Search Results (125)

In this work, a methodology based on the finite element method is proposed for the design and simulation of optical modulators that exploit the magnetostrictive effect, aimed at enhancing the performance of magnetometers. The study focuses on a channel-type optical waveguide whose cross-section is carefully engineered to maximize opto-mechanical interaction while ensuring straightforward integration with magnetostrictive thin films. Fabrication follows the Induced Static Stress (ISS) technique: sputter deposition of a Terfenol-D (Tb_0.3Dy_0.7Fe_1.92) layer onto a bismuth germanium oxide (Bi₁₂GeO₄) substrate creates residual stresses because of mismatched thermal expansion coefficients. During operation, applied magnetic fields induce magnetostrictive deformation, which, together with the pre-existing thermal stresses, modifies the local refractive index via the elasto-optic effect, thereby enabling dynamic guiding and modulation of guided light. Numerical analysis is carried out in COMSOL Multiphysics 5.6, employing coupled structural and optical modules. A fine mesh is generated along the waveguide core, while material parameters such as Young’s modulus, Poisson’s ratio, magnetostriction constant, and refractive indices are specified for each layer. Full article

The inherent nonlinear hysteresis characteristics of giant magnetostrictive actuators are significantly influenced by the frequency of the input signal, and this rate-dependent effect poses severe challenges to high-precision modeling and control. To address this issue, this paper proposes an improved rate-dependent Prandtl–Ishlinskii (PI) model, which incorporates a rate-dependent envelope function with asymmetric left–right thresholds, and additional rate-dependent nonlinear terms to more accurately characterize the frequency-dependent hysteresis behavior of giant magnetostrictive actuators (GMAs). Based on this model, its inverse model is analytically constructed to achieve feedforward compensation, thereby substantially mitigating the influence of hysteresis nonlinearity. On this compensation basis, a sliding mode control strategy with prescribed performance is designed to guarantee global closed-loop stability, and to satisfy the predefined transient and steady-state performance on the tracking error. Finally, verification tests are conducted on a GMA experimental platform, and the results demonstrate that the proposed modeling and composite control scheme can effectively suppress rate-dependent hysteresis disturbances, achieving fast system response and desirable steady-state accuracy, thus validating the feasibility and engineering practicality of the method. Full article

DC bias will cause the magnetization working point of the transformer core to shift and cause local saturation, and generate abnormal vibration through the magnetostrictive effect, which threatens the safe operation of the transformer. Aiming at the problem that the time–frequency characteristics of transformer vibration signals under DC bias are complex and the adjacent bias levels are difficult to distinguish, this paper proposes a 2DWT-CNN-Transformer diagnostic method that combines two-dimensional discrete wavelet transform, a convolutional neural network, and Transformer Encoder. Firstly, the multi-physical-field finite element model of three-phase three-column transformer is established, and the L0–L5 six-class DC bias dataset is constructed. Secondly, the one-dimensional vibration signal is reconstructed into a two-dimensional matrix, and the multi-subband time–frequency features of LL, LH, HL, and HH are extracted by two-dimensional discrete wavelet transform. The local texture features are extracted by the CNN, and the multi-head self-attention mechanism of Transformer Encoder is introduced to establish the global dependence and enhance the discrimination ability of adjacent bias levels. Compared with the traditional time–frequency-feature deep learning model, the proposed method achieves higher accuracy, especially in the high-noise environment of 15 dB, where it can still maintain accuracy of 96.23%. The visualization results further show that the model can form a more compact intra-class aggregation and a clearer inter-class boundary. This also provides an effective solution for the identification and evaluation of transformer DC bias states based on vibration signals in complex environments in the future. Full article

In this work, resonator applications based on the magnetoelectric coupling effect in multiferroic materials are systematically investigated, with particular emphasis on mechanically driven ME antennas. A finite-element model is established to analyze the electromechanical response and coupling behavior of the device. To better describe the converse ME process, a nonlinear magnetostrictive model is introduced to evaluate the influence of material properties, structural configuration, and DC bias magnetic field on resonance characteristics and radiation performance. The simulation results show that the radiation intensity of the ME antenna is strongly dependent on the applied bias magnetic field and can be significantly enhanced under the optimal operating condition. On this basis, key parameters are optimized to reduce the resonance frequency and improve the radiation response. Prototype devices are then fabricated and experimentally characterized. The measured results verify the predicted resonance behavior and demonstrate the feasibility of the proposed devices in low-frequency wireless communication and magnetic-anomaly sensing. This study provides theoretical guidance and experimental support for the design of portable low-frequency ME antenna systems and other resonator-based magnetoelectric devices. Full article

