• Journal of the Society of Naval Architects of Korea
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• v.44 no.4
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• pp.417-424
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• 2007

With regard to corrosion fatigue crack initiation life (Nc), it has been treated ambiguously for the member which doesn't have stress concentration area. In this research, in order to clarify the corrosion fatigue crack initiation life (Nc), corrosion fatigue tests were carried out. Reasonable and universal corrosion fatigue crack initiation life (Nc) was defined and corrosion fatigue crack initiation/propagation model was suggested also. As the fatigue crack which emanates from the pit is usually small, accordingly it is treated as a small crack. In addition, the observation of the corrosion fatigue fracture surfaces using SEM was conducted. And the fracture mechanics analysis using an intrinsic crack model was conducted for the treatment of the small crack. Finally, the followings were obtained. When there is no clear stress concentration point which seems to fall into a corrosion fatigue crack initiation life, the significance of the definition and suggestion of the moment of the reasonable and universal corrosion fatigue crack initiation life (Nc), at which the fatigue crack propagation rate becomes faster than the corrosion pit growth rate so that the fatigue crack initiates from the pit and propagates in earnest, has been clarified.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.6
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• pp.732-738
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• 2004

One of the main degradation mechanisms in steam generator tubes is stress corrosion cracking induced by residual stress. The resulting damages can cause tube bursting or leakage of the primary water which contains radioactivity. Shot peening technique has been used to prevent stress corrosion crack growth in steam generator tubes. In order to investigate the shot peening effect on stress corrosion cracking stress intensity factors are calculated for the semi-elliptical surface crack which is located in residual stress region. The residual stress distribution in steam generator tubes is obtained from the simple model proposed by Frederick et al.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.141.1-141.1
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• 2005

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.5
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• pp.772-778
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• 2001

In this study, corrosion fatigue characteristics of 12Cr alloy steel were investigated in 3.5wt.% NaCl solution of 150$^{\circ}C$ and 4.5bar. Behavior of corrosion fatigue cracks was measured by the indirect compliance method and compared with the results in distilled water and in air. 1) 12Cr alloy steel was susceptible to temperature. Its susceptibility was increased as the temperature was increased. 2) The crack growth characteristics of 12Cr alloy steel in distilled water were similar to 3.5wt.% NaCl solution. 3) The temperature of solution affects to the crack growth characteristics of 12Cr alloy steel. In corrosion solutions of 4.5bar, 150$^{\circ}C$, fracture surfaces of corrosion fatigue crack growth at a/W=0.3 was showed the trans-granular fracture suface. As the crack grew up, it was changed to inter-granular type. In condition of high temperature, The crack growth behaviors of 12Cr alloy steel were remarkable.

• Journal of the Korean Society of Safety
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• v.32 no.6
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• pp.1-8
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• 2017

P-PIE is a program developed to estimate failure probability of pipes and pressure vessels considering fatigue and stress corrosion crack growth. Using the program, crack growth simulation was performed with an initially existing crack in order to examine the effects of initial crack depth distribution on the leak probability of pipes. In the simulation stress corrosion crack growth was considered and several crack depth distribution models were used. From the results it was found that the initial crack depth distribution gives great effect on the leak probability of pipes. The log-normal distribution proposed by Khaleel and Simonen gives lower leak probability compared other exponential distribution models. The effects of the number and the quality of pre-service and in-service inspections on the leak probability were also examined and it was recognized that the number and the quality of pre-service and in-service inspections are also give great effect on the leak probability. In order to reduce the leak probability of pipes in plants it is very important to improve the quality of inspections. When in-service inspection is performed every 10 years and the quality of inspection is above the very good level, the leak probability shows nearly constant value after the first inspection for an initially existing crack.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.24 no.2
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• pp.94-100
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• 1988

Recently with the rapid development in marine and shipbuilding industries such as marine structures, ship, and chemical plants, there occurs much interest in the study of corrosion fatigue characteristics was closed up an important role in mechanical design. In this study, the 5086 Al-Alloy was tested by used of a rotary bending fatigue tester and was investigated under the environments of various specific resistance and air. The specific resistance, as a corrosion environment, was changed 15, 20, 25 and 5000$\Omega$.cm. The corrosion fatigue crack initiation sensitivity was quantitatively inspected for 5086 Al-Alloy in the various specific resistance. The experimental constants of Paris rule were examined in the various specific resistances, and the influences of load and corrosion with affect the crack growth rate were compared with. Main results obtained are as follows: (1) Number of stress cycles to corrosion fatigue crack initiation delaies and corrosion fatigue crack initiation sensitivity decreases with the increasing for the specific resistance. (2) The experimental constant m of Paris rule decreases with the decreasing for specific resistance. Hence the effect of corrosion is more susceptible than that of stress intensity factor. (3) The corrosion fatigue crack of 5086 Aluminium Alloy appears intergranular fracture. (4) Corrosion sensitivity is decreased with the increasing stress intensity factor and is nearly uniform when stress intensity factor is over 40kg.mm super(-3/2)

