Soft Tissue Modeling

In order to carry out representative FSI simulations, realistic material models for the soft tissue are required. WP2 will provide WP3 and WP4 with material properties required to model the interaction between soft tissue and fluid in the upper airways. There exist several useful mathematical models for tissue modeling at continuum level, see e.g. [11]. However, test data of mechanical response of biological soft tissue is very scarce. Recently, the Department of Structural Engineering at NTNU has manufactured a biaxial test rig that can test small pieces of soft tissue in different ambient conditions (air, solvent, different temperatures). The load along the two orthogonal axes can be applied cyclically in-phase or out-of-phase. With this, we have the possibility to determine our own test data that is used in estimating the parameters employed with the constitutive material models. We also have previous experience with tests and parameter estimation [12]. The material models are implemented in commercial software such as ABAQUS, or in tailor-made finite element programs. With this, we have general 2D or 3D material models. One can also use the general models to generate simplified 1D or 0D structural models (springs, dampers) that can be employed in simplified FSI simulations.

• [11] B. Skallerud, V. Prot, and I. Nordrum, “Modeling active muscle contraction of mitral valve leaflets during systole: a first approach,” J Biomechanics and Modeling in Mechanobiology, vol. 10, pp. 11 – 26, 2011.
• [12] V. Prot, B. Skallerud, G. Sommer, and G. Holzapfel, “On modelling and analysis of healthy and pathological human mitral valves: two case studies,” J Mechanical Behaviour of Biomedical Materials, vol. 3, no. 2, pp. 167 – 177, 2010.