基于奇异强度理论的疲劳特性评估方法

疲劳是海洋结构物破坏的重要因素,为简化舰船结构疲劳评估方法,基于线弹性断裂力学和切口应力强度理论,针对典型薄板结构研究拐角节点处的应力强度,分析结构形式,利用ANSYS有限元模拟和MathCAD函数拟合,分别给出计算应力强度因子的＂奇异权函数法＂和＂奇异等效裂纹法＂的研究方法,同时给出简便算法和经验公式。进而应用Paris裂纹扩展法则进行结构奇异强度疲劳特性评估,并结合S-N曲线分析拐角节点处的应力集中,得到与结构尺寸相关的＂奇异应力集中系数＂函数。最后,针对切口应力,提出有限元分析所需要的＂奇异应力等效取值点＂的参考位置。希望能将奇异强度理论纳入船舶结构疲劳强度校核规范中做参考。

Fatigue Characteristics Assessment Method Based on Singularity Strength Theory

Fatigue is a key factor in the destruction of marine structures, and this paper studies the stressintensity of typical sheet structures for corner nodes based on linear elastic fracture mechanics and thenotch stress intensity theory to simplify the conventional ship structural fatigue assessment method. Struc-tural analysis is performed by using ANSYS finite element simulation, the MathCAD function fitting, re-search methods of ＂singular weight function method＂ and ＂singular equivalent crack method＂ to calculatestress intensity factors. Finally, simple algorithms and empirical formulas are given. Then, the fatigue life iscalculated based on Paris crack propagation law, and S-N curves are combined to analyze the stress con-centration factors. The relationship between the ＂singular stress concentration factor＂ and the ＂singularitystrength＂ is investigated. Finally, singular stress points for equivalent notch stress are given to realize the fi-nite element analysis. It is hoped that the singular strength theory can be brought into ship structural fa-tigue strength check specification for reference.