Stress Impedance Research Articles

Micromechanical Force Sensor Using the Stress-Impedance Effect of Soft Magnetic FeCuNbSiB.

By using the stress–impedance (SI) effect of a soft magnetic amorphous FeCuNbSiB alloy, a micromachined force sensor was fabricated and characterized. The alloy was used as a sputtered thin film of 500 nm thickness. To clarify the SI effect in the used material as a thin film, its magnetic and mechanical properties were first investigated. The stress dependence of the magnetic permeability was shown to be caused by the used transducer effect. The sputtered thin film also exhibited a large yield strength of 983 GPa. Even though the fabrication technology for the device is very simple, characterization revealed a gauge factor (GF) of 756, which is several times larger than that achieved with conventional transducer effects, such as the piezoresistive effect. The fabricated device shows great application potential as a tactile sensor.

FeSiB Tellerde Manyetoempedans ve Stresempedans Etki

In this study, the magnetoimpedance (MI) and stress impedance (SI) effect properties of Fe77.5Si7.5B15 wires have been investigated. Wires were annealed at 460 oC for different times. The largest change in the MI was observed at 1MHz ac current frequency value. At this frequency value, the change in MI was about 40% in the wire that as-received, while the change in the wire heat treated at 460 oC for 10 minutes was found to be 169%. It has been determined that low time annealed leads to increase in magnetic softness.

Magnetoimpedance and Stress-Impedance Effects in Amorphous CoFeSiB Ribbons at Elevated Temperatures.

The temperature dependencies of magnetoimpedance (MI) and stress impedance (SI) were analyzed both in the as-quenched soft magnetic Co68.5Fe4Si15B12.5 ribbons and after their heat treatment at 425 K for 8 h. It was found that MI shows weak changes under the influence of mechanical stresses in the temperature range of 295–325 K and SI does not exceed 10%. At higher temperatures, the MI changes significantly under the influence of mechanical stresses, and SI variations reach 30%. Changes in the magnetoelastic properties for the different temperatures were taken into consideration for the discussion of the observed MI and SI responses. The solutions for the problem of thermal stability of the magnetic sensors working on the principles of MI or SI were discussed taking into account the joint contributions of the temperature and the applied mechanical stresses.

Simple Device to Measure Pressure Using the Stress Impedance Effect of Amorphous Soft Magnetic Thin Film.

A simple micro-machined pressure sensor, based on the stress-impedance (SI) effect, was fabricated herein using typical micro-fabrication technologies. To sense pressure, a 1-µm thin, soft magnetic metallic film of FeSiB was sputtered and used as a diaphragm. Its electrical response (impedance change) was measured under pressure in a frequency band from 5 to 500 MHz. A lumped-element equivalent electric circuit was used to separate the impedance of the soft magnetic metal from other parasitic elements. The impedance change clearly depended on the applied pressure. It was also shown that the impedance change could be explained by a change in relative permeability, according to the theory of the SI effect. The radial stress in the diaphragm and the relative permeability exhibited a linear relationship. At a measurement frequency of 200 MHz, the largest sensor response, with a gauge factor of 385.7, was found. It was in the same order as the conventional sensors. As the proposed device is very simple, it has the potential for application as a cheap pressure sensor.

Strain Dependence of Hysteretic Giant Magnetoimpedance Effect in Co-Based Amorphous Ribbon.

The significant strain dependence of the hysteretic Giant Magnetoimpedance (GMI) effect in a Co67Fe3Cr3B12Si15 amorphous alloy in a low magnetizing field is presented. A simplistic test stand capable of continuous measurements of GMI characteristics under the influence of strain is detailed. Based on the results, a stress-impedance (SI) sensor is proposed, with a gauge factor similar to semiconductor strain gauges but more robust. An effective method of minimizing external magnetic field influence on the SI effect is given.

Comparison of Stress-Impedance Effect in Amorphous Ribbons with Positive and Negative Magnetostriction.

The SI (stress-impedance) effect in amorphous ribbons with varying magnetostriction was investigated. Iron- and cobalt-based ribbons with different magnetostriction coefficients were put under tensile stress in a dead weight tester and the impedance change was investigated in function of applied stresses. Significant differences of characteristics are presented. Stress-impedance analog of Villari reversal point was observed. The reversal point showed driving current frequency dependence, in which this point manifests for different stress values. Based on the obtained SI characteristics and magnetoelastic hysteresis, the most appropriate stress-sensing material was selected for development of precise small forces sensor.

Influence of Annealing Processes on Piezomagnetic Property in Fe73.5CulNb3Si13.5B9 Amorphous Alloy Strips

It is researched the influence rule on piezomagnetism property of Fe73.5CulNb3Si13.5B9 amorphous alloy with technology for heating processing. Result shows that the piezomagnetism property of Fe-based amorphous alloys appears favorable property at frequency of 1 KHz. Elevating the temperature of heating processing is in favor of promoting the piezomagnetism effect. In the condition of frequency at 1KHz, and continuous upload/offload stress applying process, the piezomagnetism property of Fe73.5CulNb3Si13.5B9 amorphous alloy is enhanced with increase of heating treatment temperature. When the temperature rise at 550 ℃, stress impedance (SI) effect value SI(%)=1.402 (relevant applying stress σ=0.612MPa). SI effect of Fe-based amorphous alloy is more sensitive under the stress of 0.2 MPa than above.

Stress Applied Patterns to the Influence of Stress Impedance Effect in Silicon/FeCuNbSiB Amorphous Powder Compound Film

We made use of compression-testing machine and LCR digital electric bridge to apply pressure stress and record the value of impedance which controlled by a computer throughout the whole testing process. Four stress loading methods were designed for testing, and a systematic research had been done with a scanning frequency at 1KHz for silicon/FeCuNbSiB amorphous powder compound films. It has been found that rubber matrix film is a kind of elastomer, which has some elastic deformation phenomenon such as elastic hysteresis and ratcheting. The radical reason of stress impedance (SI) effect is the internal relations between elastic deformation and impedance change. Deformation of elastic film will directly influenced the impedance, and the function of stress applied on the film will directly cause elastic deformation, thereby indirectly cause the change of impedance. Result shows, stress impedance effect is relevant to the recover process of elastic deformation. In the course of stress loading, the longer deformation recovered, the more indistinctively changed of impedance.

Force-sensitive properties of FeCuNbSiB powder/silicone rubber composite films

Composite films of different contents were prepared by Fe73.5Cu1Nb3Si13.5B9 powder as compound phase and silicone rubber as matrix phase. The thickness of film is 200 μm. Values of impedance, Z, under pressure stress were measured by TH2816LCR digital bridge. LYYL-500N high-grade-type microcomputer control pressure testing machine was used to conduct program control loading with a speed of 0.1 mm·min−1. The results show that composite films of different contents (25 vol%, 30 vol%, and 35 vol%) have excellent force-sensitive properties in both loading process and unloading process, especially when the stress is below 0.2 MPa, the stress–impedance (SI) and |k| values of composite films are much higher than that in the range of 0.2–1.0 MPa. The force-sensitive properties of loading process are superior to unloading process. While the frequency is 1 kHz, the force-sensitive properties of composite films are better than 50 kHz. The optimal temperature of powder heat treatment is 500 °C. Composite film which was prepared by this kind of powder has a good force-sensitive property.

Theoretical analysis of stress impedance effect of glass-coated amorphous ferromagnetic micro-wires

The stress impedance (SI) effect of glass-coated amorphous ferromagnetic micro-wires (GAFM) has great potential applications in the field of stress sensor, smart stealthy materials, etc. To explore the optimal manufacturing parameters of GAFM and the optimal experimental conditions for stress impedance effect, we set up a theoretical model to analyze the mechanism of SI effect and its relationship with various geometrical and magnetic parameters of the GAFM basing on the LLG and Maxwell equations. It is shown that the SI effect will get enhanced first, but decreased subsequently with the increase of external stress, magnetic field, radius, saturation magnetostriction and excitation frequency. Among all the affecting factors, the SI is sensitive to the changes of micro-wire radius mostly but insensitive to the saturation magnetization.

