scholarly journals Evaluation of Creep-Fatigue Damage Based on Simplified Model Test Approach

2013 ◽  
Author(s):  
Yanli Wang ◽  
Tianlei Li ◽  
T.-L. (Sam) Sham ◽  
Robert I. Jetter
Keyword(s):  
Fatigue Damage ◽  
High Temperatures ◽  
Test Data ◽  
Model Test ◽  
Hold Time ◽  
Simplified Model ◽  
Creep Fatigue ◽  
Asme Code ◽  
Cyclic Damage ◽  
Very High

Current methods used in the ASME Code, Subsection NH for the evaluation of creep-fatigue damage are based on the separation of elevated temperature cyclic damage into two parts, creep damage and fatigue damage. This presents difficulties in both evaluation of test data and determination of cyclic damage in design. To avoid these difficulties, an alternative approach was identified, called the Simplified Model Test or SMT approach based on the use of creep-fatigue hold time test data from test specimens with elastic follow-up conservatively designed to bound the response of general structural components of interest. A key feature of the methodology is the use of the results of elastic analysis directly in design evaluation similar to current methods in the ASME Code, Subsection NB. Although originally developed for current material included in Subsection NH, recent interest in the application of Alloy 617 for components operating at very high temperatures has caused renewed interest in the SMT approach because it provides an alternative to the proposed restriction on the use of current Subsection NH simplified methods at very high temperatures. A comprehensive review and assessment of five representative simplified methods for creep-fatigue damage evaluation is presented in Asayama [1]. In this review the SMT methodology was identified as the best long term approach but the need for test data precluded its near term implementation. Asayama and Jetter [2] is a summary of the more comprehensive report by Asayama [1] with a summary of the SMT approach presented by Jetter [3]. In this paper, the previously documented development of the SMT approach and applicable restrictions are discussed and reviewed; the design of the SMT specimen, measurement issues and constraints are presented; the test apparatus and measurement system is described; initial test results and their application to a prototypic design curve are presented; and further testing and analysis for ASME Code incorporation are discussed.

Pressurized Creep-Fatigue Testing of Alloy 617 Using Simplified Model Test Method

2017 ◽  
Author(s):  
Yanli Wang ◽  
Robert I. Jetter ◽  
T.-L. Sham
Keyword(s):  
Elevated Temperature ◽  
Hysteresis Loop ◽  
Fatigue Damage ◽  
Model Test ◽  
Test Method ◽  
Simplified Model ◽  
Damage Evaluation ◽  
Primary Stress ◽  
Creep Fatigue ◽  
Cyclic Damage

The Simplified Model Test (SMT) is an alternative approach to determine cyclic life at elevated temperature and avoids parsing the damage into creep and fatigue components. The Elastic-Perfectly Plastic (EPP) combined integrated creep-fatigue damage evaluation approach incorporates the SMT data based approach for creep-fatigue damage evaluation into the EPP methodology to avoid the separate evaluation of creep and fatigue damage and to eliminate the requirement for stress classification as in current methods; thus greatly simplifying evaluation of elevated temperature cyclic service. The conceptual basis of the SMT approach is that if the effects of plasticity, creep and strain redistribution in the SMT specimen result in a stress-strain hysteresis loop that envelopes the hysteresis loop at the peak strain location in the component, then the SMT results can be used to assess the cyclic damage in the component. The original SMT concept (Jetter, 1998) considered that the effects of sustained primary stress loading could be safely neglected because the allowable local stress and strain levels were much higher than the allowable sustained primary stress levels. This key assumption requires experimental verification. The influence of the internal pressure on SMT creep-fatigue life is demonstrated and the effect of primary load on the SMT design approach is discussed.

Structural Integrity Code and Regulatory Issues in the Design of High Temperature Reactors

2008 ◽  
Author(s):  
William J. O’Donnell ◽  
Amy B. Hull ◽  
Shah Malik
Keyword(s):  
High Temperature ◽  
Elevated Temperature ◽  
Structural Integrity ◽  
Cyclic Creep ◽  
Creep Rupture ◽  
Creep Fatigue ◽  
Asme Code ◽  
High Temperature Reactors ◽  
Gen Iv ◽  
Very High

