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1.
Ir. H. A. Waterman 《Rheologica Acta》1969,8(1):22-38
Summary The propagation of elastic waves (both longitudinal and transverse) through polyurethane rubbers filled with different amounts
of sodium chloride particles was studied at 0.8 MHz and 5 MHz. At a constant filler concentration (∼10% by volume), the velocity
of these waves appeared to be independent of filler size. On the other hand, both velocities were found to increase with filler
content. From the wave velocities, the effective modulus for longitudinal waves, L, bulk modulus, K, and shear modulus, G,
were calculated according to the relations for a homogeneous isotropic material. All three moduli appear to be monotonically
increasing functions of filler content, c, over the whole experimentally accessible temperature range (−80°C to +80°C for
L and K; −80°C to about −30°C for G) and they, moreover, reflect the glass-rubber transition of the binder. Poissons ratio,
μ, was found to decrease with increasing filler content and shows a rise at about −30°C as a result of the approach of the
glass-rubber transition.
The attenuation of the elastic waves was also measured in the temperature ranges mentioned. For filler particles beyond a
critical size both tan δL and tan δG in the hard region are independent of the filler content within the accuracy of the measurements. The critical size depends
on the type of wave and on its frequency. In the rubbery region, however, tan δL increases with particle size (at a constant content of 10% by volume) and even shows an enhancement with the smallest particles
(1–5 μ) at 0.8 MHz. Moreover, it is found that for the same filler size tan δL increases with filler content. In some cases an anomalous damping behaviour was found, such that in the rubbery region the
attenuation rises indefinitely with temperature. For filler particles larger than the above-mentioned critical size, tan δG and tan δL increase in the hard region as well. Finally, the experimental results are compared with existing theories on the elastic
properties of and wave propagation through composite media. 相似文献
2.
E. V. Karpov 《Journal of Applied Mechanics and Technical Physics》2009,50(1):163-169
This paper gives the results of an experimental study of the deformation and fracture of a spheroplast under uniaxial low-cycle
loading (compression and unloading) at a temperature T = 25 and 100°C. Various mechanisms of damage accumulation at various temperatures and degrees of damage to the material are studied. The
experimental results are compared with the well-known dependences taking into account damage accumulation for metals. It is
established that the basic propositions of these theories are suitable for the low-cycle fracture of spheroplast — a ductile
material of complex structure.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 50, No. 1, pp. 197–204, January–February, 2009. 相似文献
3.
A. I. Usmanov 《Fluid Dynamics》1998,33(3):351-354
The dependence of the flow coefficient of a gas jet ejected from an orifice/nozzle into a subsonic/transonic cross-flow on
the flow and the jet Mach numbers, the off-design ratio, the nozzle inclination angle, β, and other determining parameters
is considered. The physical nozzle flow pattern is constructed on the basis of experimental data obtained for 0.3< M∞<1.75 and β=60°, 90°, and 120°. The results of measuring the pressure upstream and downstream of the orifice and on the windward
and leeward orifice generators are presented. It is shown that the flow rate coefficient of a jet ejected into a cross-flow
may exceed that of a similar jet outflowing into a flooded space.
Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 3, pp. 65–70, May–June, 1998. 相似文献
4.
The effect of temperature on the interfacial tension for PS/PMMA, PS/PE, and PMMA/PE was measured using the imbedded fiber
retraction method. Interfacial tensions for PS/PMMA, PS/PE, and PMMA/PE were measured over temperature ranges of 160–250 °C,
140–220 °C, and 140–220 °C, respectively. The interfacial tension was found to follow a dependence of 3.6–0.013 T dyn/cm, 7.6–0.051 T dyn/cm and 11.8–0.017 T dyn/cm for PS/PMMA, PS/PE, and PMMA/PE, respectively. Comparison of the data with the mean field theory of Helfand and Sapse
were made; however, a simple linear fit to the data described the temperature dependence in the experimental window as well
as the predictions of the mean field theory.
Received: 6 July 1999 Accepted: 23 March 2000 相似文献
5.
