On the Effects of Driving Amplitude, Frequency and Magnetic Fields on the Feed Rate of a Vibratory Micro-Pin Feeder

2012 ◽  
Author(s):  
Benjamin E. Rimai ◽  
Raymond J. Cipra
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Aspect Ratio ◽  
Experimental Work ◽  
Feed Rate ◽  
Small Range ◽  
Driving Frequency ◽  
Micro Scale ◽  
Aspect Ratios ◽  
Industrial Setting

The use of micro-pin feeder-bowls has been established as a way to singulate and orient micro-scale metallic pins of varying lengths. Increasing the rate and reliability with which pins can feed through the bowl is important when considering the use of such a feeder-bowl in an industrial setting. Previous experimental work, which was limited to a single driving frequency and small range of driving amplitudes of the feeder-bowl, showed low feed rates and long capture times for pins whose aspect ratio exceeded five-to-one. New experimental work has shown that by altering the driving amplitude and frequency of the feeder-bowl, pins with aspect ratios exceeding seven-to-one could be fed. Because the frequency response of feeder-bowls may be limited, other techniques for improving the feed rate for long pins were also sought. One such technique was the magnetizing of the pins to increase their response to a magnetic field which surrounded the feeder-bowl. In some circumstances, more than a 70% reduction in average capture time was observed. The improved capture performance for long pins will permit more freedom in the design of devices that can be assembled with the aid of vibratory micro-pin feeder-bowls. The research results will also be used to improve the accuracy of feeder bowl simulations.

Linear stability of rectangular cavity flows driven by anti-parallel motion of two facing walls

2002 ◽  
Vol 458 ◽  
pp. 153-180 ◽  
Author(s):  
S. ALBENSOEDER ◽  
H. C. KUHLMANN
Keyword(s):  
Aspect Ratio ◽  
Linear Stability ◽  
Cross Section ◽  
Strain Field ◽  
Rectangular Cross Section ◽  
Small Range ◽  
Critical Mode ◽  
Plane Flow ◽  
Aspect Ratios ◽  
The Cross

The flow in an infinite slab of rectangular cross-section is investigated numerically by a finite volume method. Two facing walls which move parallel to each other with the same velocity, but in opposite directions, drive a plane flow in the cross-section of the slab. A linear stability analysis shows that the two-dimensional flow becomes unstable to different modes, depending on the cross-sectional aspect ratio, when the Reynolds number is increased. The critical mode is found to be stationary for all aspect ratios. When the separation of the moving walls is larger than approximately twice the height of the cavity, the basic flow forms two vortices, each close to one of the moving walls. The instability of this flow is of centrifugal type and similar to that in the classical lid-driven cavity problem with a single moving wall. When the moving walls are sufficiently close to each other (aspect ratio less than 2) the two vortices merge and form an elliptically strained vortex. Owing to the dipolar strain this flow becomes unstable through the elliptic instability. When both moving walls are very close, the finite-length plane-Couette flow becomes unstable by a similar elliptic mechanism near both turning zones. The critical mode produces wide streaks reaching far into the cavity. For a small range of aspect ratios near unity the flow consists of a single vortex. Here, the strain field is dominated by a four-fold symmetry. As a result the instability process is analogous to the instability of a Rankine vortex in an quadripolar strain field, resulting from vortex stretching into the four corners of the cavity.

scholarly journals Heating Efficiency of Triple Vortex State Cylindrical Magnetic Nanoparticles

2019 ◽  
Vol 14 (1) ◽  
Author(s):  
De Wei Wong ◽  
Wei Liang Gan ◽  
Yuan Kai Teo ◽  
Wen Siang Lew
Keyword(s):  
Magnetic Field ◽  
Magnetic Nanoparticles ◽  
Magnetic Fields ◽  
Vortex State ◽  
Magnetic Hyperthermia ◽  
Relaxation Mechanism ◽  
Micromagnetic Simulations ◽  
Heating Efficiency ◽  
Aspect Ratios ◽  
Low Field

AbstractA well-established method for treating cancerous tumors is magnetic hyperthermia, which uses localized heat generated by the relaxation mechanism of magnetic nanoparticles (MNPs) in a high-frequency alternating magnetic field. In this work, we investigate the heating efficiency of cylindrical NiFe MNPs, fabricated by template-assisted pulsed electrodeposition combined with differential chemical etching. The cylindrical geometry of the MNP enables the formation of the triple vortex state, which increases the heat generation efficiency by four times. Using time-dependent calorimetric measurements, the specific absorption rate (SAR) of the MNPs was determined and compared with the numerical calculations from micromagnetic simulations and vibrating sample magnetometer measurements. The magnetization reversal of high aspect ratios MNPs showed higher remanent magnetization and low-field susceptibility leading to higher hysteresis losses, which was reflected in higher experimental and theoretical SAR values. The SAR dependence on magnetic field strength exhibited small SAR values at low magnetic fields and saturates at high magnetic fields, which is correlated to the coercive field of the MNPs and a characteristic feature of ferromagnetic MNPs. The optimization of cylindrical NiFe MNPs will play a pivotal role in producing high heating performance and biocompatible magnetic hyperthermia agents.

