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Creep Fatigue Damage Investigation And Modeling Of Alloy 617 At High Temperatures
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Book Synopsis Creep-fatigue Damage Investigation and Modeling of Alloy 617 at High Temperatures by : Fraaz Tahir
Download or read book Creep-fatigue Damage Investigation and Modeling of Alloy 617 at High Temperatures written by Fraaz Tahir and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Very High Temperature Reactor (VHTR) is one of six conceptual designs proposed for Generation IV nuclear reactors. Alloy 617, a solid solution strengthened Ni-base superalloy, is currently the primary candidate material for the tubing of the Intermediate Heat Exchanger (IHX) in the VHTR design. Steady-state operation of the nuclear power plant at elevated temperatures leads to creep deformation, whereas loading transients including startup and shutdown generate fatigue. A detailed understanding of the creep-fatigue interaction in Alloy 617 is necessary before it can be considered as a material for nuclear construction in ASME Boiler and Pressure Vessel Code. Current design codes for components undergoing creep-fatigue interaction at elevated temperatures require creep-fatigue testing data covering the entire range from fatigue-dominant to creep-dominant loading. Classical strain-controlled tests, which produce stress relaxation during the hold period, show a saturation in cycle life with increasing hold periods due to the rapid stress-relaxation of Alloy 617 at high temperatures. Therefore, applying longer hold time in these tests cannot generate creep-dominated failure. In this study, uniaxial isothermal creep-fatigue tests with non-traditional loading waveforms were designed and performed at 850 and 950°C, with an objective of generating test data in the creep-dominant regime. The new loading waveforms are hybrid strain-controlled and force-controlled testing which avoid stress relaxation during the creep hold. The experimental data showed varying proportions of creep and fatigue damage, and provided evidence for the inadequacy of the widely-used time fraction rule for estimating creep damage under creep-fatigue conditions. Micro-scale damage features in failed test specimens, such as fatigue cracks and creep voids, were quantified using a Scanning Electron Microscope (SEM) to find a correlation between creep and fatigue damage. Quantitative statistical imaging analysis showed that the microstructural damage features (cracks and voids) are correlated with a new mechanical driving force parameter. The results from this image-based damage analysis were used to develop a phenomenological life-prediction methodology called the effective time fraction approach. Finally, the constitutive creep-fatigue response of the material at 950°C was modeled using a unified viscoplastic model coupled with a damage accumulation model. The simulation results were used to validate an energy-based constitutive life-prediction model, as a mechanistic model for potential component and structure level creep-fatigue analysis.
Book Synopsis High Temperature Fatigue and Fatigue-Creep Responses of Alloy 617 - Experimental and Unified Constitutive Modeling by : Patrick Graham Pritchard
Download or read book High Temperature Fatigue and Fatigue-Creep Responses of Alloy 617 - Experimental and Unified Constitutive Modeling written by Patrick Graham Pritchard and published by . This book was released on 2014 with total page 114 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Report on FY15 Alloy 617 SMT Creep-Fatigue Test Results by :
Download or read book Report on FY15 Alloy 617 SMT Creep-Fatigue Test Results written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: For the temperature range of 990-950C, Alloy 617 is a candidate IHX structural material for high temperature gas reactors (HTGRs) because of its high temperature creep properties. Also, its superior strength over a broad temperature range also offers advantages for certain component applications. In order for the designers to be able to use Alloy 617 for these high temperature components, Alloy 617 has to be approved for use in Section III (the nuclear section) of the ASME (American Society of Mechanical Engineers) Boiler and Pressure Vessel Code. A plan has been developed to propose a Code Case for use of Alloy 617 at elevated temperature in Section III of the ASME Code by September 2015. There has not been a new high temperature material approved for use in Section