Download or read book Near Threshold Crack Growth in Nickel Base Superalloys written by HR. Van Stone and published by . This book was released on 1988 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: The influence of stress ratio on the elevated-temperature crack growth behavior of the nickel-base superalloys René 95 and Alloy 718 is discussed. The near-threshold and Region II crack growth behavior of a wide variety of microstructures for each alloy are explained using phenomenological descriptions of closure, that is, K-dependent or K-independent closure. K-dependent closure is the type of closure observed for nickel-base superalloys where increasing the R-ratio causes a uniform lateral shift of the entire fatigue crack growth curve. K-independent closure is the type commonly reported for steels and titanium alloys where increasing the R-ratio has a larger influence on near-threshold crack growth than on Region II crack growth. The existence of K-dependent closure in nickel-base superalloys results in microstructurally sensitive crack growth rates, even at high R-ratios. This permits the use of K-based crack growth prediction techniques and simplifies alloy and process development for applications having complex loading spectra.

Download or read book The Near Threshold Fatigue Crack Growth Behavior of a Nickel based Superalloy written by George John Gikas and published by . This book was released on 1982 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Near Threshold Corrosion Fatigue Crack Growth Behavior of a Nickel Base Superalloy in Air and Inert Environments written by James Lum Yuen and published by . This book was released on 1982 with total page 412 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Near Threshold Fatigue Crack Growth Behavior of Fine Grain Nickel Based Alloys written by John A. Newman and published by . This book was released on 2003 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Near Threshold Crack Growth Behavior of a Single Crystal Ni Base Superalloy Subjected to Mixed Mode Loading written by D. DeLuca and published by . This book was released on 1999 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ni-base single crystal superalloys, which are used in applications such as gas turbine engine blades, are primarily loaded along the (001) direction. Mode II (crystallographic shear) type cracking along the (111) plane is frequently the mode of growth in the early stages of fatigue failure of these components. Disks with a middle crack were used to characterize crystallographic shear crack growth from machined flaws oriented parallel to a (111) plane of a single crystal alloy. Automated crack growth experiments were conducted at constant stress ratio in the near threshold regime. Various combinations of Mode I and Mode II loading were achieved by orienting the machined flaw at different angles (?) to the loading axis. Loading angle ? = 0° (pure Mode I loading) resulted in crystallographic crack extension along alternating (111) slip systems producing a zig-zag pattern. This orientation exhibited significant resistance to self-similar crack growth from the machined flaw. In contrast, self-similar crack growth was achieved with relative ease for loading angles, ? ?0° (mixed mode). In the mixed mode tests with KI > 0, the crack growth rate was 10 to 50 times higher than that under Mode I loading. Preliminary results indicate that crack growth is non-crystallographic at 593°C.

Download or read book Threshold Crack Growth Behavior of Nickel Base Superalloy at Elevated Temperature written by NE. Ashbaugh and published by . This book was released on 1989 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental program was conducted to evaluate the effects of frequency and R on the near-threshold crack growth behavior of Inconel 718 at 649°C in laboratory air. Frequencies from 0.01 to 400 Hz and R from 0.1 to 0.9 were applied to compact tension [C(T)] and middle- or center-cracked tension [M(T)] specimens under decreasing-K conditions using computer-controlled test machines. Digital load-displacement data were obtained to determine crack length and closure load. The fatigue crack growth threshold in Inconel 718 at 649°C obtained using decreasing ?K testing was generally associated with a crack arrest phenomenon which could be attributed to the buildup of oxides with time. Over the ranges of R and v used in this investigation, the growth rate behavior at the onset of crack arrest appears to be a combination of time-dependent and cyclic-dependent behavior. Even at 400 Hz, purely cyclic behavior was apparently never reached. For crack growth rate modeling, both frequency and stress ratio have to be incorporated in the characterization of ?Kth. Over the ranges of parameters tested, a cyclic threshold was approached at high frequencies and low R and a sustained load time-dependent threshold was obtained at high R, indicating that the cyclic contribution to the growth rate was negligible.

