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Analyzing Harmonic wave Propagation in Two Layered Elastic Anisotropic Prestressed Plate

Nosrati, Mohammad Amin | 2022

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 55946 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Fallah Rajabzadeh, Famida
  7. Abstract:
  8. Obtaining the mechanical properties of body tissues in a non-destructive manner is clinically important and has wide applications in the diagnosis and prevention of diseases. one of non-destructive methods is elastography, which requires proper modeling of the tissue and then analysis of the wave propagation in it and obtaining the propagation relations and the dispersion curves. Study of the literature revealed that many simplifications have been used in most modelings of arteries and so far the anisotropy of the artery and its layers with the effects of surrounding tissues and blood have not been studied Therefore, the aim of this study is to model the artery as a two-layer orthotropic sheet under pre-stress that has fluid on both sides. The two-layer plate represents the arterial tissue and the fluid on both sides of the plate indicates Blood and prevascular tissue. The assumption of modeling the tissue of the artery wall as a plate is due to the unification of the wave propagation response in the shell and the plate from a certain frequency. Also considering the surrounding tissues as fluid is due to observing the slight effect of considering these tissues on the dispersion curves. For this purpose, the wave propagation in the model is investigated using the three-dimensional theory of elasticity and the Theory of Superposing small deformations on large initial static deformations and the Holzapfel-Ogden model. The effect of fluid-solid interaction through the boundary conditions between them (equality of stresses and equality of displacement along the thickness of the artery) is considered. Then, using the governing equations and writing the boundary conditions, the dispersion equations are obtained and the dispersion curves are plotted. in order to be able to validate the results first, the equations and dispersion curves for the two models of an elastic and hyperelastic isotropic plate in the fluid that have been previously studied have been obtained. In the following, for the first time dispersion equations are obtained for two models of single-layer and double-layer orthotropic hyperelastic plate in the fluid. By comparing the dispersion curves, it is shown that the direction of wave propagation, the presence of fibers, its location, and in general the anisotropic properties of the plate, will strongly affect the propagation curves and any simplification in this area will cause errors
  9. Keywords:
  10. Wave Propagation ; Anisotropy ; Laminated Sheets ; Elastography ; Dispersion Curve ; Incompressible Material ; Orthotropic Plates

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