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1.
A model of nonassociated plasticity is put forward for initially isotropic materials deforming with residual changes in volume
under the action of triaxial normal stresses. The model is based on novel plastic loading and plastic potential functions,
which define closed, convex, every where smooth surfaces in the 6D space of symmetric second-rank stress tensors. By way of
example, the plastic deformation of a cylindrical concrete specimen wrapped with a CFRP tape and loaded in axial compression
is described.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 44, No. 2, pp. 183–194, March–April, 2008. 相似文献
2.
The applicability range of toughness-and strength-based criteria for progressive cracking of a transverse layer in a cross-ply
composite laminate subjected to tensile loading is considered. Using a deterministic cracking model, approximate relations
for the crack density as a function of stress are derived for initiation-and propagation-controlled types of cracking. The
master-curve approach is applied to progressive cracking in glass/epoxy laminates. The accuracy of estimation of laminate
stiffness reduction by using crack density master curves is evaluated.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 44, No. 5, pp. 633–646, September–October, 2008. 相似文献
3.
Xiaoqing Yan Shurong Ding J. W. Tong M. Shen Z. Huo 《Mechanics of Composite Materials》2009,45(3):293-302
A thermoplastic angle-ply AS4/PEEK laminate with a hole is considered. The interlaminar stresses along the hole edge at different
interfaces under uniaxial extension are investigated. According to the symmetries of the structure and loading, a suitable
finite-element model is developed. Utilizing a three-dimensional elastic-plastic finite-element procedure elaborated previously,
a finite-element modeling of the interlaminar stresses in a thick angle-ply composite laminate is carried out. Based on the
interlaminar stresses obtained, the dangerous locations of delamination initiation are predicted. The results obtained indicate
that there is some relationship between the dangerous locations and fiber orientations in the adjacent layers, and it maybe
inferred that the critical locations are near the regions where the hole edge is tangent to the fiber orientation in the layers
adjacent to the interface. The interlaminar stresses at the same interfaces are not sensible to distances from the midplane
of the laminate. Very high interlaminar tensile stresses are found to exist on the hole edge at the +25°/+25° or –25°/–25°
interfaces, and delaminations can initiate there first.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 45, No. 3, pp. 427-440, May-June, 2009. 相似文献
4.
C. Soutis 《Mechanics of Composite Materials》2007,43(1):51-58
Cohesive-zone models have been successfully applied to predicting the damage from notches in engineering materials loaded
intension. They have also been used to determine the growth of fibre microbuckling from a hole in a composite laminate under
compression. The usual strategy is to replace the in elastic deformation associated with plasticity or microbuckling with
a line crack and to assume some form of stress-displacement bridging law across the crack faces. This paper examines recent
published experimental data for notched glass-fibre epoxy/honey comb sand wich panels loaded in uniaxial compression. A plastic
fibre kinking analysis and a linear softening cohesive-zone model are used for the prediction of the unnotched and open-hole
compressive strength and the theoretical results are found to be in a good agreement with experimental data.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 43, No. 1, pp. 73–84, January–February, 2007. 相似文献
5.
The structural situation of corners of a laminate reinforcement patch can cause singularities in the mechanical in-plane fields
due to the geometry and different material properties in the reinforced and nonreinforced domains, respectively. In the present
study, an asymptotic analysis of the cross-sectional force fields near the corners of a laminate reinforcement patch is performed.
Using the complex potential method based on Lekhnitskii’s approach, the mechanical in-plane fields at a two-dimensionally
modeled interface corner can be determined in a closed-form manner. Various configurations of interface corners are examined,
and their effect on the singular characteristics of the cross-sectional force field is studied. In particular, the size effect
of the reinforcement patch is considered.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 43, No. 3, pp. 319–338, May–June, 2007. 相似文献
6.
The paper presents a theoretical-numerical hybrid method for determining the stresses distribution in composite laminates
containing a circular hole and subjected to uniaxial tensile loading. The method is based upon an appropriate corrective function
allowing a simple and rapid evaluation of stress distributions in a generic plate of finite width with a hole based on the
theoretical stresses distribution in an infinite plate with the same hole geometry and material. In order to verify the accuracy
of the method proposed, various numerical and experimental tests have been performed by considering different laminate lay-ups;
in particular, the experimental results have shown that a combined use of the method proposed and the well-know point-stress
criterion leads to reliable strength predictions for GFRP or CFRP laminates with a circular hole.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 43, No. 4, pp. 531–570, July–August, 2007. 相似文献
7.
O. G. Gurtovyi 《Mechanics of Composite Materials》2000,36(3):193-198
A phenomenological yield condition for quasi-brittle and plastic orthotropic materials with initial stresses is suggested.