scholarly journals The Effect of an External Magnetic Field on the Aspect Ratio and Heat Input of Gas-Metal-Arc-Welded AZ31B Alloy Weld Joints Using a Response Surface Methodology

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5269
Author(s):  
Pankaj Sharma ◽  
Somnath Chattopadhyaya ◽  
Nirmal Kumar Singh ◽  
Marta Bogdan-Chudy ◽  
Grzegorz Krolczyk
Keyword(s):  
Magnetic Field ◽  
Response Surface Methodology ◽  
External Magnetic Field ◽  
Aspect Ratio ◽  
Response Surface ◽  
Heat Input ◽  
Feed Rate ◽  
Gas Flow ◽  
Gas Metal Arc Welding ◽  
Weld Joints

This study attempted to analyze and optimize the effect of an external magnetic field (EMF) on the aspect ratio and heat input for AZ31B weld joints that were welded using the gas metal arc welding (GMAW) process. The response surface methodology (RSM) was adopted for the critical analysis, and subsequently, mathematical models were developed based on the experimental results. It was observed that the EMF and its interaction with the wire feed rate significantly affected the aspect ratio and heat input, respectively. At 119 G (magnetic field), 700 mm/min (welding speed), 5.8 m/min feed rate, and 11.5 L/min (gas flow rate), the aspect ratio was 2.26, and the corresponding heat input factor (HIf) was 0.8 with almost full weld penetration.

scholarly journals Giant Extensional Strain of Magnetoactive Elastomeric Cylinders in Uniform Magnetic Fields

Materials ◽  
2020 ◽  
Vol 13 (15) ◽  
pp. 3297 ◽  
Author(s):  
Dmitry V. Saveliev ◽  
Inna A. Belyaeva ◽  
Dmitry V. Chashin ◽  
Leonid Y. Fetisov ◽  
Dirk Romeis ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Aspect Ratio ◽  
Smart Materials ◽  
Magnetic Particles ◽  
Sample Composition ◽  
Deformation Properties ◽  
Extensional Strain ◽  
The Impact ◽  
Macroscopic Shape

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.

A Simple Stationary Dynamo Model

1972 ◽  
Vol 27 (8-9) ◽  
pp. 1350-1354 ◽  
Author(s):  
Dietrich Lortz
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Aspect Ratio ◽  
Vacuum Field ◽  
Dynamo Model ◽  
Large Aspect Ratio ◽  
Helical Symmetry ◽  
Circular Loop ◽  
The Magnetic Field

Solutions of the stationary dynamo equations are derived such that outside a torus the magnetic field is the axisymmetric vacuum field of a circular loop, while inside the torus in the limit of large aspect ratio both the velocity and the magnetic fields have helical symmetry.

scholarly journals Electromagnetic Embossing of Optical Microstructures with High Aspect Ratios in Thin Aluminum Sheets

2021 ◽  
Author(s):  
Julian Heidhoff ◽  
Björn Beckschwarte ◽  
Oltmann Riemer ◽  
Lars Schönemann ◽  
Marius Herrmann ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Aspect Ratio ◽  
The Body ◽  
Thin Sheets ◽  
Submillimeter Range ◽  
Aluminum Sheets ◽  
Aspect Ratios ◽  
Body Forces ◽  
Thin Aluminum ◽  
Basic Approaches

Electromagnetic embossing enables the transfer of surface structures from forming dies to metal sheets at high forming speeds. For this purpose, the contactless forming force is provided by means of a magnetic field of a tool coil which interacts with an eddy current in the workpiece. In thin sheets which are completely penetrated by the magnetic field, the resulting Lorentz forces act as body forces that accelerate the workpiece onto the forming die. In addition to the body forces, also high strain rates can support the embossing of thin sheets. This investigation deals with the embossing of pyramidal structures in the submillimeter range and an aspect ratio of about 1 into thin aluminum sheets (3.0255 / Al99,5). In order to quantify the reproduced microstructures, their extent is determined by means of a lateral analysis. From this, the replicated height is derived. Up to now it has been possible to partially reproduce microstructures with a large aspect ratio in thin sheets. In addition, the changing surface roughness of the sheets is taken into account. Before embossing, the sheets exhibit a relatively rough surface with a rolled texture, which is smoothed by the impulse forming with an optical forming die. This study reveals basic approaches for the electromagnetic embossing of optical microstructures.

