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Charlie Kong - One of the best experts on this subject based on the ideXlab platform.
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grain growth mechanism of lamellar structure high purity nickel via cold rolling and cryorolling during annealing
Materials, 2021Co-Authors: Zhibao Xie, Charlie KongAbstract:High-purity (99.999%) nickel with lamellar-structure grains (LG) was obtained by room-temperature rolling and cryorolling in this research, and then annealed at different temperatures (75 °C, 160 °C, and 245 °C). The microstructure was characterized by transmission electron microscopy. The grain growth mechanism during annealing of the LG materials obtained via different processes was studied. Results showed that the LG high-purity nickel obtained by room-temperature rolling had a static discontinuous recrystallization during annealing, whereas that obtained by cryorolling underwent static and continuous recrystallization during annealing, which was caused by the seriously inhibited dislocation recovery in the rolling process under cryogenic conditions, leading to more accumulated Deformation Energy storage in sheets.
M D Goel - One of the best experts on this subject based on the ideXlab platform.
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Deformation Energy absorption and crushing behavior of single double and multi wall foam filled square and circular tubes
Thin-walled Structures, 2015Co-Authors: M D GoelAbstract:Deformation and Energy absorption studies with single, double and multi-wall square and circular tube structure with and without aluminum foam core are carried out for assessing its effectiveness in crashworthiness under the identical test conditions. Modeling and numerical simulation of aluminum foam filled square tubes under axial impact loading is presented. The foam-filled thin-walled square tubes are modeled as shell wherein, foam core is modeled by incorporating visco-elastic plastic foam model in Altair s RADIOSS TM . It is observed that the multi-wall tube structure with foam core alters the Deformation modes considerably and results in substantial increase in Energy absorption capacity in comparison with the single and multi-wall tube without foam core. Moreover, the multi-wall tube foam filled structure shows mixed Deformation modes due to the significant effect of stress wave propagation. This study will help automotive industry to design superior crashworthy components with multi-tube foam filled structures and will reduce the experimental trials by conducting the numerical simulations. & 2015 Elsevier Ltd. All rights reserved.
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Deformation Energy absorption and crushing behavior of single double and multi wall foam filled square and circular tubes
Thin-walled Structures, 2015Co-Authors: M D GoelAbstract:Abstract Deformation and Energy absorption studies with single, double and multi-wall square and circular tube structure with and without aluminum foam core are carried out for assessing its effectiveness in crashworthiness under the identical test conditions. Modeling and numerical simulation of aluminum foam filled square tubes under axial impact loading is presented. The foam-filled thin-walled square tubes are modeled as shell wherein, foam core is modeled by incorporating visco-elastic plastic foam model in Altair® RADIOSSTM. It is observed that the multi-wall tube structure with foam core alters the Deformation modes considerably and results in substantial increase in Energy absorption capacity in comparison with the single and multi-wall tube without foam core. Moreover, the multi-wall tube foam filled structure shows mixed Deformation modes due to the significant effect of stress wave propagation. This study will help automotive industry to design superior crashworthy components with multi-tube foam filled structures and will reduce the experimental trials by conducting the numerical simulations.
G. Rosi - One of the best experts on this subject based on the ideXlab platform.
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analytical continuum mechanics a la hamilton piola least action principle for second gradient continua and capillary fluids
Mathematics and Mechanics of Solids, 2015Co-Authors: Nicolas Auffray, V. Eremeyev, A. Madeo, Francesco Dellisola, G. RosiAbstract:In this paper a stationary action principle is proved to hold for capillary fluids, i.e. fluids for which the Deformation Energy has the form suggested, starting from molecular arguments. We remark that these fluids are sometimes also called Korteweg–de Vries or Cahn–Allen fluids. In general, continua whose Deformation Energy depends on the second gradient of placement are called second gradient (or Piola–Toupin, Mindlin, Green–Rivlin, Germain or second grade) continua. In the present paper, a material description for second gradient continua is formulated. A Lagrangian action is introduced in both the material and spatial descriptions and the corresponding Euler–Lagrange equations and boundary conditions are found. These conditions are formulated in terms of an objective Deformation Energy volume density in two cases: when this Energy is assumed to depend on either C and ∇C or on C−1 and ∇C−1, where C is the Cauchy–Green Deformation tensor. When particularized to energies which characterize fluid materia...
