Elastic characterization of the gerbil pars flaccida from in situ inflation experiments
Faculty of Sciences. Physics
Biomechanics and modeling in mechanobiology. - Berlin
, p. 727-741
University of Antwerp
In hearing science, finite element modelling is used commonly to study the mechanical behaviour of the middle ear. Correct quantitative elasticity parameters are an important input in these models. However, up till now, no large deformation elastic characterization of the pars flaccida, a small part of the tympanic membrane, has been carried out. In this paper, an elastic characterization of the gerbil pars flaccida is presented. The gerbil is used frequently as animal model in middle ear mechanics research. Characterization was done via inverse analysis of in situ static pressure inflation experiments. As a first approach, the pars flaccida was modelled as a linear homogeneous isotropic elastic membrane, which resulted in an average Youngs modulus of E=(41004)kPa . It was found that linear elastic modelling cannot describe inflation stagnation at high pressures. Therefore, in a second approach, the VerondaWestmann hyperelastic model was introduced. This was able to describe curve stagnation, the mean parameters that were found are C1=(3104)kPa and C2=(2502) . Finally, in situ strain was considered in the finite element models which resulted in a better description of the behaviour for small pressures. Incorporating this, the optimal VerondaWestmann parameters are C1R=(2606)kPa , C2R=(1402) for a radial in situ strain of R=(122) . In conclusion, this paper shows that a linear elastic material is not appropriate to describe pars flaccidas behaviour in the quasi-static pressure regime, that the currently used membrane stiffness estimates do not hold for large deformations and that incorporating an in situ strain in the models is necessary for a good description for small static pressures.