DEVELOPING A TOOL FOR A QUALITATIVE MEASUREMENT OF PINNING FORCES USING ROTATIONAL MAGNETIZATION EXPERIMENTS

2009 ◽  
Vol 23 (05) ◽  
pp. 711-722
Author(s):  
I. M. OBAIDAT
Keyword(s):  
High Temperature Superconductors ◽  
Magnetization Vector ◽  
Sample Surface ◽  
Rate Of Change ◽  
Magnetic Flux Density ◽  
Zero Field ◽  
Average Strength ◽  
Rotational Angle ◽  
Sample Rotation ◽  
Disk Sample

We have investigated the behavior of vortices in a polycrystalline YBa 2 Cu 3 O 7-δ disk sample using rotational magnetization-vector (RMV) measurements. The measurements were conducted in the field-cooled (FC) and the zero-field cooled (ZFC) states for several values of applied magnetic field parallel to the sample surface at 4.2 K and for various angles of rotation (θ rot ) up to 360°. The total magnetic flux density, B, in the sample at any rotational angle was considered to be composed of two types of vortices: weakly pinned vortices that rotate frictionally in the opposite direction of sample rotation and strongly pinned vortices that rotate rigidly in the same direction of sample rotation. From the rate of change of these two types of vortices and the rate of change of B, we were able to develop a tool to qualitatively describe the average strength of pinning centers in high-temperature superconductors.

scholarly journals Vortex phase diagram and the normal state of cuprates with charge and spin orders

2020 ◽  
Vol 6 (7) ◽  
pp. eaay8946 ◽  
Author(s):  
Zhenzhong Shi ◽  
P. G. Baity ◽  
T. Sasagawa ◽  
Dragana Popović
Keyword(s):  
Phase Diagram ◽  
Normal State ◽  
Ground State ◽  
High Field ◽  
High Temperature Superconductors ◽  
Upper Critical Field ◽  
Energy Scale ◽  
Zero Field ◽  
Vortex Matter ◽  
Nonlinear Transport

The phase diagram of underdoped cuprates in a magnetic field (H) is key to understanding the anomalous normal state of these high-temperature superconductors. However, the upper critical field (Hc2), the extent of superconducting (SC) phase with vortices, and the role of charge orders at high H remain controversial. Here we study stripe-ordered La-214, i.e., cuprates in which charge orders are most pronounced and zero-field SC transition temperatures Tc0 are lowest. This enables us to explore the vortex phases in a previously inaccessible energy scale window. By combining linear and nonlinear transport techniques sensitive to vortex matter, we determine the T − H phase diagram, directly detect Hc2, and reveal novel properties of the high-field ground state. Our results demonstrate that quantum fluctuations and disorder play a key role as T → 0, while the high-field ground state is likely a metal, not an insulator, due to the presence of stripes.

A Modeling of Fe-Ga Magnetostrictive Shunt Damper

2014 ◽  
Author(s):  
JinHyoeng Yoo
Keyword(s):  
Magnetic Flux ◽  
Permanent Magnet ◽  
Cantilever Beam ◽  
Mechanical Energy ◽  
Rate Of Change ◽  
Magnetic Flux Density ◽  
Pickup Coil ◽  
Model Parameters ◽  
Mass Load ◽  
Shunt Circuit

This study presents mechanical energy dissipation with a proof-of-concept prototype magnetostrictive (Fe-Ga alloy, galfenol) based shunt circuit using passive electrical components. Magneto strictive material can harvest electricity out of the structural vibrations based on the Villari effect using permanent magnet and pickup coil configuration. The device in this study consists of a polycrystalline galfenol strip bonded to a brass cantilever beam. Two brass pieces, each containing a permanent magnet, are used to mass load at the end of the beam and to provide a magnetic bias field through the galfenol strip. The voltage induced in an induction coil closely wound around the cantilever beam captures the time rate of change of magnetic flux within the galfenol strip as the beam vibrates. To dissipate the electrical voltage output from the pickup coil and/or to change the phase of eddy current from the magnetic flux density fluctuation, a shunt circuit is attached. The effective mechanical impedance for the magnetostrictive shunt circuit is derived in a model. The effectiveness of a series L-R and L-C shunt circuit is demonstrated theoretically and experimentally. The non-linear model parameters, which include the mechanical-magnetic coupling factors, α and αT, and the permeability of galfenol, β, are extracted from experimental measurement. The shunted magnetostrictive damping model of both resistive and capacitance shunt cases compare well with the experimental results.