Since the 1980s, the ASME Code has made numerous improvements in elevated-temperature structural integrity technology. These advances have been incorporated into Section II, Section VIII, Code Cases, and particularly Subsection NH of Section III of the Code, “Components in Elevated Temperature Service.” The current need for designs for very high temperature and for Gen IV systems requires the extension of operating temperatures from about 1400°F (760°C) to about 1742°F (950°C) where creep effects limit structural integrity, safe allowable operating conditions, and design life. Materials that are more creep and corrosive resistant are needed for these higher operating temperatures. Material models are required for cyclic design analyses. Allowable strains, creep fatigue and creep rupture interaction evaluation methods are needed to provide assurance of structural integrity for such very high temperature applications. Current ASME Section III design criteria for lower operating temperature reactors are intended to prevent through-wall cracking and leaking and corresponding criteria are needed for high temperature reactors. Subsection NH of Section III was originally developed to provide structural design criteria and limits for elevated-temperature design of Liquid-Metal Fast Breeder Reactor (LMFBR) systems and some gas-cooled systems. The U.S. Nuclear Regulatory Commission (NRC) and its Advisory Committee for Reactor Safeguards (ACRS) reviewed the design limits and procedures in the process of reviewing the Clinch River Breeder Reactor (CRBR) for a construction permit in the late 1970s and early 1980s, and identified issues that needed resolution. In the years since then, the NRC, DOE and various contractors have evaluated the applicability of the ASME Code and Code Cases to high-temperature reactor designs such as the VHTGRs, and identified issues that need to be resolved to provide a regulatory basis for licensing. The design lifetime of Gen IV Reactors is expected to be 60 years. Additional materials including Alloy 617 and Hastelloy X need to be fully characterized. Environmental degradation effects, especially impure helium and those noted herein, need to be adequately considered. Since cyclic finite element creep analyses will be used to quantify creep rupture, creep fatigue, creep ratcheting and strain accumulations, creep behavior models and constitutive relations are needed for cyclic creep loading. Such strain- and time-hardening models must account for the interaction between the time-independent and time-dependent material response. This paper describes the evolving structural integrity evaluation approach for high temperature reactors. Evaluation methods are discussed, including simplified analysis methods, detailed analyses of localized areas, and validation needs. Regulatory issues including weldment cracking, notch weakening, creep fatigue/creep rupture damage interactions, and materials property representations for cyclic creep behavior are also covered.

Creep-Fatigue Damage and Crack Initiation for a Mod 9Cr-1Mo Structure With Weldments

2007 ◽  
Author(s):  
Hyeong-Yeon Lee ◽  
Se-Hwan Lee ◽  
Jong-Bum Kim ◽  
Jae-Han Lee
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
Fatigue Damage ◽  
Hold Time ◽  
Fatigue Crack Initiation ◽  
Creep Damage ◽  
Steel Specimen ◽  
Structural Test ◽  
Creep Fatigue ◽  
Creep Fatigue Crack

A structural test and evaluation on creep-fatigue damage, and creep-fatigue crack initiation have been carried out for a Mod. 9Cr-1Mo steel structural specimen with weldments. The conservatisms of the design codes of ASME Section III subsection and NH and RCC-MR codes were quantified at the welded joints of Mod.9Cr-1Mo steel and 316L stainless steel with the observed images from the structural test. In creep damage evaluation using the RCC-MR code, isochronous curve has been used rather than directly using the creep law as the RCC-MR specifies. A y-shaped steel specimen of a diameter 500mm, height 440mm and thickness 6.35mm is subjected to creep-fatigue loads with two hours of a hold time at 600°C and a primary nominal stress of 30MPa. The defect assessment procedures of RCC-MR A16 guide do not provide a procedure for Mod.9Cr-1Mo steel yet. In this study application of σd method for the assessment of creep-fatigue crack initiation has been examined for a Mod. 9Cr-1Mo steel structure.

An Evaluation of Creep-Fatigue Damage for the Prototype Process Heat Exchanger of the NHDD Plant

2011 ◽  
Vol 133 (5) ◽  
Author(s):  
Hyeong-Yeon Lee ◽  
Kee-Nam Song ◽  
Yong-Wan Kim ◽  
Sung-Deok Hong ◽  
Hong-Yune Park
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
High Temperature ◽  
Fatigue Damage ◽  
Inlet Temperature ◽  
Alloy 617 ◽  
Element Analysis ◽  
Creep Fatigue ◽  
Process Heat ◽  
Very High