A. A. Klopotov Yu. A. Timoshnikov É. V. Kozlov N. A. Koneva 《Journal of Applied Mechanics and Technical Physics》1999,40(3):545-548
Results of studies of structural and mechanical properties ofNi
3
Fe alloy are presented. The densities and types of dislocations in the alloy, the parameters of dislocation interaction, and
the energy expended in deformation ofNi
3
Fe specimens in various initial states are estimated. The strain hardening behavior of orderedNi
3
Fe alloy is shown to be influenced by a number of external factors, such as deformation or γ-irradiation.
Tomsk State Architectural University, Tomsk 634003. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 40,
No. 3, pp. 211–215, May–June, 1999. 相似文献
6.
Two-phase CFD calculations, using a Lagrangian model and commercial code Fluent 6.2.16, were employed to calculate the gas
and droplet flows and film cooling effectiveness with and without mist on a flat plate. Two different three dimensional geometries
are generated and the effects of the geometrical shape, size of droplets, mist concentration in the coolant flow and temperature
of mainstream flow for different blowing ratios are studied. A cylindrical and laterally diffused hole with a streamwise angle
of 30° and spanwise angle of 0° are used. The diameter of film cooling (d) hole, and the hole length to diameter ratio (L/d) for both of geometries are 10 mm and 4, respectively. Also the blowing ratio ranges from 1.0 to 2.0, and the mainstream
Reynolds number based on the mainstream velocity and hole diameter (Re
d) is 6,219. The results are shown for different droplets diameters (1–10 μm), concentrations (1–5%) and mainstream temperatures
(350–500 K). The centreline effectiveness and distribution of effectiveness on the surface of cooling wall are presented. 相似文献
7.
V. M. Kulik 《Journal of Applied Mechanics and Technical Physics》2007,48(2):221-228
The longitudinal and transverse components of deformation of the surface of a flat layer of a viscoelastic material glued
onto a solid base under the action of a traveling pressure wave are determined. The coating compliance is described by two
components corresponding to two components of surface displacement. The dimensionless compliance components depend only on
the viscoelastic properties of the material, the ratio of the wave length to the layer thickness λ/H, and the ratio of the
wave velocity to the velocity of propagation of shear oscillations V/C
t
0
. Data on the dynamic compliance are presented for 0.3 < λ/H < 30 and 0.1 < V/C
t
0
< 10. The compliance is demonstrated to be determined by its absolute value and by the phase lag of strain from pressure.
The effect of viscous losses in the material and compressibility of the latter on the dynamic compliance is analyzed. An anomalous
behavior of the compliance with the wave velocity being greater than a certain critical value is explained.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 2, pp. 90–97, March–April, 2007. 相似文献
8.
We found a solution of an unsteady two-dimensional heat conduction equation in a functionally gradient material (FGM) which
is subjected to a double thermal shock, namely, a local heating of a specimen by a power laser beam and cooling of a heated
surface by a water-air spray. We developed an analytical method whereby a coating is described as a laminated plate composed
of n layers with the constant material properties within a layer. Temperature distribution in a nonhomogeneous laminated plate
is obtained in a form of series using the Laplace–Hankel integral transforms. In order to extend the model of a laminated
plate to describe FGM where thermal physical characteristics are continuous functions of spatial coordinate, we considered
the limiting case of the obtained temperature distribution when the thickness of the layer iΔ
i
→ 0, and the number of layers n→∞. This allowed us to obtain the temperature distribution in an easy-to-use analytical form which can be used for determining
thermal stresses in FGM. The dependence of the temperature distribution in FGM on the operating parameters of a double thermal
shock method, e.g., a duration of heating, laser beam radius, the rate of a spray cooling, is discussed.
Received on 3 May 1999 相似文献
9.
The imbedded-fiber retraction (IFR) method was used to study the effect of temperature and PDMS molecular weight on the interfacial
tension of PS/PDMS blends. The interfacial tension decreased with increasing temperature and analysis of the temperature dependence
using a simple linear fit gave –dγ/dT value of 0.058±0.010 dyn/cm-deg. Reported –dγ/dT values of PS/PDMS blends are highly
dependent on the molecular weights of the polymers and can have values that are <0, 0, or >0. Our interfacial tension values
were independent of the molecular weight of PDMS and this was attributed to the molecular weights studied here being well
above the entanglement values of both polymers. However, analysis of interfacial tension data from this work and the literature
showed the following empirical relationship between apparent blend molecular weight, Mb, and interfacial tension of PS/PDMS blends with a correlation of 0.94: γ12=γ0+k2Mb
(–2/3), where γ0=7.3±0.3 dyn/cm; k2=–517±41 (dyn/cm)(g/mol)2/3. 相似文献
10.
