• Journal of Ocean Engineering and Technology
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• v.1 no.2
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• pp.93-100
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• 1987

Corrosion fatigue cracking of the austenitic stainless steel(bese metal & heat affected zone by TIG weld) was studied experimentally under the environments of various specific resistance and air. The characteristics of corrosion fatigue crack growth rate and the environmental constants of paris' rule were investigated for SUS 304 weldments in the various specific resistance. The influences of stress intensity factor range and corrosion on the crack growth rate were compared. The characteristics of corrosion fatigue cracking for the weldments were inspected from mechanical, electrochemical and microstructural point of view. Main results obtained are as follows: 1) As the specific resistance decreases, the environmental constant C of paris'rule increases(hence the corrosion fatigue crack growth rate is rapid), but the environmental constant m decreases, so the effect of corrosion to the crack growth rate is more susceptible than thet of stress intensity factor range. 2) As the stress intensity factor range decreases, the corrosion fatigue crack growth rate of heat affected zone is more susceptible than that of the base metal. 3) The corrosion fatigue crack growth rate of the heat affected zone is more rapid than that of the base metal, because of the phenomenon of softening and the less noble potential coused by wedlding heat cycle. 4) The corrosion fatigue cracking of SUS 304 weldment appears transgranular fracture.

• Journal of the korean Society of Automotive Engineers
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• v.5 no.1
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• pp.32-44
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• 1983

In case of $K_{Imax}$ < $K_{Iscc}$, the corrosion fatigue of high strength steel in 0.1N $H_{2}$S $O_{4}$ solution and 3.5% salt water is as follows. 1. The fatigue life shortens in order of 3.5% salt water and 0.1N $H_{2}$S $o_{4}$ solution. 2. The fatigue crack growth rate in air is obtained as the following equation. (dc/dN)$_{atr}$=7.23*10$^{-6}$ (.DELTA. K)$^{2.23}$ 3. The corrosion fatigue crack growth rate in environment is divided into three regions, that is, First Region, Second Region and Third Region from the small cyclic stress intensity. 4. The formation rate of the active surface on metal is slower than the mechano-chemical reaction rate in First Region. The crack growth rate depends on time and the cyclic stress intensity and is expressed as the following equation. (dc/dN)$_{I}$=C(/DELTA. K)$^{\delta}$ 5. The formation rate of the active surface is faster than the mechano-chemical reaction rate in Second Region and the synergistic effect by stress and corrosion becomes slow. In case the fatigue load is large, we have the critical crack growth rate which is not related to the cyclic stress intensity. 6. The corrosion crack growth rate by the mechano-chemical reaction is the same in $H_{2}$S $O_{4}$ solution and salt water, so Hydrogen accelerates the crack growth. 7. The environment has no effect on the corrosion fatigue crack growth rate in Third Region. 8. In First Region and Second Region, dimple is observed on the fatigue fracture surface in 0.1N $H_{2}$S $O_{4}$ solution. 9. The striation is observed in any environment as in air in Third Region and its interval approximately coincide with the crack growth rate.ate.e.e.

• Journal of the Korean Society of Safety
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• v.16 no.4
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• pp.52-57
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• 2001

Fatigue crack growth behaviour of Ti-6A-4V alloy is investigated in air and salt solution environment at room temperature and $200^{\circ}C$. Fatigue crack growth rate is blown to be fast for the formation of corrosive product in hot salt environment. For the effect on corrosion fatigue crack growth behaviour of region II. fatigue crack growth rate in atmosphere had a little gap to both case, $200^{\circ}C$ and room temperature. However, it showed very fast tendency in salt corrosive atmosphere, and it was remarkably accelerated in $200^{\circ}C$ temperature salt environment. When $\Delta$K was approximately 30MPa(equation omitted), fatigue crack growth rate had a little difference between at room temperature and at $200^{\circ}C$ high temperature, however in case of salt corrosive environment the room temperature was 3.5 times Inter and $200^{\circ}C$ high temperature for 16 times than air environment respectively.

• Journal of the korean Society of Automotive Engineers
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• v.8 no.1
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• pp.40-51
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• 1986

A study has been made of the corrosion fatigue of high strength low alloy steel in 3.5% NaCl solution under tension stress for solution temperature being 25.deg. C, 55.deg. C and 85 .deg. C. The main results obtained are as follows; 1) The corrosion fatigue crack growth rate curve could be divided into the First Region, the Second Region and the Third Region. 2) The corrosion fatigue crack growth rates in the First Region and the Second Region were Arrhenius temperature-dependent in this test range. The apparent activation energies for the corrosion fatigue cack growth rate were found to be 2000cal/mol in the First Region and 3700 cal/mol in the Second Region. 3) Hematite (Fe$_{2}$O$_{3}$) as the hexahedral crystal and magnetite (Fe$_{3}$O$_{4}$) as the octahedral crystal were observed in the corrosion products on the corrosion fatigue fracture surface at 85.deg. C and the anode fusion seem to be generated in the crack tip region at high temperature. 4) The complex environment effect ratio which was defined by the ratio of fatigue crack growth rate in corrosion environment to that in air might be considered not only a criterion estimating the effect of environment quantitatively but also an important parameter in the selection of the design stress for the fail safe design. The complex environment effect was not greater than ten in this test.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.11a
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• pp.228-229
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• 2005

The compressive residual stress, which is induced by shot peening process, has the effect of increasing the intrinsic fatigue strength of surface and therefore would be beneficial in reducing the probability of fatigue damage. However, it was not known that the effect of shot peening in corrosion environment. In this study, the effect of shot peening on corrosion fatigue crack growth of sping steel immersed in 6% $FeCl_3$ solution and corrosion characteristics with considering fracture mechanics. The results of the experimental study corrosion fatigue characteristics of spring steel are as follows; the fatigue crack growth rate of the shot peening material was lower than of the un peening material. And fatigue life shows more improvement in the shot peening material than un peening material. This is because the compressive residual stress of surface operate resistance of corrosion fatigue crack propagation. It is assumed that the shot peening process improve corrosive resistance and mechanical property.

