• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.7 s.178
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• pp.1763-1770
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• 2000

A finite element interface system for the design of optimal spot welding locations has been developed. In order to find out the optimal locations of spot welding points, iterative finite element an alyses are necessary, and thus automatic generation of finite element model for the structures with spot welded pointsis required. In this interface system, quadrilateral shell elements are automatically generated for finite element analysis of spot welded structured, which employs a domain decomposition methodand adaptive mesh(h-method).

• Journal of Welding and Joining
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• v.16 no.5
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• pp.76-85
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• 1998

The resistance spot welding process has been used for joining the sheet metal in automotive engineering. In the resistance spot welding, the weld quality is very important, because the quality of weld is one of the most important factors to the automobile quality. The size of he molten nugget has been utilized to estimate the weld quality. However, it is not easy to find the weld defects. For weldability estimation, we have to use the nondestructive method such as X-ray or ultrasonic inspection. But these kinds of approaches are not suitable for detecting the defects in real time. The purpose of this study is to develop the real time monitoring of the weld quality in the resistance spot welding. Obtained data were used to estimate weldability using fuzzy algorithm. It is sound that this monitoring and estimation system can be useful to improve the weld quality in the resistance spot welding process and it is possible to estimate the weldability in real time.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.10
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• pp.141-151
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• 1999

The resistance Spot Welding is widely used in the field of assembling the plates. However we don't still have any satisfactory solution, which is non-destructive quality evaluation in real-time or on-line, against it. Moreover, even though the rate of welding under the condition of expulsion has been high until now, quality control of welding against expulsion hasn't still been established. In this paper, it was proposed on the quality assurance technique of resistance spot welding pieces using Neuro-Fuzzy algorithm. Four parameters from electrode separation signal in the case of non-expulsion, and dynamic resistance patterns in the case of expulsion are selected as fuzzy input parameters. The parameters consist of Fuzzy Inference System are determined through Neuro-Learning algorithm. And then, fuzzy Inference System is constructed. It was confirmed that the fuzzy inference values of strength have within ${\pm}$4% error specimen in comparison with real strength for the total strength range, and the specimen percent having within ${\pm}$1% error was 88.8%. According to KS(Korean Industrial Standard), tensile-shear strength limit for electric coated of zinc is 400kgf/mm2. Judging to the quality of welding is good or bad, according to this criterion and the results of inference, the probability of misjudgement that good quality is valuated into poor one was 0.43%, on contrary it was 2.59%. Finally, the proposed Neuro-Fuzzy Inference System can infer the tensile-shear strength of resistance spot welding pieces with high performance for all cases-non-expulsion and expulsion. And On-Line Welding Quality Inspection System will be realized sooner or later.

• Journal of Welding and Joining
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• v.24 no.1
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• pp.71-76
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• 2006

In this study, the microstructure and mechanical properties of spot friction stir welded A 5052 alloy were investigated. Especially, the effect of insertion depth of welding tool on microstructural changes and mechanical properties was investigated in order to obtain the optimum spot friction stir welding condition. The lap shear load of spot friction stir welded A 5052 alloy plates showed lower value at the shallowest insertion depth and increased with tool insertion depth. At 1.6mm, the maximum value of 3.35 kN was obtained, and then dropped to lower load when the insertion depth was deeper. Spot friction stir welded joints showed shear fracture mode at shallower insertion depths and fracture mode changed to plug fracture mode as the insertion depth was deeper.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.10a
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• pp.582-587
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• 1993

A robot application system is developed for dual purpose of stud welding and are welding to weld plates in the manufacturing of elevator cabin. The production quantity is not so big to accommodate separate stations for stud welding and are welding respectively while the need for randomization of the processes is urgent. A robot with specification for spot welding is chosen, which is appropriate for stud welding. Some implementations are made so that the robot may also be shared for are welding process. Common jig and fixture is designed for the dual purpose. Important aspects in the procedure of system design, installation, and commissioning are stated, and signal set-ups and logic diagrams are illustrated.

• 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.

• Proceedings of the KWS Conference
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• 2008.05a
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• pp.24-24
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• 2008

• Journal of Welding and Joining
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• v.28 no.6
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• pp.76-83
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• 2010

The purpose of this study is to propose a method to decide near-optimal settings of the constant current fuzzy control parameters using a controlled random search. This method tries to find the near-optimal settings of the constant current fuzzy control parameters through experiments. It has an advantage of being able to carry out searches in the search domain which includes some irregular points. The method suggested in this study was used to determine the fuzzy control parameters by which the desired welding current were formed during inverter DC resistance spot welding. The output variable was the ITAE (integral of time multiplied by the absolute error). This output variable was determined according to the input variables, which are the GE, GDE, and GDU. This study described how to obtained near-optimal welding current condition over a wide search space conducting a relatively small number of experiments.

• Journal of Welding and Joining
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• v.21 no.4
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• pp.80-86
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• 2003

Arc-spot welding is generally used in joining of precise parts such as case and core in electric compressor. It is important to control joining deformation in electric compressor because clearance control of micrometer order is needed for excellent airtightness and anti-nose. The countermeasures for this deformation in field have mainly been dependent on rule of try and error by operator's experience because of productivities. For control this deformation problem without influence on productivities, development of exact simulation model should be needed. In this study, on the basis of previous study, the analysis model io predict deformation of precise order in arc-spot welded structure with non-uniform stiffness is brought up through feedback and tuning between monitoring data and analysis results. For this, deformation monitoring system was built and boundary condition considering mechanical melting temperature was applied.

• Proceedings of the KWS Conference
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• 2006.10a
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• pp.77-79
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• 2006

While RSW(Resistance Spot Welding) have been the most successful sheet metal joining process in automotive industry, there are certain qualify issues due to the control system and its application process. Recent materials and coatings make the process more complicated resulting in new challenges for quality welds. In this research, an intelligent RSW system with adaptive control algorithm is introduced to overcome typical RSW issues and its applications to automotive body assembly are presented.