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Large strain behaviour of brain tissue in shear: some experimental data and differential constitutive model
L E Bilston1, Z Liu, N Phan-Thien
1Department of Mechanical and Mechatronic Engineering, University of Sydney, Australia. bilston@mech.eng.usyd.edu.au
Abstract:
In this paper, some experimental measurements of the behaviour of bovine brain tissue under large shear strains in vitro are reported, and a constitutive model which is consistent with the data is developed. It was determined that brain tissue is not strain-time separable, showing slower relaxation at higher strains, and that the stresses in shear are not linear with increasing shear strain. The new constitutive model is a differential model, including both an "elastic" term, of the Mooney type and a nonlinear viscoelastic term. The latter allows for the change in relaxation behaviour with strain, by modifying an upper convected multimode Maxwell model with a damping function. The model shows good agreement with the experimental shear results and could be used to describe other types of data.