Xavier Jacob - Academia.edu (original) (raw)

Papers by Xavier Jacob

The Journal of the Acoustical Society of America, 2015

The Journal of the Acoustical Society of America, 2014

The effect of self-similarity on acoustic and elastic wave propagation at normal incidence is inv... more The effect of self-similarity on acoustic and elastic wave propagation at normal incidence is investigated using Classical Cantor and Fibonacci multilayered structures. They are made of two sorts of orthotropic plies having differently oriented orthotropic axes with respect to the propagation direction. The properties of their transmission coefficient are presented using a unidirectional numerical model based on a transfer matrix formalism. It was found that stack self-similarity influences the acoustic transmission properties. Transmission coefficients of self-similar stacks present a self-similar shape and behavior. A self-similar process, applied to layer orientation allows multilayered stacks to be created. A thickness-equivalent model was developed to compare these structures with standard self-similar multilayers which are finally compared to periodic and random stacks. The transmission coefficient of a deterministic self-similar Fibonacci structure is similar to that of an averaged transmission coefficient of random stacks.

IEEE Ultrasonics Symposium, 2005., 2005

Measurements of the static displacement, induced by the radiation stress associated with a longit... more Measurements of the static displacement, induced by the radiation stress associated with a longitudinal acoustic wave propagating in a solid are presented. High frequency acoustic tone bursts were launched into samples of fused silica and duralumin. The static displacement was measured, at the sample free surface, with a heterodyne optical interferometer. Concerning the role of the nonlinearity parameter and the

Physical Review Letters, 2008

Experiments with acoustic waves guided along the mechanically free surface of an unconsolidated g... more Experiments with acoustic waves guided along the mechanically free surface of an unconsolidated granular packed structure provide information on the elasticity of granular media at very low pressures that are naturally controlled by the gravitational acceleration and the depth beneath the surface. Comparison of the determined dispersion relations for guided surface acoustic modes with a theoretical model reveals the dependencies of the elastic moduli of the granular medium on pressure. The experiments confirm recent theoretical predictions that relaxation of the disordered granular packing through non-affine motion leads to a peculiar scaling of shear rigidity with pressure near the jamming transition corresponding to zero pressure. Unexpectedly, and in disagreement with the most of the available theories, the bulk modulus depends on pressure in a very similar way to the shear modulus.

The Journal of the Acoustical Society of America, 2008

ABSTRACT Unconsolidated granular materials exhibit strong dependence of elastic properties on pre... more ABSTRACT Unconsolidated granular materials exhibit strong dependence of elastic properties on pressure due to high sensitivity of the intergrain contacts to magnitude of loading. As a consequence the gravity field makes these granular assemblages highly elastically inhomogeneous particularly near mechanically free surface. Theoretical and experimental investigations conducted recently have demonstrated that multiple waveguide surface acoustic modes propagate along the free surface of the solid-state skeleton in the disordered air-saturated granular packings. These modes are localized near the surface. In ordered granular packing the acoustic waves can travel along the surface inside the horizontal channels, which are localized beneath the surface. The waves of different frequencies are travelling at different depths. The anisotropy of these inhomogeneous granular phononic crystals has an important influence of the existence of the waveguide modes. The experiments with acoustic waves traveling in the vicinity of a free surface provide fundamental information on the mechanical behaviour of unconsolidated granular media at very low pressures in the vicinity of the jamming transition. The perspectives of this research could be related to the analysis of the role which could be played in the considered phenomena by the acoustic waves predominantly travelling in these granular porous assemblages through the fluid-saturated pores.

The Journal of the Acoustical Society of America, 2007

Dynamic elastography holds great promise for biological tissues characterization. Resulting from ... more Dynamic elastography holds great promise for biological tissues characterization. Resulting from the radiation force induced by focused ultrasound beam, plane shear waves are generated within the medium and imaged with an ultrafast ultrasound scanner. Known as Supersonic Shear Imaging (SSI) technique, this method allows, from the measurements of shear wave velocities, to compute shear modulus (µ) maps. Beside, in order to improve tissue diagnostic, the evaluation of the nonlinear elastic moduli could be of some interest. Recently a new formulation of the nonlinear equation describing the propagation of plane shear waves in isotropic soft incompressible solids have been developed using a new expression, up to the fourth order, of the strain energy density (e): 2 2 3 2

The Journal of the Acoustical Society of America, 2002

ABSTRACT

Applied Physics Letters, 2006

Measurements of the static displacement induced by the radiation stress associated with a longitu... more Measurements of the static displacement induced by the radiation stress associated with a longitudinal acoustic wave propagating in a solid are presented. Acoustic tone bursts were launched into fused silica and duraluminum samples. The static displacement was measured at the sample free surface with an optical interferometer. The role of the nonlinearity parameter and the variations of the dc pulse

