scholarly journals Microstructural Model for Creep-Fatigue Interaction in Grade 91 Steel

2021 ◽  
Author(s):  
Mark Messner ◽  
Ajey Venkataraman ◽  
Andrea Rovinelli ◽  
Ting-Leung Sham
Keyword(s):  
Creep Fatigue ◽  
Microstructural Model ◽  
Grade 91 ◽  
Grade 91 Steel

Creep-Fatigue Damage Evaluation of Grade 91 Steel Using Interrupt Creep Fatigue Test

2018 ◽  
Author(s):  
Uijeong Ro ◽  
Jeong Hwan Kim ◽  
Hoomin Lee ◽  
Seok Jun Kang ◽  
Moon Ki Kim
Keyword(s):  
Fatigue Damage ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Fatigue Behavior ◽  
Fe Model ◽  
Testing Method ◽  
Creep Fatigue ◽  
Grade 91 ◽  
Grade 91 Steel

The Sodium Fast-cooled Reactor (SFR), are generation IV nuclear power plants, have a target operating temperature of 550°C which makes creep-fatigue behavior more critical than a generation III nuclear power plants. So it is important to understand the nature of creep-fatigue behavior of the piping material, Grade 91 steel. The creep-fatigue damage diagram of Grade 91 steel used in ASME-NH was derived using a conventional time-fraction testing method which was originally developed for type 300 stainless steels. Multiple studies indicate that the creep-fatigue damage diagram of Grade 91 steel developed using this testing method has excessive conservatism in it. Therefore, an alternative testing method was suggested by separating creep and fatigue using interrupted creep tests. The suggested method makes it possible to control creep life consumption freely which was difficult with the previous method. It also makes it easier to observe the interaction between creep and fatigue mechanisms and microstructural evolution. In conclusion, an alternative creep-fatigue damage diagram for Grade 91 steel at 550°C was developed using an interrupt creep fatigue testing method and FE model simulation.

Unified Viscoplastic Model Coupled With Damage for Evaluation of Creep-Fatigue of Grade 91 Steel

2017 ◽  
Author(s):  
Nazrul Islam ◽  
David J. Dewees ◽  
Tasnim Hassan
Keyword(s):  
Damage Mechanics ◽  
Creep Damage ◽  
Continuum Damage Mechanics ◽  
Creep Model ◽  
Damage Evaluation ◽  
Creep Fatigue ◽  
Grade 91 ◽  
Term Creep ◽  
Grade 91 Steel

A continuum damage mechanics (CDM) coupled unified viscoplasticity model has been developed to predict the creep-fatigue life of modified Grade 91 steel. A tertiary creep model termed MPC-Omega codified in Part 10 of API (and also implemented in the ASME BP&V Code for Grade 22V and more recently Grade 91 Steel) is also employed for creep damage evaluation. As MPC-Omega has a direct relationship with Larson-Miller parameter (LMP) coefficients, creep damage coefficients in the unified constitutive model (UCM) are tied with MPC-Omega coefficients in order to utilize WRC and API 579-1 Grade 91 creep rupture database. The model is validated against long-term creep, LCF, creep-fatigue and TMF experimental responses at T = 20–600°C.

Creep-Fatigue Life Determination of Grade 91 Steel Using a Strain-Range Separation Method

2009 ◽  
Author(s):  
Wolfgang Hoffelner
Keyword(s):  
Stress Rupture ◽  
Strain Range ◽  
Inelastic Strain ◽  
Fatigue Curve ◽  
Cyclic Softening ◽  
Least Square ◽  
Creep Failure ◽  
Creep Fatigue ◽  
Grade 91 ◽  
Grade 91 Steel

The method of strain range partitioning developed by Manson offers a possibility for treatment of creep-fatigue interactions. It partitions the strain-range of a complex hysteresis loop into four elementary strain range types. Although the method has its merits it is difficult to apply because of lacking experimental data and difficult loop reconstructions. The paper describes an approach which separates the inelastic strain range only into a fatigue portion and a creep portion following both a power law Coffin-Manson relationship. Coefficients and exponents were determined by a simple least square fitting procedure from a set of literature data. The plastic part agreed very well with the experimentally determined fatigue curve. The creep part could, however, only be understood using fatigue-modified stress rupture data accounting for cyclic softening. With this approach it was possible to determine number of cycles to creep failure as a function of the pure creep strain range. This procedure was applied to a set of literature data of grade 91 steel which covered a temperature range of 500°C, 550°C, 600°C with stress controlled and strain controlled hold-times. Life-times were predicted in a range corresponding with the scatter of pure fatigue or creep curves, which means that a very good agreement was obtained. The paper will give a thorough description of the procedure and demonstrate its applicability to design codes.

Creep-Fatigue Interaction Models for Grade 91 Steel

2014 ◽  
Vol 3 (2) ◽  
pp. 20130054 ◽  
Author(s):  
Stefan Holmström ◽  
Rami Pohja ◽  
Warwick Payten
Keyword(s):  
Interaction Models ◽  
Creep Fatigue ◽  
Grade 91 ◽  
Grade 91 Steel

Evaluation of Creep-Fatigue Crack Growth for Grade 91 Steel Wide Plate

2010 ◽  
Vol 654-656 ◽  
pp. 528-531 ◽  
Author(s):  
Hyeong Yeon Lee ◽  
Jong Bum Kim ◽  
Jae Han Lee
Keyword(s):  
Stainless Steel ◽  
Fatigue Crack ◽  
Austenitic Stainless Steel ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Defect Assessment ◽  
Creep Fatigue ◽  
Grade 91 ◽  
Creep Fatigue Crack ◽  
Grade 91 Steel

An assessment of a creep-fatigue crack growth for Mod. 9Cr-1Mo steel wide plates have been carried out based on an extended French high temperature design code, RCC-MR A16 guide. The defect assessment guide of the A16 provides assessment procedures on creep-fatigue crack growth for an austenitic stainless steel, but no guidelines are available yet for a Mod. 9Cr-1Mo steel. In this study, assessments of a creep-fatigue crack growth at defects of Grade 91 steel wide plates have been carried out based on the extended A16 method for austenitic stainless steel.

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