Development of Creep–Fatigue Evaluation Method for 316FR Stainless Steel

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Yuji Nagae ◽  
Shigeru Takaya ◽  
Tai Asayama
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Evaluation Method ◽  
Elevated Temperatures ◽  
Strain Curve ◽  
Creep Damage ◽  
Fatigue Curve ◽  
Time To Failure ◽  
Creep Fatigue ◽  
Fatigue Evaluation

In the design of fast reactor plants, the most important failure mode to be prevented is creep–fatigue damage at elevated temperatures. 316FR stainless steel is a candidate material for the reactor vessel and internal structures of such plants. The development of a procedure for evaluating creep–fatigue life is essential. The method for evaluating creep–fatigue life implemented in the Japan Society of Mechanical Engineers code is based on the time fraction rule for evaluating creep damage. Equations such as the fatigue curve, dynamic stress–strain curve, creep rupture curve, and creep strain curve are necessary for calculating creep–fatigue life. These equations are provided in this paper and the predicted creep–fatigue life for 316FR stainless steel is compared with experimental data. For the evaluation of creep–fatigue life, the longest time to failure is about 100,000 h. The creep–fatigue life is predicted to an accuracy that is within a factor of 2 even in the case with the longest time to failure. Furthermore, the proposed method is compared with the ductility exhaustion method to investigate whether the proposed method gives conservative predictions. Finally, a procedure based on the time fraction rule for the evaluation of creep–fatigue life is proposed for 316FR stainless steel.

Development of 2012 Edition of JSME Code for Design and Construction of Fast Reactors: (5) Creep-Fatigue Evaluation Method for 316FR Stainless Steel

2013 ◽  
Author(s):  
Yuji Nagae ◽  
Shigeru Takaya ◽  
Tai Asayama
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Evaluation Method ◽  
Elevated Temperatures ◽  
Strain Curve ◽  
Fatigue Curve ◽  
Creep Rupture ◽  
Time To Failure ◽  
Fast Reactors ◽  
Creep Fatigue

The most important failure mode to be prevented in the design is creep-fatigue at elevated temperatures in fast reactors. 316FR stainless steel is a candidate material for the reactor vessel and internal structures. Development of the procedure for evaluating creep-fatigue life is essential. The method for evaluating creep-fatigue life implemented in the Japan Society Mechanical Engineers code is based on the time fraction rule for austenitic stainless steel such as SUS304. Necessary equations such as fatigue curve and creep rupture curve for calculation of creep-fatigue life are evaluated, and the predicted creep-fatigue life by using the time fraction rule in 316FR stainless steel is compared with experimental data. The longest time to failure is about 100,000 h for evaluating creep-fatigue life. Fatigue curve, creep rupture curve, stress-strain curve and creep strain curve are provided for calculating creep-fatigue life. The creep-fatigue life is predicted within a factor of 2 even the test condition of the longest time to failure. Furthermore, comparison with the ductility exhaustion method was done to investigate the conservatism of the proposed method. Finally, the procedure based on the time fraction rule for evaluation of creep-fatigue life is proposed in 316FR stainless steel.

Evaluation Method of Creep-Fatigue Life for 316FR Weldment

2015 ◽  
Author(s):  
Yuji Nagae ◽  
Kenji Yamamoto ◽  
Tomomi Otani
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Fatigue Life ◽  
Base Metal ◽  
Evaluation Method ◽  
Elevated Temperatures ◽  
Reduction Factor ◽  
Strength Reduction ◽  
Strength Reduction Factor ◽  
Creep Fatigue

The most important failure mode to be prevented is creep-fatigue at elevated temperatures in fast reactors. 316FR stainless steel is a candidate material for the reactor vessel and internal structures. A method to evaluate creep-fatigue life, based on the time fraction rule, has been already developed in base metal of 316FR stainless steel. Development of procedure in evaluating creep-fatigue life is also necessary for the weldment of 316FR stainless steel by similar fillers or 16-8-2 fillers. Compared between mechanical properties of weldment and those of base metal, strength-reduction factors for weldment have been evaluated. Strength-reduction factor for fatigue has been proposed. It is considered that strength-reduction factor for creep strength is not necessary. Creepfatigue life could be evaluated in the same way for weldments of similar fillers and 16-8-2 fillers, because a difference in mechanical properties between both filler metals is negligible. Creep-fatigue life by the time fraction rule using analytical relaxation curve for weldments were compared with experimental data, and a method to evaluate creep-fatigue life for the weldments of 316FR stainless steel has been proposed.

