R.M. Pidaparti, P.A. Sarma, and R.A. Meiss (USA)
Smooth muscle tissue, Composite, Non-linear, StressStrain, Simulation, Experiments
Smooth muscle tissue is a complex structure, which lines the hollow internal organs, and exhibit non-linear, viscoelastic, anisotropic, time dependent properties. This paper describes the two material models (anisotropic and non-linear) that are developed to predict the stress-strain behavior of the tissue. Three-dimensional finite element simulations were carried out to estimate the anisotropy ratio through the percentage change in area based on the experimental data. Also, a hyperelastic material model is developed to simulate the shortening-dependent stiffness of tracheal smooth muscle tissue through a threedimensional non-linear finite element analysis. The results obtained from both the models are in good agreement with the experimental data. properties of the smooth muscle tissue without mechanical constraints on its function, an indirect method is used in this study to obtain both the longitudinal and radial mechanical properties. In addition, a hyperelastic material model is developed to represent the non-linear behavior of the smooth muscle tissue. The results of material models are compared to the experimental data. 2. MATERIALS AND METHODS Composite Material Model: The composite properties of a contracting smooth muscle tissue are estimated from a computational model based on the experimental data of length dependent stiffness. The area changes are obtained at different muscle lengths from experiments in which stimulated muscle undergoes unrestricted shortening. First we obtain the deformed shape of the muscle from the 3-D finite element analysis and then the percentage change in area is calculated based on original undeformed cross sectional area. Then vary the material properties until the area changes from the finite element analysis are matched to those derived from experiments. Hyperelastic Material Model: The non-linear properties of a contracting smooth muscle tissue are represented through a hyperelastic material model based on the experimental data of length dependent stiffness for computational simulations. Hyperelastic material models are described in terms of strain energy potential and are available in most general-purpose finite element software, like ABAQUS or ANSYS. Finite Element Analysis: In this study, commercially available finite element software, ANSYS is used. For composite material properties prediction, smooth muscle strip is modeled as 3D solid in the form of a hollow cylinder with inner radii 0.175mm, outer radii of 0.25 mm, and 6mm in length. Symmetric boundary conditions on the parallel sides were used in the model. The finite element model consists of 1280 SOLID-95 elements and 6593 nodes. The material properties for the smooth muscle tissue were assumed to be composite in nature.
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