Effects of the Welding Residual Stress on the Grounding Damage Analysis of a Tanker

Vessels are rarely subjected to accidental loads such as the collision, grounding and stranding. But these accidental loads cause a lot of damages to hull structure including a large deformation, fracture, tearing and so on. In case of carrying dangerous goods such as crude oil, these accidents can induce a serious environmental pollution. All ocean-going vessels were made by welding. The welding residual stress is a significant shortcoming of welding remains at the hull structure, even though welding technology in shipbuilding field has provided a variety of advantages, e.g. remarkable shortening of the shipbuilding time. The aim of this paper is to investigate the effects of the residual stress in a grounding accident. When a ship runs aground against a sea-obstacle like a rock, this accident can be classified as a grounding. Among parameters of grounding accident scenarios such as the ship speed, the initial striking point, and loading conditions of the ship, only ship speed varies from 10 to 15 knots under ballast condition with/without consideration of residual stress(this sentence is not clear to the read). The initial striking point is at the bow of the center line of ship. A series of nonlinear numerical simulations with large deformation and fracture were carried out using LS-DYNA. As a result, two cases with residual stress have longer damage length. The difference seems to be relatively small, but not negligible.