Two approaches to predict failure of soft tissue are available. The first is based on a pointwise criticality condition, e.g. von Mises maximum stress, and it is restrictive because only a local state of deformation is considered and the failure criterion is separated from stress analysis. The second is based on damage mechanics where a scalar or tensor parameter is introduced to describe the degradation of material properties during mechanical loading. The damage parameter is an internal variable which magnitude is constrained by a damage evolution equation and a critical threshold condition. Theoretically, the approach of damage mechanics is very flexible and allows reflecting the physical processes triggering macroscopic damage at small length scales. Practically, the experimental calibration of damage theories is far from trivial and, because of that, it is reasonable to look for alternative theories that present the bulk failure in more feasible ways than the traditional damage theories.

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