• Journal of Advanced Marine Engineering and Technology
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• v.8 no.2
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• pp.39-50
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• 1984

The plane bending corrosion fatigue test was performed on the welded zone between SM58 steel plate and SM41 steel plate jointed with submerged arc welding in the air and in the natural sea water with various conditions. The main results obtained from the test are summarized as follows: 1) The welded zone of the steel plates has the lowest impact strength and the highest electrode potential, but the hardness was mediate of SM58 base and SM41 base. 2) The cathodic protection of the welded zone was also effective for the plane bending corrosion fatigue, and the optimum protection potential of the welded zone was -1,000 mV SCE. 3) The corrosion fatigue strength under the various stress conditions of the steel plate could be estimated and also the require safety factors on the design could be obtained from the plane bending fatigue limit diagram.

• 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.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.6 no.3
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• pp.65-72
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• 1997

The horizontal corrosion fatigue tester has been developed for investigating environmental strength. Using this tester, we investigated about corrosion fatigue caracteristics for A106-Gr B steel weldments in 3.5% synthetic seawater and room temperature. Considered parameter is only frequency of 1, 3 and 5Hz.. and Corrosion fatigue crack length was measured by DC potential difference method. From the results, we could find that the horizontal corrosion fatigue tester could be well applied to estimation of fatigue strength. and, In case of 5Hz., corrosion fatigue crack growth pate of A106-Gr B steel weldment was transgranular, and of 1 and 3Hz. showed that transgranular and interfranular was mixed. Also, Material constants of corrosion fatigue crack growth estimated in each frequency were C=9.33$\times$$10^{-9}$ and m=2.93 in 1Hz., C=9.77$\times$$10^{-10}$ and m=3.47 in 3Hz., C=1.02$\times$$10^{-10}$ and m=4.05 in 5Hz

• Korean Journal of Materials Research
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• v.31 no.3
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• pp.172-180
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• 2021

In this study, using the plasma spray method, tensile and compression fatigue tests are performed in saline solution to examine the effect of Ti undercoat on corrosion fatigue behavior of alumina-coated specimens. The alumina-coated material using Ti in the undercoat shows better corrosion fatigue strength than the base material in the entire stress amplitude range. Fatigue cracking of UT specimens occurs in the recess formed by grit-blasting treatment and progresses toward the base metal. Subsequently, the undercoat is destroyed at a stage where the deformation of the undercoat cannot follow the crack opening displacement. The residual stress of the UT specimen has a tensile residual stress up to about 100 ㎛ below the surface of the base material; however, when the depth exceeds 100 ㎛, the residual stress becomes a compressive residual stress. In addition, the inside of the spray coating film is compressive residual stress, which contributes to improving the fatigue strength characteristics. A hardened layer due to grit-blasting treatment is formed near the surface of the UT specimen, contributing to the improvement of the fatigue strength characteristics. Since the natural potential of Ti spray coating film is slightly higher than that of the base material, it exhibits excellent corrosion resistance; however, when physiological saline intrudes, a galvanic battery is formed and the base material corrodes preferentially.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.716-721
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• 2004

Corrosion highly affects to reduce lifetime and performance of machinery metallic components. The effects of shot peening on the fatigue life of metal material under corrosive environment are investigated in this paper. Experimental results show that the fatigue limit of shot peened specimen increases about 52$\%$. That means the fatigue life of metallic components is highly extended by shot peening. The corrosion greatly reduces the fatigue strength depending on the corrosive condition from one week up to one year. In case of shot peened specimen, the corrosion does not reduce the fatigue strength and fatigue life up to six months. It means that shot peening has superior effectiveness to reduce the influence of corrosion to the metallic materials.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.8
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• pp.1503-1512
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• 1992

The strength evaluation and life prediction on the corrosion part of structure is one of the most important subjects, as a viewpoint of reducing economic loss by regular inspection, maintenance, repair and replace. For this purpose, it has been difficult to obtain the available data on growth of pit depth or growth rate of each pit which depends on time. In this paper, the life prediction and strength evaluation method was suggested for the structure with irregular stress concentration part by surface corrosion. The statistical distribution pattern of corrosion depth and the degree of fatigue strength decline were confirmed according to corrosion period by artificial corrosion of SS41 steel. The life prediction and the fatigue strength evaluation of materials with consideration of the corrosion period on the extreme value statistic analysis by the data of maximum depth of corrosion and on random variable was studied.

• Journal of the Korean Society for Precision Engineering
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• v.6 no.1
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• pp.75-84
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• 1989

This paper deals with the effect of $N_2$ and $H_2$gas mixture ratio and ion-nitriding time in the corrosion fatigue fracture behavior of ion-nitrided SCM4 steel with notch subject to rotary bending stress. The specimens were treated rapid water cooling after ion-nitriding at $500^{\circ}C$ Torr for 1 hour and 3 hours in gas mixtures of 80% $N_2$and 50% $N_2$. The fatigue limit and the fracture strength of corrosion fatigue depended on $N_2$gas quantity and ion-nitriding time. The ion-nitrided specimens showed about 88 .approx. 158% increase in the fracture strength of corrosion fatigue in $10^6$ cycles than non-nitrided specimens. The corrosion failure is due to corrosion pitting of the surface, and the propargation of cracks started at the surface into the core.

• Journal of Ocean Engineering and Technology
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• v.6 no.2
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• pp.85-93
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• 1992

The only hardness of 2nd phase of martensite in dual phase steel which was composed of the martensite and ferrite was changed. Fatigue test was conducted by cantilever type of self-made rotated bending fatigue testing machine. The corrosion fatigue fracture behaviors of dual phase steel were investigated in 3% NaCl solution at $N_f$ = $1.5\times$$10^5$ $N_f$=1.0 $\times$ $10^6$ cycles. The fatigue strength was increased with increasing the hardness of 2nd phase. The size and number of corrsion pits were influenced by the 2nd phase hardness and pits remain constant in size just after they were transited into cracks. The life of crack initiation was effected by stress level. The shape of relation of $\Delta$K and da/dn has smaller scattering in it in 3% NaCl solution than that in air. The higher the 2nd phase hardness is, the higher the corrosion fatigue life becomes. Corrosion fatigue fracture behavior was effected by mechanics in case of $N_f$=1.5$\times$10$^5$$N_f$=1.5$\times$10$^6$ cycles.

• Journal of Ocean Engineering and Technology
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• v.10 no.3
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• pp.14-23
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• 1996

The corrosion fatigue test were carried out to evaluate the fatigue characteristics of accelerated cooled (ACC) TMCP high tensile strength steels and weld joint with high heat input by one side one run submerged are welding. In this paper, the fatigue crack growth behaviors were investigated with the center crack tension specimen of base metal and heat affected zone in substitute sea water and air, respectively Main results obtained are sunnarized as follows: 1. The fatigue crack growth rates in sea water faster than those in air environment for the different heat input values, crack growth rate of base metal is very fast and effect of heat input is not remarkable. 2. In HAZ (82kJ/cm, 116kJ/cm), the crack branching phenomena were observed in both air and sea water environment, 3. In SEM observation, the corrosion effect on base metal was larger than that on HAZ in corrosion environment.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.102-107
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• 2004

Suspension part should have enough endurance during its lifetime to protect passenger. Therefore, the coil spring is one of the major suspension part of an automobile. Corrosion fatigue strength of the coil spring depends on many factors including mechanical and environmental properties. In this paper, residual stresses by shot peening was analyzed using finite element analysis and evaluated its effect on corrosion fatigue strength.