摘要:

The paper discusses the extent and nature of the internal changes in a metal subjected at a suitable temperature to a steady stress sufficiently high to produce flow and rupture. The general strength of metals at high temperatures is compared with that of other metals at atmospheric temperatures. Flow occurs in metallic aggregates by three means which are not necessarily independent, namely, by slip within the crystals, by grain boundary movement, and by continuous recrystallization under stress. The method of ascertaining the rate of creep and estimating significance of the tests are briefly described in relation to the probable mode of flow. The connection between the flow and the previous condition of the metal,i. e., whether cast or worked, etc., is related to the microstructure and grain size. Further factors, such as the action of grain boundary and crystalline material, within the grains are discussed in relation to their effect on intercrystalline rupture and slip. Evidence is given of the importance of these factors by the consideration of a case of an alloy which age‐hardens on exposure to service temperatures. Further factors, such as the effect of temperature, are referred to in the concluding portion of the paper.

ISSN:0148-6055    

DOI:10.1122/1.2116492

出版商:The Society of Rheology    

年代:1932

数据来源: AIP

摘要:

A further development is given in this paper of the theory of the flow of liquids in capillaries under inlet pressures that are high enough to cause an appreciable change in viscosity, such that the viscosity can no longer be treated as uniform. The results are put in the form of Poiseuille's law, with a correction factor. Starting from any given empirical relation between viscosity and pressure, an expression for the corresponding correction factor can be obtained by integration. Conversely, if the form of the function connecting viscosity with pressure is unknown, it can be determined by differentiation of the observed flow‐pressure graph connecting rate of flow with inlet pressure. For the usual case it can be shown that the rate of flow approaches an asymptotic limiting value. If for any reason the logarithmic viscosity‐pressure diagram takes an upward bend, the viscosity increasing more rapidly than before, the rate of flow must actually decrease with further increase of inlet pressure, and the flow‐pressure graph will pass through a maximum. The foregoing analysis makes possible several different methods for computing the viscosity‐pressure characteristics of a lubricating oil, or other liquid, from the simple experimental procedure of observing the efflux out of a long metal capillary into the free atmosphere. The paper includes a review of the calculations by S. Kiesskalt for flat capillaries; and indicates under what conditions the extrusion type of high‐pressure gage proposed by C. Barus might be realized. The theory is illustrated by the experiments of C. Barus on marine glue to 30,000 pounds per square inch, and by more recent experiments of the authors on pressure‐gun and cup grease, and on castor oil, to approximately 45,000 pounds per square inch. The long capillary method is less sensitive and less precise but much more rapid than the two methods previously used in the work of the A. S. M. E. Special Research Committee on Lubrication. From the data presented on castor oil it appears that all three methods are in reasonable agreement.

ISSN:0148-6055    

DOI:10.1122/1.2116493

出版商:The Society of Rheology    

年代:1932

数据来源: AIP

摘要:

In an earlier paper concerning the deforming of plastic materials the distinction has been emphasized between (a) the extent to which a material can be deformed without rupture, and (b) the stress required to cause this deformation to start to take place. The former (a) (which formed the main consideration of the earlier paper) is the plasticity, and the latter (b) is in the nature of a yield‐value or shearing strength.

ISSN:0148-6055    

DOI:10.1122/1.2116494

出版商:The Society of Rheology    

年代:1932

数据来源: AIP

摘要:

In another connection, the anomalous behavior of very dilute aqueous salt solutions, notably potassium chloride and potassium chlorate, made it of interest to learn the viscosities of these solutions at low concentrations. The viscosity of aqueous KCl has been precisely measured by Joy and Wolfenden, but so far as we have found them, the recorded data onKClO3proved inadequate for our purpose. The viscosity has therefore been measured in the hope that a study of the variation of this property with the concentration might reveal a relationship enabling us to interpret our results in the prior study.

