Measurement and Numerical Analysis of Welding Residual Stress in Box Structure Employed for Breeder Blanket System of Iter

Abstract

In order to evaluate the ability to construct a box structure employed for the breeder blanket system of ITER, a real-scale structure of the current Japanese ITER test blanket module was fabricated by electron beam (EB) welding between the first and side walls according to the manufacturing plan, and the residual stresses were measured using X-ray. Also, to examine the reliability of experimental results, thermal elastic-plastic finite element analysis was conducted. At the corner of the box and weld end point, the relatively higher tensile stresses perpendicular to the weld direction were measured. The measured residual stress parallel to the weld line at the mid-point of the weld line had a fair agreement with the computed result. On the other hand, the experimental value perpendicular to the weld line was different from the numerical result, since the residual stress might be released excessively by the grinding of the wide area. Moreover, from the analyses of bead on EB welding for various thickness plates, it was found that the larger compressive stress perpendicular to the weld line would be produced at the surface of thicker plates due to the larger internal mechanical restraint.