• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1116-1120
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• 2004

In the nuclear power plant, there are several cylindrical vessels such as reactor vessel, pressuriser and so on. The vessels are usually constructed by welding large rolled plates, forged sections or nozzle pipes together. In order to assure the integrity of the vessel, these welds should be periodically inspected using sensors such as ultrasonic transducer or visual cameras. This inspection is usually conducted under water to minimize exposure to the radioactively contaminated vessel walls. The inspections have been performed by using a conventional inspection machine with a big structural sturdy column, however, it is so huge and heavy that maintenance and handling of the machine are extremely difficult. It requires much effort to transport the system to the site and also requires continuous use of the utility's polar crane to move the manipulator into the building and then onto the vessel. Setup beside the vessel requires a large volume of work preparation area and several shifts to complete. In order to resolve these problems, we have developed an underwater mobile robot guided by the laser pointer, and performed a series of experiments both in the mockup and in the real reactor vessel. This paper introduces our robotic inspection system and the laser guidance of the mobile robot as well as the results of the functional test.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.4
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• pp.532-540
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• 2012

In this study, some considerations have been suggested in developing on-site techniques to evaluate the sensitization of stainless steels. Electrochemical potentiokinetic reactivation (EPR) technique is known to be a candidate tool for field applications since it enables quantitative assessment in reasonable test time, compared to oxalic etching (ditch) technique. The on-site application of the test method imposes additional restrictions on the selection of the test method (for example, minimum surface preparation requirement, insensitivity to testing temperature, etc.). The EPR and etching techniques have been compared in order to sensitization of stainless steel structures. It has been widely reported that the maximum sensitivity in the welded structure of stainless steel is shown at heat-affected zone (HAZ) than weldments with cast structure. In this work, sectioned weldments and external surfaces were investigated to reveal the degree of sensitization by the etching and the results were compared with those of EPR test. The EPR test showed little sensitivity to surface roughness and test temperature.

• Journal of Environmental Health Sciences
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• v.3 no.1
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• pp.27-44
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• 1976

This study was carried out to evaluate the harmful factors in working environments and to investigate the labor productivity after improvement of environments, surveying 93 industrial establishments of 10 industries located in Youngdeungpo industrial area in Seoul. The results obtained were as follows: 1) The highest noise level of 125dB(A) was indicated at the rolling process of transport equipment manufacturing industry. 2) The best illumination level was shown in precise machinery industry and the worst was indicated in rubber products, metallic products and transport equipment manufacturing industries. 3) Thermal conditions were above threshold limit value (TLV) at more than two processes of all industries except printing industry. 4) The highest dust concentration was determined in textile and wearing manufacturing industry. 5) Organic solvents were detected at 52 processes in 93 industrial establishments and 33 processes of them showed higher than TLV. The results about harmful chemicals were as follows: a) sulfur dioxide ($SO_2$)was determined higher than TLV on welding process of metallic product manufacturing industry and heat treatment process of transport equipment manufacturing industry. b) Carbon monoxide (CO) concentration was 700ppm at heat treatment process of transport equipment manufacturing industry, indicating 14 times of TLV. c) vinylchloride concentration in the air of PVC raw material mixing process and PVC preparation process of chemical product manufacturing industry was determined higher than TLV. d) Hydrochloride (HCl) concentration in the air of wire expanding process of transport equipment manufacturing industry was determined higher than TLV. 7) Higher values of lead concentration than TLV were determined at lead welding metallic product manufacturing industry and type planting process of process of printing industry, $1.8mg/m^3$ and $0.3mg/m^3$ respectively. 9) 22, 968 of 52, 855 workers (i.e. 43.5%) in 93 industries were exposed to various harmful agents. 10) It was found that the improvement of illumination in electric apparatus manufacturing industry (from 20~40 lux to 420 lux) resulted in an increase in productivity of 6.5% per capita and a decrease in faulty products of 19%. 11) Improvement of environments using local exhaust ventilation system resulted in a decrease of harmful substances lower than TLV and an increase in productivity of 11.4%. 12) Improvement of shovelling tools based on ergonomics resulted in a reduction in energy expenditure of 25.3% and an increase in productivity of 32.2% per capita.

