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Crack growth rates and microstructure feature of initiation region for very‐high‐cycle fatigue of a high‐strength steel
Author(s) -
Hu Yuanpei,
Sun Chengqi,
Hong Youshi
Publication year - 2018
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.12811
Subject(s) - materials science , microstructure , scanning electron microscope , transmission electron microscopy , amplitude , bending , high strength steel , composite material , cycling , structural engineering , paris' law , metallurgy , fracture mechanics , crack closure , engineering , optics , physics , nanotechnology , archaeology , history
The S‐N data up to very‐high‐cycle fatigue (VHCF) regime for a high‐strength steel were obtained by fatigue tests under constant amplitude and variable amplitude (VA) via rotating bending and electromagnetic resonance cycling. Crack initiation for VHCF was from the interior of specimens, and the initiation region was carefully examined by scanning electron microscopy and transmission electron microscopy. Crack growth traces in the initiation region of fine‐granular‐area (FGA) were the first time captured for the specimens under VA cycling by rotating bending. The obtained crack growth rates in FGA were upwards to connect well with those in fish‐eye region available in the literature and were associated well with the calculated equivalent crack growth rates in FGA. The observations of profile samples revealed that FGA is a nanograin layer for the specimens under VA cycling, which is a new evidence to support the previously proposed “numerous cyclic pressing” model.