• Corrosion Science and Technology
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• v.2 no.2
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• pp.93-97
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• 2003

Fatigue crack growth test or low alloy steel was performed in high temperature water. Test parameters were dissolved oxygen content. loading frequency and R-ratio ($P_{min}/P_{max}$). Since the sulfur content or the steel was low, there were no environmentally assisted cracks (EAC) in low dissolved oxygen(DO) water. At high DO, the crack growth rate at R = 0.5 tests was much increased due to environmental effects and the crack growth rate depended on loading frequency and maximized at a critical frequency. On the other hand, R = 0.7 test results showed an anomalous decrease of the crack growth rate as much different behavior from the R = 0.5. The main reason of the decrease may be related to the crack tip closure effect. All the data could be qualitatively understood by effects of oxide rupture and anion activity at crack tip.

• Journal of Ocean Engineering and Technology
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• v.2 no.2
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• pp.122-129
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• 1988

Recently with the rapid development in marine and shipbuliding industries such as marine structures, ship and chemical plants, there occurs much interest in the study of corrosion fatigue characteristics which was closed up an important role in mechanical design. In this study, the 5086 Al-alloy was tested by use of rotary bending fatigue tester. The retardation effect of overload on the corrosion fatigue crack propagation in sea environment was quantitatively studied. 1) Retardation effect of corrosion fatigue crack propagation is most eminent when overload ratio is 1.52, overload magnitude corresponds to about 77% and 55% of yield strength and tensile strength respectively. 2) After overload ratio 1.52 was used, retardation of corrosion fatigue crack growth rate is largely retarded and quasi-threshold stress intensity factor range($\Delta\textrm{K}_{th}$) appears. 3) According to m of experimental constant, retardation effect of corrosion fatigue crack propagation corresponds to about 25% of constant stress amplitude when overload ratio is 1.52. 4) When overload ratio 1.52 was used, retardation parameter (RP) decreases to about 0.43 and corrosion sensitivity (S)decreses to about 2.1.

• Nuclear Engineering and Technology
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• v.53 no.1
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• pp.304-313
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• 2021

Nickel base Alloy X-750, which is used as fastener parts in light-water reactor (LWR), has experienced many failures by environmentally assisted cracking (EAC). In order to improve the reliability of passive components for nuclear power plants (NPP's), it is necessary to study the failure mechanism and to predict crack growth behavior by developing a probabilistic failure model. In this study, The Bayesian inference was employed to reduce the uncertainties contained in EAC modeling parameters that have been established from experiments with Alloy X-750. Corrosion fatigue crack growth rate model (FCGR) was developed by fitting into Paris' Law of measured data from the several fatigue tests conducted either in constant load or constant ΔK mode. These parameters characterizing the corrosion fatigue crack growth behavior of X-750 were successfully updated to reduce the uncertainty in the model by using the Bayesian inference method. It is demonstrated that probabilistic failure models for passive components can be developed by updating a laboratory model with field-inspection data, when crack growth rates (CGRs) are low and multiple inspections can be made prior to the component failure.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.3
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• pp.88-94
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• 2006

The compressive residual stress, which is induced by shot peening process, has the effect of increasing the intrinsic fatigue strength of surface and therefore would be beneficial in reducing the probability of fatigue damage. However, the effect of shot peening in corrosion environment was not known. In this study, investigated is the effect of shot peening on corrosion fatigue crack growth of SAE 5155 steel immersed in 6% $FeCl_3$ solution and corrosion characteristics with considering fracture mechanics. The results of the experimental study corrosion fatigue characteristics of SAE 5155 are as follows; the fatigue crack growth rate of the shot peening material was lower than that of the non-peening material. And fatigue life shows more improvement in the shot peening material than in non-peening material. This is due to the compressive residual stress of surface increases resistance of corrosion fatigue crack propagation. It is assumed that the shot peening process improve corrosive resistance and mechanical property.

• Journal of Welding and Joining
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• v.6 no.2
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• pp.56-63
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• 1988

The effects of PWHT (poste weld heat treatment) and stress simulating the residual stress during PWHT in weld HAZ of low and high strength steels on corrosion fatigue crack growth were evaluated. The obtained results are summarized as follows. 1. Fatigue crack growth rate of HAZ in air and 3.5% NaCl solution was slower than that of parent due to the signgularity in weld HAZ. 2. In the case of HT-80, 3.5% NaCl solutio nacts to accelerate the crack growth for all specimens, and the sensitivity of as-weld to corrosion environment was the greatest among other PWHT specimens. 3. Corrosion fatigue crack growth of parent, as-weld and PWHT speciments ofr SS41 as well as SM53B was retarded in comparison with the fatigue crack growth in air. 4. There was a tendency that crack growth of PWHT specimens subjected $10kg/mm^2$ was faster than that of PWHT specimens without stress during PWHT. 5. The retardation phenomenon of crack growth in corrosion environment is attributed to the crack branching decreased .DELTA.K due to the corrosion products and multi-cracks.