Non-uniform corrosion prediction of stiffened plates due to interactions with mechanical stresses

Abstract

Corrosion is recognised as a mechanism which significantly degrades structural integrity. For example from open literature, area coverage of 30% with through-thickness pits would reduce the ultimate collapse strength of a steel plate (800 mm x 800 mm x 15 mm) by up to 50%. By applying some counter measures, such as coatings and cathodic protection, the time before corrosion initiates and the area over which it spreads can be reduced. However, failures in the counter measures can still occur due to deformation from the structural loading or accidental damage and the corrosion inevitably will still occur. Hence an accurate prediction model to assess the corrosion behaviour is essential, to determine what corrosion is likely to occur, how this will propagate and the effect it will have on the ultimate collapse strength. To do this most corrosion prediction models rely on historical datasets taken from a small range of ships in a limited range of conditions. These models give little insight into what happens when the conditions change especially the interaction between mechanical stresses and corrosion growth, termed mechano-electrochemical induced corrosion. It is difficult to tell from the empirical models whether the data is gathered from areas of high or low stress or how much this will change the rate of corrosion growth. In this study, we included the effect of stress on a Weibull function, and this stress factor is based on electrochemical measurements taken from open literature. This corrosion model is then embedded into a nonlinear finite element model of a steel stiffened plate in seawater. The thickness reduction of each discretised element is assessed as a function of stress and time. The simulation results show dynamic changes in thickness reduction for each element in the corroded area which takes on a bench-shaped form, similar to what has been found in reality.

More information

Identifiers

ORCID for Eko Charnius Ilman: orcid.org/0000-0002-9011-7733

ORCID for Julian Wharton: orcid.org/0000-0002-3439-017X

ORCID for Yikun Wang: orcid.org/0000-0001-5619-7795

ORCID for Adam Sobey: orcid.org/0000-0001-6880-8338

Catalogue record

Export record