Plasticity and damage heterogeneity in fatigue

Modelling the role of non-metallic inclusions on the anisotropic fatigue behaviour of forged steel

“…These two approaches are combined in a probabilistic framework that takes into account the competition between the two mechanisms. The probability of crack initiation in the material matrix is estimated using a two scale model based on the accumulated plastic deformation at the local scale [15].The probability of crack propagation from initial defects is estimated using the LEFM framework. The defect is considered as a pre-existing crack and is assumed to propagate under a mode I opening mode.…”

“…It is only valid when one slip system is active in the reference volume. However, observations carried 10 out close to the fatigue limit show that mesoplasticity and subsequent mesodamage can occur in many different grains on different glide systems [15]. Moreover, the loaded volume can be significantly larger than the reference volume.…”

“…The authors propose to apply a simple strength theory classically used for composites such as TsaiHill or Tsai-Wu theory. 4 For polycrystalline materials subjected to high cycle fatigue, some authors [4,5,15,16] use a multi-scale approach, combined with the concept of elastic shakedown to model the role of local plasticity on the fatigue limit. A fatigue limit is assumed to occur if and only if the initially plastically deforming grains recover an elastic response after cycling.…”

“…The loading conditions investigated included: (a) push-pull tensile loads (load ratio of R=-1), (b) tensile uniaxial loads (R=0.1) and (c) 15 reversed torsion (R=-1). Twenty specimens were used for each condition to define the fatigue limit at 10 7 cycles with the staircase method.…”

Prise en compte du rôle des inclusions non métalliques dans le comportement anisotrope en fatigue d’aciers forgés

“…La probabilité de rupture P F1 associée à un amorçage possible au sein de la matrice est prise en compte via l'approche de Morel [4]. Cette approche se base sur les hypothèses d'adaptation élastique à l'échelle mésoscopique et du maillon le plus faible appliqué sur l'ensemble des plans d'un volume élémentaire représentatif.…”