Numerical simulation of fatigue crack growth in steel structures

为了弥补S-N曲线对焊接钢结构（如船舶、海洋结构和桥梁）疲劳强度评估能力的不足，本课题开发了一种基于疲劳裂纹扩展（起生和扩展）数值模拟的疲劳强度评估新方法。项目具体项目如下：提出了一种用于疲劳裂纹扩展数值模拟的算法。考虑位错理论，建立了由声（零缺陷）应力场引发疲劳裂纹的数值模型。为了验证算法的有效性，进行了数值模拟，并与实验结果进行了比较。提出了一种腐蚀疲劳计算算法。提出了板厚应力分布的常规估计方法。壳型单元有限元分析的计算结果是该方法的输入数据。

In order to recover the insufficient ability of S-N curves for the evaluation of fatigue strength in the welded built-up steel structures, e.g.ship, offshore structures and bridges, a new fatigue strength evaluation procedure based on the numerical simulation of the, fatigue crack growth(initiation and propagation) is developed by this research project.Detailed project items are as follows1.An algorithm to perform the numerical simulation of the fatigue crack growth is proposed.2.An numerical model for the fatigue crack initiation from the sound(zero defect) stress concentration field is constructed by considering the dislocation theory.3.Some numerical simulations are performed and the results are compared with the experimental results in order to verify the algorithm.4.An algorithm for the corrosion fatigue is proposed.5.The conventional estimation method of stress distributions in the plate thickness is proposed.Calculation results of the FE analysis by shell type element is the input data of this method.