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Structural intensity assessment & material identification of a human tympanic membrane

Boek - Dissertatie

The middle ear system functions as an acoustic impedance transformer, from which energy is transmitted from the air medium to the fluid present in the inner ear. The first transmission of mechanical energy is located between the eardrum and the first of the ossicles. Moreover, it was assumed that most of the energy is efficiently transmitted from the eardrum’s tissues to their attachment to the malleus. No more specific information could be found in literature and it was the aim of this Ph.D. research to quantify the energy flow on human eardrums. The starting point of this work was based on a well-known technique called the energy flow analysis and it is based on a combination of measured deformations and the stiffness of a sample. These studies were mainly focused on analyzing plate-like structures in the past, which are by no means comparable to the complex morphology of eardrums. Furthermore, the stiffness of individual eardrums may also vary considerably. Therefore, the Ph.D. candidate had 2 challenges to face: expand the current energy flow analysis suited for simple geometries, in order to estimate results from complex ones & develop a method, from which stiffnesses could be identified via measurements of individual eardrums. The first issue was addressed by developing a method that discretizes the continuous & irregular surface of the eardrum to a collection of individual elements. This choice has shown itself to be efficient and it could provide precise energy transmission data via measurements of an irregular sample’s deformation. Later, the second challenge was overcome by refining the so-called the Virtual Fields Method. The adapted algorithm was validated with synthetic data and the errors of the retrieved stiffnesses were below 3%. Since the stiffness and the energy flow assessments were completed for irregular geometries, it was decided to use the algorithms for the case of an eardrum. Thankfully, after recording some experimental data of the refereed membrane, reasonable stiffness values were estimated and were within the range of what researchers published in the past. By combining the stiffness with the displacement fields of a single eardrum, the energy flow could be finally visualized and the results were in accordance with our expectations. Due to this achievement, not just the main aim of this research was completed, but 2 well-established engineering techniques were refined, so they could be applied on more complex geometries.
Aantal pagina's: 165
Jaar van publicatie:2020
Trefwoorden:Doctoral thesis
Toegankelijkheid:Open