• Proceeding of KASS Symposium
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• 2006.05a
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• pp.66-72
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• 2006

Recently nonlinear materials are used in construction of building and bridge then various structure formats are achieved positively. one of them, cable members, are the interesting study object which increase rigidity of a total structure by inducing tension. The way of construction using cable members is increasing, so the technology of design and construction are developing. Protection Fretting Fatigue is very important to maintain efficiency of cable member permanently. However, recognition of this is somewhat humble and this paper considers anti-corrosive performance of cable.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.465-466
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• 2002

In any mechanical system consisting of gears, shafts and/or bearings, the majority of metallic particles deposited into and carried by the lubrication system originate from the deterioration of oil-wetted working surfaces, even in proper lubrication system, due to failure mechanism (s) such as wear, fatigue and fretting corrosion. Determination of the point at which transition from normal to abnormal or to actual damage occurs has become a focus of attention in research activities for years, because it has been recognized that reliable, economic operation can be achieved through appropriate preventative measures. Known collectively from 'all size wear debris analysis' as early failure detection, the methods of testing for damage differ considerably, range from a micron or a submicron size debris analysis to Magnetic Chip Detector (MCD) ferrous debris analysis. This paper will be focused on the utilization of the low-cost analysis techniques for evaluation of industrial machinery condition.

• Korean Journal of Materials Research
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• v.18 no.9
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• pp.497-502
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• 2008

BGA test sockets failed earlier than the expected life-time due to abnormal signal delay, shown especially at the low temperature ($-50^{\circ}C$). Analysis of failed sockets was conducted by EDX, AES, and XRD. A SnO layer contaminated with C was found to form on the surface of socket pins. The formation of SnO layer was attributed to the repeated Sn transfer from BGA balls to pin surface and instant oxidation of fresh Sn. As a result, contact resistance increased, inducing signal delay. Abnormal signal delay at the low temperature was attributed to the increasing resistivity of Sn oxide with decreasing temperature, as manifested by the resistance measurement of $SnO_2$.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.7
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• pp.1006-1013
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• 2004

Operating experience of steam generators shows that the tubes are degraded by stress corrosion cracking, fretting wear and so on. These defected tubes could stay in service if it is proved that the tubes have sufficient structural margin to preclude the risk of tube bursting. This paper provides detailed plastic limit pressure solutions for through-wall cracks in the steam generator tubes. These are developed based on three dimensional(3D) finite element analyses assuming elastic-perfectly plastic material behavior. Both axial and circumferential through-wall cracks in free span and in u-bend regions are considered. The resulting limit pressure solutions are given in a polynomial form, and thus can be simply used in practical integrity assessment of the steam generator tubes.

• 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.

• Journal of Yeungnam Medical Science
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• v.7 no.1
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• pp.81-93
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• 1990

The author fractographically analyized the cause of metal failure(the first time this procedure has been used for this metal failure)and also analyized it clinically. In this study, I selected eight cases which have been analyized fractographically. In all these cases, the analysis was done after treatment of metal failure of implants internally fixed to femur shaft fractures at the Department of Orthopedic Surgery, Yeung-Nam University Hospital during the six year period from May 1983 to September 1989. 1. Metal failure occured in five dynamic-compression plates, one Jewett nail, one screw in Rowe plate, and one interlocking nail. 2. The clinical cause of metal failure was deficiency of medial butress in five cases, incorrect position of implant in one case, and incorrect selection of implant in two cases. 3. The time interval between internal fixation and metal failure was four months in one case, between five months to twelve months in six cases, three years in one case. 4. The fractographically analytical cause of metal failure was ; first, impact failure, one case, second, fatigue failure, six cases, machining mark(stress liser), four cases type : low consistent cyclic fatigue failure irregular cyclic fatigue failure third, stress corrosion crack, one case. 5. 316L Stainless Steel has good resistance to corrosion. However, when its peculiar surface film is destroyed by fretting, it shows pitting corrosion. This is, perhaps, the main cause of metal failure. 6. It is possible that mechanical injury occured in implants during the manufacturing of implants or that making a screw hole is the main cause of metal failure.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.4
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• pp.409-416
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• 2012

Recently, surface modification technology is of importance to improve the wear resistance and the corrosive resistance for high accurate mechanical parts such as LM guide, Ball Screw and Roller Bearing etc., Those has generally featured on rolling contact mechanism to improve not only the wear and the friction, but also the accuracy and the corrosion performances. For surface modifications of high accurate mechanical parts, normally thermal spray, PVD, CVD and E.P. processes have been used with many materials such as DLC, raydent, W, Ni, Ti etc. Diamondlike carbon (DLC) films possess a combination of attractive properties and have been largely employed to modify the tribological behaviors such as friction, wear, corrosion, fretting fatigue, biocompatibility, etc. However, for rolling contact mechanism mechanical parts DLC films are needed to study for commercial benefit. Rolling contact mechanism has features on effects of cyclic motions and stresses, and also not simply sliding motions. The papers focused on the performance test of wear and corrosive resistance according to Me-DLC film thickness. And also, its thickness effect of wear analysis was carried out through the simulation of the maximum shear stress under the rolling contact surface. As the results, Me-DLC films have more potential to improve the wear resistance for high precision mechanical parts than raydent films.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.12 s.255
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• pp.1618-1625
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• 2006

During the last two decades, several guidelines have been developed and used for assessing the integrity of a defective steam generator (SG) tube that is generally caused by stress corrosion cracking or wall-thinning phenomenon. However, as some of SG tubes are also failed due to fretting and so on, alternative failure estimation schemes are required for relevant defects. In this paper, parametric three-dimensional finite element (FE) analyses are carried out under internal pressure condition to simulate the failure behavior of SG tubes with different defect configurations; elliptical wear, tapered and flat wear type defects. Maximum pressures based on material strengths are obtained from more than a hundred FE results to predict the failure of SG tube. After investigating the effect of key parameters such as defect depth, defect length and wrap angle, simplified failure estimation equations are proposed in relation to the equivalent stress at the deepest point in wear region. Comparison of failure pressures predicted by the proposed estimation scheme with corresponding burst test data showed a good agreement.

• 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.