arXiv subjects

Elisabeth Bouchaud

Publications and source records attributed to Elisabeth Bouchaud.

14 recordsLinked to original sources

arXiv2018

Flow and fracture near the sol-gel transition of silica nanoparticle suspensions

We analyze the evolution of the mechanical response of a colloidal suspension to an external tensile stress, from fracture to flow, as a function of the distance from the sol-gel transition. We cease to observe cracks at a finite distance from the transition. In an intermediate region where the phenomenon is clearly hysteretic, we observe the coexistence of both flow and fracture. Even when cracks are observed, the material in fact flows over a distance that increases in the vicinity of the transition.

cond-mat.soft↗

arXiv2017

Roughness of oxide glass subcritical fracture surfaces

An original setup combining a very stable loading stage, an atomic force microscope and an environmental chamber, allows to obtain very stable sub-critical fracture propagation in oxide glasses under controlled environment, and subsequently to finely characterize the nanometric roughness properties of the crack surfaces. The analysis of the surface roughness is conducted both in terms of the classical root mean square roughness to compare with the literature, and in terms of more physically adequate indicators related to the self-affine nature of the fracture surfaces. Due to the comparable nanometric scale of the surface roughness, the AFM tip size and the instrumental noise, a special care is devoted to the statistical evaluation of the metrologic properties. The 2 roughness amplitude of several oxide glasses was shown to decrease as a function of the stress intensity factor, to be quite insensitive to the relative humidity and to increase with the degree of heterogeneity of the glass. The results are discussed in terms of several modeling arguments concerning the coupling between crack propagation, material's heterogeneity, crack tip plastic deformation and water diffusion at the crack tip. A synthetic new model is presented combining the predictions of a model by Wiederhorn et al. [1] on the effect of the material's heterogeneity on the crack tip stresses with the self-affine nature of the fracture surfaces.

cond-mat.soft↗

arXiv2015

Mode I fracture of a biopolymer gel: rate-dependent dissipation and large deformations disentangled

We have designed a new experimental setup able to investigate fracture of soft materials at small scales. At high crack velocity, where energy is mostly dissipated through viscoelastic processes, we observe an increasingly large high strain domain in the crack tip vicinity. Taking advantage of our ability to determine where linear elasticity breaks down, we derive a simple prediction for the evolution of the energy release rate with the crack velocity.

cond-mat.soft↗

arXiv2013

Bulk elastic fingering instability in Hele-Shaw cells

We demonstrate experimentally the existence of a purely elastic fingering instability which arises when air penetrates into an elastomer confined in a Hele-Shaw cell. Fingers appear sequentially and propagate within the bulk of the material as soon as a critical strain, independent of the elastic modulus, is exceeded. Their width depends non-linearly on the distance between the confining glass plates. A key element in the driving force of the instability is the adhesion of layers of gels to the plates, which results in a considerable expense of elastic energy during the growth of the air bubble.

cond-mat.soft↗

arXiv2013

Digital instability of a confined elastic meniscus

Thin soft elastic layers serving as joints between relatively rigid bodies may function as sealants, thermal, electrical, or mechanical insulators, bearings, or adhesives. When such a joint is stressed, even though perfect adhesion is maintained, the exposed free meniscus in the thin elastic layer becomes unstable, leading to the formation of spatially periodic digits of air that invade the elastic layer, reminiscent of viscous fingering in a thin fluid layer. How- ever, the elastic instability is reversible and rate-independent, dis- appearing when the joint is unstressed. We use theory, experiments, and numerical simulations to show that the transition to the digital state is sudden (first-order), the wavelength and amplitude of the fingers are proportional to the thickness of the elastic layer, and the required separation to trigger the instability is inversely proportional to the in-plane dimension of the layer. Our study reveals the energetic origin of this instability and has implications for the strength of polymeric adhesives; it also suggests a method for patterning thin films reversibly with any arrangement of localized fingers in a digital elastic memory, which we confirm experimentally.

cond-mat.soft↗

arXiv2013

Correlating toughness and roughness in ductile fracture

Three dimensional calculations of ductile crack growth under mode I plane strain, small scale yielding conditions are carried out using an elastic-viscoplastic constitutive relation for a progres- sively cavitating plastic solid with two populations of void nucleating second phase particles. Full field solutions are obtained for three dimensional material microstructures characterized by ran- dom distributions of void nucleating particles. Crack growth resistance curves and fracture surface roughness statistics are calculated using standard procedures. The range of void nucleating particle volume fractions considered give rise to values of toughness, JIC, that vary by a factor of four. For all volume fractions considered, the computed fracture surfaces are self-affine over a size range of about two orders of magnitude with a roughness exponent of 0.54 $\pm$ 0.03. For small void nucleating particle volume fractions, the mean large particle spacing serves as a single dominant length scale. In this regime, the correlation length of the fracture surface corresponding to the cut-off of the self-affine behavior is found to be linearly related to JIC thus quantitatively correlating toughness and fracture surface roughness.

cond-mat.soft↗

arXiv2012

Fractoluminescence characterization of the energy dissipated during fast fracture of glass

Fractoluminescence experiments are performed on two kinds of silicate glasses. All the light spectra collected during dynamic fracture reveal a black body radiator behaviour, which is interpreted as a crack velocity-dependent temperature rise close to the crack tip. Crack velocities are estimated to be of the order of 1300 m.s$^{-1}$ and fracture process zones are shown to extend over a few nanometers.

