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A magnetic non-destructive inspection method based on measurement of the magnetic flux leakage near the material surface has been studied for carbon steel pipes used in various plants. However, in actual plants, stress fluctuations caused by changes in the temperature and internal pressure of the fluid passing through the pipes may affect the residual magnetization state due to magnetomechanical effect and prevent accurate inspection. In this paper, we applied cyclic stress to pre-magnetized STPG370 carbon steel up to 107 cycles and measured the change of the magnetization state as the change of the magnetic field near the specimen surface. As a result, under the environmental magnetic field, the magnetization (or corresponding magnetic field near the specimen surface) of the specimen decreases significantly after the first few cycles of stress loading, which suggests the magnetization state approaches the anhysteretic (stable) magnetization state. Furthermore, the magnetization gradually decreases further with higher cycles of stress loading.

When an electromagnetic transient occurs in a transformer, certain parts of the winding will be over stressed internally, which in severe cases will lead to the destruction of the winding insulation. Excitation inrush current and short-circuit current are the main causes of winding damage during electromagnetic transients, resulting in or accelerating winding damage, and the presence of short-circuit current and excitation inrush current can greatly reduce the service life of power transformers. The process of closing and energizing a transformer generates a large excitation inrush, and when the current amplitude is the same, the excitation inrush generates a greater electromagnetic force than the short-circuit current. In this paper, the field-path coupling method and the finite element method (FEM) are combined to analyze the magnetomechanical effects on the transformer winding through the principle analysis and simulation, comparing the excitation inrush and short-circuit current scenarios, analyzing and concluding the leakage characteristics of the excitation inrush and short-circuit current and the winding force deformation results.

In this paper, we theoretically investigated stress-induced magnetic anisotropy and presented a model based on a unidirectional tensile stress experiment. Firstly, the theoretical model was simulated based on the work of Jiles. Secondly, experiments were conducted, and data under unidirectional tensile stress were collected and analyzed. Finally, the model was developed by correlating the experimental data and theoretical model. Our model provides a good description of stress-induced magnetic anisotropy under unidirectional tensile stresses and lays down a foundation for the quantitative testing and evaluation of stress of ferromagnetic materials through the magnetic method.

This article reviews the ferromagnetic hysteresis, magnetomechanical, and Barkhausen properties of magnetic materials and presents an integrated model to describe these effects and the underlying mechanisms that cause these effects. Hysteretic properties of ferromagnets, such as permeability, coercivity, remanence, and hysteresis loss are known to be sensitive to external factors including applied stress, temperature, and heat treatment, and internal factors like residual strain, microstructure, grain size, and anisotropy and the presence of precipitates of a second phase, such as iron carbide in steels. It thus becomes imperative to characterize the effect of these factors on the hysteresis parameters. Currently, several models such as Preisach, Stoner–Wohlfarth, and Jiles–Atherton are used to describe the magnetic hysteresis of ferromagnetic materials. We review here the quasistatic Jiles–Atherton hysteresis model which describes hysteresis in terms of domain wall motion enabling a connection to be made to the physical response of the magnetic material. This model has been extended to include the magnetomechanical effect and the Barkhausen effect in ferromagnetic materials. Theoretical work presented here provides a conceptual framework linking together these magnetic property measurements with model parameters and to the structure of the material. [ABSTRACT FROM AUTHOR]

The magnetomechanical effect describes a phenomenon for magnetic materials, and most studies focus on ferromagnetic materials. To further study the mechanism of the magnetomechanical effect, the characteristics of the magnetomechanical effect of aluminum alloy 2A12 are experimental studied in this paper. The experimental magnetic hysteresis losses of the aluminum alloy under different stresses and plastic deformations are calculated, and its quantitative correlations with stress and plastic deformation are compared. It is found that (1) in the elastic deformation stage, the magnetic hysteresis loss increases approximately linearly with the increase of stress; (2) in the plastic deformation stage, the magnetic hysteresis loss decreases approximately linearly with the increase of plastic deformation. This study not only has engineering application value to quantitative evaluation stress and plastic deformation of aluminum alloy 2A12 but also has significance and reference value to further study the mechanism of the magnetomechanical effect. [ABSTRACT FROM AUTHOR]

