摘要:

The energy dissipation of a cohesive soil is obtained by the Fourier transformation of stress relaxation test data. Energy dissipation is expressed in terms of the loss tangent. The soil response is nonlinear. Because of the difficulty in obtaining a mathematical expression to fit the relaxation data adequately over the entire time scale of interest, an approximate method of evaluating the transform is used. The relaxation response functions are approximated by straight line segments to form a piecewise continuous relation. By using a large number of straight line segments, the error between the actual and approximate transformation can be made negligible. The segment slopes with corresponding values of time are used in a digital computer program to evaluate the transform. The results clearly indicate a decrease of loss tangent with increased applied strain level. For constant strain level, the variation of loss tangent as a function of moisture content is not clearly defined. The loss tangent vs. logarithm of time relation gives a characteristic single peak bell‐shaped distribution for each strain level.

ISSN:0148-6055    

DOI:10.1122/1.548981

出版商:The Society of Rheology    

年代:1965

数据来源: AIP

摘要:

Constitutive relations are derived for isotropic materials in which local thermodynamic equilibrium obtains and for which the internal energy of each element depends only upon the volume and entropy of the element. The basis of the derivation is the principle that the material possesses a non‐negative entropy production function which depends upon the rates of deformation. Results include constitutive relations for viscous, plastic, and viscoplastic deformation.

ISSN:0148-6055    

DOI:10.1122/1.548982

出版商:The Society of Rheology    

年代:1965

数据来源: AIP

摘要:

A polynomial constitutive equation is given which governs the behavior of a viscoelastic solid experiencing small, time‐dependent strains superposed on large initial deformations. Through this equation, it is shown that the incremental state of stress is related to the history of incremental deformation through twelve relaxation functions, which may depend on the initial deformation. Finally, by means of direct comparison with a parallel relation obtained through thermodynamics of irreversible processes, further important restrictions on the number and character of the relaxation functions are established.

ISSN:0148-6055    

DOI:10.1122/1.548983

出版商:The Society of Rheology    

年代:1965

数据来源: AIP

摘要:

The statistical variability of ultimate properties for 8 samples of SBR‐sulfur gum vulcanizates differing in crosslink density by a factor of about 25 was studied. It is shown that these variability data, determined at one rate and one temperature, can be correlated when plotted as a reduced failure envelope. The envelope obtained in this manner agrees reasonably well with the reduced envelope previously reported which was constructed from break data obtained by testing (a) single specimens of constant crosslink density at varying rate and temperature and (b) single specimens at constant rate and temperature but varying crosslink density. It is also shown that the statistical variability data for all samples, including a benzene‐soluble one, can be represented by a double exponential cumulative distribution function. It is also shown, in agreement with previous work, that the most probable values ofσbwhen plotted as a function ofνeexhibit a maximum inσbat a low value ofνe.

ISSN:0148-6055    

DOI:10.1122/1.548984

出版商:The Society of Rheology    

年代:1965

数据来源: AIP

摘要:

This paper deals with the description of an apparatus employed for the performance of mechanical tests on specimens of 2‐phase materials. In particular, a new optical‐photoelectric method is described in some detail, which has been used for the direct measurement of deformations in the high temperature field (up to 2000°C). The strain‐time graphs obtained from isothermal short‐time creep tests of some of these materials are discussed.

ISSN:0148-6055    

DOI:10.1122/1.548985

出版商:The Society of Rheology    

年代:1965

数据来源: AIP

摘要:

The viscoelastic properties of the polyphosphoryldimethylamides were investigated by the technique of stress relaxation as a function of the N to P ratio, and therewith of the chain length. From the great similarity of the shape of the curves to those of “normal” organic polymers, i.e., poly(methyl methacrylate) or polystyrene as a function of the molecular weight, from the broad distribution of relaxation times, as well as from the difficulty of preparing samples below the gel‐point, it is concluded that the relaxation mechanism in the flow region is molecular flow, with bond interchange along the backbone either completely absent or present to only a minor extent.

ISSN:0148-6055    

DOI:10.1122/1.548986

出版商:The Society of Rheology    

年代:1965

数据来源: AIP

摘要:

Poisson's ratio was measured on a variety of plastics as a function of load up to 4000 psi by two methods. Poisson's ratio generally remained constant or decreased slightly with load. However, with crazed polyblends the ratio drastically decreased from 0.33 to 0.15 at high loads applied for long times. The low value can be explained by the growth of cracks perpendicular to the direction of the applied tensile stress. It has been shown that the lowering of the heat‐distortion temperature with stress can not be explained in terms of the lowering of the glass temperature resulting from the volume increase on application of a stress. Instead, the lowering of the softening temperature can be explained in terms of the shape of the modulus vs. temperature curve. The new theory agrees quite well with the experimental values. Materials with a broad softening range have a heat‐distortion temperature which is strongly dependent upon the load.

ISSN:0148-6055    

DOI:10.1122/1.549012

出版商:The Society of Rheology    

年代:1965

数据来源: AIP

摘要:

Melt viscosity data were obtained for linear and branched ethylene polymers over temperatures of 150 to 250°C and shear rates of about one to300 sec−1.A capillary rheometer was employed, and the appropriate corrections were made for the several sources of significant error in shear stress and shear rate. These corrected data were analyzed in terms of the Ree‐Eyring inverse hyperbolic sine relationship for viscous flow. The molecular structure was determined by infrared absorption analyses and molecular weight determinations. The rheological character of these polyethylenes was found to depend on the weight‐average length of the polymer backbone and on the branching. The major contribution to the viscosity depended on the length of the backbone and was associated with the longer relaxation times. An additional contribution to the viscosity depended on molecular segments about equal to the interbranch distance, and was associated with the shorter relaxation times. The temperature effect was found to depend on the number of the long‐chain branches, as interpreted by the reduced variable procedure applied to the shear rate.

ISSN:0148-6055    

DOI:10.1122/1.548987

出版商:The Society of Rheology    

年代:1965

数据来源: AIP

摘要:

Using the tensor‐analytic approach of Green and Zerna, an expression relating the internal pressure in an infinitely long, hollow, elastic cylinder with a thin elastic casing to the geometry of the cylinder in the strained and unstrained states, has been derived. Assumption of incompressibility is made. The strains in the elastic case are assumed to be infinitesimal, whereas, as long as they are consistent with the above requirement, no restriction is placed on the magnitude of the strains in the cylinder. The result is specialized for the case of a Mooney material for which expressions of stresses and strains in the cylinder are also presented. In the latter case, an additional restriction is placed on the magnitude of the strains in the cylinder, namely, that of being within the limits of validity of the Mooney expression for the strain energy function. The results of the analysis are applied in the solution of a practical problem, and in this case, the discrepancies between finite and infinitesimal strain theories are discussed.

ISSN:0148-6055    

DOI:10.1122/1.548988

出版商:The Society of Rheology    

年代:1965

数据来源: AIP

摘要:

We define random media as certain stochastic processes and consider briefly the question of whether a consistent subfamily of distribution functions can be extended to obtain a stochastic process characterizing a random medium. We define and discuss the “statistical geometry” of “two‐phase” random media and “symmetric” random media. We also review certain aspects of random subdivisions of space into crystals, radiation scattering from particulate assemblies such as random packings of rigid spheres and percolation processes in random crystals and random networks.

ISSN:0148-6055    

DOI:10.1122/1.548989

出版商:The Society of Rheology    

年代:1965

数据来源: AIP