Avaliação de propriedades acustoelásticas do polímero termoplástico polimetilmetacrilato por ultrassom
Nenhuma Miniatura disponível
Data
2017-11-17
Autores
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Federal de Goiás
Resumo
Ultrasound is a powerful tool used in modern medical and industrial applications. The
portability, applicability and ease of working with ultrasound, together with the fact
that it is a non-destructive technique and of lower costs, contribute to its use. Modernly,
thermoplastic polymer polymethylmethacrylate (acrylic) or PMMA has been used for
a variety of applications, from transparent aerospace components to medical-hospital
equipment. The study of PMMA’s acustoelasticity using ultrasonic methods allows the
indirect inspection of certain physical characteristics of this material. It is known that
acoustic waves are a ected by the characteristics of the medium, such as temperature,
texture and tension. The research was divided into three stages, the first one to analyze
the influence of temperature on the velocity of critically refracted longitudinal ultrasonic
waves (Lcr) in PMMA. For this, the transmission method was used for three di erent
frequencies. In the second, the structural anisotropy was evaluated using the acoustic
birefringence using the pulse-echo method. At this stage a rectangular sample was
fractured transversely and rejoined to simulate a symmetry break. The third and final
step was devoted to characterizing the acoustoelastic constants L22, L21 and L23 of
homogeneous samples by means of longitudinal and shear waves in the pulse-echo
mode and the application of an uniaxial force. The results with the waves Lcr showed a
significant influence of the temperature on the propagation velocity of the ultrasonic
waves, another factor of influence was the frequency of the transducers. On the other
hand, with acoustic birefringence it was possible to identify a great variation of this
magnitude near the fractured zone, that is, of greater anisotropy. The acoustoelastic
constants L22, L21 and L23 were characterized and an increase in the propagation time of
the ultrasound wave as a function of the strain was observed for the constants L22 and
L23. The constant L21 decreased the propagation time of the ultrasonic shear wave as a
function of the deformation. The ultrasonic techniques employed were relevant and
allowed to obtain new results not yet described in the literature. The characterization
of the acoustoelastic constants also made it possible to estimate the third order elastic
constants (l, m, n and A, B, C). The constants characterized in this research are important
to obtain a complete understanding of the elastic properties of polymethylmethacrylate.
Descrição
Citação
REZENDE, Ana Cláudia Barbosa. Avaliação de propriedades acustoelásticas do polímero termoplástico polimetilmetacrilato por ultrassom. 2017. 108 f. Dissertação (Mestrado em Engenharia Elétrica e da Computação) - Universidade Federal de Goiás, Goiânia, 2017.