• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.4
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• pp.98-104
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• 2006

In this paper, for the purpose of investigation the acoustic emission(AE) behaviors during resistance spot welding process and tension test of spec steels. As the results present the resistance spot welding method that can get suitable welding qualities or structural integrity estimating method. The resistance spot welding process consists of several stages: set-down of the electrodes; squeeze; current flow; forging; hold time; and lift-off. Various types of AE signals are produced during each of these stages. For tensile-shear test and cross tensile test in resistance spot welded specimens, fracture pa 야 ems are produced: tear fracture; shear fracture; and plug fracture. Tensile-shear specimens strength appeared higher than cross tensile specimens one. In case of tensile-shear specimen happened tear fracture that crack happens in most lower plate. Also, in case of cross tensile specimens, upper plate and lower plate are detached perfect fracture was exposed increases a little as acting force is lower than ordinary welding condition. Therefore, the structure which is combined by resistance spot welding confirmed that welding design must attain so that shear stress may can interact mainly.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.10a
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• pp.49-53
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• 2004

Thin spot welding is frequently used for industrial purpose, such as automobile and aerospace industries and household appliances due to its high performance. In these days, the systemization of welding process made it possible to produce more precise or smaller electric parts. And when it comes to welding of steel sheets, the size of nugget must be getting smaller. Therefore, welding conditions are limited to avoid defects, such as deformation, damage and weakening of joining area. In this research, thin spot welding establishes the welding conditions, and then the measurement of the nugget size by the nondestructive inspection has been conducted. As a result, the right estimation of the nugget size, the detection of corona bond near joining area, the selection of the optimum ultrasonic mode, and setup for ultrasonic inspection are studied. From the trustworthy solutions of the nugget size estimated by results of measurement, the optimum inspection conditions depending upon the width of welding parts are determined as well.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.1
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• pp.148-159
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• 1998

Spot welding palys a key role in increasing productivity and weight reduction of the final products. This paper proposes a systematic approach on the design of spot weld configuration, dealing with the requried number and location of spot weld joints under the given design parameters, such as the applied loads, lap area, and individual spot weld strength. The optimal design of a spot-welded joint is postulated as a state when the safety factors of all spot weld points (i) are evenly distributed and (ii) reach maximum value. A CAD program is developed to arrange the optimal location of each spot weld based on the derived objective function and constraints. The CAD tool integrates the optimization procedure with Finite Element Analysis (FEA) code through an interface. The interface automatically provides geometrical data and mesh configuration for different spot weld locations to FEA model. It also extracts the transmitted load of each spot weld from the FEA code, and allows the optimization code predict an improved arrangement of spot weld locations. The feasibility of the developed approach is demonstrated by the selected examples.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.14 no.5
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• pp.74-79
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• 2005

Spot welding widely used in automotive and aerospace industries has made it possible to produce more precise and smaller electric part by robotization and systemization of welding process. The quality of welding depends upon the size of nugget between the overlapped steel plates. Recently, the thickness of the steel plates becomes much thinner and hence, it introduces the smaller size of nugget. Therefore, it is necessary to develop the criterion to evaluate the quality of weld in order to obtain the optimal welding conditions for the better performance. In this paper, a thin steel plates, 0.1mm through 0.3mm thickness, have been spot-welded at different welding conditions and the nugget sizes are examined by defocused scanning microscopy. The relationships between nugget sizes and weldability have been investigated experimentally. The result of ultrasonic technique shows the good agreement with that of the tensile test.

• Journal of Welding and Joining
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• v.24 no.1
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• pp.50-55
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• 2006

In an attempt to optimize friction spot joining process of Al alloys for automobiles, effects of joining parameters such as tool rotating speed, plunging depth, and joining time on the joints properties were investigated. A wide range of joining conditions could be applied to join Al alloys for automobile without defects in the weld zone except for certain welding conditions with a lower heat input. For sound joints without defects, tensile shear strength of joints was higher than acceptable criteria of tensile shear strength of resistance spot welded joints for aluminum.