A process heat exchanger (PHE) transfers the heat generated from a nuclear reactor to a sulfur-iodine hydrogen production system in the Nuclear Hydrogen Development and Demonstration, and was subjected to very high temperature up to 950°C. An evaluation of creep-fatigue damage, for a prototype PHE, has been carried out from finite element analysis with the full three dimensional model of the PHE. The inlet temperature in the primary side of the PHE was 950°C with an internal pressure of 7 MPa, while the inlet temperature in the secondary side of the PHE is 500°C with internal pressure of 4 MPa. The candidate materials of the PHE were Alloy 617 and Hastelloy X. In this study, only the Alloy 617 was considered because the high temperature design code is available only for Alloy 617. Using the full 3D finite element analysis on the PHE model, creep-fatigue damage evaluation at very high temperature was carried out, according to the ASME Draft Code Case for Alloy 617, and technical issues in the Draft Code Case were raised.

Proposals of Improvements of RCC-MR Creep-Fatigue Rules

2007 ◽  
Author(s):  
Marie-Noe¨l Berton ◽  
Olivier Ancelet ◽  
Marie The´re`se Cabrillat ◽  
Ste´phane Chapuliot
Keyword(s):  
Stress Relaxation ◽  
Fatigue Damage ◽  
High Temperatures ◽  
Dwell Time ◽  
Damage Evaluation ◽  
Fast Reactors ◽  
Creep Fatigue ◽  
Sodium Fast Reactors ◽  
Gen Iv ◽  
Current Rule

The RCC-MR creep-fatigue rules were developed and written in the framework of studies for the first SFR (Sodium Fast Reactors). These reactors were characterized by low primary loads and moderately high temperatures. The rule thus has to be improved with the aim of decreasing its conservatisms in case of higher temperatures and/or higher pressures (for GEN IV Gas Cooled Reactors). Studies were realized to improve the rule on the following points: - the position of the temperature dwell time in the cycle : the current rule always considers that the dwell time is located at one of the extremes of the cycle, what can be very conservative in some cases, - the symmetrisation effect of the stabilized cycle, - the case where the primary loads vary during the cycle, - the primary and secondary stresses combination during the temperature dwell time for the evaluation of the stress relaxation. These works are based on viscoelastoplastic calculations of stabilized cycles and the new proposals are applied on different tests. The consequences on creep-fatigue damage evaluation can be very significant.

scholarly journals Effect of Internal Pressurization on the Creep-Fatigue Performance of Alloy 617 Based on Simplified Model Test Method

2019 ◽  
Author(s):  
Y. Wang ◽  
B. Jetter ◽  
T.-L. Sham
Keyword(s):  
Model Test ◽  
Design Method ◽  
Local Stress ◽  
Fatigue Loading ◽  
Test Method ◽  
Simplified Model ◽  
Alloy 617 ◽  
Primary Stress ◽  
Creep Fatigue ◽  
The Impact

Abstract The Simplified Model Test (SMT) is an alternative approach to determine cyclic life at elevated temperature and avoids parsing the damage into creep and fatigue components. The original SMT concept [1] considered that the effects of sustained primary stress loading could be safely neglected because the allowable local stress and strain levels were much higher than the allowable sustained primary stress levels. This key assumption is critically evaluated on Alloy 617 using internal pressurized cylindrical SMT specimens at 950 °C. The impact of combined internal pressurization and displacement-controlled creep-fatigue loading on the SMT cycle life is demonstrated at different strain ranges. The effect of primary load on the SMT design method is discussed.

scholarly journals Development of Simplified Model Test Methods for Creep-Fatigue Evaluation

2019 ◽  
Author(s):  
Y. Wang ◽  
B. Jetter ◽  
M. C. Messner ◽  
T.-L. Sham
Keyword(s):  
Model Test ◽  
Evaluation Method ◽  
Test Methods ◽  
Simplified Model ◽  
Test Results ◽  
Interaction Diagram ◽  
Creep Fatigue ◽  
Fatigue Evaluation ◽  
Creep Regime ◽  
Further Development

Abstract The Simplified Model Test (SMT) approach is an alternative creep-fatigue evaluation method that no longer requires the use of the damage interaction diagram, or D-diagram. The reason is that the combined effects of creep and fatigue are accounted for in the test data by means of a SMT specimen that is designed to replicate or bound the stress and strain redistribution that occurs in actual components when loaded in the creep regime. However, creep-fatigue experiments on SMT key feature articles are specialized and difficult to perform by the general research community. In this paper, two innovative SMT based creep-fatigue experimental methods are developed and implemented. These newly-developed SMT test methods have resolved all the critical challenges in the SMT key feature article testing and enable the potential of further development of the SMT based creep-fatigue evaluation method into a standard testing method. Scoping test results on Alloy 617 and SS 316H using the newly developed SMT methods are summarized and discussed. The concepts of the SMT methodology for creep-fatigue evaluation are explained.