cond-mat.mtrl-sci↗

arXiv2009

French Roadmap for complex Systems 2008-2009

This second issue of the French Complex Systems Roadmap is the outcome of the Entretiens de Cargese 2008, an interdisciplinary brainstorming session organized over one week in 2008, jointly by RNSC, ISC-PIF and IXXI. It capitalizes on the first roadmap and gathers contributions of more than 70 scientists from major French institutions. The aim of this roadmap is to foster the coordination of the complex systems community on focused topics and questions, as well as to present contributions and challenges in the complex systems sciences and complexity science to the public, political and industrial spheres.

nlin.AO↗

arXiv2009

Plasticity-induced structural anisotropy of silica glass

Amorphous silica density at ambient pressure is known to depend on thermal history (through the quenching rate) but also, at room temperature, on the maximum pressure applied in the past. Here we show that beyond density, a mechanical loading can endow the structure with an orientational order. Molecular dynamics simulations show evidence that amorphous silica develops a permanent anisotropic structure after extended shear plastic flow. This anisotropy which survives for an unstressed specimen is revealed markedly by the fabric tensor computed over the Si-O-Si orientations, albeit the SiO4 tetrahedra microstructure remains mostly unaltered.

cond-mat.other↗

arXiv2006

Nanoscale damage during fracture in silica glass

We report here atomic force microscopy experiments designed to uncover the nature of failure mechanisms occuring within the process zone at the tip of a crack propagating into a silica glass specimen under stress corrosion. The crack propagates through the growth and coalescence of nanoscale damage spots. This cavitation process is shown to be the key mechanism responsible for damage spreading within the process zone. The possible origin of the nucleation of cavities, as well as the implications on the selection of both the cavity size at coalescence and the process zone extension are finally discussed.

cond-mat.stat-mech↗

arXiv2006

Scaling exponents for fracture surfaces in homogenous glass and glassy ceramics

We investigate the scaling properties of post-mortem fracture surfaces in silica glass and glassy ceramics. In both cases, the 2D height-height correlation function is found to obey Family-Viseck scaling properties, but with two sets of critical exponents, in particular a roughness exponent $ζ\simeq 0.75$ in homogeneous glass and $ζ\simeq 0.4$ in glassy ceramics. The ranges of length-scales over which these two scalings are observed are shown to be below and above the size of process zone respectively. A model derived from Linear Elastic Fracture Mechanics (LEFM) in the quasistatic approximation succeeds to reproduce the scaling exponents observed in glassy ceramics. The critical exponents observed in homogeneous glass are conjectured to reflect damage screening occurring for length-scales below the size of the process zone.

cond-mat.stat-mech↗

arXiv2006

Anisotropic self-affine properties of experimental fracture surfaces

The scaling properties of post-mortem fracture surfaces of brittle (silica glass), ductile (aluminum alloy) and quasi-brittle (mortar and wood) materials have been investigated. These surfaces, studied far from the initiation, were shown to be self-affine. However, the Hurst exponent measured along the crack direction is found to be different from the one measured along the propagation direction. More generally, a complete description of the scaling properties of these surfaces call for the use of the 2D height-height correlation function that involves three exponents zeta = 0.75, beta = 0.6 and z = 1.25 independent of the material considered as well as of the crack growth velocity. These exponents are shown to correspond to the roughness, growth and dynamic exponents respectively, as introduced in interface growth models. They are conjectured to be universal.

cond-mat.stat-mech↗

arXiv2006

Two-dimensional scaling properties of experimental fracture surfaces

The morphology of fracture surfaces encodes the various complex damage and fracture processes occurring at the microstructure scale that have lead to the failure of a given heterogeneous material. Understanding how to decipher this morphology is therefore of fundamental interest. This has been extensively investigated over these two last decades. It has been established that 1D profiles of these fracture surfaces exhibit properties of scaling invariance. In this paper, we present deeper analysis and investigate the 2D scaling properties of these fracture surfaces. We showed that the properties of scaling invariance are anisotropic and evidenced the existence of two peculiar directions on the post-mortem fracture surface caracterized by two different scaling exponents: the direction of the crack growth and the direction of the crack front. These two exponents were found to be universal, independent of the crack growth velocity, in both silica glass and aluminum alloy, archetype of brittle and ductile material respectively. Moreover, the 2D structure function that fully characterizes the scaling properties of the fracture surface was shown to take a peculiar form similar to the one predicted by some models issued from out-of-equilibrium statistical physics. This suggest some promising analogies between dynamic phase transition models and the stability of a crack front pinned/unpinned by the heterogenities of the material.

cond-mat.stat-mech↗

arXiv2005

Numerical study of the temperature and porosity effects on the fracture propagation in a 2D network of elastic bonds

This article reports results concerning the fracture of a 2d triangular lattice of atoms linked by springs. The lattice is submitted to controlled strain tests and the influence of both porosity and temperature on failure is investigated. The porosity is found on one hand to decrease the stiffness of the material but on the other hand it increases the deformation sustained prior to failure. Temperature is shown to control the ductility due to the presence of cavities that grow and merge. The rough surfaces resulting from the propagation of the crack exhibit self-affine properties with a roughness exponent $ζ= 0.59 \pm 0.07$ over a range of length scales which increases with temperature. Large cavities also have rough walls which are found to be fractal with a dimension, $D$, which evolves with the distance from the crack tip. For large distances, $D$ is found to be close to 1.5, and close to 1.0 for cavities just before their coalescence with the main crack.

physics.class-ph↗