• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.1404-1407
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• 1996

A quality monitoring system in butt welding process is proposed to estimate weld pool sizes. The geometrical parameters of the weld pool such as the top bead width and the penetration depth plus half back width are utilized to prove the integrity of the weld quality. The monitoring variables used are the surface temperatures measured at three points on the top surface of the weldment. The temperature profile is assumed that it has a gaussian distribution in vertical direction of torch movement and verify this assumption through temperature analysis. A neural network estimator is designed to estimate weld pool size from temperature informations. The experimental results show that the proposed neural network estimator which used gaussian distribution as temperature information can estimate the weld pool sizes accurately than used three point temperatures as temperature information. Considering the change of gap size in butt welding, the experiment were performed on various gap size.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.211-216
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• 2003

Weld line in injection molded part is one of the defect in injection molding process. Weld line deteriorates not only appearance quality but mechanical property. In this study weld line strength has been examined according to the injection operational conditions, materials and mold designs. PC and PP were used, and four different specimens were used in this experiment. Weld line strength decreased as injection temperature increases for PC. It was more dependent on mold temperature than injection temperature for PP Among the four different specimens, uneven thickness specimen showed the highest weld line strength.

• Journal of Welding and Joining
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• v.32 no.1
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• pp.93-101
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• 2014

This study aims to investigate the effect of heat input of outside SAW weld on low temperature toughness($-20^{\circ}C$) of inside SAW weld for API 5L X70 with sour gas resistance. As increasing heat input of the outside weld, low temperature toughness of the inside weld was decreased. Especially, in spite of the same heat input, the value of low temperature toughness was fluctuated. On the basis of fracture and microstructure analysis, the low temperature toughness is correlated with the fracture area ratio of shear lips and four kinds of fracture sections. These sections were divided with size and shape of dimple correlated with grain boundary ferrite and cleavage correlated acicular and polygonal ferrite in grain. Therefore, it was seen that these sections were two of final solidification area in the inside weld and the outside weld, no reheated zone and reheated zone in the inside weld. In conclusion, it is thought that the difference of low temperature toughness at the same heat input is due to the fact that each of impact test specimens could have the different microstructure, even though the notch was machined under the error tolerance of 1mm. It is because the final solidification area of the inside weld is very narrow.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.181-186
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• 2001

JLF-1 steel (Fe-9Cr-2W-V-Ta), low activation ferritic steel, is one of the promising candidate materials fer fusion reactor applications. High temperature fatigue life and tensile strength of JLF-1 steel and its TIG welded joints were investigated at the room temperature and $400^{\circ}C$. The strength of base metal (JLF-1) is in between those of weld metal and the HAZ. When the test temperature was increased from room temperature to $400^{\circ}C$, both strength and ductility decreased for base metal, weld metal and the HAZ. The longitudinal specimens of base metal showed similar strength and ductility compared with those of the transverse specimens at room temperature and $400^{\circ}C$. Little anisotropy was observed in the JLF-1 steel base metal in terms of rolling direction. Fatigue limit of weld metal which was obtained from cross-weld specimen is 495MPa. Thus, the weld metal showed the higher fatigue limit than those of base metal at both room temperature and $400^{\circ}C$. Little anisotropy of fatigue properties was observed for JLF-1 base metal in terms of rolling direction. When the test temperature was increased from room temperature to $400^{\circ}C$, the fatigue limit of both base metal and weld metal decreased substantially.

• Design & Manufacturing
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• v.6 no.2
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• pp.1-5
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• 2012

Weld line in injection molded part is one of the defects in injection molding process. Weld line deteriorates not only appearance quality but mechanical property. In this study, ABS and PP were used as experimental materials. And weld line length, depth and strength have been examined according to the injection molding conditions. As the results of experimental studies, weld line length increased as flow rate increases for all materials. And the flow rate is most influenced to the creation of weld line length. Also weld line strength increased, as flow rate and melt temperature increase for all materials. The whole experiment results was similar to CAE analysis results.