Stress concentration and microscopic defects inside a component can cause the failure of equipment and mechanical structures, and traditional non-destructive testing (NDT) methods are not able to completely solve this problem. The magnetomechanical effect organically combines the magnetic field and stress, making it an important approach for detecting stress concentration and microscopic defects in a component. The magnetomechanical model proposed by Jiles can explain the non-linear relationship between stress and magnetic induction, but it fails to explain the asymmetry in the change of magnetisation under the conditions of tensile and compressive stress. A general nonlinear magnetomechanical model proposed by Shi can more precisely explain the magnetomechanical effect, but with complex equations. Using a more precise equation for magnetostrictive strain and taking into account the effects of the demagnetising field and a linear stress-dependent term on the magnetomechanical effect, this paper proposes a concise and accurate model based on the merits of the two methods. This theoretical model can demonstrate the magnetomechanical effect more accurately than Jiles' model and is easier to solve and apply than Shi's model. This model offers the possibility of quantitative measurement of stress concentration by magnetic measurements. [ABSTRACT FROM AUTHOR]

Copyright of Metallophysics & Advanced Technologies / Metallofizika i Novejsie Tehnologii is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Electric machines are subjected to mechanical stress during their operation, which significantly affects the magnetic characteristics of the core material. Furthermore, as the converter topologies evolve, the induced harmonic content increases. The analysis of magnetic properties due to both magnetomechanical effects and harmonics is rarely addressed. This work provides a deeper insight into the core loss behavior by analyzing the impact of mechanical stress on the hysteresis characteristics of magnetic materials subjected to non-sinusoidal excitation. A qualitative analysis based on the measured characteristics is presented to study the material behavior under sinusoidal and non-sinusoidal excitations. An analytical approach based on the Lavers' formula and loss separation theory is presented. • Magnetic material is subjected to compressive stress under non-sinusoidal excitation. • A qualitative analysis and modeling of magnetic characteristics are presented. • An analytical approach using loss separation theory and Lavers' formula is proposed. • Loss coefficients consider the effect of applied stress on magnetic characteristics. [ABSTRACT FROM AUTHOR]

With the recent developments in science and technology, torque measurements have been widely used in many fields. However, present torque measurement methods have limitations for long-term applications. Therefore, a new method of non-contact torque measurement based on the magnetomachanical effect is reported that may be used in reducing fatigue for long-term measurements. The theory of the changes in magnetization with torque are analyzed to construct a model. Hence, an experiment platform was constructed that includes an excitation coils, shaft, and Gauss meter. The relationship between the magnetic induction and the torque was measured using this apparatus. The results show that the experimental measurements are in agreement with mathematical models obtained using magnetomechanical concepts. The results also show that the maximum nonlinearity error of the system is 0.6% and the maximum repetitive error is 3.125%. Additionally, this proposed method meets the requirements for long-term torque measurements and may also be used for the non-contact characterization of the torque of watercraft and airplanes. [ABSTRACT FROM AUTHOR]

Mechanical stress of diverse origin alters the magnetic properties of the core material of electrical machines during operation and, as a result, the magnetic flux path and particularly iron loss. In this paper, based on mechanical stress-dependent magnetic characterisation of non-oriented electrical steel sheet, the behaviour of the specific iron loss and its components are determined and modelled for compressive and tensile stress using stress-dependent iron loss seperation. An approach is presented to model the hysteresis loss component without dc measurements. Here, the focus is set on high frequencies and magnetic flux densities. As a result, a high sensitivity of the components particularly to mechanical compressive stress can be observed and modelled. [ABSTRACT FROM AUTHOR]

High internal temperature and pressure often induces the subsea pipelines to buckle and then crack. This paper exposes the magnetic field distribution characterizations inside buckling pipelines in order to detect the buckling via magnetic measurements. J-A force-magnetic coupling model is used to obtain the permeability μr as a function of the stress σ. Finite element method with multiphysics coupling is deployed to calculate the magnetic fields inside the buckling pipe with different magnetizations, temperatures, and pressures by importing the μr-σ curve. The results demonstrate that complicated stress fields cause the magnetic fields inside the buckling pipe to have many noticeable characteristics that can be deployed to reliably and precisely identify the buckling. The signs and magnitudes of the buckling stress vary significantly in different cross-sections, and even reverse at the buckling starts, where the axial and radial components have two peaks and two peak-valleypeaks symmetrically distributed about the middle plane, respectively. The magnetic fields can reveal tiny buckling with stress but without visible deformation. [ABSTRACT FROM AUTHOR]

