Navegando por Assunto "Ultrasound"

Agora exibindo 1 - 4 de 4

Acesso aberto (Open Access)
Análise do estado plano de tensões em chapas de aço ASTM A131 por métodos ultrassônicos
(Universidade Federal do Pará, 2023-08-17) ALBUQUERQUE, Lucas Gabriel de Sousa; MACHADO, Paulo Cordeiro; http://lattes.cnpq.br/0133330144786049; https://orcid.org/0000-0003-4375-6812
Residual stresses affect the mechanical component in the same way that external stresses do. These stresses usually arise in the manufacturing process. By knowing the residual stresses, mainly the tensile stresses, present in a component or those that may be generated by some manufacturing process, it is possible to take actions to avoid or minimize their effects, thus extending the component's useful life. Thus, residual stress will always be a demand to be studied, both by academia and by the metal-mechanic industry. Therefore, the objective of this work was to determine the plane state of residual stresses in ASTM A131 steel plates by combined shear and compressive ultrasonic wave methods. A TIG welding torch was used to induce residual stresses in the plates by the high thermal gradient. The specimens were xed by supports to avoid deformation, thus preserving the residual stresses. Three different methods were applied, named, in this paper, as: Hirao I; Clark; and Hirao II. The major difference between them is related to the preferred direction of wave propagation. Stresses in different directions from the anisotropy axis can change this direction. Consequently, the angle between the anisotropy and the preferential direction of propagation of the ultrasonic wave (φ) is changed. To measure the propagation time of the ultrasonic waves, a software was developed for the acquisition of the ultrasonic response signals and another one for the data processing.To end the preferential angle of wave propagation, a support was made by 3D printing, which allowed the transducer to be moved using a stepper motor. In all three methods, very high tensile stresses were observed near the melt zone, which decreased rapidly as the distance from this region increased. In addition, the values of φ were lower in the center line than in the lateral lines, indicating variation in residual stress levels as function of distance from the constraints.
Acesso aberto (Open Access)
Análise teórico-experimental da biotransferência de calor em tecidos sintéticos aquecidos por ultrassom
(Universidade Federal do Pará, 2016-04-14) AMORIM, Nelson de Souza; COTTA, Renato Machado; QUARESMA, João Nazareno Nonato; http://lattes.cnpq.br/7826389991864785
The inverse problem of parameter estimation for the bioheat transfer problem in sintetic tissue was analyzed. Initially an experimental analysis was developed by heating a synthetic tissue using a ultrasound transducer. Different temperature profiles were obtained for 3 cases involving intensity variations: 1W/cm2, 1.5W/cm2 and 2W/cm2 for 3 thermocouples positioned along the sintetic tissue. A mathematical model was develeped to represent the experimental problem. The solution of this model was obtained using the Classical Integral Transform Technique (CITT). The Levenberg-Marquardt Method was used to solve the parameter estimation for the attenuation of sintetic tissue. A comparison between experimental solution and the mathematical model was performed.
Acesso aberto (Open Access)
Extração utilizando óleo vegetal e assistida por ultrassom de biocompostos da pimenta cumari-do-pará (capsicum chinense Jacq) em diferentes estádios de maturação e localidades
(Universidade Federal do Pará, 2017-03-23) CARDOSO, Raiane Vieira; RODRIGUES, Antonio Manoel da Cruz
The extraction of blend is one of the most critical steps in the polls with natural products, because your efficiency depends on several parameters, such as the sample type, type of analytes to be extracted, location where these analytes are sampled, type of solvent extractor and method of extraction, among others. In this study the objective of performing the ultrasound-assisted extraction of cumari pepper blend-do-pará (Capsicum chinense Jacq) grown in two different locations in the State of Pará (Santo Antônio do Tauá and Igarapé-Açu) and with different level of maturation using vegetable oil as a solvent. The centesimal composition (moisture, ash, proteins, carbohydrates and lipids), was made in conjunction with the quantification of soluble solids, acidity, pH and color. For conducting the tests of extraction of bio- and antioxidant capacity, the pulps were freeze dried and subjected to extraction with organic solvents and ultrasound-assisted extraction using vegetable oils (soybean, Brazil nuts and palm olein). In the extracts were analyzed concentrations of vitamin C, total carotenoids and phenolic compound capsaicin. The antioxidant activity was measured by β-carotene system/linoleic acid and ABTS radical test. The results indicated that the ash content is not influenced by the degree of maturation at both locations studied. About the color, the biggest b * parameters, index Chroma (C) and the Hue Angle values (ºc) near 90° were found in Peppers mature, demonstrating that these fruits boast yellow colour when they reach maturity. For bioactive compounds and antioxidant activity, it was observed that for the majority of the compounds analyzed the degree of ripeness and the location interfere and highest values were found for the mature peppers of Igarapé açu. The same behavior was observed for extracts obtained from vegetable oils, being soybean oil which obtained greater values. The fruits of peppers had significant antioxidant activity and the Pearson correlation results have shown that phenolic compounds were the main responsible for antioxidant activity.
Acesso aberto (Open Access)
Uso de métodos não convencionais visando a obtenção de extratos naturais enriquecidos de biomoléculas a partir de rejeitos vegetais descartados em feiras livres
(Universidade Federal do Pará, 2018-03-16) MELO, Giselle Cristine da Silva; RODRIGUES, Antonio Manoel da Cruz; http://lattes.cnpq.br/7524720020580309