Magnetomechanical Coupling Effect Research Articles

Magnetostrictive bi-perceptive flexible sensor for tracking bend and position of human and robot hand

The sensor that simultaneously perceives bending strain and magnetic field has the potential to detect the finger bending state and hand position of the human and robot. Based on unique magneto-mechanical coupling effect of magnetostrictive materials, the proposed a bi-perceptive flexible sensor, consisting of the Co–Fe film and magnetic sensing plane coils, can realize dual information perception of strain/magnetic field through the change of magnetization state. The sensor structure and interface circuit of the sensing system are designed to provide high sensitivity and fast response, based on the input–output characteristics of the simulation model. An asynchronous multi-task deep learning method is proposed, which takes the output of the position task as the partial input of the bending state task to analyze the output information of the sensor quickly and accurately. The sensing system, integrating with the proposed model, can better predict the bending state and approach distance of human or robot hand.

Experimental study on strengthening the magneto-mechanical coupling effect of X80 steel by weak magnetic excitation

Abstract Current magnetic stress detection techniques are significantly impacted by external noise signals. The magnetic stress detection technology under excitation magnetic fields is proposed to weaken the external noise signals on the detection results. In this study, the uniaxial tensile magnetic signal testing system with the excitation magnetic field was built. The enhancement of the weak magnetic excitation on magnetic signals has been quantitatively analyzed and the concept of optimal weak excitation magnetic field has been proposed. The response law between triaxial magnetic induction intensity and stress under the excitation magnetic field is determined. The results indicate that the weak excitation magnetic field significantly enhances the magnetic induction signal intensity, more importantly, the linearity of the magnetic signal and stress response is also enhanced. Furthermore, the optimal excitation magnetic field under uniaxial stress states is 600 A/m, and the corresponding stress-magnetic change rate is 0.002 Oe/MPa. This study provides a theoretical basis for the long-distance detection of pipelines under weak magnetic excitation. The long-distance magnetic stress detection results of pipelines will become more accurate with the weak magnetic excitation which has a good engineering significance.

A finite-strain plate model for the magneto-mechanical behaviors of hard-magnetic soft material plates

In this paper, we propose a plate model, within the framework of finite-strain elasticity, to study the magneto-mechanical behaviors of hard-magnetic soft material plates. The 2D vector plate equation is derived from the 3D governing equations through a series expansion and truncation approach. The displacement and traction boundary conditions on the edges of plate samples are also proposed. Compared with the other plate or shell theories, the current plate model naturally incorporates the elastic incompressibility and the magneto-mechanical coupling effect of the material, which doesn't involve any a priori hypotheses on the geometry and deformation of the plates. Thus, it is applicable for modeling the large deformations of hard-magnetic soft material plates. To show the efficiency of the plate model, we study a benchmark problem, i.e., the plane-strain bending deformations of plate samples induced by magnetic and mechanical loads. Some analytical solutions of the plate equation system are derived, which provide accurate predictions on the magneto-mechanical response of the plate samples with different thickness-length ratios and magnetization directions. To promote applications of the plate model, we further derive a simplified plate equation system and write out its weak form, which is then implemented into the finite element software COMSOL Multiphysics. The efficiency of the simplified plate equation system is also verified through some typical examples. It is found that the numerical results obtained from the 2D plate model show good consistency with those of the 3D volume model, while the plate model exhibits obvious advantages in the aspects of numerical efficiency.

Modeling and simulation of magnetostrictive actuators based on ΔE effect Preisach model

Based on the classical Preisach model, combined with the magneto-mechanical coupling effect of Giant magnetostrictive materials (GMM), this paper introduces the Everett function to optimize the classical Preisach hysteresis model and improve its accuracy. By importing dynamic parameters, the dynamic Preisach hysteresis model is established. Combined with the constitutive model of GMM, a dynamic Preisach hysteretic nonlinear magnetostrictive actuator model based on the ΔE effect is established. Then, the finite element simulation is carried out by Comsol software and compared with the theoretical model simulation. The results show that the error between the magnetostrictive strain of the established hysteresis model and the finite element simulation results is less than 100 ppm, which verifies the accuracy of the proposed model. Finally, the curves of magnetic field intensity, magnetic induction intensity, magnetization, magnetostrictive strain and ΔE effect of GMA are obtained by using this model.

Magneto-Mechanical Coupling Study of Magnetorheological Elastomer Thin Films for Sensitivity Enhancement.