scholarly journals Experimental Studies on the Influence of Electrochemical Dimensional Processing on the Surface Fatigue of Rolls in Rolling Machines

2021 ◽  
Vol 346 ◽  
pp. 01035
Author(s):  
Alexander A. Boldyrev ◽  
Alexander I. Boldyrev ◽  
Alla V. Perova ◽  
Anna A. Padurets
Keyword(s):  
Surface Layer ◽  
Metal Layer ◽  
Local Heating ◽  
Experimental Studies ◽  
Sample Surface ◽  
Specific Work ◽  
Sample Rotation ◽  
Surface Fatigue ◽  
Contact Roller ◽  
Dimensional Processing

The state of surface layer in large part determines the performance characteristics of products, especially those operating at high contact loads, and in particular of rolls in rolling machines. As a rule, grinding is the final processing of rolls, but high specific work and high local heating in the cutting area lead to the appearance of a large variety of defects in the surface layer of the machined part. Subsequent electrochemical dimensional processing can significantly reduce their number. This article presents the results of comparative tests for surface fatigue of samples made of alloy steel 9Cr2MoV. The sequence of samples preparation for experimental studies is considered, they underwent a cycle of heat treatment according to a single standard mode, which made it possible to obtain a martensitic structure in the presence of inclusions of small carbides. Then the samples were ground to the height of irregularities Ra = 0.3-0.2 microns. Some of the ground samples were subjected to electrochemical dimensional processing at rational modes, when 0.2 mm thick metal layer was removed per side in the time equal to 0.5 min. The result was practically flaw-free surface with the microroughness height Ra = 0.25-0.18 microns. The sample tests for surface fatigue were carried out on a two-contact roller machine under rolling conditions with relative slip between the sample surface and pressure rollers at the peripheral speed of sample rotation 1.3 times lower than the circumferential speed of pressure roller rotation. The analysis on the contact stress diagram of the samples showed that higher resistance to fatigue fractures is observed in the samples after electrochemical dimensional processing. The number of cycles at which the limit of material contact endurance occurs for these samples is almost twice as large as for the samples after grinding.

Continuous Two-Dimensional Melting of Vortex-Solid in High Temperature Superconductors

1989 ◽  
Vol 169 ◽  
Author(s):  
N.-C. Yeh
Keyword(s):  
Magnetic Field ◽  
High Temperature ◽  
Defect Density ◽  
High Temperature Superconductors ◽  
Finite Size ◽  
Sample Thickness ◽  
Zero Field ◽  
Two Dimensional ◽  
Thermally Induced ◽  
Transport Studies

AbstractA model of continuous two-dimensional melting in the mixed state of high temperature superconductors is proposed. Two-dimensional melting sets in at a cross-over temperature Tx(H) below the three-dimensinal phase transition Tx(H) due to finite size effects, and Tx(H) is a function of the sample thickness (lc), applied magnetic field (H), and k(= λ/ξ) For a given zero-field transition temperature Tc0 and material properties, (such as defect density), the onset temperature of 2D-melting (Tx(H)) decreases with decreasing sample thickness and increasing magnetic field. In transport studies, thermally induced melting is further complicated by the depinning effect of high current densities.

Calculation of the Interaction Forces between Superconductor and Permanent Magnet Using Equivalent Current Loops in Zero Field Cooling

2013 ◽  
Vol 634-638 ◽  
pp. 2436-2441
Author(s):  
Yong Yang ◽  
Xiao Jing Zheng ◽  
Tao Li ◽  
Zhi Qiang Hua
Keyword(s):  
Permanent Magnets ◽  
High Temperature Superconductors ◽  
Magnetic Bearing ◽  
Image Method ◽  
Zero Field ◽  
Vertical Force ◽  
Interaction Forces ◽  
Magnetic Dipoles ◽  
Zero Field Cooling ◽  
Field Cooling

The levitation between high temperature superconductors (HTSs) and permanent magnets (PMs) has been applied to the flywheel energy storage systems and magnetic bearing systems for the last nearly twenty years. The interaction forces acting on the levitating body are calculated by the modified frozen-image method. The magnetic dipoles are equivalent to Amperian current loops. The current intensity in loops changes linearly when the PM moves. Under the zero field cooling condition, the expression of vertical force is obtained when the PM traverses vertically, and when the PM traverses horizontally, the expressions of vertical and horizontal forces are obtained. Those expressions of vertical and horizontal forces are gained by calculating the forces between current loops and using superposition theorem of vector. The calculations agree well with the previous experimental data, which means that the deductions of the expressions are reliable.

