• Nuclear Engineering and Technology
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• v.56 no.4
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• pp.1244-1249
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• 2024

A combination of flow-accelerated corrosion (FAC) tests and corresponding computational fluid dynamics (CFD) tests were performed to determine the hydrodynamic parameters that could help predict the highly susceptible location to FAC in the elbow section. The accelerated FAC tests were performed on a specimen containing elbow sections fabricated using commercial 2-inch carbon steel pipe. The tests were conducted at flow rates of 9 m/s under the following conditions: water temperature of 150 ℃, dissolved oxygen <5 ppb, and pH 7. Thickness reduction of the specimen pipe due to FAC was measured using ultrasonic testing. CFD was conducted on the FAC test specimen, and the turbulence intensity, and shear stress were analyzed. Notably, the location of the maximum hydrodynamic parameters, that is, the wall shear stress and turbulent intensity, is also the same location with maximum FAC rate. Therefore, the shear stress and turbulence intensity can be used as hydrodynamic parameters that help predict the FAC-induced wall-thinning rate. The results provide a method to identify locations susceptible to FAC and can be useful for determining inspection priority in piping systems.

• Korean Journal of Materials Research
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• v.19 no.9
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• pp.473-480
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• 2009

In order to provide the mechanism of nozzle clogging, recovered nozzles for high strength steel grade were examined carefully after continuous casting. The thickness of clogged material in SEN is increased in the following order: from the bottom to the top of the nozzle, upper part of slag line, and the pouring hole. Nozzle clogging material begins to form due the adhesion of metal to nozzle wall, the decarburization, and reduction of oxide in the refractory by Al and Ti in the melt. The reduction of oxide in the refractory by Al and Ti improves the wettability of the melt on the refractory and forms a thin Al-Ti-O layer. Metal containing micro alumina inclusions is solidified on the Al-Ti-O layer, and the solid layer grows due to the heat evolution through the nozzle wall. Thermodynamic calculation has been made for the related reactions. The effect of superheat to the nozzle clogging is discussed on ultra low carbon steel and low carbon steel.

• Transactions of Materials Processing
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• v.10 no.4
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• pp.329-337
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• 2001

The finite element simulation model and the program to calculate the reverse moment have been developed to analyse the stress state and deformation of pipe bending using local induction heating with small bending radius in this study. The reverse moment that is to be applied on the bending arm to control the wall thinning ratio of the bending outside to within a particular value. Even though the demand of pipes with small bending radius is increasing in power plants and ship buildings, the welded elbows are still widely used. The bending process with or without a reverse moment acting on the bending arm has been simulated. The reverse moments calculated from the developed program are in good agreement with the finite element simulations and the experiments.

• Restorative Dentistry and Endodontics
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• v.16 no.2
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• pp.174-181
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• 1991

A model system was used which enabled the same root canal system to be measured before and after coronal flaring of 51 extracted mandibular molars. The concavity of the distal surface of the mesial root was measured and the amount of reduction was compared after coronal flaring using step-back flared preparation, Gates-Glidden dirll or ultrasonic system(Quick-$\varepsilon$) at the furcation and apical 3mm from the furcation. The results were as follows: 1. The mean concavity of mesial root of manchbular molar was $0.73{\pm}0.27mm$ at the bifurcation and $0.65{\pm}0.23mm$ at the 3.0mm apical from the bifurcation. 2. The thickness of the root canal wall of the mesiobuccal canal was $1.08{\pm}0.26mm$ at the bifurcation and $1.00{\pm}0.23mm$ at the 3.0mm apical from the bifurcation. 3. The thickness of the root canal wall of the mesiolingual was $1.09{\pm}0.21mm$ at the bifurcation and $0.98{\pm}0.29mm$ at the 3.0mm apical from the bifurcation. 4. In the amount of reduction at the furcation and at the 3.0mm apical from the furcation there was no statistically significant difference between the step-back preparation and Gates-Glidden drill preparation, and ultrasonic preparation(P>0.05).

• Design & Manufacturing
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• v.12 no.3
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• pp.25-30
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• 2018

Recently The automotive industry is trying to increase the energy efficiency by reducing the weight of the car body and engine components as a way to achieve high energy efficiency. In particular, the reduction of the weight of the vehicle through the weight reduction of the vehicle body has the advantage that the fuel consumption and the output can be improved. But at the same time, there is the disadvantage that the strength becomes weak due to the reduction of the material thickness. Therefore, in order to overcome these disadvantages, materials with high strength according to the unit thickness have been actively developed, and researches for applying them have also been increasing. In this study, we will investigate the application of cold rolled steel sheet, which is a lightweight material, to a horn bracket that secures a installed in an automobile engine room. The horn bracket secures the horn on the car engine and is bolted to the outer wall of the engine. The momentum is acted on the bracket due to the distance between the bolt fastening part and the car horn installed on the bracket end side. Therefore, the body part of the bracket is more likely to be destroyed by the influence of the continuous stress. In this paper, design optimization for weight reduction and strength enhancement was performed to solve this problem, and possibility of applying the rolled steel sheet material as lightweight material by tensile test and fabrication was confirmed.

