Magnetic Stress Research Articles

Comparison of dual-bolus versus dual-sequence techniques for determining myocardial blood flow and myocardial perfusion reserve by cardiac magnetic resonance stress perfusion: From the Automated Quantitative analysis of myocardial perfusion cardiac Magnetic Resonance Consortium

BackgroundQuantitative stress cardiac magnetic resonance (CMR) can be performed using the dual sequence (DS) technique or dual bolus (DB) method. It is unknown if DS and DB produce similar results for myocardial blood flow (MBF) and myocardial perfusion reserve (MPR). The study objective is to investigate if there are any differences between DB and DS derived MBF and MPR. MethodsRetrospective observational study with 168 patients underwent stress CMR. Dual bolus and dual sequence methods were simultaneously performed on each patient on the same day. Global and segmental stress MBF and rest MBF values were collected. ResultsUsing Bland-Altman analysis, segmental and global stress MBF values were higher in DB than DS (0.22 + 0.60ml/g/min, p<0.001 and 0.20 + 0.48ml/g/min, p=0.005 respectively) with strong correlation (r = 0.81, p < 0.001 for segmental and r = 0.82, p < 0.001 for global). In rest MBF, segmental and global DB values were higher than by DS (0.15 + 0.51ml/g/min, p<0.001 and 0.14 + 0.36ml/g/min, p=0.011 respectively) with strong correlation (r = 0.81, p < 0.001 and r = 0.77, p < 0.001). Mean difference between MPR by DB and DS was -0.02 + 0.68ml/g/min (p=0.758) for segmental values and -0.01 + 0.49ml/g/min (p=0.773) for global values. MPR values correlated strongly as well in both segmental and global, both (r = 0.74, p < 0.001) and (r = 0.75, p < 0.001) respectively. ConclusionsThere is very good correlation between DB and DS derived MBF and MPR values. However, there are significant differences between DB and DS derived global stress and rest MBF. Whilst MPR values did not show statistically significant differences between DB and DS methods.

An improved stress-dependent magnetostriction model of silicon steel based on simplified multi-scale and Jiles–Atherton theory

Due to the magnetic domain movement and energy change under magnetic field and stress applied, the macroscopic magnetic properties and magnetostriction properties of non-oriented (NO) silicon steel are influenced. To present this effect of the magnetic domains’ motion mechanism, a stress-dependent magnetostriction must be modeled. This paper proposes an improved stress-dependent magnetostriction model (I-SDM model) for NO silicon steel based on a simplified multi-scale model. Firstly, the stress-dependent expression of the anhysteretic magnetization, obtained by assuming a six-domain structure and considering the volume fraction of magnetic domain energy, is introduced into the inverse Jiles–Atherton (JA) model. In this way, the stress-dependent hysteresis model is constructed. Then, coupling with the improved quadratic domain rotation model that considers pinning effects, the I-SDM model for NO silicon steel is built. Finally, with the parameters obtained from experimental results, the proposed model under varying stresses is simulated and compared with other models. It shows that the proposed model has the highest simulated accuracy for both λ-H loop and λ-B loop with stress applied.

Study on the Strengthening Effect of Excitation Magnetic Field on Stress-Induced Magnetic Signal of X80 Steels

Weak magnetic excitation stress detection has good engineering application prospects in the pipeline non-destructive testing field. To obtain the quantitative variation law between the excited stress-induced magnetic signal and the axial stress value of X80 steel, an axial tensile experimental test of X80 steel under weak magnetic excitation is conducted in this paper. The enhancing effect of the excitation magnetic field on the sensitivity of stress-induced magnetic signals has been quantitatively analyzed. The results indicate that the value of normal magnetic flux density B z increases by 24 times when the excitation magnetic field reaches 600 A/m. Within the scope of 400 A/m to 700 A/m, the excitation magnetic field of 400 A/m has the best excitation effect on X80 steel.

Consideration of tensile stress in the ODF-based approach for modelling the first magnetization curves of Grain-Oriented Electrical Steels

Grain-oriented electrical steels (GOES) are extensively utilized in power transformers to enhance energy efficiency and reduce their size and weight. GOES are characterized by their strong magnetic anisotropy, leading to distinct magnetic characteristics (behavior law and iron losses) according to the direction and the intensity of the applied field with respect to the rolling direction (RD). The Orientation Distribution Function (ODF) based approach is a convenient method for describing the anisotropy of the GOES behavior law owing to its ease of identification and implementation. However, it exhibits a significant oscillation issue at low magnetic fields. To address this issue, a high-order ODF-based method has been proposed in the literature. In this article, the ODF-based model, initially stress-free, is extended to include the effects of mechanical tensile stress on the first magnetization curves of a conventional GOES. An ODF-based model considering both magnetic anisotropy and mechanical tensile stress is then proposed. The results are discussed and compared with experimental data.

