Weld distortion prediction of the CFETR vacuum vessel by inherent strain theory

The CFETR (China Fusion Engineering Test Reactor) vacuum vessel sectors have high density welded joint, and as-welded size of the vacuum vessel is within a very tight tolerance, prediction of weld distortion is critical to allow the final assembly with the other components. Based on inherent strain theory, the weld distortion of the vacuum vessel can be predicted using the computer package ABAQUS. In this paper, calculation and application method of inherent strain on various welded joints is proposed. Six possible welding sequence schemes of the PS3 segment are provided within the actual processing condition, weld distortion of vacuum vessel on six welding sequence schemes is studied without external constraints condition, then according to the distortion value and distortion tendency without external constraints condition, the external constraints condition are provided. The optimal welding sequence can be obtained by the simulation result with external constraints condition, which can provide data support and theoretical guidance for the actual processing of the CFETR vacuum vessel.