Fatigue reliability of a web frame subjected to random non-uniform corrosion wastage

• Reliability assessment of a ship welded structure subjected to corrosion and fatigue is done.
• A three-dimensional finite element model is generated.
• Randomly corroded surface geometries are simulated by the use of Monte Carlo simulation.
• Hot-spot stresses around welded details in a stiffener frame joint are determined.
• Fatigue reliability is modelled as a series system of correlated components.

An approach for reliability assessment of a welded structure subjected to corrosion degradation and fatigue is developed. The objective of this work is to evaluate the fatigue reliability of a complicated ship welded structure subjected to random non-uniform corrosion and fatigue loading simultaneously. A three-dimensional finite element model accounting for randomly distributed non-uniform corrosion wastage based on non-linear time-dependent model is generated. Randomly corroded surface geometries are simulated by the use of the Monte Carlo simulation technique for different service times of corrosion wastage and linear elastic finite element analysis are performed. Hotspot stresses around welded details on a web frame joint are determined. Based on nonlinear regression analysis, the time-dependent functions for the hot-spot stresses affected by corrosion deterioration are fitted. The relationship between the structural fatigue damage and corrosion deterioration caused by corrosion thickness wastage at different times is quantified employing S–N approach. The statistical properties of fatigue damage and service life of critical hot-spots in the web frame welded joint are estimated taking into account random non-uniform time-dependent corrosion wastage. The fatigue reliability of the web frame welded joint during its service life is modelled as a series system of correlated components using the Ditlevsen bounds method.