• Journal of Welding and Joining
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• v.9 no.3
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• pp.41-51
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• 1991

The thermomechanical coupling phenomena in the resistance welding process is complicated due to interactions of mechanical, thermal and electrical factors. Although experimental investigations of resistance spot welding have been carried out, but there are a few by computer simulation. so the purpose of this research is to decrease the time and cost much required in experimental investigation by carrying out the analysis of the resistance spot welding process through computer simulation based on the finite element method. The tool used in the computer simulation is the commercial ANSYS program package. A two dimensional axisymetric model is used to simulate the resistance spot welding for two stainless steel sheets of equal thickness and parametric study is carried out for variable welding current, workpieces of unequal thickness and dissimilar materials. The results from the computer simulation are in good agreement with the experimental one. Through these results, such items as stress distribution, temperature profiles, thermal expansion and weld nugget formation are predicted. Reliability and applicability of finite element models have been demonstrated to simulate and to analyze the resistance spot welding process.

• Proceedings of the KWS Conference
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• 2003.11a
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• pp.147-149
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• 2003

Many factors, such as welding current, welding time, force, electrode shape, the output stability of a welding machine, are closely related with micro spot series welding. Of those factors, the output stability evaluation of the welding machine would be checked first. in this study, we applied 6$\sigma$ to evaluation for the output stability of the welding machine. We estimated output stability and control stability of the welding machine by using Cp(process capability), Ppk and 4-block diagram. Therefore the problem as solved in micro spot series welding process and the problem of output control in welding machine by 6$\sigma$ tool.

• Proceedings of the KSR Conference
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• 2009.05b
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• pp.559-564
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• 2009

Aluminum extrude is increasing to vehicle body manufacture of a recent railroad vehicle. Conventional welding of this aluminum extrude has been used MIG welding or resistance spot welding mainly. But the advanced manufactures like Japan's tried to apply the friction stir welding and friction spot joining at railroad vehicle body manufacture process. Therefore in this paper we tried to study to apply friction stir welding to AL 6005-T6 extrude which has been manufactured the railroad vehicle mainly. In this study we investigated first the mechanisms to affect the welding strength in friction stir welding. After we made the 3 tools of different shape, we observed how the welding strength changed while changing the welding time and the rotation speed, the plunging depth.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.239-242
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• 2009

Friction stir spot welding (FSSW), developed based on principle of friction stir welding, has been paid attention as a new solid-state spot welding process. Since FSSW can produce high-quality weld in Al alloys more easily than resistance spot welding, this process has been already used for construction of Al components in the automotive industries. Despite the large industrial interests in FSSW, fundamental knowledge on welding phenomena of this process has not been fully understood. In this study, FSSW phenomena, such as the consolidation mechanism, the microstructural evolution and the material flow, were examined in Al alloy 6061. This study clarified that the elliptical zone found in the vicinity of the pin hole on the cross section was characterized by the initially lapped surface of two sheets. Moreover, the following material flow was proposed; capture of the upper material with the threads on the pin surface, spiral flow along the tool rotation, and then release at the tip of the pin.

• Journal of Powder Materials
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• v.31 no.1
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• pp.37-42
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• 2024

Friction stir spot welding (FSSW) is a solid-state joining process and a rapidly growing dissimilar material welding technology for joining metallic alloys in the automotive industry. Welding tool shape and process conditions must be appropriately controlled to obtain high bonding characteristics. In this study, FSSW is performed on dissimilar materials AA5052-H32 aluminum alloy sheet and SPRC440 steel sheet, and the influence of the shape of joining tool and tool insertion depth during joining is investigated. A new intermetallic compound is produced at the aluminum and steel sheets joint. When the insertion depth of the tool is insufficient, the intermetallic compound between the two sheets did not form uniformly. As the insertion depth increased, the intermetallic compound layer become uniform and continuous. The joint specimen shows higher values of tensile shear load as the diameter and insertion depth of the tool increase. This shows that the uniform formation of the intermetallic compound strengthens the bonding force between the joining specimens and increases the tensile shear load.