共查询到20条相似文献,搜索用时 0 毫秒
1.
J. Rosti L.I. Salminen E.T. Seppälä M.J. Alava K.J. Niskanen 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(2):259-263
We study the statistics of crack pinning in two dimensions by experiments and simulations of directed polymers in random media.
Mode I tensile tests on paper samples show a delocalization phenomenon as the notch length is varied if the fraction of cracks
pinned to the notch is monitored. This is compared with the behavior of directed polymers in the presence of both an energetically
favorable localized pinning center and bulk disorder. An analysis of the crack interface roughness indicates self-affine behavior
with a roughness exponent ζ in the proximity of the minimum energy surface value 2/3.
Received 4 April 2000 and Received in final form 10 October 2000 相似文献
2.
F. Kun S. Zapperi H.J. Herrmann 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(2):269-279
We introduce a continuous damage fiber bundle model and compare its behavior with that of dry fiber bundles. Several interesting
constitutive behaviors, such as plasticity, are found in this model depending on the value of the damage parameter and on
the form of the disorder distribution. We compare the constitutive behavior of global load transfer models, obtained analytically,
with local load transfer models numerical simulations. The evolution of the damage is studied analyzing the cluster statistics
for dry and continous damage fiber bundles. Finally, it is shown that quenched random thresholds enhance damage localization.
Received 27 March 2000 相似文献
3.
Y. Couder L. Pauchard C. Allain M. Adda-Bedia S. Douady 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(2):135-138
The veins of plant leaves exhibit a large variety of morphologies. They are often thought to result from their growth in a
concentration scalar field. It is shown here that the topology of these patterns rather corresponds to what is expected from
growth in a tensorial stress field. This is demonstrated by analogic experiments performed on crack formation in gel films
where many characteristic venation patterns, of both dicotyledons and monocotyledons, were reproduced. This suggests, for
the origin of the veins formation, a set of hypotheses which is new but supported by known physiological data.
Received 11 March 2002 Published online 19 July 2002 相似文献
4.
K. Ivanova 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(2):327-330
The two-dimensional Ausloos et al. model of fluid invasion, freezing and thawing in a porous medium is elaborated upon and investigated in order to take into
account the pore volume redistribution and conservation during freezing. The results are qualitatively different from previous
work, since the damaged pore sizes are found to be much less than the possible maximum value and is reached after a large
number of invasion-freezing-thawing cycles, e.g. the material is “slowly damaged”. The pore size distribution is thus found in better agreement with expected practical findings.
The successive invasion percolation clusters are still found to be self-avoiding with aging. The cluster size decreases with
a power law as a function of invasion-frost-thaw iterations. The aging kinetics is also discussed through the normalized totally
invaded pore volume.
Received 24 September 1999 and Received in final form 5 January 2000 相似文献
5.
I.L. Menezes-Sobrinho J.G. Moreira A.T. Bernardes 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(2):313-318
We study the existence of distinct failure regimes in a model for fracture in fibrous materials. We simulate a bundle of parallel
fibers under uniaxial static load and observe two different failure regimes: a catastrophic and a slowly shredding. In the
catastrophic regime the initial deformation produces a crack which percolates through the bundle. In the slowly shredding
regime the initial deformations will produce small cracks which gradually weaken the bundle. The boundary between the catastrophic
and the shredding regimes is studied by means of percolation theory and of finite-size scaling theory. In this boundary, the
percolation density scales with the system size L, which implies the existence of a second-order phase transition with the same critical exponents as those of usual percolation.
Received 24 June 1999 相似文献
6.
A. Guarino S. Ciliberto A. Garcimartın M. Zei R. Scorretti 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(2):141-151
The acoustic emission of fracture precursors, and the failure time of samples of heterogeneous materials (wood, fiberglass)
are studied as a function of the load features and geometry. It is shown that in these materials the failure time is predicted
with a good accuracy by a model of microcrack nucleation proposed by Pomeau. We find that the time interval δt between events (precursors) and the energy ɛ are power law distributed and that the exponents of these power laws depend
on the load history and on the material. In contrast, the cumulated acoustic energy E presents a critical divergency near the breaking time τ which is E∼
. The positive exponent γ is independent, within error bars, on all the experimental parameters.
Received 31 July 2001 and Received in final form 17 December 2001 相似文献
7.
A. Guarino A. Garcimartín S. Ciliberto 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,6(1):13-24
The statistical properties and the localization of fracture precursors on heteregeneous materials is studied by recording
their acoustic emission as a function of the applied load. It's found that the microcrack cluster together as the load increases
and the instantaneous acoustic energy has an invariant power law distribution. The integrated acoustic energy presents a critical
divergency close to the failure load for the sample. These result support the idea that fracture can be viewed as a critical
phenomenon. Finally a measure of the concentration of microcraks, which allows us to predict the failure load, is introduced.
