Extrusions and intrusions in fatigued metals. Part 1. State of the art and history†

Current state and historical progress in experimental and theoretical studies of surface relief appertaining to persistent slip bands (PSBs) and leading to fatigue crack initiation in cyclically deformed metals is presented as a thorough critical overview. A comprehensive inventory of microscopic techniques used for this study is tabulated chronologically with emphasis to their applicability to polycrystals. The most relevant experimental characteristics concerning surface relief evolution, namely the form of extrusions and intrusions in single- and polycrystalline materials, are surveyed. Theoretical models and computational simulations of extrusion and intrusion formation and fatigue crack initiation are critically reviewed. †In 2003, it was 100 years since J.A. Ewing and J.C.W. Humfrey first documented the nature of early surface fatigue damage in Swedish iron in their paper The Fracture of Metals under Repeated Alternations of Stress published in the journal Philosophical Transactions of the Royal Society of London, Series A [1]. Let this work (Part 1 and 2) commemorate their pioneering effort to understand the physical mechanisms of early fatigue damage.