Departament de Resistència dels Materials i Estructures en Enginyeria (fins octubre 2015)
http://hdl.handle.net/2117/4001
2017-03-24T04:46:21ZMechanical stress in abdominal aortic aneurysms using artificial neural networks
http://hdl.handle.net/2117/85112
Mechanical stress in abdominal aortic aneurysms using artificial neural networks
Soudah Prieto, Eduardo; Rodriguez, Jose; López González, Roberto
Combination of numerical modeling and artificial intelligence (AI) in bioengineering processes are a promising pathway for the further development of bioengineering sciences. The objective of this work is to use Artificial Neural Networks (ANN) to reduce the long computational times needed in the analysis of shear stress in the Abdominal Aortic Aneurysm (AAA) by finite element methods (FEM). For that purpose two different neural networks are created. The first neural network (Mesh Neural Network, MNN) creates the aneurysm geometry in terms of four geometrical factors (asymmetry factor, aneurism diameter, aneurism thickness, aneurism length). The second neural network (Tension Neural Network, TNN) combines the results of the first neural network with the arterial pressure (new factor) to obtain the maximum stress distribution (output variable) in the aneurysm wall. The use of FEM for the analysis and design of bioengineering processes often requires high computational costs, but if this technique is combined with artificial intelligence, such as neural networks, the simulation time is significantly reduced. The shear stress obtained by the artificial neural models developed in this work achieved 95% of accuracy respect to the wall stress obtained by the FEM. On the other hand, the computational time is significantly reduced compared to the FEM.
2016-04-04T11:13:54ZSoudah Prieto, EduardoRodriguez, JoseLópez González, RobertoCombination of numerical modeling and artificial intelligence (AI) in bioengineering processes are a promising pathway for the further development of bioengineering sciences. The objective of this work is to use Artificial Neural Networks (ANN) to reduce the long computational times needed in the analysis of shear stress in the Abdominal Aortic Aneurysm (AAA) by finite element methods (FEM). For that purpose two different neural networks are created. The first neural network (Mesh Neural Network, MNN) creates the aneurysm geometry in terms of four geometrical factors (asymmetry factor, aneurism diameter, aneurism thickness, aneurism length). The second neural network (Tension Neural Network, TNN) combines the results of the first neural network with the arterial pressure (new factor) to obtain the maximum stress distribution (output variable) in the aneurysm wall. The use of FEM for the analysis and design of bioengineering processes often requires high computational costs, but if this technique is combined with artificial intelligence, such as neural networks, the simulation time is significantly reduced. The shear stress obtained by the artificial neural models developed in this work achieved 95% of accuracy respect to the wall stress obtained by the FEM. On the other hand, the computational time is significantly reduced compared to the FEM.A FEM fluid-structure interaction algorithm for analysis of the seal dynamics of a Surface-Effect Ship
http://hdl.handle.net/2117/84942
A FEM fluid-structure interaction algorithm for analysis of the seal dynamics of a Surface-Effect Ship
García Espinosa, Julio; Capua, Daniel di; Serván Camas, Borja; Ubach Fuentes, Pere-Andreu; Oñate Ibáñez de Navarra, Eugenio
This paper shows the recent work of the authors in the development of a time-domain FEM model for evaluation of the seal dynamics of a surface effect ship. The fluid solver developed for this purpose, uses a potential flow approach along with a streamline integration of the free surface. The paper focuses on the free surface-structure algorithm that has been developed to allow the simulation of the complex and highly dynamic behaviour of the seals in the interface between the air cushion, and the water.; The developed fluid-structure interaction solver is based, on one side, on an implicit iteration algorithm, communicating pressure forces and displacements of the seals at memory level and, on the other side, on an innovative wetting and drying scheme able to predict the water action on the seals. The stability of the iterative scheme is improved by means of relaxation, and the convergence is accelerated using Aitken's method.; Several validations against experimental results have been carried out to demonstrate the developed algorithm. (C) 2015 Elsevier B.V. All rights reserved.
