• 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.

• 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.

• Nuclear Engineering and Technology
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• v.51 no.4
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• pp.1060-1068
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• 2019

This work aims to establish a model of a primary water stress corrosion crack growth rate of Alloy 690 material for the head penetration nozzles of Korean pressurized water reactors. The test material had an inhomogeneous microstructure with bands of fine-grains and intragranular carbides in the matrix of coarse-grains, which was similar to the archive materials of the head penetration nozzles. The crack growth rate was measured from the strain-hardened materials as a function of the stress intensity factor in simulated primary water at various temperatures and dissolved hydrogen contents. The effects of strain-hardening, temperature, and dissolved hydrogen on the crack growth rate were analyzed independently, and were then introduced as normalizing factors in the crack growth rate model. The crack growth rate model proposed in this work provides a key element of the tools needed to assess the progress of a stress corrosion crack when detected in thick-wall Alloy 690 components in Korean reactors.

• 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.

• Journal of Power System Engineering
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• v.8 no.3
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• pp.44-51
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• 2004

Effect of corrosion characteristics in relation to loaded stress in the welded zone of A5083-H116 aluminum alloy, in the seawater was studied. The corrosion experiment was performed for 120 hours on the specimens in the natural seawater tank with four steps of the loaded stress. The corrosion crack, corrosion rate, electrode potential, current, and corrosion pattern, etc. were examined for the specimens with the elapse of the immersion time. The main result derived from this study is the crack growth length is increased with the increasing loaded stress. The electrode potential and the corrosion current are decreased rapidly in the early stage of the corrosion, and then decreased gradually and stabilized eventually with the elapse of the immersion time. The test condition of the longer crack growth tends to show the higher corrosion rate. Corrosion pattern of the welded zone indicates that the depth and width of the pitting become increasing with the increasing loaded stress.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.7 s.178
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• pp.1841-1846
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• 2000

To examine the effect of acid fog on the corrosion fatigue behavior in structural steel, fatigue tests under acid fog atmosphere were carried out in comparison with distilled water. The corrosive c omponents contained in acid fog pile up the corrosion products on crack face and show a crack branching and crack tip blunting. Therefore, due to these workings crack growth rate was reduced by decreasing the effective stress range in crack tip rather than under distilled water. Also the effect of sulfuric acid, which is the main component of acid fog, and testing speed on fatigue crack growth were examined. It was found that corrosion behavior was remarkably dependent upon pH and Hz rather than components of acid fog. According as pH and testing speed decrease below a specific value, crack growth was accelerated in comparison with distilled water. This reveals that due to liquid having strong acidity and slow speed of test the crack face dissolution was promoted, so crack closure was disturbed in the process of stress descent.

• 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.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.11 no.2
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• pp.45-50
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• 2015

In many cases, the field fracture mechanism of the thermoplastic pipe is considered as either brittle or environmental fractures. Thus the estimation of the lifetime by modeling slow crack growth considering such fracture mechanisms is required. In comparison of the some conventional and empirical equations to explain the slow crack growth rate such as the Paris' law, the crack layer theory can be used to simulate the crack and process zone growth behaviors precisely, so the lifetime of thermoplastic pipe can also be accurately estimated. In this study, the modified crack layer theory for the stress corrosion cracking (SCC) of high density polyethylene is introduced with detailed algorithm. The oxidation induction time of the HDPE is also considered for the reduction of specific fracture energy during exposed to chemical environments. Furthermore, the parametric study for an important SCC parameter is conducted to understand the slow crack growth behavior of SCC.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.6 no.2
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• pp.34-40
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• 2007

Antifatigue failure technology take an important part of current industries. Currently, the shot peening is used for removing the defect from the surface of steel and improving the fatigue strength on surface. Therefore, this paper the effect of compressive residual stress and corrosion of spring steel(SAE 5155)by shot-peening on fatigue crack growth characteristics in stress ratio(R=0.05)was investigated with considering fracture mechanics. By using the methods mentioned above, We arrived at the following conclusions. The fatigue crack growth rate(da/dN) of the shot-peening material was lower than that of the un-peening material. And in stage I, ${\Delta}Kth$, the threshold stress intensity factor, of the shot-peen processed material is high in critical parts unlike the un-peening material. Also m, fatigue crack growth exponent and number of cycle of the shot-peening material was higher than that of the un-peening material. That is concluded from effect of da/dN. Finally fracture of shot-peening material and un-peening material was identified and discussed in this study.

• Journal of Industrial Technology
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• v.17
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• pp.291-295
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• 1997

The tests of stress corrosion cracking in structural carbon steel were carried out under the conditions of acid fog and general water. As the result of measurement SCC rupture time under acid fog was observed to be much shorter than that of general water at the same stress level. Therefore, acid fog drops the SCC strength in structural carbon steel due to strong corrosion. In the SCC process by acid fog, crack initiation was caused by pit corrosion and local stress concentration, and distinctive feature of crack growth shows branching since crack grows to the corrosion direction. Moreover, corrosion products were observed by clevage corrosion on the crack surfaces.