Generation of creep-fatigue interaction diagram for modified 9Cr–1Mo steel

2021 ◽  
Vol 191 ◽  
pp. 104376
Author(s):  
J. Veerababu ◽  
Sunil Goyal ◽  
J. Vanaja ◽  
A. Nagesha ◽  
M. Vasudevan
Keyword(s):  
Interaction Diagram ◽  
Creep Fatigue

scholarly journals Determination of the Creep-Fatigue Interaction Diagram for Alloy 617

2016 ◽  
Author(s):  
J. K. Wright ◽  
L. J. Carroll ◽  
T.-L. Sham ◽  
N. J. Lybeck ◽  
R. N. Wright
Keyword(s):  
Fatigue Testing ◽  
Hold Time ◽  
Strain Range ◽  
Fatigue Tests ◽  
Alloy 617 ◽  
Interaction Diagram ◽  
Creep Fatigue ◽  
Intermediate Heat Exchanger ◽  
Cycles To Failure

Alloy 617 is the leading candidate material for an intermediate heat exchanger for the very high temperature reactor (VHTR). As part of evaluating the behavior of this material in the expected service conditions, creep–fatigue testing was performed. The cycles to failure decreased compared to fatigue values when a hold time was added at peak tensile strain. At 850°C, increasing the tensile hold duration continued to degrade 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. At 950°C, the creep–fatigue cycles to failure are not further reduced with increasing hold duration, indicating saturation occurs at relatively short hold times. The creep and fatigue damage fractions have been calculated and plotted on a creep–fatigue interaction D–diagram. Test data from creep–fatigue tests at 800 and 1000°C on an additional heat of Alloy 617 are also plotted on the D–diagram.

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.

A Comparison of Creep-Fatigue Assessment and Modelling Methods

2014 ◽  
Author(s):  
Rami H. Pohja ◽  
Stefan B. Holmström
Keyword(s):  
Fatigue Damage ◽  
Rupture Strength ◽  
Creep Damage ◽  
Creep Rupture ◽  
Design Codes ◽  
Diagram Method ◽  
Fatigue Assessment ◽  
Interaction Diagram ◽  
Fatigue Damage Accumulation ◽  
Creep Fatigue

Design codes, such as RCC-MRx and ASME III NH, for generation IV nuclear reactors use interaction diagram based method for creep-fatigue assessment. In the interaction diagram the fatigue damage is expressed as the ratio of design cycles over the allowable amount of cycles in service and the creep damage as the ratio of time in service over the design life. With this approach it is assumed that these quantities can be added linearly to represent the combined creep-fatigue damage accumulation. Failure is assumed to occur when the sum of the damage reaches a specified value, usually unity or less. The fatigue damage fraction should naturally be unity when no creep damage is present and creep damage should be unity when no fatigue damage is present. However, strict fatigue limits and safety factors used for creep rupture strengths as well as different approaches to relaxation calculation can cause a situation where creep-fatigue test data plotted according to the design rules are three orders of magnitude away from the interaction diagram unity line. Thus, utilizing the interaction diagram methods for predicting the number of creep-fatigue cycles may be inaccurate and from design point of view these methods may be overly conservative. In this paper the results of creep-fatigue tests carried out for austenitic stainless steel 316 and heat resistant ferritic-martensitic steel P91, which are included in the design codes, such as RCC-MRx, are assessed using the interaction diagram method with different levels of criteria for the creep and fatigue fractions. The test results are also compared against the predictions of a recently developed simplified creep-fatigue model which predicts the creep-fatigue damage as a function of strain range, temperature and hold period duration with little amount of fitting parameters. The Φ-model utilizes the creep rupture strength and ultimate tensile strength (UTS) of the material in question as base for the creep-fatigue prediction. Furthermore, challenge of acquiring representative creep damage fractions from the dynamic material response, i.e. cyclic softening with P91 steel, for the interaction diagram based assessment is discussed.

scholarly journals The Role of Material Modeling on Strain Range Estimation for Elevated Temperature Cyclic Life Evaluation

2018 ◽  
Author(s):  
M. C. Messner ◽  
R. I. Jetter ◽  
T.-L. Sham ◽  
Yanli Wang
Keyword(s):  
Strain Range ◽  
Creep Damage ◽  
Strain History ◽  
Stress And Strain ◽  
Interaction Diagram ◽  
Perfectly Plastic ◽  
Inelastic Analysis ◽  
Creep Fatigue ◽  
Elastic Perfectly Plastic ◽  
Simplified Procedure

