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101.
Electric fields in the rheology of disperse systems 总被引:3,自引:0,他引:3
In the present survey, the influence of electric fields on the structure and rheological properties of disperse systems as well as the effect of deformations on their electrical characteristics are discussed. The properties of these systems are considered in terms of the dielectric permittivity and electrification potential. The considerable thickness of the double electric layer around the disperse phase particles, which is characteristic of disperse systems with nonpolar hydrocarbon dispersion media, provides the possibility for strong electric fields to produce an electric nonuniformity on the surface of the disperse phase particles. The formation of hydrate layers on the particles creates the possibility of polarization of the disperse phase. In plastic disperse systems such as greases, a strong orientation effect is observed, which contributes to the creation of frozen flow patterns when the flow is suddenly stopped. The survey is concluded with a consideration of the process of formation of chain structures in the direction of the lines of force of the electric field whose orientation is normal to the direction of flow, which can lead to complete stoppage of the flow. 相似文献
102.
The shapes of shear body waves in periodically inhomogeneous, magnetostrictive, dielectric media are studied with emphasis
on the partial (elastic and magnetostrictive) wave motions coupled to produce magnetoelastic waves
__________
Translated from Prikladnaya Mekhanika, Vol. 42, No. 7, pp. 57–63, July 2006. 相似文献
103.
We demonstrate the ability to determine stress intensity factors in orthotropic materials directly from measured temperatures
away from the crack and using far-field expressions for the stresses. This is advantageous, recognizing that recorded thermoelastic
data can be very unreliable near the tip of a crack. In addition to singular terms that govern in the immediate vicinity of
the crack tip, the present series expressions for the stresses contain higher-order finite terms. Little measured input information
is needed and data acquisition positions can be selected largely at the user's discretion. 相似文献
104.
The work is devoted to the problem of plane monochromatic longitudinal wave propagation through a homogeneous elastic medium
with a random set of spherical inclusions. The effective field method and quasicrystalline approximation are used for the
calculation of the phase velocity and attenuation factor of the mean (coherent) wave field in the composite. The hypotheses
of the method reduce the diffraction problem for many inclusions to a diffraction problem for one inclusion and, finally,
allow for the derivation of the dispersion equation for the wave vector of the mean wave field in the composite. This dispersion
equation serves for all frequencies of the incident field, properties and volume concentrations of inclusions. The long and
short wave asymptotics of the solution of the dispersion equation are found in closed analytical forms. Numerical solutions
of this equation are constructed in a wide region of frequencies of the incident field that covers long, middle, and short
wave regions of propagating waves. The phase velocities and attenuation factors of the mean wave field are calculated for
various elastic properties, density, and volume concentrations of the inclusions. Comparisons of the predictions of the method
with some experimental data are presented; possible errors of the method are indicated and discussed. 相似文献
105.
106.
107.
石墨对铜基自润滑材料高温摩擦磨损性能的影响 总被引:21,自引:4,他引:21
通过基体多元合金化和选用不同粒度的石墨颗粒,采用常规粉末冶金方法制备了铜基石墨固体自润滑材料,在大越式OAT-U型摩擦磨损试验机上考察了复合材料从室温到500℃温度条件下的摩擦磨损性能,利用扫描电子显微镜观察分析磨损表面形貌,进而探讨其摩擦磨损机理.结果表明:在室温条件下,石墨颗粒越小,则复合材料的摩擦系数越小,减摩自润滑效果越好;在室温至500℃条件下,选用合适的石墨粒度(0.3~0.5mm)和多元基体合金化,可使铜基石墨固体自润滑材料保持较好的自润滑特性. 相似文献
108.
稀土处理玻璃纤维填充聚四氟乙烯复合材料在油润滑下的摩擦学性能 总被引:4,自引:3,他引:4
分别用偶联剂、稀土以及偶联剂 -稀土混合物处理玻璃纤维表面 ,以改善玻璃纤维与聚四氟乙烯之间的界面结合力 ,考察了玻璃纤维填充聚四氟乙烯复合材料在油润滑下的摩擦学性能 .结果表明 :在油润滑条件下 ,表面处理玻璃纤维填充聚四氟乙烯复合材料的摩擦系数比未经处理玻璃纤维填充聚四氟乙烯复合材料的低 ,耐磨性亦较优 ;而稀土处理玻璃纤维填充聚四氟乙烯复合材料具有最低的摩擦系数及最高的耐磨性和极限 pv值 ;未经处理玻璃纤维填充聚四氟乙烯复合材料的磨损形式主要为粘着转移 ,偶联剂处理玻璃纤维填充聚四氟乙烯复合材料和偶联剂与稀土处理玻璃纤维填充聚四氟乙烯复合材料均以磨粒磨损为主 ,而稀土处理玻璃纤维填充聚四氟乙烯复合材料的磨损机理主要为粘着磨损和轻微磨粒磨损 相似文献
109.
Short duration stress pulses are of particular interest in determining the interfacial crack tip instability criteria for
the dynamic fracture behavior of laminated carbon-fiber/epoxy composites. However, the heterogeneous architectures of laminated
composites can alter the characteristics of a stress pulse as it propagates toward a crack tip. This makes it difficult to
use standard dynamic testing techniques for characterizing these materials, since these techniques assume the characteristics
of the stress pulse do not change as a result of propagation and can therefore be unambiguously determined from impact conditions.
This paper presents a novel experimental technique that has been developed for characterizing short duration stress pulse
propagation in laminated composite materials. In this technique, a dynamic moiré interferometer is used to capture fringe
patterns corresponding to displacement fields associated with short duration stress pulses that were generated by impacting
0° and 90°/0°/90° carbon-fiber/epoxy composites with a magnetic flyer plate. Appropriate dynamic testing conditions for capturing
high fidelity fringe patterns were determined using the recently developed dynamic moiré fringe contrast factor. The effects
of the composite architecture on the propagation of short duration stress pulses observed with the dynamic moiré interferometer
were confirmed by transient dynamic finite element analysis. From comparisons of experimental and numerical data, it was determined
that the impact conditions for the magnetic flyer plate and laminated composite will not necessarily be planar, which has
a significant effect on the intensity and duration of the propagating stress pulse. 相似文献
110.
纤维复合材料的弹粘塑性行为体分比与应变率的影响 总被引:1,自引:0,他引:1
利用微观力学方法研究了纤维增复合材料的弹塑性行为,着重分析了纤维体分比和加载应变率对以金属基为主的复合材料应力-应变关系的影响。给出了不同体分比的Graphite/Titanium复合材料在不同常应变率下的应力-应变关系曲线,对这两种因素的影响进行了比较分析。 相似文献