Influence of strain range on fatigue life reduction of stainless steel in PWR primary water

2017 ◽  
Vol 40 (12) ◽  
pp. 2194-2203 ◽  
Author(s):  
Masayuki Kamaya
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Strain Range ◽  
Primary Water ◽  
Fatigue Life Reduction

Mean Stress Effect on Fatigue Properties of Type 316 Stainless Steel: Part II — In PWR Primary Water Environment

2017 ◽  
Author(s):  
Masayuki Kamaya
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Effective Strain ◽  
Strain Range ◽  
Stress Effect ◽  
Mean Stress ◽  
316 Stainless Steel ◽  
Mean Stress Effect ◽  
Primary Water ◽  
The Mean

The mean stress effect on the fatigue life of Type 316 stainless steel was investigated at 325°C in simulated PWR primary water. It was shown that, as shown in high-temperature air environment, the fatigue life was extended by applying the mean stress under the same stress amplitude. An increase in the maximum peak stress by applying the mean stress induced additional plastic strain and this hardened the material. On the other hand, the fatigue life was shortened by the mean stress for the same strain range. The ratcheting strain caused by applying mean stress accelerated crack mouth opening and reduced fatigue life. It was also shown that the fatigue life in the simulated PWR primary water was shorter than that in air even without the mean stress. The magnitude of the reduction depended on the strain range. The reduction in fatigue life was the maximum when the strain range was 0.6%. The environmental effect disappeared when the effective strain was less than 0.4%.

Evaluation of Fatigue Damage in LWR Water With and Without Threshold and Moderation Factor

2003 ◽  
Author(s):  
Makoto Higuchi ◽  
Kazuya Tsutsumi ◽  
Katsumi Sakaguchi
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Stainless Steels ◽  
Power Plants ◽  
Light Water Reactor ◽  
Low Alloy Steels ◽  
Light Water ◽  
Water Reactor ◽  
Fatigue Data ◽  
Fatigue Life Reduction

During the past twenty years, the fatigue initiation life of LWR structural materials, carbon, low alloy and stainless steels has been shown to decrease remarkably in the simulated LWR (light water reactor) coolant environments. Several models for evaluating the effects of environment on fatigue life reduction have been developed based on published environmental fatigue data. Initially, based on Japanese fatigue data, Higuchi and Iida proposed a model for evaluating such effects quantitatively for carbon and low alloy steels in 1991. Thereafter, Chopra et al. proposed other models for carbon, low alloy and stainless steels by adding American fatigue data in 1993. Mehta developed a new model which features the threshold concept and moderation factor in Chopra’s model in 1995. All these models have undergone various revisions. In Japan, the MITI (Ministry of International Trade and Industry) guideline on environmental fatigue life reduction for carbon, low alloy and stainless steels was issued in September 2000, for evaluating of aged light water reactor power plants. The MITI guideline provide equations for calculations applicable only to stainless steel in PWR water and consequently Higuchi et al. proposed in 2002 a revised model for stainless steel which incorporates new equations for evaluation of environmental fatigue reduction in BWR water. The paper compares the latest versions of these models and discusses the conservativeness of the models by comparison of the models with available test data.

Improvement of Thermomechanical Fatigue Life in Nitrogen Alloyed 316 Stainless Steel

2005 ◽  
Vol 475-479 ◽  
pp. 1429-1432 ◽  
Author(s):  
Dae Whan Kim ◽  
Chang Hee Han ◽  
Woo Seog Ryu
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Temperature Change ◽  
Low Cycle Fatigue ◽  
Strain Range ◽  
Thermomechanical Fatigue ◽  
Fatigue Tests ◽  
Cycle Fatigue ◽  
Phase Condition ◽  
Higher Temperature

Fatigue tests of type 316 and 316LN stainless steel were conducted at RT and 600ı, 0.8~1.5% strain range for low cycle fatigue (LCF), 300~600ı, 0% strain range for thermal fatigue (TF) and 300~600ı, 2% strain range, in-phase or out-of-phase for thermomechanical fatigue (TMF). LCF, TF, and TMF lives were increased but saturation stresses were decreased with the addition of nitrogen. The higher temperature was the lower TF life at a same temperature change. The minimum temperature change for TF failure was more than 100ı. TMF life was higher at inphase condition than at out-of-phase condition. Fracture mode was transgranular for LCF and outof- phase of TMF and almost transgranular and small intergranular for TF and in-phase TMF.

