The Experts below are selected from a list of 231 Experts worldwide ranked by ideXlab platform
Prasad Yarlagadda - One of the best experts on this subject based on the ideXlab platform.
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An advanced meshless technique for large deformation analysis of metal forming
Australian Journal of Mechanical Engineering, 2009Co-Authors: Cheng Yan, Prasad YarlagaddaAbstract:Large deformation analysis is one of the major challenges in numerical modelling and simulation of metal forming. Although the finite element method (FEM) is a well-established method for modelling non-linear problems, it often encounters difficulties for large deformation analyses due to the mesh distortion issues. Because no mesh is used, the meshless methods show very good potential for large deformation analysis. In this paper, a local meshless formulation is developed for large deformation analysis. The Radial Basis Function (RBF) is employed to construct the meshless shape functions, and the spline function with high continuity is used as the weight function in the construction of the local weak form. The discrete equations for large deformation of solids are obtained using the local weak-forms, RBF shape functions and the total Lagrangian approach, which refers all variables to the Initial (Undeformed) Configuration. This formulation requires no explicit mesh in computation and therefore fully avoids mesh distortion difficulties in the large deformation analysis of metal forming. Several example problems are presented to demonstrate the effectiveness of the developed meshless technique. It has been found that the developed meshless technique provides a superior performance to the conventional FEM in dealing with large deformation problems in metal forming.
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An advanced meshless technique for large deformation analysis of metal forming
2008Co-Authors: Prasad Yarlagadda, Cheng YanAbstract:The large deformation analysis is one of major challenges in numerical modelling and simulation of metal forming. Although the finite element method (FEM) is a well-established method for modeling nonlinear problems, it often encounters difficulties for large deformation analyses due to the mesh distortion issues. Because no mesh is used, the meshless methods show very good potential for the large deformation analysis. In this paper, a local meshless formulation is developed for the large deformation analysis. The Radial Basis Function (RBF) is employed to construct the meshless shape functions, and the spline function with high continuity is used as the weight function in the construction of the local weak form. The discrete equations for large deformation of solids are obtained using the local weak-forms, RBF shape functions, and the total Lagrangian (TL) approach, which refers all variables to the Initial (Undeformed) Configuration. This formulation requires no explicit mesh in computation and therefore fully avoids mesh distortion difficulties in the large deformation analysis of metal forming. Several example problems are presented to demonstrate the effectiveness of the developed meshless technique. It has been found that the developed meshless technique provides a superior performance to the conventional FEM in dealing with large deformation problems in metal forming.
Cheng Yan - One of the best experts on this subject based on the ideXlab platform.
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An advanced meshless technique for large deformation analysis of metal forming
Australian Journal of Mechanical Engineering, 2009Co-Authors: Cheng Yan, Prasad YarlagaddaAbstract:Large deformation analysis is one of the major challenges in numerical modelling and simulation of metal forming. Although the finite element method (FEM) is a well-established method for modelling non-linear problems, it often encounters difficulties for large deformation analyses due to the mesh distortion issues. Because no mesh is used, the meshless methods show very good potential for large deformation analysis. In this paper, a local meshless formulation is developed for large deformation analysis. The Radial Basis Function (RBF) is employed to construct the meshless shape functions, and the spline function with high continuity is used as the weight function in the construction of the local weak form. The discrete equations for large deformation of solids are obtained using the local weak-forms, RBF shape functions and the total Lagrangian approach, which refers all variables to the Initial (Undeformed) Configuration. This formulation requires no explicit mesh in computation and therefore fully avoids mesh distortion difficulties in the large deformation analysis of metal forming. Several example problems are presented to demonstrate the effectiveness of the developed meshless technique. It has been found that the developed meshless technique provides a superior performance to the conventional FEM in dealing with large deformation problems in metal forming.
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An advanced meshless technique for large deformation analysis of metal forming
2008Co-Authors: Prasad Yarlagadda, Cheng YanAbstract:The large deformation analysis is one of major challenges in numerical modelling and simulation of metal forming. Although the finite element method (FEM) is a well-established method for modeling nonlinear problems, it often encounters difficulties for large deformation analyses due to the mesh distortion issues. Because no mesh is used, the meshless methods show very good potential for the large deformation analysis. In this paper, a local meshless formulation is developed for the large deformation analysis. The Radial Basis Function (RBF) is employed to construct the meshless shape functions, and the spline function with high continuity is used as the weight function in the construction of the local weak form. The discrete equations for large deformation of solids are obtained using the local weak-forms, RBF shape functions, and the total Lagrangian (TL) approach, which refers all variables to the Initial (Undeformed) Configuration. This formulation requires no explicit mesh in computation and therefore fully avoids mesh distortion difficulties in the large deformation analysis of metal forming. Several example problems are presented to demonstrate the effectiveness of the developed meshless technique. It has been found that the developed meshless technique provides a superior performance to the conventional FEM in dealing with large deformation problems in metal forming.
