• 대한조선학회지
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• 제10권1호
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• pp.15-20
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• 1973

In this paper, it is desired to show a simplified analytical method in estimating the thermal stresses in the heat affected zone of butt welded joint. A finite strip as shown in Fig.1 is taken as a analytical model for stress analysis. Expressing the temperature distributions by Fourier series, the thermal stresses are obtained. From the numerical sample calculation, the following results can be obtained. (1) Thermal stresses can be estimated by the sujected method. (2) The stress component, which is parallel to the weld direction is the largest stress component in major part of the strip. (3) In obtaining a stress component for the engineering purpose, length of the strip can be treated as five times of the thickness with same degree of convergency.

• Journal of Welding and Joining
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• 제18권5호
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• pp.55-62
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• 2000

A metallurgical model for the phase transformation kinetics at Coarsened Grain Heat Affected Zone(CGHAZ) on the basis of Johnson-Mehl-Avrami equation(JMA equation) was proposed. In this model, the effect of prior austenite grain size on the transformation and the morphological changes of ferrite were considered. Isothermal dilatometer tests were performed to determine the effect of prior austenite grain size (AGS) on the austenite decomposition to ferrite and pearlite in a plain carbon steel. By comparing the calculated volume fraction with measured data, the reliability of the developed model was discussed.

• Journal of Welding and Joining
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• 제15권5호
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• pp.46-55
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• 1997

This study has evaluated the liquation cracking behavior in the heat affected zone of several Ni base superalloys (Incoloy 825, Inconel 718 and Inconel 600). 304 and 310S austenitic stainless steels were also included for comparison. In addition, the mechanism of liquation cracking in the HAZ was postulated based on the extensive microstructural examinations with SEM, EDAX and TEM. The liquation cracking resistance of Ni base alloys was found to be far inferior to that of austenitic stainless steels. The liquation cracking of Incoloy 825 and Inconel 718 was believed to be closely related with the Laves-austenite(Ti rich in 825 and Nb rich in 718) and MC-austenitic eutectic phases formed along the grain boundaries by constitutional liquation and incipient melting under rapid welding thermal contraction. Further, liquation cracking resistance of the HAZ was dependent not only upon the type and amount of low melting phases but also on the grain size.

• Journal of Welding and Joining
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• 제12권2호
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• pp.108-118
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• 1994

In the present study, the dynamic crack initiation toughness and total absorbed energy behavior of Heat Affected Zone(HAZ) was experimentally evaluated for SS41 steel welding. The materials were submerged arc-welded SS41 steel plate with thickness 19mm. The test temperature range was from $20^{\circ}C$(room temperature) to $-70^{\circ}C$ The HAZ of welding were divided into three sub-zones for analysis; H1, H2, H3, according to the distance from the fushion line. From the experimental studies, the reference value of dynamic crack initiation toughness $(J_{Id(R)})$ can be use to estimate dynamic fracture toughness characteristics of steel welding.

• 한국해양공학회지
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• 제10권2호
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• pp.69-76
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• 1996

In-process quality control and high reliability of the weld are the major concerns in applying friction welding to the economical and qualified mass-production. Experimental examinations and quantitative analysis were performed for the optimiaztion of similar friction welding of hydraulic valve spool steels(SNCM220, SCM435, SACM645, SCM415, ${\varphi}24). The quantitative correlations were found between the initial cumulative counts of acoustic emission(AE) occurring during plastic deformation periods of the welding and the fatigue life as well as weld strength and welding conditions. A real-time evaluation system was developed for the friction weld quality by AE.

• 한국해양공학회지
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• 제20권2호
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• pp.41-45
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• 2006

Arc welding is sometimes used to repair damaged cast iron parts in diesel engine for driving n ship. In this case cold arc welding is good for saving the time and results in good repairing. But if some difference in hardness on welding zones made with AWS E Ni-CI and NiFe-CI happen, repaired parts would be cracked in a short. In order to overcome this default, the study is performed on varying preheating temperature of welding parts, selecting welding rod and welding work way. The result will be used on ship's working shop.

• 한국해양공학회지
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• 제13권2호통권32호
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• pp.66-73
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• 1999

This paper presents the experimental examinations and statistical quantitative analysis of the correlation between the cumulative counts of acoustic emission(AE) during plastic deformation periods of the welding and the tensile strength and other properties of the tube-to-tube welded joints of O.D. 30mm (I.D 18mm) nozzle steel. This is a new approach which attempts finally to develop real-time quality monitoring system for friction welding. And this study results in practical possiblility of real-time quality control more than 100% joint efficiency showing good weld no micro structural defects.

• 한국안전학회지
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• 제16권3호
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• pp.19-25
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• 2001

The friction-welding SM25C is a substitute for the suing steel that is utilized in the machinery, airplane, and automobile, ok. This substitution would provide reduction of material and weight of welding parts. From the result we found that the strength of the friction welded joint was 529-617MPa and the toughness 1.2 times higher than that of the base metal. The optimal condition of friction welding was found as follows : n=2000rpm, $P_1$=68㎫, $P_2$=137MPa, $t_2$=2sec, $t_1$=2-4sec, Considering the strength, the hardness, and the reduction of area in the friction welding, the fiction welding using SUP9A and SM25C was found to cause no problem in on-the-job application.

• Corrosion Science and Technology
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• 제6권2호
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• pp.77-81
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• 2007

Fault current can be discharged from power transmission tower due to lightning or inadvertent contact of crane, etc. Pipelines in proximity to either the source of the ground fault or the substation grounding grid may provide convenient conductive path for the fault current to travel. Inappropriate measures to the neighboring pipelines against the fault current may cause severe damages to the pipes such as coating breakdown, arc burn, puncture, loss in wall thickness, or brittle heat-affected zone. Like inductive and conductive AC coupling, steadily induced fault current right after the coating breakdown can lead to corrosion of the pipeline. In this work, some protection guidelines against fault currents used in the field have been validated through the simulation and analytical method.

• 한국기계가공학회지
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• 제11권6호
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• pp.75-81
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• 2012

Dissimilar material friction welding such as STD11 and SCM440, we are considering of such things as strength and tenacity of welding interface, which consist of friction welding rotation frequency, friction heating pressure, upset forging-pressure, friction heating time, and upset forging-pressure time. From the study, obtaining the interrelationship between welding condition and quality(toughness, tenacity), we can set the best range of welding condition. while performing acoustic emission examination for the nondestructive evaluation, we can deduce the interrelationship among total acoustic emission counts, friction welding variable, and quality during friction welding, which can solve the manufacturing difficulty and enhance the economic value.