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Rheology#R##N#Theory and Applications, Volume 4 | 1967

THIXOTROPY AND DILATANCY

Walter H. Bauer; Edward A. Collins

Publisher Summary This chapter presents the measurement and occurrence of thixotropy and dilatancy. The concept of thixotropy arose in the study of certain colloidal dispersions. These were capable of stable existence as solid materials with a low modulus of elasticity when under a low shearing stress such as a few inches of gravitational head. They had sufficient rigidity to sustain their own weight in an inverted test tube, exhibiting a yield value or upper limit of stress under which no permanent deformation took place in the time the observer chose to wait. When vigorously mechanically agitated in a container, the dispersions transferred to a freely flowing liquid state, with viscosities of the order of the dispersing liquid. Despite some reluctance of investigators to consider properties evidenced in time intervals too short for ready measurement or in time intervals too long for convenient waiting, the number of systems shown to exhibit measurable time dependency of flow properties such as viscosity, elastic modulus, relaxation of stress and strain, and shear thinning after mechanical agitation has steadily increased. Dilatancy has been used to describe both volumetric dilation under shear and the increase in viscosity with increasing rate of shear.


Tribology Transactions | 1960

Flow Properties of Lithium Stearate-Oil Model Greases as Functions of Soap Concentration and Temperature

Walter H. Bauer; Alfred P. Finkelstein; Stephen E. Wiberley

Lithium stearate-oil greases having 4, 8, and 12% soap were prepared and flow properties of the greases were investigated, at 0, 25, and 37.8 C. Flow data were obtained with a cone and plate viscometer equipped with automatic programming and recording of shear stress versus rate of shear, and of shear stress versus time at selected shear rates. Flow curves, shear stress versus shear rate, were obtained for an initial and a repeat 300-sec cycle of shear with maxima of 1520 sec−1 and of 15,200 sec−1, Flow curves were measured for highly worked samples, previously sheared at 19,000 sec−1 for 1000 sec. The rate of change of shearing stress required to maintain a constant rate of shear was measured at nine shear rates in the interval from 190 sec−1 to 19,000 sec−1. Similar flow measurements were made on greases containing stearic acid additives. Initial flow resistance, ascribed to soap structural elements, showed temperature and concentration dependence differing from that of the sheared soap, and was destroy...


Review of Scientific Instruments | 1991

Generation of a focused proton beam with a self‐magnetically BΘ‐insulated ion diode

Walter Schimassek; Walter H. Bauer; Otto Stoltz

A self‐magnetically BΘ ‐insulated ion diode was investigated and optimized at the pulsed power line KALIF (2 MV, 50 ns, 2 Ω) to produce a focused and pulsed high‐intensity proton beam for generation of high‐power density in matter. This diode is characterized by an azimuthal insulating magnetic field that is generated by the diode current. The beam is neutralized by electrons from the cathode vanes, so that neither a gas filled drift space nor foils are needed. The beam therefore propagates in vacuum and repeated shots are possible without changing parts. The protons had energies up to 1.8 MeV and the proton content in the ion beam was about 50%. The maximum total diode current was about 800 kA and its efficiency was as high as 70%. The beam microdivergence was determined to be 1.1°. The radial dependence of the proton current density was measured and is proportional to r−1.74. This result was confirmed by 2D quasistatic particle‐in‐cell simulations. The focus was optimized by adjusting the anode shape an...


Journal of Rheology | 1966

Flow behavior of low molecular weight polybutadiene, carboxyl-polybutadiene, and butadiene-acrylonitrile copolymers.

Richard J. Boyce; Walter H. Bauer; Edward A. Collins

The flow behavior of some low molecular weight polymers was studied as a function of shear rate, shear stress, and temperature. The polymers included polybutadienes, random carboxyl and carboxyl‐terminated polybutadienes, carboxyl‐terminated butadiene‐acrylonitrile, and acrylonitrile‐butadiene copolymers. Measurements were made in the temperature range 3.8–73°C. A cone and plate viscometer and pressure capillary viscometer were used to cover the shear rate range 1−105 sec−1. Measurements were carried out with various capillary radius to length ratios. Mw and Mn values were calculated from molecular weight distribution data obtained by gel permeation chromatography. Limiting viscosity numbers were also determined. In the range of shear rates studied, all polymers showed a limiting viscosity at low rates of shear and a region of shear rate thinning. The log viscosity‐log shear rate flow curves for each sample at the various temperatures were superimposable by linear shifts. Energies of activation calculat...