• Nuclear Engineering and Technology
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• v.35 no.2
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• pp.144-153
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• 2003

The object of this paper is the probabilistic failure analysis on the cladding performance of WPF(Whole Pin Furnace) test fuel pins under transient conditions, and analysis of the KALIMER fuel pin using the preceding analysis. The cumulative damage estimation and Weibull probability estimation of WPF test are performed. The probabilistic method was adapted for these analyses to determine the effective thickness thinning due to eutectic penetration depth. In the results, it is difficult to assume that a brittle layer depth made by eutectic reaction is all of the thickness reduction due to cladding thinning. About 93% cladding thinning of the eutectic penetration depth is favorable as an effective thickness of cladding. And the unreliability of the KALIMER driver fuel pin under the same WPF test condition is lower than that of the WPF pin because of the higher plenum-fuel volume ratio and lower cladding inner radius vs. thickness ratio. KALIMER fuel pin developed from conceptual design has a more stable transient performance for a failure mechanism due to fission gas buildup than the WPF pin.

• Corrosion Science and Technology
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• v.20 no.6
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• pp.403-411
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• 2021

In this study, the reliability of a commercial ER-type corrosion sensor was evaluated under an accelerated corrosion environment to verify its suitability for application in monitoring of ship's seawater piping system. A closed-loop pump piping testbed was designed and constructed to compare the wall thickness reduction of the pipe and the response from the sensor. The sensor was attached inside the pipe near the outlet of the pump that was exposed to a 3.5% NaCl solution with or without copper accelerated acetic acid (CASS). The results demonstrated that the presence of CASS significantly increased the corrosivity of the solution as well as the thickness reduction of the pipe, as expected. On the other hand, the corrosion products formed by the solution with CASS were thicker compared with those without CASS. The sensor response to temperature variation was found to be a clear linear relationship for the solution without CASS but there was a non-linear relationship where CASS was present.

• International Journal of Internet, Broadcasting and Communication
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• v.16 no.1
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• pp.176-181
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• 2024

The desktop-level 3D printing machines makes it easier for independent designers to produce collectible models. Desktop 3D printers that use FDM (Fused Deposition Modeling) technology usually use a minimum nozzle diameter of 0.4mm. When using FDM printers to make Gunpla models, Thin slice structures are prone to slicing errors, which lead to deformation of printed objects and reduction in structural strength. This paper aims to analyze the printing model that produces errors, control a single variable among the three variables of slice layer height, slice wall thickness and filament type for comparative testing, and find a way to avoid gaps. To provide assistance for using FDM printers to build models containing thin-walled structures.

• Journal of the Korean Geosynthetics Society
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• v.22 no.3
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• pp.11-25
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• 2023

In this study, the design and numerical analysis method of the inclined self-supported wall using cement treated soil were studied. In the case of the inclined self-supported wall, the active earth pressure decreased due to the decrease in the coefficient, Ka according to the slope (angle) and the weight decreasing effect, thereby increasing the overall stability. The wall with the slope caused a change in failure mode from overturning to sliding on the excavation side, and the optimal slope was evaluated to be about 10°. Compared to the strength reduction method, the overall stability in numerical analysis results in conservative results in limit equilibrium analysis, so it was found that this method should be attended when designing. As a result of the parameteric study, the stability on bearing capacity and compression failure did not significantly increase above the slope of 10° when the surcharge was small (about 20kPa or less). In the case of cohesion of the backfill, The results similar to numerical analysis were found to consider cohesion. It was evaluated that stability on sliding, oveturning, shear, and tension failure increases in proportion to the thickness of the wall, but there is no significant change in the stability on the bearing capacity and compressive failure regardless of the thickness of the wall above a certain angle (about 10°).

• Progress in Superconductivity and Cryogenics
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• v.23 no.4
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• pp.14-18
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• 2021

The Mg-Powder-Compaction (MPC) process is proposed to fabricate the MgB₂ superconducting wires. Mg powder wall, similar to the Mg metal tube, inside the Nb outer sheath has been made and the stochiometric B powder was inserted into the wall. Even though the very high MgB₂ core density of 2.53 g/cm³ is obtained, the superconducting area fraction of MgB₂ is not high enough for the applications. In this work, an advanced MPC process was adopted by adding Mg powder into B powder. The Mg powder wall in the initial wire was fabricated by controlling the wall thickness while maintaining a constant density, and the mixture of B and Mg powder was filled into the Mg powder wall with the same filling density. It is found that the reduction in the area of the Mg powder wall proceeds similar to the wire, and the Mg powder wall is well maintained at the final wire diameter, which is advantage for the fabrication of long wires. With the advanced MPC process, as the added Mg is increased the densities of MgB₂ core is decreased and the porous structure is formed, it is found that the area fraction of superconducting MgB₂ increase up to the 37.7 % with the improved high critical current density (J_c) and the engineering critical current density (J_e).