Calculation of some parameters of polyhedron bulging process

Single‐curvature polyhedron bulging technology for manufacturing spherical vessels is to build spherical vessels by assembling and welding sheet blanks of zero‐curvature and single‐curvature into a polyhedron, then gradually bulging the polyhedron into a spherical vessel. With the technology, heavy presses and large dies are not needed, so spherical vessels can be built at low cost. In order to make a polyhedron after being bulged satisfy given dimension requirements of the spherical vessel, it is necessary to calculate wall thickness and diameter of the polyhedron under bulging pressure.In this paper, wall thickness decrement and deflection of a point on a single‐curvature polyhedron during bulging are measured, it proves that the wall thickness decrement is much smaller than the deflection. Under the assumption that wall thickness of a polyhedron keeps constant during bulging, the constant‐area spheritaxis principle is put forward. With this principle, methods of calculating diameter, wall thickness of a polyhedron and pressure under which the polyhedron becomes a spherical vessel are got. Besides, other applications of the principle are also given.