Significance of strain rate-dependence in modelling of organic materials

This paper explores the significance of the inherent strain rate-dependence of many biological materials. Such characteristics are pertinent to computational modelling of these materials for the purposes of surgical robotics and simulation. A pair of 2-dimensional fmite element models of the human brainlvenmcle system are developed and used to analyse the brain structural disease, hydrocephalus. The models are geometrically identical, and both incorporate a linear biphasic material model for the brain parenchyma. Model I is assigned a Young modulus value, Eo = 3156Pa. based on the instantaneous elastic respnse derived from a hyperviscoelastic model. Model 2 accounts for the extremely slow loading characteristic of the disease and a revised modulus value of E, = 584.4Pa is assigned. This significant variation in stifhess generates similar differences in the simulation results. The conclusion is that consideration of the in ths ic strain rate-dependence of organic materials is vital to the satisfactory modelling ofsuch materials, and hence significant to surgical robot performance.