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Fracture mechanical characterization of the initiation and growth of interior fatigue cracks
Author(s) -
StanzlTschegg S. E.
Publication year - 2017
Publication title -
fatigue and fracture of engineering materials and structures
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.887
H-Index - 84
eISSN - 1460-2695
pISSN - 8756-758X
DOI - 10.1111/ffe.12622
Subject(s) - materials science , fracture (geology) , paris' law , crystallite , characterization (materials science) , metallurgy , alloy , composite material , fracture mechanics , structural engineering , crack closure , engineering , nanotechnology
The formation and growth of interior fatigue cracks have been studied thoroughly during the last decades, due to the high practical importance of accurate predictions about the fatigue lives of structures and machine components. This is of special interest in the VHCF regime, for which the ultrasonic fatigue method is especially useful. Fracture mechanical values and lifetimes can be measured at constant and variable amplitudes . Endurance limits and Δ K thresholds can also be determined very quickly (e.g. 10 10 cycles within a few days). Three different materials were studied. For chromium steel, internal crack formation and a fracture mechanical analysis of its growth were carried out. For a specially manufactured Mg alloy, microstructural features leading to interior cracks were analysed. Finally, for polycrystalline high‐purity copper, the conditions for interior‐crack formation and growth were determined. The utilization of FE‐SEM microscopy assisted in interpreting the prevailing mechanisms responsible for endurance limits, lifetimes and fatigue‐crack growth thresholds.