Oller Martinez, Sergio Horacio
Total activity: 570
Areas of expertise
Prof. Structures and Continuum Mechanics
h index
26
Professional category
University professor
Doctoral courses
Dr. Ingeniero de Caminos, Canales y Puertos
University degree
Ingeniero en Construcciones (Homologado al Título de Ing. de Caminos)
Postgraduated qualification
Especialidad en Métodos Avanzados de Análisis y Diseño de Estructuras.
Research group
RMEE - Strength of Materials and Structural Engineering Group
Department
Department of Strength of Materials and Structural Engineering
School
Barcelona School of Civil Engineering (ETSECCPB)
Associated research bodies
CIMNE. Centre Internacional de Mètodes Numèrics en Enginyeria Open in new window
E-mail
sergio.ollerupc.edu
Contact details
UPC directory Open in new window
Orcid
0000-0002-5203-8903 Open in new window
Scopus Author ID
7003881173 Open in new window
Links of interest
Google Scholar Open in new window
ResearchGate Open in new window
Researcher ID Open in new window

Graphic summary
  • Show / hide key
  • Information


Scientific and technological production
  •  

1 to 50 of 570 results
  • Optimization method for the determination of material parameters in damaged composite structures

     Comellas Sanfeliu, Ester; Valdez Peña, Sergio Ivvan; Oller Martinez, Sergio Horacio; Botello, S.
    Composite structures
    Vol. 122, p. 417-424
    DOI: 10.1016/j.compstruct.2014.12.014
    Date of publication: 2015-04
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    An optimization method to identify the material parameters of composite structures using an inverse method is proposed. This methodology compares experimental results with their numerical reproduction using the finite element method in order to obtain an estimation of the error between the results. This error estimation is then used by an evolutionary optimizer to determine, in an iterative process, the value of the material parameters which result in the best numerical fit. The novelty of the method is in the coupling between the simple genetic algorithm and the mixing theory used to numerically reproduce the composite behavior. The methodology proposed has been validated through a simple example which illustrates the exploitability of the method in relation to the modeling of damaged composite structures.

    Postprint (author’s final draft)

  • Numerical homogenization for composite materials analysis: comparison with other micro mechanical formulations

     Otero Gruer, Fermin Enrique; Oller Martinez, Sergio Horacio; Martinez Garcia, Xavier; Salomon, Ramon Omar
    Composite structures
    Vol. 122, p. 405-416
    DOI: 10.1016/j.compstruct.2014.11.041
    Date of publication: 2015-04
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    This work presents a two-scale homogenization procedure to analyze three dimension composite structures by FEM. The theory implemented is compared with other micro-structural formulations: micro models and serial parallel mixing theory, in terms of result accuracy and computational cost. The comparison shows that for linear analysis, the homogenization is an excellent alternative to the other formulations. Its computational cost is substantially lower than the one required by the micro-model and it is able to capture several micro-structural phenomena that it is not automatically recorded by the serial parallel methodology. It will also be shown that the extension of the proposed theory to the non-linear range stills represents a challenge. The major limitation is its computational cost because it requires to solve the sub scale at each gauss point and load step. However, the comparison shows that this cost is in terms of CPU time but not in terms of memory. Based on the results obtained, it can be concluded that the homogenization is an excellent alternative for simulation of materials with complex micro structures. The method is also very promising for non linear simulations, when coupled with a threshold criteria to decide whether it is necessary to analyze the RVE or not. (C) 2014 Elsevier Ltd. All rights reserved.

    Postprint (author’s final draft)

  • Formulation of enriched macro elements using trigonometric shear deformation theory for free vibration analysis of symmetric laminated composite plate assemblies

     Rango, Rita F.; Nallim, Liz G.; Oller Martinez, Sergio Horacio
    Composite structures
    Vol. 119, p. 38-49
    DOI: 10.1016/j.compstruct.2014.08.012
    Date of publication: 2015-01
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    The formulation of an enriched macro element suitable to analyze the free vibration response of composite plate assemblies is presented in this article. Based on the Trigonometric Shear Deformation Theory (TSDT) and the use of Gram-Schmidt orthogonal polynomials as enrichment functions a finite macro element is developed. In the TSDT framework, shear stresses are vanished at the top and bottom surfaces of the plates and shear correction factors are no longer required. The Principle of Virtual Work is applied to derive the governing equations of motion. A special connectivity matrix is obtained; so that hierarchically enriched global stiffness matrix and mass matrix of general laminated plate structures are derived, allowing to study generally coplanar plate assemblies by combining two or more macro elements. This procedure gives a matrix-eigenvalue problem that can be solved with optimum efficiency. Results of free vibration analysis for symmetric laminated plates of different thickness ratios, geometrical planform shapes and boundary conditions are presented. The accuracy of the formulation is ensured by comparing some numerical examples with those available in the literature.

