• Tribology and Lubricants
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• v.25 no.6
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• pp.374-380
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• 2009

This paper presents the stress and displacement characteristics of oil pipe using the finite element analysis. Displacement in axial direction and von Mises stress of a pipe were analyzed with three design factors, which are the pipe thickness, the corrugation pitch and the corrugation height, under uniform oil pressure. The FE computed results are presented between a conventional round pipe and a rectangular pipe, which is manufactured in this study. The computed FE results show that maximum displacement in axial direction and von Mises stress of pipe are increased linearly as the oil pressure increases. Also, they are increased linearly as the corrugation pitch, corrugation height and pipe thickness increases. von Mises stress of a rectangular pipe at the edge increases sharply compared with that of a conventional round pipe. Therefore, the strength of rectangular pipe is superior to that of a conventional round pipe.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.436-439
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• 2008

This paper is to research the heat transfer performance of the sintered pipe. Recently, oil prices is to be 127 $ per barrel, we expect higher costs this summer. We promote alternative fuels, after oil and gasoline prices reached record highs. The governments have made efforts to avoid future crisis by continuing the move toward renewable energy and energy saving. In this paper, we have fabricated a sintered pipe, the heat transfer performance of sintered pipe is achieved experimentally. The pipe is copper tube of outer diameter of 15.88 mm, the length of the pipe is 800 mm. Based on the experimental results, it is shown the overall heat transfer coefficient of sintered pipe is increased as compared with that of a straight pipe, is equal as compared with that of a spiral pipe. The overall heat transfer coefficient was $0.075{\sim}0.09\;kW/^{\circ}C$

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.10
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• pp.894-900
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• 2000

The experimental study for performance improvement of aluminum/freon22 grooved heat pipe was carried out. Arterial wick was used for performance improvement of heat pipe. The experimental result was compared with screen covered grooved wick heat pipe. And also, performance test of grooved wick thermosyphon inserted straight wire in the center of grooved pipe was carried out. This result was compared with the performance test result of grooved wick thermosyphon. The operation limit of artery inserted grooved heat pipe was slightly extended, but thermal resistance of this heat pipe was twice as large as that of screen covered grooved heat pipe. In case of thermosyphon, the operation limit of grooved thermosyphon inserted straight wire in the center of grooved pipe was slightly extended, but thermal resistance was increased, comparing with that of the grooved thermosyphon.

• Journal of the Earthquake Engineering Society of Korea
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• v.26 no.1
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• pp.13-22
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• 2022

This study proposes a low-cycle fatigue life derived from measurement points on pipe elbows, which are components that are vulnerable to seismic load in the interface piping systems of nuclear power plants that use seismic isolation systems. In order to quantitatively define limit states regarding leakage, i.e., actual failure caused by low-cycle fatigue, in-plane cyclic loading tests were performed using a sine wave of constant amplitude. The test specimens consisted of SCH40 6-inch carbon steel pipe elbows and straight pipes, and an image processing method was used to measure the nonlinear behavior of the test specimens. The leakage lines caused by low-cycle fatigue and the low-cycle fatigue curves were compared and analyzed using the relationship between the relative deformation angles, which were measured based on each of the measurement points on the straight pipe, and the moment, which was measured at the center of the pipe elbow. Damage indices based on the combination of ductility and dissipation energy at each measurement point were used to quantitatively express the time at which leakage occurs due to through-wall cracking in the pipe elbow.

• Journal of the Korean Institute of Gas
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• v.15 no.4
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• pp.39-43
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• 2011

In this study, the stress and deformation behavior characteristics of a flexible joint for a gas pipe have been analyzed by a finite element method. These characteristic results may investigate the strength safety analysis of a flexible joint, which is composed by a spiral corrugation pipe or a rectangular corrugation model and a plane pipe. The FEM computed results show that an optimized spiral corrugation pipe model is a inclined angle of $4.7^{\circ}$ and a corrugation height of 1.5mm. And also, a rectangular corrugation pipe model of $90^{\circ}$ is recommended in strength safety rather than a spiral corrugation pipe with an inclined angle. Thus, a corrugated pipe for an increased strength safety is to recommend a reduced pitch and curvature radius of an inclined corrugation.