2016-03-31T11:20:03ZGarcía Espinosa, JulioCapua, Daniel diServán Camas, BorjaUbach Fuentes, Pere-AndreuOñate Ibáñez de Navarra, EugenioThis paper shows the recent work of the authors in the development of a time-domain FEM model for evaluation of the seal dynamics of a surface effect ship. The fluid solver developed for this purpose, uses a potential flow approach along with a streamline integration of the free surface. The paper focuses on the free surface-structure algorithm that has been developed to allow the simulation of the complex and highly dynamic behaviour of the seals in the interface between the air cushion, and the water.; The developed fluid-structure interaction solver is based, on one side, on an implicit iteration algorithm, communicating pressure forces and displacements of the seals at memory level and, on the other side, on an innovative wetting and drying scheme able to predict the water action on the seals. The stability of the iterative scheme is improved by means of relaxation, and the convergence is accelerated using Aitken's method.; Several validations against experimental results have been carried out to demonstrate the developed algorithm. (C) 2015 Elsevier B.V. All rights reserved.A review of pelvic fractures in adult pedestrians: Experimental studies involving PMHS used to determine injury criteria for pedestrian dummies and component test procedures
http://hdl.handle.net/2117/84835
A review of pelvic fractures in adult pedestrians: Experimental studies involving PMHS used to determine injury criteria for pedestrian dummies and component test procedures
Arregui Dalmases, Carlos; Kerrigan, Jason; Sánchez Molina, David; Velázquez Ameijide, Juan; Crandall, Jeff R.
Objectives: Perform a systematic review for the most relevant pelvic injury research involving PMHS. The review begins with an explanation of the pelvic anatomy and a general description of pelvic fracture patterns followed by the particular case of pelvic fractures sustained in pedestrian-vehicle collisions. Field data documenting the vehicle, crash, and human risk factors for pedestrian pelvic injuries are assessed.
Method: A summary of full-scale PMHS tests and subsystem lateral pelvic tests is provided with an interpretation of the most significant findings for the most relevant studies.
Conclusions: Based on the mechanisms of pedestrian pelvic injury, force, acceleration, and velocity and compression have been
assessed as predictive variables by researchers although no consensus criterion exists.
2016-03-30T07:58:10ZArregui Dalmases, CarlosKerrigan, JasonSánchez Molina, DavidVelázquez Ameijide, JuanCrandall, Jeff R.Objectives: Perform a systematic review for the most relevant pelvic injury research involving PMHS. The review begins with an explanation of the pelvic anatomy and a general description of pelvic fracture patterns followed by the particular case of pelvic fractures sustained in pedestrian-vehicle collisions. Field data documenting the vehicle, crash, and human risk factors for pedestrian pelvic injuries are assessed.
Method: A summary of full-scale PMHS tests and subsystem lateral pelvic tests is provided with an interpretation of the most significant findings for the most relevant studies.
Conclusions: Based on the mechanisms of pedestrian pelvic injury, force, acceleration, and velocity and compression have been
assessed as predictive variables by researchers although no consensus criterion exists.Ferritic stainless steel composite slabs : Experimental study of longitudinal shear transfer
http://hdl.handle.net/2117/83863
Ferritic stainless steel composite slabs : Experimental study of longitudinal shear transfer
Ferrer Ballester, Miquel; Marimón Carvajal, Federico; Arrayago Luquin, Itsaso; Mirambell Arrizabalaga, Enrique
The objective of this work is to carry out the procedure described in Eurocode 4 to evaluate the longitudinal shear transfer capability of conventional steel sheeting open-rib profile with embossments, usually rolled in conventional galvanized steel, being rolled now in ferritic stainless steel 1.4003 alloy. Finally, the results of both composite floor slabs are compared.
Two methodologies have been used to evaluate the longitudinal shear resistance in composite slabs, the m-k method and the partial connection method.
The developed tasks are the following:
-Construction and test of 6 slabs using ferritic stainless steel sheeting: 3 short and 3 long span lengths.
-Construction and test of 2 slabs using galvanized steel sheeting: 1 short and 1 long span lengths.
-Tensile tests of both stainless steel and galvanized sheeting as well as compression tests on concrete.
-Determination of the m-k parameters and ultimate shear stress for stainless steel slabs.
-Comparison of results between stainless steel and galvanized steel sheeting
2016-03-07T07:59:35ZFerrer Ballester, MiquelMarimón Carvajal, FedericoArrayago Luquin, ItsasoMirambell Arrizabalaga, EnriqueThe objective of this work is to carry out the procedure described in Eurocode 4 to evaluate the longitudinal shear transfer capability of conventional steel sheeting open-rib profile with embossments, usually rolled in conventional galvanized steel, being rolled now in ferritic stainless steel 1.4003 alloy. Finally, the results of both composite floor slabs are compared.