Yang Mingguan - One of the best experts on this subject based on the ideXlab platform.
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Analyse de la stabilité au feu des murs en béton armé par l'approche calcul à la rupture
HAL CCSD, 2018Co-Authors: Yang MingguanAbstract:High rise reinforced concrete walls under fire exhibit important out-of-plane displacements, which in turn lead to an eccentricity of the self-weight with respect to the Initial Undeformed Configuration, resulting in supplementary bending moments. This geometrical change, combined with the degradation of the stiffness and strength properties of reinforced concrete due to severe temperature increase, may lead to the failure of walls under fire.Investigation on fire resistance of reinforced concrete walls will be based on the yield design approach in order to analyze the global stability of high rise walls, taking into account the geometry changes induced by the thermal loading.The program consists of two parts.Firstly, a 9-meter high reinforced concrete wall has already been tested under fire with the equipment Vulcan. This full size experiment aims at validating the modeling of plates under large out-of-plan displacement and identifying potential local phenomenon which has not been considered in the model.Secondly, a yield design approach will carried out to analyze the stability of reinforced concrete walls. By using the perturbation method, a recursive analytical procedure based on a kinematic approach is proposed to find the deformed Configuration of reinforced concrete walls under fire. The deformed Configuration will be later modeled as a shallow shell, on which a yield design procedure will be performed by a non-linear optimizationPour les panneaux de grande hauteur soumis à un fort gradient thermique associé à l’incendie, ils subissent des déplacements hors plan importants qui, du fait de l’excentrement du poids propre qui en résulte, vont engendrer des efforts de flexion venant s’ajouter aux efforts de compression déjà existants. Un tel changement de géométrie, d’autant plus prononcé que le panneau est de grande hauteur, combiné à une dégradation simultanée des propriétés de résistance des matériaux sous l’effet de l’élévation de température, peut conduire à un effondrement de la structure sous poids propre. L’évaluation de la résistance au feu d’éléments de structures de grandes dimensions, repose sur la théorie du calcul à la rupture, appliquée d’une part à la détermination d’un diagramme d’interaction au feu caractérisant la résistance du panneau en chacune de ses sections, d’autre part à l’analyse de la ruine globale du panneau dans sa Configuration déformée. Le programme comporte deux volets complémentaires. Le premier volet concerne l’approche expérimentale. Un mur de 9 mètre a été testé sur le grand équipement Vulcain afin de valider le modèle de calcul d’une part, qui est en cours du développement, et à identifier des phénomènes locaux éventuels non accessibles par la modélisation d’autre part. Le deuxième volet concerne le développement d’outils de modélisation et de calcul performants. Basées sur une approche cinématique, des procédures itératives qui se reposent sur la méthode de perturbation ont été construit pour chercher une solution analytique pour prédire la Configuration déformée d’une plaque soumis à un fort gradient thermique. Ensuite, des méthodes numériques fondées sur la discrétisation en éléments finis du panneau déformé, traité comme une coque à faible courbure, et l’utilisation de techniques d’optimisation non-linéaires, qui ont connu récemment des progrès importants, devront pouvoir être développées et appliquées à ce problèm
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Stability of reinforced concrete walls under fire conditions by a yield design approach
2018Co-Authors: Yang MingguanAbstract:Pour les panneaux de grande hauteur soumis à un fort gradient thermique associé à l’incendie, ils subissent des déplacements hors plan importants qui, du fait de l’excentrement du poids propre qui en résulte, vont engendrer des efforts de flexion venant s’ajouter aux efforts de compression déjà existants. Un tel changement de géométrie, d’autant plus prononcé que le panneau est de grande hauteur, combiné à une dégradation simultanée des propriétés de résistance des matériaux sous l’effet de l’élévation de température, peut conduire à un effondrement de la structure sous poids propre. L’évaluation de la résistance au feu d’éléments de structures de grandes dimensions, repose sur la théorie du calcul à la rupture, appliquée d’une part à la détermination d’un diagramme d’interaction au feu caractérisant la résistance du panneau en chacune de ses sections, d’autre part à l’analyse de la ruine globale du panneau dans sa Configuration déformée. Le programme comporte deux volets complémentaires. Le premier volet concerne l’approche expérimentale. Un mur de 9 mètre a été testé sur le grand équipement Vulcain afin de valider le modèle de calcul d’une part, qui est en cours du développement, et à identifier des phénomènes locaux éventuels non accessibles par la modélisation d’autre part. Le deuxième volet concerne le développement d’outils de modélisation et de calcul performants. Basées sur une approche cinématique, des procédures itératives qui se reposent sur la méthode de perturbation ont été construit pour chercher une solution analytique pour prédire la Configuration déformée d’une plaque soumis à un fort gradient thermique. Ensuite, des méthodes numériques fondées sur la