Open AccessOn fatigue behaviour of two spring steels. Part II: Mathematical models
Author(s) -
Donka Angelova,
Roumyana Yordanova,
T. Lazarova,
Svetla Yankova
Publication year - 2016
Publication title -
frattura ed integrità strutturale
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.368
H-Index - 19
ISSN - 1971-8993
DOI - 10.3221/igf-esis.37.34
Subject(s) - spring (device) , structural engineering , spring steel , materials science , mechanical engineering , forensic engineering , engineering
Symmetric fatigue in two spring steels is investigated in three groups of specimens. One of the\udgroups (Steel EN10270-1SH/ DIN 17223C – C 0.82%, Mn 0.76%, Si 0.26%) has experienced rotating-bending\udfatigue in air, and the other two groups (Steel BS250A53/ DIN 55Si7 – C 0.56%, Mn 0.81%, Si 1.85%), torsion\udfatigue in-air and corrosion environment. All experiments include testing to fracture, applying acetate-foil\udreplication technique, replica monitoring of short crack surface growth, length measuring of propagating cracks,\uda, at the corresponding number of fatigue cycles, N. Data obtained from replica monitoring are presented in\udplots “Crack lengths, a – Cycles, N”, and used for calculating fatigue crack growth rates, da/dN, and graphical\udpresentations “Crack growth rates, da/dN – Crack lengths, a”. A mathematical description of da/dN – a is\udpresented by introducing a parabolic-linear model in different versions for each of the steels. The model\udversions are verified through comparing the experimental fatigue lifetimes with those calculated by the proposed\udmodel version