Two methodologies have been used to evaluate the longitudinal shear resistance in composite slabs, the m-k method and the partial connection method.
The developed tasks are the following:
-Construction and test of 6 slabs using ferritic stainless steel sheeting: 3 short and 3 long span lengths.
-Construction and test of 2 slabs using galvanized steel sheeting: 1 short and 1 long span lengths.
-Tensile tests of both stainless steel and galvanized sheeting as well as compression tests on concrete.
-Determination of the m-k parameters and ultimate shear stress for stainless steel slabs.
-Comparison of results between stainless steel and galvanized steel sheetingUnified lagrangian formulation for fluid and solid mechanics, fluid-structure interaction and coupled thermal problems using the PFEM
http://hdl.handle.net/2117/82977
Unified lagrangian formulation for fluid and solid mechanics, fluid-structure interaction and coupled thermal problems using the PFEM
Franci, Alessandro; Oñate Ibáñez de Navarra, Eugenio; Carbonell Puigbó, Josep Maria
The objective of this work is the derivation and implementation of a unifed Finite Element formulation for the solution of uid and solid mechanics, Fluid-Structure Interaction (FSI) and coupled thermal problems.
2016-02-15T19:37:06ZFranci, AlessandroOñate Ibáñez de Navarra, EugenioCarbonell Puigbó, Josep MariaThe objective of this work is the derivation and implementation of a unifed Finite Element formulation for the solution of uid and solid mechanics, Fluid-Structure Interaction (FSI) and coupled thermal problems.Improving mesh generation in finite element analysis for functional morphology approaches
http://hdl.handle.net/2117/82900
Improving mesh generation in finite element analysis for functional morphology approaches
Marcé Nogué, Jordi; Fortuny Terricabras, Josep; Gil Espert, Lluís; Sánchez Romero, Montserrat
Finite Element Analysis (FEA) is a powerful tool for functional morphology purposes. The accuracy of the final results depends on the mesh generation and the quality of the mesh. This is especially important in vertebrates as they present a complex biological structure, implying a complex geometry and, consequently, mesh generation should be performed with a consistent criterion. The aim of this paper is to discuss different ways to create a mesh of a vertebrate structure with different mesh generation methods and give recommendations on how to generate an efficient mesh without exceeding computational limits. Topics such as quality of the mesh, suitability of the mesh and reliability of the mesh are introduced to help the generation of the mesh. In this case, the use of convergence procedures assures the results of the computational solution and can be a good solution for the vertebrate models. The skull of a Chinese giant salamander (Andrias davidianus) is used as a case study.
2016-02-12T15:39:19ZMarcé Nogué, JordiFortuny Terricabras, JosepGil Espert, LluísSánchez Romero, MontserratFinite Element Analysis (FEA) is a powerful tool for functional morphology purposes. The accuracy of the final results depends on the mesh generation and the quality of the mesh. This is especially important in vertebrates as they present a complex biological structure, implying a complex geometry and, consequently, mesh generation should be performed with a consistent criterion. The aim of this paper is to discuss different ways to create a mesh of a vertebrate structure with different mesh generation methods and give recommendations on how to generate an efficient mesh without exceeding computational limits. Topics such as quality of the mesh, suitability of the mesh and reliability of the mesh are introduced to help the generation of the mesh. In this case, the use of convergence procedures assures the results of the computational solution and can be a good solution for the vertebrate models. The skull of a Chinese giant salamander (Andrias davidianus) is used as a case study.Numerical simulation of penetration problems in geotechnical engineering with the particle finite element method (PFEM)
http://hdl.handle.net/2117/82878
Numerical simulation of penetration problems in geotechnical engineering with the particle finite element method (PFEM)
Monforte Vila, Lluís; Carbonell Puigbó, Josep Maria; Arroyo Alvarez de Toledo, Marcos; Gens Solé, Antonio
This paper highlights a computational framework for the numerical analysis of saturated soil-structure interaction problems. The variational equations of linear momentum and mass balance are obtained for the large deformation case. These equations are solved using the Particle Finite Element Method. The paper concludes with a benchmark test and the analysis of a penetration test.