• Corrosion Science and Technology
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• v.6 no.5
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• pp.219-226
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• 2007

Pre-construction primer (PCP), or shopprimer, have been applied to steel plates to control temporary corrosion during ship fabrication. For surface preparation at ship block stage, in common shipyard practices, welding beads, burnt and rusted areas shall be blasted or power tool cleaned and the contamination such as zinc salt shall be removed with blasting or power tool. Whereas, the sound film of PCP needs not to be removed or roughened as the paint having good compatibility with PCP is used for the first coat. In many cases, however, full blasting or sweep blasting on the sound PCP treated block assemblies was requested. There still has been argument about the legitimacy of this practice, thus, it is critical to evaluate the quality of the coating system applied on the sound PCP retained condition, comparing with the one applied on the full blasted or sweep blasted condition. In this study, two different epoxy systems for water ballast tank were applied on the surfaces with sound PCP condition, full blasted condition, and sweep blasted condition. Coating performances such as durability, anti-corrosion, cathodic disbondment resistance were evaluated. The test results clearly indicated that the sound film of PCP needed not to be removed or roughened as the paint having good compatibility with PCP based on inorganic zinc silicate.

• Advances in aircraft and spacecraft science
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• v.11 no.1
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• pp.83-103
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• 2024

Adhesive bonding is currently widely used in many industrial fields, particularly in the aeronautics sector. Despite its advantages over mechanical joints such as riveting and welding, adhesive bonding is mostly used for secondary structures due to its low peel strength; especially if it is simultaneously exposed to temperature and humidity; and often presence of bonding defects. In fact, during joint preparation, several types of defects can be introduced into the adhesive layer such as air bubbles, cavities, or cracks, which induce stress concentrations potentially leading to premature failure. Indeed, the presence of defects in the adhesive joint has a significant effect on adhesive stresses, which emphasizes the need for a good surface treatment. The research in this field is aimed at minimizing the stresses in the adhesive joint at its free edges by geometric modifications of the ovelapping part and/or by changing the nature of the substrates. In this study, the finite element method is used to describe the mechanical behavior of bonded joints. Thus, a three-dimensional model is made to analyze the effect of defects in the adhesive joint at areas of high stress concentrations. The analysis consists of estimating the different stresses in an adhesive joint between two 2024-T3 aluminum plates. Two types of single lap joints(SLJ) were analyzed: a standard SLJ and another modified by removing 0.2 mm of material from the thickness of one plate along the overlap length, taking into account several factors such as the applied load, shape, size and position of the defect. The obtained results clearly show that the presence of a bonding defect significantly affects stresses in the adhesive joint, which become important if the joint is subjected to a higher applied load. On the other hand, the geometric modification made to the plate considerably reduces the various stresses in the adhesive joint even in the presence of a bonding defect.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.6
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• pp.646-652
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• 2014

Data of pollution incidents which occurred in shipyards of South Korea for 10 years from 2004 to 2013 were collected and analyzed in order to propose the plans for the prevention of pollution incidents in shipyards. Total number of pollution incidents in shipyards was 103 cases over the nation of Korea for the recent 10 years and the average annual number was about 10 cases, and annual cases tended to increase from 8 cases in 2004 to 23 cases in 2010 and then to decrease to 9 cases in 2013. The location data of pollution incidents showed 32 cases in Busan metropolitan city (31%), 30 cases in Jeonnam (29%), 21 cases in Gyeongam (21%), 5 cases in Jeju (5%), 4 cases in Gangwon (4%), 4 cases in Gyeongbuk (4%), 3 cases in Chungnam (3%) and 3 cases in Incheon metropolitan city (3%). According to the data of work types of shipyards, 60 cases happened during the work of ship repair (58%), 25 cases during the work of ship breakup (24%), 10 cases in the course of ship building (10%) and 8 cases by others (8%). The data of pollutant type showed oil and oily mixtures to be 59 cases (57%), waste paint dust to be 22 cases (21%), iron dust and welding slag to be 13 cases (13%), wastes to be 4 cases (4%), waste FRP powder to be 3 cases (3%), and others to be 2 cases (2%). The plans for the prevention of pollution incidents in shipyards of Korea were proposed as follows; (1) Observance of the related laws and regulations, (2) Establishment and implementation of action plans to prevent areas dense with shipyards from causing pollution incidents, (3) Establishment and implementation of oil pollution prevention plans in shipyards, especially during the ship repair and breakup works, (4) Preparation of measures to solve civil complaints against pollution incidents in shipyards, and (5) Improvement in national management for the control of shipyards.