Mean Stress Effect on Fatigue Properties of Type 316 Stainless Steel in Pressurized Water Reactors Primary Water Environment

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Masayuki Kamaya
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Water Environment ◽  
Stress Effect ◽  
Mean Stress ◽  
Pressurized Water ◽  
316 Stainless Steel ◽  
Mean Stress Effect ◽  
Primary Water ◽  
The Mean

The mean stress effect on the fatigue life of type 316 stainless steel was investigated in simulated pressurized water reactor (PWR) primary water and air at 325 °C. The tests in air environment have revealed that the fatigue life was increased with application of the positive mean stress for the same stress amplitude because the strain range was decreased by hardening of material caused by increased maximum peak stress. On the other hand, it has been shown that the fatigue life obtained in simulated PWR primary water was decreased compared with that obtained in air environment even without the mean stress. In this study, type 316 stainless steel specimens were subjected to the fatigue test with and without application of the positive mean stress in high-temperature air and PWR water environments. First, the mean stress effect was discussed for high-temperature air environment. Then, the change in fatigue life in the PWR water environment was evaluated. It was revealed that the change in the fatigue life due to application of the mean stress in the PWR water environment could be explained in the same way as for the air environment. No additional factor was induced by applying the mean stress in the PWR water environment.

A Proposal of Fatigue Life Correction Factor Fen for Austenitic Stainless Steels in LWR Water Environments

2002 ◽  
Author(s):  
Makoto Higuchi ◽  
Kunihiro Iida ◽  
Akihiko Hirano ◽  
Kazuya Tsutsumi ◽  
Katsumi Sakaguchi
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Stainless Steels ◽  
Austenitic Stainless Steels ◽  
Reduction Factor ◽  
New Models ◽  
Fatigue Data ◽  
Few Data ◽  
Fatigue Life Reduction ◽  
Remarkable Reduction

The fatigue life of austenitic stainless steel has recently been shown to undergo remarkable reduction with decrease in strain rate and increase in temperature in water. Either of these parameters as a factor of this reduction has been examined quantitatively and methods for predicting the fatigue life reduction factor Fen in any given set of conditions have been proposed. All these methods are based primarily on fatigue data in simulated PWR water owing to the few data available in simulated BWR water. Recent Japanese fatigue data in simulated BWR water clearly indicated the effects of the environment on fatigue degradation to be milder than under actual PWR conditions. A new method for determining Fen in BWR water was developed in the present study and a revised Fen in PWR water is also proposed based on new data. These new models differ from those previously used primarily with regard to the manner in which strain amplitude is considered to affect Fen in the environment.

Influence of PWR Environment on Fatigue Crack Initiation and Growth of Type 316 Stainless Steel

2015 ◽  
Author(s):  
Ryosuke Fujikawa ◽  
Shigeki Abe ◽  
Takao Nakamura ◽  
Masayuki Kamaya
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Crack Initiation ◽  
Environmental Effect ◽  
Monte Carlo Model ◽  
Fatigue Crack Initiation ◽  
Multiple Crack ◽  
316 Stainless Steel ◽  
Fatigue Life Reduction

This study was aimed at investigating the role of crack initiation and growth rate on the fatigue life reduction by environmental effect. First, crack length and the number of cracks were observed on the inner surface of specimens after fatigue test in PWR environment and air. Next, incubation time was deduced by inverse analysis. Third, statistical crack initiation and growth behavior was simulated by a Monte Carlo model. The influence of multiple crack interaction and coalescence to the fatigue life were discussed. It was revealed that environmental effect enhanced crack initiation and accelerated crack growth. Moreover, coalescence of cracks was estimated to influence fatigue life of 316 stainless steel in PWR environment.

