Hyperelastic models for the analysis of soft tissue mechanics: definition of constitutive parameters

The analysis of the interaction phenomena occurring between biorobots and biological tissues requires in-depth knowledge of the biomechanical response of tissues. Most phenomenological models are based on hyperelastic formulation and this entails a careful evaluation of the model constitutive parameters, which are defined on the basis of data obtained from experimental tests. The choice of the test to be developed depends on the tissue characteristics to be studied and the procedure to be used to define the parameters . The aim of the present work is to describe a procedure used to define constitutive parameters for hyperelastic soft tissue constitutive models by considering combinations of data from uniaxial, equibiaxial and shear testing conditions of tissue specimens and to discuss the results obtained. The parameters are estimated using a stochastic optimization procedure, considering the complex behaviour of the cost function. The mechanical tests to be adopted and their combination are discussed with regard to the reliability and efficiency of the procedure to be used in the numerical modelling of tissue-robot interaction phenomena.