腐蚀疲劳点蚀演化及腐蚀疲劳裂纹成核机制研究

作为一种不可逆的热力学过程，腐蚀疲劳的点蚀演化伴随着体系能量的耗散。文章基于热力学原理，对腐蚀疲劳点蚀演化过程中的能量问题进行探索性研究。引入双变量点蚀模型，建立点蚀演化过程中体系热力学势函数，推导了点蚀形状参数在演化过程中的变化方程，并分析了体系应变能、表面能和电化学能对点蚀演化形貌的影响机制及规律。根据裂纹成核位错机理建立了腐蚀疲劳裂纹成核临界条件的能量准则，并与应力强度因子准则进行比较，分析结果验证了能量准则的合理性。

Pit evolution and crack nucleation mechanism study of corrosion fatigue

As an irreversible thermodynamics process, the pit evolution during corrosion fatigue is always accompanied with energy dissipation of the system. Based on the thermodynamics principle, the exploratory study of energy issues for corrosion fatigue pit evolution is carried out. A two-variable model is proposed to describe the pit evolution, and the potential function during pit evolution is established. The shape param-eter of pit as a function of pit depth is derived, and the mechanics that surface energy, elastic energy and electrochemical energy stored in the system control the pit morphology is analyzed. The energy criterion, in view of the dislocation mechanics of crack nucleation, is introduced to build the critical condition for pit transition to fatigue crack, with its critical pit morphology compared with stress intensity factor criterion. The results validate the reasonableness of energy criterion.