2016-02-11T19:31:27ZMonforte Vila, LluísCarbonell Puigbó, Josep MariaArroyo Alvarez de Toledo, MarcosGens Solé, AntonioThis paper highlights a computational framework for the numerical analysis of saturated soil-structure interaction problems. The variational equations of linear momentum and mass balance are obtained for the large deformation case. These equations are solved using the Particle Finite Element Method. The paper concludes with a benchmark test and the analysis of a penetration test.The particle finite element method (PFEM) in thermo-mechanical problems
http://hdl.handle.net/2117/82652
The particle finite element method (PFEM) in thermo-mechanical problems
Rodríguez, J.M.; Carbonell Puigbó, Josep Maria; Cante Terán, Juan Carlos; Oliver Olivella, Xavier
The aim of this work is to develop a numerical framework for accurately and robustly simulating the different conditions exhibited by thermo-mechanical problems. In particular, the work will focus on the analysis of problems involving large strains, rotations, multiple contacts, large boundary surface changes, and thermal effects.
The framework of the numerical scheme is based on the particle finite element method (PFEM) in which the spatial domain is continuously redefined by a distinct nodal reconnection, generated by a Delaunay triangulation. In contrast to classical PFEM calculations, in which the free boundary is obtained by a geometrical procedure (a - shape method), in this work, the boundary is considered as a material surface, and the boundary nodes are removed or inserted by means of an error function.
The description of the thermo-mechanical constitutive model is based on the concepts of large strains plasticity. The plastic flow condition is assumed nearly incompressible, so a u-p mixed formulation, with a stabilization of the pressure term via the polynomial pressure projection, is proposed.
One of the novelties of this work is the use of a combination between the isothermal split and the so-called IMPL-EX hybrid integration technique to enhance the robustness and reduce the typical iteration number of the fully implicit Newton–Raphson solution algorithm.
The new set of numerical tools implemented in the PFEM algorithm, including new discretization techniques, the use of a projection of the variables between meshes, and the insertion and removal of points allows us to eliminate the negative Jacobians present during large deformation problems, which is one of the drawbacks in the simulation of coupled thermo-mechanical problems.
Finally, two sets of numerical results in 2D are stated. In the first one, the behavior of the proposed locking-free element type and different time integration schemes for thermo-mechanical problems is analyzed. The potential of the method for modeling more complex coupled problems as metal cutting and metal forming processes is explored in the last example.
This is the accepted version of the following article: [Rodriguez, J. M., Carbonell, J. M., Cante, J. C., and Oliver, J. (2016) The particle finite element method (PFEM) in thermo-mechanical problems. Int. J. Numer. Meth. Engng, doi: 10.1002/nme.5186.], which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1002/nme.5186/full
2016-02-05T18:51:22ZRodríguez, J.M.Carbonell Puigbó, Josep MariaCante Terán, Juan CarlosOliver Olivella, XavierThe aim of this work is to develop a numerical framework for accurately and robustly simulating the different conditions exhibited by thermo-mechanical problems. In particular, the work will focus on the analysis of problems involving large strains, rotations, multiple contacts, large boundary surface changes, and thermal effects.
The framework of the numerical scheme is based on the particle finite element method (PFEM) in which the spatial domain is continuously redefined by a distinct nodal reconnection, generated by a Delaunay triangulation. In contrast to classical PFEM calculations, in which the free boundary is obtained by a geometrical procedure (a - shape method), in this work, the boundary is considered as a material surface, and the boundary nodes are removed or inserted by means of an error function.
The description of the thermo-mechanical constitutive model is based on the concepts of large strains plasticity. The plastic flow condition is assumed nearly incompressible, so a u-p mixed formulation, with a stabilization of the pressure term via the polynomial pressure projection, is proposed.
One of the novelties of this work is the use of a combination between the isothermal split and the so-called IMPL-EX hybrid integration technique to enhance the robustness and reduce the typical iteration number of the fully implicit Newton–Raphson solution algorithm.
The new set of numerical tools implemented in the PFEM algorithm, including new discretization techniques, the use of a projection of the variables between meshes, and the insertion and removal of points allows us to eliminate the negative Jacobians present during large deformation problems, which is one of the drawbacks in the simulation of coupled thermo-mechanical problems.