Magnetostrictive patch transducers (MPTs) are highly efficient for generating and detecting ultrasonic waves for non-destructive evaluation (NDE), though their use on cementitious media and fibre-reinforced concrete has not yet been investigated. In this study, a COMSOL simulation, validated with laser-Doppler vibrometry, was first used to quantify patch deformation for use in subsequent simulation of wave propagation in samples. The MPT system was then validated on thin glass plates, producing tunable A₀, S₀, and SH₀ modes through frequency-wavelength matching. In cementitious mortar plates, SH₀ and SH₁ modes were demonstrated experimentally for the first time using MPTs. The validated COMSOL model was then used to interpret complex signals in quasi-plate and half-space cementitious mortar prisms, showing that MPTs generate Rayleigh, bulk SH, and surface-skimming SH modes. In steel fibre-reinforced concrete, surface-skimming SH wave speed correlated with increases in breaking strength even in the presence of surface features such as notches. Notably, Rayleigh wave speeds could not be measured in the presence of surface features, and the Rayleigh velocities measured in the same sample, but not in the local tested area did not correlate with SH speed. This behaviour is likely due to the non-uniform distribution of material constituents, including fibre-reinforcement and coarse aggregate, combined with the different propagation paths and depth sensitivities of the reported wave modes. Overall, racetrack-coil MPTs enable multimodal inspection of cementitious media, providing information on the presence of geometric features and material properties. Full article

Conventional piezoelectric transducers suffer from stringent coupling demands and poor environmental robustness, limiting their utility for defect detection in the flat steel of down conductors in grounding grids. To overcome this, this study presents a Lamb wave excitation source based on magnetostriction. A mechanism model of the excitation source is established by analyzing the coupling among coil-driven electromagnetic excitation, magnetostrictive deformation, mechanical loading, and Lamb wave propagation in flat steel. The excitation source configuration and magnetization scheme are designed according to the geometric features of the down conductor. The experimental results show that, under pulsed current excitation, the magnetostrictive material produces a transient mechanical response, injecting disturbances into the flat steel and thereby enabling Lamb wave detection. The proposed source is compact and robust, showing strong potential for field applications. This study provides a novel active guided-wave solution for defect detection in the flat steel of down conductors and lays a foundation for subsequent signal analysis and engineering practice. Full article

Magnetostrictive sensors based on the inverse magnetostrictive effect offer the advantages of wireless passive operation and structural simplicity; however, achieving both high sensitivity and superior linearity remains a persistent challenge. This study presents a magnetostrictive pressure sensor incorporating a tunable Poisson’s ratio (TPR) chiral auxetic honeycomb substructure, designed to linearize the stress response of the sensing material. A theoretical model linking substructure design parameters to sensor output linearity was derived and validated through finite element simulations. The fabricated substructure exhibited a stable negative Poisson’s ratio (−1.278 to −1.213) within its elastic regime and a highly linear axial-to-transverse strain relationship (x = 1.214y + 0.113). The sensor achieved a calibration linearity of R² = 0.99745, a continuous linear force response up to 118.7 N while the corresponding voltage variation reached 10.75 mV, and a maximum hysteresis error of 5.495% over eight loading cycles. Bearing press-fit force monitoring experiments confirmed practical viability under industrial conditions, with R² exceeding at least 0.995 for dry assembly between multiple bearing types and maintaining R² > 0.994 under lubricated conditions. The proposed TPR substructure approach establishes a reference framework for linearity enhancement in inverse magnetostrictive force sensors. Full article