Bending-torsional coupling vibration characteristics of asynchronous motorized spindle considering electromechanical coupling and multi-excitation effect

For the asynchronous motorized spindle directly driven by the induction motor, the load-dependent slip ratio determines that its transient characteristics are sensitive to load. For the accurate evaluation of transient characteristics, it is necessary to deeply analyze the bending-torsional coupling vibration characteristics of the asynchronous motorized spindle with the non-ideal energy source. In this work, starting from energy conservation and clarifying the multi-physical field coupling mechanism, the bending-torsional coupling dynamic model is developed. Considering the speed fluctuation, the mass eccentricity excitation is deconstructed to explore its contribution to the coupling vibration. From the load-displacement relationship, the unbalanced excitation experienced by the journal from the bearing is modeled, considering the friction. According to the T-type equivalent circuit and mechanical characteristics of the induction motor, the electromagnetic torque considering power conservation is obtained. Furthermore, combined with Maxwell's stress formula, the electromagnetic excitation from electromagnetic torque and magnetic pull is obtained, considering the tangential and normal magnetic stress. Based on the projection and synthesis of forces, the semi-empirical mechanical cutting force model is employed to calculate the milling load. And a numerical algorithm for the fast acquisition of state-dependent delay is proposed. In particular, to reasonably characterize the energy characteristics in the system, the influence of structural vibration as an energy sink on the multi-physical field composed of mechanical, electromagnetic, and thermal fields is explored from the energy conservation. The proposed model was validated experimentally. The effects of electrical and mechanical parameters on the response are numerically discussed.

Magnetostrictive strain monitoring in Non-Oriented Si-Fe steels using a SAW resonator sensor

The aim of this study is to introduce a new technique for characterizing the magnetostrictive behavior of non-oriented ferromagnetic steel sheets using miniaturized wireless surface acoustic wave sensors (SAW). Unlike conventional optical and electromechanical techniques, this type of sensor offers advantages such as on-board capability, high-temperature resistance (up to 400 °C), and the ability to be connected remotely. The final objective is to monitor magnetic stresses in electrical machines, aligning with the requirements of Industry 4.0 and predictive maintenance. The focus of the present study is the measurement of magnetostriction in ferromagnetic steel sheets, employing a wireless surface acoustic wave resonator operating within the 433 MHz ISM band, under various mechanical fixation configurations. To ensure the accuracy and reliability of SAW measurements, a commercial strain gauge is employed as a reference sensor. Measurements are conducted at different excitation frequencies to explore the phenomenon comprehensively.

Multi-field synergistic regulation enhanced multicaloric effect in all-d-metal Ni37Co13Mn35Ti15 alloy

Solid-state cooling technology has attracted great attention to replace traditional vapor-compression cooling technology due to its advantages of environmentally friendly, energy conservation, and high efficiency. However, the cooling performance of a single field (magnetic, stress or electric field) induced caloric effect is still insufficient. Recently, a larger multicaloric effect is expected to be achieved by the synergistic regulation of multiple fields. In this study, we choose all-d-metal Ni37Co13Mn35Ti15 alloy with magnetostructural phase transition and systematically study the multicaloric effect through the synergistic regulation of external stress and magnetic fields based on our homemade multicaloric effect testing device. The magnetic field and stress field play opposite effects on the phase transition, thus contributing contradictory caloric effect to multicaloric effect. By loading stress without magnetic field while unloading stress under magnetic field of 1.1 T, the stress hysteresis and energy hysteresis loss can be reduced by up to 45.2% and 54.8% in comparison with those obtained from a non-ideal regulation protocol. Moreover, the maximum adiabatic temperature change |ΔTad| during unloading increases by 24% from 6.3 K to 7.8 K with the application of magnetic field (1.1 T), suggesting a larger multicaloric effect than that of a single elastocaloric effect. These results prove that multi-field synergistic regulation is an effective means to enhance the multicaloric effect and reduce the hysteresis and energy loss of materials with the magnetostructural transition.