• International Journal of Air-Conditioning and Refrigeration
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• v.12 no.1
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• pp.1-9
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• 2004

The purpose of the present study is to examine the heat transport limitations in a screen mesh heat pipe for electronic cooling by theoretical analysis. Diameter of pipe was 6mm, and mesh numbers were 50, 100, 150, 200 and 250, and water was investigated as working fluid. According to the change of mesh number, wick layer, inclination and saturation temperature, the maximum heat transport limitations by capillary, entraintment, sonic and boiling were analyzed by a theoretical design method of heat pipe, including capillary pressure, pumping pressure, liquid friction coefficient in wick, vapor friction coefficient, etc. Based on the results, the capillary limitation in a small diameter of heat pipe is largely affected by mesh number and wick layer. Mesh number of 250 is desirable not to be used in pipe diameter of 6 mm, because capillary heat transport limitation decreases by the abrupt increase of liquid friction pressure due to the small liquid flow area. For the heat transport of 15 watt in 6mm diameter pipe, mesh number of 100 and one layer is an optimum wick condition, which thermal resistance is the smallest.

• Structural Engineering and Mechanics
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• v.84 no.3
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• pp.337-344
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• 2022

Due to corrosion defects on the surface of the oil pipe, the sealing performance of the annular blowout preventer (BOP) decreases, and the leakage of toxic and harmful gases such as H₂S and SO₂ will threaten the safety of operators on the well. Therefore, this paper establishes the FE model for evaluating the sealing performance of BOP-oil pipe corrosion defects, which is based on the rubber large deformation theory and rubber core sealing mechanism, and designs the experiment of BOP sealing performance to verify the accuracy of the FE model. The sealing performance of BOP sealing oil pipe with corrosion defects is studied. The research results show that the sealing performance of BOP is more sensitive to the axial size of corrosion defects. With the increase of oil pipe outer diameter, the critical size of defects increases continuously. The sensitivity of radial and depth dimensions is low, When for 88.9 mm outer diameter oil pipe, the axial critical size of corrosion defect is 20 mm, the radial critical size is 16 mm and the critical depth is 2 mm. Fit the formula between the outer diameter of oil pipe and the piston increment. According to the formula, the operator can calculate the piston stroke increment required by the BOP to complete the sealing when the oil pipe is corroded.

• Journal of the Korean Society for Precision Engineering
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• v.8 no.1
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• pp.41-49
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• 1991

A knowledge of the resdual stress distribution at circumferential weldments can normally increase the accuracy of a fracture assessment in pipe line. In this paper, we present the measurements about the residual stress distributions at three kinds of circumferential butt welded pipes using the holl drilling strain gage method. By this experiment, we have obtined the following characteristics. At the inner surface of the pipe region near the center line of welding is under high tensile residual stress. However, as the distance from the center line of welding increases, the tensile component decreases and finally becomes compressive residual stress at region far away from the center line of welding. The longitudinal residual stress at the outer surface is compressive regardless of the diameter of pipe and the circumferential stress is changed from compressive to tensile as pipe diameter increases. The results also demonstrate that the residual stress is mainly caused by self-restraint bending force in the pipe welding.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.6
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• pp.512-518
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• 2008

Guided wave technology is advantageous for fast inspection of pipe wall thinning since the guided wave propagates long distance. In this investigation, the method to evaluate gradual wall thinning in a pipe based on the arrival time delay with magnetostrictive patch transducers is presented. Low frequency A0 Lamb waves were generated and measured by the present transducer and it was applied to arrival time delay measurement experiments on a test pipe having gradual wall thinnings artificially manufactured. From experiments, consistent results that wall thinning increases the arrival time delay of A0 waves were obtained. Consequently, the feasibility of the magnetostrictive patch transducers to evaluate wall thinning was verified.

• Corrosion Science and Technology
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• v.17 no.6
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• pp.279-286
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• 2018

Austenitic stainless steels used in nuclear power plants mainly use pipes made of seamless pipes, which depend on imports. The manufacturing process and high cost are some of the problems associated with seamless pipes. Therefore, in this study, the corrosion characteristics of the seamless pipe and the SAW pipe were assessed to determine the safety and reliability of the SAW pipe in a bid to replace the seamless pipe. Microstructure was analyzed using an optical microscope and the degree of hardness was measured using a Rockwell B scale. Intergranular corrosion resistance was evaluated by ASTM A262 Practice A, C, and E methods. The degree of sensitization was determined using a DL-EPR test. Anodic polarization test was performed in deaerated 1% NaCl solution at $30^{\circ}C$ and the U-bend method was used to evaluate the SCC resistance in 0.01 M $Na_2S_4O_6$ at $340^{\circ}C$ and 40% NaOH solution at $290^{\circ}C$. Weld metal of the SAW pipe specimen showed relatively high degree of sensitization and intergranular corrosion rate. However, annealing to SAW pipes improved the corrosion properties in comparison to that of the seamless pipe.