Giulio Sciarra - Academia.edu (original) (raw)
Papers by Giulio Sciarra
Proceedings of The Royal Society A: Mathematical, Physical and Engineering Sciences, Apr 22, 2009
In the spirit of Germain the most general objective stored elastic energy for a second gradient m... more In the spirit of Germain the most general objective stored elastic energy for a second gradient material is deduced using a literature result of Fortuné & Vallée. Linear isotropic constitutive relations for stress and hyperstress in terms of strain and straingradient are then obtained proving that these materials are characterized by seven elastic moduli and generalizing previous studies by Toupin, Mindlin and Sokolowski. Using a suitable decomposition of the strain-gradient, it is found a necessary and sufficient condition, to be verified by the elastic moduli, assuring positive definiteness of the stored elastic energy. The problem of warping in linear torsion of a prismatic second gradient cylinder is formulated, thus obtaining a possible measurement procedure for one of the second gradient elastic moduli.
International Journal of Non-linear Mechanics, May 1, 2016
We study volume transition phenomenon in hydrogels within the framework of Flory-Rehner thermodyn... more We study volume transition phenomenon in hydrogels within the framework of Flory-Rehner thermodynamic modelling; we show that starting from different models for the Flory parameter different conclusions can be achieved, in terms of admissible coexisting equilibria of the system. In particular, with explicit reference to a one-dimensional problem we establish the ranges of both temperature and traction which allow for the coexistence of a swollen and a shrunk phase. Through consideration of an augmented Flory-Rehner free-energy, which also accounts for the gradient of volume changes, we determine the position of the interface between the coexisting phases, and capture the connection profile between them.
1-Raw results of porosimetry on S1, S2 and S3 samples. 2-Raw X-ray scans of S1, S2, S3 samples.
Proceedings of The Royal Society A: Mathematical, Physical and Engineering Sciences, Apr 1, 2016
We study the solutions of a generalized Allen-Cahn equation deduced from a Landau energy function... more We study the solutions of a generalized Allen-Cahn equation deduced from a Landau energy functional, endowed with a non-constant higher order stiffness. We analytically solve the stationary problem and deduce the existence of so-called compactons, namely, connections on a finite interval between the two phases. The dynamics problem is numerically solved and compacton formation is described.
Canadian Geotechnical Journal, Mar 1, 2017
The paper presents a comprehensive analysis of the hydro-mechanical response of an embankment sub... more The paper presents a comprehensive analysis of the hydro-mechanical response of an embankment subject to inundation. The Modified Cam-Clay model extended to unsaturated conditions and formulated in terms of Bishop's effective stress is used to predict the mechanical behavior of the sand-clay mixture. The model's ability to accurately reproduce the embankment response is evaluated by comparing the numerical predictions with the results of the physical model. Time evolution and spatial distribution of the wetting-induced displacements are analyzed together with the stress paths resulting from the imbibition process. The influence of after-compaction conditions on the embankment performance is examined focusing on the occurrence of the volumetric collapse.
arXiv (Cornell University), Mar 1, 2020
We study the solutions of a generalized Allen-Cahn equation deduced from a Landau energy function... more We study the solutions of a generalized Allen-Cahn equation deduced from a Landau energy functional, endowed with a non-constant higher order stiffness. We assume the stiffness to be a positive function of the field and we discuss the stability of the stationary solutions proving both linear and local non-linear stability.
Taylor & Francis eBooks, Apr 26, 2005
Afluid filled cylindrical cavern of circular cross section in a homogeneous infinite salt formati... more Afluid filled cylindrical cavern of circular cross section in a homogeneous infinite salt formation under a hydrostatic stress is set under internal pressure that differs from the confining pressure. The fluid in the cavern and in the mixture is treated as ideal and the solid as elastic. The initial state of stress is a consequence of the outside pressure and the cavern pressure. Perturbing the cavern pressure induces small changes in the solid and fluid densities.We compute these fields as functions of the radial distance from the cavern centre and show that depending on the relative stress levels the (salt) formation experiences either a dilatation or a compaction that is concentrated in a boundary layer near the cavern wall. © 2005 Taylor & Francis Group, London
Wave Motion, Nov 1, 2020
We study the solutions of a generalized Allen-Cahn equation deduced from a Landau energy function... more We study the solutions of a generalized Allen-Cahn equation deduced from a Landau energy functional, endowed with a non-constant higher order stiffness. We assume the stiffness to be a positive function of the field and we discuss the stability of the stationary solutions proving both linear and local non-linear stability.
