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Damage tolerant structures require accurate fatigue crack growth rate models for life prediction. Central to these models are fracture mechanics similitude and empirically gathered growth rates. In this work, standard test methods failed to achieve similitude for 17-4PH stainless steel round-rod but succeeded for plate. Material product form differences are interrogated through constant ΔK tests, crack path analysis, residual stress (RS) characterization, and growth rate simulation. Analyses revealed that quench-induced RS in the round-rod promoted a non-planar, 3D crack path with closure effects. Strategies to mitigate the RS/path effects are evaluated by controlling constraint, closure, environment, and heat treatment.

Corrosion processes are often discussed as stochastic events. Here, it is shown that some of these seemingly random processes are not driven by nanoscopic fluctuations but rather by the spatial distribution of micrometer‐scale heterogeneities that trigger fast reactions associated with corrosion. Using a novel excitable reaction‐diffusion model, corrosion waves traveling over the metal surface and the associated material loss are described. This resulting nonuniform corrosion penetration, seen as a height loss in modeling, exposes buried intermetallic particles, which depending on the local electrochemical state of the surface trigger or block new waves. Informed by quantitative experimental data for the Mg–Al–Zn alloy AZ31B, wave speeds, wave widths, and average material loss are accurately captured. Morphogenic mitigation based on wave‐breaking microparticles is also simulated. While AZ31B corrosion is identified as a process driven by rare‐wave events, this study predicts several other corrosion regimes that proceed via spots or patchy patterns, opening the door for new protection, design, and prediction strategies. [ABSTRACT FROM AUTHOR]

The influence of applied loading rate (dK/dt) on stress corrosion cracking (SCC) behavior in annealed 304L stainless steel immersed in 4.7 M MgCl2 solution was assessed at varying temperatures from 23 °C to 70 °C. Measured crack growth rates obtained under rising K loading (dK/dt > 0) are compared to those obtained during static K testing. A rising K-based loading protocol was found to yield more conservative crack growth rates across all temperatures, with the variation in crack growth rates (and therefore the dependence in loading rate) decreasing with increasing environmental severity. [ABSTRACT FROM AUTHOR]