Near Threshold Corrosion Fatigue Crack Growth Behavior of a Nickel Base Superalloy in Air and Inert Environments PDF Download
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Author: James Lum Yuen
Publisher:
ISBN:
Category : Iron-nickel alloys
Languages : en
Pages : 412
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Book Description
Author: James Lum Yuen
Publisher:
ISBN:
Category : Iron-nickel alloys
Languages : en
Pages : 412
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Book Description
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 724
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Book Description
Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Author: George John Gikas
Publisher:
ISBN:
Category : Alloys
Languages : en
Pages : 136
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Book Description
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781721587025
Category :
Languages : en
Pages : 28
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Book Description
Constant-Kmax fatigue crack growth tests were performed on two finegrain nickel-base alloys Inconel 718 (DA) and Ren 95 to determine if these alloys exhibit near-threshold time-dependent crack growth behavior observed for fine-grain aluminum alloys in room-temperature laboratory air. Test results showed that increases in K(sub max) values resulted in increased crack growth rates, but no evidence of time-dependent crack growth was observed for either nickel-base alloy at room temperature. Newman, John A. and Piascik, Robert S. Langley Research Center NASA/TM-2003-212443, NAS 1.15:212443, L-18314, ARL-TR-3021
Author: NE. Ashbaugh
Publisher:
ISBN:
Category : Crack arrest
Languages : en
Pages : 11
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Book Description
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.
Author:
Publisher:
ISBN:
Category : Corrosion and anti-corrosives
Languages : en
Pages : 668
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Book Description
Author:
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 534
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Book Description
Author: Santo A. Padula (II.)
Publisher:
ISBN:
Category :
Languages : en
Pages : 404
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Book Description
Author: HR. Van Stone
Publisher:
ISBN:
Category : Crack closure
Languages : en
Pages : 24
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Book Description
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.
Author: Raghu Prakash
Publisher:
ISBN:
Category : Corrosive wastes
Languages : en
Pages : 16
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Book Description
Nickel based super-alloys when exposed to a combination of high temperature and low melting point fused corrosion products, result in early fatigue failure compared to their response in high temperature benign environment. The high cycle fatigue (HCF) (at 550 and 625°C) as well as fatigue crack growth (at 550°C) behavior of a nickel based super alloy 718 in hot corrosive environment (Na2SO4+NaCl salt coating), typical of marine engine environment, is presented in this paper. At least an order of magnitude decrease in fatigue life is noticed when the temperature is changed from 550 to 625°C at stress levels below 450 MPa. The statistical analysis of scatter in fatigue lives at different stress levels is performed and a Weibull-Inverse power law model is fitted to the stress-fatigue life data of alloy 718 in hot corrosive environment. Fracture surface examination of hot corrosion fatigue failures showed higher crack growth rates compared to uncoated high temperature HCF fracture surfaces. Fatigue crack growth rate at 550°C in a hot corrosive environment increases by an order of magnitude at 0.5 Hz in the Paris region compared to crack growth kinetics at 2 Hz in lab air environment at the same temperature. The fracture surface shows a mix of transgranular and intergranular mode of crack in the propagation region at 0.5 Hz. A fatigue failure diagram is proposed combining the thresholds of maximum stress level from endurance tests and maximum stress intensity factor from fatigue crack growth tests to demarcate the regions of propagating and non-propagating cracks during hot corrosion fatigue. The complexities in incorporating the effect of loading frequency in fatigue failure diagram are highlighted.