Elongations of magnetoactive elastomers (MAEs) under ascending–descending uniform magnetic fields were studied experimentally using a laboratory apparatus specifically designed to measure large extensional strains (up to 20%) in compliant MAEs. In the literature, such a phenomenon is usually denoted as giant magnetostriction. The synthesized cylindrical MAE samples were based on polydimethylsiloxane matrices filled with micrometer-sized particles of carbonyl iron. The impact of both the macroscopic shape factor of the samples and their magneto-mechanical characteristics were evaluated. For this purpose, the aspect ratio of the MAE cylindrical samples, the concentration of magnetic particles in MAEs and the effective shear modulus were systematically varied. It was shown that the magnetically induced elongation of MAE cylinders in the maximum magnetic field of about 400 kA/m, applied along the cylinder axis, grew with the increasing aspect ratio. The effect of the sample composition is discussed in terms of magnetic filler rearrangements in magnetic fields and the observed experimental tendencies are rationalized by simple theoretical estimates. The obtained results can be used for the design of new smart materials with magnetic-field-controlled deformation properties, e.g., for soft robotics.

Abstract: The objective of this research is to explore the correlation between uniaxial ratcheting behaviour and magnetic response under asymmetrical cyclic stressing in X80 pipeline steel. The magnetic field variations from cycle to cycle were recorded simultaneously during ratcheting. Analysis made in the present work shows that the magnetic hysteresis loop evolves systematically with the number of cycles in terms of its shape and position. The most prominent result here is that the magnetic field under a certain stress first decreases sharply in the preliminary stage of ratcheting, followed by a stable decreasing period with an approximately linear slope. Furthermore, it can be concluded that ratcheting influences the changes in magnetic field more significantly under tensile stress than compressive stress. The underlying reason of the strong non‐linearity of the magnetic field evolution was discussed. [ABSTRACT FROM AUTHOR]

Copyright of Metallophysics & Advanced Technologies / Metallofizika i Novejsie Tehnologii is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

It is widely accepted that the magnetic state of a ferromagnetic material may be irreversibly altered by mechanical loading due to magnetoelastic effects. A novel standardized nondestructive testing (NDT) technique uses weak magnetic stray fields, which are assumed to arise from inhomogeneous deformation, for structural health monitoring (i.e., for detection and assessment of damage). However, the mechanical and microstructural complexity of damage has hitherto only been insufficiently considered. The aim of this study is to discuss the phenomenon of inhomogeneous “self-magnetization” of a polycrystalline ferromagnetic material under inhomogeneous deformation experimentally and with stronger material-mechanical focus. To this end, notched specimens were elastically and plastically deformed. Surface magnetic states were measured by a three-axis giant magnetoresistant (GMR) sensor and were compared with strain field (digital image correlation) and optical topography measurements. It is demonstrated that the stray fields do not solely form due to magnetoelastic effects. Instead, inhomogeneous plastic deformation causes topography, which is one of the main origins for the magnetic stray field formation. Additionally, if not considered, topography may falsify the magnetic signals due to variable lift-off values. The correlation of magnetic vector components with mechanical tensors, particularly for multiaxial stress/strain states and inhomogeneous elastic-plastic deformations remains an issue.

This research aims to explore magnetomechanical effect as a nondestructive method to monitor the failure process of steel structural elements subjected to compressive loadings. Experiments on steel tubular joints were carried out to study the relationship between the applied load and the magnetomechanical field. Results show that the mechanical response and the magnetomechanical response demonstrate similar behavior to the applied load in the whole loading progress. At the critical load of buckling, the load-magnetic field curve has a bifurcation point corresponding to the traditional bifurcation of load-displacement curve. This research demonstrates that the stress-induced magnetic filed can be utilized as an important indicator of impending failure in steel structural elements. [ABSTRACT FROM AUTHOR]

