associated with an increased fatigue crack growth rate. Thus, it is of major importance to account for this behaviour in component life prediction. Consequently, a model for the prediction of the transition of cracking modes and the correct active crystallographic plane, i.e. the crack path, and the crystallographic crack growth rate has been developed. This model is based on the evaluation of appropriate crack driving forces using three-dimensional finite-element simulations. A special focus was given towards the influence of the crystallographic orientation on the fracture behaviour. Further, a model to incorporate residual stresses in the crack growth modelling is presented. All modelling work is calibrated and validated by experiments on different specimen geometries with different crystallographic orientations. This dissertation consists of two parts, where Part I gives an introduction and background to the field of research, while Part II consists of six appended papers. Die vorliegende Dissertation wurde in der Abteilung für Festigkeitslehre an der Universität von Linköping erstellt und ist Teil eines Forschungsprojektes, welches Modellierung, Mikrostrukturuntersuchungen und Materialtests von gegossenen nickelbasierten Superlegierungen umfasst. Das Hauptziel dieser Arbeit war es, das Verständnis des Bruchverhaltens von einkristallinen Superlegierungen auf Nickelbasis zu vertiefen und ein Modell zur Vorhersage des Wachstumsverhaltens von Ermüdungsrissen zu entwickeln. Es wurde beobachtet, dass das Risswachstum in diesen Materialien einem von zwei unterschiedlichen Rissmodi folgt; Modus I Rissfortschritt senkrecht zur Belastungsrichtung oder kristallographisches Risswachstum auf den oktaedrischen f111g-Ebenen, wobei letzteres mit einer erhöhten Ermüdungsrisswachstumsrate verbunden ist. Somit ist es von grosser Bedeutung dieses Verhalten in der Lebensdauervorhersage einer Komponente zu berücksichtigen. Demzufolge wurde ein Modell für die Vorhersage des Übergangs zwischen den Rissmodi und der korrekten aktiven kristallographischen Ebene, d.h. des Risspfades, sowie der kristallographischen Risswachstumsrate erarbeitet. Dieses Modell basiert auf geeigneten Rissantriebskräften, welche mit Hilfe dreidimensionaler Finite-Elemente-Simulationen berechnet werden. Im Fokus stand insbesondere der Einuss der kristallographischen Orientierung auf das Bruchverhalten. Ausserdem wird ein Modell zur Berücksichtigung von Restspannungen in der Risswachstumsmodellierung präsentiert. Alle Modellierungsarbeiten wurden durch Experimente an verschiedenen Probengeometrien mit unterschiedlichen kristallographischen Orientierungen kalibriert und validiert. Diese Dissertation besteht aus zwei Teilen, wobei Teil I aus einer Einführung und einem Hintergrund in das Forschungsgebiet und Teil II aus sechs beigefügten Forschungsartikeln besteht.
Author: Christian Busse Publisher: Linköping University Electronic Press ISBN: 9176853950 Category : Languages : en Pages : 26
Book Description
This Licentiate of Engineering thesis is a product of the results generated in the research project KME-702, which comprises modelling, microstructure investigations and material testing of cast nickel-base superalloys. The main objective of this work is to model the fatigue crack propagation behaviour in single-crystal nickel-base superalloys. To achieve this, the influence of the crystal orientations on the cracking behaviour is assessed. The results show that the crystal orientation is strongly affecting the material response and must be accounted for. Furthermore, a linear elastic crack driving force parameter suitable for describing crystallographic cracking has been developed. This parameter is based on resolved anisotropic stress intensity factors and is able to predict the correct crystallographic cracking plane after a transition from a Mode I crack. Finally, a method to account for inelastic deformations in a linear elastic fracture mechanics context was investigated. A residual stress field is extracted from an uncracked finite-element model with a perfectly plastic material model and superimposed on the stress field from the cracked model with a linear elastic material model to account for the inelastic deformations during the determination of the crack driving force. The modelling work is validated by material testing on two different specimen geometries at different temperatures. This Licentiate of Engineering thesis consists of two parts, where Part I gives an introduction and background to the research area, while Part II consists of three papers. Denna licentiatavhandling är en produkt av resultat som genererats i forskningsprojektet KME-702, och omfattar modellering, mikrostrukturundersökningar och materialprovning av gjutna nickelbaserade superlegeringar. Huvudsyftet med detta arbete är att modellera sprickförloppet under utmattning i enkristallina nickelbaserade superlegeringar. För att uppnå detta har kristallorienteringens inverkan på sprickbeteendet