Showing papers on "Elastic modulus published in 1983"

The relation between porosity, microstructure and strength, and the approach to advanced cement-based materials

Abstract: A theory is formulated to connect the strength of cement paste with its porosity. The theory shows that bending strength is largely dictated by the length of the largest pores, as in the Griffith (1920) model, but there is also an influence of the volume of porosity, which affects toughness through changing elastic modulus and fracture energy. Verification of this theory was achieved by observing the large pores in cement, and then relating bending strength to the measured defect length, modulus and fracture energy. The argument was proved by developing processes to remove the large pores from cement pastes, thereby raising the bending strength to 70 MPa. Further removal of colloidal pores gave a bending strength of 150 MPa and compression strength up to 300 MPa with improved toughness. Re-introduction of controlled pores into these macro-defect-free (mdf) cements allowed Feret’s law (1897) to be explained.

Elastic Constants of Artificial and Natural Ice Samples by Brillouin Spectroscopy

Abstract: The method of Brillouin spectroscopy has been used to measure the dynamic elastic moduli of local homogeneous regions in ice samples representing four different environments of formation. These included artificial ice frozen from distilled water, clear monocrystalline glacial ice, bubbly lake ice, and sea ice. The samples studied were found to have identical local elastic properties. Accordingly the elastic properties of homogeneous monocrystalline ice have been found not to vary with sample age, with impurities present at the time of freezing, or with crystal quality. The bulk elastic properties of ice remain, of course, subject to modification by different crystal grain textures and the presence of inclusions of various sorts. Because the elastic constants obtained in the present work are subject to smaller overall uncertainty than values measured previously, it is believed that they are the most reliable obtained to date. The values at −16 °C were determined to be c 11 = 139.29 ± 0.41, c 12 = 70.82 ± 0.39, c 13 = 57.65 ± 0.23, c 33 = 150.10 ± 0.46, c 44 = 30.14 ± 0.11 (units of 108 N m− 2 or kbar). A full range of derived elastic parameters for monocrystalline ice and for homogeneous isotropic polycrystalline ice has been calculated.

Contribution of fibrin stabilization to clot strength. Supplementation of factor XIII-deficient plasma with the purified zymogen.

Abstract: The contribution of fibrin stabilization to clot strength, measured as the static elastic modulus, was evaluated in human plasma by two independent procedures. In the first approach, amine inhibitors of fibrin stabilization were examined for their effects on the rigidity of normal plasma clots. It is a unique property of these inhibitors that they do not interfere with the reversible aggregation of fibrin molecules, i.e., do not delay clotting time, but selectively prevent only the formation of gamma-glutamyl-epsilon-lysine protein-to-protein linkages. Though the compounds tested were of different chemical structures and potencies, a fivefold reduction in clot strength was obtained in each instance. This value of 20% of normal seems to correspond to the rigidity of the Factor XIII-deficient plasma clot because, as demonstrated by the second approach, when a plasma specimen that genetically lacked the fibrin stabilizing factor was supplemented by the addition of measured amounts of the purified zymogen, a fivefold increase in clot strength could be achieved. The described procedure of evaluating Factor XIII in terms of correcting the elastic modulus of a deficient plasma clot is considered an important assay for the functional competence of purified preparations of the zymogen for the purpose of therapeutic application.

Elastic modulus in composition‐modulated copper‐nickel foils

Abstract: The biaxial elastic modulus Y[111] was measured by bulge testing on Cu‐Ni thin foils containing short‐wavelength composition modulations produced by vapor deposition. In the wavelength range of 1.3–3.0 nm, we observed a twofold increase in the modulus as compared with homogeneous foils. The increase was proportional to the square of the composition amplitude. The maximum modulus occurred at a wavelength of 1.7 nm and an average composition of 45 at. % Cu. The stress‐strain curves of the modulated foils were reversible but non‐Hookean, while homogeneous foils displayed a Hookean behavior with moduli in good agreement with those calculated from the single‐crystal elastic constants of bulk Cu‐Ni alloys.

Preparation and properties of oxynitride glasses

Abstract: Mixtures of oxides and nitrides can be melted and quenched to form glasses that contain up to 20 at % nitrogen. Adding nitrogen to an oxide glass increases its Tg, hardness, fracture toughness, elastic modulus, and chemical durability. Those changes suggest that nitrogen substitutes for oxygen in the network to produce a more highly cross-linked structure. Nitrides will be stable in oxide melts only if they are not oxidized by other components. To a first approximation, the possibility of redox reaction between a given oxide and nitride can be predicted by comparing ΔG° for the oxide with ΔG° for oxidation of the nitride. In agreement with experiment, the analysis predicts Al2O3, Li2O, CaO, Y2O3, and La2O3 will not cause decomposition in melts containing Si3N4 and SiO2, whereas K2O, Na2O, P2O5, and B2O3 will bw unstable.

