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김세현(Sehyeon Kim),황인성(Insung Hwang),강문진(Munjin Kang),박지용(Jiyong Park),유지영(Jiyoung Yu) 대한용접·접합학회 2021 대한용접·접합학회지 Vol.39 No.3
Resistance spot welding is a crucial assembly process for vehicle body manufacturing. The quality of the weld joint significantly influences the rigidity and durability of the vehicle; therefore, it is necessary to inspect the weld quality. The indentation depth of the resistance spot welding joint is widely used as an indicator to evaluate the quality of welds. However, because indentation tests on resistance spot welds are typically performed by field workers, additional time and process are required for the tests. Moreover, several attempts to apply automatic methods have shown limitations in high efficiency and prediction accuracy. To address this problem, we measured electrode displacement using a linear variable differential transformer during resistance spot welding in this study. In addition, we established an estimated regression model using the measured electrode displacement data to predict the indentation depth. Multiple regression models were estimated through stepwise regression analysis, and the significance of the model was analyzed through analysis of variance and residual analysis. Indentation depth prediction was performed after the resistance spot welding process using the proposed regression model, and prediction accuracy higher than 93% was achieved. The coefficient of determination obtained for this model was 94.72%.
Predicting Failure Modes of Resistance Spot Welds from the Chemical Composition of Materials
Heewon Cho(조희원),Sangwoo Nam(남상우),Minjung Kang(강민정),Munjin Kang(강문진),Young-Min Kim(김영민) 대한용접·접합학회 2020 대한용접·접합학회지 Vol.38 No.5
The failure mode of resistance spot welds on steel sheets was predicted according to the chemical composition of the materials. Resistance spot welding was performed on various steels sheets ranging from 440 to 1180 MPa grade steel. Tensile strength tests were performed, and the size and hardness of the nuggets were measured to analyze the mechanical properties of the welds. The hardness values of the fusion zone and heat affected zone were determined on the basis of the chemical composition of the materials. The interfacial and pull-out-failure-generated loads were calculated and compared to predict the failure mode of the welds. The failure mode prediction results demonstrated a trend analogous to the experimental results.
Al 5083 합금 용접부의 기계적 물성에 미치는 Mg의 영향
김동윤 ( Dongyoon Kim ),김동철 ( Dongcheol Kim ),강문진 ( Munjin Kang ),김영민 ( Young-min Kim ) 대한금속ㆍ재료학회 2017 대한금속·재료학회지 Vol.55 No.10
A new aluminum welding wire with 0.8 wt% higher in Mg content was developed and compared with commercial welding wire of the 5000 series. The weldability of the Al5083 base material was evaluated using high current metal inert gas (MIG) welding, using the developed Al5183 and commercial Al5183 welding wire. For the wire with 5.1 wt% Mg content, the hardness of the weld metal decreased with increasing heat input to the center of the weld under low and high heat input conditions. For the wire with 5.9 wt% Mg content, the hardness of the weld metal did not decrease under low and high heat input conditions. The wire with 5.1 wt% Mg content exhibited a tensile strength of about 300 MPa under the low/medium heat input conditions. The tensile strength decreased to 284 MPa under high heat input conditions. However, the welding wire with 5.9 wt% Mg content exhibited a tensile strength of 300 MPa regardless of the heat input condition. Dendritic microstructures were observed in the center of the welds in both wires, with Mg contents of 5.1 wt% and 5.9 wt%, and the second dendrite arm spacing (SDAS) increased with increasing heat input. (Received May 8, 2017; Accepted July 10, 2017)
Effect of Welding Time on Resistance Spot Weldability of Aluminum 5052 Alloy
Gu‑Cheol Kim,Insung Hwang,Munjin Kang,Dongcheol Kim,Hyunsung Park,김영민 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.1
In the study, the effect of welding time on resistance spot weldability of aluminum 5052-H32 alloy was analyzed throughsimulation and experiments. The resistance spot weldability was evaluated by measuring the tensile shear strength, nuggetsize, and hardness of welds with variations in the welding time. The simulated results of parameters such as tensile shearstrength and nugget size obtained using the SORPAS program were compared with the experimental results. Furthermore,a simulation was performed to calculate the temperature inside the weld nugget based on the distance from the center of thenugget. Hence, an optimum welding time to retain the required weld strength of the aluminum 5052-H32 alloy was obtained.