Passive Wireless Strain Sensors Using Microfabricated Magnetoelastic Beam Elements

Abstract

This paper describes resonant wireless strain sensors fabricated from magnetoelastic alloys. The transduction mechanism is the E effect-the change in stiffness of magnetoelastic materials with applied strain or magnetic field. This is measured as a shift in the resonant frequency and is detected wirelessly using pick-up coils utilizing the magnetoelastic coupling of these materials. The sensors are fabricated from a 28-μm-thick foil of Metglas 2826 MB (Fe 40 Ni 38 Mo 4 B 18 ), a ferromagnetic magnetoelastic alloy, using microelectrodischarge machining. Two sensor types are described-single and differential. The single sensor has an active area of 7 × 2 mm 2 , excluding the anchors. At 23°C, it operates at a resonant frequency of 230.8 kHz and has a sensitivity of 13 × 10 3 ppm/mstrain; the dynamic range is 0.05-1.05 mstrain. The differential sensor includes a strain independent reference resonator of area 2 × 0.5 mm 2 in addition to a sensing element of area 2.5 × 0.5 mm 2 that is divided into two segments. The sensor resonance is at 266.4 kHz and reference resonance is at 492.75 kHz. The differential sensor provides a dynamic range for 0-1.85 mstrain with a sensitivity of 12.5 × 10 3 ppm/mstrain at 23°C. The reference resonator of the differential sensor is used to compensate for the temperature dependence of the Young's modulus of Metglas 2826 MB, which is experimentally estimated to be −524 ppm/°C. For an increment of 35°C, uncompensated sensors exhibit a resonant frequency shift of up to 42% of the dynamic range for the single sensor and 30% of the dynamic range of the differential sensor, underscoring the necessity of temperature compensation. The geometry of both types of sensors can be modified to accommodate a variety of sensitivity and dynamic range requirements.[2013-0330] IndexTerms-Strain measurement, magnetoelasticity, resonant sensing, Metglas, E effect.

Magnetic, Magnetoelastic and Corrosion Resistant Properties of (Fe–Ni)-Based Metallic Glasses for Structural Health Monitoring Applications

“…Metallic glasses fabricated in the form of ribbons can be introduced easily inside the engineering structure during the fabrication process. Due to their magnetic and magnetomechanical properties, these alloys will reflect any change in the structure of the hosting material through a change in the affected magnetic and/or magnetomechanical properties, therefore allowing monitoring and study of the structural system [2,3]. These materials are actually a promising alternative for the current SHM as they present several advantages besides their excellent magnetomechanical properties, for example high corrosion resistance, fabrication low cost, and quick remote detection possibility [4,5].…”

An Hourglass-Shaped Wireless and Passive Magnetoelastic Sensor with an Improved Frequency Sensitivity for Remote Strain Measurements

“…However, there was interference between neighboring magnetoelastic ribbons, and the method was only suitable for biological field detection. Venkatram Pepakayala changed the shape of the magnetoelastic material into a spring [23]. The frequency sensitivity of the sensor increased to 12.5 × 10 3 ppm/mstrain, which was much higher than before.…”

“…the frequency sensitivity comparison between the proposed HSMS and several other works. The values of the frequency sensitivity of one unit strain in studies[21,23,24] were 9.2 kHz, 17.6 kHz, and 28.6 kHz respectively. The frequency sensitivity of the propose HSMS was 37.1 kHz.…”

Wireless strain measurement with a micromachined magnetoelastic resonator using ringdown frequency locking

“…The sensors are fabricated from Metglas 2826MB (Fe 40 Ni 38 Mo 4 B 18 ), a magnetoelastic alloy (available from Metglas Inc., Conway, SC). The detailed operation of these types of strain sensors was described in [25]. …”

“…These sensors utilize the ΔE effect (i.e. change in Young’s modulus with applied strain) to transduce strain into change in sensor resonant frequency [25]. Real-time tracking of strain, as enabled by the use of the FLL, is useful in applications that present fast changing loading conditions.…”