Dynamic fracture simulations through strain injection techniques

J. OLIVER,; A E. HUESPE; LLOBERAS-VALLS, O.; DIAS I.

Nantes

Conferencia; CFRAC 2017 International Conference on Computational Fracture and Failure of Materials and Structures; 2017

ECCOMAS

A methodology for the simulation of dynamic crack propagation based on Finite Elements with Embedded discontinuities (E-FEM) is presented . Both strain and displacement discontinuities are injected within the finite element through a kinematic enrichmentconsidering discontinuous strain and displacement modes. The technology has been already utilized in a wide number of quasi-static tests in [1, 2] and recently adopted for thestudy of dynamic fracture propagation in [3]. The strain injection technology is complemented with the crack path field tracking algorithm which computes the trace of the strongdiscontinuity and provides an extra robustness to the crack modeling approach. Due tothe intra-elemental character of the kinematic enrichment, the overall computational costturns to be remarkably lower (up to three orders of magnitude lower in terms of FE discretization) than other existing techniques based on supra-elemental crack modeling, e.g.phase-field or gradient damage approaches.Upon increasing loading rates, crack propagation instabilities, such as crack curvingand branching, have been observed and their impact in terms of the resulting crack pattern, i.e. crack surface, and dissipated energy is studied. Results turn to be reasonablyinsensitive to spatial and temporal discretizations provided that they suffice to model theunderlying physics and a convergent behavior, in terms of the dissipated energy, is observed upon refinement of the FE mesh and adopted number of time steps. An interestingcorrelation is found between the maximum experimental crack speed and the maximumdissipation of a single crack at the onset of branching considering that the energy is instantaneously released which can be used to estimate the crack speed upon branching basedon the overall dissipation which is a remarkably less fluctuating field