Magnetorheological elastomer thin films (MREFs) exhibit remarkable deformability and an adjustable modulus under magnetic fields, rendering them promising in fields such as robotics, flexible sensors, and biomedical engineering. Here, we fabricated MREF by introducing magnetostrictive particles (MSPs) and evaluated the magneto-mechanical coupling effect on the enhancement of sensitivity. The saturation magnetization (Ms) in a parallel anisotropic TbDyFe-PDMS MREF was 5.8 emu/g, and the initial tensile modulus was 55% greater than that of an Iso MREF. We propose a nonlinear magnetorheological formula on the magnetostriction effect, incorporating magnetic dipole interactions and the nonlinear prestress of magnetic particles. This formula highlights the complex nonlinear relationship between the external magnetic field (H) and the key parameters that affect the enhanced MR effect of MSPs-MREF, such as saturation magnetization, remanence (Mr), magnetostriction constant (λs) and stress deviator in ferromagnetic particles (Sed) in the magnetic chain structure. Furthermore, we validate the influence of the key parameters of the rectified magnetorheological formula on a nonlinear magneto-mechanical behavior of MSPs-MREF in PDMS-based MSPs-MREF models by using finite-element simulations. Finally, we developed a biosensor based on MSPs-MREF to detect human serum albumin at low concentrations in human urine samples. There is a 4-fold increase in sensitivity, a lower detection of limit (0.442 μg/mL), and a faster response time (15 min) than traditional biosensors, which in the future might provide an effective way of detecting biomolecules of low concentrations.

Mechanism study of strain-induced magnetic properties changes for nickel-based materials at atomic scale

Based on the magneto-mechanical coupling effect, magnetic non-destructive testing technology is widely used to test stress and defect in ferromagnetic materials. To analyze the effect of strain/stress on the atomic magnetism of Ni-based materials strain-induced changes of magnetic properties of FCC-Ni 2 × 2 × 2 supercell and its doped systems with Cu and Nb atoms are studied by the first principal density functional theory. Firstly, addition of Cu or Nb promote the expansion of nickel lattice, and Nb makes this effect more significant. Cu atoms enhance the magnetic moment of Ni atoms, while Nb atoms play an inhibitory role. Secondly, for uniaxial strain, the magnetic moments of atoms in the doping-free systems show a nearly monotonic increasing trend from compression to tension, while the doped systems show a trend of first increases and then decreases. Furthermore, for shear loading, the atomic magnetic moment decreases with increases of the shear strain. Further investigation shows that Ni atoms at different distances exhibit completely different magnetic behavior due to the influence of loadings and doping atoms. This study would be an important supplement to the physical mechanism of multi-field coupling in magnetic non-destructive testing.

Magneto-mechanical coupling effect of ferromagnetic materials: Test characteristics and theoretical model

The magneto-mechanical coupling effect of ferromagnetic materials is the result of macroscopic influence of mechanical properties on magnetic properties under the combined action of stress field and applied magnetic field, which essentially can be attributed to the change of material properties caused by the transformation of microscopic magnetic domain structures. The effect of applied magnetic field is mainly manifested as the change of magnetic moment cluster (direction and size) inside microscopic magnetic domain; The stress field mainly causes the movement and rotation of the domain walls inside the ferromagnetic material, and further causes the change of magnetic moment cluster. Taking Q235 low carbon steel as an example, the effects of tensile stress σt on some important magnetic parameters of ferromagnetic materials under different excitation intensities (i.e., H0), such as the maximum value of applied magnetic field Hmax, intrinsic coercive field Hcj, hysteresis loss power per unit volume ph and anhysteretic magnetization Man, were obtained by setting macroscopic magneto-mechanical coupling test and fully considering the influence of demagnetizing field Hd (The standard ring specimen was used for demagnetization correction of the non-standard strip specimen). Meanwhile, the basic magnetization characteristics of ferromagnetic materials were discussed by introducing the basic magnetization curve F(H0, Ban) and considering the effect of σt as the equivalent stress field Hσ based on the theory of microscopic magnetic domain and the principle of thermodynamic. In the range of 635.4 A/m ≤ H0 ≤ 928.6 A/m and 0 MPa ≤ σt ≤ 350 MPa, the theoretical calculation models Man(H0, σt) and Hσ(H0, σt) in the magneto-mechanical coupling effect were obtained, which are in good agreement with the experimental results.

