scholarly journals Collect Available Creep-Fatigue Data and Study Existing Creep-Fatigue Evaluation Procedures for Grade 91 and Hastelloy XR

2007 ◽  
Author(s):  
Tai Asayama ◽  
Yukio Tachibana
Keyword(s):  
Evaluation Procedures ◽  
Fatigue Data ◽  
Creep Fatigue ◽  
Grade 91 ◽  
Fatigue Evaluation

Accuracy and Margin in Creep-Fatigue Evaluation for Modified 9Cr-1Mo Steel

2007 ◽  
Author(s):  
Yukio Takahashi
Keyword(s):  
Stress Relaxation ◽  
Nuclear Power ◽  
Creep Damage ◽  
Assessment Method ◽  
Fatigue Tests ◽  
Simple Method ◽  
Component Design ◽  
Creep Fatigue ◽  
Grade 91 ◽  
Fatigue Evaluation

Modified 9Cr-1Mo steel (ASME SA-213, Grade 91) is regarded as a promising candidate for structural materials in some of the nuclear power generation plants considered in Generation-IV project. If it is used at high temperature conditions, consideration of creep-fatigue interaction in addition to simple creep rupture is needed in component design. The author has been conducting many creep-fatigue tests for the steel at temperatures between 550°C and 650°C in order to search for a suitable creep-fatigue assessment method. It was found that creep damage at failure estimated by applying the time fraction approach to measured stress relaxation data strongly depended on the test temperature and became quite small at 550°C. However, application of calculated stress relaxation brought about the increase of creep damage over the linear damage summation line. Furthermore, addition of design factors significantly increased the values of creep and fatigue damages, making margin against failure quite large. A new definition of creep damage as a ductility consumer in strain based approach gave a simple method to estimate creep damage more properly and stably with a much smaller sensitivity on the stress relaxation behavior.

Creep-Fatigue Evaluation Based on the Overstress

1991 ◽  
Vol 113 (2) ◽  
pp. 187-193 ◽  
Author(s):  
Y. Asada ◽  
Y. Okamoto ◽  
T. Hashimoto
Keyword(s):  
Fatigue Behavior ◽  
High Vacuum ◽  
Back Stress ◽  
Strain Response ◽  
Fatigue Data ◽  
Creep Fatigue ◽  
Fatigue Evaluation ◽  
Damage Equation ◽  
Very High ◽  
High Vacuum Environment

There is summarized a series of creep-fatigue data on a normalized and tempered 2 1/4Cr-1Mo steel obtained at 550°C in a very high vacuum environment under a wide variety of a strain-time program. A special feature of a stress-strain response of the steel is described to give the overstress and the internal back stress. A damage equation is developed to predict a creep-fatigue behavior which is free from the environmental effect.

Development of 2012 Edition of JSME Code for Design and Construction of Fast Reactors: (4) Creep–Fatigue Evaluation Method for Modified 9Cr–1Mo Steel

2013 ◽  
Author(s):  
Shigeru Takaya ◽  
Yuji Nagae ◽  
Tai Asayama
Keyword(s):  
Evaluation Method ◽  
Time To Failure ◽  
Test Results ◽  
Fast Reactors ◽  
Material Test ◽  
Creep Fatigue ◽  
Summation Rule ◽  
Fatigue Evaluation ◽  
Failure Life ◽  
Design And Construction

This paper describes a creep–fatigue evaluation method for modified 9Cr–1Mo steel, which has been newly included in the 2012 edition of the JSME code for design and construction of fast reactors. In this method, creep and fatigue damages are evaluated on the basis of Miner’s rule and the time fraction rule, respectively, and the linear summation rule is employed as the failure criterion. Investigations using material test results are conducted, which show that the time fraction approach can conservatively predict failure life if margins on the initial stress of relaxation and the stress relaxation rate are embedded. In addition, the conservatism of prediction tends to increase with time to failure. Comparison with the modified ductility exhaustion method, which is known to have good failure life predictability in material test results, shows that the time fraction approach predicts failure lives to be shorter in long-term strain hold conditions, where material test data is hardly obtained. These results confirm that the creep–fatigue evaluation method in the code has implicit conservatism.

Development of New Design Fatigue Curves in Japan: Proposal of a New Fatigue Evaluation Method

2018 ◽  
Author(s):  
Seiji Asada ◽  
Akihiko Hirano ◽  
Toshiyuki Saito ◽  
Yasukazu Takada ◽  
Hideo Kobayashi
Keyword(s):  
Stainless Steels ◽  
Evaluation Method ◽  
Austenitic Stainless Steels ◽  
Fatigue Tests ◽  
Carbon Steels ◽  
Low Alloy Steels ◽  
Stress Effect ◽  
Fatigue Data ◽  
Alloy Steels ◽  
Fatigue Evaluation

In order to develop new design fatigue curves for carbon steels & low-alloy steels and austenitic stainless steels and a new design fatigue evaluation method that are rational and have clear design basis, Design Fatigue Curve (DFC) Phase 1 subcommittee and Phase 2 subcommittee were established in the Atomic Energy Research Committee in the Japan Welding Engineering Society (JWES). The study on design fatigue curves was actively performed in the subcommittees. In the subcommittees, domestic and foreign fatigue data of small test specimens in air were collected and a comprehensive fatigue database (≈6000 data) was constructed and the accurate best-fit curves of carbon steels & low-alloy steels and austenitic stainless steels were developed. Design factors were investigated. Also, a Japanese utility collaborative project performed large scale fatigue tests using austenitic stainless steel piping and low-alloy steel flat plates as well as fatigue tests using small specimens to obtain not only basic data but also fatigue data of mean stress effect, surface finish effect and size effect. Those test results were provided to the subcommittee and utilized the above studies. Based on the above studies, a new fatigue evaluation method has been developed.

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