Predicting failure in soft tissue phantoms via modeling of non-predetermined tear progression

The advantageous, curved trajectory of beveltipped devices in soft tissue is a function of the interplay between material deformation, contact interactions and material failure. Highly detailed modeling of tool-tissue interactions is therefore vital in optimising performance and design. At high resolution, discontinuous failure of soft tissue phantoms has not been demonstrated. An iterative procedure, making incremental additions to the failure path in an otherwise continuous finite element mesh, is presented to achieve this goal. The procedure´s efficacy was demonstrated in two materials including a soft tissue phantom. Failure path is shown to respond well to different and evolving shear and normal stress states. The iterative procedure would thus be ideal for analysing and optimising complex tool-tissue interactions, for instance in needle steering systems, where the path taken by the needle also depends on the progression of a tear which develops ahead of the tip during the insertion process. With the method presented here, this behaviour could be modeled and analysed at an unprecedented resolution.