Abstract: The PZT/Insulator/CoFe nanometer multilayer has been proposed for applications of the spin-dependent devices in this paper. With the strains as a response of PZT layer to an applied electric field in the structure, the magnetization in CoFe layer can be significantly altered, leading to a significance change in magnetoresistance. Our numerical results have demonstrated that the magnetization states in CoFe layer can be tuned by an electric field without a magnetic field being present. [Copyright &y& Elsevier]

In order to propel the development of metal magnetic memory (MMM) technique in fatigue damage detection, a modified Jiles–Atherton (J–A) model is constructed to describe MMM mechanism in elastic stress stage. The MMM phenomenon is discussed from the view of energy minimum theory and equivalent magnetic field theory, the modified J–A model is constructed based on the energy balance in the process of magnetisation and the idea of J–A model, and the new model is used to simulate magnetomechanical effect by Matlab and compare with experimental results. It is shown that the forming process of MMM field is cyclic magnetisation in the range of equivalent magnetic field and the MMM field moves irreversibly towards a local equilibrium state . is the intermediate state with some pinning before M reaches the anhysteretic magnetisation state . The curve is a loop around the curve, and it changes with , H and the type of stress cycle. The modified J–A model that is suited for MMM detection is constructed by replacing in J–A model with and changing some parameters, and it can describe magnetisation features in tension, release processes better and explain the changes in the sign of that have been observed in experiments more reasonably. The modified J–A model can simulate the process of MMM field to become steady and the MMM field variation at fatigue process theoretically by changing model parameters, which is confirmed by experimental results. The results of theoretical research, simulation analysis and experiment verification all indicate that the modified J–A model can be used to describe MMM mechanism in elastic stress stage and analyse MMM field changes at fatigue process. [ABSTRACT FROM AUTHOR]

In order to propel the development of metal magnetic memory (MMM) technique in fatigue damage detection, the Jiles-Atherton model (J-A model) was modified to describe MMM mechanism in elastic stress stage. A series of rotating bending fatigue experiments were conducted to study the stress-magnetization relationship and verify the correctness of modified J-A model. In MMM detection, the magnetization of material irreversibly approaches to the local equilibrium state M instead of global equilibrium state M under cyclic stress, and the M− σ curves are loops around the M− σ curve. The modified J-A model is constructed by replacing M in J-A model with M, and it can describe the magnetomechanical effect well at low external magnetic field. In the rotating bending fatigue experiments, the MMM field distribution in normal direction around cylinder specimen is similar to the stress distribution, and the calculation result of model coincides with experiment result after some necessary modifications. The MMM field variation with time at a certain point in fatigue process is divided into three stages with the variation of stable stress-stain hysteresis loop, and the calculation results of model can explain not only the three stages of MMM field changes, but also the different change laws when the applied magnetic field and initial magnetic field are different. The MMM field distribution in normal direction along specimen axis reflects stress concentration effect at artificial defect, and the magnetic signal fluctuates around the defect at late fatigue stage. The calculation results coincide with the initial MMM principle and can explain signal fluctuates around the defect. The modified J-A model can explain experiment results well, and it is fit for MMM field characterization. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, domain rotations in Tb0.3Dy0.7Fe2 alloy under a compressive stress applied along various crystallographic axes alone have been investigated on the basis of 3D Stoner–Wohlfarth model by following the conventional free energy minimization procedure. The dependence of both the domain rotations and the strains caused by the compressive stress on the stress directions has been revealed. And it has been found that the anisotropic magnetomechanical effect arises from the dependence of the stress induced anisotropy on the stress direction. This study is very helpful for the better understanding of magnetic behavior of magnetostrictive materials under both stress and field. [Copyright &y& Elsevier]

In this work we present a non-destructive technique to detect the magnetization changes due to mechanical stress produced in steel notched plates under tensile loads. The measurements have been carried out using, separately, a magnetic field probe based on HTS dc SQUID and a flux-gate gradiometer probe. The aim of this work is to demonstrate that it is possible to localize the dislocation density change in the samples and to correlate it with the change of magnetization using a contact-less and non-invasive technique. [ABSTRACT FROM AUTHOR]