Elastic properties of a single-crystal forsterite Mg2SiO4, up to 1,200 K

Abstract: Elastic moduli of forsterite were measured between 300 and 1,200 K (≃ 1.6 times the Debye temperature) by the Rectangular Parallelepiped Resonance method. All the moduli decrease regularly with temperature. A summary of the results is as follows: temperature derivatives of elastic moduli, - ∂C ij /∂R in MPa/K whereC si =(C jj +C kk −2·C jk )/4; (i, j, k=1, 2, 3;i ≠j ≠k), and ρ is density in kg/m3. These data permit for the first time the calculation of elastic and thermal properties well into the classical range far above the Debye temperature. We find, for example, that the elastic constants, including the bulk moduls, closely follow standard equations throughout the measured temperature range. This information aids extrapolations up to the melting point. This data, coupled with thermal expansivity data permit the computations of thermal anharmonic parameters of minerals forT>θ.

Elastic modulus in composition‐modulated silver‐palladium and copper‐gold foils

Abstract: The biaxial elastic modulus Y[111] has been measured by bulge testing in Ag‐Pd and Cu‐Au thin foils containing one‐dimensional composition modulations with wavelengths ranging from 0.9 to 5.5 nm. For the Ag‐Pd foils having wavelengths of 2.0–3.0 nm, the modulus was up to 2.3 times greater than that of homogeneous foils of the same average composition. The increase was found to be proportional to the square of the amplitude of the modulation. In foils containing modulations of wavelengths less than 2.0 nm or greater than 3.0 nm, the modulus was the same as that of homogeneous foils. It was observed that the deformation was elastic but non‐Hookean. For the Cu‐Au modulated foils no modulus enhancement was observed: The modulus for any wavelength was in good agreement with that calculated from the bulk elastic constants.

Elasticity and thermal expansion of a natural garnet up to 1, 000k

Abstract: High temperature mechanical properties of a natural pyrope garnet have been investigated up to 1, 000K. The elastic moduli were measured by the Rectangular Parallelepiped Resonance (RPR) method. The frequencies of the lower 16 modes smoothly decrease with temperature from 300 to 1, 000K, and so do the elastic moduli.Thermal expansion of the specimen was measured by a dilatometric method. The least squares calculation based on an equation kY2-Y+E(θE, T)/Q=0(Y is relative volume expansion, and E(θE, T) is the Debye function) yields the constants Q=16.5MJ/mol, θE=698K, and k=1.50. From these constants, the Gruneisen's parameter γ0 (=Bo Vo/Q) and the pressure derivative of bulk modulus ∂B/∂P (=2k+1) at 0K are 1.2 and 4.0, respectively.By using these data, bulk moduli and other physical properties of this garnet are estimated up to higher temperatures (Table 2).

Rheology of Fibrin Clots. VI. Stress Relaxation, Creep, and Differential Dynamic Modulus of Fine Clots in Large Shearing Deformations

Abstract: A fine, unligated clot of human or bovine fibrin prepared from purified fibrinogen is subjected to a large torsional deformation (maximum shear strain γ up to 1.37) with superposed small oscillating deformations (Δγ ca. 0.03) at frequencies from 0.2 to 1 Hz. The “secant modulus” is defined as Gi(γ)=σi/γ, where σ is stress and the subscript i refers to an initial measurement about 25 s after imposition of strain. The storage modulus G′(ω,γ) refers to a differential oscillating measurement at frequency ω superposed on a static strain γ. For γ up to about 0.1, Gi(γ) was independent of γ and equal to G′(ω,0) measured at about 1 Hz and zero static strain. At large static deformations, the differential storage modulus G′(ω,γ) could be used to monitor changes in structure. Since there is very little time dependence of the relaxation modulus in the range from 1 to 60 s, and the loss tangent is very small, Gi′(ω,γ) could be considered simply as the differential modulus Gi(γ)+γdGi/dγ, and agreed with the latter exp...

Frequency spectrum and dynamic correlations of concentrated polymer liquids

Abstract: Elastic interactions between polymer chains in concentrated liquids are incorporated into the equation of motion by adding a memory term whose kernel is related to the relaxation modulus of the system Below a characteristic chain length mechanical and dynamical properties are predicted to approach Rouse‐like behavior For long chain systems, an approximate self‐consistency condition is obtained for the dynamic viscosity in the form of a nonlinear integral equation In this limit, the mechanical spectrum is shown to split into a molecular weight independent branch separated from terminal relaxations by a wide plateau region whose elastic modulus is calculated as a function of the same parameters commonly used for the Rouse characterization of low molecular weight polymers Concentration dependences of plateau modulus, entanglement length, and transitional relaxation time are correctly predicted Zero shear viscosity and terminal relaxation time are shown to scale with the same power of the molecular weight Heuristic considerations on the viscosity exponent suggest a value of three The calculated expression of the single chain scattering function in the transition region shows a continuous change from Rouse‐like behavior to flat response with decreasing wave vector Application to multichain scattering by concentrated solutions predicts long‐time exponential behavior only above a critical scattering wavelength

