Demagnetizing factors for cylinders

Fluxmetric (ballistic) and magnetometric demagnetizing factors N_f and N_m for cylinders as functions of susceptibility χ and the ratio γ of length to diameter have been evaluated. Using a one-dimensional model when γ⩾10, N_f was calculated for -1⩽χ<∞ and N_m was calculated for χ→∞. Using a two-dimensional model when 0.01⩽γ⩽50, an important range for magnetometer measurements, N_m and N_f were calculated for -1⩽χ<∞. Demagnetizing factors for χ<0 are applicable to superconductors. For χ=0, suitable for weakly magnetic or saturated ferromagnetic materials, N_f and N_m were computed exactly using inductance formulas     

Demagnetizing factors for square bars

Using a finite-element method, we have calculated fluxmetric and magnetometric demagnetizing factors N/sub f/ and N/sub m/ for square cross-section bars as functions of susceptibility /spl chi/ and length-to-width ratio c/a over the range /spl chi/=-1 to /spl infin/ and c/a=0.01 to 100. We present the results in figures and tables and compare them with those for cylinders. We give an approximate conjugate relation for N/sub m/(/spl chi/) of a cube.     

Steel-fibre high-strength concrete prisms confined by rectangular ties under concentric compression

This paper presents results from a continuing research program that aims to investigate the behaviour of high-strength concrete columns and to recommend some design procedures to Brazilian Building Code. The specific current work deals with experimental behaviour of steel fibre high-strength concrete columns (SFHSCC) confined with low ratios of rectangular ties under concentric compression. Twenty-four small-scale SFHSCC were tested under concentric loading and their behaviour were examined and compared with the behaviour of two normal-strength concrete columns. The variables studied in this work were the concrete strength, amount of transversal reinforcement and volumetric fraction of steel fibre. The results indicated that steel fibre not only improves the columns ductility, but also avoids the premature concrete cover spalling. Further, to improve the ductility of high-strength concrete column, the used amount of steel reinforcement is the same when the confinement or steel fibre is applied.

---

Résumé Cet article présente les résultats d'un programme de recherche continue qui a pour but d'étudier le comportement de poteaux en béton à hautes performances et de recommander quelques procédures de projet pour le Code Brésilien du béton armé. Ce travail traite du comportement expérimental de poteaux en béton fibré à hautes performances, confiné par des étriers rectangulaires, sous compression concentrique. Vingt-quatre poteaux de petite échelle ont été testés sous chargement concentrique et leur comportement a été examiné et comparé à ceux des poteaux en béton conventionnel. Les variables étudiées dans ce travail étaient la résistance du béton, la quantité d'armatures transversales et la fraction volumétrique de fibres d'acier. Les résultats ont indiqué que la fibre d'acier augmente non seulement la ductilité des poteaux, mais empêche l'enrobage prématuré de la couverture des armatures longitudinales. De plus, afin d'améliorer la ductilité de poteaux en béton à hautes performances, la quantité d'armatures en acier utilisée est la même que lorsque l'on utilise un confinement par des étriers rectangulaires ou des fibres d'acier.

     

Demagnetizing fields in bubble-domain investigations

A theory of cylindrical domains is presented for cases of a single domain in a plate of finite extent and of many domains scattered at random in a plate of infinite extent in the plane. Force and stability functions are determined for both cases. New unexpected solutions showing stability without a bias field, as well as those, for which the bias field must be directed in compliance with the magnetization in the cylindrical domain, are obtained. It is proved that the neglect of finite plate dimensions, as well as of the interaction between domains, is the cause of the apparent dependence of energy density of the domain wall on the bias field as stated in other reports. Theoretical considerations are proved by the experiments on the domain structure carried out on YFeO3orthoferrite.     

Jones matrix for image-rotation prisms

The polarization-transforming properties of rotational prisms are analyzed with polarized light by using the Jones calculus and the exact ray-trace. A general expression of the Jones matrix for a rotational prism is derived, incorporating an explicit dependence on the image-rotation angle or the wave-front-rotation angle. The Jones matrix for the Pechan, Dove, Reversion, and Delta prisms is derived where the explicit dependence on the angle of rotation of the image is given. An experiment with a rotating Dove prism is also conducted to determine the output states of polarization for incident linearly polarized light. Experimental results agree with theoretical expectations.     

Stress intensity factors for two rectangular cracks in three-dimensions

In this paper an analytical solution is developed for two three-dimensional coplanar rectangular-shaped cracks embedded in an infinite elastic medium and subjected to normal loading. Employing two-dimensional integral transforms, the solution of the problem is reduced to triple integral equations. Assuming the plane strain solution across the lengths of the narrow cracks, an approximate solution of the triple integral equations for large values of the lengths of the cracks is obtained. Finally, expressions are obtained for the stress intensity factors along the sides of the cracks and these results are given in the form of graphs.     

Stress intensity factors for cracks emanating from rectangular cutouts

The stress intensity factors are determined at the crack roots for a rectangular cutout with symmetric edge cracks in an infinite sheet under uniaxial tension.The stress analysis is carried out using conformal mapping and the Muskhelishvili formulation. Numerical results are obtained for varying crack length and selected length-to-width ratios for the rectangle. The stress intensity factors are compared to those for a single internal crack to illustrate the influence of the cutout effects.

