Plastic zone in a thick layer with a disc-shaped crack

Summary The width of the annulus of plastic deformations for a layer of ideally elasto-plastic material with a very thin plastic zone has been discussed. The problem reduces to a Fredholm integral equation of the second kind, with the upper limit to be determined by a trial-and-error method from the condition of finiteness of the normal stress. The expression for the width of plastic zone has been found. The distribution of stresses is given in diagrams and its behavior discussed.

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Zusammenfassung Es wurde die Weite eines Ringes einer plastischen Veränderung in einer Schicht von idealem, elastisch-plastischem Material mit einer sehr dünnen plastischen Zone, untersucht. Das Problem verringerte sich zu einer Fredholm Integralgleichung zweiter Ordnung. Die obere Grenze wurde durch eine Versuchs- und Fehlermethode auf den Gebrauchszustand des normalen Druckes bestimmt. Die Formel für die Weite der plastischen Zone wurde gefunden. Die Verteilung der Drucke ist in einem Diagram gezeigt und ihr Verhalten wurde besprochen.

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Résumé Dans l'ouvrage on a discuté la largeur d'un anneau des déformations plastiques dans une couche d'un matériau élastoplastique avec une zone plastique très mince. Le problème est réduit à une equation intégrale de Fredholm de deuxième ordre, avee la limite supérieure déterminée par la méthode des essais successifs, appliquée sur la base d'une condition, que les contraintes normales ont des valeurs finies. Les formules pour la largeur de la zône plastique ont ététabliés et la répartition des contraintes est discutèe et prèsentée sur les graphiques.

     

Hall generator with variable active-layer thickness

The principle of operation of a new semiconductor device, a Hall generator with a variable-thickness active layer, is discussed. Such a device results from the location of a p-n junction in close proximity to the surface of a semiconductor plate, thus isolating the thin active layer of the Hall generator from the base. Two additional electrodes, one on the base and one on the active layer of the Hall generator, allow variation of space-charge location on the p-njunction by means of reverse biasing. Initial results on experimental units are also given.     

Studies on the addition reaction of diethylamine to multiacrylate catalyzed by lithium diethylamide

Summary The nucleophilic addition reaction of diethylamine to vinyl groups of multiacrylate - oligo[(2-acryloyloxy-5-methyl-1,3-phenylene)methylene] and to p-cresyl acrylate as model compound were investigated. The reaction was carried out in benzene with excess amine in the presence of lithium diethylamide as catalyst within the temperature range from 21 to 50°C. Based on the obtained results, it has been shown that the addition reaction rate of diethylamine to multiacrylate and p-cresyl acrylate is proportional to [CH₂=CH-] and to [Et₂NLi] with the ratio [Et₂NH]_o/[Et₂NLi]_o= 5. Second-order addition reaction rate constants and activation energies for the systems under investigation have been determined. The chemical composition of the resultant addition products has been confirmed by spectroscopic methods: IR, ¹H-NMR, ¹³C-NMR and elemental analysis. Received: 29 August 1999/Revised version: 20 April 2000/Accepted: 20 April 2000     

Peritektoidische Reaktion in einem Stahl mit rd. 1% C und 18% Cr

Betrachtungen zur peritektoidischen Reaktion γ + M₂₃C₆ → M₇C₃ in einem Stahl mit rd. 1% C und 18% Cr im Zusammenhang mit früheren Schrifttumsangaben. Elektrolytische Isolation der Phasen nach unterschiedlichen Austenitisierungsbedingungen des Stahles und chemische sowie Röntgenanalysen der gebildeten Phasen sowie vergleichende metallographische Beurteilung der entstandenen Gefüge. Erörterung der Versuchsergebnisse im Hinblick auf Ablauf, Morphologie und Bildungsmechanismus der peritektoidischen Reaktion unter Berücksichtigung der Diffusionsvorgänge und vorangehender Schrifttumsangaben.     

Keimbildung und Wachstum von Vanadincarbiden auf 0,8% C enthaltendem Austenit

Untersuchung des Mechanismus der Bildung und des Wachstums von Vanadindiffusionsschichten beim Diffusionsvanadieren mittels Gasverfahren auf 0,8% C enthaltendem Austenit. Bestimmung des Verlaufs der Bildung von Schichten durch Analysieren ihres Zustandes während des Vanadierens.     

Wetting of Cu by Bi–Ag based alloys with Sn and Zn additions

Contact angles on copper substrate of Bi–Ag–Sn and Bi–Ag–Zn ternary alloys containing 3, 6, and 9 at.% of Sn and Zn, respectively, were studied with the sessile drop method. Wetting tests were carried out at 573 and 603 K with or without the use of a flux. Without the flux, the examined alloys do not wet copper, i.e., the observed contact angles are higher than 90°. However, in the presence of the flux wetting of copper is observed. In the case of alloys with Sn, the contact angles decrease with increasing content of Sn, while in the case of alloys with Zn no such tendency is observed. Solidified solder–substrate couples were cross-sectioned and examined with scanning electron microscopy coupled with electron dispersive X-ray analysis.     

Desolvation step preceding electroreduction and the electrochemical reactions of the Ni(II)/Ni(Hg) system in dimethylformamide (DMF) and its mixtures with water

The kinetics of the electrode reaction of the Ni(II)/Ni(Hg) system in DMF and its mixtures with water at different concentrations of several background electrolytes has been studied.

Similarly to aqueous solutions, at higher background electrolyte concentrations the charge transfer step is preceded by a chemical reaction. It was deduced that this proceeding reaction is due to slow dissociation of the solvent molecule in the S¹_N process.

The change of a solvent from water to 70 vol.% of DMF decreases the standard rate constant (k_s) for about one order of magnitude. At larger DMF content k_s is virtually independent of the solvent composition. The change of k_s with the DMF content was explained by assuming the resolvation of Ni(II) ions at the electrode surface in proportion to the surface coverage of the electrode molecules of both solvents.