III for almost 20 years. The Alloy 617 Code Case effort would lead the way to establish a path for Code qualification of new high temperature materials of interest to other advanced SMRs. Creep-fatigue at elevated temperatures is the most damaging structural failure mode. In the past 40 years significant efforts have been devoted to the elevated temperature Code rule development in Section III, Subsection NH* of the ASME Boiler and Pressure Vessel Code, to ascertain conservative structural designs to prevent creep-fatigue failure. The current Subsection NH creep-fatigue procedure was established by the steps of (1) analytically obtaining a detailed stress-strain history, (2) comparing the stress and strain components to cyclic test results deconstructed into stress and strain quantities, and (3) recombining the results to obtain a damage function in the form of the so-called creep-fatigue damage-diagram. The deconstruction and recombination present difficulties in evaluation of test data and determination of cyclic damage in design. The uncertainties in these steps lead to the use of overly conservative design factors in the current creep-fatigue procedure. In addition, and of major significance to the viability of the Alloy 617 Code Case, the use of the current elastic analysis based rules in Subsection NH for the evaluation of strain limits (a precursor for the creep-fatigue rules) and the creep-fatigue rules themselves have been deemed inappropriate for Alloy 617 at temperatures above 650C (Corum and Brass, 1991). The rationale for this exclusion is that at higher temperatures it is not feasible to decouple plasticity and creep, which is the basis for the current simplified rules. This temperature, 650C, is well below the temperature range of interest for this material for the High Temperature Gas Cooled Reactor (HTGR) as well as the VHTR. The only current alternative is, thus, a full inelastic analysis which requires sophisticated material models which have not yet been formulated and verified. To address the prohibition on the use of current methods at very high temperatures, proposed Code rules have been developed which are based on the use of elastic-perfectly plastic (E-PP) analysis methods and which are expected to be applicable to very high temperatures. To provide data to implement the proposed rules and to verify their application, a series of tests have been initiated. One test concept, the Simplified Model Test (SMT), takes into account the stress and strain redistribution in real structures by including representative follow-up characteristics in the test specimen. The correlation parameter between test and design is the elastically calculated strain, and the dependent test variable is the observed cycles to failure. Although the initial priority for the SMT approach is to generate data to support validation of the E-PP Code Case for evaluation of creep-fatigue damage, the broader goal of the SMT approach is to develop a methodology for evaluation of creep fatigue damage which is simpler to implement than the current complex rules and applicable to the full temperature range from ambient conditions to the very high temperature creep regime of 900 ...
Book Synopsis Progress Report on Long Hold Time Creep Fatigue of Alloy 617 at 850°C. by :
Download or read book Progress Report on Long Hold Time Creep Fatigue of Alloy 617 at 850°C. written by and published by . This book was released on 2015 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt: Alloy 617 is the leading candidate material for an intermediate heat exchanger for the very high temperature reactor. To evaluate the behavior of this material in the expected service conditions, strain-controlled cyclic tests that include long hold times up to 240 minutes at maximum tensile strain were conducted at 850°C. In terms of the total number of cycles to failure, the fatigue resistance decreased when a hold time was added at peak tensile strain. Increases in the tensile hold duration degraded the creep-fatigue resistance, at least to the investigated strain controlled hold time of up to 60 minutes at the 0.3% strain range and 240 minutes at the 1.0% strain range. The creep-fatigue deformation mode is considered relative to the lack of saturation, or continually decreasing number of cycles to failure with increasing hold times. Additionally, preliminary values from the 850°C creep-fatigue data are calculated for the creep-fatigue damage diagram and have higher values of creep damage than those from tests at 950°C.
