Effect of weld-induced imperfections on the ultimate strength of an aluminium patrol boat determined by the ISFEM rapid assessment method

Abstract

Marine-grade aluminium alloys are being increasingly used as a hull material of naval vessels, particularly in the case of high-speed patrol vessels for which the requirement for reduced structural weight is critical. Combined with the drive for weight reduction, the demand for operations of aluminium vessels in harsher seaway environments has led to increased interest in the application of limit-state design and analysis procedures, which require evaluation of the ultimate strength of the hull girder. This paper investigates the use of the state-of-the-art rapid assessment procedure ISFEM (intelligent supersize finite element method) to examine the ultimate hull-girder strength under vertical and horizontal bending of a metal inert gas welded aluminium midship section with plate and stiffener scantlings typical of a high-speed patrol vessel. The analysis investigates the effect on ultimate strength of weld-induced imperfections including plate and stiffener distortion, residual stresses and material softening in the weld heat-affected zone.