This paper presents an effective approach to reducing noise and vibration levels in ultra-high-voltage (UHV) shunt reactors based on structural optimization and damping techniques. The main sources of vibration are associated with magnetostriction of electrical steel and electromagnetic forces in the magnetic system, which induce structural excitation of the reactor tank. A combined numerical and experimental methodology is employed, including finite element modeling (FEM) of the reactor tank and field measurements of vibration displacement and acoustic noise. In contrast to previous studies focused primarily on material properties, this work emphasizes the role of structural modifications in controlling vibration transmission. The proposed solutions include the use of nitrile butadiene rubber (NBR) damping elements, optimization of the magnetic system geometry, and reinforcement of the tank structure using vertical and horizontal stiffeners. The FEM analysis in the frequency range of 50–150 Hz shows that the maximum displacement amplitude reaches 16.2 μm at the tank bottom and 10.5 μm at the tank walls. Experimental results confirm a reduction in vibration levels to 13 μm and a sound power level of 88 dBA, which meets regulatory requirements. The proposed approach improves the vibroacoustic performance and operational reliability of UHV reactors and can be effectively applied in the design of modern high-voltage power equipment. Full article

DC bias is a primary cause of anomalous vibration and noise in power transformers. This study investigates the magnetostriction characteristics of grain-oriented silicon steel sheets under simultaneous AC excitation and DC bias. A novel prediction method is proposed, which integrates multi-scale mutual information features with frequency-domain features, and employs a long short-term memory (LSTM) network for DC bias identification. The experimental platform with six voltage levels and seven bias ratios was set up to collect strain signals under various operating conditions. The results indicate that DC bias alters the magnetostriction spectrum by modulating the nonlinear response. Specifically, the amplitude of the 100 Hz harmonic decreases monotonically as bias increases, whereas the high-frequency harmonics are noticeably amplified, leading to greater waveform asymmetry and harmonic distortion. The proposed prediction model achieves a root-mean-square error (RMSE) of 0.0336 and a coefficient of determination (R²) of 0.8810 under stratified 5-fold cross-validation, offering theoretical support and experimental evidence for DC bias monitoring and transformer condition assessment. Full article

First, the properties of the linear magnetizing curve and low static permeability are summarized. Second, a design for technical implementation of mechanical stress-induced anisotropy in metal-amorphous nanocomposites (MANCs) is presented. Stress annealing, which creates the conditions for a linear magnetizing curve, is an order of magnitude more effective with Co-based MANCs than with Fe-based ones. Permeabilities between 3000 and 100 and between 100 and 10 can be obtained in Fe- and Co-based nanocomposites, respectively, at similar applied tensile stresses. A measure of linearity is introduced based on the parameters of the hysteresis loop, which is proven to be equal to the fraction of the crystalline phase responsible for the induced anisotropy. Lastly, experimental results concerning linearity and related properties are discussed. Full article

Magnetorheological elastomers (MREs) have attracted considerable attention in high-precision sensing and intelligent control due to their responsive sensitivity. The magnetostrictive properties of MREs excited by magneto-mechanical coupling at the mesoscopic scale show broad application potential but have not yet been fully elucidated. In this study, the magnetostrictive properties were investigated at the mesoscopic scale through theoretical modeling, numerical simulation and experimental research. A correction factor was introduced to address the limitations of conventional magnetic dipole theory under near-field conditions, thereby providing a rational theoretical explanation of magnetostrictive behavior. Visualization analysis was performed using the finite element method (FEM). Subsequently, MREs were prepared under various solidified magnetic fields, and their performance was validated through scanning electron microscopy (SEM) and a laser displacement sensor. The results demonstrated that magnetostriction is determined by the relative angle between the particle chain and the magnetic field direction. The linearity of the particle chain was found to be positively correlated with magnetostriction. The maximum theoretical and experimental magnetostrictive elongations reached 0.9% and 0.565%, respectively, while the maximum theoretical and experimental magnetostrictive compression reached 2.77% and 1.81%, respectively. This work provides significant scientific insights into the magneto-mechanical energy conversion mechanism and contributes to the development of magnetostrictive instruments. Full article

