• Journal of Advanced Marine Engineering and Technology
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• v.19 no.2
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• pp.47-55
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• 1995

When the low heavy oil is using as fuel oil to the diesel engine, some problems such as corrosion resistance, wear resistance and heat resistance are happened in diesel engine's internal material, especially the adhesive wear of piston ring groove was occurred as a important problem. Therefore to prevent adhesive wear of its groove, the surface of its groove used to be electroplated with Chrominum and for its Chromium electroplating, Fe anode is being used until nowadays because of its Special shape. However in case of using Fe anode, there were some problems such as deterioation of solution, property of Chromium film, and condition of coation. In this paper Pb anode electroplated withPb to the steel plate was investigated for its Chromium electroplating for Pb's high corrosion resistance in acid solution, and Pb anode is not dissolved compared with Fe anode and deterioration degree of solution in case of Pb anode is smaller than that of Fe anode and also property of Chromium film was better than that of Fe anode. Moreover it was known that the optimum cathodic current density for Pb electroplating to steel plate as insoluable anode for Chromium coating of piston ring groove is 30mA/$cm^2$ by experimental results obtained.

• Tunnel and Underground Space
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• v.14 no.5
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• pp.363-372
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• 2004

Double torsion (DT) tests were carried out to investigate the influence of the geometry of guide groove on stress corrosion index of Kumamoto andesite. The fracture toughness was measured in the constant displacement rate, which was set to 2.07 MN/m$^{3}$2/ in average regardless of crack velocity. Stress corrosion indices, n were evaluated using specimens with rectangular, circular and triangular grooves and were 37, 36 and 38 in average, respectively. The n values were constant regardless of the groove geometry, however the DT specimen with triangular groove geometry showed the largest standard deviation in the relationship between crack velocity and stress intensity factor. The DT test was found to be effective in using a rectangular-grooved specimen and the width of the groove must be greater than the average grain size of minerals.

• Corrosion Science and Technology
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• v.6 no.3
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• pp.140-146
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• 2007

In the paper, with corrosion velocity measurement and metallographic observation on specimens after sulfuric acid/ferric sulfate boiling experiment, intergranular corrosion tendency of the new type ultra low carbon stainless steel developed by ourselves which experienced solution treatment at different temperatures was evaluated. A VHX 500 super depth field tridimensional microscope was used to observe corrosion patterns on the sample surfaces. The depth and width of grain boundary corrosion groove were measured by the tridimensional microscope, which indicated that the corrosion degrees of the samples which received solution treatment at different temperatures are quite different. Transgranular corrosion at different degree occurred along with forged glide lines. After comparison it was proved that the stainless steel treated at $1100^{\circ}C$ performs very well against intergranular corrosion.

• Journal of Ocean Engineering and Technology
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• v.13 no.3 s.33
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• pp.68-76
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• 1999

The welding residual stresses produced by the welding frequently caused a crack and promote stress corrosion etc. in HAZ(heat affected zone) contained with external load and weakness of material. Therefore, PWHT(post welding heat treatment) is widely used to reduce wekdubg residuss, to relax hardening of heat affected zone and to get rid of impurity. In this study, in order to define the effect on shappes of T-welded joint, during the post welding heat treatment, we have carried out numerical analyses on the several test pieces by using computer program which was based on thermal-elasto-plato-plasto-creep theories for the study. The main results obtained form this study is as follows: 1) The mechanical difference for change the thickness of plate and groove angle did not appear. 2) The distribution modes of welding residual stresses are same on the all test specimens during the post welding heat treatment. 3) In a mecharical point of view, minimum groove groove angle($40^{circ}$) is more suitable than maximum groove angle($60^{circ}$). 4) Therefore, it is appropriate to minimize the size of groove shape in strength and safety.

• Journal of the Korean Institute of Rural Architecture
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• v.12 no.4
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• pp.1-11
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• 2010

This study is a research examining reshaped pattern in the perspective of repairing parts and materials through repairing renovation of registered cultural properties constructed in modern times and results are as followings. Repairing construction of registered cultural properties of Jollanamdo according to parts is shown numerously in the order of roof, walls and windows, and mostly outworn as time passes on and leakage were the main cause of repair. Also when original shape was damaged by previous repair in the past, and this was another reason of repairing. It was surveyed that among the repairing job repair of damage occurred on the part of roofing area including water leakage, corrosion and damage of roofing material, and damage of groove channel were the most main cause of repair. Especially when roof leakage is occurred by outworn of roofing materials, this cause corrosion and damage of materials due to the damage of leakage parts and this cause repeating cycles of worse leakage again and again. Main repairing materials which deform the original shape of registered cultural properties were confirmed as copper plate used on the roof. Copper plate showing high frequency of application which replaces groove slate or cement roofing tile used on the roof before has high durability and anti-corrosion but it is considered improper material to recover original shape.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.6 no.2
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• pp.20-27
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• 2010