A transient magneto-mechanical numerical model of a tank based on improved jiles-atherton theory

Magnetic field generated by the ferromagnetic material of underwater detectors varies with seawater pressure, which may affect the accuracy of deep-sea resource exploration. The effect of stress on magnetization is cumulative. In order to accurately simulate the influence of deep-sea pressure on the magnetic field around underwater detectors, it is very important to develop a transient magneto-mechanical numerical model. In this paper, a transient magneto-mechanical coupling model of a tank was developed to obtain the magnetic signal deviation caused by the magneto-mechanical coupling effect. By improving the Jiles-Atherton theory for complex stress and calculating the variation in magnetic field with pressure, the hysteresis effect between magnetization and stress was verified. Under different background magnetic fields, the effect of stress on magnetic field was determined by calculating the magnetic field distribution under different pressures.

A nonlinear magneto-elastoplastic coupling model based on Jiles–Atherton theory of ferromagnetic materials

As seen in the Jiles–Atherton (J–A) model and its modified form, the linear relationship between the magnetization coefficient and the stress deviates significantly from the experimental results. It is necessary to introduce many parameters that are difficult to obtain or unknown to describe the effect of elastoplastic deformation on magnetization or hysteresis, such as shape coefficient, pinning coefficient, and molecular field coefficient. In this paper, a new nonlinear magneto-elastoplastic model for ferromagnetic materials is established based on the magneto-mechanical coupling effect, and both the sixth-order term of magnetization and the nonlinear equation of the magnetization coefficient are introduced into the magnetostriction equation. In the models established in this paper, the elastoplastic deformation equivalent magnetic field is introduced into the effective magnetic field, and the Frohlich–Kennelly equation is used to describe the anhysteretic magnetization. After comparing the prediction results of different models with the available experimental results, it is observed that the proposed model in this paper exhibits superior prediction ability for magnetostrictive strain, magnetization, and hysteresis phenomena under different stresses. This paper has also analyzed the mechanism of the effect of elasto-plastic loading and residual stress on the hysteresis in different models as well as the differences between them. The determination coefficient of the proposed model in this paper is closer to 1, which is better than the existing models, indicating that it has a better fitting effect and is of great significance to the development of quantitative non-destructive testing technology.

Mechanism of strain-induced magnetic properties changes for metal magnetic memory technology on atomic scale

Magnetic non-destructive testing technology is widely used to detect stresses and defects in ferromagnetic materials based on the magneto-mechanical coupling effect. In the existing studies, calculated are the magnetic moment variations of the <i>α</i>-Fe system under axial tension and compression by using first-principles study, and the magneto-mechanical coupling mechanism is preliminarily discussed at an atomic level for the magnetic testing technology. In this work, taking the more complex doping systems Fe-C and Fe-Mn for examples, under different loading conditions of tension, compression and shearing, the coupling mechanisms such as the magnetic moment changes in different types of atomic doping systems are discussed in detail. The results show that the <i>α</i>-Fe and doping systems follow different changing laws of magnetic moments and energy under different types of strains. The detailed analyses of the density of states, the band structure, and the atomic magnetic moment show that doping elements change the morphology of band structure and the peak value of density of states by affecting the magnetic moment of Fe atoms, which leads the changing laws of magnetic moment and energy to be different from each other. In this work, discussed are the magneto-mechanical effects on the atomic level for ferromagnetic materials with different loading types, different doping elements and different element content. The results can be used as an important part of the multi-field coupling mechanism for magnetic testing technology.

Research on a theoretical model of magnetic nondestructive testing for ferromagnetic materials based on the magneto–mechanical coupling effect

In this paper, a new nonlinear magneto–mechanical coupling constitutive model, based on thermodynamic theory and the hysteresis effect, introduces the 6th order term of magnetization in the whole magnetic field and the global coupling factor related to the magneto–mechanical coupling into the magnetostrictive strain. Compared with the Zheng Xiao-Jing–Liu Xin-En model and Jiles–Atherton model, the nonlinear model precisely describes the hysteresis of the material and the magnetostrictive strain under the compressive stress and the nonlinear change of the magnetostrictive strain with stress and magnetization. The comparison of the prediction results of different models with the existing experimental data shows that the proposed model has a better prediction ability of the mid-field magnetostrictive strain, low-field magnetic flux density, and high-field magnetic flux density than other models. In addition, this paper also investigates that the effects of stress and plastic deformations on the hysteresis curve, coercivity, and remanence. The difference and mechanism of elasto–plastic deformations affecting the magnetization process of materials are obtained. Above all, the results in this paper are of great significance for the development of non-destructive testing inversion technology.

