Submarine Pressure Hull Collapse Considering Corrosion and Penetrations

The influence of corrosion around a casting in a submarine pressure hull is investigated using nonlinear finite element modelling techniques. The area encompassed by the corrosion patch and the percentage thinning of the pressure hull due to corrosion are varied. For each variation in corrosion patch dimensions, collapse pressures are calculated with and without a ballast pump valve body casting located at the center of the corrosion patch. The extent to which the presence of the casting within a corrosion patch influences collapse pressure is examined and different methods of modelling the casting within the pressure hull are evaluated. The loss of strength caused by corrosion is largely counteracted by the presence of a casting in the corroded region. The casting stiffens the response of the shell plating in that area, causing an increase in collapse pressure. The benefit provided by the casting increased as the percentage thinning of the shell plating increased, increasing the failure load of the corroded hull by as much as 19% for 20% thinning of the shell plating.