Assessment of the period to fatigue macrocrack initiation near stress concentrators by means of strain parameters
A new approach to the experimental assessment of the local strain at a stress concentrator has been presented. It is based on a procedure of notch opening displacement measurements at certain points in the vicinity of a notch related to the effective notch radius ρ eff = ρ + d *, where ρ is the notch radius and d * is a material constant. Different stress concentrators in structural elements were modelled for a wide variation of notch radii (ρ = 0.1–6.5 mm) and different geometries of specimens. Hence, a basic relationship, which directly relates the local strain range Δε* to the period of fatigue macrocrack initiation N i has been established. Thus, by applying the value of Δε* , assessed from a direct measurement at the notch root, it is possible to determine the period N i to initiate a fatigue macrocrack of length a i = d * for some structural components of complicated geometry.
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