共查询到20条相似文献,搜索用时 906 毫秒
1.
A. I. Beyle C. G. Gustafson V. L. Kulakov Yu. M. Tarnopol'skii 《Mechanics of Composite Materials》1997,33(5):403-414
Prospects for the application of advanced composites in the offshore technology of oil production are considered. The use of composites in vertical pipelines-risers seems to be the most efficient. The operating loads are studied and the attendant problems are formulated. A comparative analysis of the characteristics of metal, composite, and metal-composite deep-water risers is presented. A technique is developed for designing multilayered risers, taking into account the action of internal and external pressures, gravity, and the axial tensile force created by tensioners, as well as the residual technological stresses due to the difference in coefficients of thermal expansion, physical-chemical shrinkage, and force winding. Numerical estimations are given for a two-layered riser with an inner metal layer of steel, titanium, or aluminum alloys and a composite layer of glass- or carbon-fiber plastics formed by circumferential winding. It is shown that the technological stresses substantially affect the characteristics of the riser.Institute of Polymer Mechanics, Latvian Academy of Sciences, Riga, LV-1006, Latvia. Trondheim Technical University, Norway. Translated from Mekhanika Kompozitnykh Materialov, Vol. 33, No. 5, pp. 577–591, September–October, 1997. 相似文献
2.
An anisotropic medium is considered in which, upon loading, scattered microdamages accumulate giving rise to nonlinear and
residual strains. The damage at a point of the medium is characterized by a scalar function on a unit sphere, referred to
as the damage function. This function is approximated by a fourth-rank tensor used for specifying the relation between the
increments of strains and stresses. The calculation dependences are presented in detail for a unidirectional composite, which
is taken to be a homogeneous transversely isotropic medium. Determination of the unknown constants is illustrated by the example
of an actual fiberglass plastic.
Institute of Polymer Mechanics, University of Latvia, Riga, LV-1006, Latvia. Translated from Mekhanika Kompozitnykh Materialov,
Vol. 35, No. 5, pp. 561–574, September–October, 1999. 相似文献
3.
The dependence of physical and mechanical properties of monolithic and foamed rigid polyurethanes on the content of flame
retardants was investigated at 293 and 98 K. The character of the influence of the content of trichloroethyl phosphate on
the ultimate tensile elongation and the coefficient of linear thermal expansion for monolithic and foamed polyurethanes at
a temperature of 98 K was established.
Latvian State Institute of Wood Chemistry, Riga, LV-1006 Latvia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 35,
No. 5, pp. 671–676, September–October, 1999. 相似文献
4.
A. A. Skudra 《Mechanics of Composite Materials》1996,32(5):463-466
An empirical approach is proposed for assessing the influence of the synergistic effect on the increase in strength and the
strain limit of a cement matrix at the moment of formation of the first crack.
Riga Technical University, Riga, LV-1047, Latvia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 32, No. 5, pp. 663–667,
September–October, 1996. 相似文献
5.
An attempt is made to find a solution by which the effect of neighboring filler particles on the strength of composites could
be indirectly estimated. The stresses in composites with a great amount of filler are calculated. Composites based on epoxy-resin
binder are tested. A comparison of different models shows that the modified Kerner model reflects only the tendency for the
compression strength to change with the degree of filling. The relations between the compression strength and the degree of
filling are better described by models allowing for constraint of the plastic deformations of the matrix. However, in this
case, the effect of the neighboring particles is not properly taken into account.
Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 5, pp. 575–584, September–October, 1999. 相似文献
6.
We show how the Gabriel–Roiter measure, introduced by Ringel in (Bull Sci Math 129:726–748, 2005 and Contemp Math 406:105–135, 2006), applies to indecomposable modules of finite length over right pure semisimple rings, and in particular to the study of
the open problem whether any right pure semisimple ring is of finite representation type.
Dedicated to the memory of Andrey Vladimirovich Roiter. Professor A. V. Roiter has died on 26 July 2006 in Riga, Latvia. He
was born in 1937. 相似文献
7.
R. A. Kayumov 《Mechanics of Composite Materials》1999,35(5):409-418
Laminated nonthin shells made of nonlinearly elastic fiber composites are considered. The composite material is assumed to
be transversely isotropic in planes perpendicular to reinforcement. The asymptotic method and the condition of material stability
are applied to analyze the structure of constitutive relations. To introduce a small parameter, the high stiffness in the
reinforcement direction of the fiber composite is used. This allows us to obtain simplified constitutive relations containing
functions with one or two arguments instead of five as in the initial general case.
Kazan State Architectural Building Academy, Tatarstan, Russia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 35,
No. 5, pp. 615–628, September–October, 1999. 相似文献
8.
