Influence of local rate of deformation during cold plate bending on properties of spherical tank segments.

Bending of the spherical tank segments is performed through several working ranges of the hydraulic press tool. In the process of bending the shell spherical segments in the tool, creeps may be formed at the plate edge if the plate width is not adjusted to the toll radius and dimensions. In order to obtain the required radius, the plate si calibrated to remove the formed creeps and readjust the segment angles, Examination results of these parts of segments reveal considerable change in tensile stress R(mv) yield stress R(e) perecentage of strain A(5), and toughness J compared to the places with no creeps. Therefore the right width of the plate in relation to dimensions of the tool must be chosen to prevent creeping at the plate edges during the process of the segment bending. Of greatest relevance is the magnitude of circular stress defined by the finite elementg method in the plasto/elastic area.