Numerical modelling and analysis of current induced stresses in REBCO coil stacks

This study reports the effect of the radial, axial, and hoop electromagnetic stresses caused by the large current density and the self-field (screening current-induced magnetic field) on REBCO superconducting coil stacks. A two-dimensional numerical model is used to study the stress distribution of a superconducting coil stack under current. The electromagnetically homogenized coil stack is assumed to be composed of four equally spaced coils with rectangular cross-section. Initially, the verification of the model is done by comparing the analytical calculations (which were in good agreement) of stress distributions of a superconducting slab exposed to a variable magnetic field and in a superconducting strip exposed to a variable current. Then, the two-dimensional model is used to obtain the components of stress that occurred in the coil stack under sinusoidal varying currents. The stress component distributions are calculated at different time intervals, currents, frequencies, and coil distances. Besides, one-dimensional stress distributions are plotted to show how the stress distributions change while the current increases. The upper and lower coils have much higher magnetic stress than the inner coils. Results obtained from the one-dimensional stress distribution calculations show that the stress occurring in the radial direction is lower than the stress in the z-direction in the coil stack. The stress distributions do not show a significant change as the frequency of the applied current changes. The stresses in both the radial and axial directions decrease as the distance between coils increases. All results are presented, and the possible reasons are explained.

Spatial and temporal crack initiation prediction in steels based on residual stress tensor distribution monitoring

We have developed a method and the corresponding instruments, able to provide the spatial and temporal determination of crack initiation in ferromagnetic steels and their welds. The method is based on the monitoring of the differential magnetic permeability µr along the length of the steel, since a sigmoid monotonical dependence of µr on residual stresses has been determined in the past. Thus, the magnetic stress calibration (MASC) curves can inform on the localized residual stresses. Therefore, the temporal stress monitoring at different areas of interest can inform about the status of residual stresses. Then, the tendency of the residual stress value can inform about reaching the positive (tensile) or negative (compressive) yield point of the steel. As an example, a quasi-parabolic temporal dependence of µr offers the tendency to determine the time, or the time window, required to reach yield point. This way, the temporal prediction of the crack initiation is provided for the given point in space, since reaching the yield point results in crack initiation.

Kinetic-scale Topological Structures Associated with Energy Dissipation in the Turbulent Reconnection Outflow

Assisted by the Magnetospheric Multiscale mission capturing unprecedented high-resolution data in the terrestrial magnetotail, we apply a local streamline-topology classification methodology to investigate the categorization of the magnetic field topological structures at kinetic scales in the turbulent reconnection outflow. It is found that strong correlations exist between the straining and rotational part of the velocity gradient tensor as well as the magnetic field gradient tensor. Strong energy dissipation prefers to occur at regions with high magnetic stress or current density, which is contributed mainly by O-type topologies. These results indicate that the kinetic structures with O-type topology play a more important role in energy dissipation in turbulent reconnection outflow.

Fluctuation of Magnetic Field in Magnetic Nano-Particles Thermometer

In this study, some important factors have been identified for the fluctuation of the magnetic field over time, which provides a basis for improving the temperature measurement accuracy and long-term stability of the magnetic nanoparticles thermometer (MNPT). We improved the mathematical model between the relative error of the magnetic induction intensity and the temperature measurement error of MNPT. The simulation founded that when the relative error of the magnetic induction intensity is kept within the range of &lt;0.01%, the temperature measurement error is less than 0.1 K. Then, the multi-physics (magnetic field, temperature field, and thermal stress field) coupling relationship in the Helmholtz coil is established. During the coupling process, the temperature field of the Helmholtz coil affects the resistance of coil wire, and its thermal stress field is affected by the temperature field, which also changes the coil radius. After the temperature field and thermal stress field change, the magnetic field fluctuates immediately. Further simulation found that the problem of coil temperature rise becomes more serious as the size of the Helmholtz coil increases. The method of forced air cooling can make the fluctuation of the large Helmholtz coil magnetic field &lt; 0.01%, and improve the measurement accuracy of MNPT.

Experimental study on wear performance of before and after magnetic treatment of hot-pressing sintering iron-based diamond bit matrix

The properties of diamond bits sintered by hot-pressed with different metal matrix materials are different, among which cobalt-based bits are popular because of their good comprehensive properties, but the price of cobalt-based bits is higher. In order to improve the cost performance, replacing cobalt (Co) with iron (Fe) is one of the common methods to improve the cost performance of diamond bits. However, the replacement of Co by Fe has adverse effects on the wear performance of diamond bits, thus affecting the working life of diamond bits, and further affecting the drilling efficiency. Therefore, it is of great significance to study the iron-based matrix modification treatment method and friction and wear performance of iron-based hot-pressed diamond bit to reduce the drilling cost and improve the drilling efficiency. The matrix material of iron-based hot-pressed diamond bit was magnetically treated by magnetic treatment equipment, and the influence of magnetic treatment parameters on the wear performance of iron-based hot-pressed diamond bit matrix was studied. Through the analysis of the worn surface morphology of the bit matrix, the influence and law of magnetic treatment on the wear resistance of the iron-based bit matrix were obtained. The results show that magnetostriction, magnetic field stress, and other factors can improve the structure of the bit matrix, and then affect the overall performance of the bit matrix. After magnetic treatment, the hardness of the bit matrix increases, the roughness decreases, the friction coefficient decreases, and the wear resistance increases.

