• 한국해양공학회지
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• 제11권2호
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• pp.57-69
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• 1997

The objetive of this study is to compare the mechanical proprties of 6000 series Al-Mg-Si aluminum alloy (AC120) with 5000 series Al-Mg aluminum alloy (TG25), and to investigate the influence of corrosion solution for fatigue life. Comparing of TG25 and AC120 alloy sheets, TG25 alloy sheets showing higher plastic ratio and total elongation have better formability than AC120 alloy sheets. The hardness of nugget area was a little higher than that of base metal area. Also, grain coarsening was observed in HAZ(Heat Affected Zone). In a corrosion fatigue experiment, the fatigue life decreased as concentration increased, when a dipping time was constant. The life decreased as dippling time increased, when a concentration was constant.

• 한국생산제조학회지
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• 제9권5호
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• pp.96-104
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• 2000

This paper represents to develop a computer software system which is capable to analyze the phase transformation of high strength steel(BV-AH32) and to predict heat transfer and welding residual stress due to phase transformation during Gas Metal Arc(GMA) welding. The developed model was considered temperature dependent properties such as young's modules, coefficient of thermal expansion and yield stress as well as the double ellipsoidal heat distribution by the moving arc. From the results, it was found that the longitudinal and transverse residual stresses calculated by the coupled analysis of heat transfer, residual stress and phase transformation showed good agreement with the experimental data. In addition, the temperature distribution as well as longitudinal and transverse residual stresses of weldment by the 1-pass and 2-pass of welding were also determined.

• Journal of Welding and Joining
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• 제4권3호
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• pp.43-49
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• 1986

Weldability of the TMCP steel manufactured by controlled rolling followed by accelerated cooling process was investigated. For comparison, two other steel plates produced by different manufacturing processes were selected; normalized and controlled rolled. Tandem submerged arc welding with both side one run technique was carried out. The results of this study can be summarized as follows; TMCP steel having the lowest carbon equivalent shows the best combination of mechanical properties, not only in the base metal but also in the heat affected zone. In the HAZ, the accelerated colling effect imarted on the trengthis releved by the weld thermal cycles, and thus the strength of the welded joint decrease substantially accompanied with the fracture in the HAZ. On the other hand, not only the softening but the fine microstructure can preserve the high toughness of TMCP steel in the HAZ.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1999년도 특별강연 및 추계학술발표대회 개요집
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• pp.310-313
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• 1999

This paper represents to develop a computer software system which is capable to analyze the phase transformation of high strength steel(BV-AH32) and to predict heat transfer, residual stress due to phase transformation during Gas Metal Arc(GMA) welding. The developed model was taken into account temperature dependent of young's modules, coefficient of thermal expansion and yield stress as well as the double ellipsoidal heat distribution by the moving arc. The results showed that the longitudinal and transverse residual stresses calculated by the coupled analysis of heat transfer, residual stress and phase transformation are in good agreement with the experimental data. In addition, the temperature distribution as well as longitudinal and transverse residual stresses of weldment were determined at the 1-pass and 2-pass of welding.

• Journal of Welding and Joining
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• 제10권1호
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• pp.20-34
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• 1992

Characteristics of two correcting methods, a new Autogeneous GTAW heating (TIG) method and the conventional GMAW bead-on plate welding(MIG) method, for distorted aluminum fabrication structures were studied. As a result of microscopic study of Autogeneous GTAW heating and GMAW bead-on plate welding areas, porosities in weld metal and surface cracks in local heating zone were found. Through the mechanical tests, it was verified that porosities decrease tensile strength and surface of distortion, angular displacement and transeverse shrinkage were measures and compared. In order to investigate changes of material properties in heating area and cause of defects such thermal stresses were calculated by ADINA. Through the computations of transient thermal stresses and microscopic observation of fracture surface, thermal stress was found to be the cause of crack during Autogeneous GTAW heating.

• 한국생산제조학회지
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• 제4권4호
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• pp.25-32
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• 1995

This study is to inspect the influence of the initial residual stress on fatigue crack growth behavior after the distribution of the initial residual stress is measured when the crack is growing from the compressive residual stress field. Also, the tensile residual stress field. Also, the influence of the variation of residual stress distribution on fatigue crack growth behavior at the crack tip is studied when the initial crack occurs on weld metal, bead interface and HAZ (Heat Affected Zone), respectively. For this purpose, CT-type specimen that crack parallel to the welding bead were manufactured by butt welding on the Al. Alloy 1100-O plate.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2005년도 추계학술발표대회 개요집
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• pp.189-191
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• 2005

Dissimilar joining of AI 6013-T4 alloys and austenite stainless steel was carried out using friction stir welding technique. Microstructures near the weld zone and mechanical properties of the joint have been investigated. Microstructures in the stainless steel side and AI alloy were depended on the thermo-mechanical condition which they received. TEM micrographs revealed that the interface region was composed of the mixed layers of elongated stainless steel and ultra-fine grained AI alloy and intermetallic compound layer which was identified as the $Al_{4}Fe$ with hexagonal close packed structure. Mechanical properties were lower than those of 6013 AI alloy base metal, because tool inserting location was deviated to AI alloy from the butt line, which resulted in the lack of the stirring.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2005년도 춘계학술발표대회 개요집
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• pp.223-225
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• 2005

In order to demonstrate the friction stir weldability of the Al 6061 T-6 unequal thickness joint and determine optimum welding parameters, the relations between welding parameters and properties of the joints have been studied in this paper. The experimental results showed that the tensile properties of the joints are affected by the welding heat inputs and tool shape. In this study, the maximum ultimate strength of the as-welded joint is equivalent to 78% and 18hour aged joint is equivalent to 93% that of the base metal. Though the voids-free joints are fractured at the thermally affected zone on the advancing side, the fracture occurs at the weld center when the void defects exist in the joints.

• 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.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.331-336
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• 2004

Dissimilar friction welding were produced using 10mm and 11mm diameter solid bar in Inconel ally(IN X-750) to Stainless steel(STS316L) to investigate their mechanical properties. The main friction welding parameters were selected to endure good quality welds on the basis of visual examination, tensile tests, Virkers hardness surveys of the bond of area and HAZ and macro-structure investigations. The specimens were tested as welded, not heat-treated. The tensile strength of the friction welded steel bars was increased up to $95\%$ of the STS316L base metal under the condition of all heating time. Optimal welding conditions were n=2,000(rpm), $P_1=220(MPa),\;P_2=260(MPa),\;t_1=4(s),\;t_2=4(s)$ when the total upset length is 7(mm).