• 한국금형공학회:학술대회논문집
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• 2008.06a
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• pp.115-119
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• 2008

Weld line in injection molded part is one of the defects in injection molding process. Weld line deteriorates not only appearance quality but mechanical property. In this study, ABS and PP were used as experimental materials. And weld line length, depth and strength have been examined according to the injection molding conditions. As the results of experimental studies, weld line length increased as flow rate increases for all materials. And the flow rate is most influenced to the creation of weld line length. Also weld line strength increased, as flow rate and melt temperature increase for all materials. The whole experiment results was similar to CAE analysis results.

• Journal of Welding and Joining
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• v.24 no.1
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• pp.64-70
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• 2006

570MPa grade weldable steels were gas metal arc welded with various heat inputs and interpass temperatures using flux cored wires. Effects of heat input and interpass temperature on the strength and impact toughness of weld metal were investigated in terms of microstructural change, recovery of alloying elements, and the amount of reheated weld metal. Increase of heat input and interpass temperature resulted in decrease of weld metal strength. This is because of the small amount of acicular ferrite, large columnar size and low recovery of alloying elements such as manganese and silicon. In addition to the microstructural change, weld metal toughness was also influenced by the deposition sequence. It increased with an increase of the amount of reheated weld metal.

• Journal of Ocean Engineering and Technology
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• v.29 no.6
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• pp.481-487
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• 2015

The effects of the heat input and preheat/interpass temperatures on the tensile strength and impact toughness of multipass welded weld metal were investigated and interpreted in terms of the recovery of the alloying elements and microstructure. Increases in both the heat input and preheat/interpass temperatures decreased the tensile strength of the weld metal. A lower recovery of alloying elements, especially Mn and Si, and smaller area fraction of acicular ferrite in the weld metal were observed in higher heat input welding, resulting in a lower tensile strength. In contrast, only a microstructure difference was observed at a higher preheat/interpass temperature. The impact toughness of the weld metal gradually increased with an increase in the heat input because of the lower tensile strength. However, it decreased again when the heat input was larger than 45 kJ/cm because of the much smaller area fraction of acicular ferrite. No effect of the preheat/interpass temperature on the impact toughness was observed. The formation of a weld metal heat-affect zone showed little effect on the impact toughness of the weld metal in this experiment.

• Journal of Welding and Joining
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• v.32 no.4
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• pp.1-9
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• 2014

A quantitative understanding on the effect of the welding conditions on weld joint dimensions and weld thermal cycle is difficult through experimental studies alone. The experimental realization of temperature distribution in the weld pool is proved to be extremely difficult due to the small size of welds, high peak temperature and steep temperature gradients in weld pool. This review deals with the heat transfer and fluid flow analysis to understand the parametric influence of a single wire submerged arc welding (SAW) and multi-wire SAW processes on the weld bead dimensions, temperature and fluid flow distribution in the weldment.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.98-103
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• 2008

This paper is to discuss distribution of welding residual stresses of a ferritic low alloy steel nozzle with dissimilar metal weld using Alloy 82/182. Two dimensional (2D) thermo-mechanical finite element analyses are carried out to simulate multi-pass welding process on the basis of the detailed and fabrication data. On performing the welding analysis generally, the characteristics on the heat input and heat transfer of weld are affected on the weld residual stress analyses. Thermal analyses in the welding heat cycle process is very important process in weld residual stress analyses. Therefore, heat is rapidly input to the weld pass material, using internal volumetric heat generation, at a rate which raises the peak weld metal temperature to $2200^{\circ}C$ and the base metal adjacent to the weld to about $1400^{\circ}C$. These are approximately the temperature that the weld metal and surrounding base materials reach during welding. Also, According to the various ways of appling the weld heat source, the predicted residual stress results are compared with measured axial, hoop and radial through-wall profiles in the heat affected zone of test component. Also, those results are compared with those of full 3-dimensional simulation.