Book Synopsis Prediction of the Creep-Fatigue Lifetime of Alloy 617 by :
Download or read book Prediction of the Creep-Fatigue Lifetime of Alloy 617 written by and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A relatively simple method using the nominal constant average stress information and the creep rupture model is developed to predict the creep-fatigue lifetime of Alloy 617, in terms of time to rupture. The nominal constant average stress is computed using the stress relaxation curve. The predicted time to rupture can be converted to number of cycles to failure using the strain range, the strain rate during each cycle, and the hold time information. The predicted creep-fatigue lifetime is validated against the experimental measurements of the creep-fatigue lifetime collected using conventional laboratory creep-fatigue tests. High temperature creep-fatigue tests of Alloy 617 were conducted in air at 950°C with a tensile hold period of up to 1800s in a cycle at total strain ranges of 0.3% and 0.6%. It was observed that the proposed method is conservative in that the predicted lifetime is less than the experimentally determined values. The approach would be relevant to calculate the remaining useful life to a component like a steam generator that might fail by the creep-fatigue mechanism.
Book Synopsis Creep and Environmental Effects on the High Temperature Creep-Fatigue Behavior of Alloy 617 by : L. J. Carroll
Download or read book Creep and Environmental Effects on the High Temperature Creep-Fatigue Behavior of Alloy 617 written by L. J. Carroll and published by . This book was released on 2011 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: Alloy 617 is the leading candidate material for an intermediate heat exchanger (IHX) of the very high temperature reactor (VHTR), expected to have an outlet temperature as high as 950°C. Acceptance of Alloy 617 in Section III of the ASME Code for nuclear construction requires a detailed understanding of the creep-fatigue behavior. Strain-controlled low cycle fatigue (LCF) tests including hold times up to 1800 s at maximum tensile strain were conducted at 950°C and a total strain range of 0.3 % in air and in a simulated VHTR impure helium. For similar test conditions, the creep-fatigue behavior was globally similar in both environments. The fatigue resistance decreased when a hold time was added at peak tensile strain, consistent with the observed change in fracture mode from transgranular to intergranular. Further increases in the tensile hold time, beyond 180 s, were not detrimental to the creep-fatigue resistance. The influence of oxidation on the fatigue crack initiation and propagation is discussed. Bulk damage in the form of grain boundary cracking was present in the interior of the creep-fatigue specimens. This bulk cracking was quantified and found to be similar for hold times of up to 1800 s consistent with the saturation in failure lives.
Book Synopsis Introduction to Creep by : R. W. Evans
Download or read book Introduction to Creep written by R. W. Evans and published by Routledge. This book was released on 1993 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Fracture at High Temperatures by : Hermann Riedel
Download or read book Fracture at High Temperatures written by Hermann Riedel and published by Springer. This book was released on 2014-01-13 with total page 430 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis High Temperature Creep-fatigue by : Ryuichi Ohtani
Download or read book High Temperature Creep-fatigue written by Ryuichi Ohtani and published by . This book was released on 1988 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Role of Environment of High Temperature Creep-Fatigue Behavior of Alloy 617 by :
Download or read book The Role of Environment of High Temperature Creep-Fatigue Behavior of Alloy 617 written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Previously submitted in STIMS - INL/CON-09-17350.
Book Synopsis Modeling of Thermomechanical Fatigue Damage in Coated Alloys by : Y. Kadioglu
Download or read book Modeling of Thermomechanical Fatigue Damage in Coated Alloys written by Y. Kadioglu and published by . This book was released on 1993 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: A life prediction model that determines the contribution of fatigue, creep and environmental damage to failure was developed for an aluminide coated nickel-based superalloy, Mar-M247. In the first phase of the study, isothermal (IF) and thermomechanical fatigue (TMF) experiments were conducted to investigate the experimental damage mechanisms. In the second phase, an analytical technique was advanced to compute the stress fields due to a surface inclusion in a half-space where the inclusion simulates the oxide spike. The technique is based on Eshelby's equivalent inclusion method and elucidates the mismatch in elastic moduli and thermal expansion coefficients of the matrix and the oxide spike on local strain fields. The fatigue life results of several experiments, along with the local stress-strain field in the vicinity of an oxide spike, were employed to define the model constants. Life prediction bounds are established corresponding to short-time coating protection, where the coating provides inconsiderable protection to substrate, and long-time coating protection, where the coating provides appreciable protection to the substrate. For in-phase loading, since the failure is governed by creep damage, the nature of coating protection did not influence the fatigue lives. The out-of-phase predictions corresponding to short-time coating protection and the experimental data coincided as the maximum temperature increased in the experiments, confirming that the coating provides unsubstantial protection at higher temperatures.