Effects of Water Flow Rate on Fatigue Life of Ferritic and Austenitic Steels in Simulated LWR Environment

2002 ◽  
Author(s):  
Akihiko Hirano ◽  
Michiyoshi Yamamoto ◽  
Katsumi Sakaguchi ◽  
Tetsuo Shoji ◽  
Kunihiro Iida
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Carbon Steel ◽  
Water Flow ◽  
Flow Rate ◽  
Fatigue Testing ◽  
Water Flow Rate ◽  
High Water ◽  
Low Sulfur ◽  
Fatigue Life Reduction

The flow rate of water flowing over a steel surface is considered to be one of the most important factors influencing the fatigue life of the steel, because the water flow produces differences in the local environment. The effect of the water flow rate on the fatigue life of carbon, low alloy, and austenitic stainless steels was therefore investigated experimentally. Fatigue testing of low (S = 0.008 wt%) and high (S = 0.016 wt%) sulfur content carbon steels and a low alloy steel was performed at 289°C for various dissolved oxygen concentrations (DO) of less than 0.01 and 0.05, 0.2, and 1 ppm, and at various water flow rates. Three different strain rates of 0.4, 0.01, and 0.001%/s were used in the fatigue tests. For high sulfur carbon steel (S = 0.016 wt%), the effect of a high water flow rate on mitigating fatigue life reduction was more clearly observed at a lower strain rate, irrespective of the DO. This effect of high water flow rate was most notable at a DO of 0.2 ppm, which was the DO level that produced a significant sulfur effect. This indicates that the mechanism responsible for the mitigation of fatigue life reduction is the flushing effect of the water, which eliminates the locally corrosive environment. For high sulfur carbon steel (S = 0.016 wt%), no benefit of a high water flow rate was found at a DO of 0.01 ppm. This was because the environmental effect is insignificant at this low DO level. For low sulfur carbon steel (S = 0.008 wt%) and low alloy steel (S = 0.008 wt%), a high water flow rate had little effect on mitigating fatigue life reduction even at a DO of 0.2 ppm. This indicates that the sulfur is much less influential in low sulfur steel than in high sulfur steel. Fatigue testing of Type 316 nuclear grade stainless steel (316NG) and Type 316 stainless steel (SUS316) was performed at 289°C and 320°C for DO levels of less than 0.01 and 0.05, and 0.2. For austenitic stainless steel, no mitigating effect at a high water flow rate was found. It should be noted rather that there is a possibility that a high water flow rate decreases the fatigue life because a tendency to a slight decrease in fatigue life with an increasing flow rate was observed.

Influence of Mean Strain on Fatigue Life of Stainless Steel (Effect of Constant and Ratcheting Mean Strain)

2014 ◽  
Author(s):  
Masayuki Kamaya
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Effective Strain ◽  
Mouth Opening ◽  
Strain Range ◽  
Fatigue Tests ◽  
Mean Stress ◽  
Crack Mouth ◽  
The Mean ◽  
Mean Strain

The influence of mean strain on fatigue life was investigated for Type 316 stainless steel at room temperature in ambient environment. Two types of mean strain were simulated in the fatigue tests: constant and increasing (ratcheting) mean strains. In order to apply the constant mean strain, prestraining was induced prior to fatigue tests. Although the stress amplitudes became larger due to the prestraining, fatigue lives were almost the same as those obtained using non-prestrained specimens for the same strain range. Change in the maximum peak stress and stress amplitude due to the prestraining had little influence on the fatigue life. It was shown that the mean strain showed little influence on the fatigue life under the same strain range. The ratcheting mean strain was observed during the fatigue tests under mean stress. The fatigue life was reduced by applying the mean stress for the same strain range. The degree of the reduction was increased with the magnitude of the ratcheting mean strain. It was deduced that the increasing mean strain enhanced the crack mouth opening and increased the effective strain range. It was concluded that the ratcheting mean strain reduced the fatigue life for the same strain range, and the reduction in fatigue life could be predicted conservatively by assuming the crack mouth was never closed during the fatigue tests.

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