• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.06a
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• pp.38-46
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• 1999

Numerical methods are procured for evaluating the contact stresses, the dissipation of friction energy density and the fatigue cracking emanated from the contact surface under the partial slip condition. A rounded punch is used for the indenter pressing and slipping on the elastic half plane. Plane strain condition is assumed for the present analysis. Several sample calculations are carried out to investigate the effect of the punch roundness, the shear load path, and the crack obliquity and closure on the failure. It is found that the present methods can be a useful tool for studying the physical failure of the of the contacting materials such as fretting wear and fretting fatigue cracking.

• Journal of the Korean Society of Industry Convergence
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• v.7 no.4
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• pp.399-405
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• 2004

Currently, the use of carbon steel in a high temperature environment, such atomic reactor, increases. Test piece was heated in electric furnace and the prescribed temperature was controlled within ${\pm}1^{\circ}C$. Debris that falls apart from cracked section due to friction is accumulated inside. Then, as it causes fretting corrosion (formation of oxide layer), it contributes to crack closure.

• Journal of the Korean Society of Safety
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• v.19 no.2
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• pp.11-15
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• 2004

The fretting-fatigue by leaking is one of the significant degradation in steam generator tubes. In this study, the burst pressure of inclined damaged steam generator tubes were obtained from three criterions by using the finite element method. The analysis results were also compared with the experiment data from published references and they showed a good agreement with the experiment data.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.205-210
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• 2001

Fatigue crack growth tests were carried out using high manganese cast steel under constant amplitude loading. Average crystal grain sizes of the material are $200{\mu}m$ and $1000{\mu}m$. For this material, ${\Delta}K_{th}$ is about $8MPa{\sqrt{m}}$ which is quiet large as compared to the general structural steels and the crack growth rate is lower than the general structural steels especilly in the low ${\Delta}K$ regsion. The reason of this behavior is crack closure due to fracture surface roughness and fretting oxide. The relationship between da/dN and the ${\Delta}K_{eq}$ was represented by narrow band regardless of the stress ratio.

• 한국기계연구소 소보
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• v.4 no.1
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• pp.19-26
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• 1981

Fatigue, the birth and growth of cracks in metal parts subjected to repeated loading, has been a problem plaguing engineers since the Industrial Revolution and the advent of rotating or reciprocating machinery. Designing against metal fatigue was studied briefly in several aspects. Examples of fatigue failures were shown. Fatigue was classified by loading: uniaxial Fatigue, multiaxial fatigue, cumulative fatigue da¬mage. Fatigue design criteria were discussed: Infinite-Life Design, Safe-Life Design, Fail-Safe Design, and Damage Tolerant Design. Mitigation of notch effects by design, improvement of fatigue strength of metal parts by residual stress and surface finishing were discussed. Relative fatigue beha¬vior was studied under various environmantal conditions. Especially the effects of corrosion, temperature, fretting, and irradiation were covered.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.2
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• pp.167-175
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• 2014

If volumetric flaws such as bearing pad fretting flaws and debris fretting flaws are detected in the pressure tubes of pressurized heavy water reactors during in-service inspection, the initiation of fatigue cracks and delayed hydrogen cracking from the detected volumetric flaws shall be assessed by using elastic stress concentration factors in accordance with CSA N285.8-05. The CSA N285.8-05 presents only an approximate formula based on linear elastic fracture mechanics for the debris fretting flaw. In this study, an engineering formula considering the geometric characteristics of the debris fretting flaw in detail was derived using two-dimensional finite element analysis and Kinectrics, Inc.'s engineering procedure with slight modifications. Comparing the application results obtained using the derived formula with the three-dimensional finite element analysis results, it is found that the results obtained using the derived formula agree well with the results of the finite element analysis.

• Progress in Superconductivity and Cryogenics
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• v.3 no.1
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• pp.1-5
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• 2001

In order to investigate the effect of fatigue damage on the properties of RRR in this study. fatigue tests at room temperature and residual resistivity measurement tests at 12K were carried out using annealed 9 strand Cu-Ni/NbTi/Cu composite cables Through fatigue tests of NbTi composite cables. a conventional S-N curve could be obtained even though there existed a possibility of fretting among strands, From the resistivity measurement of a NbTi strand after fatigue test, it was found that the RRR of xii·gin strand for annealed cables was 3 times more than that for as-received one. With increasing of fatigue cycles at a sress amplitude level. the RRR decreased. which was resulted from the accumulation of damage such as lattice defects and dislocation within the Cu stabilizer.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.1
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• pp.91-99
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• 2006

Fatigue properties of INVAR/AW wires have been investigated under the heat exposure in order to ensure stable operation and to estimate life span of their power line. In the case of heat exposure for 10000 hr, fatigue life and limit increased. For further heat exposure, fatigue limit decreased due to the decrease in yield strength. The variation fatigue of strand wire was strongly dependent on its amplitude. Also, cracks in wires of 7 strands were caused by stress concentration at the outer surface and fretting between each wire during vibration.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 1999.02a
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• pp.30-33
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• 1999

In this study, the fatigue test at room temperature and residual resistivity measurement test at 12K were carried out, respectively, using a 9 strand Cu-Ni/NbTi/Cu composite cable, in order to investigate how the fatigue damage effects on critical properties. Through the fatigue test of a 9 strand Cu-Ni/NbTi/Cu composite cable, a conventional S-N curve was obtained even though there existed a possibility of fretting among strands. From the resistivity measurement of a NbTi strand after fatigue tests, it was found that with increase of the repeated number the RRR increased slightly, and the trend became significant with increase in maximum value of the applied stress amplitude.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2000.02a
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• pp.104-108
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• 2000

In this study, the fatigue test at room temperature and residual resistivity measurement test at 12K were carried out, respectively, using a 0 strand Cu-Ni/NbTi/Cu composite cable, in order to investigate how the annealing treatment effects on critical properties due to fatigue damage. Through a fatigue test of a 0 strand Cu-Ni/NbTi/Cu composite cables, a conventional S-N curve was obtained even though there existed a possibility of fretting among strands. From the resistivity measurement of a NbTi strand after fatigue tests, it was found that the RRR for annealed cables was 3 times more than that for as-received one, but with increase of the repeated number the RRR decreased which was resulted from the accumulation of damage such as lattice defects dislocation within the Cu stabilizer.