This study presents an experimental investigation of the large plastic deformation of poly(ethylene terephthalate) (PET) submitted to plane strain compression. PET samples, obtained by injection moulding, annealed and non-annealed, were deformed using a specific compression device developed for this purpose. The obtained stress–strain curves at different temperatures and strain rates are useful for engineering applications and show a significant temperature dependence and a minor dependence on the strain rate. A softening temperature as a minimum temperature necessary to initiate deformation when a minimum, almost zero, stress is applied is introduced. This temperature, at the zero stress and strain limit, we denominate “Stress–Strain independent softening Temperature (T
SOF)”. The T
SOF values, 104 and 113°C for non-annealed and annealed PET, respectively, have been obtained using three different strain rates, indicating that the property is sensitive to the thermal history of the material. 相似文献
11.
V. V. Garannikov V. G. Zubchaninov N. L. Okhlopkov 《International Applied Mechanics》2000,36(7):961-968
The constitutive relations of the complanarity hypothesis are used to construct an image of the process of loading of 9×2
steel for a plane deformation.astroid-type trajectory, which is realized in the plain Э1-Э3 of the deviator subspace of Il'yushin's deformation. The laws governing changes in the scalar and vector properties of the
material are considered. The computed results are compared with experimental data obtained on a CH-DC computer-aided system.
State Technical University, Tver', Russia. Translated from Prikladnaya Mekhanika, Vol. 36, No. 7, pp. 130–136, July,2000. 相似文献
12.
13.
The purpose of this study is to investigate the effects of various bimodal pore size distributions of biporous wicks for a
loop heat pipe (LHP). The study was conducted following a statistical method using a two-level factorial plan involving three
variables (particle size of pore former:74–88 and 125–149 μm Na2CO3, pore former content:20% by volume and 25% by volume, sintering temperature:700 and 750°C). Finally, the heat transport capability
of the LHP between monoporous wicks and biporous wicks has been investigated. Experimental results show that, at the sink
temperature of 10°C and the allowable evaporator temperature of 80°C, the heat transfer capacity of the better biporous wick
achieved 200 W and the total thermal resistance was 0.31°C/W. The performance is enhanced about 60%, compared to a monoporous
wick for 125 W and 0.53°C/W. Therefore, LHPs with biporous wicks are very attractive for high heat flux applications in the
future. 相似文献
14.
Edward T. Kopesky Stephen G. Boyes Neil Treat Robert E. Cohen Gareth H. McKinley 《Rheologica Acta》2006,45(6):971-981
Two distinct oligomeric species of similar mass and chemical functionality (M
w≈2,000 g/mol), one a linear methyl methacrylate oligomer (radius of gyration R
g≈1.1 nm) and the other a hybrid organic–inorganic polyhedral silsesquioxane nanocage (methacryl-POSS, r≈1.0 nm), were subjected to thermal and rheological tests to compare the behaviors of these geometrically dissimilar molecules over the entire composition range. The glass transition temperatures of the blends varied monotonically between the glass transition temperatures of the pure oligomer (T
g=−47.3°C) and the pure POSS (T
g=−61.0°C). Blends containing high POSS contents (with volume fraction φ
POSS≥0.90) exhibited enhanced enthalpy relaxation in differential scanning calorimetry (DSC) measurements, and the degree of enthalpy relaxation was used to calculate the kinetic fragility indices m of the oligomeric MMA (m=59) and the POSS (m=74). The temperature dependences of the viscosities were fitted by the free-volume based Williams–Landel–Ferry (WLF) and Vogel–Fulcher–Tammann (VFT) framework and a dynamic scaling relation. The calculated values of the fragility from the WLF–VFT fits were similar for the POSS (m=82) and for the oligomer (m=76), and the dynamic scaling exponent was similar for the oligomeric MMA and the POSS. Within the range of known fragilities for glass-forming liquids, the temperature dependence of the viscosity was found to be similarly fragile for the two species. The difference in shape of the nanocages and oligomer chains is unimportant in controlling the glass-forming properties of the blends at low volume fractions (φ
POSS<0.20). However, at higher volume fractions, adjacent POSS cages begin to crowd each other, leading to an increase in the fractional free volume at the glass transition temperature and the observed enhanced enthalpy relaxation in DSC. 相似文献
15.
