Testing program for Burning Plasma Experiment vacuum vessel bolted joint

As presently designed, the Burning Plasma Experiment vacuum vessel will be segmentally fabricated and assembled by bolted joints in the field. Due to geometry constraints, most of the bolted joints have significant eccentricity, which causes the joint behavior to be sensitive to joint clamping forces. Experience indicates that, as a result of this eccentricity, the joint will tend to open at the side closest to the applied load, with the extent of the opening depending on the initial preload. Analytical models and a testing program were developed to investigate and predict the nonlinear behavior of the vacuum vessel bolted joint. The test results are comparable with the analytical solutions in general, showing about 15% less load capacity than the finite element analysis predicted because the test specimens contained certain manufacturing and fabrication tolerances. The bolted joint capacity can be predicted by the finite element analysis, provided that an appropriate factor of safety be applied to cover these tolerances. The imperfections of the flanges and spacer surfaces are sensitive to the bolted joint characteristics. The design tolerances for the surfaces should be carefully specified. >