• Journal of Advanced Marine Engineering and Technology
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• v.29 no.8
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• pp.891-898
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• 2005

Inertia welding is a solid-state welding process in which butt welds in materials are made in bar and in ring form at the joint race, and energy required lot welding is obtained from a rotating flywheel. The stored energy is converted to frictional heat at the interface under axial load. The quality of the welded joint depends on many parameters, including axial force, initial revolution speed and energy amount of upset. working time, and residual stresses in the joint. Inertia welding was conducted to make the large exhaust valve spindle for low speed marine diesel engine. superalloy Nimonic 80A for valve head of 540mm and high alloy SNCrW for valve stem of 115mm. Due to different material characteristics such as, thermal conductivity and flow stress. on the two sides of the weld interface, modeling is crucial in determining the optimal weld geometry and Parameters. FE simulation was performed by the commercial code DEFORM-2D. A good agreement between the Predicted and actual welded shape is observed. It is expected that modeling will significantly reduce the number of experimental trials needed to determine the weld parameters. especially for welds for which are very expensive materials or large shaft. Many kinds of tests, including macro and microstructure observation, chemical composition tensile , hardness and fatigue test , are conducted to evaluate the qualify of welded joints. Based on the results of the tests it can be concluded that the inertia welding joints of the superalloy exhaust valve spindle are better properties than the material specification of SNCrW.

• Journal of the Korean Society of Safety
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• v.34 no.6
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• pp.7-12
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• 2019

Flux Cored Arc Welding (FCAW), which has been widely used in many industries, was developed in the 1950s to supplement shortcomings of the Shielded Metal Arc Welding (SMAW). FCAW has an advantage in that it can weld regardless of postures and give good quality results in the filed with many different working conditions. In this study, SM490A (rolled steel for welding structural purpose) with different thicknesses (L:25T+R:30T) were welded using FCAW. Then the mechanical properties (tension test, bending test, hardness test, impact test and macro test) were analyzed and the following conclusions were drawn. In the tensile test, it exceeds the KS standard tensile strength range (400~510) in all welding positions, which means there is a problem in the tensile force transmission performance. In the bending test, it was found that most of the specimens did not exhibit surface rupture or other defects during bending test and they exhibit sufficient toughness even after plastic deformation. In the hardness test, all the results were lower than the standard value of 350 Hv of KS B 0893, which means they have good hardness. In the impact test, all results were larger than the KS reference value of 27J. In the macro test, they showed uniform structure state by the shape of the weld, and there was risk of lamination because no internal defects, bubbles, or impurities were found on the surface of the weld.

• Journal of Korean Society of Steel Construction
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• v.23 no.4
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• pp.483-491
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• 2011

The fabrication of steel structural members always involves welding process such as flux cored arc welding. Therefore, for the application of structural steels to cold regions, it is a prerequisite to clarify the service temperature of the welded joints in order to ensure the structural integrity of the welded parts. In this study, the Charpy impact test was conducted to evaluate the service temperature of structural steel weld. The Charpy impact test is a commercial quality control test for steels and other alloys used in the construction of metallic structures. The test allows the material properties for service conditions to be determined experimentally in a simple manner with a very low cost. Standard V-notch Charpy specimens were prepared and tested under dynamic loading condition. The service temperatures of the weld metal, HAZ (heat affected zone) and base metal were derived by the absorbed energy and the impact test requirements; thus the applicability of the structural steels to cold regions was discussed in detail.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.11
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• pp.1007-1013
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• 2014

In this study to improve the productivity, advantage Tandem circumferential weld process of seam tracking system was applied for the laser vision sensor. Weld geometry scanning laser vision sensor and PLC control unit are used to scan correct positioning of welding torch when the program is implemented so that it can correctly track the welding line. The welding experiment was conducted to evaluate the performance of laser vision seam tracking sensor in tandem welding process. The seam tracking several experiments was to determine the reliability of the system, welding experiments relatively good quality welding bead was confirmed. Furthermore, the PLC program for seam tracking was used to confirm the validity of the application of tandem welding process according to the benefits of increased productivity, which is expected to contribute to national competitiveness.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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• pp.306-316
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• 2002