The variable-pitch connecting rod of a helicopter bears axial tensile and compressive loads during operation. The traditional load monitoring method using strain gauge is easily affected by external conditions. Therefore, a giant magnetostrictive (GM) tension and compression force sensor with permanent magnet bias is proposed and optimized. Because the bias magnetic field plays a decisive role in the performance of the sensor, this paper has carried out in-depth research on this. Firstly, the mathematical model of the magnetic circuit is established, and the various magnetic circuits of the sensor are simulated and analyzed. Secondly, the magnetic flux uniformity of the GMM rod is used as the evaluation index, and the relative permeability of the magnetic material and the structure are systematically studied. The influence of parameters on the magnetic flux of the magnetic circuit, and finally the optimal parameter combination of the magnetic circuit is determined by orthogonal test. The results show that when the magnetic circuit without the magnetic side wall is used, the magnetic material can better guide the magnetic flux through the GMM rod; the magnetic flux uniformity of the optimized GMM force sensor is increased by 7.44%, the magnetic flux density is increased by 13.9 mT and the Hall output voltage increases linearly by 1.125% in the same proportion. This provides an important reference for improving the utilization rate of GMM rods and also improves the safety of flight operation and reduces maintenance costs. Full article

The dynamic model and nonlinear forced vibration of a laminated beam with magnetostrictive layers, embedded on a nonlinear elastic Winkler–Pasternak foundation, in the presence of an electromagnetic actuator, mechanical impact, dry friction, a longitudinal magnetic field, and van der Waals force is investigated in the present work. The dynamic equations of this complex system are established based on von Karman theory and Hamilton’s principle. Then, by means of the Galerkin–Bubnov procedure, the partial differential equations are transformed into ordinary differential equations. The Optimal Auxiliary Functions Method (OAFM) is applied to solve the nonlinear differential equation. The results obtained are validated by comparisons with numerical results given by the Runge–Kutta procedure. Local stability in the neighborhood of the primary resonance is examined by means of the homotopy perturbation method, the Jacobian matrix, and the Routh–Hurwitz criteria. Global stability is studied by introducing the control law input function and using the approximate solution obtained by the OAFM in the construction of the Lyapunov function. La Salle’s invariance principle and Potryagin’s principle complete our study. The effects of some parameters are graphically presented. Our paper reveals the immense potential of the OAFM in the study of complex nonlinear dynamical systems. Full article

This study investigates the vibration and noise characteristics of oil-immersed power transformers, with a particular focus on the influence of transformer oil on structural dynamics and acoustic emission. The research integrates multi-physics modelling, finite-element simulation, and field measurements to analyze the vibration transmission paths from the core and windings to the tank wall. A fluid–structure interaction (FSI) model is developed to account for the damping effect of insulating oil, and a correction factor is introduced to adjust modal parameters. Simulation results reveal that oil significantly enhances vibration propagation, especially in the vertical direction, while structural ribs and clamping configurations affect local vibration intensity. Noise simulations show that magnetostriction is the dominant source of audible sound, with harmonic components sensitive to load and voltage variations. Experimental validation using a portable sound level meter confirms the simulation trends and highlights the spatial variability of acoustic pressure. The findings provide a theoretical and practical basis for optimizing sensor placement and developing voiceprint-based diagnostic tools for transformer condition monitoring. Full article

A multiphysics-coupled 2–2 cement-based magnetoelectric composite model is established in COMSOL 6.2. This model is used to not only systematically investigate the magnetoelectric-coupling behavior, but also quantify the effects of the magnetic field, frequency, and layer-thickness ratio on the material’s magnetoelectric properties. The results demonstrate that the model effectively reproduces the internal stress–strain distribution and voltage evolution. Specifically, the magnetostrictive and piezoelectric layers exhibit mechanical responses with pronounced non-uniformity, which is attributed to boundary effects. The bias magnetic field plays a crucial regulatory role: the output voltage increases linearly from 0 to 2000 Oe and then saturates at higher fields. Under an alternating magnetic field, the composite exhibits pronounced resonance characteristics, whose frequency is jointly governed by structural dimensions and the bias field. The dynamic response was further analyzed using the magnetic flux density modulus, displacement profiles at selected locations, and voltage evolution across the piezoelectric layer. Notably, the thickness of each functional phase exerts a pronounced and distinct influence on the composite’s magnetoelectric coupling, with markedly different trends between phases. Optimization results show that a thin piezoelectric layer combined with a thick magnetostrictive layer yields the highest magnetoelectric performance. Additionally, the longitudinal and transverse magnetoelectric coefficients exhibit markedly different coupling mechanisms—this is owing to the misalignment between the magnetic-field and electric-polarization directions, and this difference further reveals the intrinsic anisotropy of the magnetoelectric response. Overall, this study provides a crucial theoretical foundation for the design and optimization of high-performance cement-based magnetoelectric composites. Full article