Mathematics in engineering, 2019
Traveling waves of permanent form with compact support are possible in several nonlinear partial ... more Traveling waves of permanent form with compact support are possible in several nonlinear partial nonlinear differential equations and this, mainly, along two pathways: A pure nonlinearity stronger than quadratic in the higher order gradient terms describing the mathematical model of the phenomena or a special inhomogeneity in quadratic gradient terms of the model. In the present note we perform a rigorous analysis of the mathematical structure of compactification via a generalization of a classical theorem by Weierstrass. Our mathematical analysis allows to explain in a rigorous and complete way the presence of compact structures in nonlinear partial differential equations 1 + 1 dimensions.
Frontiers in Mechanical Engineering
Within the context of immiscible biphasic flow in porous media, when the nonwetting fluid invades... more Within the context of immiscible biphasic flow in porous media, when the nonwetting fluid invades the pore spaces which are a priori saturated with the wetting fluid, capillary forces dominate if the pore network is formed by fine-grained soils. Owing to the cohesion-less frictional behavior of such soils, a capillary force–driven fracturing phenomenon has been put forward by some researchers. Unlike the purely mechanistic tensile force–driven mode-I fracturing that typically has been attributed to the formation of desiccation cracks in soils, attempts to model this alternate capillarity-driven mechanism have not yet been realized at a continuum scale. However, the macro-scale counterpart of the capillary energy associated with the various pore-scale menisci is well-established as the interfacial energy characterized by the soil-water retention curve. An investigation of the possible contribution of this interfacial energy in supplying the dissipation related to fracture initiation ...
Frontiers in Mechanical Engineering
This publication is part of the proceedings of the Biot-Bažant Conference on Engineering Mechanic... more This publication is part of the proceedings of the Biot-Bažant Conference on Engineering Mechanics and Physics of Porous Materials, which took place virtually on June 1-3, 2021. It contains a one-page abstract and the video of the talk that was given at the conference.
perturbation of fluid density and solid elastic strain in
Advances in Materials Science and Engineering, 2021
The mixing order of silica sand, clay (kaolinite), and water controls the microstructure of resul... more The mixing order of silica sand, clay (kaolinite), and water controls the microstructure of resulting artificial soil samples. Most homogeneous microstructures can be achieved by applying the mixing order “sand-water-clay.” The following methods were used to validate this statement: (1) optical observation, (2) X-ray tomography, (3) scanning electron microscopy, and (4) Mercury intrusion porosimetry. For all samples, clays are mainly organized in a homogeneous matrix but are also dispersed heterogeneously in micrometer-sized layers surrounding sand particles, particularly where sand grains show a greater roughness. At water contents ≥1.5 w L , the microstructures are visually similar from the mm to μm scale whatever mixing order is used. However, for water contents lower than 1.5 w L , the mixing order controls the distribution of the clay particles. This paper proposes a motivated choice of a preparation protocol of artificial clayey materials to be used in laboratory experiments. ...
Poromechanics III - Biot Centennial (1905-2005), 2005
Afluid filled cylindrical cavern of circular cross section in a homogeneous infinite salt formati... more Afluid filled cylindrical cavern of circular cross section in a homogeneous infinite salt formation under a hydrostatic stress is set under internal pressure that differs from the confining pressure. The fluid in the cavern and in the mixture is treated as ideal and the solid as elastic. The initial state of stress is a consequence of the outside pressure and the cavern pressure. Perturbing the cavern pressure induces small changes in the solid and fluid densities.We compute these fields as functions of the radial distance from the cavern centre and show that depending on the relative stress levels the (salt) formation experiences either a dilatation or a compaction that is concentrated in a boundary layer near the cavern wall. © 2005 Taylor & Francis Group, London
arXiv: Pattern Formation and Solitons, 2020
We study the solutions of a generalized Allen-Cahn equation deduced from a Landau energy function... more We study the solutions of a generalized Allen-Cahn equation deduced from a Landau energy functional, endowed with a non-constant higher order stiffness. We assume the stiffness to be a positive function of the field and we discuss the stability of the stationary solutions proving both linear and local non-linear stability.
