腐蚀疲劳点蚀演化及腐蚀疲劳裂纹成核机制研究

Pit evolution and crack nucleation mechanism study of corrosion fatigue

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。

As an irreversible thermodynamics process, the pit evolution during corrosion fatigue is alwaysaccompanied with energy dissipation of the system. Based on the thermodynamics principle, the exploratorystudy of energy issues for corrosion fatigue pit evolution is carried out. A two-variable model is proposed todescribe the pit evolution, and the potential function during pit evolution is established. The shape parameterof pit as a function of pit depth is derived, and the mechanics that surface energy, elastic energy andelectrochemical energy stored in the system control the pit morphology is analyzed. The energy criterion, inview of the dislocation mechanics of crack nucleation, is introduced to build the critical condition for pittransition to fatigue crack, with its critical pit morphology compared with stress intensity factor criterion. Theresults validate the reasonableness of energy criterion.