Toroidal Specimens Research Articles

Disaccommodation in manganese-zinc ferrite

The temperature spectrum of disaccommodation for manganese-zinc ferrous-ferrite toroidal specimens is studied using two methods of magnetic shock. One of these methods, namely, disturbance using a capacitor discharge (ac demagnetization), produces a broad maximum in the disaccommodation against temperature characteristic. The other method of disturbance, using the field provided by a permanent magnet, is shown to give a discrete disaccommodation spectrum, which is used to analyse three room-temperature diffusion effects in terms of the partial pressure of oxygen during firing. One of these effects, which depends only on the oxygen partial pressure (and hence cation vacancy concentration), has not previously been reported at room temperature. The permanent-magnet disturbance is also used to investigate the magnetization states in the toroidal specimens.

A First Order Solution for the Stress Concentration Present at the End of Roller Contact

An approximate solution of the “critical” maximum compressive stress present in rolling contact fatigue is given. Geometries normally used in rolling contact rig tests having contact areas varying from rectangular to full elliptical contact are considered. For cylinders in contact it is shown that the first order solution for end of contact stress is considerably above the nominal line contact Hertz stress usually calculated. Confirmation of the approximate stresses calculated is provided by deformation studies just into the plastic regime, and rolling contact fatigue tests on both cylindrical and 100-inch radius toroidal specimen rollers. Contributed by the ASLE Technical Committee on Bearings and Bearing Lubrication and presented at the Annual Meeting of the American Society of Lubrication Engineers held in New York, April, 1963.

Initial Permeability Characteristics of Vanadium-Doped Manganese-Zinc Ferrites

The basic composition of manganese-zinc ferrites used in this experiment is represented by (MnO)27(ZnO)20 (Fe2O3)53. When doped by a small amount of vanadium and calcium, a significant reduction of high-frequency losses has been observed. Measured toroidal specimens were prepared by standard sinteringtechniques, and special precautions have been taken to maintain the sintering temperatures within ±2 degrees. Initial permeability μ, μ−1 tanδ, and the hysteresis coefficient h10 were measured by a Maxwell bridge at room temperature. In these experiments it was found that, under certain sintering conditions,losses are minimized by the use of adequate amounts of vanadium doping yielding less than 3×10−6 and 20 of μ−1 tanδ and the hysteresis coefficient h10, respectively. The loss analysis, granular structure observation and electrical resistivity measurements were also performed.

Rectangular Hysteresis Loop Ferrites with Large Barkhausen Steps

Observations have been made at low temperatures of large discontinuities (steps) in the 60-cycle hysteresis loops of polycrystalline ferrites containing copper. At the temperature for step formation, which is a function of copper content, the coercivity decreases and the loop squareness approaches unity. This behavior is attributed to the formation (in the toroidal specimens used) of circular 180° domain walls having different threshold fields. This domain wall configuration is probably brought on at low temperatures by a low effective magnetocrystalline anisotropy provided by the localized distortions exerted by divalent copper in the spinel lattice.

Electrical and magnetic measurements in an electrical engineering factory

The paper describes how, by the application of negative feedback amplifiers and high-speed polarized relays, new methods of performing the commoner electrical and magnetic measurements in power engineering have been developed. Examples include the application of amplifier techniques to the measurement of power and voltage, and of high-speed relays to the measurement of speed, frequency and the slip frequency of induction motors. In a Section on industrial magnetic measurements, apparatus is described for routine tests on whole sheets of transformer steel and on toroidal specimens; while a new approach to routine permeability measurements is given. The paper concludes with an example in the field of dielectric measurements—the rapid measurement of the power-factor of insulation samples.

Stressed ferrites having rectangular hysteresis loops

A study has been made of the effect of stress on the magnetic properties of ferrites. Rectangular hysteresis loops were obtained by encasing toroidal specimens in plasties which shrink during polymerization. Ferrites having this type of hysteresis loop are useful in magnetic switching and magnetic memory devices.

The Emission and Scattering of Neutrons

Be-radon sources, which utilize as high as 1800 millicuries of radon, and probably emit about 2 to 3 million neutrons per second, were used with an ionization chamber and an amplifier system capable of detecting individual neutrons in the presence of the gamma-radiation, to investigate the emission and the properties of neutrons. The energy distribution of the neutrons emitted under the bombardment of the three groups of alpha-particles present has been studied, and the results analyzed in terms of a number of neutron groups, which are discussed in terms of transitions involving neutrons and gamma-rays, with at least one, and possibly two resonance levels. The maximum energy of the neutrons appears to be about 14.2 MEV, and indicates a neutron mass of about 1.0068. Deuterium-radon and zinc-radon have been found to give, if any, less than 1 percent of the number of neutrons emitted by Be-radon. The interaction of high energy neutrons with matter seems to be largely one of approximately elastic collisions with atomic nuclei, resulting in scattering of the neutrons. The scattering of neutrons has been studied using interposed cylindrical specimens to scatter neutrons away from the ionization chamber, and using toroidal specimens to scatter neutrons into the ionization chamber. The collision areas computed from the scattering measurements increase with atomic weight in a manner that indicates that the effective volume of the nucleus is proportional to its atomic weight, but the classical elastic sphere collision theory is inadequate, and a wave theory of scattering must be used to obtain consistent quantitative results. The neutron "radius" indicated is of the order of 1.2\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}13}$ cm, and the nuclear radii appear to vary about as ${(\mathrm{atomic}\mathrm{weight})}^{\frac{1}{3}}$, ranging from 2.5\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}13}$ cm for lithium to 7.8\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}13}$ cm for lead.