薄肉補強リング付きベローズの内圧座屈評価手法

抄録

This paper describes evaluation methods of in-plane squirm buckling strength of bellows with thin wall reinforcing rings. Many bellows with thin wall reinforcing rings are used in the facilities of nuclear power plants. Bellows used in a vent pipe of the Mark-I type pressure containment vessel (PCV) is one of the examples. Bellows with solid reinforcing rings are not buckled due to internal pressure because deformation of bellows is restricted by the reinforcing rings. However, bellows with thin wall reinforcing rings might be buckled when it is subjected to high pressure exceeding design conditions. Buckling strength of the in-plane squirm mode is dominated by plastic collapse strength of convolutions, but buckling strength evaluation methods for bellows with thin wall reinforcing rings have not been proposed. Authors carried out parametric plastic collapse analyses for bellows with thin wall reinforcing rings, and examined simplified evaluation methods. Proposed evaluation methods were developed based on the formulae defined in Standards of the Expansion Joint Manufacturers Association (EJMA). Buckling strength of bellows with thin wall reinforcing rings can be evaluated using the effective thickness which is the same bending stiffness with the added thickness of bellows and reinforcing rings.