Angel Romo-Uribe Maraolina Domínguez-Díaz Maria Eugenia Romero-Guzmán Leonardo Rejón Rubén Saldivar-Guerrero 《Rheologica Acta》2009,48(2):201-215
This research investigates the influence of monomer composition on the thermal transitions, mi crostructure, and viscoelastic
properties of thermotro pic liquid crystalline polymers (LCPs) based on 1, 4-hydroxy-benzoic acid (B) and 2,6-hydroxy-naphthoic
acid (N). Compositions B–N of 1:1, 1:3, 3:1, and 2:1 mol% were studied. The solid-to-nematic transition T
s→n was greatly influenced by the monomer composition, ranging from 230 to 280 °C. However, the decomposition temperature T
dec was independent of composition, all the materials degrading at T
dec = 509 °C. Polarized optical microscopy showed a threaded texture in the nematic phase. Fiber X-ray diffraction showed aperiodic
meridional maxima for all LCPs, the number of maxima depended on composition. B–N 3:1 and 1:3 mol% favor the orthorhombic
crystallographic phase whereas the 1:1 and 2:1 mol% crystallized in a pseudohexagonal phase. Dynamic time sweeps showed that
the nematic phases are stable at the temperatures studied. Strain sweeps showed the existence of a linear viscoelastic (LVE)
regime. The LVE properties ranged from predominantly viscous (G′ < G″) for the 1:1 mol% composition to predominantly elastic (G′ > G″) and with a well-defined rubber-like regime for the 1:3 mol% composition, resembling the rheology of flexible polymer melts.
The persistence length q appears to be the parameter driving the rheological behavior.
相似文献
Angel Romo-UribeEmail: |
16.
Jalil Moghadasi Fakhri Yousefi Mohammad Mehdi Papari Mohammad Ali Faghihi Ali Asghar Mohsenipour 《Heat and Mass Transfer》2009,45(11):1453-1466
It is the purpose of this paper to extract unlike intermolecular potential energies of five carbon dioxide-based binary gas
mixtures including CO2–He, CO2–Ne, CO2–Ar, CO2–Kr, and CO2–Xe from viscosity data and compare the calculated potentials with other models potential energy reported in literature. Then,
dilute transport properties consisting of viscosity, diffusion coefficient, thermal diffusion factor, and thermal conductivity
of aforementioned mixtures are calculated from the calculated potential energies and compared with literature data. Rather
accurate correlations for the viscosity coefficient of afore-cited mixtures embracing the temperature range 200 K < T < 3273.15 K is reproduced from the present unlike intermolecular potentials energy. Our estimated accuracies for the viscosity
are to within ±2%. In addition, the calculated potential energies are used to present smooth correlations for other transport
properties. The accuracies of the binary diffusion coefficients are of the order of ±3%. Finally, the unlike interaction energy
and the calculated low density viscosity have been employed to calculate high density viscosities using Vesovic–Wakeham method. 相似文献
17.
Experimental studies on drag reduction and rheology of mixed cationic surfactants with different alkyl chain lengths 总被引:2,自引:0,他引:2
Zhiging Lin Lu Chou Bin Lu Yi Zheng H. Ted Davis L. E. Scriven Y. Talmon Jacques L. Zakin 《Rheologica Acta》2000,39(4):354-359
Experimental studies of the effects of mixtures of cationic surfactants on their drag reduction and rheological behaviors
are reported. Cationic alkyl trimethyl quaternary ammonium surfactants with alkyl chain lengths of C12 and C22 were mixed at different molar ratios (total surfactant concentrations were kept at 5 mM with 12.5 mM sodium salicylate (NaSal)
as counterion). Drag reduction tests showed that by adding 10% (mol) of C12, the effective drag reduction range expanded to 4–120 °C, compared with 80–130 °C with only the C22 surfactant. Thus mixing cationic surfactants with different alkyl chain lengths is an effective way of tuning the drag reduction
temperature range. Cryo-TEM micrographs revealed thread-like micellar networks for surfactant solutions in the drag reducing
temperature range, while vesicles were the dominant microstructures at non-drag reducing temperatures. High extensional viscosity
was the main rheological feature for all solutions except 50% C12 (mol) solution, which also does not show strong viscoelasticity. It is not clear why this low extensional viscosity solution
with relatively weak viscoelasticity is a good drag reducer.
