The aim of the present work is to study the stabilizing effect of the nonuniformity of the stress field on the cohesive cracks evolution in two-dimensional elastic structures. | Vietnam Journal of Mechanics, VAST, Vol. 40, No. 4 (2018), pp. 349 – 375 DOI: A GENERALISATION TO COHESIVE CRACKS EVOLUTION UNDER EFFECTS OF NON-UNIFORM STRESS FIELD Tuan-Hiep Pham1,∗ , J´erome ˆ Laverne2 , Jean-Jacques Marigo3 1 ´ CEA, Universit´e Paris-Saclay, DEN, Service d’Etudes des Mat´eriaux Irradi´es, France 2 EDF R&D, Laboratoire National d’Hydraulique et Environnement, France 3 CNRS, Ecole Polytechnique, Laboratoire de M´ecanique des Solides, France ∗ E-mail: Received Frebuary 07, 2018 Abstract. The aim of the present work is to study the stabilizing effect of the nonuniformity of the stress field on the cohesive cracks evolution in two-dimensional elastic structures. The crack evolution is governed by Dugdale’s or Barenblatt’s cohesive force models. We distinguish two stages in the crack evolution: the first one where all the crack is submitted to cohesive forces, followed by a second one where a non cohesive part appears. Assuming that the material characteristic length dc associated with the cohesive model is small by comparison to the dimension L of the body, we develop a two-scale approach, and using the complex analysis method, we obtain the entire crack evolution with the loading in a closed form for the Dugdale’s case and in semi-analytical form for the Barenblatt’s case. In particular, we show that the propagation is stable during the first stage, but becomes unstable with a brutal jump of the crack length as soon as the non cohesive crack part appears. We discuss also the influence of all the parameters of the problem, in particular the non-uniform stress and cohesive model formulations, and study the sensitivity to imperfections. Keywords: cohesive zone model, stress gradient, crack evolution. 1. INTRODUCTION Griffith’s theory of fracture [1] is based on the concept of critical energy release rate Gc which comes from the fundamental but somewhat too restrictive assumption .
