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对氢致钢内部疲劳裂纹的萌生和扩展进行了数值模拟.首先用有限元法分析了氢在疲劳载荷作用下向钢中缺陷处扩散富集的过程,然后计算得到氢含量分布结果.根据夹杂理论将氢富集区视为在缺陷附近分布的弹性夹杂,用有限元法计算得到的氢含量场求出夹杂处的应力强度因子,进而建立疲劳裂纹萌生和扩展的判据.比较了在不同加载条件下氢致疲劳裂纹萌生和扩展的规律.用梯形法修正了Sofronis和McMeeking的瞬态扩散有限元公式,发现用梯形法可以缓解加载初期较高的浓度梯度和应力梯度引起的计算结果震荡的情况,这对于计算开裂判据是十分重要的.最后讨论了提高模拟精度和改进模型的方法.
The initiation and propagation of internal fatigue crack in hydrogen-induced steel were numerically simulated.Firstly, the process of hydrogen diffusion and enrichment into defects in steel was analyzed by finite element method, and then the hydrogen content distribution was calculated.According to the inclusion The hydrogen enrichment zone is regarded as the elastic inclusions distributed near the defects, and the stress intensity factor at the inclusions is calculated by the hydrogen content field calculated by the finite element method, and then the criterion of fatigue crack initiation and propagation is established. The law of hydrogen induced fatigue crack initiation and propagation under the loading condition was modified by trapezoidal method, and the transient diffusion finite element formula of Sofronis and McMeeking was corrected by trapezoidal method. It was found that the trapezoidal method can mitigate the shock caused by the higher concentration gradient and stress gradient Which is very important for calculating the crack criterion.Finally, the methods to improve the simulation accuracy and improve the model are discussed.