Thermomechanical Fatigue Crack Formation In Nickel Base Superalloys At Notches
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Thermomechanical Fatigue Crack Formation In Nickel Base Superalloys At Notches
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Author : Patxi Fernandez-Zelaia
language : en
Publisher:
Release Date : 2012
Thermomechanical Fatigue Crack Formation In Nickel Base Superalloys At Notches written by Patxi Fernandez-Zelaia and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with Alloys categories.
Hot sections of gas engine turbines require specialized materials to withstand extreme conditions present during engine operation. Nickel-base superalloys are typically used as blades and disks in the high pressure turbine section because they possess excellent fatigue strength, creep strength and corrosion resistance at elevated temperatures. Components undergo thermomechanical fatigue conditions as a result of transient engine operation. Sharp geometric features, such as cooling holes in blades or fir-tree connections in disks, act as local stress raisers. The material surrounding these features are potential sites of localized inelastic deformation and crack formation. To reduce customer costs associated with unnecessary overhauls or engine down-time, gas turbine manufacturers require accurate prediction methods to determine component endurances. The influence of stress concentration severity on thermomechanical fatigue crack formation is of particular importance as cracks often initiate in these hot spots. Circumferentially notched specimens were utilized to perform thermomechanical fatigue experiments on blade material CM247LC DS and disk material PM IN100. A parametric study on CM247LC DS was performed utilizing four notched specimens. Experimental results were coupled with finite element simulations utilizing continuum based constitutive models. The effects of applied boundary conditions on crack initiation life was studied in both alloys by performing experiments under remotely applied force and displacement boundary conditions. Finite element results were utilized to develop a life prediction method for notched components under thermomechanical fatigue conditions.
Thermomechanical Fatigue Crack Propagation In An Anisotropic Directionally Solidified Nickel Base Superalloy
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Author : AE. Gemma
language : en
Publisher:
Release Date : 1976
Thermomechanical Fatigue Crack Propagation In An Anisotropic Directionally Solidified Nickel Base Superalloy written by AE. Gemma and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1976 with Crack propagation categories.
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.
Thermal Mechanical Fatigue Crack Propagation In Nickel And Cobalt Base Superalloys Under Various Strain Temperature Cycles
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Author : AE. Gemma
language : en
Publisher:
Release Date : 1973
Thermal Mechanical Fatigue Crack Propagation In Nickel And Cobalt Base Superalloys Under Various Strain Temperature Cycles written by AE. Gemma and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1973 with Coatings categories.
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.
Thermal Mechanical Fatigue Behavior Of Nickel Base Superalloys
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Author : Norman J. Marchand
language : en
Publisher:
Release Date : 19??
Thermal Mechanical Fatigue Behavior Of Nickel Base Superalloys written by Norman J. Marchand and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 19?? with categories.
This report presents the main achievements of a 36-month research program the main objective of which was to gain more insight into the problem of crack growth under thermal mechanical fatigue (TMF) conditions. The program was arranged into five technical tasks. Under Task I, the goal was to identify the crack propagation conditions in aircraft engines (hot section) and to assess the validity of conventional fracture mechanics parameters to address TMF crack growth. The second task defined the test facilities, test specimen and the testing conditions needed to establish the effectiveness of data correlation parameters identified in Task I. Under Task III, a computerized testing system to measure the TMF behavior (LCF and CG behaviors) of various alloy systems was built. A crack propagation test program was defined and conducted under Task IV. The test variables included strain range, strain rate (frequency) and temperature. Task V correlated and generalized the Task IV data for isothermal and variable temperature conditions so that several crack propagation parameters could be compared and evaluated.
Thermomechanical Fatigue Behaviour Of Coated And Bare Nickel Based Superalloy Single Crystals
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Author : E. Chataigner
language : en
Publisher:
Release Date : 1996
Thermomechanical Fatigue Behaviour Of Coated And Bare Nickel Based Superalloy Single Crystals written by E. Chataigner and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1996 with Alloys categories.
