Influence of Load Ratio, Rise Time and Waveform on the Corrosion Fatigue Crack Growth of Austenitic Stainless Steel in a PWR Primary Coolant Environment

2007 ◽  
Author(s):  
Norman Platts ◽  
David Tice ◽  
Keith Rigby ◽  
John Stairmand
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Weld Metal ◽  
Crack Growth ◽  
Growth Rates ◽  
Rise Time ◽  
Load Ratio ◽  
Loading Frequency ◽  
Primary Coolant ◽  
Crack Growth Rates

The rate of growth of flaws in reactor circuit components by fatigue is usually determined using the reference crack growth curves in Section XI of the ASME Boiler and Pressure Vessel Code. These curves describe the rate of crack propagation per cycle (da/dN) as a function of the applied stress intensity factor range (ΔK). No reference curves for water-wetted defects in austenitic stainless steels are currently available. This paper describes the results of testing of austenitic stainless steel and weld metal in simulated PWR primary coolant over a range of temperatures and mechanical loading conditions. Previous data presented by the authors on wrought stainless steel demonstrated that crack growth rates can be significantly enhanced by the PWR primary environment at temperatures between 150°C and 300°C. The current study extends these data to weld metal and also investigates the impact of other loading waveforms (e.g. trapezoidal loading) on the degree of environmental enhancement. The environmental enhancement increases significantly with reducing loading frequency and decreases with decreasing water temperature. The environmental influence on fatigue is shown to be independent of load ratio over the range R = 0.1 to R = 0.8. The level of enhancement is frequently smaller at very high R ratio (≥0.85) with the enhanced rates of fatigue frequently being unsustained at these high load ratios. There is a strong correlation between the rise time and the level of enhancement of crack growth rate over inert crack growth rates at all temperatures tested. Weld metal has been shown to exhibit similar behavior to wrought material over the whole temperature range studied although the apparent rates of enhancement relative to average inert crack growth rates are lower than found for wrought material. For complex loading waveforms (e.g. trapezoidal loading with hold periods at maximum or minimum load) it is possible predict the level of enhancement on the basis of the test data generated using simpler saw tooth loading regimes.

Influence of PWR Primary Coolant Environment on Corrosion Fatigue Crack Growth of Austenitic Stainless Steel

2005 ◽  
Author(s):  
David Tice ◽  
Norman Platts ◽  
Keith Rigby ◽  
John Stairmand ◽  
David Swan
Keyword(s):  
Growth Rate ◽  
Stainless Steel ◽  
Crack Growth Rate ◽  
Crack Growth ◽  
Growth Rates ◽  
Environmental Influence ◽  
304L Stainless Steel ◽  
Loading Frequency ◽  
Primary Coolant ◽  
Crack Growth Rates

The rate of growth of flaws in reactor circuit components by fatigue is usually determined using the reference crack growth curves in Section XI of the ASME Boiler and Pressure Vessel Code. These curves describe the rate of crack propagation per cycle (da/dN) as a function of the applied stress intensity factor range (ΔK). No reference curves for water-wetted defects in austenitic stainless steels are currently available. This paper describes the results of testing of Type 304L stainless steel in simulated PWR primary coolant over a range of temperatures and mechanical loading conditions. The data on wrought stainless steel presented in this paper demonstrate that crack growth rates can be significantly enhanced by the PWR primary environment at temperatures between 150°C and 300°C. The degree of enhancement increases significantly with reducing loading frequency and decreases with decreasing water temperature. The environmental influence on fatigue is also smaller at very high R ratio (≥0.85). At long rise times the maximum enhancement of crack growth rate over inert crack growth rates was between 1 and 2 orders of magnitude at 250–300°C. However there is evidence that at very long rise times the environmental effect starts to decrease again. The conditions under which this occurs are influenced by temperature and water flowrate, with turbulent flow conditions appearing to have a limited beneficial effect. Due to the strong time dependence of crack growth rate, the data are best rationalized using a time domain (a˙e–a˙i) approach.

Cyclic Crack Growth Rate of Irradiated Austenitic Stainless Steel Welds in Simulated BWR Environment

2011 ◽  
Author(s):  
Y. Chen ◽  
B. Alexandreanu ◽  
W. J. Shack ◽  
K. Natesan ◽  
A. S. Rao
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Crack Growth ◽  
Neutron Irradiation ◽  
Growth Rates ◽  
Reactor Core ◽  
Cracking Behavior ◽  
Steel Welds ◽  
The Impact ◽  
Crack Growth Rates

Reactor core internal components in light water reactors are subjected to neutron irradiation. It has been shown that the austenitic stainless steels used in reactor core internals are susceptible to stress corrosion cracking after extended neutron exposure. This form of material degradation is a complex phenomenon that involves concomitant conditions of irradiation, stress, and corrosion. Interacting with fatigue damage, irradiation-enhanced environmental effects could also contribute to cyclic crack growth. In this paper, the effects of neutron irradiation on cyclic cracking behavior were investigated for austenitic stainless steel welds. Post-irradiation cracking growth tests were performed on weld heat-affected zone specimens in a simulated boiling water reactor environment, and cyclic crack growth rates were obtained at two doses. Environmentally enhanced cracking was readily established in irradiated specimens. Crack growth rates of irradiated specimens were significantly higher than those of nonirradiated specimens. The impact of neutron irradiation on environmentally enhanced cyclic cracking behavior is discussed for different load ratios.

