DESIGN OF SHELL CONJUNCTION ZONES IN PRESSURE VESSELS

Abstract

Separation forces occur in shell junctions of fuel tanks due to the change in its geometry. To compensate the forces, thrust rings are placed in these zones. Moreover, there is a necessity to determine a form and dimensions of the trust ring cross section with consideration of the operation conditions. Welding is used to join trust rings with a shell in case of conventional manufacturing. Nowadays, additive manufacturing technology is constantly being developed. Additive method allows to create objects with various geometry, in a layer-by-layer way of addition of the material in accordance with a computer model. These new technological capabilities make the task of determining of the geometry of the fuel tank in the shell’s junctions zone actual. 
 The following work provides a consideration of two approaches to the determination of the conversion geometry of shells in-between area instead of trust ring. The first approach is based on determination of a median surface with the use of rational cubic splines and membrane theory of shells. The second approach is based on the use of topology optimization of the initial design. The choice of the first approach relates to the fact that standard energy functional like potential energy of uniform bent rod or uniform sheet can be described with cubic splines. In the following work the use of rational cubical splines for build-up a transitive area in a junction zone of the spherical-conical vessel is considered. Spline parameters are determined based on the condition of median surface propagation of the transitive zone in its probable location. Thickness of the shell in the transitive area was evaluated due to the membrane theory of shells with the use of Huber von Mises Hencky theory of failure. Obtained solutions are tested in numerical models of spherical-conical vessel. Comparison of two approaches is carried out and practical recommendations are given.