Finally, two sets of numerical results in 2D are stated. In the first one, the behavior of the proposed locking-free element type and different time integration schemes for thermo-mechanical problems is analyzed. The potential of the method for modeling more complex coupled problems as metal cutting and metal forming processes is explored in the last example.Coupling finite element analysis and multibody system dynamics for biological research
http://hdl.handle.net/2117/81689
Coupling finite element analysis and multibody system dynamics for biological research
Marcé Nogué, Jordi; Klodowski, Adam; Sánchez Romero, Montserrat; Gil Espert, Lluís
Flexible Multibody System Dynamics (FMSD) is a simulation technique that can be used to study the behavior of the mechanical systems that consists of one or more deformable bodies. A deformable body can be modeled using a number of approaches while the floating frame of reference formulation is a widely used approach. In that approach, flexibility within Multibody System Dynamics (MSD) is described by employing the Finite Element Analysis (FEA) with a modal reduction approach. The applicability of an FMSD in the feeding mechanism of vertebrate structures is tested in order to utilize the potential of the method in biological research. Flexible Multibody System Dynamics is explored studying the feeding mechanism in a skull of Edingerella madagascariensis. Firstly, a static structural analysis is done using FEA and secondly, dynamic solutions based on FMSD are obtained by varying the number of deformation modes used in the modal reduction analysis. The conclusion is that use of this approach is feasible and efficient for the study of feeding mechanisms in vertebrate structures when a dynamic response should be evaluated.
2016-01-19T15:30:51ZMarcé Nogué, JordiKlodowski, AdamSánchez Romero, MontserratGil Espert, LluísFlexible Multibody System Dynamics (FMSD) is a simulation technique that can be used to study the behavior of the mechanical systems that consists of one or more deformable bodies. A deformable body can be modeled using a number of approaches while the floating frame of reference formulation is a widely used approach. In that approach, flexibility within Multibody System Dynamics (MSD) is described by employing the Finite Element Analysis (FEA) with a modal reduction approach. The applicability of an FMSD in the feeding mechanism of vertebrate structures is tested in order to utilize the potential of the method in biological research. Flexible Multibody System Dynamics is explored studying the feeding mechanism in a skull of Edingerella madagascariensis. Firstly, a static structural analysis is done using FEA and secondly, dynamic solutions based on FMSD are obtained by varying the number of deformation modes used in the modal reduction analysis. The conclusion is that use of this approach is feasible and efficient for the study of feeding mechanisms in vertebrate structures when a dynamic response should be evaluated.Insights into the controversy over materials data for the comparison of biomechanical performance in vertebrates
http://hdl.handle.net/2117/81679
Insights into the controversy over materials data for the comparison of biomechanical performance in vertebrates
Gil Espert, Lluís; Marcé Nogué, Jordi; Sánchez Romero, Montserrat
Mechanical comparison of different species is performed with the help of computational tools like Finite Element Analysis FEA. In palaeobiology it is common to consider bone like an isotropic material for simulations but often real data of bone materials is impossible to know. This work investigates the influence of choice of bone materials properties over the results of simulations, showing when and why the materials data are relevant and when the selection of these data becomes irrelevant. With a theoretical approach from continuum mechanics and with a practical example the relationship between material data and comparative metrics like stress, strains and displacements is discussed. When linear and elastic material properties are assumed in a comparative analysis, the effect of the elastic modulus of the material is irrelevant over stress patterns. This statement is true for homogeneous and inhomogeneous materials, in this last case the proportion between the different materials properties must kept constant. In the case of the strains and displacements, there is an inverse proportionality kept constant, between the values of the metrics and the changes in the elastic modulus. These properties allow comparative studies without considering the real elastic materials properties.
2016-01-19T13:47:08ZGil Espert, LluísMarcé Nogué, JordiSánchez Romero, MontserratMechanical comparison of different species is performed with the help of computational tools like Finite Element Analysis FEA. In palaeobiology it is common to consider bone like an isotropic material for simulations but often real data of bone materials is impossible to know. This work investigates the influence of choice of bone materials properties over the results of simulations, showing when and why the materials data are relevant and when the selection of these data becomes irrelevant. With a theoretical approach from continuum mechanics and with a practical example the relationship between material data and comparative metrics like stress, strains and displacements is discussed. When linear and elastic material properties are assumed in a comparative analysis, the effect of the elastic modulus of the material is irrelevant over stress patterns. This statement is true for homogeneous and inhomogeneous materials, in this last case the proportion between the different materials properties must kept constant. In the case of the strains and displacements, there is an inverse proportionality kept constant, between the values of the metrics and the changes in the elastic modulus. These properties allow comparative studies without considering the real elastic materials properties.