---

Zusammenfassung Die Spannungsintensitatsfaktoren an den RiBwurzeln zweier an beiden Enden cities rechteckigen Ausschnitts symmetrisch angeordneten Risses in einem dünnen Blech unendlicher Ausdehnung, welcher einer einachsigen Spannung unterworfen ist, werden bestimmt.Die Analyse der Spannungen wird mit Hilfe der Konformen Darstellung and der Muskhelishvili-Formulierung durchgeführt. Es ergeben sich zahlenmäßige Resultate fur verschiedene Rißlängen and Verhältnisse von länge zu Breite des rechteckigen Ausschnittes.Der Vergleich der Spannungsintensitatsfaktoren mit denjenigen eines einzelnen Risses illustrieren den Einfluß des Ausschnittes and seiner Abmessungen.

---

Résumé On détermine les facteurs d'intensité de contraintes aux extrémités de deux fissures amorçées de part et d'autre d'un trou rectangulaire dans une tôle mince de dimensions infinies et soumise à traction uniaxiale.L'analyse des contraintes est effectuée en recourant à la représentation conforme, et à la formulation proposée par Muskhelishvili. On obtient des résultats numériques correspondant à diverses longueurs des fissures, et divers rapports de la longueur sur la largeur du trou rectangulaire.La comparaison des facteurs d'intensité de contraintes obtenus et de ceux qui correspondent a une simple fissure interne, illustre les effets du trou et de ses proportions géométriques.

     

Stress intensity factors for cracked rectangular cross-section thin-walled tubes

For cracked structural rectangular thin-walled tubes, an exact and very simple method to determine the stress intensity factors has been proposed based on a new concept of crack surface widening energy release rate. Unlike the classical crack extension energy release rate, the crack surface widening energy release rate can be expressed by the G^*-integral and elementary strength theory of materials for slender cracked structures. From present discussions, a series of new and exact solutions of stress intensity factors are derived for cracked rectangular and square tubes. The present method can also be applied to cracked polygon thin-walled tubes.     

Minimum deviation for uniaxial prisms

Formulas for the minimum-deviation angle when the optical axis is contained in the incidence plane have been developed. The variation of the minimum-deviation angle as a function of the direction of the optical axis has been analyzed, and it was verified that the width of the incident beam was the same as the width of the emerging beam for the extraordinary rays as well.     

Magnetometric Demagnetizing Factors for Various Shapes of Rotational Symmetry

We have investigated the magnetometric demagnetizing factors of rotation-symmetrical magnetic bodies of relative permeability $mu$ placed in a uniform magnetic field parallel to the axis of rotation. The bodies we considered include a cylinder, a sphere, a bicone, and a rotating astroid. We numerically calculated the magnetometric demagnetizing factors from the surface magnetic charge densities $sigma$ obtained by the surface magnetic charge simulation method. We show that the magnetometric demagnetizing factors for various shapes of rotation-symmetrical bodies are significantly different from those of a sphere. We have determined the shape producing the largest demagnetizing field in ferromagnetic bodies with sufficiently large relative permeability $mu$ . We report the magnetometric demagnetizing factors for uniformly magnetized bodies ($mu=1$ , i.e., susceptibility $chi=0$ ) of various shapes.      

Demagnetizing field computation for dynamic simulation of themagnetization reversal process

The magnetic-field distribution for a thin magnetic film is computed using the fast Fourier transform technique. The method is quite general and accommodates any two-dimensional magnetization distribution. It allows the computation of fields both inside the film (demagnetizing fields) and outside (stray fields and leakage)     

Analytical solutions for image orientation changes in prisms

Optical prisms are most commonly employed because of their ability to output an image of different orientation relative to the input object. Previous papers have presented a systematic but numeric approximation for designing a single prism, which outputs an image with a specific image orientation. Instead of a numerical solution, an exact analytical solution for the same problem is offered. Further, how to design prism systems by using off-the-shelf right-angle prisms and roof prisms as building blocks to obtain an output image with a specific image orientation is addressed. Illustrative examples are given to verify the proposed approach and demonstrate its use.     

On the compressive strength prediction for concrete masonry prisms

The results of a combined experimental program and numerical modeling program to evaluate the behavior of ungrouted hollow concrete blocks prisms under uniaxial compression are addressed. In the numerical program, three distinct approaches have been considered using a continuum model with a smeared approach, namely plane-stress, plane-strain and three-dimensional conditions. The response of the numerical simulations is compared with experimental data of masonry prisms using concrete blocks specifically designed for this purpose. The elastic and inelastic parameters were acquired from laboratory tests on concrete and mortar samples that constitute the blocks and the bed joint of the prisms. The results from the numerical simulations are discussed with respect to the ability to reproduce the global response of the experimental tests, and with respect to the failure behavior obtained. Good agreement between experimental and numerical results was found for the peak load and for the failure mode using the three-dimensional model, on four different sets of block/mortar types. Less good agreement was found for plain stress and plain strain models.