• Corrosion Science and Technology
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• 제4권5호
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• pp.178-190
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• 2005

In order to develop a new corrosion sensor for detecting and monitoring the external and internal corrosion damage of buried pipeline, the electrochemical property of sensors and the correlation of its output to corrosion rate of steel pipe, were evaluated by electrochemical methods in two soils of varying resistivity (5,000 ohm-cm, 10,000 ohm-cm) and synthetic tap water environments. In this paper, two types of galvanic probes were manufactured: copper-pipeline steel (Cu-CS) and stainless steel-pipeline steel (SS-CS). The corrosion behavior in synthetic groundwater and synthetic tap water for the different electrodes was investigated by potentiodynamic test. The comparison of the sensor output and corrosion rates revealed that a linear relationship was found between the probe current and the corrosion rates. In the soil resistivity of $5,000{\Omega}-cm$ and tap water environments, only the Cu-CS probe had a good linear quantitative relationship between the sensor output current and the corrosion rate of pipeline steel. In the case of $10,000{\Omega}-cm$, although the SS-CS probe showed a better linear correlation than that of Cu-CS probe, the Cu-CS probe is more suitable than SS-CS probe due to the high current output.

• Nuclear Engineering and Technology
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• 제56권2호
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• pp.688-706
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• 2024

Austenitic stainless steels (ASS) are extensively employed in various sectors such as nuclear, power, petrochemical, oil and gas because of their excellent structural strength and resistance to corrosion. SS304 and SS316 are the predominant choices for piping, pressure vessels, heat exchangers, nuclear reactor core components and support structures, but they are susceptible to stress corrosion cracking (SCC) in chloride-rich environments. Over the course of several decades, extensive research efforts have been directed towards evaluating SCC using diverse methodologies and models, albeit some uncertainties persist regarding the precise progression of cracks. This review paper focuses on the application of Acoustic Emission Technique (AET) for assessing SCC damage mechanism by monitoring the dynamic acoustic emissions or inelastic stress waves generated during the initiation and propagation of cracks. AET serves as a valuable non-destructive technique (NDT) for in-service evaluation of the structural integrity within operational conditions and early detection of critical flaws. By leveraging the time domain and time-frequency domain techniques, various Acoustic Emission (AE) parameters can be characterized and correlated with the multi-stage crack damage phenomena. Further theories of the SCC mechanisms are elucidated, with a focus on both the dissolution-based and cleavage-based damage models. Through the comprehensive insights provided here, this review stands to contribute to an enhanced understanding of SCC damage in stainless steels and the potential AET application in nuclear industry.

• 한국안전학회지
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• 제7권1호
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• pp.65-72
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• 1992

Objective of this research is to evaluate fracture behaviors of fresh-butt welded metal by the acoustic emission technique. The specimens used are medium carbon steel(SM45C), mild steel (SS41) and stainless steel(SUS304), which have different weldability. The similar welding and dissimilar welding processes are considered, in the former SM45C, SS41 and SUS304 are used, in the later the following metals are used SM45C and SS41, SM45C and SUS304 and SS41 and SUS304. The characteristics of fracture in weld metal are eshmated by the tension test with nominal speciemns, the fracture toughness test with compact tension specimens and fractography analysis. The results of tension test show for base metals and similar welding materials that the yield strength and ultimate strength of similar welding materials are increased, the elongation of those are decreased. The weldability of SUS304 is better than that of SM45C and SS41 In similar welding materials. Mechanical properties of dissimilar welding mateiiths we lower than those of similar welding materials. In dissimilar welding materials, the weldability of SM45C and SUS304 is better than that of SM45C and SS41, and also weidability of SS41 and SUS304 is better than SS41 and SM45C. Comparing mechanical properties with AE counts, it is found that AE conuts appeared on a small before the limit load of elasticity(P$_{e}$), and apper greatly near yield strength region in tension test. These results could contribute to the safety analyses and the evaluation of strength for welding structure.e.

