Método para detecção de tensão mecânica e sistema para detecção de tensão mecânica em tubos dispostos em ambientes aquáticos

Fundação Universidade de Caxias do SulUniversidade Federal do Rio Grande do SulEngenhariaDepositad

Model for wireless magnetoelastic strain sensors

This paper describes a magnetoelastic strain sensor based on the ∆E effect and discusses some materials used in its construction. A polycrystalline Fe–Al–B alloy with good quality magnetoelastic properties was used as the transducer and glued to the test object, either brass plates or rods of SAE 1010 steel. The strain-dependent magnetic field of the transducer changes the operating point of the resonator, a strip of field-annealed Metglas 2826MB3, resulting in a modification of its resonant frequency. A model was developed to simulate the strain-dependent magnetic field acting on the resonator and thus to calculate curves of resonant frequency vs. deformation. With the help of this model, differences in the shape of the frequency vs. strain curve can be understood. For a sensor with resonant frequency of 60.5 kHz glued to a rod of SAE 1010 steel, a total resonant frequency variation ∆f ~7 kHz was observed for a deformation of 1100 ppm. The geometry of this sensor is especially favorable for the remote monitoring of a steel surface, such as the wires of the tensile armor of a marine riser

Monitoring the electrochemical behavior of hybrid coatings on magneto-elastic sensors using resonant frequency variations

In this work we present results for the protective performance of coatings used on magneto-elastic ribbons. It is found that monitoring the resonance frequency variation (Δf) of a magneto-elastic sensor can give useful electrochemical information. This method has the advantage of allowing one to monitor the electrochemical behavior of coatings without the need for direct access to the sample. A sensor developed from the FeNiMoB alloy (Metglas 2826MB3) was covered with hybrid coatings based on silicon alkoxide precursors. The results obtained from the magneto-elastic sensor test were correlated with the results obtained from electrochemical impedance spectroscopy (EIS). In general, it was observed that the Δf monitoring technique provided results consistent with those obtained by EIS, with the advantage that it does not need to have direct contact with the sample. Besides that monitoring the resonance frequency also allows one to evaluate the electrochemical behavior of the coating in the medium of interest

Método para detecção de tensão mecânica e sistema para detecção de tensão mecânica em tubos dispostos em ambientes aquáticos

Fundação Universidade de Caxias do SulUniversidade Federal do Rio Grande do SulEngenhariaDepositad

Reference material for magnetic measurements in epstein frame

2 p. : il.The development of a reference material for magnetic measurements in an Epstein frame will enable Brazilian companies to obtain reliable, yet inexpensive calibrations of their equipment. By means of periodic measurements according to the standard NBR 5161, it will be possible verify the stability of the calibrations and the rated operating conditions from the behavior of the reproducibility graph and an interlaboratory comparison

Interlaboratorial de ensaios magnéticos em aços elétricos

5 f. : il.Apresentamos os resultados de um Interlaboratorial de Medidas Magnéticas em Aços Elétricos, onde participaram várias empresas e laboratórios brasileiros. Os ensaios de perdas magnéticas foram realizados em chapas de aço elétrico GNO (grão não orientado) utilizando quadro de Epstein, seguindo a norma NBR 5161. Embora a grande maioria das empresas consiga medir perdas com relativa precisão, alguns desvios sérios foram notados

RFID wireless system for detection of water in the annulus of a flexible pipe

Corrosive environments are responsible for the highest degree of degradation and failure in marine structures. The presence of sea water in marine structures such as flexible pipes can cause a significant reduction in their operational life, especially when associated with permeated gases, which could lead to corrosion related failure mechanisms such as corrosion-fatigue and hydrogen cracking. The ingress of sea water into flexible pipes can occur either due to ruptures in their external polymeric sheath or to permeation of condensed water from the pipe bore. This event since flooding of the so-called annular space of flexible pipes is the trigger for all knows corrosion assisted failure modes, it is clear that a system that is able to reliably detect the presence of water in the structure is highly desirable. This work will describe a radio frequency identification (RFID) system designed for this purpose; it relies on the measurement of shifts in the resonance frequency of specially-designed tags which would be inserted within the layers of the flexible pipe during manufacturing. This paper shows the design and validation process of these tags and also of a reader which is meant to be scanned along the outside surface of the pipe by a remotely-operated vehicle (ROV). The study was performed through a finite element analysis and a test in which the tags were inserted within a full-scale mock-up of a flexible riser, which was then flooded with synthetic seawater. Results show that the shift in response due to sea water is clearly identifiable and distinguishable from other effects

Aços elétricos semiprocessados para motores elétricos

5 p. : il.Semi-processed electrical steel sheets are submitted, after stamping, to a “stress relief annealing”, that also decarburizes, increases grain size and provides an insulating oxide layer between the sheets. Efficient motors should have: i) low copper losses in the windings (function of magnetic permeability), ii) low iron losses in the core (function of chemical composition, thickness, grain size and texture)

Revestimento híbrido a base de precursores silanos aplicado sobre uma liga magnetoelástica utilizada como plataforma para biossensores de carregamento de massa

Fundação Universidade de Caxias do SulUniversidade Federal do Rio Grande do SulEngenhariaDepositad

Efeito do Zr na microestrutura de ímãs nanocristalinos Sm (CoFeCuZr)z¹

10 f. : il.Imãs do tipo Sm2(MT)17, onde MT=Metal de Transição, apresentam microestrutura nanocristalina composta de células da fase Sm2(Fe,Co)17 (2:17) circundadas pela fase Sm(Co,Cu)5 (1:5). O objetivo principal é determinar como o Zr altera a microestrutura ou se o Zr provoca o aparecimento de outras fases na microestrutura. Amostras de composição química Sm (CobalFe0,2Cu0,1Zrx)8 (bal=balanço) com x= 0,02 , 0,04, 0,06 e 0,08 foram preparadas em forno a arco com base de cobre refrigerada a água. As amostras foram, subseqüentemente, submetidas a um tratamento térmico compreendendo 3 h a 1175oC, 4 h a 820oC, resfriamento lento (1oC/min.) até 400oC e mais 3h a 400oC. Os ímãs foram magneticamente caracterizados em bobina supercondutora. Os resultados indicam que o Zr promove em alta temperatura a existência de uma única fase Sm:MT, a qual é intermediaria entre 2:17 e 1:5, provavelmente 1:7. A existência de um campo monofásico em alta temperatura é essencial para a formação da microestrutura nanocristalina. Nas amostras com maior teor de Zr, x= 0,04, 0,06 e 0,08, observa-se que o Zr provoca a formação de diversas outras fases, entre as quais uma com ~16-17%at de Zr e pobre em Sm e em Cu. Esta outra fase com ~16-17%at de Zr pode ser o Zr2Co11 mencionado como fase estável no diagrama Zr-Co, mas ocorrendo aqui com substituição parcial de Co pelo Fe