Abstract: The localized plastic buckling occurred in the transition region in the torispherical end closure of a pressure vessel is analyzed by FEM. By introducing the initial geometrical imperfection, which is determined from the elasto-static displacements, into the zone where it is circumferentially compressed, the arc-length method RIKS procedure is employed to simulate the deformation process during loading. The buckling point is captured from the load-deflection curve of a typical point within the buckled zone, and the corresponding buckling load is calculated. The results show that the buckling load is quite sensitive to the artificial geometrical imperfections. Fur-thermore, after the first buckling initiated, the succeeding load-ing will lead to more wrinkles within the compressive transition region. Additionally, the case that with four distributed imper-fections is also analyzed. It can be seen that the interaction be-tween the imperfections is very weak before or even after the first buckling occurred, which means the buckling is fairly lo-calized.

Key words: Elasto-plastic buckling, Finite element method, Internal pressure, Pressure vessel