scholarly journals Alloy 617 Creep–Fatigue Damage Evaluation Using Specimens With Strain Redistribution

2014 ◽  
Vol 137 (2) ◽  
Author(s):  
Yanli Wang ◽  
T.-L. Sham ◽  
Robert I. Jetter
Keyword(s):  
Hold Time ◽  
Damage Evaluation ◽  
Test Results ◽  
Structural Components ◽  
Cyclic Life ◽  
Alloy 617 ◽  
Creep Fatigue ◽  
Asme Code ◽  
Time Test

The simplified model test (SMT) method is an alternate approach to determine the cyclic life at elevated temperature. It is based on the use of creep–fatigue hold time test data from test specimens with elastic follow-up conservatively designed to bound the response of general structural components. In this paper, the previously documented development of the SMT approach and applicable restrictions are reviewed; the design of the Alloy 617 SMT specimen, measurement issues and constraints are presented; initial test results and their application to a prototypic design curve are presented; and further testing and analysis for ASME code incorporation are discussed.

Evaluation of Creep-Fatigue Life Using Backscattering of Rayleigh Surface Wave

2005 ◽  
Vol 297-300 ◽  
pp. 415-420 ◽  
Author(s):  
Byeong Soo Lim ◽  
Bum Joon Kim ◽  
Sung Jin Song ◽  
Young H. Kim
Keyword(s):  
Fatigue Life ◽  
Surface Wave ◽  
Fatigue Damage ◽  
Power Plants ◽  
Fatigue Behavior ◽  
Hold Time ◽  
Rayleigh Surface Wave ◽  
P92 Steel ◽  
Creep Fatigue ◽  
Main Steam

The application of nondestructive evaluation to creep-fatigue damage was examined in this paper. Generally, as the hold time of static load increases, the degradation of material becomes more rapid and the creep-fatigue life decreases. Therefore, in the evaluation of creep-fatigue strength and life of high-pressure vessel such as main steam pipe at high temperature is very important in power plants. In this study, the creep-fatigue behavior of P92 steel was evaluated nondestructively by the backscattered ultrasound using the creep-fatigue specimens. The results obtained by Rayleigh surface wave of backscattered ultrasound were compared and analyzed with the experimental parameters. Also, the relation between the SDA (slope of degraded area) and creep-fatigue life was examined. From the result of nondestructive test, we suggest that SDA would be used as the new parameter for the evaluation of creep-fatigue damage. As the degradation increased, the SDA decreased and also the creep-fatigue life decreased.

Evaluation of Creep-Fatigue Damage for Prototype Process Heat Exchanger of the NHDD Plant

2010 ◽  
Author(s):  
Hyeong-Yeon Lee ◽  
Kee-Nam Song ◽  
Yong-Wan Kim ◽  
Sung-Deok Hong ◽  
Hong-Yune Park
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
High Temperature ◽  
Fatigue Damage ◽  
Inlet Temperature ◽  
Alloy 617 ◽  
Element Analysis ◽  
Creep Fatigue ◽  
Process Heat ◽  
Very High

A process heat exchanger (PHE) transfers the heat generated from a nuclear reactor to a sulfur-iodine hydrogen production system in the NHDD (Nuclear Hydrogen Development and Demonstration), and was subjected to very high temperature up to 950°C. An evaluation of creep-fatigue damage, for a prototype PHE, has been carried out from finite element analysis with the full three dimensional model of the PHE. The inlet temperature in the primary side of the PHE was 950°C with an internal pressure of 7MPa while the inlet temperature in the secondary side of the PHE is 500°C with internal pressure of 4MPa. The candidate materials of the PHE were Alloy 617 and Hastelloy X. In this study, only the Alloy 617 was considered because the high temperature design code is available only for Alloy 617. Using the full 3D finite element analysis on the PHE model, creep-fatigue damage evaluation at very high temperature was carried out, according to the ASME Draft Code Case for Alloy 617, and technical issues in the draft Code Case were raised.

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