High Temperature Crack Propagation in Inconel 718 PDF Download
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Author: Henrik Andersson
Publisher:
ISBN:
Category :
Languages : en
Pages : 71
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Author: Henrik Andersson
Publisher:
ISBN:
Category :
Languages : en
Pages : 71
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Book Description
Author:
Publisher:
ISBN: 9789175197500
Category :
Languages : en
Pages : 135
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Book Description
The overall objective of this work has been to develop and evaluate tools for designing against fatigue in gas turbine applications, with special focus on the nickel-based superalloy Inconel 718.
Author: Jonas Saarimäki
Publisher: Linköping University Electronic Press
ISBN: 9176858715
Category :
Languages : en
Pages : 49
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Book Description
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 supply are insufficient. There is a strong need for greener energy, considering the effect that pollution has had on global warming, and we need to come up with ways of producing cleaner electricity. A way to achieve this is by increasing the combustion temperature in gas turbines. This increases the demand on the high temperature performance of the materials used e.g. superalloys in the turbine. These high combustion temperatures can lead to detrimental degradation of critical components. These components are commonly subjected to cyclic loading of different types e.g. combined with dwell-times and overloads at elevated temperatures, which influence the crack growth. Dwell-times have shown to accelerate crack growth and change the cracking behaviour in both Inconel 718 and Haynes 282. Overloads at the beginning of the dwell-time cycle have shown to retard the dwell time effect on crack growth in Inconel 718. To understand these effects more microstructural investigations are needed. The work presented in this licentiate thesis was conducted under the umbrella of the research program Turbo Power; "High temperature fatigue crack propagation in nickel-based superalloys", concentrating on fatigue crack growth mechanisms in superalloys during dwell-times, which have shown to have a devastating effect on the crack propagation behaviour. Mechanical testing was performed under operation-like conditions in order to achieve representative microstructures and material data for the subsequent microstructural work. The microstructures were microscopically investigated in a scanning electron microscope (SEM) using electron channeling contrast imaging (ECCI) as well as using light optical microscopy. The outcome of this work has shown that there is a significant increase in crack growth rate when dwell-times are introduced at the 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. When an overload is applied prior to the dwell-time, the crack growth rate decreases with increasing overload levels in Inconel 718. At high temperature crack growth in Inconel 718 took place as intergranular crack growth along grain boundaries due to oxidation and the creation of nanometric voids. Another observed growth mechanism was crack advance along phase boundaries with subsequent severe oxidation of the phase. This thesis comprises two parts. The first giving an introduction to the field of superalloys and the acting microstructural mechanisms that influence fatigue during dwell times. The second part consists of two appended papers, which report the work completed so far in the project.
Author: Jonas Saarimäki
Publisher: Linköping University Electronic Press
ISBN: 9176853853
Category :
Languages : en
Pages : 63
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Book Description
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.
Author: Tusit Weerasooriya
Publisher:
ISBN:
Category : Inconel
Languages : en
Pages : 0
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Author: Tusit Weerasooriya
Publisher:
ISBN:
Category : Inconel
Languages : en
Pages : 36
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Book Description
Fatigue crack growth was studied at 650 deg. C as a function of frequency for several ratios of minimum-to-maximum stress intensity, and for two values of maximum stress intensity factor. Crack lengths were monitored at low frequencies from compliance calculations based on crack mouth opening displacement measurements. At higher frequencies, crack length was measured using a d.c. electric potential system. It was found that fatigue crack growth rate can be characterized in three distinct frequency regions. These three regions represent fully cycle dependent, mixed, and fully time dependent crack growth behavior and each region can be modeled by a power law function. Observation of micro mechanisms support the existence of these three different regions of crack growth. Keywords: Fatigue crack growth, Time dependent growth, Cyclic-dependent growth, Nickel base superalloy, Crack growth rate model, Frequency effects.
Author: Diego Martinez De Luca
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Fatigue crack growth was studied at 650 deg. C as a function of frequency for several ratios of minimum-to-maximum stress intensity, and for two values of maximum stress intensity factor. Crack lengths were monitored at low frequencies from compliance calculations based on crack mouth opening displacement measurements. At higher frequencies, crack length was measured using a d.c. electric potential system. It was found that fatigue crack growth rate can be characterized in three distinct frequency regions. These three regions represent fully cycle dependent, mixed, and fully time dependent crack growth behavior and each region can be modeled by a power law function. Observation of micro mechanisms support the existence of these three different regions of crack growth. Keywords: Fatigue crack growth, Time dependent growth, Cyclic-dependent growth, Nickel base superalloy, Crack growth rate model, Frequency effects.
Author: Robert Garth Andrews
Publisher:
ISBN:
Category :
Languages : en
Pages : 392
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Book Description
Author: Ulrich Krupp
Publisher: John Wiley & Sons
ISBN: 3527610677
Category : Technology & Engineering
Languages : en
Pages : 311
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Book Description
This comprehensive overview of the whole field of fatigue and fracture of metallic materials covers both the theoretical background and some of the latest experimental techniques. It provides a summary of the complex interactions between material microstructure and cracks, classifying them with respect to the overall damage process with a focus on microstructurally short cracks and dynamic embrittlement. It furthermore introduces new concepts for the numerical treatment of fatigue microcrack propagation and their implementation in fatigue-life prediction models.This comprehensive overview of the whole field of fatigue and fracture of metallic materials covers both the theoretical background and the latest experimental techniques. It provides a summary of the complex interactions between material microstructure and cracks, classifying them with respect to the overall damage process. It furthermore introduces new concepts for the numerical treatment of fatigue microcrack propagation and their implementation in fatigue-life prediction models.
