Contour precision controlling of welding distortion in fabrication for stainless steel hyperbolic shells adopting mechanical constraints

Double-layer shell structures are widely used in the carapaces of vacuum vessels, cyclotrons, submarines and ships. The design of this double-layer structure considers the structural strength, sealing and special conditions. In the shell processing, the crisscross ribs are welded with the inner and outer shells to become parts. The welding deformation caused by multiple joints exceeds the tolerance, and external constraints are needed to ensure the forming accuracy of the contour. In this paper, the suppression effect of fixture and rigid constraint method on welding deformation of butt joint and T-joint was analyzed. The welding specimen of the double-layer shell structure was carried out, and the influence of different welding sequences on the final welding deformation was analyzed. Through external mechanical constraints, the deformation is reduced from 7.27 mm to 2.89 mm, which meets the tolerance requirements. The measured deformation is compared with the simulation results based on the inherent strain theory, which verifies the reliability of the numerical model and provides technical guidance for engineering manufacturing.