Received: 3 November 1999/Accepted: 5 January 2000 相似文献
18.
An experimental investigation was carried out to study the enhancement of the heat transfer from a heated flat plate fitted
with rectangular blocks of 1 × 2 × 2 cm3 dimensions in a channel flow as a function of Reynolds number (Reh), spacing (S
y
) of blocks in the flow direction, and the block orientation angle (α) with respect to the main flow direction. The experiments were performed in a channel of 18 cm width and 10 cm height, with
air as the working fluid. For fixed S
x
=3.81 cm, which is the space between the blocks in transverse to the flow direction, the experimental ranges of the parameters
were S
y
=3.33–4.33 cm, α=0–45°, Reh=7625–31550 based on the hydraulic diameter and the average velocity at the beginning of the test section in the channel.
Correlations for Nusselt number were developed, and the ratios of heat transfer with blocks to those with no blocks were given.
The results indicated that the heat transfer could be enhanced or reduced depending on the spacing between blocks, and the
block orientation angle. The maximum heat transfer rate was obtained at the orientation angle of 45°.
Received on 13 December 2000 / Published online: 29 November 2001 相似文献
19.
The process of contact melting of the solid phase change material (PCM) around a hot sphere, which is driven by the temperature
difference between the PCM and the sphere, is analyzed in this paper. Considering the difference of the normal angle between
the sphere surface and the solid–liquid interface of the melting PCM, the fundamental equations of the melting process are
derived with the film theory. The new film thickness and pressure distribution inside the liquid film and the variation law
of the normal angle of the solid–liquid interface and the melting velocity of the sphere are also obtained. It is found that
(1) while normal angle at sphere surface φ is within a certain value φ0, which is related to Ste number and the outside force F, it has no obvious effect on the pressure distribution inside the liquid film and the numerical results by the present model
are in accordance with the analytical results in the published literature, (2) the film thickness at φ = ±90° is constringent
to a certain value and not the infinity, (3) the analytical results can be employed approximately to analyze the contact melting
process except for the film thickness at φ = ±90°. 相似文献
20.
Kenneth R. Meyer Patrick McSwiggen Xiaojie Hou 《Journal of Dynamics and Differential Equations》2010,22(3):367-380
The search for traveling wave solutions of a semilinear diffusion partial differential equation can be reduced to the search
for heteroclinic solutions of the ordinary differential equation ü − cu̇ + f(u) = 0, where c is a positive constant and f is a nonlinear function. A heteroclinic orbit is a solution u(t) such that u(t) → γ
1 as t → −∞ and u(t) → γ
2 as t → ∞ where γ
1, γ
2 are zeros of f. We study the existence of heteroclinic orbits under various assumptions on the nonlinear function f and their bifurcations as c is varied. Our arguments are geometric in nature and so we make only minimal smoothness assumptions. We only assume that
f is continuous and that the equation has a unique solution to the initial value problem. Under these weaker smoothness conditions
we reprove the classical result that for large c there is a unique positive heteroclinic orbit from 0 to 1 when f(0) = f(1) = 0 and f(u) > 0 for 0 < u < 1. When there are more zeros of f, there is the possibility of bifurcations of the heteroclinic orbit as c varies. We give a detailed analysis of the bifurcation of the heteroclinic orbits when f is zero at the five points −1 < −θ < 0 < θ < 1 and f is odd. The heteroclinic orbit that tends to 1 as t → ∞ starts at one of the three zeros, −θ, 0, θ as t → −∞. It hops back and forth among these three zeros an infinite number of times in a predictable sequence as c is varied. 相似文献