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Influence of non‐proportional bending with torsion on fatigue life of 10HNAP steel within the range of crack initiation and propagation
Author(s) -
GASIAK G.
Publication year - 2012
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/j.1460-2695.2012.01691.x
Subject(s) - torsion (gastropod) , materials science , stress intensity factor , amplitude , structural engineering , bending moment , phase angle (astronomy) , pure bending , composite material , bending , fracture mechanics , physics , engineering , optics , medicine , surgery
The paper presents a precise analysis of the influence of non‐proportional loading of specimens on fatigue life during initiation and propagation of fatigue cracks. Simulation of the fatigue life of specimens was based on relations describing propagation rate of the fatigue cracks. The Paris and Forman relations were applied; they were integrated after previous introduction of relationships for the equivalent range of the stress intensity factor ΔK eq and including the phase shift angle ϕ between amplitudes of the bending moment and the torsional moment. Under bending with torsion, range of the equivalent stress intensity factor ΔK eq includes ranges of stress intensity factors for loading modes I and III, i.e. ΔK I and Δ K III . The performed tests of 10HNAP constructional steel under cyclic bending with torsion allowed us to determine the influence of the phase shift angle ϕ on the fatigue life. It has been proved that increase of the phase shift angle from ϕ= 0° to ϕ= 60° and the ratio of amplitude of the bending moment M ag to amplitude of the torsional moment M as equal to 1.33, 2 and 4 cause increase of the fatigue life of the tested specimens. The maximum increase of the fatigue life of specimens made of 10HNAP steel was 73% ( M ag /M as = 2, ϕ= 45°).