Yield Stress Impact on Magnetohydrodynamic Jeffery Hybrid Nanofluid Flow Over a Moving Porous Surface: Buongiorno’s Model

The main goal of the present study is to explore the flow of Jeffrey hybrid nanofluid crossing through a moving porous surface with the existance of magnetic field, heat sink/source, yield stress and chemical reaction impact. Nusselt number is characterized by the process of thermal radiation. The partial equations are governed during the moved coordinate’s porous regime that is depicting the flow for Buongiorno’s model. Employing similarity transformations, the obtained equations were turned into non-linear ordinary differential equations. The controlled equations were solved by RKF45 via shooting technique. The focus is in examining physical characteristics such as heat flux at the wall, temperature distribution, velocity of flow, and surface friction for a variety of related parameters. The analysis explained that higher permeability and parameters of yield stress, generation of heat and magnetic field enhance distribution of temperature and slow down the heat transfer. The mass transport is upsurged with increasing chemical reaction and heat source. The model is prepared as an application in processes of thermal engineering.

Thermal-magnetic performance analysis for smart fluid dampers

Abstract Over the years, the Italian Government has taken significant strides in promoting road safety awareness among the students in high schools to create an awareness of prevention and a consciousness of road safety in the student population. In this context, an agreement was signed between the DICEAM Department of the “Mediterranea” University of Reggio Calabria (Italy) and the “Euclide” Higher Education Institute Bova Marina (Italy) to combine road safety with research science in the Science, Technology, Engineering, and Mathematics (STEM) area. With the primary aim of “knowing in order to act”, the students focused on the multi-physics design of magnetorheological fluid dampers as high-performance devices (simple to design and requiring reduced maintenance) for vehicle suspensions, especially class B vehicles. By combining road safety considerations with multi-physics scientific disciplines, the project seeks to emphasize the importance of prevention and knowledge-based action. The study explores the use of magnetorheological fluid dampers, powered by electric current and magnetic induction distribution with thermal loads, to provide appropriate yield stress for developing damping action with repercussions on the quality of road safety. The paper delves into the basic principles of FEM (Finite Element Method) techniques for analyzing an MR damper from both magnetostatic (the main cause generating the damping effect) and thermal perspectives (thermal effects are strongly influenced by environmental conditions). The analysis of an asymmetrical device, where the damping action relies on an MR fluid strip, reveals the significant influence of magnetic and thermal stresses on the magnetization of individual particles and the overall viscosity of the MR fluid.

Effect of the Rotation and Inclined Magnetic Field on Peristaltic Slip Flow of a Bingham Fluid in Asymmetric Channel and Porous medium

This essay aims to describe the peristaltic behavior of Bingham's fluid in an asymmetric channel and porous material. The liquid is thought to flow in a porous media and be susceptible to a powerfully inclined magnetic field. The long wavelength dependency and low Reynolds number result in a major simplification of the nonlinear equations. The pressure gradient, pressure rise per wavelength, axial velocity, spin velocity, volume flow rate, and tilted magnetic number are all given specific attention. The findings reveal that rotation, density, permeability, coupling diversity, and non-dimensional wave amplitude all play significant roles in the phenomenon. With rising slip coefficient values and falling magnetic field strengths, permeability, and yield stress coefficients the trapped bolus grows in size

Magnetic Stress-Driven Metal-Insulator Transition in Strongly Correlated Antiferromagnetic CrN.

Traditionally, the Coulomb repulsion or Peierls instability causes the metal-insulator phase transitions in strongly correlated quantum materials. In comparison, magnetic stress is predicted to drive the metal-insulator transition in materials exhibiting strong spin-lattice coupling. However, this mechanism lacks experimental validation and an in-depth understanding. Here we demonstrate the existence of the magnetic stress-driven metal-insulator transition in an archetypal material, chromium nitride. Structural, magnetic, electronic transport characterization, and first-principles modeling analysis show that the phase transition temperature in CrN is directly proportional to the strain-controlled anisotropic magnetic stress. The compressive strain increases the magnetic stress, leading to the much-coveted room-temperature transition. In contrast, tensile strain and the inclusion of nonmagnetic cations weaken the magnetic stress and reduce the transition temperature. This discovery of a new physical origin of metal-insulator phase transition that unifies spin, charge, and lattice degrees of freedom in correlated materials marks a new paradigm and could lead to novel device functionalities.