CLASSICAL XY SYSTEMS UNDER TIME DEPENDENT MAGNETIC FIELDS

1993 ◽  
Vol 07 (01) ◽  
pp. 47-55 ◽  
Author(s):  
ROBERT S. GOLDSTEIN
Keyword(s):  
Magnetic Field ◽  
Phase Diagram ◽  
Magnetic Fields ◽  
Rotating Magnetic Field ◽  
Time Dependent ◽  
Xy Model ◽  
Driving Frequency ◽  
Transition Line ◽  
Average Magnetization ◽  
Infinite Range

The phase diagram of the hard-spin XY model with infinite-range coupling under time dependent magnetic fields is investigated. Phases are distinguished by measuring time-average magnetization (TAM). For the case of an oscillating (AC) magnetic field, three phases with non-zero TAM are found in addition to a zero TAM phase. All phases are found to be synchronous with the driving frequency. The non-zero TAM-zero TAM transition line diverges to infinite magnetic field amplitude for low temperatures. An unusual type of hysteresis due to the infinite range coupling appears. Some strategic points in the phase diagram are analytically explained. Also, we interpolate between the AC and rotating magnetic field cases (investigated previously by Kuramoto's group) by studying an 'elliptical' magnetic field case.

Toroidal equilibrium of a non-neutral plasma with toroidal current, inertia and pressure

1992 ◽  
Vol 47 (3) ◽  
pp. 349-359
Author(s):  
S. N. Bhattacharyya ◽  
K. Avinash
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Aspect Ratio ◽  
The Self ◽  
Toroidal Magnetic Field ◽  
Large Aspect Ratio ◽  
Finite Mass ◽  
Neutral Clouds ◽  
Equipotential Surfaces ◽  
Neutral Plasma

Equilibrium of non-neutral clouds in a toroidal vessel with toroidal magnetic field is demonstrated in the presence of a toroidal current, finite mass and finite pressure. With a toroidal current, it is shown that in a large-aspect-ratio conducting torus the equilibrium is governed by competition between forces produced by image charges and image currents. When (where Er and Bθ are the self electrostatic and self magnetic fields of the cloud), the confinement is electrostatic and plasma shifts inwards; when the confinement is magnetic and plasma shifts outwards. For there is no equilibrium. With finite mass or finite pressure, it is shown, in a large-aspectratio approximation, that the fluid drift surfaces and equipotential surfaces are displaced with respect to each other. In both cases the fluid drift surfaces are shifted inwards from the equipotential surfaces.

Investigation of the Capabilities of Transverse Magnetic Field Controlled Laser-Induced Plasma Micro-Machining

2020 ◽  
Vol 143 (6) ◽  
Author(s):  
Yanming Zhang ◽  
Yayun Liu ◽  
Suman Bhandari ◽  
Guojun Zhang ◽  
Jianxin Deng ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Surface Quality ◽  
Transverse Magnetic Field ◽  
Transverse Magnetic ◽  
Magnetic Field Direction ◽  
Micro Machining ◽  
Laser Induced Plasma ◽  
Aspect Ratios ◽  
Machining Characteristics

Abstract Laser-induced plasma micro-machining (LIPMM) has proven a number of advantages in micro-machining due to reduced thermal defects, smaller heat-affected zones, and larger aspect ratios when compared with conventional laser ablation. The present work explores the use of external magnetic fields to further enhance process outcomes in LIPMM. Specifically, machining characteristics and outcomes including plasma intensity, attainable aspect ratios, and surface quality will be explored through a theoretical and experimental study in different classes of materials in a transverse magnetic field controlled LIPMM. First, process improvement mechanisms are illustrated in terms of plasma confinement and laser absorption in transverse magnetic fields. A magnetic field redistribution analysis is performed to reveal the differences in the achievable enhancements in machining characteristics in terms of material characteristics. Second, a set of single-factor experiments is conducted to investigate the effects of the strength and direction of the magnetic field on machining capabilities in magnetic and nonmagnetic materials (410, 304 stainless steels and silicon). The experimental results show that plasma intensity and aspect ratios can be significantly increased in the presence of transverse magnetic fields. The greatest influence on machining capability is achieved in a magnetic material. In this case, plasma intensity and aspect ratios were increased by about 176% and 160%, respectively, when compared with other materials with a magnetic field strength of 0.1 T and a magnetic field direction parallel to the processing direction. Finally, the morphology and cross-section profiles of micro-channels have been measured for verifying the impact on the surface quality of transverse magnetically controlled LIPMM.

Calculated Coronal Magnetic Fields and Their Comparison with the Coronal Structures as Observed during Five Solar Eclipses

1994 ◽  
Vol 144 ◽  
pp. 559-564
Author(s):  
P. Ambrož ◽  
J. Sýkora
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Magnetic Fields ◽  
Solar Corona ◽  
Coronal Magnetic Field ◽  
Coronal Magnetic Fields ◽  
Solar Eclipses ◽  
Coronal Structures

AbstractWe were successful in observing the solar corona during five solar eclipses (1973-1991). For the eclipse days the coronal magnetic field was calculated by extrapolation from the photosphere. Comparison of the observed and calculated coronal structures is carried out and some peculiarities of this comparison, related to the different phases of the solar cycle, are presented.

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