High temperature nuclear reactors operating in the creep regime are designed to withstand numerous cyclic events. Current ASME code rules provide two basic paths for evaluating creep fatigue and ratcheting under these conditions; one based on full inelastic analysis intended to provide a representative stress and strain history and the other based on elastic material models with adjustments of varying complexity to account for inelastic stress and strain redistribution. More recent developments have used elastic-perfectly plastic analysis to bound the effects of cyclic service. However, these methods still rely on the separate evaluation of fatigue and creep damage utilizing a damage interaction diagram. There is a procedure under current development that uses creep-fatigue data from key feature test articles directly without the use of the damage interaction diagram. However, it requires a reasonable representation of the strain range in a structure as an input. This work develops a simplified procedure based on elastic perfectly-plasticity analysis that can be used to represent the strain range in a structure in the steady state under cyclic loading conditions.

Design Study of a Superheater Header Subjected to Cyclic and High Temperature Loading

2007 ◽  
Author(s):  
Jinhua Shi
Keyword(s):  
High Temperature ◽  
Fatigue Damage ◽  
Creep Damage ◽  
Operating Conditions ◽  
Design Code ◽  
Life Study ◽  
Interaction Diagram ◽  
Design Life ◽  
Time To Rupture ◽  
Creep Fatigue

A typical superheater header in a power station is normally subject to high pressure and high temperature loading. Due to increasing fuel prices, many stations especially gas fired power stations are operated cyclically to increase flexibility and to reduce the running costs. Accordingly, new design of heat recovery steam generators (HRSGs) has been required to undertake cyclic operations. For a base load superheater header, the design life is dominated by material creep properties (time to rupture). However, for a header subjected to two shift cyclic operating conditions, fatigue damage could be increased significantly. Therefore, creep-fatigue interaction should be considered. In this paper, a creep-fatigue design life study of a typical HRSG superheater header has been conducted under various cyclic conditions. Creep stresses for the header are calculated using a reverse design code method, and the creep damage is then obtained based on the time to rupture data. Meanwhile, fatigue calculations are carried out using the methodology given in a new European boiler design code BS EN 12952. The results of creep and fatigue damage obtained are presented in a creep-fatigue interaction diagram shown in ASME III Section NH (former N47 Case) for comparisons. After a brief discussion of the results, a conclusion is drawn.

scholarly journals A New 3D Creep-Fatigue-Elasticity Damage Interaction Diagram Based on the Total Tensile Strain Energy Density Model

Metals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 274 ◽  
Author(s):  
Qiang Wang ◽  
Naiqiang Zhang ◽  
Xishu Wang
Keyword(s):  
High Temperature ◽  
Energy Density ◽  
Fatigue Damage ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Life Prediction ◽  
Tensile Strain ◽  
Elastic Strain Energy ◽  
Interaction Diagram ◽  
Creep Fatigue

Fatigue damage, creep damage, and their interactions are the critical factors in degrading the integrity of most high-temperature engineering structures. A reliable creep-fatigue damage interaction diagram is a crucial issue for the design and assessment of high-temperature components used in power plants. In this paper, a new three-dimensional creep-fatigue-elasticity damage interaction diagram was constructed based on a developed life prediction model for both high-temperature fatigue and creep fatigue. The total tensile strain energy density concept is adopted as a damage parameter for life prediction by using the elastic strain energy density and mean stress concepts. The model was validated by a great deal of data such as P91 steel at 550 °C, Haynes 230 at 850 °C, Alloy 617 at 850 and 950 °C, and Inconel 625 at 815 °C. The estimation values have very high accuracy since nearly all the test data fell into the scatter band of 2.0.

Creep/Fatigue Interaction Correlation for 304 Stainless Steel Subjected to Strain-Controlled Cycling With Hold Times at Peak Strain

1971 ◽  
Vol 93 (4) ◽  
pp. 887-892 ◽  
Author(s):  
R. D. Campbell
Keyword(s):  
Fatigue Damage ◽  
Creep Damage ◽  
Fatigue Tests ◽  
304 Stainless Steel ◽  
Peak Strain ◽  
Interaction Diagram ◽  
Data Scatter ◽  
Creep Fatigue ◽  
Relaxation Curves ◽  
Life Fraction

A numerical integration of creep relaxation curves from strain-controlled fatigue tests with hold times introduced at peak strain is performed to sum creep damage by the linear life fraction rule. Fatigue damage is summed and an interaction diagram for creep and fatigue damage is constructed. Data scatter about the interaction curve is compared to scatter for independent creep rupture and fatigue tests from the identical heat of material.

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