Design and Output Characteristics of Ultrasonic Transducer Based on Rare-Earth Giant Magnetostrictive Material

A new type of rare-earth giant magnetostrictive transducer, working in ultrasonic frequencies, is designed by the structural dynamic model and the dynamic coupling model. Based on the vibration, wave and frequency equations, the structural dynamic model of the transducer is established. By using COMSOL Multiphysics software parametric design method, considering the influence of materials, shapes and dimensions on the output characteristics of the transducer, the optimum mechanical structure of the ultrasonic transducer is determined. The magnetic circuit structure is analyzed by the dynamic coupling model based on the Jiles-Atherton model, Maxwell’s equations and magneto-mechanical coupling effect. The prototype of the ultrasonic transducer is fabricated. The relationship between the output characteristics and the frequency is studied. The results demonstrate that the ultrasonic transducer can work in the range of 18-22 kHz, and exhibits higher magneto-mechanical conversion efficiency at the frequency of 19.5 kHz.

Output characteristics and experimental study of a highly linear and large-range force sensor based on the Villari effect

Based on the principle of the Villari effect, a force sensor with a giant magnetostrictive material (GMM) as the sensitive element, high linearity, and a large range was studied. A Hall element integrated into the structure was used to detect the magnetic flux density and measure the external force. First, the finite element method was used to verify the validity of the intended magnetization process. Second, an equation for GMM magnetization was derived based on the Jiles–Atherton (J–A) model and the magneto-mechanical coupling effect. The relationships between magnetization and the biased magnetic field, and magnetization and the external force were analyzed under the dynamic coupling model of positive and negative effects. Finally, the influences of various biased magnetic fields and external forces on the sensor output characteristics were determined experimentally. The sensitivity of the designed force sensor was 0.337 mV/N when the bias current was 1.2 A and the preload was 120 N. When a force of 1000 N was applied, the linearity was 0.82%. The experimental results are consistent with the theoretical design values. These research results aid in the development of a highly linear, large-range force sensor. This study provides the theoretical and technical foundations for a high-performance force sensor that can be used in industrial testing.

Magnetoelastic coupling effect of Fe10Co90 films grown on different flexible substrates**Project supported by the National Natural Science Foundation of China (Grant Nos. 11674336 and 11874150).

The magneto–mechanical coupling effect and magnetic anisotropy of Fe10Co90 (FeCo) films deposited on silicon wafer (Si), flexible polyethylene terephthalate (PET), freestanding polydimethylsiloxane (PDMS), and pre-stretched 20% PDMS substrates were studied in detail. The loop squareness ratio Mr/Ms and the coercive Hc of the FeCo film grown on a PET substrate can be obviously tuned by applying a small tensile-bending strain, and those of the FeCo film grown on a freestanding PDMS substrate can only be slightly changed when applying a relatively large tensile bending strain. For the FeCo film prepared on a 20% pre-stretched PDMS, a wrinkled morphology is obtained after removing the pre-strain. The wrinkled FeCo film can keep the magnetic properties unchanged when applying a relatively large tensile bending strain perpendicular to the wrinkles. This reveals that PDMS is an ideal substrate for magnetic films to realize flexible immutability. Our results may help for developing flexible magnetic devices.

Cauchy–Maxwell equations: A space–time conformal gauge theory for coupled electromagnetism and elasticity

A space–time conformal gauge theory is used to develop a unified continuum model describing myriad electromechanical and magnetomechanical coupling effects observed in solids. Using the pseudo-Riemannian Minkowski metric in a finite-deformation setup and exploiting the Lagrangian’s local conformal symmetry, we derive Cauchy–Maxwell (CM) equations that seamlessly combine, for the first time, Cauchy’s elasto-dynamic equations with Maxwell’s equations for electromagnetism. Maxwell’s equations for vacuum are recoverable from our model, which in itself also constitutes a new derivation of these equations. With deformation gradient and material velocity coupled in the Lagrange density, various pseudo-forces appear in the Euler–Lagrange equations. These forces, not identifiable through classical continuum mechanics, should have significance under specific geometric or loading conditions. As a limited illustration on how the CM equations work, we carry out semi-analytical studies, viz. on an infinite body subject to isochoric deformation and a finite membrane under both tensile and transverse loading, considering piezoelectricity and piezomagnetism. Our results show that under specific loading frequencies and tension, electric and magnetic potentials may increase rapidly in some regions of the membrane. Explorations of this nature via the CM model may have implications in future studies on efficient energy harvesting.

