New method for solving the one-dimensional problem of the displacement of petroleum by water taking account of capillary forces

The article describes a method for the solution of the one-dimensional problem of the displacement of petroleum by water taking account of capillary forces; on the basis of the method, in the equations of two-phase filtration it is proposed to use a new, soughtfor function, i.e., the fraction of water in the total flow of liquid. As a result, the problem is simplified, the labor consumption of the calculations is reduced, and it becomes possible to make a qualitative evaluation of the behavior of the solutions, including the analytical justification of a solution with a stabilized zone.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 3, pp. 83–91, May–June, 1975.     

Diffraction of plane waves by an infinitely long elastic rod floating on the surface of a liquid

The interaction of plane waves coming from infinity with an infinitely long elastic rod floating on the surface of a liquid is considered. The liquid is assumed to be ideal and have infinite depth. It is assumed that the rod cannot become separated from the liquid. The parameters of the waves that pass through the rod and are reflected from it are determined, and the force factors in the transverse sections of the rod are found.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 62–67, September–October, 1980.     

Ferrite-loaded cavity resonators

The problem of the determination of the free oscillation modes of a cavity resonator completely filled with magnetized ferrite is considered. A first order formulation, which takes into account the equation of motion of the magnetization vector together with Maxwell's equations, is used. By expanding the field vectors in terms of solenoidal and irrotational eigenfunctions of the corresponding empty resonator, a matrix eigenvalue problem in classical form is obtained. The general formulation is specialized to the particular case of a circularly cylindrical resonator filled with transversely magnetized ferrite. A numerical analysis for the determination of resonance frequencies and field configurations is carried out.Work partially supported by Consiglio Nazionale delle Ricerche of Italy.     

Stress amplification and plastic flow for spheroidal shells: Applications to myopia

Amplification of effective stress and plastic strain rates after yielding are derived for the anisotropic stress fields of the prolate and oblate spheroidal shells as models of the myopic and hyperopic eyes. Dimensionless closed-form results are presented for arbitrary axis ratio with both constant shell thickness and variable shell thickness, using the constant scleral mass assumption. The results show that the myopic and hyperopic eyes are susceptible to failure by plastic yielding at the equator and pole, respectively, for high intraocular pressures. Experimental data from the equatorial zone of rabbit sclera shows scleral yielding and plastic flow for intraocular pressures greater than 32 mm Hg. Practical applications include glaucoma and pathological myopia.     

Two types of high-temperature weldable strain gages: Ni−Cr half-bridge filaments and Pt−W half-bridge filaments

The historical development of the single active and “true” (zero gage factor) dummy weldable strain gage is reviewed. The combination of these devices into a half-bridge gage results in transducers capable of static-strain measurements at temperatures of 650 and 950° F for Ni?Cr alloy elements and Pt?W alloy elements, respectively. General application notes concerning these instruments are also included.     

Zum zeitlichen Verlauf des Kriechens von Zementstein und Beton

Zusammenfassung Es wird eine Kriechfunktion abgeleitet, die die bekannten, empirisch bestimmten Kriechfunktionen als Spezialfälle enthält. Für die relative Endkriechverformung ergibt sich sowohl aus der exakten Lösung als auch aus den Näherungen der Wert 2/E. Für die Halbwertszeit, nach der die Hälfte des Endkriechmaßes erreicht wird, bekommt mann = 2l RZ , E. R ist eine Größe, die der inneren Reibung proportional ist. Es wird eine Beziehung angegeben, dieR mit der AktivierungsenergieQ verknüpft. Mit den aus Kriechkurven zu entnehmenden Werten fürR ist damit auchQ bekannt.

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Summary A formula for creep deformation as a function of time has been derived. It has been shown, that the empirical functions previously used by several authors are special cases of this more general function. The final creep deformation is found to be 2/E. Half of the final creep deformation is reached after a time ofn=21RZ/qE. R is a value, which is proportional to internal friction. There exists a relation betweenR and the activation energy. The activation energy can be calculated ifR is evaluated from creep data.