Application of ANSYS Secondary Development in Magnetic Density Analysis of Permanent Magnet Synchronous Motor

2011 ◽  
Vol 199-200 ◽  
pp. 1140-1144 ◽  
Author(s):  
Cong Gan Ma ◽  
Shu Guang Zuo ◽  
Rong He ◽  
Lv Chang He
Keyword(s):  
Magnetic Flux ◽  
Permanent Magnet Synchronous Motor ◽  
Synchronous Motor ◽  
Programming Method ◽  
Secondary Development ◽  
Magnetic Flux Density ◽  
Phase Voltage ◽  
Rotational Angle ◽  
Density Analysis ◽  
Two Parameters

In order to realize the rotation of permanent magnet synchronous motor and to carry magnetic flux density analysis of motor at 3-phase voltage load out, a set of ANSYS secondary development programming method with APDL is proposed in this paper. In this programming method, firstly, the rotational angle of the rotor at any time is calculated by two parameters of time and rotational speed. Secondly, the 3-phase voltage load at corresponding time can be got by two parameters of time and the 3-phase voltage frequency. Finally, according to the rotational angle of the rotor at any time and the 3-phase voltage load at the corresponding time, the whole process of the motor rotation is realized with ANSYS loop statement. This programming method solves the difficult problem that the rotor doesn’t rotate for ANSYS magnetic analysis and the magnetic flux density of permanent synchronous motor can be calculated more exactly.

scholarly journals Self-organization in porous 6H–SiC

2000 ◽  
Vol 15 (9) ◽  
pp. 1860-1863 ◽  
Author(s):  
S. Zangooie ◽  
J. A. Woollam ◽  
H. Arwin
Keyword(s):  
Acid Concentration ◽  
Current Density ◽  
Basal Plane ◽  
Hydrofluoric Acid ◽  
Chemical Etching ◽  
Sample Surface ◽  
Rate Of Change ◽  
Self Organization ◽  
Pore Sizes ◽  
Etching Parameters

Pores in porous 6H–SiC were found to propagate first nearly parallel with the basal plane and gradually change direction and align with the c axis. As a consequence, well-defined columnar pores were formed. It was shown that the rate of change of propagation directions was influenced by the etching parameters, such as hydrofluoric acid concentration and current density. Larger currents resulted in formation of larger pores. Pore sizes were found to increase with depth due to a decrease of the acid concentration. In addition, due to chemical etching effects, larger pore sizes were obtained close to the sample surface.

scholarly journals Creep and Recovery Behaviors of Lithium-Based Magnetorheological Grease

2021 ◽  
Vol 8 ◽  
Author(s):  
Xudan Ye ◽  
Jiong Wang
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Flux Density ◽  
Creep Strain ◽  
Constant Stress ◽  
Zero Magnetic Field ◽  
Magnetic Flux Density ◽  
Zero Field ◽  
Creep And Recovery ◽  
Recovery Behavior

This article studies the creep and recovery behavior of magnetorheological grease (MRG) under constant stress shear. The experiment is done by using a parallel plate rheometer with magnetron attachment and temperature control unit. The effects of constant stress, CI particle concentration, magnetic flux density and temperature on creep and recovery behavior are systematically studied. Experimental results show that as the constant stress increases, the response strain will also increase. The creep strain tested under zero field is higher than the value tested under a magnetic field, indicating that the creep and recovery behavior of MRG is highly dependent on the magnetic field strength. In addition, the creep and recovery behavior of MRG is greatly affected by temperature. Under the action of a magnetic flux density, the creep strain will decrease with the increase of temperature. The result is opposite at zero magnetic field.

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