摘要:

In a paper of 1928 the author dealt with the factors which interfere with the flow of mixtures of gas and liquid in vertical channels, and again in English in 1929. In these two papers a cause of intermittency was already mentioned,viz., that although there may be sufficient gas to establish the mist condition as described below, when the rate of speed of this fluid is smaller than the differential velocity of gas and liquid, drops of liquid cannot be lifted by the gas. Liquid then, if continuously supplied, collects at the bottom and can only be lifted when enough of it has been gathered so that for some time a foam is formed.

ISSN:0148-6055    

DOI:10.1122/1.2116438

出版商:The Society of Rheology    

年代:1932

数据来源: AIP

摘要:

The mechanics of continua describe the behavior of deformable materials, that is, they predict the connection between forces and isothermic deformations in any kind of continuum. Of course the theory is confined to certain ideal materials which are so chosen as to show approximately the behavior of the natural materials. The best known among the ideal materials are the isotropic elastic solid and the viscous fluid, both of which are characterized by three constants: the modulus of compression, the density, and the modulus of rigidity, or the modulus of viscosity. Metals behave approximately in the same way as elastic solids, if only one takes sufficiently small deformations and sufficiently short times of observation. Fluids behave in the same way as the ideal viscous fluid, if the velocities of movement are sufficiently small. The problems concerning rheology, and the testing of materials which have, of late, made such great progress, urgently require, however, a more general theory which takes into account the imperfect elasticity of real solids and the imperfect viscosity of real fluids. In the following we shall discuss a few ideal materials of more general properties.

ISSN:0148-6055    

DOI:10.1122/1.2116434

出版商:The Society of Rheology    

年代:1932

数据来源: AIP

摘要:

Where rheological phenomena are too complex to yield readily to a detailed mathematical analysis, one naturally turns to the method of dimensions because of its successful use in the analogous problems of hydrodynamics, aerodynamics, and lubrication research.

ISSN:0148-6055    

DOI:10.1122/1.2116435

出版商:The Society of Rheology    

年代:1932

数据来源: AIP

摘要:

The strain‐hardening observed in poly‐crystalline metals is also present in the elastic state, but is here hidden by the comparatively big value of the modulus of shear.A simple microstructural model is described and statistically treated. The model shows all the features, which we observe in the tension‐ and compression‐test, and explains the Bauschinger‐effect and the brittleness after plastic strain.

ISSN:0148-6055    

DOI:10.1122/1.2116436

出版商:The Society of Rheology    

年代:1932

数据来源: AIP

摘要:

Certain mechanical conditions necessary for successful etching of flow layers are described. Etching tests on various materials with different nitrogen contents are discussed showing that those materials with the higher nitrogen content below certain limits produce the most clearly developed flow layers in etching. In addition, two methods of improving the etchings received from various materials by artificially introducing nitrogen into the surface layers are described.

ISSN:0148-6055    

DOI:10.1122/1.2116437

出版商:The Society of Rheology    

年代:1932

数据来源: AIP

摘要:

The plasticity of a number of solders at wiping temperatures has been determined by compression tests between parallel plates. The character of the flow is found to be that corresponding to a linear relation between shearing stress and a fractional power of the velocity gradient. This corresponds approximately to a relation between rate of compression(dhdt)and sample height (h) given by the equation:dhdt = khb, in whichkandbare constants, of whichbis independent of the test conditions. For viscous materialsb= 5.0; for most soldersbis greater than 5.0, and increasing values ofbare associated with lower temperature gradients of plasticity. It is shown that a solder must have a low temperature gradient of plasticity in order to be properly wiped, and that determination of the value ofbby means of a plasticity test can therefore be used to evaluate the working properties of a solder.A number of factors upon which the plasticity of wiping solders and the porosity of wiped joints may depend have been investigated. In particular, it is shown that segregation is not responsible for porosity, but that the latter may be dependent upon the particle size of the solid phase at wiping temperatures. The relation of particle size to the wetting power of the liquid phase is discussed.

ISSN:0148-6055    

DOI:10.1122/1.2116439

出版商:The Society of Rheology    

年代:1932

数据来源: AIP

摘要:

Thixotropy is a reversible sol‐gel transformation in which a gel can be liquefied, and thus changed to the sol condition, by mechanical disturbance—such as shaking or stirring—and after agitation ceases will, with time, again revert to the gel condition. All thioxtropic materials so far investigated have been two‐phase systems, of which one phase is generally solid and the other liquid. The present investigation deals with measurements of the thixotropy of paints undertaken to arrive at a more complete understanding of their flow characteristics, especially under the influence of extremely small shearing forces. While paint has long been recognized as a plastic material, its thixotropic nature has not been generally appreciated, although “false body” observed in some paints is a manifestation of thixotropy. Williamson attempts to calculate a “false body constant” for any paint, basing his calculations upon plasticity data, and failing to realize that the presence of “false body” in all paints requires all paints to be thixotropic. In addition Williamson has failed to appreciate the full significance of the mutual presence of plasticity and thixotropy. As has been previously pointed out by the author, Williamson's treatment of the subject is far from satisfactory in the practical case of evaluating leveling ability of paints. Other investigators of the plasticity of paints have, in general, either not recognized the presence of thixotropy or else ignored it.

ISSN:0148-6055    

DOI:10.1122/1.2116440

出版商:The Society of Rheology    

年代:1932

数据来源: AIP

摘要:

When two liquids are mixed in a certain ratio, it would not appear to be a very difficult problem to calculate the fluidity of the mixture, provided that the properties of the pure components are known and they are inert. In fact the problems at first appeared to be so simple that the assumptions involved were not even considered. After many years of groping for the solution, we have arrived at the conclusion that the problem is still unsolved. An important investigation in this field concludes: “The results of this paper also are consequently indecisive. All previous formulas are certainly useless.” A textbook of Rheology puts it succinctly, “The law of ideal mixtures is unknown.” It is not altogether unsatisfactory that the old erroneous assumptions have been admitted to be unworthy of confidence. As Hatschek says, “The ideal mixture curve for viscosity is almost certainlynota straight line.” This at least opens the way for new work, however.

ISSN:0148-6055    

DOI:10.1122/1.2116447

出版商:The Society of Rheology    

年代:1932

数据来源: AIP

摘要:

The paper of Bingham and Brown makes it desirable to study the data on the fluidities of non‐aqueous mixtures which have recently become available in connection with the International Critical Tables, to determine first whether there is a correlation between the fluidity and volume (test 3). It should, moreover, be possible to determine the composition of the compound formed in favorable cases where chemical combination takes place. Finally, although the minimum in fluidity should change with the temperature, the maximum deviation from the linear should not change with the temperature (test 4).

ISSN:0148-6055    

DOI:10.1122/1.2116412

出版商:The Society of Rheology    

年代:1932

数据来源: AIP

摘要:

The relations existing between viscosity determinations and the various stages of glass manufacture are pointed out and explained with reference to a typical viscosity‐temperature curve. The rotation viscometer employed in making such determinations is described. Curves are shown for four representative types of glasses: a lead, a lime, a lead borosilicate, and a hard borosilicate, and the use to which such comparison curves may be put is indicated.

ISSN:0148-6055    

DOI:10.1122/1.2116413

出版商:The Society of Rheology    

年代:1932

数据来源: AIP