Download or read book The Fatigue Crack Propagation Behavior of a Polycrystalline Nickel base Superalloy in the Near Threshold Region written by Santo A. Padula (II.) and published by . This book was released on 2002 with total page 404 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Modelling of Crack Growth in Single Crystal Nickel Base Superalloys written by Christian Busse and published by Linköping University Electronic Press. This book was released on 2019-09-24 with total page 55 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Aspects of Crack Growth in Single Crystal Nickel Base Superalloys written by Christian Busse and published by Linköping University Electronic Press. This book was released on 2017-11-20 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Fracture Mechanics Nineteenth Symposium written by Thomas A. Cruse and published by ASTM International. This book was released on 1988 with total page 936 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Cracks in superalloys written by Jonas Saarimäki and published by Linköping University Electronic Press. This book was released on 2018-01-18 with total page 63 pages. Available in PDF, EPUB and Kindle. Book excerpt: Gas turbines are widely used in industry for power generation and as a power source at hard to reach locations where other possibilities for electrical power supplies are insufficient. New ways of producing greener energy is needed to reduce emission levels. This can be achieved by increasing the combustion temperature of gas turbines. High combustion temperatures can be detrimental and degrade critical components. This raises the demands on the high temperature performance of the superalloys used in gas turbine components. These components are frequently subjected to different cyclic loads combined with for example dwell-times and overloads at elevated temperatures, which can influence the crack growth. Dwell-times have been shown to accelerate crack growth and change cracking behaviour in both Inconel 718, Haynes 282 and Hastelloy X. On the other hand, overloads at the beginning of a dwell-time cycle have been shown to retard the dwell-time effect on crack growth in Inconel 718. More experiments and microstructural investigations are needed to better understand these effects. The work presented in this thesis was conducted under the umbrella of the research program Turbo Power; "High temperature fatigue crack propagation in nickel-based superalloys", where I have mainly looked at fatigue crack growth mechanisms in superalloys subjected to dwell-fatigue, which can have a devastating effect on crack propagation behaviour. Mechanical testing was performed under operation-like cycles in order to achieve representative microstructures and material data for the subsequent microstructural work. Microstructures were investigated using light optical microscopy and scanning electron microscopy (SEM) techniques such as electron channeling contrast imaging (ECCI) and electron backscatter diffraction (EBSD). The outcome of this work has shown that there is a significant increase in crack growth rate when dwell-times are introduced at maximum load (0 % overload) in the fatigue cycle. With the introduction of a dwell-time there is also a shift from transgranular to intergranular crack growth for both Inconel 718 and Haynes 282. The crack growth rate decreases with increasing overload levels in Inconel 718 when an overload is applied prior to the dwell-time. At high temperature, intergranular crack growth was observed in Inconel 718 as a result of oxidation and the creation of nanometric voids. Another observed growth mechanism was crack advance along ?-phase boundaries with subsequent oxidation of the ?-phase. This thesis comprises two parts. Part I gives an introduction to the field of superalloys and the acting microstructural mechanisms related to fatigue and crack propagation. Part II consists of five appended papers, which report the work completed as part of the project.

Download or read book Superalloys written by Matthew J. Donachie and published by ASM International. This book was released on 2002 with total page 439 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book covers virtually all technical aspects related to the selection, processing, use, and analysis of superalloys. The text of this new second edition has been completely revised and expanded with many new figures and tables added. In developing this new edition, the focus has been on providing comprehensive and practical coverage of superalloys technology. Some highlights include the most complete and up-to-date presentation available on alloy melting. Coverage of alloy selection provides many tips and guidelines that the reader can use in identifying an appropriate alloy for a specific application. The relation of properties and microstructure is covered in more detail than in previous books.

Download or read book Fatigue Crack Initiation and the Growth of Short Cracks in Nickel based Superalloys written by James Finis McCarver and published by . This book was released on 1981 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fatigue Crack Propagation of Nickel Base Superalloys at 650 C written by TP. Gabb and published by . This book was released on 1988 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: The 650°C fatigue crack propagation behavior of two nickel-base superalloys, René 95 and Waspaloy, were studied with particular emphasis placed on understanding the roles of creep, environment, and two key grain boundary alloying additions, boron and zirconium. Comparison of air and vacuum data showed the air environment to be detrimental over a wide range of frequencies for both alloys. In-depth analysis of René 95 showed that at lower frequencies, such as 0.02 Hz, failure in air occurred by intergranular, environmentally assisted creep crack growth, while at higher frequencies, up to 5.0 Hz, environmental interactions were still evident but creep effects were minimized. The effect of boron and zirconium in Waspaloy was found to be important where environmental and/or creep interactions were present. In those instances, removal of boron and zirconium dramatically increased crack growth. It is therefore plausible that effective dilution of these elements may explain, in part, a previously observed trend in which crack growth rates increased with decreasing grain size.

Download or read book Fatigue of Materials written by Subra Suresh and published by Cambridge University Press. This book was released on 1998-10-29 with total page 708 pages. Available in PDF, EPUB and Kindle. Book excerpt: Written by a leading researcher in the field, this revised and updated second edition of a highly successful book provides an authoritative, comprehensive and unified treatment of the mechanics and micromechanisms of fatigue in metals, non-metals and composites. The author discusses the principles of cyclic deformation, crack initiation and crack growth by fatigue, covering both microscopic and continuum aspects. The book begins with discussions of cyclic deformation and fatigue crack initiation in monocrystalline and polycrystalline ductile alloys as well as in brittle and semi-/non-crystalline solids. Total life and damage-tolerant approaches are then introduced in metals, non-metals and composites followed by more advanced topics. The book includes an extensive bibliography and a problem set for each chapter, together with worked-out example problems and case studies. This will be an important reference for anyone studying fracture and fatigue in materials science and engineering, mechanical, civil, nuclear and aerospace engineering, and biomechanics.

Download or read book Fatigue Crack Growth Threshold Concepts written by David L. Davidson and published by Society for Mining Metallurgy & Exploration. This book was released on 1984 with total page 584 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book An Investigation Into the Near threshold Crack Growth Behaviour and Metallurgy of Inertia Friction Welded Nickel based Superalloy RR1000 written by Mabutho Viki and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: