Changes In Magnetic Permeability Research Articles

In-situ microstructure monitoring during tempering of quenched AISI4340 steels using a high temperature electromagnetic sensor

AISI 4340 steels are used in applications where high strength and toughness are required, for example, in power transmission gears and shafts, aircraft landing gear and other structural components. The required mechanical properties are achieved by hot rolling and quenching and tempering (Q&T) heat treatment. For optimum process efficiency and quality control, it is desirable to monitor the microstructural development during tempering in situ, as the microstructure is directly linked to the mechanical properties. Electromagnetic (EM) sensors have been shown to be sensitive to steel microstructural changes due to the associated changes in magnetic and electrical properties. This study reports on using a high-temperature laboratory EM sensor that operates inside a furnace to assess microstructural changes that occur during tempering at 250°C for AISI4340 steel samples. The sensor operates at low magnetic field and low frequency where the signal is affected by changes in magnetic permeability due to microstructural changes. The microstructure and hardness have been characterised to correlate to the measured EM sensor signal. The results have shown that the EM sensor signal is affected by temperature and microstructural changes on the slow heating to the tempering temperature and then is sensitive to the continuing microstructure changes that occur during the isothermal hold. The results show the potential for in-situ EM sensor monitoring during heat treatment.

A model to account for magnetic permeability changes resulting from edge damage caused by laser cutting in a high performance cobalt-iron alloy

Laser cutting is the mainstay of electrical machine stator core manufacture for prototyping and for high value, small and medium batch sizes. However, it can introduce localized damage into electrical steels, with reduction in magnetic permeability and increase in core loss in regions adjacent to the edge. These phenomena have been studied in Silicon-iron alloys, but there is little published data on Cobalt-iron. This paper presents experimental measurements on magnetic edge damage effect in Cobalt-iron alloys due to laser cutting. The paper then uses magnetic measurements for an increasing number of cuts in test samples to develop a model that represents the deterioration of magnetic permeability with distance from the cut edge, including cumulative damage effects from multiple cuts. The model is suitable for incorporation into finite-element models, either as a continuous function of position or to generate individual magnetization curves for discrete layers in finite-element mesh. The paper concludes by using the model to generate a series of magnetization curves which include the damage effect and in turn uses these to predict the net magnetic behavior of a series of rectangular strips. Good agreement is obtained between these predictions and measurements of samples from the same batch of Cobalt-iron.

Analysis of PEC technique and external magnetic fields for detection of corrosion under insulation: 3D finite element model

Metal piping in industrial plants is subject to corrosion under insulation, which reduces the wall thickness and limits service life and operating conditions. The Pulsed Eddy Current (PEC) technique can be effective in the inspection of isolated metallic materials. However, changes in magnetic permeability make its use difficult in ferromagnetic steels. In this work, we used Neodymium magnets to magnetize the material during tests with a probe. We developed a 3D finite element model to reproduce the magnetic field of the PEC probe and identify defects under insulation. Theoretical results satisfactorily matched the experimental results.

A Novel Magnetoelastic Biosensor With Flexible TbDyFe Film as Sensing Materials for Osteoarthritis Marker MMP-3 Detection

A new design of flexible magnetoelastic (ME) biosensor based on TbDyFe/polystyrene-poly (ethylene-butylene)-polystyrene block copolymer (SEBS) film for the osteoarthritis (OA) marker matrix metalloproteinase 3 (MMP-3) detection is presented. This article studied a novel flexible ME film to replace the traditional rigid substrate for biosensors. The magnetostrictive material of TbDyFe was mixed homogeneously with paraffin solution to fabricate TbDyFe fluid, which was reacted at high temperature with SEBS in a certain ratio to prepare the film. TbDyFe/SEBS films were used as substrates for the immobilization of MMP-3 antibodies. Specific binding of antibodies to MMP-3 antigens generated compressive stress on the substrate surface, which in turn led to changes in magnetic permeability and impedance. To improve the sensitivity of the biosensor, the TbDyFe doping concentration was optimized and the magnetic response performance of the TbDyFe/SEBS composite film was measured. The results show that this assay is capable of detecting concentrations of MMP-3 between 0.76 and 10000 ng <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\cdot $ </tex-math></inline-formula> mL−1 with a detection limit of 0.76 ng <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\cdot $ </tex-math></inline-formula> mL−1, covering the range of clinical tests required for the diagnosis of OA. This novel flexible ME biosensor provides a viable method for the diagnosis and monitoring of OA.

A Thickness Reduction Detection Method Based on Magnetic Permeability Perturbation Under DC Magnetization for Ferromagnetic Components

The assessment of internal thickness reduction of ferromagnetic components has always been a critical issue in engineering. However, traditional nondestructive testing (NDT) methods have some limitations with the increase of wall thickness. Based on the nonlinear magnetization characteristics of ferromagnetic materials, a relationship between the thickness reduction and active excitation of changes in magnetic permeability is established, and a new thickness reduction detection method based on magnetic permeability perturbation (MPP) is proposed. The mechanism of thickness reduction detection based on MPP is analyzed by a theoretical model and the feasibility is verified through a series of simulations and experiments. Experimental results show that the measurement results have good linearity, and a thinning loss of 6.25% of wall thickness can be well detected. Additionally, the effects of magnetizing current and excitation frequency on the amplitude and linearity of the detection signal are discussed in detail. This method does not benefit from the lift-off effect, nor is it limited by the skin effect, which has great practical value as a supplement to the evaluation of thickness reduction for ferromagnetic components.

On the influence of cyclic loadings on the magnetic permeability of ferritic-pearlitic AISI 1045 steel

In this paper, the changes in magnetic permeability of ferritic-pearlitic AISI 1045 steel during cyclic loading were investigated using a Micromagnetic Multiparameter Microstructure and stress Analysis (3MA) sensor. For this, in-situ and ex-situ magnetic measurements were carried out at cyclically loaded specimens at different cycle numbers in the high cycle fatigue regime. The magneto-mechanical interaction measured during tensile and compressive stresses showed a nonlinear behavior of the magnetic permeability with respect to mechanical stress. Moreover, values extracted from 3MA measurements were plotted against the cycle number and cycle number to failure to indicate the fatigue-induced evolution of magnetic permeability and estimate fatigue life, respectively. The obtained magnetic measurements were correlated with the temperature and electrical resistance change of material during fatigue as well as the surface hardness of the specimens after failure.

Damage detection via embedded sensory particles – Effect of particle/matrix interphase properties

Supported by recent studies, a crack interior to the host material will cause an especially strong stress concentration and thus can be detected by monitoring or sensing the localized changes in the magnetic properties of the particles in metallic composites. Using finite element analysis calibrated from the experiments, this work investigates the effects of material properties and thickness of the particle/matrix interphase on the phase transformation response of embedded sensory particles in the vicinity of a crack existing in the host matrix. Depending on the interphase elastic and cohesive properties, its thickness, and the operational temperature, which is known to delay or promote martensitic transformation, it is found that interphase damage may occur at stress levels lower than that needed to initiate phase transformation in MSMA particles. Such a response would mitigate the degree to which the particle transforms and reduces particle sensitivity. The effect of particle position relative to the crack tip on interphase damage and particle transformation response is studied via the full factorial design of experiments. To assess the true feasibility of the technique, the average change in magnetic permeability in the vicinity of the particle given constant applied magnetic and applied stress fields is evaluated.

Development of elasto-magnetic (EM) sensor for monitoring cable tension using an innovative ratio measurement method

The magnetic permeability changes of ferromagnetic materials under elastic stress offer the potential to measure tension based on the inverse magnetostrictive effect. The elasto-magnetic (EM) sensor is the most promising technology for monitoring tension in steel structures. Nevertheless, difference in the device channel or variation of the external wire resistance results in an inaccurate induced voltage variation of the EM sensor in tension measurement. In this paper, the EM sensor for monitoring cable tension using an innovative ratio measurement method was presented. An inductor-resistor model of the excitation system and a transformer model of the sensor system were established to obtain the explicit relationship between the ratio result and the external tension. The experimental results show that the ratio of the integral value of the induced voltage to the excitation current variation is proportional to the external tension, a finding that is consistent with the theoretical derivation. In addition, the simulation analysis and experiment result demonstrate that the ratio measurement method improves sensor performance with the comparison of the traditional induced voltage method. Finally, the EM sensor was applied in the Zhengzhou Olympic Stadium of China. The monitoring results show that the proposed ratio measurement method could accurately measure cable tension.

Stress Monitoring in Steel Elements via Detection of AC Magnetic Permeability Changes

Stress Monitoring in Steel Elements via Detection of AC Magnetic Permeability Changes

Sensing strain with Ni-Mn-Ga

Abstract Deformation rearranges the crystal lattice in magnetic shape memory alloys, which changes all anisotropic properties of the material. This study investigates leveraging the deformation-induced change of magnetic permeability for a strain measurement technique. A Ni-Mn-Ga single crystal placed inside a doubly wound coil with a primary and a secondary winding was used as a strain sensor. An AC voltage excited the primary coil and the secondary voltage was measured as the sample was strained from 0 to 5.2%. This method varies from other methods that utilize complex magnetic circuits, require high magnetic fields, or other sensing methods such as Hall probes. When the sensor element was tested statically by compressing the element manually against a bias magnetic field perpendicular to the load axis, the voltage output varied from 129.7 mV to 164.2 mV. The dynamic performance of the sensor was tested by cycling the element between 25 and 100 Hz in compression against a bias magnetic field in a displacement controlled magneto-mechanical test system. The bias magnetic field was varied from 0.2 to 0.8 T (0.16 to 0.64 MA/m) while the cyclic displacement was varied from 0.5 to 4.5% strain. The voltage amplitude of the signal in the secondary coil increased with decreasing tensile strain. The full scale RMS voltage at a 200 mm stroke increased from 53.0 mV to 78.4 mV as the bias magnetic field decreased from 0.8T to 0.2 T. As the element was compressed, there was no difference in the sensor output voltage between the static and dynamic tests. When the element expanded during unloading, the voltage output of the sensor from the static test matched the voltage output during compression. For the dynamic testing, the voltage output of the sensor exhibited a hysteresis from the loading voltage output, the hysteresis increased when the strain rate increased.

Sensitivity of fields generated within magnetically shielded volumes to changes in magnetic permeability

Future experiments seeking to measure the neutron electric dipole moment (nEDM) require stable and homogeneous magnetic fields. Normally these experiments use a coil internal to a passively magnetically shielded volume to generate the magnetic field. The stability of the magnetic field generated by the coil within the magnetically shielded volume may be influenced by a number of factors. The factor studied here is the dependence of the internally generated field on the magnetic permeability μ of the shield material. We provide measurements of the temperature-dependence of the permeability of the material used in a set of prototype magnetic shields, using experimental parameters nearer to those of nEDM experiments than previously reported in the literature. Our measurements imply a range of 1μdμdT from 0–2.7%/K. Assuming typical nEDM experiment coil and shield parameters gives μB0dB0dμ=0.01, resulting in a temperature dependence of the magnetic field in a typical nEDM experiment of dB0dT=0−270 pT/K for B0=1μT. The results are useful for estimating the necessary level of temperature control in nEDM experiments.

Research and progress in developing key technologies for practical saturated iron-core superconducting fault current limiters

Saturated iron-core superconducting fault current limiter is one of the various types of superconducting fault current limiters studied in recent years. The principle was first proposed by Raju’s group in the early 1980’s, which utilizes the intrinsic property of a magnetic core, i.e. change in magnetic permeability at different magnetization states, resulting in the change in impedance of the coil wound around it. There have been some technical difficulties for it to satisfy the utility’s requirement in functional capacity, safety, and reliability, which prevents this kind of device from practical application. This article introduces our progresses in solving these technical difficulties in last ten years. These progresses include: ensuring a deep and stable saturation of the iron-core’s working section by cross-sectional area variation of the core in a loose coupling structure, paving the way for high voltage grid applications; adopting a fast switching mechanism for the DC bias circuit to avoid high induced voltage during fault current limiting, protecting the device from damaging and enhancing its operation safety; by meas of the combination of high power mode and low power mode in magnetization and the use of varistor energy release unit, shortening the device’s recovery time to satisfy the grid re-closure requirement; taking on the three phases in one configuration to optimize the iron-core structure, reducing the size and the weight of the device and lowering the costs of manufacture, transportation and installation; eliminating the problem of induced eddy current and large coupling current on a metal oil-tank by using separated fiber glass oil-tanks. These new technologies make a saturated iron-core superconducting fault current limiter an ideal short-circuit fault current limiting device, a superior choice particularly for high voltage power grids.

The correlation between structural relaxation process and the change in magnetic permeability of the Fe73.5Cu1Nb3Si15.5B7 amorphous alloy under the thermal influence

The correlation between structural relaxation process and the change in magnetic permeability of the Fe73.5Cu1Nb3Si15.5B7 amorphous alloy under the thermal influence

Real-time electromagnetic seed drop detection for permanent implants brachytherapy: Technology overview and performance assessment.

To describe the principles and report on the performance of a novel real-time electromagnetic (EM) seed drop detection technology for permanent implants brachytherapy procedures. A novel EM hollow needle prototype was recently developed by Philips. It possesses standard 3D tracking capability as well as a seed drop detection mechanism, both performed from a single custom built EM sensor. The detection mechanism is based on the magnetic permeability changes in the sensor as the seeds pass through. Drop position estimates are generated by the tracking information at the dropping instants. Three validation experiments were carried out in this study. First, the robustness of the detection mechanism was tested in free air with four different seed types. Detection waveforms were measured and commented. The accuracy of the seed drop position estimates was then evaluated using both 2D and 3D experiments. The procedures consisted of dropping seeds in phantoms, recording the drop position estimates, and finally registering the resulting spatial distributions on reference ones obtained by accurate modalities. Seeds were dropped on a specially designed plastic support adapted to brachytherapy template dimensions for 2D experiments, and true seed positions (reference distribution) were obtained by optical detection. In 3D experiments, seeds were dropped in edible gelatin and reference distributions were obtained by localizing the implants from CT scans of the phantoms. All four seed types were correctly detected by the needle prototype. In total, 250 seeds were dropped on the plastic support, and 96 were dropped in gelatin phantoms. The detection rate was 100% in both cases. The minimum, maximum, and average drop position errors were, respectively, 0.1(+1.6/ - 0.1), 2.9(+1.4/ - 1.5), and 0.9(+1.4/ - 0.7) mm for 2D, and 0.1(+1.0/ - 0.1), 2.1(+1.1/ - 0.8), and 0.6(+1.2/ - 0.5) mm for 3D experiments. The hollow needle prototype combines both EM tracking and automatic seed drop detection in a compact and convenient form. The EM detection mechanism is robust, and the seed drop position estimates appear sufficiently accurate for potential integration of the technology to current brachytherapy treatment planning systems. In that context, it would serve as a valuable tool for rapid dosimetry validation in real-time treatment delivery.

Accuracy Improvement of Low‐Invasive Temperature Measurement for Hyperthermia Treatment Using a Ferromagnetic Implant with Low Curie Temperature

SUMMARYWe investigated a hyperthermia treatment method in which a ferromagnetic implant with a low Curie temperature (FILCT) is implanted into a malignant tumor and then a high‐frequency magnetic field is applied outside the body. In earlier studies, we confirmed that the target temperature of the tumor can be noninvasively monitored by detecting changes in the magnetic field caused by changes in magnetic permeability. It was very difficult, however, to detect the FILCT temperature if the applied magnetic field was in an unstable state. Additionally, if the initial bias is higher, it is more difficult to detect the FILCT temperature because the resolution of the lock‐in amplifier is reduced. In order to improve the accuracy of low‐invasive temperature measurement, we formulated a method that reduces the drift in the pickup coil voltage caused by instability from the applied magnetic field. In addition, we experimentally confirmed that the influence of fluctuations in the applied magnetic field can be reduced by adjusting the initial bias value to close to 0 V.

Liquid pressure wireless sensor based on magnetostrictive microwires for applications in cardiovascular localized diagnostic

In this letter, we report a method to measure changes in a fluid pressure, flowing through a flexible pipeline, by means of a ring of magnetic microwire concentric to the pipeline. The detection is based on the modulated scattering of electromagnetic waves by the magnetoelastic ring. This modulation is driven by applying a low frequency bias magnetic field able to tune the magnetic permeability of the ferromagnetic microwire. Pressure detection, by means of magnetic permeability changes, is possible due to the magnetostrictive character of the sample. The experimental work developed has, also, allowed fluid pressure detection in a hydraulic circuit connected to ventricular assist system where a fluid with a viscosity close to blood flows.

A model-based method for the characterisation of stress in magnetic materials using eddy current non-destructive evaluation

A precise knowledge of the distribution of internal stresses in materials is key to the prediction of magnetic and mechanical performance and lifetime of many industrial devices. This is the reason why many efforts have been made to develop and enhance the techniques for the non-destructive evaluation of stress. In the case of magnetic materials, the use of eddy current (EC) techniques is a promising pathway to stress evaluation. The principle is based on the significant changes in magnetic permeability of magnetic materials subjected to mechanical stress. These modifications of magnetic permeability affect in turn the signal obtained from an EC probe inspecting the material. From this principle, a numerical tool is proposed in this paper to predict the EC signal obtained from a material subjected to stress. This numerical tool is a combination of a 3D finite element approach with a magneto-mechanical constitutive law describing the effect of stress on the magnetic permeability. The model provides the variations of impedance of an EC probe as a function of stress. An experimental setup in which a magnetic material subjected to a tension stress is inspected using EC techniques is tailored in order to validate the model. A very good agreement is found between experimental and modelling results. For the Iron-Cobalt alloy tested in this study, it is shown that a uniaxial tensile stress can be detected with an error lower than 3 MPa in the range from 0 to 100 MPa.

Effect of Uniaxial Stress on Magnetic Permeability and Magnetic Loss of Low-Carbon Steel in Weak Alternating Magnetic Field

The inverse magnetostrictive effect provides a chance to detect the stress by measuring some magnetic parameters. So it is important to learn the effect of stress on some magnetic parameters. A measuring system to measure magnetic permeability and magnetic loss and a device to load uniaxial tension and pressure stress were developed. The result shows that magnetic permeability and magnetic loss increase with uniaxial tension stress increase and decreases with uniaxial pressure stress increase. It is also concluded that the relative change of magnetic permeability and magnetic loss decrease with increase of the included angle between the directions of the stress and magnetic field. These results suggest that magnetic permeability and magnetic loss can be further used to evaluate the stress in low-carbon steel.

Utilizing electromagnetic properties to determine the micro-plastic limit of low-carbon steel CSN 411375

It is generally accepted that not all cyclic stresses below the fatigue limit are non-damaging. Particularly in spectrum loading, the inclusion of some cyclic stresses below the fatigue limit can reduce the fatigue lifeof acomponent. It is believed that the boundary between damaging and non-damaging stresses is the so-called micro-plastic limit (MPL) defined as a macro-stress at which dislocation pile-up stresses begin to obstruct the magnetic domains in rotation to the direction of the tensile stress. This paper shows that MPL can be determined from changes in magnetic permeability during tensile loading. In our work, changes in magnetic permeability were measured indirectly - by measuring changes in electrical impedance (a.c. resistance and inductance). Measurements were performed on normalized low-C steel CSN 411375, and the microplastic limit was determined by evaluating the Δ R- σ and Δ L- σ records.

Accuracy Improvement of Low-invasive Temperature Measurement for Hyperthermia Treatment using a Ferromagnetic Implant with Low Curie Temperature

We investigated a treatment method for hyperthermia in which a ferromagnetic implant with a low curie temperature (FILCT) is implanted into a malignant tumor and then a high-frequency magnetic field is applied outside the body. In earlier studies, we confirmed that the target temperature of the tumor can be non-invasively monitored by detecting changes in the magnetic field caused by magnetic permeability changes. It was very difficult, however, to detect FILCT temperature if the applied magnetic field was in an unstable state. Additionally, if the initial bias is higher, it becomes more difficult to detect FILCT temperature because the resolution of the lock-in amplifier is reduced. To improve the accuracy of low-invasive temperature measurement, we formulated a method that reduces the drift in the pickup coil voltage caused by instability from the applied magnetic field. In addition, we experimentally confirmed that the influence from fluctuation in the applied magnetic field can be reduced by adjusting the initial bias value near 0 V.