Questo studio è finalizzato alla valutazione dei percorsi tensio-deformativi associati a processi... more Questo studio è finalizzato alla valutazione dei percorsi tensio-deformativi associati a processi di infiltrazione in terreni parzialmente saturi. I risultati presentati si riferiscono a un problema al finito estremamente semplice in cui le deformazioni laterali sono impedite (condizioni edometriche) e il flusso dell'acqua è monodimensionale. Gli effetti indotti dall'infiltrazione di acqua piovana dall'alto verso il basso sono analizzati con riferimento a due materiali con caratteristiche fisiche, meccaniche e idrauliche diverse, al fine di valutare come si modifica la risposta finale del deposito al variare delle proprietà del materiale
Geotechnics, 2021
Natural soils are usually heterogeneous and characterized with complex microstructures. Sand–clay... more Natural soils are usually heterogeneous and characterized with complex microstructures. Sand–clay mixtures are often used as simplified soils to investigate the mechanical properties of soils with various compositions (from clayey to sandy soils) in the laboratory. Performing laboratory tests on a sand–clay mixture with definite clay fraction can provide information to understand the simplified soils’ mechanical behavior and better predict natural soils’ behavior at the engineering scale. This paper reviews previous investigations on sand–clay mixture and soil–structure interface direct shear test. It finds that even though there are many investigations on sand–clay mixtures and soil–structure interfaces that consider pure sand or pure clay, limited data on the mechanical behavior of the interface between sand–clay mixture and structure materials are available. Knowledge is missing on how the clay content influences the mechanical behavior of interface and how the soil particles’ ar...
Proceedings of The Royal Society A: Mathematical, Physical and Engineering Sciences, Apr 22, 2009
In the spirit of Germain the most general objective stored elastic energy for a second gradient m... more In the spirit of Germain the most general objective stored elastic energy for a second gradient material is deduced using a literature result of Fortuné & Vallée. Linear isotropic constitutive relations for stress and hyperstress in terms of strain and straingradient are then obtained proving that these materials are characterized by seven elastic moduli and generalizing previous studies by Toupin, Mindlin and Sokolowski. Using a suitable decomposition of the strain-gradient, it is found a necessary and sufficient condition, to be verified by the elastic moduli, assuring positive definiteness of the stored elastic energy. The problem of warping in linear torsion of a prismatic second gradient cylinder is formulated, thus obtaining a possible measurement procedure for one of the second gradient elastic moduli.
International Journal of Non-linear Mechanics, May 1, 2016
We study volume transition phenomenon in hydrogels within the framework of Flory-Rehner thermodyn... more We study volume transition phenomenon in hydrogels within the framework of Flory-Rehner thermodynamic modelling; we show that starting from different models for the Flory parameter different conclusions can be achieved, in terms of admissible coexisting equilibria of the system. In particular, with explicit reference to a one-dimensional problem we establish the ranges of both temperature and traction which allow for the coexistence of a swollen and a shrunk phase. Through consideration of an augmented Flory-Rehner free-energy, which also accounts for the gradient of volume changes, we determine the position of the interface between the coexisting phases, and capture the connection profile between them.
1-Raw results of porosimetry on S1, S2 and S3 samples. 2-Raw X-ray scans of S1, S2, S3 samples.
Proceedings of The Royal Society A: Mathematical, Physical and Engineering Sciences, Apr 1, 2016
We study the solutions of a generalized Allen-Cahn equation deduced from a Landau energy function... more We study the solutions of a generalized Allen-Cahn equation deduced from a Landau energy functional, endowed with a non-constant higher order stiffness. We analytically solve the stationary problem and deduce the existence of so-called compactons, namely, connections on a finite interval between the two phases. The dynamics problem is numerically solved and compacton formation is described.
