Detailed finite element modelling of deep needle insertions into a soft tissue phantom using a cohesive approach

Abstract

Detailed finite element modelling of needle insertions into soft tissue phantoms encounters difficulties of large deformations, high friction, contact loading and material failure. This paper demonstrates the use of cohesive elements in high-resolution finite element models to overcome some of the issues associated with these factors. Experiments are presented enabling extraction of the strain energy release rate during crack formation. Using data from these experiments, cohesive elements are calibrated and then implemented in models for validation of the needle insertion process. Successful modelling enables direct comparison of finite element and experimental force–displacement plots and energy distributions. Regions of crack creation, relaxation, cutting and full penetration are identified. By closing the loop between experiments and detailed finite element modelling, a methodology is established which will enable design modifications of a soft tissue probe that steers through complex mechanical interactions with the surrounding material.

Keywords::

• needle insertion
• cohesive elements
• soft tissue
• finite element method
• fracture toughness
• flexible probe

Acknowledgements

The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement no. 258642-STING. The authors are also grateful for the support of EPSRC grant EP/E040918/1 and the EU-FP7 Project ROBOCAST (FP7-ICT-21590).