scholarly journals Stress Corrosion Crack Growth Rates in Type 304 Stainless Steel in Simulated BWR Environments

1986 ◽  
Vol 108 (1) ◽  
pp. 20-25 ◽  
Author(s):  
J. Y. Park ◽  
W. E. Ruther ◽  
T. F. Kassner ◽  
W. J. Shack
Keyword(s):  
Growth Rate ◽  
Stainless Steel ◽  
Dissolved Oxygen ◽  
Crack Growth ◽  
Growth Rates ◽  
Load Ratio ◽  
304 Stainless Steel ◽  
Type 304 ◽  
Type 304 Stainless Steel ◽  
Crack Growth Rates

Stress corrosion cracking of Type 304 stainless steel has been studied with fracture-mechanics-type standard 25.4-mm-thick compact tension specimens in simulated boiling-water reactor environments at 289°C and 8.3 MPa. Tests were performed with either constant or cyclic loading. The latter tests used a positive sawtooth waveform with an unloading time of 1 or 5 s, a load ratio R (minimum load to maximum load) of 0.2 to 0.95, and a frequency f of 8 × 10−4 to 1 × 10−1 Hz. Crack lengths and crack growth rates were determined by the compliance method; crack mouth opening displacement was measured with in-situ clip gauges. Fractography was used to examine the mode of cracking and to confirm the compliance method for crack length determination. The test environments were high-purity deionized water with 0.2- to 8-ppm dissolved oxygen, and water with 0.2-ppm dissolved oxygen and 0.1-ppm sulfate (as H2SO4). Two heats with a carbon content of 0.06 wt percent were investigated in solution-heat-treated and furnace-sensitized conditions. Degree of sensitization varied from ∼0 to 20 C/cm2 as measured by the electrochemical potentiokinetic polarization method. The first heat was tested in water with 0.2- and 8-ppm dissolved oxygen and with 0.2-ppm dissolved oxygen and 0.1-ppm sulfate. The loading conditions encompassed the range f=8×10−2 to 8 × 10−4 Hz, Kmax=28 to 72 MPa•m1/2, and R = 0.95. Under these conditions, the crack growth rates were ∼0 to 3 × 10−9 m/s. The effects of water chemistry transients which produced changes in the concentration of dissolved oxygen or sulfate in the environment were also investigated. The second heat was tested in water with 8-ppm dissolved oxygen. The influence of load ratio and frequency was investigated over the range R = 0.5 to 1.0 and f = 1 × 10−1 to 2 × 10−3 Hz, at maximum stress intensity Kmax = 28 to 38 MPa•m1/2. Under these conditions, crack growth rates varied from 1 × 10−10 to 3 × 10−9 m/s. Crack growth rate increased significantly at low R values. However, the growth rate at R = 0.95 was not significantly different from that under constant load. Correlation of the crack growth rate data with crack-tip strain rates is discussed.

Crack Growth in Stainless Steel 304 under Creep-Fatigue Loading

2007 ◽  
Vol 353-358 ◽  
pp. 485-490 ◽  
Author(s):  
Y.M. Baik ◽  
K.S. Kim
Keyword(s):  
Stress Intensity Factor ◽  
Stainless Steel ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Growth ◽  
Growth Rates ◽  
Static Loading ◽  
Fatigue Loading ◽  
Creep Fatigue ◽  
Crack Growth Rates

Crack growth in compact specimens of type 304 stainless steel is studied at 538oC. Loading conditions include pure fatigue loading, static loading and fatigue loading with hold time. Crack growth rates are correlated with the stress intensity factor. A finite element analysis is performed to understand the crack tip field under creep-fatigue loading. It is found that fatigue loading interrupts stress relaxation around the crack tip and cause stress reinstatement, thereby accelerating crack growth compared with pure static loading. An effort is made to model crack growth rates under combined influence of creep and fatigue loading. The correlation with the stress intensity factor is found better when da/dt is used instead of da/dN. Both the linear summation rule and the dominant damage rule overestimate crack growth rates under creep-fatigue loading. A model is proposed to better correlate crack growth rates under creep-fatigue loading: 1 c f da da da dt dt dt Ψ −Ψ     =         , where Ψ is an exponent determined from damage under pure fatigue loading and pure creep loading. This model correlates crack growth rates for relatively small loads and low stress intensity factors. However, correlation becomes poor as the crack growth rate becomes large under a high level of load.

Fatigue Crack Growth in Type 316 Stainless Steel at High Temperature

1971 ◽  
Vol 93 (4) ◽  
pp. 976-980 ◽  
Author(s):  
P. Shahinian ◽  
H. H. Smith ◽  
H. E. Watson
Keyword(s):  
Growth Rate ◽  
Stainless Steel ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Rates ◽  
316 Stainless Steel ◽  
Arrhenius Relation ◽  
Crack Growth Rates

The dependence of fatigue crack growth rates on range of stress intensity factor (ΔK) in Type 316 stainless steel was investigated over the temperature range of 75 to 1100 deg F. The data for the most part could be described by a power law relationship. An increase in temperature generally increased crack growth rate for a given ΔK and decreased fatigue life. The dependence of crack growth rate on temperature is not described adequately by an Arrhenius relation over the range investigated. On the other hand, by normalizing ΔK with respect to Young’s modulus, E, the crack growth rates for the various temperatures tend to fall within a single band.

Sign in / Sign up

Export Citation Format

Share Document