工程结构蚀坑的腐蚀疲劳裂纹起始寿命预测

为了研究腐蚀疲劳裂纹在蚀坑处萌生位置差异的本质及预测腐蚀疲劳裂纹起始寿命,采用双参数模型描述点蚀坑形貌,并基于三维有限元模型分析不同点蚀坑形貌下的应力集中情况。基于此,分析了蚀坑深度、深径比及位置等参数对蚀坑不同位置应力集中的影响规律。依据腐蚀疲劳现象学观点,建立了三维双参数点蚀坑腐蚀疲劳裂纹萌生评估模型,分析不同蚀坑形貌下腐蚀疲劳裂纹萌生的临界值。研究表明:控制腐蚀疲劳裂纹萌生的条件主要为蚀坑深度和蚀坑形状;萌生于蚀坑处不同位置的腐蚀疲劳裂纹的临界值均可采用蚀坑临界深度值表示。所建模型的有效性和合理性得到了有效验证,为工程实际中遭受腐蚀疲劳损伤结构的腐蚀疲劳起始寿命预测提供了一种可行性方法。

Prediction of corrosion fatigue crack initiation life of pits in engineering structures

In order to study the essence of the difference of corrosion fatigue crack initiation locations in the pit and predict the corrosion fatigue crack initiation life, the pit morphology was described by the two-parameter model and the stress concentration at different pit morphologies was analyzed based on the three-dimensional finite element model. Then, the influence laws of pit parameters(e.g. depth, depth-diameter ratio and location) on the stress concentration at different positions were investigated. Finally, a three-dimensional two-parameter pit-corrosion fatigue crack initiation evaluation model was established according to the phenomenology of corrosion fatigue, and the critical value of corrosion fatigue crack initiation corresponding to different pit morphologies was analyzed. It is shown that the factors controlling the corrosion fatigue crack initiation include the depth and shape of the pit. The critical values of the corrosion fatigue cracks initiating at different locations in the pit can be expressed by the critical pit depth. The validity and rationality of the proposed model are verified effectively. The research results provide a feasibility method for predicting the corrosion fatigue initiation life of the structures that are damaged by corrosion fatigue in engineering practice.