Analysis method for magneto-mechanical coupled vibration of the in-vessel structures considering halo current effect and application to HL-2M tokamak

Abstract The tokamak in-vessel structures serve in strong magnetic fields. During plasma disruptions such as the vertical displacement events, the induced eddy current and the injected halo current in in-vessel structures cause the vibration of the plasma-facing components. The vibration is coupled to the magnetic field in the form of the motional eddy current. Such magneto-mechanical coupling effect may have a considerable influence on the dynamic mechanical behavior of the in-vessel structures. This paper presents a numerical approach to analyze this magneto-mechanical coupled problem based on the hybrid method of the finite element and boundary element formulation. The plasma current and the halo current are taken into account in a form of a series of movable current filaments and a pair of current source and sink. The proposed approach is applied to the numerical analysis of a simplified model of the vacuum vessel of HL-2 M tokamak under an l -mode plasma disruption. Simulation results show that the vibration is strongly damped and the maximum vertical displacement is reduced by around 30 % when considering the magneto-mechanical coupling.

Modeling of Magneto-Elastic Behavior Under Perturbations of Spontaneous Magnetic Field

Internal magnetic fields launched by the neighbor grains can influence the magneto-mechanical coupling effects of the material. However, these perturbations are often ignored and have not been taken into account in the previous works. Herein, a multiscale model is proposed for describing the magneto-elastic behavior and a localization operation is employed to deal with the perturbation of spontaneous magnetic field in magnetism. The model proposed is discussed, and two simulation results are compared each other on polycrystalline iron. The simulation results demonstrate that there is no great disturbance to the magnetization curve when the spontaneous magnetic field is taken into account. However, the perturbation has an obvious counteraction effect on magnetostrictive curve. The results are consistent with our previous hypothesis and have certain reference value and significance for experimental measurement. This kind of micro-macro strategy could then participate in the understanding of the effect of stress on the magnetic behavior, especially in the case of multiaxial loadings.

An anisotropic magneto-mechanical model of ferromagnetic materials for the magnetic memory testing method

The metal magnetic memory (MMM) method shows great potential in the early damage evaluation of ferromagnetic materials. The MMM signal is affected by the environmental magnetic field because of the magneto-mechanical coupling effect. For instance, the effect of the environmental magnetic field is connected with the angle between the environmental magnetic field and the detected structure, which is referred to as the angle effect. This paper aims to explore the angle effect on the MMM method under the weak magnetic field. An anisotropic nonlinear magneto-mechanical constitutive relationship is proposed based on the magnetic domain theory and the approach law. Compared to the existing model, the present constitutive relationship in this paper can predict the stress-magnetization curve of ferromagnetic materials under the combined action of the loading stress and the environmental magnetic field with different directions. Based on the present constitutive relationship, an anisotropic nonlinear magneto-mechanical model of the MMM method is established, and then the angle effect is discussed in detail. The prediction of the anisotropic nonlinear magneto-mechanical model shows a good agreement with experimental data. The proposed model can clarify the reasons for some complex phenomena of the MMM signal, and thus help in the practical application of the MMM method.

A study on influence of magnetic field on fracture of ferromagnetic material due to magneto-mechanical coupling effects

A study on influence of magnetic field on fracture of ferromagnetic material due to magneto-mechanical coupling effects

Magneto-dependent stress relaxation of magnetorheological gels

The stress relaxation behaviors of magnetorheological (MR) gels under stepwise shear loading are systematically investigated. The particle-enhanced effect, the magneto-induced effect, and the temperature-enhanced effect on the stress relaxation of MR gels (MRG) are discussed. For further analysis of the magneto-induced stress relaxation mechanism in MRG, a phenomenological model is established to describe the stress relaxation behavior of the matrix and the magnetic particle chains. All characteristic parameters introduced in the model, i.e. relaxation time, instantaneous modulus, and stable modulus, have well-defined physical meanings and are fitted based on the experimental results. The influence of each parameter on the macroscopic response is discussed and it is found that the relaxation stress induced by the magneto-mechanical coupling effect plays an important role in the stress relaxation process of MRG.