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Least action principle for second gradient continua and capillary fluids: a Lagrangian approach following Piola's point of view
2014Co-Authors: Nicolas Auffray, F. Dell'isola, V. Eremeyev, A. Madeo, Luca Placidi, G. RosiAbstract:As Piola would have surely conjectured, the stationary action principle holds also for capillary uids, i.e. those fluids for which the Deformation Energy depends on spatial derivative of mass density (a modelling necessity which has been already remarked by Cahn and Hilliard [15, 16]). For capillary fluids it is indeed possible to de fine a Lagrangian density function whose corresponding Euler-Lagrange stationarity conditions once transported on the actual con guration, via a Piola's transformation, are exactly those obtained, with di fferent methods, in the literature. We recall that some particulat classes of second gradient fluids are sometimes also called Korteweg-de Vries or Cahn-Allen fluids. More generally those continua (which may be solid or fluid) whose Deformation Energy depends on the second gradient of placement are called second gradient (or Piola-Toupin or Mindlin or Green-Rivlin or Germain or second grade) continua. In the present work, following closely the procedure fi rst conceived by Piola and carefully presented in his works translated in the present volume, a material (Lagragian) description for second gradient continua is formulated. Subsequently a Lagrangian action is introduced and by means of Piola's transformations this action is calculated in both the material and spatial descriptions. Then the corresponding Euler-Lagrange equations and boundary conditions are calculated by using some kinematical relationships suitably established. Once an objective Deformation Energy volume density is assumed to depend on either C and ∇C or on C^(-1) and (where C is the Cauchy-Green Deformation tensor) the particular form of aforementioned Euler-Lagrange conditions and boundary conditions are established. When further particularizing the treatment to those energies which characterize fl uid materials, the capillary fluid evolution conditions (see e.g. Casal [25] or Seppecher [142, 145] for an alternative deduction based on thermodynamic arguments) are recovered. Also a version of Bernoulli's law which is valid for capillary fluids is found and, in Appendix B, all the kinematic formulas which we have found useful for the present variational formulation are gathered. Many historical comments about Gabrio Piola's contribution to analytical continuum mechanics are also presented when it has been considered useful. In this context the reader is also referred to Capecchi and Ruta [17].
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Analytical continuum mechanics à la Hamilton-Piola: least action principle for second gradient continua and capillary fluids
Mathematics and Mechanics of Solids, 2013Co-Authors: Nicolas Auffray, F. Dell'isola, V. Eremeyev, A. Madeo, G. RosiAbstract:In this paper a stationary action principle is proven to hold for capillary fluids, i.e. fluids for which the Deformation Energy has the form suggested, starting from molecular arguments, for instance by Cahn and Hilliard. Remark that these fluids are sometimes also called Korteweg-de Vries or Cahn-Allen. In general continua whose Deformation Energy depend on the second gradient of placement are called second gradient (or Piola-Toupin or Mindlin or Green-Rivlin or Germain or second gradient) continua. In the present paper, a material description for second gradient continua is formulated. A Lagrangian action is introduced in both material and spatial description and the corresponding Euler-Lagrange bulk and boundary conditions are found. These conditions are formulated in terms of an objective Deformation Energy volume density in two cases: when this Energy is assumed to depend on either C and grad C or on C^-1 and grad C^-1 ; where C is the Cauchy-Green Deformation tensor. When particularized to energies which characterize fluid materials, the capillary fluid evolution conditions (see e.g. Casal or Seppecher for an alternative deduction based on thermodynamic arguments) are recovered. A version of Bernoulli law valid for capillary fluids is found and, in the Appendix B, useful kinematic formulas for the present variational formulation are proposed. Historical comments about Gabrio Piola's contribution to continuum analytical mechanics are also presented. In this context the reader is also referred to Capecchi and Ruta.
Domen Seruga - One of the best experts on this subject based on the ideXlab platform.
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geometric modelling of elastic and elastic plastic solids by separation of Deformation Energy and prandtl operators
International Journal of Solids and Structures, 2020Co-Authors: Domen Seruga, Odysseas Kosmas, Andrey P JivkovAbstract:Abstract A geometric method for analysis of elastic and elastic-plastic solids is proposed. It involves operators on naturally discrete domains representing a material’s microstructure, rather than the classical discretisation of domains for solving continuum boundary value problems. Discrete microstructures are considered as general cell complexes, which are circumcentre-dual to simplicial cell complexes. The proposed method uses the separation of the total Deformation Energy into volumetric and distortional parts as a base for introducing elastoplastic material behaviour. Volumetric parts are obtained directly from volume changes of dual cells, and the distortional parts are calculated from the distance changes between primal and dual nodes. First, it is demonstrated that the method can accurately reproduce the elastic behaviour of solids with Poisson’s ratios in the thermodynamically admissible range from -0.99 to 0.49. Further verification of the method is demonstrated by excellent agreement between analytical results and simulations of the elastic Deformation of a beam subjected to a vertical displacement. Second, the Prandtl operator approach is used to simulate the behaviour of the solid during cyclic loading, considering its elastoplastic material properties. Results from simulations of cyclic behaviour during alternating and variable load histories are compared to expected macroscopic behaviour as further support to the applicability of the method to elastic-plastic problems.
Zhibao Xie - One of the best experts on this subject based on the ideXlab platform.
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grain growth mechanism of lamellar structure high purity nickel via cold rolling and cryorolling during annealing
Materials, 2021Co-Authors: Zhibao Xie, Charlie KongAbstract:High-purity (99.999%) nickel with lamellar-structure grains (LG) was obtained by room-temperature rolling and cryorolling in this research, and then annealed at different temperatures (75 °C, 160 °C, and 245 °C). The microstructure was characterized by transmission electron microscopy. The grain growth mechanism during annealing of the LG materials obtained via different processes was studied. Results showed that the LG high-purity nickel obtained by room-temperature rolling had a static discontinuous recrystallization during annealing, whereas that obtained by cryorolling underwent static and continuous recrystallization during annealing, which was caused by the seriously inhibited dislocation recovery in the rolling process under cryogenic conditions, leading to more accumulated Deformation Energy storage in sheets.