Study On Stress Intensity Factor Evaluation Method Of Ship Hull Structure With Double Crack Damage

Crack damage,which contains the damage degree of crack structure,is one of the common damage forms of ship and offshore structures.The crack damage is determined by numerical simulation normally which is complicated.In engineering,some evaluation methods like Newman formula are used to calculate the Stress Intensity Factor(SIF)at the crack tip which demands highly for crack structure data.However,the usual numerical methods are very complicated,and the Newman formula and other engineering evaluation methods have higher requirements on the crack structure data.Therefore,the existing evaluation methods need to be improved in some respects,such as avoiding tedious measurements,calculating SIF values with simple data,then it will be convenient to evaluate SIF values of cracked structure in project.Some academicians have proposed evaluation method basing on the maximum crack opening displacement(MCOD)to solve it,but its application scope is small.If the scope is expanded,it will be of great significance to engineering application.This paper mainly studies the typical structure of ship and offshore structures,plate and T-butt welded joint,calculating SIF values of cracked structure through MCOD.The main contents include the following parts:(1)Theoretical deduction and solving method of point SIF of flat surface with single crack.Solution of calculating point SIF by FEM.(2)Study SIF of plate with two crack in the same length and shape ratio and same cracks;then propose estimation method and formula of SIF of common double collier cracks.(3)Study SIF of T-butt welded joint with single crack and propose estimation method of point SIF of flat surface on account of MCOD,basing on the solving method of SIF of plate with single crack and considering the influence of welding structure.(4)Study SIF of T-butt welded joint with two cracks in the same length and shape ratio and same cracks.Propose solution and relevant formula of SIF of T-butt with double cracks.In this paper,SIF of a cracked plate and a T-butt welded joint are studied in detail,the calculation method of stress intensity factor of corresponding structure is given.