Distortion-free Welding of Thin-walled Elements Based on Thermal Tensioning Effects

Buckling distortions are more marked than other forms of welding distortions in manufacturing thin-walled structural elements. They are the main troublesome problems in sheet metal fabrication where fusion welding is applied especially for aerospace structures such as sheet metal formed airframe panels, fuel tanks, shells of jet engine cases etc. with material thickness less than 4 mm. Extensive research and development studies to explore distortion-free welding techniques were carried out at Beijing Aeronautical Manufacturing Technology Research Institute (BAMTRI). To prevent buckling, Low Stress No Distortion (LSND) welding techniques were pioneered at BAMTRI and implemented successfully for product engineering and component manufacturing. Two innovative methods of LSND welding techniques have been developed for industrial application: one is based on the whole cross-section thermal tensioning effect, the other is based on the localized thermal tensioning effect. The nature of LSND welding techniques is to create active in-process control of incompatible (inherent) plastic strains and stresses formation during welding to achieve distortion-free results implying that no post weld costly reworking operations for distortion correction is required. In this paper, the mechanisms of LSND welding techniques either using whole cross-section thermal tensioning effect or using localized thermal tensioning effect are described and analyzed in details.