We present a new theoretical and numerical framework for modelling mechanically-assisted corrosion in elastic-plastic solids. Both pitting and stress corrosion cracking (SCC) can be captured, as well as the pit-to-crack transition. Localised corrosion is assumed to be dissolution-driven and a formulation grounded upon the film rupture-dissolution-repassivation mechanism is presented to incorporate the influence of film passivation. The model incorporates, for the first time, the role of mechanical straining as the electrochemical driving force, accelerating corrosion kinetics. The computational complexities associated with tracking the evolving metal-electrolyte interface are resolved by making use of a phase field paradigm, enabling an accurate approximation of complex SCC morphologies. The coupled electro-chemo-mechanical formulation is numerically implemented using the finite element method and an implicit time integration scheme; displacements, phase field order parameter and concentration are the primary variables. Five case studies of particular interest are addressed to showcase the predictive capabilities of the model, revealing an excellent agreement with analytical solutions and experimental measurements. By modelling these paradigmatic 2D and 3D boundary value problems we show that our formulation can capture: (i) the transition from activation-controlled corrosion to diffusion-controlled corrosion, (ii) the sensitivity of interface kinetics to mechanical stresses and strains, (iii) the role of film passivation in reducing corrosion rates, and (iv) the dependence of the stability of the passive film to local strain rates. The influence of these factors in driving the shape change of SCC defects, including the pit-to-crack transition, is a natural outcome of the model, laying the foundations for a mechanistic assessment of engineering materials and structures.

中文翻译：

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溶解驱动应力腐蚀开裂的相场公式

我们提出了一个新的理论和数值框架，用于对弹塑性固体中的机械辅助腐蚀进行建模。可以捕获点蚀和应力腐蚀开裂（SCC）以及点到裂纹的过渡。假定局部腐蚀是由溶蚀驱动的，并提出了以膜破裂-溶蚀-再钝化机理为基础的配方，以结合膜钝化的影响。该模型首次纳入了机械应变作为电化学驱动力的作用，从而加速了腐蚀动力学。通过利用相场范例解决了与跟踪演化的金属-电解质界面相关的计算复杂性，从而能够精确近似复杂的SCC形态。使用有限元方法和隐式时间积分方案，以数值方式实现电化学-化学-机械耦合公式。位移，相场序参数和浓度是主要变量。进行了五个特别感兴趣的案例研究，以展示模型的预测能力，从而揭示与分析解决方案和实验测量的极好的一致性。通过对这些典型的2D和3D边界值问题进行建模，我们表明我们的公式可以捕获：（i）从活化控制腐蚀到扩散控制腐蚀的过渡，（ii）界面动力学对机械应力和应变的敏感性，（iii ）膜钝化在降低腐蚀速率中的作用，（iv）无源膜的稳定性对局部应变率的依赖性。这些因素对驱动SCC缺陷的形状变化（包括从点到裂纹的过渡）的影响是该模型的自然结果，为工程材料和结构的机械评估奠定了基础。