ON THE MODELING OF PRESSURE VESSEL SHELL PORTION AFFECTING LOCAL DEFORMATION AT NOZZLES AND OTHER STRUCTURAL DISCONTINUITIES

摘要

In stress analyses of a nozzle in a cylindrical pressure vessel, or a nozzle subjected to asymmetric loading, it is a concern for a designer how to determine the boundary shell length in the three dimensional finite element model. It is well-known that the boundary shell requires more length than in case of axisymmetric analysis. This paper presents analytical studies of cylinders whose one ends are subjected to prescribed deformation. These boundary and load are intended as a simplified model of the boundary condition in such a structure.The effect of the prescribed deformation such as deformation at the other end and reaction forces at the loaded point were observed. The analyses were performed for the cases of various values of thickness and lengths. Different Young's modulus and Poisson's ratio and several mesh sizes were also studied. Among these parameters, it was shown that thickness affects the reaction deformation the most. According to the results, this paper proposes the appropriate length of the shell portion as 1.2R(R/t)~(1/2) for free edge boundary condition.