Ductile crack growth using cohesive GTN model
Résumé
This chapter presents a three-dimensional simulation of ductile crack growth using a recent GTN cohesive approach. A cohesive-volumetric finite element approach is adopted. The behavior of the material is characterized by a hardening bulk constitutive law inside the finite elements together with a softening traction-separation law at the interfaces between elements. The traction-separation law recently proposed by [1] rests on the micromechanical Gurson-Tvergaard-Needleman model for ductile damage and fracture, and the reduced kinematics of a surface. It takes into account the effect of local I1 and J2 stress invariants via a dependence of the cohesive model to the surrounding bulk stress. The efficiency of this cohesive-GTN model is underlined through the 3D numerical simulation, using XPER code [35], of a compact tension test. The results show a strong tunneling in the crack front shape. The crack propagates faster at the midsection than at the side-surface. Large gradients of local stress and strain through the specimen thickness during crack growth are observed. Especially, the stress triaxiality is higher at the midsec-tion than at the side-surface, leading to more damage in the cohesive zone due to cavity growth.