Analysis of thick-walled spherical shells subjected to external pressure: Elastoplastic and residual stress analysis

• Published in: Proceedings of the Institution of Mechanical Engineers. Part L, Journal of materials, design and applications Journal of materials, design and applications, 2020-01, Vol.234 (1), p.186-197
• Main Authors: Kholdi, Mohsen, Loghman, Abbas, Ashrafi, Hossein, Arefi, Mohammad
• Format: Article
• Language: English
• Subjects: Compressive properties; Deep sea; Elastic limit; Elastoplasticity; External pressure; Hydrostatic pressure; Internal pressure; Performance enhancement; Residual stress; Spherical shells; Stress analysis; Submarines; Thick walls; Thickness; Vessels; Water tanks; Yield criteria; Yield point
• ISSN: 1464-4207; 2041-3076
• DOI: 10.1177/1464420719882958

When cylindrical and spherical vessels are subjected to the internal pressure, tensile tangential stresses are created throughout the thickness, the maximum of which are located at the inner surface of the vessels. To improve the performance of these vessels, autofrettage process has been devised to produce beneficial compressive residual stresses at the inner part of such vessels. The question arises whether the process such as autofrettage can be useful for vessels such as submarines or other thick walled tanks, which are used in deep sea waters and, therefore, subjected to high external hydrostatic pressure causing both radial and tangential stresses to be compressive across the thickness. On the other hand, is the residual stresses created by unloading from an external pressure beyond elastic limit beneficial and enhance their performances? In this study, elastoplastic and residual stresses in a thick-walled spherical vessel under external hydrostatic pressure has been investigated. The material behavior is considered to be elastic-perfectly plastic. Von Misses yield criterion is used to obtain initial yield point and for the ideal elastoplastic regime analytical relations are presented. It has been found that by applying external hydrostatic pressure yielding process will start from inside of the sphere. Finally after unloading, residual tensile stresses are created at the inner part of the vessel which is useful for the vessel. The residual stresses and the condition of reverse yielding is studied in this paper.