Banca de DEFESA: EVERTON BRITO DE LIMA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : EVERTON BRITO DE LIMA
DATE: 13/04/2023
TIME: 10:00
LOCAL: Defesa remota
TITLE:

Applications of the Finite Element Method in Acoustics

KEY WORDS:

Finite element method, acoustic radiation force and torque, super-resolution ultrasound.

PAGES: 82
BIG AREA: Ciências Exatas e da Terra
AREA: Física
SUMMARY:

This thesis concentrates the contributions of numerical studies, through the finite element method, which helped to obtain the results of studies covering two fundamental areas of acoustics, particle manipulation through the force and torque of acoustic radiation, and ultrasound imaging. In the first work, the numerical simulations performed validated the analytical demonstration of the transfer of acoustic spin from a first-order Bessel beam to a sub-wavelength spheroidal particle (prolate), where the proportionality relation of the induced torque and the spin, which in turn increases in accordance with the acoustic energy density. Subsequently, they corroborated the legitimation of a theory of non-linear interaction of any acoustic wave, with a spheroidal particle of sub-wavelength, exemplified by the study of the effects of torque and acoustic radiation force resulting from the non-linear interaction of the aforementioned particle and a beam sound composed of two crossed plane waves. In the following work, an extremely efficient semi-analytical method was proposed to obtain the mean fields of acoustic radiation force and torque exerted on any axisymmetric particle of subwavelength, in an ordinary acoustic field. In this work, we circumvent both the limitations of analytical methods, restricted to simplistic symmetry problems, and the limitations of purely numerical methods, which demand a lot of time and computational power to simulate the behavior of the particle along the acoustic field. Starting with imaging, the numerical simulations provided the elaboration of a super-resolution, low-cost and simple-to-execute ultrasonic image formation model, composed of a spherical polymer lens that focuses an acoustic wave generated by a flat circular transducer, this focusing exceeds the diffraction limit reaching a resolution of 0.6λ, thus surpassing the conventional resolution of λ. In addition to the numerical simulations, we present a theoretical description of the model, accompanied by an experimental execution. In the most recent imaging work, based on numerical simulations, we developed and characterized a super-resolution transducer, consisting of an additive manufacturing case, which has a flat circular piezoelectric actuator on its cylindrical base, and a core-shell lens (with steel core and polymer shell) of superfocusing on its conical top, thus achieving a super-resolution imaging method in a single device. Thus, we highlight how the numerical simulations corroborated not only with the theoretical sector but also with the experimental sector of these areas.

BANKING MEMBERS:
Externo(a) à Instituição - EDIGUER ENRIQUE FRANCO
Interno(a) - 2570322 - ASKERY ALEXANDRE CANABARRO BARBOSA DA SILVA
Externo(a) à Instituição - FREDERICO SALGUEIRO PASSOS - IFAL
Interno(a) - 1282899 - GLAUBER JOSE FERREIRA TOMAZ DA SILVA
Interno(a) - 3934870 - JOSE HENRIQUE ARAUJO LOPES DE ANDRADE
Interno(a) - 2356200 - JOSE PEREIRA LEAO NETO