• Journal of Welding and Joining
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• 제32권6호
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• pp.70-74
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• 2014

On this study, we researched the in-process monitoring during fiber laser welding as well as on the first paper. On the previous/formal study, we analyzed the change of emission signal on thin plate welding. On this study, however, we analyzed RMS and FFT with emission signals in laser welding on lap joint and butt joint of 8mm-thick 316L stainless steel. As the result, the movement of specific frequency peak was observed according to welding speed changes. Furthermore, frequency peak as a result of FFT on the thick plate welding are much clearer than on the thin plate welding. Therefore, it is expected that the welding parameter changes can be predicted in case of applying FFT to in-process monitoring.

• Corrosion Science and Technology
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• 제20권2호
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• pp.85-93
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• 2021

The corrosion damage of materials in marine environment mainly occurs by Cl^- ions due to the breakdown of passive films. Additionally, various characteristics in seawater such as salinity, temperature, immersion time, flow rate, and biological activity also affect corrosion characteristics. In this study, the corrosion characteristics of stainless steels (STS 304 and STS 316L) and anodized aluminum alloys (AA 3003 and AA 6063) were evaluated with seawater temperature parameters. A potentiodynamic polarization experiment was conducted in a potential range of -0.25 V to 2.0 V at open circuit potential (OCP). Corrosion current density and corrosion potential were obtained through the Tafel extrapolation method to analyze changes in corrosion rate due to temperature. Corrosion behavior was evaluated by measuring weight loss before/after the experiment and also observing surface morphology through a scanning electronic microscope (SEM) and 3D microscopy. Weight loss, maximum damage depth and pitting damage increased as seawater temperature increased, and furthermore, the tendency of higher corrosion current density with an increase of temperature attributed to an increase in corrosion rate. There was lower pitting damage and lower corrosion current density for anodized aluminum alloys than for stainless steels as the temperature increased.

• 한국정밀공학회지
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• 제13권5호
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• pp.53-59
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• 1996

Warm deep drawing of single-action dies using local heating has appeared to be an alternative attractive production method of multi-operation die sets generally used at room temperature in deep drawing of rectangular cup. Uniaxial tensile tests and deep drawing tests of various materials are carried out and the effect of temperature on tensile properties and drawability are examined at temperatures up to 200 .deg. C under three kinds of lubricants of teflon film, vinyl film and drawing oil. Good formability is achieved when punch and die temperature were differentiated intentionally in order to get large tensile strength(TS) at punch shoulder protion and small TS at die side. Throughout the experiments, it has been shown that the limiting drawing height of STS316L was increased with heating die and blank holder at 100 .deg. C, but that of STS430 wasn't. When vinyl or teflon film was attached on the plates, the drawability was increased considerably.

• 방사성폐기물학회지
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• 제17권1호
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• pp.15-28
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• 2019

고리 1호기는 원전해체 계획에 따라 영구정지 이후 가능한 한 빠른 시일 내에 원자로냉각재계통의 화학제염을 수행할 계획으로, 계통제염 기술 확보를 위해 한수원에서는 2014년부터 '원전 해체설계를 위한 냉각재계통 및 기기제염 상용기술개발' 연구과제를 통해 화학제염기술을 개발하고 있다. 본 연구를 위해 Lab. 규모 계통제염 공정장치를 제작하였으며, 계통제염 대상의 주요재료인 STS304, 316, 410, Alloy600, SA508을 사용하여 화학제염 공정실험을 수행하였다. 화학제염 공정실험의 목적은 산화-환원공정의 최적시간, 최적제염제 및 공정횟수를 도출하기 위함이다. 화학제염 공정실험은 과망간산-옥살산 기반의 단위공정 및 연속공정 실험, 과망간산+질산-옥살산 기반의 연속공정 실험으로 나누어 수행하였다. 그 결과 단위공정실험을 통해 최적공정 시간인 산화공정 5시간, 환원공정 4시간을 도출하였으며, 연속공정실험을 통해 최적제염제와 공정횟수를 도출하였다. 최적제염제는 산화제의 경우 $200mg{\cdot}L^{-1}$ 과망간산 + $200mg{\cdot}L^{-1}$ 질산이고, 환원제는 $2000mg{\cdot}L^{-1}$ 옥살산이며, 공정횟수는 STS304와 SA508의 경우 2 cycle, Alloy600의 경우 3 cycle 이상 수행하는 것이 적절할 것으로 평가되었다.

