Microstructure-sensitive computational modeling of fatigue crack formation

Recent trends towards simulation of the cyclic slip behavior of polycrystalline and polyphase microstructures of advanced engineering alloys subjected to cyclic loading are facilitating understanding of the relative roles of intrinsic and extrinsic attributes of microstructure in fatigue crack formation, comprised of nucleation and growth of cracks at the scale of individual grains or phases Modeling of processes of early stages of fatigue crack nucleation and growth at these microstructure scales is an important emerging frontier in several respects First, it facilitates analysis of the influence of local microstructure attributes on the distribution of driving forces for fatigue crack formation as a function of the applied stress state This can support microstructure-sensitive estimates of minimum life, as well as characterization of competing failure modes. Second, it can inform modification of process route and its manifestations (e g, residual stress, texture) to alter microstructure in ways that promote enhanced resistance to formation of fatigue cracks Third, microstructure-sensitive modeling, even conducted at the mesocopic scale of individual grains/phases, can facilitate parametric design exploration in searching for microstructure morphologies and/or compositions that modify fatigue resistance Fourth, such technologies offer promise for integration with advanced nondestructive evaluation methods for prognosis and structural health monitoring Finally, as a longer term prospect in view of uncertainties in modeling mechanisms of cyclic slip, clack nucleation and growth, such modeling can serve to support more quantitative predictions of fatigue lifetime as a function of microstructure We first discuss computationally based microstructure-sensitive fatigue modeling in the context of recent initiatives in accelerated insertion of materials and integration of computational mechanics, materials science, and systems engineering in design of materials and structures We then highlight recent application of such strategies to Ni-base superalloys, gear steels, and alpha-beta Ti alloys, with focus on the individual grain scale as the minimum length scale of heterogeneity Finally, we close by outlining opportunities to advance microstructure-sensitive fatigue modeling in the next decade. (C) 2010 Elsevier Ltd All rights reserved.