These properties are studied also when a periodic load is applied to the sample. It's found that the Kaiser effect is not
strictly satisfied in heteregeneous materials.
Received: 23 January 1998 / Revised: 20 April 1998 / Accepted: 17 June 1998 相似文献
8.
A. Bershadskii 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(2):323-327
It is shown that localized instabilities can be an origin of log-normal and power-law statistical distributions in fracture,
fragmentation and island growth processes. Results of laboratory experiments and numerical simulations performed by different
authors are used to demonstrate the applicability of this approach.
Received 2 September 1999 相似文献
9.
J. A. Åström 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,56(4):291-295
A set of 3873 cracks on exposed granite rock surfaces are analyzed
in order to investigate possible fracture mechanisms. The fracture patterns
are compared with the Mohr-Coulomb and the Roscoe fracture models,
which can be combined into a single fracture scheme. A third model
for comparison is based on interacting `penny-shaped' micro cracks introduced
by Healy et al. [Nature 439, 64 (2006)]. The former models predict a bimodal
fracture angle distribution, with two narrow peaks separated by
60○-90○ symmetrically on both sides of the direction of the
largest principal stress, while the latter
predicts a single broader peak in the same direction
with standard deviation in the range 15○-20○.
The crack length distributions seem consistent with numerical simulation,
whereas the fracture patterns are Euclidean rather than fractal.
The statistical analyses indicate that none of the models
fully describe the fracture patterns. It seems that natural shear
fractures easily become a complex combination of different fracture mechanisms. 相似文献
10.
S. Zapperi H.J. Herrmann S. Roux 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(1):131-136
We simulate the propagation of a planar crack in a quasi-two dimensional fuse model, confining the crack between two horizontal
plates. We investigate the effect on the roughness of microcrack nucleation ahead of the main crack and study the structure
of the damage zone. The two-dimensional geometry introduces a characteristic length in the problem, limiting the crack roughness.
The damage ahead of the crack does not appear to change the scaling properties of the model, which are well described by gradient
percolation.
Received 29 March 2000 相似文献
11.
Within mean field approximation, a procedure is elaborated to consider noise induced phase transitions with arbitrary relations
between the noises of different degrees of freedom. The proposed approach is applied to investigate effects of cross correlation
between noises in the generalized synergetic model of Lorenz type. This cross correlation is shown to induce phase transitions
of the dynamical system under consideration. Additionally, we find the correlation between noises transforms a synergetic
behavior to a thermodynamic one.
Received 13 November 2002 Published online 11 April 2003
RID="a"
ID="a"e-mail: dikh@sumdu.edu.ua 相似文献
12.
I.M. Sokolov 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,22(3):369-373
We consider two-particle dispersion in a velocity field, where the relative two-point velocity scales according to v
2(r) ∝r
α and the corresponding correlation time scales as τ(r) ∝r
β, and fix α = 2/3, as typical for turbulent flows. We show that two generic types of dispersion behavior arize: For α/2 +
β < 1 the correlations in relative velocities decouple and the diffusion approximation holds. In the opposite case, α/2 +
β > 1, the relative motion is strongly correlated. The case of Kolmogorov flows corresponds to a marginal, nongeneric situation.
In this case, depending on the particular parameters of the flow, the dispersion behavior can be rather diffusive or rather
ballistic.
Received 13 March 2001 相似文献
13.
We study the low-velocity (0.1-100 μm s-1) frictional properties of interfaces between a rough glassy polymer and smooth silanized glass, a configuration which gives
direct access to the rheology of the adhesive joints in which shear localizes. We show that these joints exhibit the full
phenomenology expected for confined quasi-2D soft glasses: they strengthen logarithmically when aging at rest, and weaken
(rejuvenate) when sliding. Rejuvenation is found to saturate at large velocities. Moreover, aging at rest is shown to be strongly
accelerated when waiting under finite stress below the static threshold.
Received 20 February 2002 and Received in final form 16 May 2002 相似文献
14.
A new and general approach is proposed to analyze the dynamics of a colloidal particle interacting with a nearby wall. This
analysis can be used to determine the acting forces even when the system is non-stationary. As an illustration, we use total
internal reflection microscopy to investigate the forces acting on a polystyrene sulfate latex particle as it is receding
from a charged glass surface.
Received 10 October 2002 Published online: 16 April 2003
RID="a"
ID="a"Present address: Department of Polymer Physics, BASF Aktiengesellschaft, 67056 Ludwigshafen, Germany
RID="b"
ID="b"Present address: Arryx. Inc., Chicago, IL 60601, USA 相似文献
15.
M. Romeo V. Da Costa F. Bardou 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(4):513-525
The lognormal distribution describing, e.g., exponentials of Gaussian random variables is one of the most common statistical distributions in physics. It can exhibit
features of broad distributions that imply qualitative departure from the usual statistical scaling associated to narrow distributions.
