Quantitative Evaluation of Environmentally Assisted Cracking: A Survey of Developments and Application of Modeling Concepts

In recent years there has been a great impetus for the development and application of quantitative methods to correlate and predict the crack initiation and propagation response of materials and structures under the joint action of mechanical loads and the environment. In this paper, after briefing the need and objectives of such methods, some of the current methods—especially, in corrosion fatigue, creep-fatigue, and damage accumulation—and the underlying concepts are critically examined; the main objective of this examination was to identify, and build upon, useful ideas for furthering the state-of-the-art. As a convenient point of reference, the presentation and discussion emphasize the models and concepts, recently developed by the author, for the quantitative evaluation of intergranular stress corrosion cracking (IGSCC); these are based on the premise that the IGSCC damage is related to the imposed strain rate under static as well as dynamic loading situations. In particular, it is concluded that the cumulative (continuum) damage approach currently offers a promising means for evaluating the crack growth response when the concept of effective stress is integrated to account for the loss of load-bearing area (due to the cracking). The significance of these models and concepts is briefly discussed in relation to the plausible mechanistic considerations including film-rupture ideas and the electrochemistry. Also, the logical framework of the modeling is made clear in relation to its engineering application, and subsequent future work is indicated.