scholarly journals Effects of LWR Coolant Environments on Fatigue Lives of Austenitic Stainless Steels

1998 ◽  
Vol 120 (2) ◽  
pp. 116-121 ◽  
Author(s):  
O. K. Chopra ◽  
D. J. Gavenda
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Statistical Model ◽  
Stainless Steels ◽  
Type Strain ◽  
Fatigue Cracks ◽  
Austenitic Stainless Steels ◽  
Strain Range ◽  
Fatigue Tests ◽  
Ferritic Steels

Fatigue tests have been conducted on Types 304 and 316NG stainless steels to evaluate the effects of various material and loading variables, e.g., steel type, strain rate, dissolved oxygen (DO) in water, and strain range, on the fatigue lives of these steels. The results confirm significant decreases in fatigue life in water. Unlike the situation with ferritic steels, environmental effects on Types 304 and 316NG stainless steel are more pronounced in low-DO than in high-DO water. Experimental results have been compared with estimates of fatigue life based on a statistical model. The formation and growth of fatigue cracks in air and water environments are discussed.

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.

scholarly journals Mechanism of Fatigue Crack Initiation in Austenitic Stainless Steels in LWR Environments

2002 ◽  
Author(s):  
Omesh K. Chopra
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
Stainless Steels ◽  
Fatigue Cracks ◽  
Fatigue Crack Initiation ◽  
Austenitic Stainless Steels ◽  
Fracture Morphology ◽  
Fatigue Tests ◽  
Temperature Level ◽  
Metallographic Examination

This paper examines the mechanism of fatigue crack initiation in austenitic stainless steels (SSs) in light water reactor (LWR) coolant environments. The effects of key material and loading variables, such as strain amplitude, strain rate, temperature, level of dissolved oxygen in water, and material heat treatment on the fatigue lives of wrought and cast austenitic SSs in air and LWR environments have been evaluated. The influence of reactor coolant environments on the formation and growth of fatigue cracks in polished smooth SS specimens is discussed. Crack length as a function of fatigue cycles was determined in air and LWR environments. The results indicate that decreased fatigue lives of these steels are caused primarily by the effects of the environment on the growth of cracks <200 μm and, to a lesser extent, on enhanced growth rates of longer cracks. A detailed metallographic examination of fatigue test specimens was performed to characterize the fracture morphology. Exploratory fatigue tests were conducted to enhance our understanding of the effects of surface micropits or minor differences in the surface oxide on fatigue crack initiation.

Low-Cycle Fatigue Behavior of TP347H Austenitic Stainless Steels at Room Temperature

2013 ◽  
Vol 815 ◽  
pp. 875-879 ◽  
Author(s):  
Hong Wei Zhou ◽  
Yi Zhu He ◽  
Yu Wan Cen ◽  
Jian Qing Jiang
Keyword(s):  
Fatigue Life ◽  
Stainless Steels ◽  
Room Temperature ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Austenitic Stainless Steels ◽  
Fracture Morphology ◽  
Cycle Fatigue ◽  
Response Curves

Low-cycle fatigue (LCF) tests were performed with different strain amplitudes from 0.4% to 1.2% at room temperature (RT) to investigate fatigue life and fracture morphology of TP347H austenitic stainless steels. The results show that there is initial cyclic hardening for a few cycles, followed by continuous softening until fatigue failure at all strain amplitudes in stress response curves. The fatigue life of the steels follows the strain-life Coffin-Manson law. Fracture morphology shows that fatigue cracks initiate from the specimen free surface instead of the interior of the specimen, and ductile fracture appears during LCF loading. More sites of crack initiation and quicker propagation rate of fatigue crack at high strain amplitudes than those at low strain amplitudes are responsible for reduced fatigue life with the increasing of strain amplitude.

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.

scholarly journals Hydrogen Effects on Fatigue Life of Welded Austenitic Stainless Steels Evaluated With Hole-Drilled Tubular Specimens

2020 ◽  
Author(s):  
B. Kagay ◽  
C. San Marchi ◽  
V. Pericoli ◽  
J. Foulk
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Stress Concentration ◽  
Stainless Steels ◽  
Fatigue Crack Initiation ◽  
Austenitic Stainless Steels ◽  
Internal Hydrogen ◽  
Weld Fatigue ◽  
Crack Initiation Life ◽  
Tubular Specimens

Abstract Limited fatigue data exists for small-volume welded austenitic stainless steel components typically employed in hydrogen infrastructure due to the difficulty of testing these components with conventional specimen designs. To assess the fatigue performance of orbital tube welds of austenitic stainless steels, a hole-drilled tubular specimen was designed to produce a stress concentration in the center of the orbital weld. Fatigue life testing was performed on welded and non-welded 316L stainless steel hole-drilled tubular specimens, and the effects of hydrogen were evaluated by testing specimens with no added hydrogen and with internal hydrogen introduced through gaseous precharging. When accounting for the differences in flow stress caused by microstructural variations and the presence of internal hydrogen, the total fatigue life and fatigue crack initiation life of the welded and non-welded tubes were comparable and were reduced by internal hydrogen. In addition, the fatigue life results produced with the hole drilled tubular specimens were consistent with fatigue life data from circumferentially notched stainless steel specimens that have a similar elastic stress concentration factor. To better understand the mechanics of this specimen geometry, mechanics modeling was performed to compare the stress and strain distributions that develop at the stress concentration in the hole-drilled tubular and circumferentially notched specimens during fatigue cycling.

