Improvement of measuring accuracy of magnetic field strength in single sheet testers by using two H coils

The accuracy of the measured magnetic field strength of single sheet testers using an H coil[1-4] is examined by finite element analysis. An improved measuring method which uses two H coils is proposed from this investigation. It is clarified that the best measuring method of magnetic field strength is the improved two H coil method. The validity of the new method is confirmed by experiments. </p

Influence of lamination orientation and stacking on magnetic characteristics of grain-oriented silicon steel laminations

Analytical and experimental investigations have been carried out upon the behaviour of flux in laminations, where the rolling directions of adjacent sheets are reversed. The paper clarifies the mechanism of the greatly different magnetic characteristics between such laminations and usual ones, where the rolling directions of adjacent sheets are coincident.</p

A New Application of Transient Recorder to Magnetic Measurements (Part I: Core Loss Measurement at Very Low Frequencies)

A new method have been developed based upon analogue-to-digital conversion techniques and memories. The method involves the scaling of operating frequency from "real" to "optimum" for the power loss measurement. The advantages of using this techniques are as follows: (1) extreme availability at lower frequency region, (2) high accuracy and high stability, (3) simple measuring procedure, (4) digital indication. This method can be measured the power losses over the frequency range 0.1Hz to 1kHz for magnetic circuit and d.c. to 1kHz in such a purely resistive circuit. We estimate the accuracy of this core loss measuring system within 1.0% over all these frequency range. Using this system, specific core losses of the various grades of silicon iron have been measured in the frequency range 0.1Hz to 200Hz

Axisymmetric Magnetorotational Instability in Viscous Accretion Disks

Axisymmetric magnetorotational instability (MRI) in viscous accretion disks is investigated by linear analysis and two-dimensional nonlinear simulations. The linear growth of the viscous MRI is characterized by the Reynolds number defined as $R_{\rm MRI} \equiv v_A^2/\nu\Omega$, where $v_A$ is the Alfv{\'e}n velocity, $\nu$ is the kinematic viscosity, and $\Omega$ is the angular velocity of the disk. Although the linear growth rate is suppressed considerably as the Reynolds number decreases, the nonlinear behavior is found to be almost independent of $R_{\rm MRI}$. At the nonlinear evolutionary stage, a two-channel flow continues growing and the Maxwell stress increases until the end of calculations even though the Reynolds number is much smaller than unity. A large portion of the injected energy to the system is converted to the magnetic energy. The gain rate of the thermal energy, on the other hand, is found to be much larger than the viscous heating rate. Nonlinear behavior of the MRI in the viscous regime and its difference from that in the highly resistive regime can be explained schematically by using the characteristics of the linear dispersion relation. Applying our results to the case with both the viscosity and resistivity, it is anticipated that the critical value of the Lundquist number $S_{\rm MRI} \equiv v_A^2/\eta\Omega$ for active turbulence depends on the magnetic Prandtl number $S_{{\rm MRI},c} \propto Pm^{1/2}$ in the regime of $Pm \gg 1$ and remains constant when $Pm \ll 1$, where $Pm \equiv S_{\rm MRI}/R_{\rm MRI} = \nu/\eta$ and $\eta$ is the magnetic diffusivity.Comment: Accepted for publication in ApJ -- 18 pages, 9 figures, 1 tabl

Review : Microstructural Control and Functional Enhancement of Light Metal Materials via Metal Additive Manufacturing

Additive manufacturing (AM) has been attracting a great deal of attention in both academia and industry in recent years as a technology that could bring innovation to manufacturing. AM was originally developed as a method specialized in fabricating three-dimensional structures by the additive manner. However, in reality, a huge number of parameters involved in AM has a significant effect on the microstructure and the resulting physicochemical properties of the metallic material. Therefore, in very recent years, metal AM is being recognized as a technology for controlling the microstructure of metals rather than its shape. In addition, AM can even customize the microstructure of each site by applying locally controlled heat energy. The ability to simultaneously control complex shapes and microstructures will add even higher value to light-weight metal materials. This paper describes the potential of metal AM to control material and shape properties that dictates the essential mechanical properties of the product with introducing latest results.Ishimoto Takuya, Nakano Takayoshi. Review : Microstructural Control and Functional Enhancement of Light Metal Materials via Metal Additive Manufacturing. MATERIALS TRANSACTIONS 64, 10 (2023); https://doi.org/10.2320/matertrans.MT-MLA2022007

Control of Anisotropic Crystallographic Texture in Powder Bed Fusion Additive Manufacturing of Metals and Ceramics—A Review