• 방사성폐기물학회지
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• 제9권2호
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• pp.93-98
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• 2011

염분분위기에서의 부식은 사용후핵연료의 중간저장 기간동안 304 스테인레스 강재 건식저장용기의 주 열화기구들 중 하나다. 본 연구에서는 감소정도가 서로 다른 냉연 304 스테인레스 강 시편들에 0.5wt.%의 염화나트륨 연무를 분사시키면서 느린 변형속도시험(SSRT)과 중성염 분사시험(NSS)을 $85^{\circ}C$와 $200^{\circ}C$ 에서 수행하였다. $85^{\circ}C$에서 2000 시간 동안 시험한 NSS시편의 무게 변화는 $200^{\circ}C$에서 시험한 시편의 무게 변화와 크게 달랐다. NSS 시편의 $85^{\circ}C$에서 무게 감량은 미미하였지만, 냉연 감소율이 증가함에 따라서 무게 변화는 점진적으로 감소하였다. $85^{\circ}C$와 $200^{\circ}C$에서 그리고 염분분사 환경에서 가볍게 냉연 가공된 시편의 SSRT 시험으로부터 얻은 항복강도와 극한 인장응력의 값은 공기 중의 값보다 약간 낮았다. 그러나 염분 분위기에서 부식으로 인한 20% 감소 냉연시편의 강도는 더 이상 변화하지 않았다. 예비결과는 냉연 304 스테인레스 강의 질과 성능이 건식저장용기의 제작을 위한 조건에 맞는다는 것을 증명하였다. 그러나 냉연 스테인레스 강의 장기적인 성능을 더 잘 이해하기 위해서는 염분분위기에서 이 재질의 부식거동에 관한 더 많은 연구가 필요하다.

• KSBB Journal
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• 제16권4호
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• pp.403-408
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• 2001

알코홀 증류폐액은 통상적으로 COD 50,000-60,000 ppm, TS 3-8%, SS 2-4%, TN 0.05-0.2% 정도가 포함되어 있어 높은 SS와 TN 함량 때문에 종합폐수로써 생물학적 처리를 하거나 혐기성 소화를 통하여 처리하는 데 문제가 있다. SS의 주성분으로는 미발효 원료 잔류물과 함께 균체, 단백질, 섬유질, 그리고 기타 현탁성 또는 용해성 물질들이 포함된다. 본 연구에서는 알코홀 증류폐액 처리의 한 해결책으로써 0.1 $\mu$m Pore size를 갖는 스테인레스 재질의 분리막을 이용한 pilot scale 정밀여과(microfiltration)를 실시하였다. Decanter로 처리된 증류폐액을 정밀여과 처리한 결과 2.5 bar, 6$0^{\circ}C$ 조건에서 VCR 농축도 10X 정도가지 원활한 permeate flux를 얻으며 24시간 이상 장시간 여과가 가능하였고 feed 중 0.7%였던 SS가 100% 가까이 제거된 permeate를 얻을 수 있었다. SS는 retentate 중에 7%까지 농축 가능하였으며 COD는 25-27% 정도 제거되었다. SS가 2.6%인 decanter를 거치지 않은 증류 원폐액의 경우, VCR 3X 이내의 조건으로 여과할 때 SS를 100% 가까이 그리고 COD는 약 50% 정도 제거 가능하였다. 무방류 시스템으로의 전용을 위하여 정밀여과로 얻어진 permeate와 retentate를 발효배지 사입수으로 재활용하여 알코홀 발효에 미치는 영향을 검토한 결과, 재활용 사입수를 사용하지 않은 경우에 비해 발효 도중 이상 현상이나 발효속도와 알코홀 생산량에 부정적인 영향을 미치는 징후는 발견되지 않았다. 발효에 의한 총 $CO_2$ 발생량과 최종 알코홀 함량은 약간 증가하고 큰 차이를 보이지 않았으나, 발효시간 동안의 $CO_2$ 발생속도는 비교적 빨라져서 $CO_2$ 발생량 450 L/ton에 도달하는 시간은 재활용 사입수를 15% 사용했을 때 83-87%, 30%를 사용했을 때 72-76% 정도 단축되는 효과를 얻었다. 증류폐액을 처리하기 위해 사용되는 기존 decanter를 대체하여 정밀여과 막분리장치를 이용한다면 SS가 완벽하게 제거됨으로써 폐수처리의 부하를 줄이는 한편 부가적인 농축 공정을 줄일 수 있을 것으로 기대된다. 또한 여과 permeate를 발효배지 사입수로 재활용함으로써 발효속도를 증진시킬 수 있으며 용수사용량을 절약할 수 있다.