A high performance strain gage based on the stressimpedance effect in magnetic amorphous wires

The paper presents a study on the possibilities of using the Co based magnetic amorphous wires (MAWs) with nearly zero magnetostriction for measuring strains by exploiting the stressimpedance (SI) effect occurring on them. It is known that the SI is a particularization of the magnetoimpedance (MI) effect when a MAW is driven by an ac current and is subjected to mechanical stresses under constant magnetic field. Several parameters of influence have been investigated in order to obtain the best performances for a strain gage (SG) that is intended to be developed for finally building a high performance landslide transducer. Using a MAW of 20mm length which is driven by a current of 10mA and of frequency of 1MHz, under induced initial torsional stress of 5πrad/m and a residual axial tensile stress of 55MPa, we obtained a high sensitivity SG showing a gage constant of about 2100 and a linear range of ±200ppm.

Effect of tensile stress on magnetoimpedance properties of CoNiFe/Cu wire

A Co20.5Ni40.5Fe39 magnetic film was electrodeposited onto a copper wire 50 µm in diameter. The magnetoimpedance (MI) effect, (ΔZ/Z)H(%) = ((Z(H) − Zmax)/Zmax) × 100, was measured in the Co20.5Ni40.5Fe39/Cu composite wire under varying tensile stresses up to 30 MPa. The results showed that large MI and stress impedance (SI) effects can be observed in the Co20.5Ni40.5Fe39/Cu composite wire. The MI curve at zero tensile stress shows a small split peak in the low-field region. With increasing applied tensile stress, single-peak behaviour of the MI effect is observed. The magnitude of the MI and SI effects decreases with increasing tensile stress, σ. The peak values of (ΔZ/Z)H(%) for the sample decrease from 265% at σ = 0 to 39% at σ = 30 MPa at 40 kHz ac driving-current frequency. The impedance of a sample under the effect of 25 MPa tensile stress at 40 kHz ac driving-current frequency showed variations of about 146%. It was also found that the frequency value, f*, where the maximum MI effect was observed as a function of driving-current frequency, increases with increasing tensile stress.

Stress impedance effects in flexible amorphous FeCoSiB magnetoelastic films

Amorphous FeCoSiB films were deposited on the flexible polyimide substrates (Kapton type (VN)) by DC magnetron sputtering. Stress impedance (SI) effects of the flexible amorphous FeCoSiB magnetoelastic films were investigated in details. The results show that a large stress impedance effect can be observed in the flexible amorphous FeCoSiB magnetoelastic films. And the results also show a bias magnetic field plays an important role in the stress impedance of FeCoSiB films. Applied a bias magnetic field during depositing can induce obvious in-plane anisotropy in the FeCoSiB films, and a larger SI effect can be obtained with a stronger anisotropy in FeCoSiB films. Argon pressure has a significant effect on the SI effect of the FeCoSiB films. The SI of the FeCoSiB films reaches a maximum of 7.6% at argon pressure of 1.5 Pa, which can be explained by the change of residual stress in FeCoSiB films.

Influence of stress on magneto-impedance in Co71−xFexCr7Si8B14 (x=0, 2) amorphous ribbons

Systematic measurements of stress-impedance (SI) have been carried out using Co-rich amorphous ribbons of nominal composition Co 71− x Fe x Cr 7 Si 8 B 14 ( x = 0, 2) at various excitation frequencies and bias fields and at room temperature. The impedance, Z ( σ ) for both the samples was found to be very sensitive functions of applied tensile stresses (up to 100 MPa) exhibiting a maximum SI ratio as much as 80% at low frequency ∼0.1 MHz. The nature of variation of SI changes with the excitation frequency especially at higher frequencies in MHz region where it exhibits a peak. Magnetization measurements were also performed to observe the effects of applied stresses and magnetization decreased with the application of stress confirming the negative magnetostriction coefficient of both the samples. Both the samples exhibited negative magneto-impedance (MI) when the variation of Z is observed with the applied bias magnetic field, H . The impedance as functions of applied magnetic field, Z ( H ), decreases with the application of stress thus making the MI curves broader. Maximum MI ratio as large as 99% has been observed for both the samples at low fields ∼27 Oe.

Stress-impedance effects in sandwiched FeCuNbCrSiB/Cu/FeCuNbCrSiB films fabricated by Microelectromechanical Systems technique

Sandwiched FeCuNbCrSiB/Cu/FeCuNbCrSiB films with a serpentine structure have been realized on silicon cantilever by Microelectromechanical Systems technique, and the stress-impedance (SI) effects have been studied in the frequency range of 1–40 MHz. Experimental results show that the values of SI ratio increase with the deflection and a large SI ratio of −24.1% at 5 MHz with the average tension stress 69.9 MPa and strain 0.048% is obtained in the sandwiched FeCuNbCrSiB/Cu/FeCuNbCrSiB films, which shows attractive for the applications of strain sensors.

