B型LNG液舱支座纵骨趾端处表面裂纹扩展计算

Crack propagation calculation of a surface crack at the toe of longitudinal end around the support of B type LNG tank

采用有限元软件对液舱底部支座附近纵骨趾端处表面裂纹进行裂纹扩展分析,得到裂纹扩展过程中应力强度因子的变化,并在BS7910经验公式的基础上拟合出趾端处表面裂纹应力强度因子修正系数经验公式且该公式计算结果与有限元计算结果吻合。针对某型LNG液舱按ABS规范的要求求得组合热点主应力幅值,并构造液舱疲劳热点载荷谱,结合本文给出的应力强度因子计算公式对LNG液舱底部支座纵骨趾端的裂纹扩展寿命进行计算,计算结果满足要求。

Crack propagation of a surface crack at the toe of longitudinal end around the bottom support of B type LNG tank has been analyzed by using finite element software.The stress intensity factors of cracks with different sizes in the process of crack propagation were gotten.Empirical formulas for calculating the SIFs of cracks at the toe of longitudinal end were proposed by fitting these calculated based on the similar empirical formulas for surface crack at toe of T joint in BS7910.And the results by formula calculation accord with the results of finite element calculation well.For a given LNG tank ship,the combined principal stress amplitudes of hot spots were obtained according to the requirements of ABS specification,and the corresponding fatigue load spectrum of the hot spot in the tank was constructed.Combined with the formula of stress intensity factor given in this paper,the crack propagation life of a surface crack at toe of the longitudinal end around the LNG tank bottom support was calculated,and the calculation results met the requirements.