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05c
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• pp.145-150
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• 1996

Acoustic Emission (AE) technique was applied to stress corrosion cracking of Inconel 600 to investigate the AE capability of detecting crack growth and to obtain the relation between AE characteristics and crack mechanism. The specimens were heat-treated in two conditions (600$^{\circ}C$ for 30 hrs or 700 $^{\circ}C$ for 1 hr) and undergone CERT at two extension rates ( 2.5${\times}$10$^{-5}$ or 1.25${\times}$10$^{－4}$(mm/s)). It was found that the AE peak amplitude from plastic deformation was generally smaller than about 48dB (0.25mV), while Intergranular stress corrosion cracking (IGSCC) and ductile fracture produced higher values of 49 to 70dB (0.3mV to 3mV). The slopes of cumulative amplitude distribution (b-values) were linearly dependent on IGSCC susceptibility and the higher the susceptibility, the smaller the b-value. The monitoring of combined AE parameters such as event rate, amplitude, count and energy can provide effective means to clearly identify the transition from crack initiation and small crack growth to rapid growth of dominant cracks.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.537-544
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• 2003

This paper deals with stress corrosion cracking behavior of high strength steel exposed to marine environments. The objective is to determine the time to failure as a function of hydrogen concentration and tensile stress in the wires. A crack growth curve is modeled using finite element method (FEM) program. The coupled hydrogen diffusion-stress analyses of SCC were programmed separately. The first part is calculating stress and stress intensity /sup 1)/factor of a cylindrical shell, prestressing tendon or suspension bridge wires, from the initiation of cracks to rupture. Virtual crack extension method, contour integral method, and crack tip elements are used for the calculation of stresses in front of the crack tip. Comparisons of the result show a good agreement with the analytical equations and wire tests. The second part of the study deals with the programming of hydrogen diffusion, affected by hydrostatic stress, calculated at the location of boundary of plastic area around the crack tip. The results of paper can be used in the design and management of prestressed structures, cable stayed and suspension bridges. Time dependent correlated parallel reliabilities of a cable, composed of 36 wires, were evaluated by the consideration of the deterioration of stress corrosion cracking.

• Transactions of the Korean Society of Mechanical Engineers
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• v.6 no.4
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• pp.377-383
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• 1982

Acoustic emission (AE) of a high strength steel (SCM-4) was measured under stress corrosion cracking(SCC) test at a constant displacement in 3.5% artificial NaCl solution of 18.deg.C, 45.deg.C and 60.deg.C, respectively. The results are as follows; During the SCC test, AE is detected and AE count rate is approximately proportional to the crack growth rate. Even though crack is not propagated macroscopically, AE is detected. The crack growth rate of SCC and the AE count rate are higher for the solution of higher temperature, 45.deg.C and 60.deg.C, than for the solution of lower temperature, 18.deg.C. In the early stage of SCC, AE total counts mostly depend on crack growth. In the later stage, however, AE mostly depends on the film fracture and the dissolution of anode.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.6
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• pp.996-1003
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• 2001

In order to investigate the fatigue fracture characteristics by corrosion degradation of 12Cr alloy steel, both the fatigue characteristics in air of them artificially degraded during long period and the corrosion fatigue characteristics were experimentally evaluated in various environments which were determined from electro-chemical polarization tests. And also, their fracture mechanisms were analyzed and compared, fractographyically. From their results, the fracture mechanical characteristics of it artificially degraded during long period in the distilled water, 3.5 wt.% NaCl solution and 12.7wt.%(1M) Na$_2$SO$_4$solution of 25, 60 and 90$\^{C}$ did not show distinguishable difference comparing with non-corroded one in regardless of temperature and degradation period. It means that degradation of the material by just surface corrosion does not remarkably affect to fatigue crack growth. On the other hand, the crack growth rates by corrosion fatigue increased due to activity increase of corrosive factors such as OH(sub)-,Cl(sup)- and SO$_4$(sup)- at the crack tip with temperature increase. Therefore, the crack growth rates by corrosion fatigue were more faster than that in air of the artificially degraded specimen due to the such difference of crack growth mechanism.