Abstract: Metal magnetic memory technique has provided a new arena for assessing stress status, especially for detecting early damage in ferromagnetic materials. To investigate the magnetomechanical effect of metal magnetic memory phenomenon, the rotary bending fatigue experiments under different stress levels were conducted. The normal components of magnetic field intensities induced by cyclic bending stresses on the surfaces of 45-steel specimens were measured throughout the fatigue process. The results show that surface magnetic fields generated contains reversible and irreversible process prior to failure, while there is a substantial increase just before fracture. Possible reasons for the variations of magnetic fields and corresponding signal characteristics to identify damage zones were discussed. [Copyright &y& Elsevier]

Abstract: The relationship between the input stress and the output flux density of giant magnetostrictive devices exhibits hysteretic nonlinearity and magnetoelastic coupling inherent to giant magnetostrictive material (GMM). To design and use these devices, it is necessary to establish an accurate model. In this paper, a magnetomechanical hysteresis model of a giant magnetostrictive device for magnetic force control is established based on the Jiles–Atherton model and the theory of magnetomechanical effects and the magnetic force model. A hybrid genetic algorithm is used to estimate the optimal parameters of the proposed model. Comparisons between the calculated and experimental results show that the proposed model can better describe magnetomechanical hysteresis behaviors of the magnetization, flux density and magnetic force of the device under a varying compressive stress and a constant bias magnetic field. The model can also predict the magnetoelastic coupling nonlinearity of the device, i.e. the effect of the bias magnetic field on the output performance of the device. Therefore, the proposed model has important significance for design and analysis of magnetostrictive devices. [Copyright &y& Elsevier]

Abstract: Two kinds of magnetic minor hysteresis loops were simultaneously measured in a low-carbon steel sample under uniaxial tensile stress by using a magnetic probe. For the minor loops measured by the Hall sensor and direct pickup coil, the coercivity H C and hysteresis loss W H showed a sudden increase at an applied field H a above 3kA/m due to the stray flux. As to the other minor loops derived from the calculated H a and indirect pickup coil, no sudden changes in H C and W H took place, and the curves of H C or W H vs applied stress almost paralleled with each other with H a above 2kA/m. H C and W H of these two minor loops obtained at suitable H a showed similar dependences on the applied stress in both elastic and plastic regions. The clear relationship between magnetic properties and external stress is quite applicable in NDE. [Copyright &y& Elsevier]

A hypothesis is presented to explain the mechanism by which externally applied stresses can affect the magnetic properties of ferromagnetic materials. Experiments have revealed coincident points in the second and fourth quadrants on stressed hysteresis loops of mild steel. The results are presented along with an explanation of this effect. An atomic level theory of the origins of the magnetomechanical effect is introduced whereby spin–spin and spin–orbit coupling interact with magnetic moments to alter the magnetocrystalline anisotropy and exchange energies. [Copyright &y& Elsevier]

• Elastic tensile stress on the steel mitigates the stratification of the rust layer. • The stratification involves segregation of Fe 3 O 4 /γ-Fe 2 O 3 in the inner sublayer. • Elastic stress reduces the magnetic attraction between Fe 3 O 4 /γ-Fe 2 O 3 and the steel through magnetomechanical effect. • A stress level up to 200 MPa completely regresses the magnetization of the steel. Effect of elastic stress on the rust layer of S450EW weathering steel formed in salt-spray was studied through electrochemical methods and characterisations on rust layers. Results show that stratification of the rust layer is mitigated with stress level enhanced on the steel. The stratification involves the magnetic Fe 3 O 4 /γ-Fe 2 O 3 phase(s), which tends to segregate in the inner sublayer. The segregation was reduced by stress through a mechanism associated with the magnetomechanical effect. The magnetisation of the steel matrix can be completely regressed by stress up to 200 MPa. Thereby, the magnetic attraction between Fe 3 O 4 /γ-Fe 2 O 3 and the matrix can be reduced considerably. [ABSTRACT FROM AUTHOR]