The Formation of Star-forming Disks in the TNG50 Simulation

We investigate the disk formation process in the TNG50 simulation, examining the profiles of SFR surface density (ΣSFR), gas inflow and outflow, and the evolution of the angular momentum of inflowing gas particles. The TNG50 galaxies tend to have larger star-forming disks, and they also show larger deviations from exponential profiles in ΣSFR when compared to real galaxies in the Mapping Nearby Galaxies at APO survey. The stellar surface density of TNG50 galaxies show good exponential profiles, which is found to be the result of strong radial migration of stars over time. However, this strong radial migration of stars in the simulation produces flatter age profiles in TNG50 disks compared to observed galaxies. The star formation in the simulated galaxies is sustained by a net gas inflow, and this gas inflow is the primary driver for the cosmic evolution of star formation, as expected from simple gas-regulator models of galaxies. There is no evidence for any significant loss of angular momentum for the gas particles after they are accreted on to the galaxy, which may account for the large disk sizes in the TNG50 simulation. Adding viscous processes to the disks, such as the magnetic stresses from magnetorotational instability proposed by Wang & Lilly, will likely reduce the sizes of the simulated disks and the tension with the sizes of real galaxies, and this may produce more realistic exponential profiles.

Frictional contribution in nanomagnetic particles substituted magnetorheological fluid

A series of Fe flake-based MR fluids were prepared using a ferrofluid as a dispersion medium. The concentration of micron-size particles was kept constant, and the nanoparticle concentration was varied. The MR fluids were characterised structurally and rheologically. The experimental results were fitted with various models.This paper aims to elucidate how the frictional behaviour of the flakes is modified in the presence of magnetic nanoparticles. The measurements were carried out on fluid flow under different conditions, such as applied magnetic field, shear rate, and stress. The data was analysed using the recent PUP (Pisuwala-Upadhyay-Parekh) rheology model. The results clearly show that the friction between the anisotropic particles decreases with an increase in nanoparticle concentration. The conclusion is further enforced by testing a commercial MRF with spherical particles.

Heterogeneous Dynamics of Sheared Particle-Laden Fluid Interfaces with Janus Particle Doping.

The formation of particle clusters can substantially modify the dynamics and mechanical properties of suspensions in both two and three dimensions. While it has been well established that large network-spanning clusters increase the rigidity of particle systems, it is still unclear how the presence of localized nonpercolating clusters affects the dynamics and mechanical properties of particle suspensions. Here, we introduce self-assembled localized particle clusters at a fluid-fluid interface by mixing a fraction of Janus particles in a monolayer of homogeneous colloids. Each Janus particle binds to a few nearby homogeneous colloids, resulting in numerous small clusters uniformly distributed across the interface. Using a custom magnetic rod interfacial stress rheometer, we apply linear oscillatory shear to the particle-laden fluid interface. By analyzing the local affine deformation of particles from optical microscopy, we show that particles in localized clusters experience substantially lower shear-induced stretching than their neighbors outside clusters. We hypothesize that such heterogeneous dynamics induced by particle clusters increase the effective surface coverage of particles, which in turn enhances the shear moduli of the interface, as confirmed by direct interfacial rheological measurements. Our study illustrates the microscopic dynamics of small clusters in a shear flow and reveals their profound effects on the macroscopic rheology of particle-laden fluid interfaces. Our findings open an avenue for designing interfacial materials with improved mechanical properties via the control of formation of localized particle clusters.

Self-Protection Characteristic Comparison between No-Insulation, Metal-as-Insulation, and Surface-Shunted-Metal-as-Insulation REBCO coils.

The metal tape co-winding or a metal-as-insulation (MI) winding method is an excellent way to improve the mechanical properties and reduce the average current density, thereby decreasing the stress in high-field REBCO magnet without completely losing the benefits of the no-insulation (NI) winding method. However, the MI winding increases the resistance between turns, which is known as characteristic resistance. The increased characteristic resistance can reduce the bypass current during abnormal transition situation, such as quench, which may not be desirable from a magnet protection point of view. To take advantage of both the MI and NI winding, one possible solution to reduce characteristic resistance of the MI winding coils is to add a shunt on top of the winding surface of the coil. We call this method surface-shunted-metal-as-insulation (SSMI). In this presentation, we compare the characteristic resistances and their correlated self-protecting characteristics between NI, MI, and SSMI. We present the test results of single pancake coils which wound using different winding methods (NI, MI, and SSMI) with same winding pressure of 20 N. In particular, we investigated how the SSMI method affects the characteristic resistance.