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71.
72.
定围压比作用下混凝土轴向受压性能试验研究 总被引:2,自引:0,他引:2
通过对混凝土施加围压,使单轴受压混凝土的裂缝发展受到限制,从而研究混凝土在接近无裂纹发展状态(无损伤产生的理想状态)下的受压性能。本文在MTS815.02岩石电液伺服系统上完成了三轴应力比σ1∶σ2∶σ3=(-α)∶(-α)∶(-1)(α=0.15,0.18,0.19,0.20,0.22)作用下的混凝土单调、循环加卸载受压的常规三轴试验。研究了不同围压比对混凝土受压应力-应变关系的影响规律,以及围压对混凝土裂缝发展的限制作用,得出了一些与同类试验不同的结果,混凝土理想无损伤发展状态的受压应力-应变关系曲线被提出,并通过试验首次研究了理想无损伤发展状态下的混凝土循环加卸载的应力-应变关系,系统地分析了围压对混凝土受压性能的影响规律。 相似文献
73.
74.
Ryosuke Yanai 《Journal of Dispersion Science and Technology》2017,38(1):40-45
To study the effect of hydrophobic modification of the emulsifier on the relationship between emulsion stability and polymer emulsifier concentration, silicone oil emulsions were prepared using hydroxypropyl methylcellulose (original HPMC) and HPMC stearoxy ether (hydrophobic HPMC) at concentrations around their overlap concentrations. Both HPMC types completely emulsified the silicone oil. However, the volume fraction of silicone oil in the emulsion prepared using hydrophobic HPMC was less than that that by the original HPMC, and the average oil droplet size in the former emulsion was less than that in the latter emulsion. Increasing HPMC concentration led to increase in both the amount of adsorbed polymer emulsifier and the storage moduli in the linear region, irrespective of which HPMC was used. Stress-strain sweep curves obtained by a rheo-optical method showed that emulsions stabilized by the hydrophobic HPMC flowed slowly, even beyond the yield stress, whereas emulsions prepared using the original HPMC flowed quickly beyond the yield stress. The storage moduli of the emulsions prepared by the hydrophobic HPMC were larger than those prepared using the original HPMC. 相似文献
75.
High-molecular weight polybutadiene chains having approximately 47% cis-1,4 units and 45% trans-1,4 units were crosslinked through their carbon-carbon double bonds using p-bis(dimethylsilyl) benzene as crosslinking agent and chloroplatinic acid as catalyst. This particular polymer was chosen because the high plateau modulus it exhibits in the un-crosslinked state is taken to indicate large numbers of chain entanglements, and stress–strain measurements on such networks have frequently been interpreted with the assumption that the trapping of such entanglements during crosslinking should contribute significantly to their modull. It is shown in the present investigation that such results are equally well interpreted in terms of the new constrained-chain theory of rubbery elasticity. © 1993 John Wiley & Sons, Inc. 相似文献
76.
S. Giordano P. L. Palla L. Colombo 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,68(1):89-101
We investigate the elastic properties of model composites, consisting in a dispersion of nonlinear (spherical or cylindrical)
inhomogeneities into a linear solid matrix. Both phases are considered isotropic. Under the simplifying hypotheses of small
deformation for the material body and of small volume fraction of the embedded phase, we develop a homogenization procedure
based on the Eshelby theory, aimed at describing nonlinear features. We obtain the bulk and shear moduli and Landau coefficients
of the overall material in terms of the elastic behavior of the constituents and of their volume fractions. The mixing laws
for the nonlinear properties describe a complex scenario where possible strong amplifications of the nonlinearities may arise
in some given conditions. 相似文献
77.
We investigate the Green function of two-dimensional dense random packings of grains in order to discriminate between the
different theories of stress transmission in granular materials. Our computer simulations allow for a detailed quantitative
investigation of the dynamics which is difficult to obtain experimentally. We show that both hyperbolic and parabolic models
of stress transmission fail to predict the correct stress distribution in the studied region of the parameters space. We demonstrate
that the compressional and shear components of the stress compare very well with the predictions of isotropic elasticity for
a wide range of pressures and porosities and for both frictional and frictionless packings. However, the states used in this
study do not include the critical isostatic point for frictional particles, so that our results do not preclude the fact that
corrections to elasticity may appear at the critical point of jamming, or for other sample preparation protocols, as discussed
in the main text. We show that the agreement holds in the bulk of the packings as well as at the boundaries and we validate
the linear dependence of the stress profile width with depth. 相似文献
78.
T. Lachhab C. Weill 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,9(1):59-69
Mechanical properties of packings of deformable spheres of polyelectrolyte gel are studied experimentally. These particles
are plunged into a brine. They have the property to swell and shrink when the concentration of salt of the solution is varied.
An oedometric compression is performed imposing cycles of deformation at constant speed and constant salinity Cs. Under many different conditions, we study the laws of deformation relating the macroscopic compression force F, to the macroscopic strain . We find empirical non linear relations of the type . The values of this exponent m are discussed and compared to the results of measurements on a single sphere compressed on
a plane as well as to the results of experiments and simulations on dry model granular assemblies. The swelling and deswelling
properties of the spheres are used to perform isotropic compression tests. In this situation we determine the relation between
the force at equilibrium and the macroscopic strain . The results are compared with those obtained in the oedometric compression tests.
Received 27 January 1998 相似文献
79.
A commercial 1-octene LLDPE, Dowlex 2045, was cross-fractionated by dynamic direct extraction and subsequent solution crystallization. Two solution fractions of molecular massM
of about 37 000 and 120 000 were selected for second fractionation by crystallization in xylene at temperatures of 80°, 65°, 50° and 21°C. From the cross fractions thin films were pressed at high temperature and then cooled either in air to room temperature or in a quenching bath to –18°C. From these films small rectangular samples were cut and stretched at room temperature. The stress-strain curves, indicating inhomogeneous drawing, show two characteristic points, A and B, of local curvature maximum. The corresponding yield stresses, A and B, were evaluated, and their dependence on structural parameters as molar mass and comonomer content, as well as on cooling rate, affecting the morphology, is discussed. 相似文献
80.
Waleed E. Mahmoud S.A. Mansour M. Hafez M.A. Salam 《Polymer Degradation and Stability》2007,92(11):2011-2015
Acrylonitrile butadiene rubber (NBR) compounds filled with 40 phr of high abrasion furnace black (HAF) and HAF (20 phr)/graphite (20 phr) were experimentally investigated. The stress-strain curves of the composites were studied, which are described by applying Ogden's model. The effect of cyclic fatigue and hysteresis was also examined. The dissipation energy that indicates the vibration damping capacity for all samples was determined. A continuum damage model is used to investigate the fatigue damage behavior for elastomers. Experiments on the cyclic fatigue of a carbon-filled NBR rubber and carbon/graphite filled NBR rubber were conducted to determine the relation between the number of cyclic fatigue and the strain amplitude. The results indicate that the theoretical formula for the number of cyclic fatigue as a function of the strain amplitude, derived from the damage model, can describe experimental data for the prepared samples very well. 相似文献