In order to prevent the corrosion of component contacted primary water designed alloy 600 material in the nuclear power plant. But the primary water stress corrosion cracking(PWSCC) of alloy 600 and weld area occurs continuously due to the residual stress. The leakage accident resulted from PWSCC in the drain nozzle of the steam generator of domestic power plants. Heater sleeves of the pressurizer are welded with alloy 600 weld material and therefore exposed to the primary water environment. PWSCC occurred in heater sleeve material and weld area of many foreign power plants. The current issue of domestic nuclear power plants are consequently concentrated to PWSCC of similar material. In order to improve the detection and the sizing of the PWSCC in the welding sleeve of the pressurizer, the automatic UT system and multi-directions probe sets have been developed. The experimental studies have been performed using the mock-up block containing artificial reflectors(ID connected EDM notch) and semi-artificial cracks made from thermal fatigue. The automatic UT System is applied in the detection and the length sizing of the ID/OD on the tube and the J-groove weld area of the artificial reflectors and results of the detection and the sizing are compared respectively. Also, the developed automatic UT system is successfully accomplished to inspect the heater sleeve and the J-groove weld area on the pressurizer for the detection of PWSCC.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.11 s.170
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• pp.2096-2101
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• 1999

This paper presents the effect of shape of external corrosion in pipeline on failure prediction by using numerical simulation. The numerical study for the pipeline failure analysis is based on the FEM(Finite Element Method) with an elastic-plastic and large-deformation analysis. The predicted failure stress assessed for the simulated corrosion defects having different corroded shapes along the pipeline axis are compared with those by methods specified in ANSl/ASME B31G code and a modified B31G code.

• Journal of Power System Engineering
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• v.11 no.3
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• pp.41-46
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• 2007

The microstructure and electrochemical analysis of welds of electric resistance welding(ERW) pipe were investigated. The direction of metal flow line in HAZ of ERW pipe shifted to the inner(or outer) surface of pipe by plastic deformation during welding. The lowest heat input welds of ERW pipe was showed crack by liquid penetrant testing. Accelerated corrosion test by constant current density of 20mA/$cm^{2}$ developed groove at the welds of ERW pipe and the measured grooving factors were about $1.2{\sim}1.5$. Corrosion potential of base metal obtained by cyclic polarization in artificial sea water(3.5wt.% NaCl solution) was 100mV higher than that of weld metal of ERW pipe.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.82-82
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• 2009

Although leakage at a low carbon steel pipe made by electrical resistance welding(ERW) was reported due to grooving corrosion, the cause for the corrosion has not yet been cleared. So lots of researches were carried out already about grooving corrosion mechanism of ERW carbon steel pipe but there is seldom study for water hammer happened by fluid phenomenon and corrosion rate by flow velocity. In this study, the corrosion test carried out using the ERW carbon steel pipe by changed the water speed and heat input in a month. The level of dissolved oxygen is maintained 5~5.5mg/l(amount of dissolved oxygen in tap water). The water speed for corrosion test is 1m/s, 2m/s, 3m/s. As the results, grooving corrosion rate is increased cause by water speed in the pipe. In the case of the ERW pipe with more heat input, grooving corrosion rate is decreased. It is therefore that welding heat input should be controlled based on the carbon content of the pipe in order to improve the corrosion reistance of the ERW pipe.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.10
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• pp.1115-1130
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• 2012

In nuclear power plants, the reactor pressure vessel (RPV) upper head control rod drive mechanism (CRDM) penetration nozzles are fabricated using J-groove weld geometry. Recently, the incidences of cracking in Alloy 600 CRDM nozzles and their associated welds have increased significantly. The cracking mechanism has been attributed to primary water stress corrosion cracking (PWSCC), and it has been shown to be driven by welding residual stresses and operational stresses in the weld region. The weld-induced residual stress is the main factor contributing to crack growth. Therefore, an exact estimation of the residual stress is important for ensuring reliable operation. This study presents the residual stress computation performed for an RPV CRDM penetration nozzle in Korea. Based on two and three dimensional finite element analyses, the effect of welding variables on the residual stress variation is estimated for sensitivity analysis.