Additive manufacturing (AM) enables the production of complex, net-shape geometries. Additionally, in AM of metal and ceramics, which has received less attention, the microstructure and texture of the product can be arbitrarily controlled by selecting appropriate process parameters, thereby enabling unprecedented superior properties. This paper discusses recent progress pertaining to texture evolution mechanisms and control methods, with an emphasis on selective laser melting. One of the unique characteristics of AM is that the texture can be varied as a function of position within the product by controlling the scan strategy. The transient behavior of the texture and the factor used to control it via the scan strategy are discussed. In addition, the texture evolution behavior of face- and body-centered cubic as well as noncubic materials is discussed. The importance of the crystallographic “multiplicity” of the preferential crystal growth direction is described to understand the evolution behavior of the texture in such materials.Hagihara K., Nakano T.. Control of Anisotropic Crystallographic Texture in Powder Bed Fusion Additive Manufacturing of Metals and Ceramics—A Review. JOM, https://doi.org/10.1007/s11837-021-04966-7

Experimental Studies of Various Factors Affecting Minor Loop Hysteresis Loss

When the distorted flux is induced in a magnetic circuit, the minor loops arise sometimes inside the major hysteresis loop. The area, accordingly the hysteresis loss of the minor loop,is affected by its amplitude and position, by the maximum flux density, by the quality of material, etc.. In this paper, we describe the experimental studies of the factors on the minor loop hysteresis loss. A method of getting the displacement factor of a minor loop which is placed at arbitrary position and has any amplitude is developed from our experimental results. Using this method, the core losses caused by the distorted flux can be calcuLated within the error less than three percent, even if the amplitude of the minor loop becomes near to the amplitude of the major loop

Beta titanium single crystal with bone-like elastic modulus and large crystallographic elastic anisotropy

To develop single crystalline beta titanium implant as new hard tissue replacements for suppressing the stress shielding, we design a Ti-26.6Nb-6.7Al alloy (at. %) single crystal that exhibits large crystallographic elastic anisotropy and low Young's modulus. The anisotropy factor, A, reaches 3.42 that is the highest among all the reported values. The Young's modulus along direction, E100, is only 36 GPa that is similar to the Young's modulus of cortical bone. These results prove our proposed design strategy and provide a new path to design beta titanium single crystal with bone-like elastic modulus for implant to minimize stress shielding.Wang P., Todai M., Nakano T.. Beta titanium single crystal with bone-like elastic modulus and large crystallographic elastic anisotropy. Journal of Alloys and Compounds, 782, 667. https://doi.org/10.1016/j.jallcom.2018.12.236

Development of Co-Cr-Mo-Fe-Mn-W and Co-Cr-Mo-Fe-Mn-W-Ag high-entropy alloys based on Co-Cr-Mo alloys

Co-Cr and Co-Cr-Mo-based alloys are commercially used in the industry especially for high wear resistance and superior chemical and corrosion performance in hostile environments. These alloys were widely recognized as the important metallic biomaterials. Here, the first development of Co-Cr-Mo-Fe-Mn-W and Co-Cr-Mo-Fe-Mn-W-Ag high-entropy alloys (HEAs) based on Co-Cr-Mo metallic biomaterials is reported. Ingots of six-component Co₂.₆Cr₁.₂Mo₀.₂FeMnW₀.₂₇ (Co₄₁.₅Cr₁₉.₁Mo₃.₂Fe₁₆Mn₁₆W₄.₃, at%) HEAs with a minor σ phase and of seven-component Co₄.₂₂₅Cr₁.₉₅Mo₀.₂FeMnW₀.₂Ag₀.₅ (Co₄₆.₆Cr₂₁.₅Mo₂.₂Fe₁₁Mn₁₁W₂.₂Ag₅.₅, at%) and Co₂.₆Cr₁.₂Mo₀.₁FeMnW₀.₁Ag₀.₁₈ (Co₄₂.₁Cr₁₉.₄Mo₁.₆Fe₁₆.₂Mn₁₆.₂W₁.₆Ag₂.₉, at%) HEAs without an · phase were fabricated. The alloy was designed by a taxonomy of HEAs based on the periodic table, a treelike diagram, predicted phase diagrams constructed by Materials Project, and empirical alloy parameters for HEAs. The · phase formation prevented the formation of solid solutions in Co-Cr-Mo-based HEAs without a Ni element. The · phase formation in as-cast ingots was discussed based on the composition dependence and valence electron concentration theory.Nagase T., Todai M., Nakano T. Development of Co-Cr-Mo-Fe-Mn-W and Co-Cr-Mo-Fe-Mn-W-Ag high-entropy alloys based on Co-Cr-Mo alloys. Materials Transactions 61, 567 (2020); https://doi.org/10.2320/matertrans.MT-MK2019002