Book Synopsis Creep-Fatigue Behavior of Alloy 617 at 850 and 950°C, Revision 2 by :
Download or read book Creep-Fatigue Behavior of Alloy 617 at 850 and 950°C, Revision 2 written by and published by . This book was released on 2015 with total page 29 pages. Available in PDF, EPUB and Kindle. Book excerpt: Alloy 617 is the leading candidate material for an Intermediate Heat Exchanger (IHX) of the Very High Temperature Reactor (VHTR). To evaluate the behavior of this material in the expected service conditions, strain-controlled cyclic tests including hold times up to 9000 s at maximum tensile strain were conducted at 850 and 950 degrees C. At both temperatures, the fatigue resistance decreased when a hold time was added at peak tensile strain. The magnitude of this effect depended on the specific mechanisms and whether they resulted in a change in fracture mode from transgranular in pure fatigue to intergranular in creep-fatigue for a particular temperature and strain range combination. Increases in the tensile hold duration beyond an initial value were not detrimental to the creep-fatigue resistance at 950 degrees C but did continue to degrade the lifetimes at 850 degrees C.
Book Synopsis A BRIEF REVIEW OF MODELS REPRESENTING CREEP OF ALLOY 617 by :
Download or read book A BRIEF REVIEW OF MODELS REPRESENTING CREEP OF ALLOY 617 written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Alloy 617 is being considered for the construction of components to operate in the Next Generation Nuclear Plant (NGNP). Service temperatures will range from 650 to 1000 C. To meet the needs of the conceptual designers of this plant, a materials handbook is being developed that will provide information on alloy 617, as well as other materials of interest. The database for alloy 617 to be incorporated into the handbook was produced in the 1970s and 1980s, while creep and damage models were developed from the database for use in the design of high-temperature gas-cooled reactors. In the work reported here, the US database and creep models are briefly reviewed. The work reported represents progress toward a useful model of the behavior of this material in the temperature range of 650 to 1000 C.
Book Synopsis Investigation of Fatigue and Creep-fatigue Crack Growth in Alloy 709 at Elevated Temperatures by : Nicholas L. Shaber
Download or read book Investigation of Fatigue and Creep-fatigue Crack Growth in Alloy 709 at Elevated Temperatures written by Nicholas L. Shaber and published by . This book was released on 2018 with total page 98 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Creep written by Tomasz Tański and published by BoD – Books on Demand. This book was released on 2018-01-10 with total page 270 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book contains 12 chapters with original and innovative research studies in the issues related to the broadly defined creep effect, which concerns not only the area of construction materials but also natural phenomena. The emphasis on the discussion of a new trend of experimental creep testing, which binds the classic creep methods to seek the correlation of parameters obtained in tests, deserves particular attention. This book aims to provide the readers, including, but not limited to, students and doctoral students and also the research personnel and engineers involved in the operation of equipment and structural components as well as specialists in high-temperature creep-resisting materials, with a comprehensive review of new trends in the field of creep-exposed materials and their research methodology. The chapters of this book were developed by respected and well-known researchers from different countries.
Book Synopsis Damage Mechanisms and Life Assessment of High Temperature Components by : Ramaswamy Viswanathan
Download or read book Damage Mechanisms and Life Assessment of High Temperature Components written by Ramaswamy Viswanathan and published by ASM International. This book was released on 1989 with total page 497 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Alloy 617 Creep-fatigue Damage Evaluation Using Specimens with Strain Redistribution by :
Download or read book Alloy 617 Creep-fatigue Damage Evaluation Using Specimens with Strain Redistribution written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
