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.

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.

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.

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

Effect of Loading on Stress Intensification Factors

2005 ◽  
Vol 128 (1) ◽  
pp. 33-38
Author(s):  
Rudolph J. Scavuzzo
Keyword(s):  
Fatigue Life ◽  
Evaluation Method ◽  
Fatigue Testing ◽  
Plastic Material ◽  
Strain Curve ◽  
Correct Prediction ◽  
Piping System ◽  
Testing Methods ◽  
Strain Cycle ◽  
Perfectly Plastic

The basic objective of this investigation is to determine the effect of loading on the stress intensification factors of Markl’s fatigue evaluation method for metal piping. Markl’s method is based on the fatigue testing of 4 in. schedule 40 carbon steel cantilever piping. Subsequent testing using a four-point loading showed that the S-N data were different from that predicted by the procedure and equation developed by Markl. Markl’s method is based on determining the elastic-plastic forces in a piping system by multiplying the elastic system stiffness by the actual deflection. In this manner a fictitious force is calculated to determine piping stresses assuming the elastic beam bending equation, Mc/I, applies even in partially plastic pipes. Previous analytical work on this topic by Rodabaugh and Scavuzzo (“Fatigue of Butt Welded Pipe and the Effect of Testing Methods–Report 2: Effect of Testing Methods on Stress Intensification Factors,” Welding Research Bulletin 433, July 1998) showed that these measured differences should occur between cantilever and four-point tests using Markl’s method. The basic assumption in this analytical comparison is that strain-cycle correlations lead to the correct prediction of fatigue life. Using the measured alternating strain, both types of test geometries lead to the same prediction of fatigue life using these strain-cycle correlations. In this study, the same analytical assumptions used by Rodabaugh and Scavuzzo (above) are applied to a pipe where the load is varied from a four-point loading through its extremes. Loads were varied from a cantilever to an end moment by changing the dimensions of four-point loading. Also, the shape of a bilinear stress-strain curve was varied from a perfectly plastic material to various degrees of work hardening by increasing the tangent modulus in the plastic regime. The results of the study indicate that Markl’s method is conservative by predicting too short a fatigue life for four-point loading for a given stress. As indicated by this study, the differences can be very large in the low-cycle regime for a perfectly plastic material and for a four-point loading approaching an end moment. Thus, piping could be over designed with unnecessary conservatism using the current ASME Code method based on stress intensification factors.

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.

Evaluation of Creep-Fatigue Life Prediction Methods for Low-Carbon Nitrogen-Added 316 Stainless Steel

1998 ◽  
Vol 120 (2) ◽  
pp. 119-125 ◽  
Author(s):  
Yukio Takahashi
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Life Prediction ◽  
Fatigue Life Prediction ◽  
Prediction Methods ◽  
Secondary Creep ◽  
Low Carbon ◽  
316 Stainless Steel ◽  
Creep Fatigue ◽  
Exhaustion Method

Low-carbon, medium-nitrogen 316 stainless steel is a principal candidate for a main structural material of a demonstration fast breeder reactor plant in Japan. A number of long-term creep tests and creep-fatigue tests have been conducting for two heats of the steel. Two representative creep-fatigue life prediction methods, i.e., time fraction rule and ductility exhaustion method were applied. An introduction of a simple viscous strain term improved the description of stress relaxation behavior and only the conventional (primary plus secondary) creep strain was assumed to contribute to creep damage in the ductility exhaustion method. The present ductility exhaustion approach was found to have very good accuracy in creep-fatigue life prediction, while the time fraction rule overpredicted failure life as large as a factor of 30.

Sign in / Sign up

Export Citation Format

Share Document