Canadian Geotechnical Journal, Mar 1, 2017
The paper presents a comprehensive analysis of the hydro-mechanical response of an embankment sub... more The paper presents a comprehensive analysis of the hydro-mechanical response of an embankment subject to inundation. The Modified Cam-Clay model extended to unsaturated conditions and formulated in terms of Bishop's effective stress is used to predict the mechanical behavior of the sand-clay mixture. The model's ability to accurately reproduce the embankment response is evaluated by comparing the numerical predictions with the results of the physical model. Time evolution and spatial distribution of the wetting-induced displacements are analyzed together with the stress paths resulting from the imbibition process. The influence of after-compaction conditions on the embankment performance is examined focusing on the occurrence of the volumetric collapse.
arXiv (Cornell University), Mar 1, 2020
We study the solutions of a generalized Allen-Cahn equation deduced from a Landau energy function... more We study the solutions of a generalized Allen-Cahn equation deduced from a Landau energy functional, endowed with a non-constant higher order stiffness. We assume the stiffness to be a positive function of the field and we discuss the stability of the stationary solutions proving both linear and local non-linear stability.
Taylor & Francis eBooks, Apr 26, 2005
Afluid filled cylindrical cavern of circular cross section in a homogeneous infinite salt formati... more Afluid filled cylindrical cavern of circular cross section in a homogeneous infinite salt formation under a hydrostatic stress is set under internal pressure that differs from the confining pressure. The fluid in the cavern and in the mixture is treated as ideal and the solid as elastic. The initial state of stress is a consequence of the outside pressure and the cavern pressure. Perturbing the cavern pressure induces small changes in the solid and fluid densities.We compute these fields as functions of the radial distance from the cavern centre and show that depending on the relative stress levels the (salt) formation experiences either a dilatation or a compaction that is concentrated in a boundary layer near the cavern wall. © 2005 Taylor & Francis Group, London
Wave Motion, Nov 1, 2020
We study the solutions of a generalized Allen-Cahn equation deduced from a Landau energy function... more We study the solutions of a generalized Allen-Cahn equation deduced from a Landau energy functional, endowed with a non-constant higher order stiffness. We assume the stiffness to be a positive function of the field and we discuss the stability of the stationary solutions proving both linear and local non-linear stability.
Mathematics in engineering, 2019
Traveling waves of permanent form with compact support are possible in several nonlinear partial ... more Traveling waves of permanent form with compact support are possible in several nonlinear partial nonlinear differential equations and this, mainly, along two pathways: A pure nonlinearity stronger than quadratic in the higher order gradient terms describing the mathematical model of the phenomena or a special inhomogeneity in quadratic gradient terms of the model. In the present note we perform a rigorous analysis of the mathematical structure of compactification via a generalization of a classical theorem by Weierstrass. Our mathematical analysis allows to explain in a rigorous and complete way the presence of compact structures in nonlinear partial differential equations 1 + 1 dimensions.
Frontiers in Mechanical Engineering
Within the context of immiscible biphasic flow in porous media, when the nonwetting fluid invades... more Within the context of immiscible biphasic flow in porous media, when the nonwetting fluid invades the pore spaces which are a priori saturated with the wetting fluid, capillary forces dominate if the pore network is formed by fine-grained soils. Owing to the cohesion-less frictional behavior of such soils, a capillary force–driven fracturing phenomenon has been put forward by some researchers. Unlike the purely mechanistic tensile force–driven mode-I fracturing that typically has been attributed to the formation of desiccation cracks in soils, attempts to model this alternate capillarity-driven mechanism have not yet been realized at a continuum scale. However, the macro-scale counterpart of the capillary energy associated with the various pore-scale menisci is well-established as the interfacial energy characterized by the soil-water retention curve. An investigation of the possible contribution of this interfacial energy in supplying the dissipation related to fracture initiation ...