• 한국재료학회지
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• 제13권10호
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• pp.651-657
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• 2003

Ultrasonic microscope has been used to detect the defects on surface or inner solid. Conventionally, it has used at a single operating frequency. The resolution and quality of the measured images are determined by a characteristic of the transducer of the ultrasonic microscope. The conventional ultrasonic microscope has been used envelope detector to detect the amplitude of reflected signal, but the changes in amplitude is not sensitive enough for specimen with microstructure that in phase. In this paper, we have studied multi-frequency depth resolution enhancement with ultrasonic reflection microscope for the reflectors of a stainless steel reference specimen and a reference calibration block to be used as the material in nuclear power plants for ISI, PSI. Increased depth resolution can be obtained by taking two, three-dimensional images at more that one frequency and numerically combining the results. As results of the experiment, we could get enhanced images with the rate of contrast in proportion and high quality signal distribution for the image to the changing rate of depth for the reflectors of the two kinds of specimens.

• Applied Microscopy
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• 제45권3호
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• pp.155-169
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• 2015

Plastic deformation was introduced to the austenitic (${\gamma}$) stainless steel of SS304 by air blast shot peening, ultrasonic shot peening, and ultrasonic nanocrystalline surface modification. Various deformation structures were formed. The hardness, the deformation structure and the underlying grain refinement mechanism were investigated. In the deformed region, planar dislocation arrays and deformation twin (DT), the DT-DT intersection and ${\varepsilon}$-martensite structures, and ${\alpha}^{\prime}$-martensite were formed in the respective regions of low, medium, and high strain. The grain refinement mechanism is found to be closely related to the 1) sub-division of coarse grains by DT, shear bands and their intersection, and 2) formation of nano-sized ${\alpha}^{\prime}$-martensite due to the high plastic deformation.

• Corrosion Science and Technology
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• 제18권1호
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• pp.1-7
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• 2019

To find proper lathe machining parameters for SA182 Grade 304 stainless steel (SS), six kinds of samples with different machining surface states were prepared using a lathe. Surface morphologies and microstructures of near surface deformed layers on different samples were analysed. Surface morphologies and chemical composition of oxide films formed on different samples in simulated primary water with $100{\mu}g/L\;O_2$ at $310^{\circ}C$ were characterized. Results showed that surface roughness was mainly affected by lathe feed. Surface machining caused grain refinement at the top layer. A severely deformed layer with different thicknesses formed on all samples. In addition to high defect density caused by surface deformation, phase transformation, residual stress, and strain also affected the oxidation behaviour of SA182 Grade 304 SS in the test solution. Machining parameters used for # 4 (feed, 0.15 mm/r; back engagement, 2 mm; cutting speed, 114.86 m/min) and # 6 (feed,0.20 mm/r; back engagement, 1 mm; cutting speed, 73.01 m/min) samples were found to be proper for lathe machining of SA182 Grade 304 SS.