• Corrosion Science and Technology
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• 제4권6호
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• pp.226-230
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• 2005

Si incorporated diamond-like carbon (Si-DLC) films ranging from 0 to 2 at.% contents were deposited on STS 316L substrates for orthopedic implants by means of r.f. plasma-assisted chemical vapor deposition (r.f. PACVD) technique, using mixtures of benzene ($C_6H_6$) and silane ($SiH_4$) as the precursor gases. This study provides the reliable and quantitative data for assessment of the effect of Si incorporation on corrosion property in the simulated body fluid environment through the electrochemical test. It was found that corrosion to resistance of Si-DLC coatings with increasing Si content are improved owing to high $sp^3$ bonding.

• 한국생산제조학회지
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• 제22권5호
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• pp.795-799
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• 2013

This paper describes a novel hybrid surface polishing process combining non-traditional electrochemical polishing (ECP) with external artificial ultrasonic vibration. The purpose of this study is to develop an easier method for improving stainless steel surfaces. To this end, vibration electrochemical polishing (VECP), a novel ultrasonic manufacturing process, for enhancing electrochemical reaction and surface quality compared with that achieved using conventional ECP is suggested. In addition, for finding the optimized experimental conditions, the two methods are compared under various current densities. Localized roughness of the work material is measured with atomic force microscopy (AFM) and scanning electron microscopy (SEM) for obtaining detailed surface information.

• 대한기계학회논문집A
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• 제31권10호
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• pp.1046-1052
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• 2007

Elastic-plastic structural analysis for regenerative cooling chamber of gas generator was performed. Uniaxial tension test was conducted for STS316L at room and high temperature conditions to get the material data necessary for the structural analysis of the chamber which was operated under thermal load and high internal pressure. Physical properties including thermal conductivity, specific heat and thermal expansion were also measured. The structural analysis for four different types of regenerative cooling chamber of gas generator revealed that increased cooling performance decreased the thermal load and strain of the cooling channel structure. The results propose that in order for the regenerative cooling gas generator chamber to have high structural stability with endurance to high mechanical and thermal loads, it is important for the chamber to be designed to have high cooling performance.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.802-807
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• 2007

Elastic-plastic structural analysis for regenerative cooling chamber of gas generator was performed. Uniaxial tension test was also conducted for STS316L at room and high temperature conditions to get the material data necessary for the structural analysis of the chamber which is operated under thermal load and high internal pressure. Physical properties including thermal conductivity, specific heat and thermal expansion data were also measured. The structural analysis for four different types of regenerative cooling chamber of gas generator revealed that increased cooling performance decreases the thermal load and strain of the cooling channel. The results propose that in order for the regenerative cooling gas generator chamber to have high structural stability with endurance to high mechanical and thermal loads, it is important for the chamber to be designed to have high cooling performance.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.251-254
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• 2009

Thermal performance of a thermosiphon for medium-temperature solar thermal application was investigated. The working fluid was Dowtherm A and the container was made of STS 316L. The thermosiphon had a outer diameter of 12.7 mm and a total length of 2 m, where the evaporator and the condenser had the same length of 0.3 m and the adiabatic section was 1.4 m. Both the evaporator and the condenser were aligned horizontal with an elevation difference of 0.18 m to utilize the gravitational force for the working-fluid return. The optimum fill charge ratio of the working fluid was investigated to obtain the maximum heat transport with the lowest thermal resistance. The maximun input thermal load was 500 W and thermal resistance was $0.60^{\circ}C/W$.

• 한국분말재료학회지
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• 제11권4호
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• pp.288-293
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• 2004

The application concept of using a fail safety filter on the filtering system is to prevent the particle leakage when the main filter element is broken at high temperature. In this study, the metal filters were fabricated by pressureless sintering method. The mixture of stainless steel powders and filler metal binder solved in the water solutions of 5% PVA was compacted to form the cylindrical filter without pressure. The compacted filter were sintered in the vacuum sintering furnace at 120$0^{\circ}C$ for 1 hour. The metal filter(produced with powder of 640-840 ${\mu}m$ size) having more than above 50% porosity, 500${\mu}m$ pore size, and permeability of 7.3${\times}$10$^{-11}$m$^{2}$ plugged within 2.5 minute to prevent the leakage of maximum slip particle size of less than 3${\mu}m$.