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 Creep-Fatigue Evaluation Method for Modified 9Cr-1Mo Steel

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Shigeru Takaya ◽  
Yuji Nagae ◽  
Tai Asayama
Keyword(s):  
Evaluation Method ◽  
Time To Failure ◽  
Test Results ◽  
Design Factor ◽  
Design Procedures ◽  
Material Test ◽  
Creep Fatigue ◽  
Summation Rule ◽  
Fatigue Evaluation ◽  
Failure Life

This paper describes a creep–fatigue evaluation method for modified 9Cr-1Mo steel, which has been newly included in the 2012 edition of the Japan Society of Mechanical Engineers code for design and construction of fast reactors (JSME FRs code). 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. The conservativeness of this method without design factors was investigated using material test results, and it was shown 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 are hardly obtained. These results confirm that the creep–fatigue evaluation method in the JSME FRs code has implicit conservatism in addition to explicit margins in the design procedures such as design factor.

scholarly journals Creep and Fatigue at Elevated Temperatures. Study on Creep-Fatigue Life of Irradiated Austenitic Stainless Steel.

2002 ◽  
Vol 45 (1) ◽  
pp. 51-56
Author(s):  
Ikuo IOKA ◽  
Yukio MIWA ◽  
Hirokazu TSUJI ◽  
Minoru YONEKAWA ◽  
Fumiki TAKADA ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Austenitic Stainless Steel ◽  
Elevated Temperatures ◽  
Creep Fatigue

Fatigue and Creep-Fatigue Life Evaluation of U-Shaped Bellows

1992 ◽  
Vol 114 (3) ◽  
pp. 280-291 ◽  
Author(s):  
K. Tsukimori ◽  
T. Yamashita ◽  
M. Kikuchi ◽  
K. Iwata ◽  
A. Imazu
Keyword(s):  
Fatigue Life ◽  
Evaluation Method ◽  
Strain Range ◽  
Creep Damage ◽  
Fatigue Tests ◽  
Reliable Operation ◽  
Life Evaluation ◽  
Creep Fatigue ◽  
Fatigue Life Evaluation ◽  
Rational Evaluation

For the reliable operation of bellows under cyclic loadings at high temperatures, a rational evaluation method of life of bellows would be needed. Authors investigated simplified analysis methods for fatigue and creep-fatigue life prediction of U-shaped bellows considering inelasticity as well as various geometrical nonuniformity such as thickness and shape of convolutions. A conservative evaluation method of the strain range is developed, introducing three strain range amplification factors for nominal elastic strain range. Creep and relaxation behaviors of bellows are studied. Consequently, a new evaluation method of creep damage fractions is proposed which depends upon the relation between primary and secondary stresses. Fatigue and creep-fatigue tests are conducted and the validity of the present methods is discussed.

scholarly journals Some issues in creep-fatigue research

2021 ◽  
pp. 1-13
Author(s):  
Isamu Nonaka
Keyword(s):  
Fatigue Life ◽  
Elevated Temperatures ◽  
Creep Damage ◽  
Design Guidelines ◽  
Evaluation Procedures ◽  
Life Evaluation ◽  
Creep Fatigue ◽  
Fatigue Life Evaluation ◽  
Summation Rule ◽  
Loading Modes

In the component operated at elevated temperatures, the life evaluation should be made in consideration of both creep and fatigue (creep-fatigue) such as the linear damage summation rule. However, the concept of creep-fatigue life evaluation has not spread well in the industry. In order to consider the reason, a series of past creep-fatigue research was surveyed, namely experimental methods, life evaluation procedures and strength design guidelines. As a result, it was revealed that the mechanism of creep-fatigue interaction has not been fully clarified yet, which results in obscuring the necessity of creep-fatigue life evaluation. The necessity of creep-fatigue life evaluation was reviewed and consequently it proved to be necessary in two cases. One is the case where the creep-fatigue interaction is significant for some kinds of material, loading modes and temperatures. The other is one where the amount of creep damage is almost the same as that of fatigue damage even though the creep-fatigue interaction is insignificant.

Sign in / Sign up

Export Citation Format

Share Document