COMPLAS 2023

Modelling of Running Ductile Fracture by Coupling the Phase-Field Evolution with a Local Damage Model

  • Sur, Anne-Sophie (NTNU)
  • Hopperstad, Odd Sture (NTNU)
  • Morin, David (NTNU)
  • Gruben, Gaute (SINTEF Industry)

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The prediction and description of running ductile fracture needs to take into account a variety of complex processes in elasto-plastic material under softening. In this context, we provide a regularised fracture model on the macro-scale considering micromechanical processes in a phenomenological sense to better capture fracture initiation and evolution. Ductile fracture has been described by various local damage models. However, finite element simulations of such a ductile fracture model often suffer from mesh dependence when the damage gets localised. Furthermore, modelling of running ductile fracture on a larger structural scale requires large shell elements, while the suggested regularised fracture model on the smaller scale needs a fine mesh, which makes a scaling method necessary due to the different length scales. To overcome the damage localisation in the fracture model on the smaller scale, we suggest introducing a phase-field variable and coupling it with a local damage model. The damage regularisation is achieved through the phase-field variable. The concept of driving force for the phase-field evolution presented in [1] is adopted and modified in such a way that it can in principle be used with any local damage model. The proposed approach reduces the mesh dependence and can reproduce the observed fracture behaviour. The proposed model is implemented by using the analogy of the phase-field evolution equation to the heat equation, as described in [2]. In this work, ductile fracture is considered in a high strength, 13Cr pipeline steel. Simulation results for different test geometries such as Kahn tear tests and plane strain tests are presented and compared with experimental results. [1] Aldakheel F., Wriggers P., Miehe C. A modified Gurson-type plasticity model at finite strains: formulation, numerical analysis and phase-field coupling.Computational Mechanics, Vol. 62 (4), pp. 815–833, 2018. [2] Navidtehrani Y., Betegón C., Martínez-Pañeda E. A simple and robust Abaqus implementation of the phase field fracture method. Applications in Engineering Science, Vol. 6, 100050, 2021.