A Study About the Evolution of 3D Crack Tunneling and the Corresponding Cohesive Zone Relations

Abstract

Fracture properties in 3D crack propagation can change drastically because of the changes in stress triaxiality when fracture is accompanied by significant plasticity. The Gurson–Tvergaard–Needleman constitutive behavior is introduced in this work into properties of a cohesive zone model (CZM). Cohesive strength and fracture energy are considered impacted by triaxiality. The shape functions of the cohesive relation are also considered here a function of the stress triaxiality, which is a novelty introduced in this work. Comparison with experiments is done considering a compact tension test of a 7150-T651 aluminum, taken from the literature. This work demonstrates that tunneling of the crack front and rupture loading depend on the CZM shape functions. Correct evolution of these functions with propagation and along the thickness of the specimen is naturally captured by formulation. Finally, the present work demonstrates initial volume of porosity/second phases and the critical coalescence volume change tunneling and cohesive relations substantially.