Research on residual stresses after hydrobulging of spherical vessels

This paper describes the residual stress distributions on wide plate specimens intended to simulate the hydrobulging process for the 200 m³ spherical vessel which is the first set for storage of liquefied petroleum gas (LPG) manufactured using dieless hydrobulging technology. The results show that on the inside surface of the spherical vessels after they are hydrobulged, the transversal residual stress is in a compressive state; the longitudinal residual stress has a very small tensile value and sometimes is in a compressive state. These distributions of residual stresses are favourable to prevent the spherical vessel from stress corrosion cracking (SCC) and embrittlement fracture and can improve its fatigue strength. This is a significant advantage of the new dieless hydrobulging technology in guaranteeing safety.