Abstract: We report a novel frequency multiplier based on the magnetoelectric (ME) effect in a simple multiferroic laminate, made up of an amorphous FeBSiC magnetic layer bonded onto a Pb(Zr,Ti)O3 plate wrapped with a coil. By applying an input signal with a frequency f to the coil, an output signal with 2f can be generated from the PZT plate due to the ME coupling. This ME laminate-based device can be operated in a broad frequency range and switched by a low bias magnetic field, offering potential opportunities for frequency multipliers in electrical applications. [ABSTRACT FROM AUTHOR]

• The energy theory and the equivalent field method are introduced. • The pinning effect caused by plastic deformation is added to the present model. • The prediction accuracy of permeability is evidently improved for the compression. • The model can be degenerated to the previous magneto-elastic model. • A new magneto-elastoplastic coupling model was proposed. A new magneto-elastoplastic coupling model for ferromagnetic materials is proposed using the equivalent field method. In the proposed model, the components of the equivalent field due to the applied magnetic field, applied stress, and plastic deformation are considered based on the energy theory. Through detailed comparison with the existing models, the proposed model in this paper can more accurately describe the basic nonlinear change of magnetostrictive strain and magnetization under the applied stress and magnetic field revealed by existing experiments. In addition, the effects of applied stress, magnetic field and plastic deformation on the magnetostriction and magnetization of ferromagnetic materials are analyzed based on the proposed theory. In conclusion, the proposed model can more accurately describe the effect of stress on the magentostrictive strain and magnetization, the effects of the applied stress and magnetic field on the magnetic permeability, and the effect of plastic deformation on magnetomechanical characteristics. [ABSTRACT FROM AUTHOR]

• The large Widemann effect of several hundred ″/cm is measured in a soft magnetoactive elastomer tube. • The hysteresis of the twist angle is observed with respect to the circumferential magnetic field. • The remanent twist angle grows with the increasing longitudinal magnetic field. Large twists of a soft tube (hollow cylinder) in helical magnetic fields are presented for the first time. Such a phenomenon is usually denoted as the Wiedemann effect. The tube is fabricated from a soft magnetoactive elastomer material with the shear modulus of about 56 kPa. The composite material comprises 80 mass% of micrometer-sized iron particles embedded into a polydimethylsiloxane matrix. The circular magnetic field is generated by an electric current in a straight wire passing through the inner hole of the tube. The maximum value of approximately 350″/cm is observed in a longitudinal magnetic field of a few kA/m overlapped with a circumferential magnetic field of about 1.4 kA/m on the surface of the inner hole. A pronounced hysteresis in the dependence of the Wiedemann effect on the circular magnetic field is found. The ways to enhance the Wiedemann twist in magnetoactive elastomers are discussed. The observed large effect is promising for application in magnetic-field controlled torsional actuators, in particular for soft robotics. [ABSTRACT FROM AUTHOR]

Elongations of magnetoactive elastomers (MAEs) under ascending–descending uniform magnetic fields were studied experimentally using a laboratory apparatus specifically designed to measure large extensional strains (up to 20%) in compliant MAEs. In the literature, such a phenomenon is usually denoted as giant magnetostriction. The synthesized cylindrical MAE samples were based on polydimethylsiloxane matrices filled with micrometer-sized particles of carbonyl iron. The impact of both the macroscopic shape factor of the samples and their magneto-mechanical characteristics were evaluated. For this purpose, the aspect ratio of the MAE cylindrical samples, the concentration of magnetic particles in MAEs and the effective shear modulus were systematically varied. It was shown that the magnetically induced elongation of MAE cylinders in the maximum magnetic field of about 400 kA/m, applied along the cylinder axis, grew with the increasing aspect ratio. The effect of the sample composition is discussed in terms of magnetic filler rearrangements in magnetic fields and the observed experimental tendencies are rationalized by simple theoretical estimates. The obtained results can be used for the design of new smart materials with magnetic-field-controlled deformation properties, e.g., for soft robotics. [ABSTRACT FROM AUTHOR]