discrétisation en éléments finis du panneau déformé, traité comme une coque à faible courbure, et l’utilisation de techniques d’optimisation non-linéaires, qui ont connu récemment des progrès importants, devront pouvoir être développées et appliquées à ce problèmeHigh rise reinforced concrete walls under fire exhibit important out-of-plane displacements, which in turn lead to an eccentricity of the self-weight with respect to the Initial Undeformed Configuration, resulting in supplementary bending moments. This geometrical change, combined with the degradation of the stiffness and strength properties of reinforced concrete due to severe temperature increase, may lead to the failure of walls under fire.Investigation on fire resistance of reinforced concrete walls will be based on the yield design approach in order to analyze the global stability of high rise walls, taking into account the geometry changes induced by the thermal loading.The program consists of two parts.Firstly, a 9-meter high reinforced concrete wall has already been tested under fire with the equipment Vulcan. This full size experiment aims at validating the modeling of plates under large out-of-plan displacement and identifying potential local phenomenon which has not been considered in the model.Secondly, a yield design approach will carried out to analyze the stability of reinforced concrete walls. By using the perturbation method, a recursive analytical procedure based on a kinematic approach is proposed to find the deformed Configuration of reinforced concrete walls under fire. The deformed Configuration will be later modeled as a shallow shell, on which a yield design procedure will be performed by a non-linear optimizatio
J. A. Rech - One of the best experts on this subject based on the ideXlab platform.
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Permanent deformation caused by subduction earthquakes in northern Chile
Nature Geoscience, 2013Co-Authors: A. Baker, R. W. Allmendinger, L. A. Owen, J. A. RechAbstract:Earth’s crust is thought to eventually rebound following an earthquake so that deformation is not permanent. Field analysis in the Atacama Desert, northern Chile, however, identifies numerous large cracks in the crust, implying that the crust here has been permanently deformed by thousands of earthquakes that have occurred over the past million years. Earthquakes are accompanied by coseismic and post-seismic rebound: blocks of crust on either side of the fault spring back to their Initial, Undeformed Configuration. This rebound is well documented by space geodetic data, such as the Global Positioning System. Thus, all earthquake-induced deformation of the crust is considered non-permanent and is modelled as an elastic or visco-elastic process. Here, however, we show that earthquakes larger than magnitude 7 in northern Chile caused the crust to deform permanently. We identify millimetre- to metre-scale tension cracks in the crust of the Atacama Desert and use cosmogenic nuclides to date the timing of crack formation. The cracks were formed by between 2,000 and 9,000 individual plate-boundary earthquakes that occurred in the past 0.8–1 million years. We show that up to 10% of the horizontal deformation generated during the earthquakes, recorded by Global Positioning System data and previously assumed to be recoverable, is permanent. Our data set provides a record of permanent strain in the shallow crust of the South American Plate. Although deformation of the deep crust may be predominantly elastic, we conclude that modelling of the earthquake cycle should also include a significant plastic component.
A. Baker - One of the best experts on this subject based on the ideXlab platform.
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Permanent deformation caused by subduction earthquakes in northern Chile
Nature Geoscience, 2013Co-Authors: A. Baker, R. W. Allmendinger, L. A. Owen, J. A. RechAbstract:Earth’s crust is thought to eventually rebound following an earthquake so that deformation is not permanent. Field analysis in the Atacama Desert, northern Chile, however, identifies numerous large cracks in the crust, implying that the crust here has been permanently deformed by thousands of earthquakes that have occurred over the past million years. Earthquakes are accompanied by coseismic and post-seismic rebound: blocks of crust on either side of the fault spring back to their Initial, Undeformed Configuration. This rebound is well documented by space geodetic data, such as the Global Positioning System. Thus, all earthquake-induced deformation of the crust is considered non-permanent and is modelled as an elastic or visco-elastic process. Here, however, we show that earthquakes larger than magnitude 7 in northern Chile caused the crust to deform permanently. We identify millimetre- to metre-scale tension cracks in the crust of the Atacama Desert and use cosmogenic nuclides to date the timing of crack formation. The cracks were formed by between 2,000 and 9,000 individual plate-boundary earthquakes that occurred in the past 0.8–1 million years. We show that up to 10% of the horizontal deformation generated during the earthquakes, recorded by Global Positioning System data and previously assumed to be recoverable, is permanent. Our data set provides a record of permanent strain in the shallow crust of the South American Plate. Although deformation of the deep crust may be predominantly elastic, we conclude that modelling of the earthquake cycle should also include a significant plastic component.