• Journal of the Korean Society for Precision Engineering
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• v.22 no.11 s.176
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• pp.125-134
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• 2005

Recently, there have been reported on the results that the material life is reduced by fretting conditions and the initial crack made by low stress under fretting. The purpose of this paper is to show that the results of finite element analysis for the fretting contact problems of a flat rounded punch are nearly consistent with the theoretical solutions and to research that the results about effects of the contact zone according to geometries and mechanical properties of pad.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1648-1651
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• 2005

Fretting contact and fretting fatigue are known to occur in mechanical devices which have fasteners subjected to oscillatory tangential load. Theoretical studies on fretting contact have been focussed on simple geometries, such as cylindrical contact problem. Recently, the contact problem of a flat rounded punch has been solved theoretically. The purpose of this paper is to show that the results of finite element analysis for the fretting contact problem are nearly consistent with the theoretical solutions.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.11a
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• pp.1043-1044
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• 2010

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.115-118
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• 2004

In this study, amplitudes of turbulence excitation are obtained for selected tubes inside the KSNP SG and their normal work-rates are investigated to estimate the magnitude of fretting-wear. From the results of numerical calculation, row 40&41 tubes show the maximum work-rates. Up to this row number, the work-rates inside the row 41 have much larger values than those of outside tubes. This phenomenon reveals the particular central one which has larger normal work-rate than that of outside zone. It turns out that both of the higher local mode at the U-bend region and the larger value of effective mass in the central region Increase the normal work-rate enormously.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.11 no.1
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• pp.20-24
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• 2015

Steam generator(S/G) tubes in pressurized water reactor (PWR's) are subject to several types of degradation. This degradation includes denting, pitting, intergranular attack(IGA), intergranular stress corrosion cracking(IGSCC), fatigue, fretting and wear. Degradation can be derived from either the primary side(inside) or the secondary side(outside) of the tube. Recent issue for tube degradation in domestic steam generator is the tube end cracking on seal weld region. The seal weld region at the tube end and tube itself is regarded as a pressure boundary between the primary side and the secondary side. One of the Westinghouse Model-F S/G has experienced tube end cracking and its number of plugging approximately becomes to the operating limit up to 5% due to tube end cracking which was reported as SAI/MAI(single/multiple axial indication) or SCI/MCI(Single/multiple circumferential indication) from the results of eddy current testing. Eddy current mock-up test was carried out to determine the origin of cracking whether it is from weld zone area or parent tube. This result was helpful to analyze crack location on ECT data. Correct action on this problem was the installation of tube-end sleeve. Last year, after removing 340 installed plugs from tubes, selected 269 tubes took tube-end sleeve installation. Tube-end sleeve brought pressure boundary from parent tube to installed sleeve tube. Tube-end sleeve has the benefit of reducing outage period and increasing more revenue than replacing S/G. This paper is provided to assist interest parties in effectively understanding this issue.