Download or read book Microstructural Effects and Fatigue Life Predictions of Notched and Un notched Ni Base Superalloys at Elevated Temperatures written by Stephen D. Antolovich and published by . This book was released on 1980 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt: The LCF(Low Cycle Fatigue) behavior of Ni base superalloys was studied both for smooth and notched test bars. The primary research material was Rene 80 which finds application in turbine blades used in the temperature range of 650-982 C (1200-1800 F). The smooth bar LCF behavior was studied in the as-heat treated condition and also after exposure for 100h at 982 C, either under a stress of 97 MPa (14 ksi) or OMPa. Test conditions included continuous cycling at different strain rates as well as 90 second hold periods at either maximum or minimum strain. The primary test temperatures were 871 C (1600 F) and 982 C (1800 F). It was found that prior exposure greatly reduces the fatigue life. Since these experiments tend to duplicate actual engine conditions, use of data obtained using as-heat treated specimens may be very non-conservative to predict lives of actual components. The test results correlated very well with a model for LCF which is based on the concept that cracks initiate at a critical combination of oxide depth and stress. The notch LCF problem was also studied. A computer model for calculating local stresses and strains was developed. In addition to the Rene 80 studies, some initial smooth bar LCF studies were carried out using Rene 77.
Download or read book Microstructural Effects and Fatigue Life Predictions of Notched and Un notched Nickel Base Superalloys at Elevated Temperatures written by Stephen D. Antolovich and published by . This book was released on 1978 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: The low cycle fatigue (LCF) of Rene 80 has been investigated at 1400, 1600 and 1800 F. Emphasis has been placed on the 1800 F studies using smooth bar (continuous cycling and 90 sec hold time) and notch LCF specimens. The detailed transmission electron microscopy shows that at 1600 and 1800 F the dislocation debris is independent of test rate over two orders of magnitude. The test results can not be explained in terms of the conventional approaches to high temperature LCF for which damage is assumed to result from creep/fatigue interactions. Instead, it is suggested that the important damage mechanism is an interaction between the deformation mode and the environment. Based on that understanding a model is developed for crack propagation at elevated temperatures and a similar model is being developed for crack initiation. (Author).
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1978 with total page 1018 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1980 with total page 870 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Technical Abstract Bulletin written by and published by . This book was released on with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fatigue Life written by V. S. Goel and published by . This book was released on 1986 with total page 440 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Aerospace Structural Metals Handbook written by and published by . This book was released on 1989 with total page 828 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Metals Abstracts written by and published by . This book was released on 1995 with total page 1602 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Aerospace Structural Metals Handbook written by Belfour Stulen, Inc. Mechanical Properties Data Center and published by . This book was released on 1970 with total page 860 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book CAB Current Awareness Bulletin written by and published by . This book was released on 1981 with total page 456 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Metals Abstracts Index written by and published by . This book was released on 1981 with total page 706 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Constitutive Modeling and Life Prediction in Ni base Superalloys written by Mahesh M. Shenoy and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Microstructural features at different scales affect the constitutive stress-strain response and the fatigue crack initiation life in Ni-base superalloys. While numerous efforts have been made in the past to experimentally characterize the effects of these features on the stress-strain response and/or the crack initiation life, there is a significant variability in the data with sometimes contradictory conclusions, in addition to the substantial costs involved in experimental testing. Computational techniques can be useful tools to better understand these effects since they are relatively inexpensive and are not restricted by the limitations in processing techniques. The effect of microstructure on the stress-strain response and the variability in fatigue life were analyzed using two Ni-base superalloys; DS GTD111 which is a directionally solidified Ni-base superalloy, and IN100 which is a polycrystalline Ni-base superalloy. Physically-based constitutive models were formulated and implemented as user material subroutines in ABAQUS using the single crystal plasticity framework which can predict the material stress-strain response with the microstructure-dependence embedded into them. The model parameters were calibrated using experimental cyclic stress-strain histories. A computational exercise was employed to quantify the influence of idealized microstructural variables on the fatigue crack initiation life. Understanding was sought regarding the most significant microstructure features using explicit modeling of the microstructure with the aim to predict the variability in fatigue crack initiation life and to guide material design for fatigue resistant microstructures. Lastly, it is noted that crystal plasticity models are often too computationally intensive if the objective is to model the macroscopic behavior of a textured or randomly oriented 3-D polycrystal in an engineering component. Homogenized constitutive models were formulated and implemented as user material subroutines in ABAQUS, which can capture the macroscale stress-strain response in both DS GTD111 and IN100. Even though the study was conducted on two specific Ni-base superalloys; DS GTD111 and IN100, the objective was to develop generic frameworks which should also be applicable to other alloy systems.
Download or read book International Aerospace Abstracts written by and published by . This book was released on 1999 with total page 1044 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Government Reports Annual Index written by and published by . This book was released on 1993 with total page 1834 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book 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 published by . This book was released on 2014 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Effects of Microstructural Parameters on Creep of Nickel Base Superalloy Single Crystals written by National Aeronaut Administration (Nasa) and published by . This book was released on 2020-08-05 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt: Microstructure-sensitive creep models have been developed for Ni-base superalloy single crystals. Creep rupture testing was conducted on fourteen single crystal alloys at two applied stress levels at each of two temperatures, 982 and 1093 C. The variation in creep lives among the different alloys could be explained with regression models containing relatively few microstructural parameters. At 982 C, gamma-gamma prime lattice mismatch, gamma prime volume fraction, and initial gamma prime size were statistically significant in explaining the creep rupture lives. At 1093 C, only lattice mismatch and gamma prime volume fraction were significant. These models could explain from 84 to 94 percent of the variation in creep lives, depending on test condition. Longer creep lives were associated with alloys having more negative lattice mismatch, lower gamma prime volume fractions, and finer gamma prime sizes. The gamma-gamma prime lattice mismatch exhibited the strongest influence of all the microstructural parameters at both temperatures. Although a majority of the alloys in this study were stable with respect to topologically close packed (TCP) phases, it appeared that up to approximately 2 vol% TCP phase did not affect the 1093 C creep lives under applied stresses that produced lives of approximately 200 to 300 h. In contrast, TCP phase contents of approximately 2 vol% were detrimental at lower applied stresses where creep lives were longer. A regression model was also developed for the as-heat treated initial gamma prime size; this model showed that gamma prime solvus temperature, gamma-gamma prime lattice mismatch, and bulk Re content were all statistically significant. MacKay, Rebecca A. and Gabb, Timothy P. and Nathal, Michael V. Glenn Research Center NASA/TM-2013-217868, E-18666 WBS 473452.02.03.05.04.01.01 NICKEL ALLOYS; MICROSTRUCTURE; SINGLE CRYSTALS; CREEP PROPERTIES; HEAT RESISTANT ALLOYS; CREEP TESTS; REGRESSION ANALYSIS; CRYSTAL LATTICES; CLOSE PACKED LATTICES; TURBINE BLADES; MATHEMATICAL MODELS; HIGH TEMPERATURE; CONCENTRATION (COMPOSITION); TEMPERATURE DEPENDENCE
