Application of Weld Distortion Analysis Based on Thermal Shrinkage Technique to Buttering Welding of Cylindrical Structure

The purpose of this research is to establish a technique to predict weld distortion of large welded structures with practical accuracy and calculation time. The issue of the manufacturing process of large welded structures is improvement of productivity because it takes a lot of time to correct the weld distortion generated in the structure. Thermal elastic-plastic analysis has been applied as a tool to predict weld distortion, but calculation load is high and calculation time is extremely long. Thermal shrinkage technique is expected as a promising technology that can achieve both high accuracy and high-speed calculation. In this technique, shrinkage strain generated during the cooling process in the welding is applied to a specific region which is called shrinkage area, and then elastic-plastic analysis is performed. In this study, a parameter study was performed for the bead-on-plate welding in order to establish the setting method of shrinkage area, which is input data of thermal shrinkage technique. To evaluate effectiveness of thermal shrinkage technique, this technique was applied to inner surface buttering welding of cylindrical structure. The result of the thermal shrinkage technique was compared with the experimental result. In the bead-on-plate welding, the result of thermal shrinkage technique with rectangular shrinkage area consisting of width w and length (h +2dh) was in good agreement with the experimental result (w: bead width, h: bead height, dh: depth of heat affected zone). The thermal shrinkage technique with the established setting method was performed to the inner surface buttering welding of the cylindrical structure. The result of the thermal shrinkage technique was in good agreement with that of the experiment, suggesting that the thermal shrinkage technique had practical accuracy. The calculation time of the thermal shrinkage technique was 1⁄389 for bead-on-plate welding compared with thermal elastic-plastic analysis, which clarified that calculation time could be drastically shortened. In addition, the calculation time of the thermal shrinkage technique for cylindrical structure was about 30 minutes under given computing environment, which showed that the prediction of weld distortion for large structure could be performed with practical calculation time. It was concluded that the thermal shrinkage technique is effective to predict weld distortion of large welded structures with practical prediction accuracy and calculation time.