This paper summarizes the results of full-scale cyclic seismic testing on four RBS (reduced beam section) steel moment connections. Key test variables were web bolting vs. welding and strong vs. medium PZ (panel zone) strength. The specimen with medium PZ strength was specially designed to mobilize energy dissipation from both the PZ and RBS region in a balanced way; the aim was to reduce the requirement of expensive doubler plates. Both strong and medium PZ specimens with web-welding were able to provide sufficient connection rotation capacity required of special moment frames, whereas specimens with web-bolting showed inferior performance due to the premature brittle fracture of the beam flange across the weld access hole. In contrast to the case of web-welded specimens, the web-bolted specimens could not transfer the actual plastic moment of the original (or unreduced) beam section to the column. If a quality welding for the beam-to-column joint is made as in this study, the fracture-prone area tends to move into the beam flange base metal within the weld access hole. Analytical study was also conducted to understand the observed base metal fracture from the engineering mechanics point of view.

• Journal of Welding and Joining
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• v.24 no.6
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• pp.13-20
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• 2006

Resistance spot welding is widely used for joining sheet metals in the automotive manufacturing process. Recently, servo-gun is used to increase the productivity and precise control the acting force. However, force control mechanisms have not been investigated with servo-guns until now. In this paper, it is proved that servo-motor current is proportional to torque and by experiment, experimental equation between servo-motor current and electrode force was derived. Algorithm for feedback control of electrode force was suggested using current measurement. In addition, applying soft touch method to this system the impact between electrode and specimen, which is the problem of air gun, could be reduced. Indentation made the force decrease in holding time of resistance spot welding. In order to overcome this problem, force compensation using the servo gun was used and it improved weld strength in good welding current range.

• Journal of the Society of Naval Architects of Korea
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• v.37 no.2
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• pp.127-136
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• 2000

Welding deformations reduce the accuracy of ship hull blocks and decrease the productivity due to correction work. Preparing an error-minimizing guide at the design stage will lead to a high quality as well as high productivity. And a precise method to predict the weld deformation is an essential part of it. This paper proposes an efficient method to predict complicated weld deformations based on the inherent strain theory combined with the finite element method. The inherent strain is determined by the highest temperature and the degree of restraint. In order to calculate the inherent strain exactly, it is considered that the degree of restraint becomes different according to the fabrication stages in real structures. A simulation of a stiffened plate shows the applicability of this method to simple ship hull blocks.

• Laser Solutions
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• v.16 no.1
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• pp.10-14
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• 2013

Remote laser beam welding (RLW) has the benefits of high speed and high quality welding, especially as applied to automotive industry. RLW is designed in a way that end effecter and head of scanner move simultaneously, and require the compensation for the motion of end effecter in order to weld proper position. In this paper, we show the algorithms of RLW that enable the end effecter to synchronize with scanner based on time. The proposed method consists of two algorithms. These algorithms make it possible for the moving end effecter to weld on desired place. The effectiveness of the algorithms is shown by experiments.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.2
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• pp.300-307
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• 2002

Partial penetration welding joint is defined as groove welds welded from one side, without steel backing or groove welds welded from both sides but without back gouging. So it has an unwelded portion at the root of the weld. Study of partial penetration weldment fracture behavior includes residual stress analysis and fracture analysis. The J-integral loses its path independency in residual stress field. Therefore, it is necessary to introduce a new J-integral, J, which is defined including the effect of plastic deformation and thermal strain. In this study, theoretical formulation and program were developed for the evaluation of J-integral for the crack tip located in the weldment. Evaluations of fracture behavior were performed for partial penetration multi-pass weldment of 25.4mm thick plate by J-integral. From a point of fracture in partial penetration multi-pass welding, it seemed to be better to control root face smaller than 6.35mm.

• Journal of Welding and Joining
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• v.14 no.1
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• pp.99-106
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• 1996

Development of an automatic TIG welding system incorporating a vision sensor and torch control mechanism leads to an improved welding quality and greater production efficiency. The automatic welding system should be greatly restricted in its size and weight for the LNG(Liquefied Natural Gas) storage tank and also provide a unique torch rotating mechanism which keeps the torch tip in the constant position while the angle is changed continuously to maintain the welding torch substantially perpendicular to the weld line. The developed system is driven by two translation axes X, Z and one rotational axis. A moving line window method is adopted to the image recognition of the corrugated membranes with specular reflection. This method decides original laser stripe patterns in image which is affected by multi-reflection. A self-teaching algorithm, which guides the automatic welding machine with the information provided by the CCD camera without any previous learning of a reference trajectory, was developed for tracking the corrugated membrane of the LNG tank along the weld line.