utvärderats. Resultaten visar att kristallorienteringen har en stark inverkan på materialbeteendet, således måste hänsyn till denna tas. Dessutom har en linjär-elastisk sprickdrivkraftsparameter lämplig att beskriva kristallografisk sprickbildning utvecklats. Denna parameter är baserad på anisotropa spänningsintensitetsfaktorer på kristallplan och kan prediktera det korrekta kristallografiska sprickplanet efter övergång från Modus I spricka. Slutligen har undersökts en metod för att ta hand om inelastiska deformationer i en linjär-elastisk brottmekanikskontext. Ett restspänningsfält extraherades från en osprucken finita element modell med en ideal plastisk materialmodell. Denna överlagrades på spänningsfältet från den spruckna modellen, som analyserades med en linjär-elastisk materialmodell, för att ta hänsyn till de inelastiska deformationerna vid bestämning av sprickdrivkraften. Modelleringsarbetet validerades genom materialprovning på två olika provgeometrier vid olika temperaturer. Licentiatavhandlingen består av två delar, där del I ger en introduktion och bakgrund till forskningsområdet medan del II består av tre papper. Dieses Lizentiat der Ingenieurwissenschaften ist im Rahmen des Forschungsprojekts KME-702 entstanden, welches Modellierung, Mikrostrukturuntersuchungen und Materialtests von gegossenen nickelbasierten Superlegierungen umfasst. Das Hauptziel dieser Arbeit ist die Modellierung der Ermüdungsrissausbreitung in einkristallinen nickelbasierten Superlegierungen. Um dieses zu erreichen, wurde der Einfluss der Kristallorientierungen auf das Rissverhalten untersucht. Die Ergebnisse zeigen, dass die Kristallorientierung das Materialverhalten stark beeinflusst und daher berücksichtigt werden muss. Darüber hinaus wurde ein linear elastischer Rissantriebskraftparameter entwickelt, der zum Beschreiben von kristallographischen Rissen geeignet ist. Dieser Parameter basiert auf aufgelösten anisotropen Spannungsintensitätsfaktoren und ist in der Lage, die korrekte kristallographische Rissebene nach einem Übergang von einem Modus I Riss vorherzusagen. Abschließend wird in einem linear-elastisch bruchmechanischen Kontext eine Methode untersucht, die nichtelastischen Deformationen bei der Bestimmung der Rissantriebskraft zu berücksichtigen. Dazu wird aus einem Finite-Elemente Modell, welches keinen Riss aufweist und mit einem perfekt plastischen Materialmodell beschrieben wird, das Restspannungsfeld extrahiert und dem Spannungsfeld überlagert, welches aus dem Modell mit Riss unter Verwendung eines linear elastischen Materialmodells erzeugt wurde. Die Modellierung wird durch Materialtests an zwei verschiedenen Probengeometrien bei unterschiedlichen Temperaturen validiert. Dieses Lizentiat der Ingenieurwissenschaften besteht aus zwei Teilen, wobei Teil I eine Einführung und einen Hintergrund in das Forschungsgebiet gibt, während Teil II aus drei Forschungsartikeln besteht.
Author: Sammy Tin Publisher: Springer Nature ISBN: 3030518345 Category : Technology & Engineering Languages : en Pages : 1098
Book Description
The 14th International Symposium on Superalloys (Superalloys 2020) highlights technologies for lifecycle improvement of superalloys. In addition to the traditional focus areas of alloy development, processing, mechanical behavior, coatings, and environmental effects, this volume includes contributions from academia, supply chain, and product-user members of the superalloy community that highlight technologies that contribute to improving manufacturability, affordability, life prediction, and performance of superalloys.
Author: B.L. Karihaloo Publisher: Elsevier ISBN: 008098374X Category : Technology & Engineering Languages : en Pages : 661
Book Description
Fracture is a major cause of failure in metallic and non-metallic materials and structures. An understanding of the micro- and macro- mechanisms of fracture enables materials scientists to develop materials with high fracture resistance, which in turn helps engineers and designers to ensure the soundness and integrity of structures made from these materials. The International Congress on Fracture is held every four years and is an occasion to take stock of the major achievements in the broad field of fracture, to honour those who have made lasting contributions to this field, and to reflect on the future directions. ICF9 is published in six volumes covering the areas of:-- Failure Analysis, Remaining Life Assessment, Life Extension and Repair- Failure of Multiphase and Non-Metallic Materials- Fatigue of Metallic and Non-Metallic Materials and Structures- Theoretical and Computational Fracture Mechanics and New Directions- Testing and Characterization Methods, and Interfacial Fracture Mechanics- High Strain Rate Fracture and Impact Mechanics.
Author: W. Steven Johnson
Author: W. Steven Johnson
Author: Steven R. Daniewicz
Author: Eric S. Huron
Author: Roger C. Reed
Author: Christian Busse
Author: Christian Busse
Author: 
Author: 
Author: Sammy Tin
Author: B.L. Karihaloo