All components of the yield tensor are determined from experiments on uniaxial loading. The reliability estimates of the criterion
suggested is discussed. For a plastic material without initial stresses, the given condition transforms into the Marin—Hu
criterion. The defining equations of the deformation theory of plasticity with isotropic and “anisotropic” hardening, associated
with the yield condition suggested, are obtained. These equations are used as the basis for a highly accurate nonclassical
continuous model for nonlinear deformation of thick sandwich plates. The approximations with respect to the transverse coordinate
take into account the flexural and nonflexural deformations in transverse shear and compression. The high-order approximations
allow us to model the occurrence of layer delamination cracks by introducing thin nonrigid interlayers without violating the
continuity concept of the theory.
Submitted to the 11th International Conference on Mechanics of Composite Materials (Riga, June 11–15, 2000).
Translated from Mekhanika Kompozitnykh Materialov, Vol. 36, No. pp. 329–340, May–June, 2000. 相似文献
8.
V. A. Kolupaev S. Kolling A. Bolchoun M. Moneke 《Mechanics of Composite Materials》2007,43(3):245-258
The tightening of industrial safety standards for structures generates a need for refined computational methods, which, among
other things, must be able to describe the yield surface and the deformation behaviour of non-reinforced thermoplastics. To
describe the plastic behaviour of materials, a potential formulation is suggested. This formulation contains a number of known
potentials as special cases. The parameters of the model, which are obtained from test data, are restricted by the convexity
condition for the potential. The new model allows one to take into account effects of the second order, for instance, the
unequal behaviour under tension and compression, the plastic compressibility, and the Poynting-Swift effect. For each particular
choice of the parameters, the Poisson ratio in tension is computed. If the restrictions imposed on the Poisson ratio do not
hold, the application of a non-associated flow rule is necessary. A simple non-associated flow rule with different values
of Poisson ratio intension and compression is proposed.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 43, No. 3, pp. 367–384, May–June, 2007. 相似文献
9.
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
10.
In this study, the effects of repeated loads on the FRP-concrete bond strength were investigated experimentally by direct
pull out tests according to CSA S806-02. A conventional reinforcing steel bar and two types of glass-fiber-reinforced plastic
(GFRP) bars were embedded in concrete and tested under four different loading patterns. The bond strength–slip curves of the
bars were obtained and analyzed. The results showed that the maximum bond strengths under the repeated loads differed from
those obtained under monotonic ones. In addition, noticeable differences in degradation of the bond strength with respect
to the magnitude of slip were observed between the different bar types tested. On the basis of an image analysis of failure
surfaces, they were attributed to the different bond failure mechanisms associated with the steel and GFRP bars. 相似文献
11.
M. Yu. Shvaiko 《Journal of Mathematical Sciences》2011,176(4):548-560
We have proposed a modification of the methods for solving the system of integral equations [M. Ya. Leonov and N. Yu. Shvaiko,
“Complex plane deformation,” Dokl. Akad. Nauk SSSR,
159, No. 2, 1007–1010 (1964); N. Yu. Shvaiko, “On the theory of slip with smooth and singular loading surfaces,” Mat. Metody Fiz.-Mekh. Polya,
48, No. 3, 129–137 (2005)]. These equations describe the development of plane plastic deformation for simple and complex loading
processes. A characteristic feature of these equations lies in the presence of unknown functions both under the integral sign
and in the integration limits. We have written analytical solutions for monotone deformation and in a small neighborhood of
an angular point of the loading trajectory. For arbitrary piecewise smooth trajectories, we have reduced this problem to the
Cauchy problem for a first-order differential equation with known initial conditions. The results obtained simplify significantly
the construction of constitutive equations [(s)\dot]mn ~ [(e)\dot]mn {\dot{\sigma }_{mn}} \sim {\dot{\varepsilon }_{mn}} and their use in applied problems of the theory of plasticity as compared with [N. Yu. Shvaiko, “On the theory of slip with smooth and singular loading surfaces,” Mat. Metody Fiz.-Mekh. Polya,
48, No. 3, 129–137 (2005); N. Yu. Shvaiko, Complex Loading and Problems of Stability [in Russian], Izd. DGU, Dnepropetrovsk (1989)]. 相似文献
12.
The macroscopic mechanical behavior of many materials crucially depends on the formation and evolution of their microstructure. In this work, we consider the formation and evolution of laminate deformation microstructure in plasticity. Inspired by work on the variational modeling of phase transformation [5] and building on related work on multislip gradient crystal plasticity [9], we present a new finite strain model for the formation and evolution of laminate deformation microstructure in double slip gradient crystal plasticity. Basic ingredients of our model are a nonconvex hardening potential and two gradient terms accounting for geometrically necessary dislocations (GNDs) by use of the dislocation density tensor and regularizing the sharp interfaces between different kinematically coherent plastic slip states. The plastic evolution is described by means of a nonsmooth dissipation potential for which we propose a new regularization. We formulate a continuous gradient-extended rate-variational framework and discretize it in time to obtain an incremental-variational formulation. Discretization in space yields a finite element formulation which is used to demonstrate the capability of our model to predict the formation and evolution of laminate deformation microstructure in f.c.c. Copper with two active slip systems in the same slip plane. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
13.
