Arc welding is usually used for bonding structural members and machine parts. When some defects or cracks are detected, however, it sometimes provides practical and effective means for compensating the strength of welded joint as a so-called repair welding. In normal practice, the regions containing defects are removed as a circular hole whose diameter is larger than 8cm. A circular plate with the same diameter is placed to plug the hole; then the repair welding with curved beads is conducted to bring the structure into the original shape. In this paper, a numerical approach using three-dimensional Finite Difference Method (FDM) in the transient temperature field is presented for evaluating the fundamental characteristics of cooling process of patch welding with curved beads. Arc welding is performed to verify the validity of the proposed numerical method by measuring the cooling process at the welding junction. In addition, the numerical results of temperature distributions on plate surface are also compared with those obtained by infrared thermography.
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