Approximate formulae are derived for the typical sums of lognormal random variables. The validity of these formulae is numerically
checked and the physical consequences, e.g., for the current flowing through small tunnel junctions, are pointed out.
Received 8 November 2002 / Received in final form 17 March 2003 Published online 7 May 2003 相似文献
16.
S. Aumaître S. Fauve S. McNamara P. Poggi 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(3):449-460
We consider three examples of dissipative dynamical systems involving many degrees of freedom, driven far from equilibrium
by a constant or time dependent forcing. We study the statistical properties of the injected and dissipated power as well
as the fluctuations of the total energy of these systems. The three systems under consideration are: a shell model of turbulence,
a gas of hard spheres colliding inelastically and excited by a vibrating piston, and a Burridge-Knopoff spring-block model.
Although they involve different types of forcing and dissipation, we show that the statistics of the injected power obey the
“fluctuation theorem" demonstrated in the case of time reversible dissipative systems maintained at constant total energy,
or in the case of some stochastic processes. Although this may be only a consequence of the theory of large deviations, this
allows a possible definition of “temperature" for a dissipative system out of equilibrium. We consider how this “temperature"
scales with the energy and the number of degrees of freedom in the different systems under consideration.
Received 26 June 2000 and Received in final form 24 October 2000 相似文献
17.
Solomon Fekade Mulugeta Bekele 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(3):369-374
We analyze the relaxation behavior of a bistable system when the background temperature profile is inhomogeneous due to the
presence of a localized hot region (blowtorch) on one side of the potential barrier. Since the diffusion equation for inhomogeneous
medium is model-dependent, we consider two physical models to study the kinetics of such system. Using a conventional stochastic
method, we obtain the escape and equilibration rates of the system for the two physical models. For both models, we find that
the hot region enhances the escape rate from the well where it is placed while it retards the escape rate from the other well. However, the value of the escape rate from the well where the hot region is placed differs
for the two models while that of the escape rate from the other well is identical for both. This work, for the first time,
gives a detailed report of the similarities and differences of the escape rates and, hence, exposes the common and distinct
features of the two known physical models in determining the way the bistable system relaxes.
Received 25 September 2001 相似文献
18.
Exactly solvable models through the generalized empty interval method,for multi-species interactions
A. Aghamohammadi M. Alimohammadi M. Khorrami 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(3):371-378
Multi-species reaction-diffusion systems, with nearest-neighbor interaction on a one-dimensional lattice are considered. Necessary
and sufficient constraints on the interaction rates are obtained, that guarantee the closedness of the time evolution equation
for E
n(t)'s, the expectation value of the product of certain linear combination of the number operators on n consecutive sites at time t. The constraints are solved for the single-species left-right-symmetric systems. Also, examples of multi-species system for
which the evolution equations of E
n(t)'s are closed, are given.
Received 25 September 2002 / Received in final form 3 December 2002 Published online 14 February 2003
RID="a"
ID="a"e-mail: mamwad@iasbs.ac.ir 相似文献
19.
A.K. Chattopadhyay 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(4):567-576
We study the dynamics of a growing crystalline facet where the growth mechanism is controlled by the geometry of the local
curvature. A continuum model, in (2+1) dimensions, is developed in analogy with the Kardar-Parisi-Zhang (KPZ) model is considered
for the purpose. Following standard coarse graining procedures, it is shown that in the large time, long distance limit, the
continuum model predicts a curvature independent KPZ phase, thereby suppressing all explicit effects of curvature and local
pinning in the system, in the “perturbative” limit. A direct numerical integration of this growth equation, in 1+1 dimensions,
supports this observation below a critical parametric range, above which generic instabilities, in the form of isolated pillared
structures lead to deviations from standard scaling behaviour. Possibilities of controlling this instability by introducing
statistically “irrelevant" (in the sense of renormalisation groups) higher ordered nonlinearities have also been discussed.
Received 23 April 2002 / Received in final form 24 July 2002 Published online 31 October 2002
RID="a"
ID="a"e-mail: akc@mpipks-dresden.mpg.de 相似文献
20.
V. Da Costa Y. Henry F. Bardou M. Romeo K. Ounadjela 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(2):297-303
Tiny spatial fluctuations of tunnel barrier parameters are shown to have dramatic consequences on the statistical properties
of quantum tunneling. A direct experimental evidence is provided that the tunnel current through metal-oxide junctions, imaged
at a nanometric scale, exhibits broad statistical distributions extending over more than 4 orders of magnitude. Striking effects
of broad current distributions are shown: the total tunnel transmission is dominated by few highly transmitting sites and
the typical current density varies strongly with the size of the junction. Moreover, self-averaging of the tunnel current
fluctuations occurs only for unexpectedly large junction areas.
Received 1 April 1999 相似文献