     

Recombination of electrons in a plasma expanding into a vacuum

As noted in a paper by one of the authors [1], when a hot ionized gas expands into a vacuum, at a certain moment ionization equilibrium must necessarily break down. Shortly after this point, which may be found by the method indicated in [1], ionizing events become very rare and only recombination occurs in the gas. In [1] photorecombination and triple collisions with the capture of an electro to the ground level of the atom were considered. Here the recombination did not proceed to the end: on expanding to infinity and cooling to zero the gas remained partially ionized.Papers have recently appeared [2–7] in which the significant role of triple collisions with the capture of electrons to upper atomic levels is noted. The recombination process has a cascade character at low temperatures and densities which are not excessively small. At first, the electron is captured by one of the upper atomic levels in a triple collision with an ion and another electron. Subsequently, as a result of electron collisions of the second kind, and later also as a result of radiative transitions, the bound electron descends through the energy levels to the atomic ground state. The recombination coefficient for such a process depends much more strongly on the electron temperature T than for a triple collision with capture directly by the ground level (as T^–9/2 as opposed to T^–1), and at low temperatures cascade recombination proceeds much more quickly than capture to the ground level. Since this casts doubt upon the conclusions of [1] regarding the residual ionization when a plasma expands into a vacuum, we were led to re-examine the question, which, as will be clear from what follows, is not considerably more complicated.     

Chemoconcentration capillary effect associated with the motion of a drop in a liquid

The effect of a surface chemical reaction involving a weak soluble surface active substance on the motion of a drop in a liquid is investigated. It is shown that as a result of the Marangoni effect the non-uniformity in the distribution of the substance along the surface associated with the proper motion of the drop and the chemical reaction has an important influence on the nature of the motion of the drop and on the force exerted by the surrounding Liquid. Under certain conditions this Leads to the development of a thrust proportional to the velocity of the drop (chemoconcentration capillary effect). The condition of occurrence of the thrust is obtained, together with its dependence on various physical parameters.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 147–154, January–February, 1988.     

Beitrag zur Prüfung metallischer Werkstoffe im Torsionsversuch

Zusammenfassung Der Torsionsversuch eignet sich zur Untersuchung des plastischen Verhaltens von Metallen bei erhöhten Temperaturen, wenn die Fließspannung stark von der Umformgeschwindigkeit abhängt. Aus der gemessenen Drehmoment-Drehwinkel-Kurve wird die Fließkurvek _f () berechnet. Hierfür wird ein Fließkriterium benötigt, dessen Unsicherheit im allgemeinen größer ist als alle Meßfehler. Diese Unsicherheit geht aber nicht in die berechnete Dehngeschwindigkeitsempfindlichkeit ein, die somit als Hauptergebnis des Versuches anzusehen ist.Um die Bedingungen technischer Warmumformung zu simulieren, wird die Verwendung extrem kurzer Proben (flacher Scheiben) empfohlen, womit sehr hohe Umformgeschwindigkeiten erreicht werden können. Für die Auswertung derartiger Versuche ist die wirksame Länge der kurzen Proben — experimentell oder semiempirisch — zu bestimmen und die Kerbwirkung zu berücksichtigen. Im Gegensatz zur herkömmlichen Vorgehensweise wird empfohlen, die örtliche Spannung und Verzerrung nicht für die Mantelfläche der Probe zu berechnen, sondern für einen kritischen Radialabstand im Innern der Probe, für den die Schiebung von der Kerbwirkung unabhängig ist, so daß sich die zuverlässigsten Werte ergeben.

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Summary The torsion test is often used for studying the plastic deformation of metals at elevated temperatures when stress depends strongly on the strain rate. From the measured torque-twisting angle curve, the stress-strain curvek _f () has to be calculated. For this purpose a yield criterion has to be used the uncertaintly of which normally exceeds all experimental errors. This uncertaintly, however, does not propagate into the calculated strain rate sensitivity which therefore may be considered as the main result of the torsion test.For simulating the conditions of technical hot forming processes, the use of extremely short test pieces (flat discs) by which very high strain rates can be obtained is recommended. For evaluating the test data the efficient lenght of short specimens has to be determined. In opposition to the conventional procedure of test evaluation, it is recommended not to calculate stress and strain for the surface of the specimen but for a critical radius for which strain is independent of the notch effect so that the most reliable values are obtained.

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