Based on the example of a toroidal membrane, a model for calculating the winding trajectory and the shape of a shell billet
and its transformation into given surface elements, as well as for calculating the shape of the membrane under an internal
pressure loading, is developed. The problem of choosing optimum design variables and manufacturing parameters of the membrane
is also investigated.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 2, pp. 147–164, March–April, 2006. 相似文献
14.
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
15.
A. N. Anoshkin A. A. Tashkinov A. F. Larionov A. B. Pospelov 《Mechanics of Composite Materials》2000,36(3):241-248
A high-performance, corrosion-resistant biplastic pipe for high-pressure oil pipeline systems is presented. The pipe combines
an outer load-carrying layer formed from unidirectionally glass-reinforced plastic (GRP) sublayers by wet multi-circuit winding
and an inner sealing layer of high-density polyethylene. Both demountable and permanent joints, tees, and other parts are
constructed for these pipes. The biplastic pipes ensure reliable operation of oil pipeline systems under a pressure of up
to 200 bar. The experimental results and calculated estimates of the strength of biplastic pipes are presented. The results
of using these pipes in oil pipeline systems in the Perm’ region are discussed.
Presented at the 11th International Conference on Mechanics of Composite Materials (Riga, June 11–15, 2000).
Translated from Mekhanika Kompozitnykh Materialov, Vol. 36, No. 3, pp. 407–418, 2000. 相似文献
16.
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
17.
S. Conti D. Faraco F. Maggi S. Müller 《Calculus of Variations and Partial Differential Equations》2005,24(4):479-493
We construct a function on the space of symmetric 2× 2 matrices in such a way that it is convex on rank-one directions and
its distributional Hessian is not a locally bounded measure. This paper is also an illustration of a recently proposed technique
to disprove L1 estimates by the construction of suitable probability measures (laminates) in matrix space. From this point of view the novelty
is that the support of the laminate, besides satisfying a convex constraint, needs to be contained on a rank-three line, up
to arbitrarily small errors.
Mathematics Subject Classification (2000): 35J50 – 26D15 – 49N60 –74G65 相似文献
18.
The intralaminar fracture toughness of a unidirectionally reinforced glass/epoxy composite is determined experimentally at
several mode I and mode II loading ratios. The crack propagation criterion, expressed as a quadratic form in terms of single-mode
stress intensity factors (alternatively, linear in terms of energy release rates), approximates the test results reasonably
well. The mixed-mode cracking criterion obtained is used to predict the intralaminar crack on set in a cross-ply glass/epoxy
composite under off-axis tensile loading.
Translated from Mekhanika Kompozitnykh Materialov, Vol. 44, No. 6, pp. 785–794, November–December, 2008. 相似文献
19.
I. J. Gnip S. A. Veyelis V. I. Kersulis S. I. Vaitkus 《Mechanics of Composite Materials》2007,43(1):85-94
Data obtained in investigating the ultimate strength and deformability of expanded polystyrene under short-term shear loading
according to EN 12090 are discussed. Linear regression equations are used for describing the ultimate shear strength and modulus
in relation to the density of EPS. A correlation is found to exist between the ultimate strength of EPS and its density and
specimen thickness. An empirical dependence between the shear modulus and density of EPS is established. The strains corresponding
to the conditional limit of proportionality and to the ultimate shear strength of EPS in short-term loading are determined.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 43, No. 1, pp. 121–134, January–February, 2007. 相似文献
20.
The mechanical properties of unidirectional GFRPs based on an ED-22 epoxy resin were investigated. The resin was modified
with a PSK-1 polysulphone or a PEF-3a epoxyurethane oligomer. Triethanolaminotitanate or diaminodiphenilsulphone was used
as a hardener. The modification did not improve the mechanical properties of GFRPs in quasi-static loading; but in a low-speed
impact loading, the shear strength of epoxypolysulphone GFRPs with 20 wt.% PSK-1 increased by 20–25%. For all the GFRPs investigated,
the shear strength grew linearly with the logarithm of loading rate. The introduction of the modifiers increased the fracture
toughness considerably: by 100 and 70% for GFRPs modified with 20 wt.% PSK-1 and 50 wt.% PEF-3a, respectively.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 6, pp.739–758, November–December, 2006. 相似文献