The thermal conductivity of epoxy composites containing not only the traditional fillers quartz, talc, carbon black, and aerosil,
but also the very promising carbon nanomaterials is investigated. Two kinds of carbon nanomaterials — multi-wall (MWNT) and
single-wall (SWNT) carbon nanotubes — were considered. The influence of their content (from 0.05 to 3.0 wt.%) on the thermal
conductivity of MWNT-epoxy composites was studied. The thermal conductivity of epoxy composites was examined in the temperature
range from −150 to 150°C. It was found that the introduction of 0.1–1.0 wt.% MWNT enhanced the thermal conductivity of pure
epoxy resin by about 40%. A further increase in content of the nanotubes decreased the thermal conductivity. This can be explained
by the worsening of nanotube dispersion at their high concentrations. The maximum growth in the thermal conductivity of the
epoxy composites, on the entire range of temperatures considered, was observed at a 0.1 wt.% content of MWNT.
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 44, No. 1, pp. 117–126, January–February, 2008. 相似文献
9.
Christopher M. Pastore 《Mechanics of Composite Materials》2000,36(2):97-116
For several decades researchers have been interested in textile processes for the production of composite reinforcement. These
technologies have offered several promises: reduced fabrication costs, 3-D multiaxial reinforcement, and damage tolerance.
Despite these advantages, textile composites have not reached the level of implementation of laminated composites. In this
paper, the opportunities provided by textile reinforced composites and the challenges that limit their implementation will
be discussed in detail. Textile composites refer to a family of processes: weaving, braiding, knitting, and hybrids thereof.
The various families of textiles will be defined and the basics of fabric formation for each family will be detailed. In particular,
the strengths and weaknesses of each manufacturing technique will be addressed to provide a view of the applicability of each
technology. This will include some guidance on shape formation capability, property ranges, size limitations, and estimates
of cost to produce. Potential applications for these materials will be presented. Among the limitations on the application
of textile reinforced composites is the lack of adequate modeling capabilities for these materials. Textile composites have
rather large unit cell structures and are highly inhomogeneous throughout their volumes. These features provide benefits in
manufacturing, but require novel modeling techniques to correctly understand the mechanical behavior. A review of analytical
techniques applied to textile composites will be presented along with a discussion of the benefits and weaknesses of each
of these methods. The enabling technologies needed to further the implementation of textile composites in structural applications
will be discussed.
Submitted to the 11th International Conference on Mechanics of Composite Materials (Riga, June 11–15, 2000).
Published in Mekhanika Kompozitnykh Materialov, Vol. 36, No. 2, pp. 165–194, March–April, 2000. 相似文献
10.
Yu. L. Ershov 《Algebra and Logic》1999,38(1):12-20
It is established that in each uniformly small Δ*–group, there exists a closed system of representatives; moreover, it turns
out that every narrow epimorphism onto a projective Δ*–group splits. (These properties are violated in a class of all Δ*–group).
Translated fromAlgebra i Logika, Vol. 38, No. 1, pp. 24–39, January–February, 1999. 相似文献
11.
An example is given to show that the necessary conditions of Theorem 4.5 [in Chen et al. Math Methods Oper Res 49:239–253, 1999] and Theorem 2.1 (i) [in Goh and Yang Eur J Oper Res 116:615–628, 1999] for (weak) vector equilibrium flows may not hold. New ξ-equilibrium and parametric equilibrium flows are introduced. As a result, necessary and sufficient conditions between a weak vector equilibrium flow and an ξ-equilibrium flow and between a vector equilibrium flow and a parametric equilibrium flow are established. 相似文献
12.
Yu. A. Gorbatkina 《Mechanics of Composite Materials》2000,36(3):169-176
The relationship between the strength (σc) of unidirectional fiber-reinforced plastics in different stressed states and the interfacial strength of their components
is investigated. The shear adhesive strength (τ0) of fiber—matrix joints determined by the pull-out technique is used as a measure of the interfacial strength. To obtain
the correlation curves betweenσc andτ0, the experimental results are used, where both the plastic and adhesive strength change under the influence of a single factor.
In this case, such factors are the fiber surface treatment, nature and composition of polymer matrices, and test temperature.
It is shown that the strength of the glass, carbon, and boron plastics increases practically linearly with increased interfacial
strength. Such a behavior is observed in any loading conditions (tension, shear, bending, and compression). Sometimes, a small
(10–20%) increase in the adhesive strength induces a significant (50–70%) growth in the material strength. Therefore, the
interface is the “weak link” in these composites. The shape of theσc—τ0 curves for composites based on the high-strength and high-modulus aramid fibers and different thermoreactive matrices depends
on the nature of the fiber and the type of stress state. In many cases, the composite strength does not depend on the interfacial
strength. Then, the fiber itself is the “weak link” in these composites.
Submitted to the 11th International Conference on Mechanics of Composite Materials (Riga, June 11–15, 2000).
Translated from Mekhanika Kompozitnykh Materialov, Vol. 36, No. 3, pp. 291–304, May–June, 2000. 相似文献
13.
