Numerical simulation of fatigue crack growth in steel structures

为了弥补S-N曲线对船舶、海洋结构、桥梁等焊接组合钢结构疲劳强度评定能力的不足，提出了一种新的基于数值模拟的疲劳强度评定方法。提出了疲劳裂纹扩展(萌生和扩展)的数值模拟算法。2.考虑位错理论，建立了基于声(零缺陷)应力集中场的疲劳裂纹萌生数值模型。3.进行了数值模拟，并与实验结果进行了比较，验证了算法的正确性。4.提出了腐蚀疲劳的计算方法。5.提出了板厚应力分布的常规估算方法。有限元计算结果表明，该方法是可行的壳型单元分析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.