• Journal of Electrochemical Science and Technology
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• 제13권2호
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• pp.292-307
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• 2022

The study presents kinetics of degradation and mineralization of an anti-epileptic drug Lamotrigine (LAM) in the aqueous matrix by electrochemical advanced oxidation process (EAOP) on Ti/DSA (Ta₂O₅-Ir₂O₅) and Stainless Steel (SS) anodes using sodium sulphate as supporting electrolyte. On both the anodes, kinetic behaviour was pseudo-first-order for degradation as well as mineralization of LAM. On Ti/DSA anode, maximum LAM degradation of 75.42% was observed at an associated specific charge of 3.1 (Ah/litre) at a current density of 1.38 mA/cm² and 100 ppm Na₂SO₄ concentration. Maximum mineralization attained was 44.83% at an associated specific charge of 3.1 (Ah/litre) at a current density of 1.38 mA/cm² and 50 ppm concentration of Na₂SO₄ with energy consumption of 2942.71 kWh/kgTOC. Under identical conditions on SS anode, a maximum of 98.92% LAM degradation was marked after a specific charge (Q) of 3.1 (Ah/litre) at a current density of 1.38 mA/cm² and 100 ppm concentration of Na₂SO₄. Maximum LAM mineralization on SS anode was 98.53%, marked at a specific charge of 3.1 (Ah/litre) at a current density of 1.38 mA/cm² and 75 ppm concentration of Na₂SO₄, with energy consumption of 1312.17 kWh/kgTOC. Higher Mineralization Current Efficiency (MCE) values were attained for EAOP on SS anode for both degradation and mineralization due to occurrence of combined electro-oxidation and electro-coagulation process in comparison to EAOP on Ti/DSA anode due to occurrence of lone electro-oxidation process.

• 대한소아치과학회지
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• 제27권2호
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• pp.274-282
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• 2000

소아의 유구치 수복에 흔히 사용하는 stainless steel crown은 주성분으로 $70\sim90%$의 니켈과 $5\sim15%$의 크롬을 함유하고 있다. 이 중 니켈 자체가 일으킬 수 있는 allergy반응이나 발암성등의 부작용이 성인에서는 활발하게 연구되고 있으며, 특히 니켈이 포함된 합금을 이용한 보철물 주변에 병원성이 있는 니켈내성 Enterococci가 존재한다는 보고가 있어 성인과는 구강환경이 다른 소아에서도 stainless steel crown 주변에 니켈내성균주가 존재하는지를 확인하고자 이 실험을 시행하였다. 유구치에 stainless steel crown(Anatom primary crown, Sankin)을 6개월 이상 장착한 환자 15명과 유구치 협면에 치아우식증이 없는 환자 15명의 치은열구액에서 채취한 시료를 BHI 한천배지, 니켈배지 및 Bile-esculin azide(BEA) 한천 배지에 도말하였다. BEA한천배지에서 자란 enterococci를 니켈내성정도를 확인하기위해 3, 5, 10, 30, 50mM 니켈배지에 접종한후 성장상태를 관찰하였다. 실험군에서는 BHI 한천배지에서 507,350개의 균주가 분리되었으며, 이 중 니켈내성세균(3mM)은 53,864 균주였다. 대조군에서는 BHI 한천배지에서 414,590 균주가, 니켈내성세균(3mM)은 37,523 균주가 분리되었다. BEA한천배지에서는 실험군의 경우 95개가 분리되었으며, 대조군에서는 20개의 균주만이 분리되었다. BHI 한천배지에서 분리된 총 균주 수를 100으로 놓았을 때 3mM 니켈배지에서 분리된 균주는 실험군에서는 10.62%, 대조군에서는 9.05%를 차지하여 두 군간에 뚜렷한 차이는 없었으며, 3mM 니켈배지에서 자란 총 균주 수와 BEA 한천배지에서 배양된 enterococci를 3mM 니켈배지로 옮겨 배양했을 때와 비교하면, 실험군에서 0.13%, 대조군에서 0.03%로 모두 1%이하의 분포를 차지하였다.