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Keynote speech (by Prof. J. D. Achenbach)

Pre-detection evaluation of growth of fatigue and stress corrosion cracks

J. D. Achenbach

Northwestern University, USA


Fatigue cracks under cyclic loading and stress corrosion cracks in an aqueous environment are very undesirable damage mechanisms in metal structures. For fatigue cracks, there is a lengthy period of pre-crack damage before actual formation of a crack, which is difficult to detect, but once a crack has nucleated its growth process can be fast, and it is therefore important that a fatigue crack is detected in a timely fashion. Stress corrosion cracks form slowly under the chemical process of anodic dissolution in the early stages followed by combined anodic dissolution and hydrogen embrittlement in the later stages, which culminates in fracture. In this fracture we will examine pre-detection evolution of growth of fatigue and stress-corrosion cracks, as a necessary preliminary to effective detection of such cracks. Since these processes are not completely deterministic, we will also consider probabilistic methods to obtain pre-detection for diagnostics and prognostics.