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Abstract

Marine structures are susceptible to failure mechanism due to presence of both external and internal loads. A submarine is manufactured with several circular hull sections welded together and forming an entire hull. A hull section consists of several bowed metal sheets welded together and strengthened by T-section rings which are welded at repeated spaces. T-section rings are fabricated using numerous web and flange plates and curved correctly by plastically bending before welding. Fatigue life of a submarine hull is dependent on load produced from hull contraction due to surrounding hydrostatic pressure, as well as residual stress present without any applied load. Numerical simulation can be used to calculate stresses generated from hydrostatic pressure. However, predicting residual stresses resulting from bending and welding processes can be more involved. Moreover, the predicted stresses need to be validated by measurement. Incremental centre-hole drilling (iCHD) is broadly applied technique to measure residual stress. The iCHD technique however is limited to near surface measurement which can contribute to misleading structural integrity assessment. On the other hand an over-conservative estimate of stress due to welding process can lead to reduced life estimate. It is thus imperative to analyse residual stresses accurately and deep into metal parts in order to move away from decade old conservative estimates. This paper reviews various techniques available for analysing residual stress field and considers multiple techniques with an aim to provide an optimum solution.

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