An experimental study on fatigue crack propagation life of T-joint fillet specimen considering residual stress under storm loading

Fatigue crack propagation life assessment of a cargo hold is an overriding consideration in the design of marine vessel such as crude oil, LNG, and LPG carriers. This paper studies the crack propagation life of T-joint welded structure on which typical fatigue cracks are frequently initiated when the marine vessels experience the storm load. Welding residual stresses are calculated to investigate its effects on the fatigue life. Thereafter the residual stress distribution is applied to the AFGROW life prediction program which incorporates the loading, the welding residual stress, and the geometric shape of the structure. The fatigue tests of the T-joint welded specimen under storm loading show the beach mark clearly generated on the cut section of the specimen. The crack propagation life estimated based on the beach mark are compared with that of AFGROW to validate the life prediction. Evaluation of the remaining service is discussed in order to allow the remaining fatigue lifetime to be estimated for the marine vessel's cargo hold if the random load or the storm load is introduced to the vessel.