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.

scholarly journals Comparison of Internal and External Hydrogen on Fatigue-Life of Austenitic Stainless Steels

2016 ◽  
Author(s):  
Paul J. Gibbs ◽  
Chris San Marchi ◽  
Kevin A. Nibur ◽  
Xiaoli Tang
Keyword(s):  
Fatigue Life ◽  
Stainless Steels ◽  
Life Stress ◽  
Maximum Stress ◽  
Austenitic Stainless Steels ◽  
Fatigue Tests ◽  
Gaseous Hydrogen ◽  
Fatigue Performance ◽  
Notched Specimens ◽  
Internal Hydrogen

The degradation of stress-controlled fatigue-life (stress-life) of notched specimens was measured in the presence of internal and in external hydrogen for two strain-hardened austenitic stainless steels: 316L and 21Cr-6Ni-9Mn. To assess the sensitivity of fatigue performance to various hydrogen conditions fatigue tests were performed in four environments: (1) in air with no added hydrogen, (2) in air after hydrogen pre-charging to saturate the steel with internal hydrogen, and in external gaseous hydrogen at pressure of (3)10 MPa (1.45 ksi), or (4) 103 MPa (15 ksi). The fatigue performance of the strain-hardened 316L and 21Cr-6Ni-9Mn steels in air was indistinguishable for the tested conditions. Decreases in the fatigue-life at a given stress level were measured in the presence of hydrogen and depended on the hydrogen environment. Testing in 103 MPa (15 ksi) external gaseous hydrogen always resulted in a clear decrease in the fatigue-life at a given maximum stress. Alloy dependent reductions in the observed life at a given maximum stress were observed in the presence of internal hydrogen or in gaseous hydrogen at a pressure of 10 MPa (1.45 ksi). The measured fatigue-life of hydrogen pre-charged specimens was comparable to the life with no intentional hydrogen additions. Accounting for the increased flow stress resulting from the supersaturation of hydrogen after pre-charging results in consistency between the measured fatigue-life of the pre-charged condition and measurements in 103 MPa (15 ksi) external hydrogen. The current results indicate that internal hydrogen may be an efficient method to infer hydrogen-assisted fatigue degradation of stainless steels in high-pressure gaseous hydrogen.

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

2003 ◽  
Vol 125 (4) ◽  
pp. 403-410 ◽  
Author(s):  
Makoto Higuchi ◽  
Kazuya Tsutsumi ◽  
Akihiko Hirano ◽  
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.

ALZ 316

Alloy Digest ◽  
1999 ◽  
Vol 48 (8) ◽  
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Corrosion Resistance ◽  
Austenitic Stainless Steel ◽  
Physical Properties ◽  
Tensile Properties ◽  
Stainless Steels ◽  
Austenitic Stainless Steels ◽  
Heat Treating

Abstract ALZ 316 is an austenitic stainless steel with good formability, corrosion resistance, toughness, and mechanical properties. It is the basic grade of the stainless steels, containing 2 to 3% molybdenum. After the 304 series, the molybdenum-containing stainless steels are the most widely used austenitic stainless steels. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, and joining. Filing Code: SS-756. Producer or source: ALZ nv.

ALLOY 0Cr25Ni6Mo3CuN

Alloy Digest ◽  
1998 ◽  
Vol 47 (2) ◽  
Keyword(s):  
Fracture Toughness ◽  
Stainless Steel ◽  
Corrosion Resistance ◽  
High Temperature ◽  
Physical Properties ◽  
Stainless Steels ◽  
Austenitic Stainless Steels ◽  
Temperature Performance ◽  
Steel Research ◽  
Oil Refinement

Abstract ALLOY 0Cr25Ni6Mo3CuN is one of four grades of duplex stainless steel that were developed and have found wide applications in China since 1980. In oil refinement and the petrochemical processing industries, they have substituted for austenitic stainless steels in many types of equipment, valves, and pump parts. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness. It also includes information on low and high temperature performance, and corrosion resistance as well as forming and joining. Filing Code: SS-706. Producer or source: Central Iron & Steel Research Institute.

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