The goal of this report focuses on the development of an assessing method for ultimate strength of ship hull plate with corrosion damnification. It is confirmed that corrosion damnification on ship hull plate generally appears as pits with different shape, size and distributing density. According to a long term inspected results for pitting on ship hull plates, all the kinds of pits appearing on the hull plate would be equivalent to semi-spherical shape, conical shape and cylindrical shape. Pitting corrosion results in a quantity loss of the plate material as well as a significant degradation of the ultimate strength of the hull plate due to reducing of the effective thickness of the plate. Accordingly, the model for describing the correlations between the ultimate strength and the corroded volume loss of a corroded plate is firstly proposed based on relative theory. Such model was then completed through numerical experiment by nonlinear finite element analyses for series of corroded plate models.
People have paid increasing attention to the corrosion-caused structural damage in recent half century. Corrosion-caused thickness loss makes the ultimate strength of typical thin-walled ship structural plates degraded significantly. For general corrosion, it is thought that the thickness is uniformly reduced over the entire plate, so the ultimate strength of the corroded plate can be assessed based on the thickness. However, for pitting corrosion, the corrosion form is complicated and the thickness of the whole plate is not uniform. Until now, there is still no acknowledged method to assess the ultimate strength of the plate with pitting corrosion damnification. The method of ultimate strength assessment for the pitted plate has been developed from the effective thickness method to the method in which many factors have been considered to represent the characteristics of pitting corrosion.