Gel-like modes. of polymer solutions in « θ » solvents

Abstract: 2014 A polymer solution forms a transient network of lifetime Tr. In good solvents, the mesh size l is identical to the correlation length 03BE for the fluctuations of the monomer concentration c. But in « 03B8 » solvents (where the pair interaction vanishes), / is much smaller than 03BE. The dynamics involve then two quantitatively very different elastic moduli E : :1) at low frequencies, E = E0 = kT/03BE3 N c3 is small; 2) at higher frequencies, E = E gel kTc2 and Egel > E0. This leads to two modes in photon-beat experiments at wave vectors q larger than a certain value qg, the high frequency mode being the gel mode. Although this gives only a small fraction of the total scattered light, it still dominates the slope of the dynamical structure factor S(q, t) at small times. We investigate the corresponding diffusion coefficient D g in the three regimes : a) « many chain » regime (qg q 1/03BE), Dg ~ kT/6 03C0~s a is very high (a is a monomer size and ~s the solvent viscosity) ; b) entangled « single chain » regime (03BE-1 q l-1 ), Dg(q) ~ 1/q; c) disentangled « single chain » regime (ql > 1), Dg ~ q. The regimes b) and c) could be observed only in neutron experiments. But the cross-over from a) to b) could explain certain photon-beat results on PS in cyclohexane. J. Physique 44 (1983) 39-43 JANVIER 1983, Classification Physics Abstracts 46.60 78.35 61.12 (*) Equipe de Recherche associee au C.N.R.S. (no 542). Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphys:0198300440103900

Brillouin scattering from H 2 O: Liquid, ice VI, and ice VII

Abstract: Brillouin scattering from ${\mathrm{H}}_{2}$O under hydrostatic pressures up to 30 GPa is reported. Sound velocities in the liquid region agree with previous ultrasonic measurements and discontinuities are observed at the liquid---ice VI and ice VI---ice VII phase transitions. Elastic moduli derived from the frequency shifts are compared with bulk modulus values obtained from compressibility data.

Influence of a Tangential Force on the Fracture of Two Contacting Elastic Bodies

Abstract: The problem of fracture initiation at two elastically contacting structural components, subject to applied normal and tangential forces, was analyzed. The fracture initiation load was predicted to depend sensitively on the magnitude of the applied tangential force and the interfacial friction coefficient, and to exhibit important dependencies on the fracture toughness, elastic modulus, and curvature of the contacting bodies. Experimental results obtained on glass and Si3N4 conform with the trends predicted by the analysis.

Elastic properties of GeSbSe glasses

Abstract: The results of the measurement of transverse and longitudinal sound velocities on eigth glass compositions of the GeSbSe system are reported and their elastic moduli evaluated. While the velocities, elastic moduli and Debye temperature show variation with composition for GexSb10Se90−x glasses, they are essentially constant for the glasses with stoichiometric compositions. The dependence of bulk modulus on mean atomic volume has been analysed. Both the mean atomic volume and the type of bonding are found to be effective in determining the composition dependence of bulk modulus.

Shear elastic modulus of graphite

Abstract: The shear elastic modulus C44 of graphite has been determined by Brillouin scattering from surface waves. The author's value agrees with that obtained from neutron scattering experiments but differs from those determined by ultrasonic technique.

Elastic Moduli of Porous Sintered Materials as Modeled by a Variable-Aspect-Ratio Self-Consistent Oblate-Spheroidal-Inclusion Theory

Abstract: If the porosity of sintered materials is modeled by oblate spheroids, self-consistent elastic moduli theory can be used to determine an effective aspect ratio for the spheroids from experimental data on elastic moduli vs porosity. The resultant effective aspect ratio serves as an additional parameter to describe observed elastic behavior. With the exception of one case in the seven investigated, this single parameter satisfactorily describes both Young's modulus and shear modulus vs porosity data. The fit to these data sets is tested by comparing theoretical and experimental values for bulk moduli and Poisson ratios. An effective aspect ratio is also shown to accurately describe a continuous distribution of aspect ratios varying between spheres and disks, implying that a continuous distribution of oblate spheroids may be a useful model for the elastic behavior of sintered materials.

Modulus of Subgrade Reaction: New Perspective

Abstract: A review of the current state-of-the-art concerning the use of the modulus of subgrade reaction (Winkler) model indicates that there is considerable disagreement concerning the correct method for interpreting and evaluating the modulus of subgrade reaction, k. Extension of previous work, which used the simplified continuum approach to solve a problem in the theory of elasticity, shows that the Winkler subgrade model actually defines an elastic body of finite thickness in which all stress and strain components are assumed to be zero except for the vertical normal stress and strain. Furthermore, the modulus of subgrade reaction, k, is defined explicitly to be a function of the Young's modulus and thickness of the elastic body. Solutions for a Young's modulus that is constant with depth, as well as one that varies linearly and with the square root of depth, are presented. Although the simplified continuum approach offers an analytically rigorous and consistent method for evaluating the modulus of subgrade re...

Apparatus for protection of a substrate

Abstract: An apparatus and method for protection of a substrate, e.g. an electrical contact. The apparatus comprises a support member and an encapsulant which has a cone penetration value of 100 to 350 (10 -1 mm) and an ultimate elongation of at least 200%, and preferably an elastic modulus of less than 10' dynes/cm 2 . The encapsulant and the substrate are pressed together so that the encapsulant is deformed into close and conforming contact with the substrate. Preferably at least part of the deformation is elastic deformation.