Some Consideration on the Anisotropy of Fatigue Limit in a Rolled Steel Plate, Based on the Observation of Fatigue Process in Electropolished Specimens

Abstract

The purpose of this study is to investigate the dominant factors controlling the anisotropy of fatigue limit of rolled materials under bending or torsional stress, by observation of fatigue process in electropolished specimens taken from a rolled steel plate. 1) The anisotropy of fatigue limit was observed only in the cases when the origin of facture was the inclusions and that of the limiting stress for slip bands initiation was not observed in spite of marked directionality of yield stress. 2) The anisotropy of fatigue limit was more remarkable in bending than in torsion. 3) The anisotropy of bending fatigue limit of notched specimens was observed when ρ> ρ₀ (ρ:notch radius, ρ₀ :ρ at the branch point) and not observed when ρ< ρ₀- that is, in the case when the non-propagating cracks existed.