ISSN:0148-6055    

DOI:10.1122/1.2116495

出版商:The Society of Rheology    

年代:1932

数据来源: AIP

摘要:

Thixotropy (thixein, to smear; tropein, to change) has recently been applied to a phenomenon of gels and sols which really has been known for some time, but whose significance has merely begun to dawn. Some systems will decrease in viscosity when stirred. Such are certain gelatine gels, rubber cements, and certain others as Portland cement. In case of the glycerine and litharge mixtures whose thixotropic properties I am reporting elsewhere, a change from a solid to a very plastic state may be brought about by violent mechanical agitation. These changes in viscosity, hardness, plasticity, and solidity with mechanical agitation are connected with thixotropy. A liquid or a sol whose rate of flow through small tubes is not proportional to the pressure gradient may be said to be thixotropic also. There are many illustrations of this in albumins, celluloses, and suspensions, oils and greases. The phenomenon of thixotropy gives important clues to the nature of the structure of these colloid systems. Such changes immediately suggest analogies to the sensibility of living biological systems to mechanical stimulation. Also after a thixotropic system has been agitated the transformation from the less viscous to the more viscous state has analogy with recovery in living organic systems.

ISSN:0148-6055    

DOI:10.1122/1.2116496

出版商:The Society of Rheology    

年代:1932

数据来源: AIP

摘要:

In modifying previous methods for obtaining pure ricinoleic acid, the authors were able to prepare the compound with a degree of purity which had not previously been reached and discovered that very pure sodium ricinoleate may be crystallized from its alcoholic solution.The authors determined a series of physical properties of pure ricinoleic acid, the specific gravity, refractive index, and viscosity at various temperatures. These determinations make it possible to establish the degree of purity of this chemical species rapidly and certainly, or, on the other hand, to draw comparisons between them and the properties of other fatty acids which would give us more accurate and broader knowledge of their constitution.

ISSN:0148-6055    

DOI:10.1122/1.2116497

出版商:The Society of Rheology    

年代:1932

数据来源: AIP

摘要:

Some of the more leisurely sightseers in the National Capitol make the pilgrimage to the Rock Creek Cemetery not alone to see the Adams monument of Saint Gaudens but to examine the marble tombstone which has become bent during the course of years due to being supported on four posts under the ends but left without support in the middle. The stone is 180 cm long, 90 cm wide and 5 cm thick, and the sagging amounts to some 8 cm. The amount of sag makes any effect due to solution or weathering inadequate as an explanation. That the phenomenon cannot be due to a simple elastic deformation seems equally beyond question, for had the workmen who put the stone in place eighty years ago noted a three inch sag they would undoubtedly have supported the middle part.

ISSN:0148-6055    

DOI:10.1122/1.2116498

出版商:The Society of Rheology    

年代:1932

数据来源: AIP

摘要:

The methods employed to determine the deformation under stress of soft solids are largely empirical in character. To evaluate the working properties of materials that are molded or extruded, and the “creep,” “cold flow,” or “plasticity” of materials that yield slowly under load, recourse must be had to comparative tests simulating as closely as possible the conditions to which the material will be subject in service. As service conditions can seldom be exactly duplicated in any practical test, particularly with respect to the time element, these methods always involve some uncertainty as to the validity of the parallel between test and service behavior, and the results are in any case limited in their application. There is, therefore, a need for the development of methods of determining, from simple general tests, the character and amount of deformation under given conditions. While much of the theoretical background for this purpose is available, little progress has been made in applying it to the test methods adapted to materials of the type in question.

ISSN:0148-6055    

DOI:10.1122/1.2116499

出版商:The Society of Rheology    

年代:1932

数据来源: AIP

ISSN:0148-6055    

DOI:10.1122/1.2116500

出版商:The Society of Rheology    

年代:1932

数据来源: AIP

ISSN:0148-6055    

DOI:10.1122/1.2116501

出版商:The Society of Rheology    

年代:1932

数据来源: AIP