Induced Magnetic Anisotropy and Stress-Impedance Effect in Nanocrystalline$hboxFe_73.5hboxCu_1hboxNb_3hboxSi_13.5hboxB_9$Ribbons

The influence of direction and strength of induced magnetic anisotropy on stress-impedance (SI) effect was experimentally and theoretically studied in this paper. Experimentally, it was found that the magnetic anisotropy of the stress Joule heated Fe73.5Cu 1Nb3Si13.5B9 nanocrystalline ribbons were determined by direction and strength of the induced anisotropy. Theoretical calculations of the direction and strength of the induced magnetic anisotropy suggest that transverse anisotropy and small anisotropic field result in an increase of the SI effect. To decrease the anisotropic field and increase the transverse anisotropy simultaneously, a complex annealing process was applied to Fe73.5 Cu1Nb3Si13.5B9 ribbons, and it was found that the SI effect was drastically improved. A maximum change of 286% in the SI ratio of the complex annealed nanocrystalline Fe73.5Cu1Nb3Si13.5 B9 ribbon was observed around 10 MHz frequencies

Stress-impedance effects in sandwiched FeCuNbCrSiB/Cu/FeCuNbCrSiB films

Sandwiched FeCuNbCrSiB/Cu/FeCuNbCrSiB films with a meander structure have been realized on silicon cantilever by Microelectromechanical Systems (MEMS), and the stress-impedance (SI) effects have been studied in the frequency range of 1–40 MHz. Experimental results show that the values of SI ratio increase with the deflection, and a large SI ratio of − 24.5% at 5 MHz with the deflection of 2 mm is obtained in the sandwiched FeCuNbCrSiB/Cu/FeCuNbCrSiB films, and the strain gauge factor is 1255 at 5 MHz, and is larger than the conventional metal strain gauge and semiconductor strain gauge, which is attractive for the applications of strain sensors.

Stress-impedance effects in multilayered FeSiB/Cu/FeSiB films

Multilayered FeSiB/Cu/FeSiB films with a meander structure were fabricated by magnetron sputtering on thin glass substrate, and the stress-impedance (SI) effects in the multilayered FeSiB/Cu/FeSiB films were studied in the frequency range of 1–40 MHz for different film thicknesses of FeSiB film and Cu layer. Experimental results showed that the values of SI ratio increased with the deflection of the layered FeSiB/Cu/FeSiB films at high frequencies, and a large negative SI ratio of − 17.3% for a frequency of 5 MHz at the deflection of 1 mm was obtained in the multilayered FeSiB/Cu/FeSiB films with a thicker FeSiB film, which was very attractive for the applications of stress sensors.

Stress-impedance effects in layered FeSiB/Cu/FeSiB films with a meander line structure

Stress-impedance (SI) effects were realized in layered FeSiB/Cu/FeSiB films with a meander line structure by magnetron sputtering on thin glass substrate. The SI effects were studied in the frequency range of 1–40 MHz for the layered FeSiB/Cu/FeSiB films with different film thickness of FeSiB film and Cu layer. Experimental results show that the values of SI ratio increase nearly linear with the deflection of the layered FeSiB/Cu/FeSiB films at high frequencies, and a large negative SI ratio of - 18.3 % at a frequency of 25 MHz with the deflection of 1000 μ m is obtained in the layered FeSiB/Cu/FeSiB films with a thicker FeSiB film, which is very attractive for the applications of stress sensors.

Giant stress-impedance effect in Fe 71Cr 7Si 9B 13 amorphous wires

The giant stress-impedance (SI) effect in as-received and furnace annealed Fe 71Cr 7Si 9B 13 amorphous wires is studied. Samples were annealed at temperature of 460 °C for times between 0.3 and 300 min to remove internal stresses. The results show that the magnetoimpedance and SI effect change sharply with annealing and a maximum stress-impedance ratio of 255% is observed in the wire annealed for 10 min under an applied tensile stress of 250 MPa.