V. A. Goldade 《Mechanics of Composite Materials》1998,34(2):107-114
Data are given on the effect of an electret charge on wetting, spreading, sorption, and diffusion of liquids in polymers and composites. The modification of polymers in electric fields or by electret and electrochemically active fillers improves the physical-mechanical and tribological characteristics of materials. It is shown that the electret composites used in machines for protecting the metal-polymer joints against corrosion increase their rigidity and tightness and improve their tribological characteristics. Electret composites are new-generation materials (smart or intelligent materials) since they respond to recent developments in technology and are capable of raising the efficiency of machines with simultaneous reduction in energy and consumption of materials.Submitted to the 10th International Conference on Mechanics of Composite Materials, April 20–23, 1998, Riga, Latvia.Belyi Metal-Polymer Research Institute, National Academy of Sciences, Gomel 246652, Belarus. Translated from Mekhanika Kompozitnykh Materialov, Vol. 34, No. 2, pp. 153–162, March–April, 1998. 相似文献
14.
A method for determining the stiffness and rheological characteristics of composite materials, based on minimizing the mismatch
of experimental data and the results of numerically modeling nonstationary deformation processes in shells ofrevolution made
of composites materials, is presented. This approach is used for analyzing the damping characteristics of chaotically reinforced
and cloth-reinforced composites.
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 43, No. 4, pp. 449–464, July–August, 2007. 相似文献
15.
S. Minkevičius 《Lithuanian Mathematical Journal》1999,39(3):273-283
The paper continues the article by the author on functional limit theorems in queuing systems under heavy traffic. Theorems
are proved for the virtual process of serving jobs when at phases of the queuing system various conditions of heavy traffic
are satisfied (compound transient phenomena).
Institute of Mathematics and Informatics, Akademijos 4, 2600 Vilnius, Lithuania. Translated from Lietuvos Matematikos Rinkinys,
Vol. 39, No. 3, pp. 343–356, July–September, 1999.
Translated by Z. Kryžius 相似文献
16.
An epoxy resin (Epon 828) was filled with single- and multiwalled carbon nanotubes (SWCNT and MWCNT) in two steps by using
the high shear mixing and ultrasonication techniques. The melt flow of the composites was characterized in a plate/plate rheometer.
The thermomechanical properties of the composites were determined in dynamic mechanical analysis tests performed at various
frequencies and temperatures. It was found that the incorporation of SWCNT or MWCNT increased the viscosity and stiffness
of epoxy above its glass-transition temperature. The time-temperature superposition principle was employed to estimate the
storage modulus of the composites as a function of frequency (f = 10–33–103 Hz) in the form of master curves. 相似文献
17.
Two approaches to the study of the stability of gently curved laminate structures are developed. The first approach is based
on the analytical separation of variables. In the second approach, a polynomial approximation over the transverse coordinate
is assumed. The loss of stability of such structures with various contact conditions for layers is examined.
For Report 1, see Mech. Compos. Mater.,35, No. 4, 285–292 (1999).
Ukrainian Transport University, Kiev, Ukraine. Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 5, pp. 643–652,
September–October, 1999. 相似文献
18.
A. Kviklys 《Mechanics of Composite Materials》2000,36(2):143-148
An analytical relationship between the thermooxidation rate constants and mechanical properties of composite materials under
isothermal and dynamic conditions is obtained. With the example of epoxy-based composites, it is shown that the kinetic parameters
of thermooxidation can be used to predict the internal stresses and breakdown voltage of coatings. The calculated drop in
the impact toughness exceeds its experimental value by 30%, while the calculated relative breaking elongation is 1.5–2 times
greater than the experimental one. A considerable decrease in these indices is observed at a loss of 0.1–1 wt.% of volatile
products of thermooxidation.
Submitted to the 11th International Conference on Mechanics of Composite Materials (Riga, June 11–15, 2000).
Translated from Mekhanika Kompozitnykh Materialov, Vol. 36, No. 2, pp. 237–248, January–February, 2000. 相似文献
19.
D. D. Zakharov 《Mechanics of Composite Materials》1999,35(5):403-408
An asymptotic analysis of the dynamic stress-strain state of a thin laminar packet of anisotropic layers is presented. The
statement is nonclassical, since in layer materials the ratio of elastic moduli in the longitudinal and transverse directions
can generate small parameters comparable to the relative half-thickness of the packet, as, for example, in high-strength unidirectional
composites. Alternation of strong load-carrying layers and a relatively soft filler with a similar difference in the elastic
moduli between the layers is also allowed. The averaged two-dimensional equations and the total stress tensor in the layers
are determined. The results are classified with respect to the types of anisotropy and the indices of differences in the elastic
moduli. It is shown that first-approximation models lead to kinematic relations similar to those of the theories of high-order
shear strains.
Institute of Problems of Mechanics, Russian Academy of Sciences, Moscow, Russia. Translated from Mekhanika Kompozitnykh Materialov,
Vol. 35, No. 5, pp. 605–614, September–October, 1999. 相似文献
20.
We use a method recently devised by Bolle to establish the existence of an infinite number of solutions for various non-homogeneous
boundary value problems. In particular, we consider second order systems, Hamiltonian systems as well as semi-linear partial
differential equations. The non-homogeneity can originate in the equation but also from the boundary conditions. The results
are more satisfactory than those obtained by the standard “Perturbation from Symmetry” method that was developed – in various forms – in the early eighties by Bahri–Berestycki, Struwe and Rabinowitz.
Received: 13 August 1998 / Revised version: 6 July 1999 相似文献