Frontiers in Mechanical Engineering
This publication is part of the proceedings of the Biot-Bažant Conference on Engineering Mechanic... more This publication is part of the proceedings of the Biot-Bažant Conference on Engineering Mechanics and Physics of Porous Materials, which took place virtually on June 1-3, 2021. It contains a one-page abstract and the video of the talk that was given at the conference.
perturbation of fluid density and solid elastic strain in
Advances in Materials Science and Engineering, 2021
The mixing order of silica sand, clay (kaolinite), and water controls the microstructure of resul... more The mixing order of silica sand, clay (kaolinite), and water controls the microstructure of resulting artificial soil samples. Most homogeneous microstructures can be achieved by applying the mixing order “sand-water-clay.” The following methods were used to validate this statement: (1) optical observation, (2) X-ray tomography, (3) scanning electron microscopy, and (4) Mercury intrusion porosimetry. For all samples, clays are mainly organized in a homogeneous matrix but are also dispersed heterogeneously in micrometer-sized layers surrounding sand particles, particularly where sand grains show a greater roughness. At water contents ≥1.5 w L , the microstructures are visually similar from the mm to μm scale whatever mixing order is used. However, for water contents lower than 1.5 w L , the mixing order controls the distribution of the clay particles. This paper proposes a motivated choice of a preparation protocol of artificial clayey materials to be used in laboratory experiments. ...
Poromechanics III - Biot Centennial (1905-2005), 2005
Afluid filled cylindrical cavern of circular cross section in a homogeneous infinite salt formati... more Afluid filled cylindrical cavern of circular cross section in a homogeneous infinite salt formation under a hydrostatic stress is set under internal pressure that differs from the confining pressure. The fluid in the cavern and in the mixture is treated as ideal and the solid as elastic. The initial state of stress is a consequence of the outside pressure and the cavern pressure. Perturbing the cavern pressure induces small changes in the solid and fluid densities.We compute these fields as functions of the radial distance from the cavern centre and show that depending on the relative stress levels the (salt) formation experiences either a dilatation or a compaction that is concentrated in a boundary layer near the cavern wall. © 2005 Taylor & Francis Group, London
arXiv: Pattern Formation and Solitons, 2020
We study the solutions of a generalized Allen-Cahn equation deduced from a Landau energy function... more We study the solutions of a generalized Allen-Cahn equation deduced from a Landau energy functional, endowed with a non-constant higher order stiffness. We assume the stiffness to be a positive function of the field and we discuss the stability of the stationary solutions proving both linear and local non-linear stability.
Questo studio è finalizzato alla valutazione dei percorsi tensio-deformativi associati a processi... more Questo studio è finalizzato alla valutazione dei percorsi tensio-deformativi associati a processi di infiltrazione in terreni parzialmente saturi. I risultati presentati si riferiscono a un problema al finito estremamente semplice in cui le deformazioni laterali sono impedite (condizioni edometriche) e il flusso dell'acqua è monodimensionale. Gli effetti indotti dall'infiltrazione di acqua piovana dall'alto verso il basso sono analizzati con riferimento a due materiali con caratteristiche fisiche, meccaniche e idrauliche diverse, al fine di valutare come si modifica la risposta finale del deposito al variare delle proprietà del materiale
Geotechnics, 2021
Natural soils are usually heterogeneous and characterized with complex microstructures. Sand–clay... more Natural soils are usually heterogeneous and characterized with complex microstructures. Sand–clay mixtures are often used as simplified soils to investigate the mechanical properties of soils with various compositions (from clayey to sandy soils) in the laboratory. Performing laboratory tests on a sand–clay mixture with definite clay fraction can provide information to understand the simplified soils’ mechanical behavior and better predict natural soils’ behavior at the engineering scale. This paper reviews previous investigations on sand–clay mixture and soil–structure interface direct shear test. It finds that even though there are many investigations on sand–clay mixtures and soil–structure interfaces that consider pure sand or pure clay, limited data on the mechanical behavior of the interface between sand–clay mixture and structure materials are available. Knowledge is missing on how the clay content influences the mechanical behavior of interface and how the soil particles’ ar...