In the second category, the continuum approaches, we find the crack band method21, nonlocal integral damage models22, nonlocal stress-based damage models23, and the more recent class of phase-field models24,25,26,27,28,29,30. Phase-field models are undoubtedly the methods that have seen the highest popularity given their overall accuracy and ease of implementation. In phase-field models, sharp cracks are regularized by a diffused damage field while a variational approach is adopted to obtain evolutionary equations for both the displacement and the damage fields24. The formulation also includes a small and positive length scale parameter so that, in the limit for the parameter approaching zero, the phase-field representation of the crack converges to the original problem of a sharp crack31. The use of a phase-field regularization prevents the need for an explicit tracking of the crack surface discontinuity. It follows that the numerical implementation of the phase-field model is relatively straight-forward when compared to the previously mentioned discrete approaches. An important disadvantage of these models lies in their high computational cost, which follows from the need to solve a coupled system of partial differential equations for both the damage (phase) and the displacement fields30. This limitation becomes even more significant when the phase-field approach is applied for fracture analysis in three-dimensional media. Additionally, phase-field models are subject to an artificial widening effect in the damaged area at the point of occurrence of instability30,32, which is in contrast to the microbranching and crack surface roughening seen in experiments33. A detailed review of phase-field models can be found in34.
Real Pic Simulator 13 Crack31
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