A study of the stress ratio effects on fatigue crack growth using the unified two-parameter fatigue crack growth driving force

Modelling probabilistic fatigue crack propagation rates for a mild structural steel

“…Local strain-based approaches [5][6][7][8] were originally proposed to model fatigue crack initiation on notched components [9]. A link between the local strain-based approaches to fatigue and the Fracture Mechanics based fatigue crack propagation models has been proposed by some authors [1,[10][11][12][13][14]. Glinka [13] was one of the first researchers to use the local strain approaches to model fatigue crack propagation.…”

“…Glinka [13] was one of the first researchers to use the local strain approaches to model fatigue crack propagation. The original idea of Glinka was later followed and developed by his collaborators, such as Noroozi et al [1,[10][11], using crack tip residual stress concepts to explain stress ratio effects as well as loading interaction effects on fatigue crack growth rates. Peeker and Niemi [12], based on the original idea of Glinka, made also independent contributions, using crack closure concepts to explain stress R-ratio and load interaction effects.…”

“…The underlying concept behind the proposed local approaches for fatigue crack propagation modelling consists of assuming fatigue crack propagation as a process of continuous failure of consecutive representative material elements (continuous re-initializations). Such a kind of approaches has been demonstrated to correlate fatigue crack propagation data from several sources, including the stress ratio effects [1,[10][11][12][13][14]. The crack tip stress-strain fields are computed using elastoplastic analysis, which are applied together a fatigue damage law to predict the failure of the representative material elements.…”

“…The simplified method of Neuber [15] or Moftakhar et al [16] may be used to compute the elastoplastic stress field at the crack tip vicinity using the elastic stress distribution given by the Fracture Mechanics [1,[16][17]. This paper proposes an assessment and extension of the model proposed by Noroozi et al [1,[10][11] to predict the fatigue crack propagation rates, based on local strain approach to fatigue. This model has been denoted as UniGrow model and classified as a residual stress based crack propagation model [18].…”

“…The maximum stress, σmax, mean stress, σm, and the strain range, ε have to be evaluated as the average values at the elementary material block size, ρ*, taking into account an elastoplastic analysis. To compute the elastoplastic stresses and strains at the elementary material blocks ahead of the crack tip, Noroozi et al [1,10] proposed the following analytical procedure:…”