ABOUT THE DESIGN OF SPHERO-CONICAL VESSEL CONSIDERING THE LIMITATIONS OF ADDITIVE TECHNOLOGIES

Abstract

Pressure vessels are widely used in in aerospace industry. It is due to recent emergence of new technological possibilities of additive manufacturing that made it possible to createmore advanced aircraft units with meeting the conditions of strength and minimum weight.

In this paper, the features of design of a spherical-conical high-pressurevesselwith respect to main process limitations of a new technology are considered. The rational shape of the vessel’sgeometry was determined within the conditions imposed by 3D printing technological limitations and analytical dependencies. Analytical relationships are based on the results obtained with the membrane theory of shells. The thickness of the spherical-conical vessel varies along its generator line and is determined by the fourth theory of strength. It is shown that the conditions of strength and technological restriction are always determined by distortion of the median surface in the joining area of conical and spherical parts of the vessel. The rational vesseldesign, consisting of a spherical, transitional and conical parts, allows to create an equal stress state when the ratio of radius to thickness of the sphere tends to infinity. The use of the spherical transition segment makes it possible to reduce the stress concentration in the transition zone from the spherical to the conical part.The geometry of the vessel containing thespherical transition part was determined. In the case of a constant cone thickness, the distortion of the median surface disappears, but the conical part will be underloaded. This design solution considers the technological limitation of the minimum shell thickness and is rational for large radius-to-thickness sphere ratios.

The results are true for spherical-conical vessels, with a sphere thickness-to-radius ratio less than or equal to 0.1 and a printingsurface inclination angle relative to the symmetry axis. They were tested on numerical models of spherical-conicalvessels with different radius-to-thickness ratios of the spherical part and can be recommended for practical implementation.