Download or read book Scatter in Fatigue Crack Growth Rate in a Directionally Solidified Nickel Base Superalloy written by S. Highsmith and published by . This book was released on 2004 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: Directional solidification of nickel-base superalloy components for gas turbine rotor blades offers a significant improvement in creep strength while at the same time yielding an anisotropic, heterogeneous microstructure. In such a material, some of the continuum assumptions of linear elastic fracture mechanics begin to break down, and local (microscopic) conditions can lead to significant deviation in fatigue crack growth rate from the global (macroscopic) trend. Fatigue crack life prediction for a large population of fielded components requires a probabilistic treatment of the material fatigue crack growth behavior. A common approach to probabilistic fatigue crack life prediction involves sampling the Paris law coefficients from a large number of crack growth experiments, which can lead to effectively "smoothing" the local intraspecimen variability out of the model. The length scale of variability is discussed as it relates to material microstructure and crack life prediction. Results from fatigue crack growth experiments on a directionally solidified superalloy are presented and spatial variation in the fatigue crack growth rate is examined. Periodicity of the crack growth rate variation is compared with the scale of microstructural heterogeneity.
Download or read book Thermomechanical Fatigue Crack Propagation in an Anisotropic Directionally Solidified Nickel Base Superalloy written by AE. Gemma and published by . This book was released on 1976 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: Strain-controlled thermomechanical fatigue tests were performed on two nickel-base superalloys, directionally solidified (DS) Mar-M200 plus hafnium and conventionally cast B-1900 plus hafnium. The DS alloy was tested at various angles (?) to the direction of grain growth. It was found that crack growth rates were a minimum for the DS alloy tested parallel to the direction of grain growth (crack propagating normal to the direction of grain growth). The crack growth rate increased for other orientations in the sequence ? = 15, 30 or 90, and 45 deg until equivalence was reached with rates for the conventionally cast alloy, B-1900 plus hafnium. A linear elastic fracture mechanics approach was extended to strain-controlled crack growth as a function of ? for the DS alloy. Prediction of crack growth rates as a function of ? was achieved by normalizing with the elastic modulus. The sequencing of crack growth rates with ? and a smooth-to-rough fracture surface transition are explained on the basis of the orientation dependence of crack opening displacement for a given strain intensity range.
Download or read book Probabilistic Aspects of Life Prediction written by W. Steven Johnson and published by ASTM International. This book was released on 2004 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt: As fatigue and fracture mechanics approaches are used more often for determining the useful life and/or inspection intervals for complex structures, realization sets-in that all factors are not well known or characterized. Indeed, inherent scatter exists in initial material quality and in material performance. Furthermore, projections of component usage in determination of applied stresses are inexact at best and are subject to much discrepancy between projected and actual usage. Even the models for predicting life contain inherent sources of error based on assumptions and/or empirically fitted parameters. All of these factors need to be accounted for to determine a distribution of potential lives based on combination of the aforementioned variables, as well as other factors. The purpose of this symposium was to create a forum for assessment of the state-of-the-art in incorporating these uncertainties and inherent scatter into systematic probabilistic methods for conducting life assessment.
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 Probabilistic Aspects of Life Prediction written by and published by ASTM International. This book was released on with total page 279 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Thermal Mechanical Fatigue Crack Propagation in Nickel and Cobalt Base Superalloys Under Various Strain Temperature Cycles written by AE. Gemma and published by . This book was released on 1973 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: Crack propagation rates under isothermal and thermal fatigue cycling have been determined for a conventionally-cast cobalt-base superalloy, and conventionally-cast and directionally-solidified nickel-base superalloys. Linear elastic fracture mechanics, where the crack growth rates under different strain ranges or for various crack lengths depend only on the strain intensity factor range, was found to be applicable over the range of crack growth rates of most practical importance. A comparison of crack growth rates is made for thermal fatigue under various strain-temperature cycles and isothermal low-cycle fatigue, and the influence of coatings and superimposed creep is discussed.
Download or read book The Microstructural Dependence of Fatigue Crack Growth Rates in a Nickel base Superalloy written by Erik Arthur Schwarzkopf and published by . This book was released on 1989 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fatigue Crack Growth and Low Cycle Fatigue of Two Nickel Base Superalloys written by N. S. Stoloff and published by . This book was released on 1983 with total page 49 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Fracture Morphology of Nickel base Superalloys Tested in Fatigue and Creep fatigue at 650 C written by and published by . This book was released on 1981 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 An Investigation Into the Fatigue Crack Growth Characteristics of a Single Crystal Nickel base Superalloy written by David Chong.* Wu and published by . This book was released on 1986 with total page 338 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Effects of Loading Waveform on Fatigue Crack Growth at Elevated Temperature in Nickel Base Superalloys written by S. Dalby and published by . This book was released on 1999 with total page 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 Short Fatigue Crack Growth in a Nickel base Superalloy at Room and Elevated Temperature written by J. C. Healy and published by . This book was released on 1990 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Effect of Loading Waveform on Fatigue Crack Growth at Elevated Temperature in Nickel Base Superalloys written by S. Dalby and published by . This book was released on 1999 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Elevated Temperature Fatigue Crack Growth in a Nickel Base Superalloy Under Dwell Conditions written by J. Byrne and published by . This book was released on 1991 with total page 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: