Three-dimensional linear elastic fracture mechanics: from theory to practice

Overview & Synopsis

One current challenge of Linear Elastic Fracture Mechanics (LEFM) is to take into account the non-linearities induced by the crack front deformations. For this, a suitable approach is the crack front perturbation method initiated by Rice (1985). It allows to update the Stress Intensity Factors (SIF) when the crack front of a planar crack is perturbed in its plane. This approach and its later extensions to more complex cases are recalled in this thesis. Applications concerning the deformation of the crack front when it propagates in an homogeneous or heterogeneous media have been considered in brittle fracture, fatigue or subcritical propagation. The crack shapes corresponding to uniform SIF have been derived: cracks with straight or circular fronts, but also when bifurcations exist, with wavy front. For an initial straight crack, it has been shown that, in homogeneous media, perturbations of all lengthscales progressively disappear unless disordered fracture properties yields Family and Vicsek (1985) roughness of the crack front. Extension of those perturbation approaches to more realistic geometries and to coalescence of cracks is also envisaged. Quantitative comparison with experiments is under study. Besides, application of the LEFM and its energetic minimisation principle to crack initiation and morpholo- gies appearing in dierent physical problems (drying retraction of suspensions, impact of a plate, indentation of a lm and geological phenomena) is considered.