• The magneto-elastoplastic multi-field coupling phenomena is studied. • The experimental progress on magnetic flux leakage signal is introduced. • The new theoretical model explains the magneto-elastoplastic coupling effect. • The magnetic dipole theory explains the nonlinear signal of broken specimen. This paper introduces an experimental progress of the magneto-elastoplastic coupling phenomenon on magnetic flux leakage signal for ferromagnetic materials. The magnetic flux leakage signal on the surface of medium carbon steel was measured under the combined action of elastic load and plastic deformation. Based on the experimental results, the influences of elastic load and plastic deformation on the magnetic flux leakage signal and their coupling effects were analyzed. A theoretical mechanism of experimental phenomena was explained by the magneto-elastoplastic coupling model and magnetic charge model. The results show that the magnetic flux leakage signal increases with the increase of the elastic load, and the magnetic flux leakage signal increases first and then decreases with the increase of plastic deformation. As the elastic load increases, the effect of plastic deformation on the magnetic flux leakage signal gradually increases. The work in this paper provides a vigorous support for the safety evaluation of engineering structures caused by the combination of plastic deformation and residual stress through magnetic flux leakage signal. [ABSTRACT FROM AUTHOR]

Bone tissue repair strategies are gaining increasing relevance due to the growing incidence of bone disorders worldwide. Biochemical stimulation is the most commonly used strategy for cell regeneration, while the application of physical cues, including magnetic, mechanical, or electrical fields, is a promising, however, scarcely investigated field. This work reports on novel magnetoactive three-dimensional (3D) porous scaffolds suitable for effective proliferation of osteoblasts in a biomimetic microenvironment. This physically active microenvironment is developed through the bone-mimicking structure of the scaffold combined with the physical stimuli provided by a magnetic custom-made bioreactor on a magnetoresponsive scaffold. Scaffolds are obtained through the development of nanocomposites comprised of a piezoelectric polymer, poly(vinylidene fluoride) (PVDF), and magnetostrictive particles of CoFe 2 O 4 , using a solvent casting method guided by the overlapping of nylon template structures with three different fiber diameter sizes (60, 80, and 120 μm), thus generating 3D scaffolds with different pore sizes. The magnetoactive composites show a structure very similar to trabecular bone with pore sizes that range from 5 to 20 μm, owing to the inherent process of crystallization of PVDF with the nanoparticles (NPs), interconnected with bigger pores, formed after removing the nylon templates. It is found that the materials crystallize in the electroactive β-phase of PVDF and promote the proliferation of preosteoblasts through the application of magnetic stimuli. This phenomenon is attributed to both local magnetomechanical and magnetoelectric response of the scaffolds, which induce a proper cellular mechano- and electro-transduction process.

Magnetomechanical and magnetostriction measurements were performed on a series of plain carbon steels, with carbon contents ranging from 0.1 to 0.9 wt.%. The microstructures in all specimens were similar, being a mixture of ferrite and pearlite, with the pearlite volume fraction increasing with increasing carbon. The magnetomechanical effect was found to vary with carbon content. Specifically, the change in magnetization with stress was proportional to the remanent magnetization for a given carbon level. Also, the sign of the magnetization change upon removal of compressive stress reversed at 0.6 wt.% carbon. The results were explained by the increased number of domain wall pinning sites produced by the increase in carbon content. [ABSTRACT FROM PUBLISHER]

It is widely accepted that the magnetic state of a ferromagnetic material may be irreversibly altered by mechanical loading due to magnetoelastic effects. A novel standardized nondestructive testing (NDT) technique uses weak magnetic stray fields, which are assumed to arise from inhomogeneous deformation, for structural health monitoring (i.e., for detection and assessment of damage). However, the mechanical and microstructural complexity of damage has hitherto only been insufficiently considered. The aim of this study is to discuss the phenomenon of inhomogeneous "self-magnetization" of a polycrystalline ferromagnetic material under inhomogeneous deformation experimentally and with stronger material-mechanical focus. To this end, notched specimens were elastically and plastically deformed. Surface magnetic states were measured by a three-axis giant magnetoresistant (GMR) sensor and were compared with strain field (digital image correlation) and optical topography measurements. It is demonstrated that the stray fields do not solely form due to magnetoelastic effects. Instead, inhomogeneous plastic deformation causes topography, which is one of the main origins for the magnetic stray field formation. Additionally, if not considered, topography may falsify the magnetic signals due to variable lift-off values. The correlation of magnetic vector components with mechanical tensors, particularly for multiaxial stress/strain states and inhomogeneous elastic-plastic deformations remains an issue. [ABSTRACT FROM AUTHOR]