• Journal of the Korean Society of Marine Environment & Safety
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• v.4 no.1
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• pp.49-56
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• 1998

The Microfiltration and Ultrafiltration were used to treat effluent of secondary municipal wastewater treatment system(Sequencing Batch Reactor). The cross-flow hollow fiber, UF 500,000(NMWC) and MF 0.65$\mu$ membrane were selected as suitable membrane. Short term and long term fouling effect were measured as a factor of flux decrease and the fouling removal effect of mixing air bubble in the penetrant was studied. The removal of anionic sulfactants before and after formation of micelle with several kinds of oil were checked. The test results show that removal of TOC was 70~80%, TN 28% and TP 16%. The decrease of flux due to fouling were 85%(UF) and 90%(MF) after running of 100hrs. The removal of anionic sulfactants were 60~70% notwithstanding micelle or not.

• Transactions of Materials Processing
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• v.10 no.3
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• pp.253-260
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• 2001

This study was performed to investigate the optimized warm forming conditions which gave the maximum drawing depth in square cup drawing of clad sheet metals, by changing the temperatures of die and blankholder and also shapes and materials of blanks. Two kinds of clad sheet metals, STS304-A1050-STS304 and STS304-A1050-STS430 were selected for experiments. The relative drawing depth of STS304-A1050-STS304 clad sheet was increased up to 4.4 at $150^{\circ}C$ that was 29% higher than at room temperature, whereas STS304-A1050-STS430 material was improved to 3.9 at $120^{\circ}C$ which was 15% better than at room temperature. In addition, comparison of wall thickness and hardness of a warm drawn cup with those of room temperature showed more even distributions. No separation between each laminated material after drawing occurred through inspection by microscope as well as application of penetrant test and bond strength test. Therefore, warm forming technique was confirmed to give better results in deep drawing of stainless clad sheet metal.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.4 no.3
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• pp.245-253
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• 2006

A test of the 1/3 scale model was conducted to verify the tip-over analysis of a dry. concrete storage cask under a hypothetical accident condition. The tip-over analysis was executed using the velocity at each point as the initial conditions of the model just before the impact. The initial velocity was determined from the initial angular velocity, which would make the equivalent kinetic energy to the potential energy. To confirm the structural integrity of the canister, the visual testing and the non-detective testings such as Liquid Penetrant testing and Ultrasonic Testing were conducted. The lid of a storage cask was plastically deformed near the impact point. The structural integrity of storage cask was maintained. To verify the tip-over analysis the strains and the accelerations acquired by the tip-over test were compared with those by the analyses. The results of the analysis were larger than the test results about two times.

• Plant Journal
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• v.7 no.1
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• pp.49-55
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• 2011

This study analyzed causes and status of cracks to suggest preventives for welding cracks generated on fillet welding zone of atmosphere corrosion resisting steel box girder. Penetrant testing, a sort of non-destructive testing, was conducted for inspection of crack status on welding zone. As a result of test, welding cracks were found on the point of start, center and end to fillet welding zone of 32 mm-thickness. The result of carbon equivalent composition of materials was 0.452%. According to welding specification, to preheat prevent welding crack, preheat temperature of $100{\sim}200^{\circ}C$ should be kept before welding execution. It was failed to keep preheat temperature because it had been executed on winter season and the structure of box girder had wide heat transfer area. As a result of examination of time varying preheating temperature of 32mm-thickness material, it was understood that preheat temperature of above $230^{\circ}C$ on both 130mm-long sides of welded joint can prevent welding crack.

• Journal of the Korean Society for Nondestructive Testing
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• v.35 no.5
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• pp.358-366
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• 2015

In this study, a nondestructive test (NDT) is performed to inspect the optimal design of a ground tracked combat vehicle for self-propelled artillery, tank, and armored vehicles. The minimum qualification required for personnel performing the NDT of a ground tracked combat vehicle was initially established in US military standards, and then applied to the Korean defense specifications to develop a ground tracked combat vehicle. However, the qualification standards of an NDT inspector have been integrated into NAS410 through the military and commercial specifications unification project that were applied in the existing aerospace/defense industry public standard. The design method for this study was verified by applying the optimal design to the liquid penetrant testing Al forging used in self-propelled artillery. This confirmed the reliability and soundness of the product.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.10 no.2
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• pp.105-115
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• 2012

Necessity of demonstration test to evaluate the structural integrity of a basket for accident conditions arose during license approval procedure for the WSPP's dry storage facility named MACSTOR/KN-400. A drop test facility for demonstration was constructed in KAERI site and demonstration tests for basket drop were conducted. As the upper welding region of a loaded basket was collided with a dropped basket during the drop test, the welding in this region was fractured and leakage happened after the drop test. The enhancement of basket design was needed since the existing basket design was not able to satisfy the performance requirement. The directions for design modification were determined and six enhanced designs were derived based on these directions. Structural analyses and specimen tests for each enhanced design were conducted. By evaluating structural analysis results and test results, one among six enhanced designs was decided as a final design for revision. The final design was the one to reduce the height of central post of a basket and to decrease the impact velocity with a dropped basket. Test basket models were fabricated with accordance with the final enhanced design. Additional demonstration test was performed for this test model and all the performance requirements were satisfied.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.10
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• pp.6282-6288
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• 2014

$CO_2$ welding is used widely in the field. On the other hand, welding defects occur when welders cannot adjust the current and voltage needed for welding and have to stop working to adjust the current and voltage, causing sudden cooling down of the welding structure inside a vehicle or tank where the control panel is invisible or when work site is far. This study used three types of existing $CO_2$ welders. This also applied SS400 rolled steel for welding structural purposes for remote control torch welding, perform a welding test through v-groove butt welding with a remote control torch and existing $CO_2$ welding torch, conducted visual inspection on the appearance of a welded top bead. In addition, the appearance quality of the welding part was monitored mainly through penetrant testing and a bending test to evaluate the welding defect reduction and the effect on the performance and compatibility by replacing the existing welder.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.192-196
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• 2005

Key part of main equipment in a gas turbine may be likely to be damaged due to operation under high temperature, high pressure, high-speed rotation, etc. Accordingly, the cost for maintenance increases and the damaged parts may cause generation to stop. The number of parts for maintenance also increases, but diagnostics technology fur the maintenance actually does not catch up with the demand. Blades are made of precipitation hardening Ni superalloy IN738 and the like for keeping hot strength. The surface of a blade is thermal-sprayed, using powder with main compositions such as Ni, Cr, Al, etc. in order to inhibit hot oxidation. Conventional regular maintenance of the coating layer of a blade is made by FPI (Fluorescent Penetrant Inspection) and MTP (Magnetic Particle Testing). Such methods, however, are complicated and take long time and also require much cost. In this study, defect diagnostics were tested for the coating layer of an industrial gas turbine blade, using an infraredthermography camera. Since the infrared thermography method can check a temperature distribution on a wide range of area by means of non-contact, it can advantageously save expenses and time as compared to conventional test methods. For the infrared thermography method, however, thermo-load must be applied onto a tested specimen and it is difficult to quantify the measured data. To solve the problems, this essay includes description about producing a specimen of a gas turbine blade (bucket), applying thermo-load onto the produced specimen, photographing thermography images by an infrared thermography camera, analyzing the thermography images, and pre-testing for analyzing defects on the coating layer of the gas turbine blade.