Journal of the American Oil Chemists' Society | 1956

Infrared absorption of branched-chain fatty acids and derivatives in the carbon-hydrogen stretching region

Donald L. Guertin; Stephen E. Wiberley; Walter H. Bauer

SummaryAn investigation of the lithium fluoride region makes it possible to characterize a number of structural isomers of branched-chain fatty acids. For example, 2-methyl, 3-methyl, and 5-methyl hexanoic acids may be distinguished. Similarly a number of isomers of octanoic acid may be identified ; 2-n-propyl and 2-isopropyl hexanoic acid may be differentiated. The isomers of 2-n-butyl hexanoic acid may also be identified.Absorption bands at 2960 cm−1 and 2930 cm−1 have been assigned, respectively, to asymmetrical methyl stretching modes and in-phase vibrations of the methylene group. Absorption at 2870 cm−1 is associated with symmetrical stretching modes of the methyl group. The absorption at 2860 cm−1 has been assigned to the out-of-phase vibrations of the methylene group. These assignments correspond to those of Fox and Martin and of Pozefsky and Coggeshall.The absorption bands at 2930 cm−1 and 2860 cm−1 are stronger than those at 2960 cm−1 and 2870 cm−1 when the ratio of methylene groups to methyl groups equals or exceeds three to one. The one exception to this rule is the case of 2-methyl hexanoic acid and the corresponding silver salt and di-soap. An interaction between the methyl group in the two-position and the acid group has been proposed as an explanation for this case.As the spectra of the fatty acids and their silver salt and aluminum di-soap derivatives are identical in the carbon-hydrogen region, it is obvious that other derivatives of these acids may be identified by reference to the spectra reported.


Review of Scientific Instruments | 1959

Modification of a Cone‐Plate Viscometer for Direct Recording of Flow Curves

Walter H. Bauer; Alfred P. Finkelstein; Charles A. Larom; Stephen E. Wiberley

Using a concentric‐cylinder rotational viscometer, Weltmann has shown that automatic recording of flow curves in accordance with a predetermined program is important in the study of materials whose flow properties are shear‐dependent and time‐dependent. When the flow of such materials as greases was studied using the Ferranti‐Shirley cone‐plate viscometer, advantages of small sample size, ease of loading with minimum deformation, and uniform shear rate across the sample were apparent. However, time‐dependent properties of the grease could not be adequately described from data obtained in manual operation of the cone‐plate viscometer.An automatic control device for shear rate acceleration of the cone‐plate viscometer has been designed so that flow curves can be obtained automatically using an X‐Y recorder. Flow curves of typical greases and other materials exhibiting non‐Newtonian and time‐dependent properties have been successfully obtained using this automatic control device. The cone‐plate viscometer as...


The Journal of Physical Chemistry | 1956

The Infrared Spectra of Three Aluminum Alkoxides

Donald L. Guertin; Stephen E. Wiberley; Walter H. Bauer; Jerome Goldenson


The Journal of Physical Chemistry | 1958

Flow Properties and Structure of Peptized Aluminum Soap–Hydrocarbon Gels

Walter H. Bauer; Neill Weber; Stephen E. Wiberley


The Journal of Physical Chemistry | 1956

Flow Properties of Aluminum Dilaurate–Toluene Gels

Neill Weber; Walter H. Bauer


Journal of Rheology | 1961

Yield Stresses and Flow Properties of Carboxypolymethylene‐Water Systems

William H. Fischer; Walter H. Bauer; Stephen E. Wiberley

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Stephen E. Wiberley

Rensselaer Polytechnic Institute

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Donald L. Guertin

Rensselaer Polytechnic Institute

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Alfred P. Finkelstein

Rensselaer Polytechnic Institute

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Charles A. Larom

Rensselaer Polytechnic Institute

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