Desenvolvimento e caracterização de um sensor magnetoelástico de deformação

Abstract

Amorphous metals have been shown to have magnetomechanical properties which are superior to those of any other magnetic materials. This has allowed their usage in a growing number of sensing purposes. The capacity of remotely interrogating the resonant frequency of amorphous material stripes trough magnetic fields allows their application as sensor in situations that do now allow direct contact with the measurement surface. This quality may be useful for the monitoring of risers that bring petrol from deep sea to platforms on the surface. The resonant frequency of the stripes is a function of, alongside other properties, the intensity of the magnetic field in which they are inserted. Thus, a substrate’s deformation may be monitored trough the use of a transducer in him affixed, which magnetizes as the substrate deforms, consequently altering the magnetic field imposed over the resonator, and its resonant frequency. In this work, the construction of a magnetoelastic strain sensor is investigated, where a polycrystalline FeAlB alloy was used as transducer, and amorphous materials, by the commercial name of Metglas 2826 MB3 and 1K501, were used as resonators. The Fe80Al20 alloy, with 2%at. B, was shown to have an 80 ppm magnetostriction, which inspired its use as transducer, which enabled the substitution of the amorphous ribbons previously used. A testing bench, capable of applying mechanical stress to a brass substrate, was built with the goal of teste the sensibility of the magnetoelastic sensor to strain. A highly linear behavior of the sensor’s resonant frequency to the applied stress on the brass substrate was observed, with Gauge Factors of 120 for the sensors that used Metglas 2826 MB3 and 1K501 as resonators, respectively. This result instigated the exploration of the magnetoelastic sensor’s applicability on ferromagnetic surfaces. Finally, mechanical stress tests were conducted, in which the deformation of the SAE 1010 steel substrate were simultaneously monitored by the magnetoelastic sensor, and a Strain Gauge. The resonant frequency of the sensor is this test showed a sigmoidal form, with a nearly linear region. The monitoring of a riser with this device is feasible