The thermal-mechanical fatigue behaviour of chromium-aluminium coated [001] single crystals of AM1, a nickel-base superalloy for turbine blades, is studied using a "diamond" shape cycle from 600‡ to 1100‡C. Comparison with bare specimens does not show any significant difference in thermal-mechanical fatigue nor in isothermal low cycle fatigue at high temperature. Metallographic observations on fracture surfaces and longitudinal sections of specimens tested to fatigue life or to a definite fraction of expected life have shown that the major crack tends to initiate from casting micropores in the sub-surface area very early in bare and coated specimens, under low cycle fatigue or thermal-mechanical fatigue. But the interaction between oxidation and fatigue cracking seems to play a major role. A simple model proposed by Reuchet and Rémy has been identified for this single crystal superalloy. Its application to the life prediction under low cycle fatigue and thermal-mechanical fatigue for bare and coated single crystals with different orientations is shown.
Influence Of Control Mode On Thermomechanical Fatigue Testing Of Circumferentially Notched Specimens
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Author : P. Fernandez-Zelaia
language : en
Publisher:
Release Date : 2014
Influence Of Control Mode On Thermomechanical Fatigue Testing Of Circumferentially Notched Specimens written by P. Fernandez-Zelaia and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with Boundary conditions categories.
The aim of this study is to understand the influence of experimentally applied boundary conditions on circumferentially-notched specimens under thermomechanical fatigue loadings (TMF) in two Ni-base superalloys, one equiaxed polycrystalline, and one directionally-solidified. TMF experiments were performed under both force-controlled and displacement-controlled conditions. Notch severities ranged from kt = 1.3 to kt = 2. The notch response was evaluated by finite element analysis using temperature-dependent viscoplasticity. The experiments and analyses are used to assess the impact of the applied boundary conditions on calculated and observed fatigue crack initiation lives.
Towards The Development Of A Physics Based Thermo Mechanical Fatigue Life Prediction Model For A Single Crystalline Ni Base Superalloy
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Author : Robert Amaro
language : en
Publisher:
Release Date : 2014
Towards The Development Of A Physics Based Thermo Mechanical Fatigue Life Prediction Model For A Single Crystalline Ni Base Superalloy written by Robert Amaro and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with Individual differences in infants categories.
A long term effort has been underway to develop a mechanism-based model for life prediction under thermo-mechanical fatigue (TMF) cycling. A model has been developed which is based upon the impingement of slip bands upon oxidized regions and subsequent initiation of a crack due to stress concentration. The concept of an effective cycle temperature, Teff, and the dynamic nature of the material are critical components of the model and result in the ability to produce very accurate life predictions. It has also been shown that the model is capable of addressing complexities such as imposed high cycle fatigue (HCF) while still producing excellent agreement with the experiment. However, given the fact that this material is used for jet engine turbine blades and that such blades have cooling holes which act as notches, the next step in the development of this model is to incorporate it into a notched environment. The principal features of the TMF model are reviewed and a strategy for full integration into notched fatigue life prediction is discussed. Recent experimental results are presented which are based upon simulating smooth bar conditions at the notch root and a first approach to numerical simulation (called Q fit) is presented. Suggestions for further research are discussed.
Thermomechanical Fatigue Behavior Of Materials
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Author : Michael J. Verrilli
language : en
Publisher: ASTM International
Release Date : 1996
Thermomechanical Fatigue Behavior Of Materials written by Michael J. Verrilli and has been published by ASTM International this book supported file pdf, txt, epub, kindle and other format this book has been release on 1996 with categories.
Superalloys 2012
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Author : Eric S. Huron
language : en
Publisher: John Wiley & Sons
Release Date : 2012-10-02
Superalloys 2012 written by Eric S. Huron and has been published by John Wiley & Sons this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-10-02 with Technology & Engineering categories.
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.
Fatigue Crack Propagation Of Nickel Base Superalloys At 650c
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Author : John Gayda
language : en
Publisher:
Release Date : 1985
Fatigue Crack Propagation Of Nickel Base Superalloys At 650c written by John Gayda and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1985 with Heat resistant alloys categories.