The Journal of the Acoustical Society of America, 2006

ABSTRACT

The Journal of the Acoustical Society of America, 2015

The Journal of the Acoustical Society of America, 2014

The effect of self-similarity on acoustic and elastic wave propagation at normal incidence is inv... more The effect of self-similarity on acoustic and elastic wave propagation at normal incidence is investigated using Classical Cantor and Fibonacci multilayered structures. They are made of two sorts of orthotropic plies having differently oriented orthotropic axes with respect to the propagation direction. The properties of their transmission coefficient are presented using a unidirectional numerical model based on a transfer matrix formalism. It was found that stack self-similarity influences the acoustic transmission properties. Transmission coefficients of self-similar stacks present a self-similar shape and behavior. A self-similar process, applied to layer orientation allows multilayered stacks to be created. A thickness-equivalent model was developed to compare these structures with standard self-similar multilayers which are finally compared to periodic and random stacks. The transmission coefficient of a deterministic self-similar Fibonacci structure is similar to that of an averaged transmission coefficient of random stacks.

IEEE Ultrasonics Symposium, 2005., 2005

Measurements of the static displacement, induced by the radiation stress associated with a longit... more Measurements of the static displacement, induced by the radiation stress associated with a longitudinal acoustic wave propagating in a solid are presented. High frequency acoustic tone bursts were launched into samples of fused silica and duralumin. The static displacement was measured, at the sample free surface, with a heterodyne optical interferometer. Concerning the role of the nonlinearity parameter and the

Physical Review Letters, 2008

Experiments with acoustic waves guided along the mechanically free surface of an unconsolidated g... more Experiments with acoustic waves guided along the mechanically free surface of an unconsolidated granular packed structure provide information on the elasticity of granular media at very low pressures that are naturally controlled by the gravitational acceleration and the depth beneath the surface. Comparison of the determined dispersion relations for guided surface acoustic modes with a theoretical model reveals the dependencies of the elastic moduli of the granular medium on pressure. The experiments confirm recent theoretical predictions that relaxation of the disordered granular packing through non-affine motion leads to a peculiar scaling of shear rigidity with pressure near the jamming transition corresponding to zero pressure. Unexpectedly, and in disagreement with the most of the available theories, the bulk modulus depends on pressure in a very similar way to the shear modulus.

The Journal of the Acoustical Society of America, 2008

ABSTRACT Unconsolidated granular materials exhibit strong dependence of elastic properties on pre... more ABSTRACT Unconsolidated granular materials exhibit strong dependence of elastic properties on pressure due to high sensitivity of the intergrain contacts to magnitude of loading. As a consequence the gravity field makes these granular assemblages highly elastically inhomogeneous particularly near mechanically free surface. Theoretical and experimental investigations conducted recently have demonstrated that multiple waveguide surface acoustic modes propagate along the free surface of the solid-state skeleton in the disordered air-saturated granular packings. These modes are localized near the surface. In ordered granular packing the acoustic waves can travel along the surface inside the horizontal channels, which are localized beneath the surface. The waves of different frequencies are travelling at different depths. The anisotropy of these inhomogeneous granular phononic crystals has an important influence of the existence of the waveguide modes. The experiments with acoustic waves traveling in the vicinity of a free surface provide fundamental information on the mechanical behaviour of unconsolidated granular media at very low pressures in the vicinity of the jamming transition. The perspectives of this research could be related to the analysis of the role which could be played in the considered phenomena by the acoustic waves predominantly travelling in these granular porous assemblages through the fluid-saturated pores.

The Journal of the Acoustical Society of America, 2007

Dynamic elastography holds great promise for biological tissues characterization. Resulting from ... more Dynamic elastography holds great promise for biological tissues characterization. Resulting from the radiation force induced by focused ultrasound beam, plane shear waves are generated within the medium and imaged with an ultrafast ultrasound scanner. Known as Supersonic Shear Imaging (SSI) technique, this method allows, from the measurements of shear wave velocities, to compute shear modulus (µ) maps. Beside, in order to improve tissue diagnostic, the evaluation of the nonlinear elastic moduli could be of some interest. Recently a new formulation of the nonlinear equation describing the propagation of plane shear waves in isotropic soft incompressible solids have been developed using a new expression, up to the fourth order, of the strain energy density (e): 2 2 3 2

The Journal of the Acoustical Society of America, 2002

ABSTRACT

Applied Physics Letters, 2006

Measurements of the static displacement induced by the radiation stress associated with a longitu... more Measurements of the static displacement induced by the radiation stress associated with a longitudinal acoustic wave propagating in a solid are presented. Acoustic tone bursts were launched into fused silica and duraluminum samples. The static displacement was measured at the sample free surface with an optical interferometer. The role of the nonlinearity parameter and the variations of the dc pulse

The Journal of the Acoustical Society of America, 2006

ABSTRACT