  • A finite points method approach for strain localization using the gradient plasticity formulation

     Perez Pozo, Luis; Campos, Andy; Lascano, S; Oller Martinez, Sergio Horacio; Rodriguez Ferran, Antonio
    Mathematical problems in engineering
    Vol. 2014, p. 782079-1-782079-12
    DOI: 10.1155/2014/782079
    Date of publication: 2014-12
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    The softening elastoplastic models present an unsuitable behavior after reaching the yield strength: unbounded strain localization. Because of the material instability, which is reflected in the loss of ellipticity of the governing partial differential equations, the solution depends on the discretization. The present work proposes to solve this dependency using the meshless Finite Points Method. This meshfree spatial discretization technique allows enriching the governing equations using gradient's plasticity and introducing an internal length scale parameter at the material model in order to objectify the solution.

  • Formulación de elementos finitos para vigas de sección abierta formadas por laminados compuestos incluyendo las deformaciones tangenciales por cortante y torsión

     Oñate Ibáñez de Navarra, Eugenio; Oller Martinez, Sergio Horacio; Vargas, P. E.
    Revista internacional de métodos numéricos para cálculo y diseño en ingeniería
    Vol. 30, num. 4, p. 238-246
    DOI: 10.1016/j.rimni.2013.07.007
    Date of publication: 2014-10
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    In this paper we derive the field of displacements and strains for thin-walled open composite beams with composite laminated material including in their kinematics flexural and torsional shear deformations effects. The equilibrium equations are defined through the variational formulation and show that is possible to formulate C-o finite elements taking into account the torsional shear deformation. Stressstrain relationships for the cross-section of thin-walled composite beams are obtained by extending first-order laminate (FSDT: first-order shear deformation) theory and using a "free stress resultant condition at the boundary". Three different one-dimensional finite elements with C-o continuity are formulated for the study of thin-walled open composite beams and they are labelled as BSW (beam with shear and warping). The influence of the integration strategy in the BSW elements is evaluated via the shear-locking phenomenon and the rate of convergence for displacements and rotations. The stiffness matrix integration is compared using exact and reduced integration methods. Examples of pure torsion and flexo-torsion in a cantilever composite beam are performed. Numerical results are compared to those reported by other authors. (C) 2013 CIMNE (Universitat Politecnica de Catalunya). Published by Elsevier Espana, S.L.U. All rights reserved.

  • Finite element modeling of delamination in advanced composite beams and plates using one- and two-dimensional finite elements based on the refined zigzag theory

     Eijo, Ariel
    Universitat Politècnica de Catalunya
    Theses

    Read the abstract Read the abstract  Share Reference managers Reference managers Open in new window

    Aunque los materiales laminados se han utilizado durante décadas, su uso ha aumentado en los últimos años como resultado de una mayor confianza por parte de la industria. Esto ha proporcionado a la comunidad científica muchas razones para dedicar una considerable cantidad de tiempo y esfuerzos en aras de una mejor comprensión de su comportamiento mecánico. Con este objetivo tanto la simulación experimental como numérica han estado trabajando juntos para dar respuesta a una variedad de problemas relacionados con estos materiales.En cuanto a la simulación numérica, un correcto modelado de la cinemática de los materiales laminados es esencial para capturar el comportamiento real de la estructura. Por otra parte, una vez que la cinemática de la estructura se ha predicho con precisión otros fenómenos no lineales como los proceso de daño y/o plasticidad podrían ser también estudiados.En consecuencia, con el fin de contribuir al constante desarrollo de herramientas numéricas más simples y eficaces para modelar materiales laminados, un método numérico para el modelado de la delaminación (modo II/III) en materiales compuestos avanzados utilizando elementos finitos de una y dos dimensiones es propuesto en este trabajo. Además, dos elementos finitos para la simulación de vigas y placas de varias capas altamente heterogéneos son desarrollados aquí.El documento está escrito en base a los resultados de cuatro artículos publicados en revistas indexadas. Copias de estos artículos se incluyen en el Apéndice. El cuerpo principal de esta tesis está constituido por los Capítulos 2-4. El Capítulo 2 aborda el tratamiento numérico de vigas y placas laminadas. El capítulo 3 presenta la formulación de los elementos finitos de viga LRZ y placa QLRZ basados en la Teoría Zigzag Refinada. Finalmente, la principal contribución de esta tesis, el modelo de delaminación LRZ/QLRZ, se desarrolla en el capítulo 4.

  • Access to the full text
    Coupled plastic damage model for low and ultra-low cycle seismic fatigue  Open access

     Barbu, Lucia Gratiela; Oller Martinez, Sergio Horacio; Martinez Garcia, Xavier; Barbat Barbat, Horia Alejandro
    World Congress on Computational Mechanics
    p. 2955-2966
    Presentation's date: 2014-07-21
    Presentation of work at congresses

    Read the abstract Read the abstract Access to the full text Access to the full text Open in new window  Share Reference managers Reference managers Open in new window

    This paper presents the theoretical framework for a coupled plastic damage constitutive model valid for materials subjected to cyclic loads that lead to low and ultra-low cycle fatigue. Two numerical examples were presented in order to illustrate the behaviour of the model and its capabilities.

  • Access to the full text
    Comparative experimental analysis of the effect caused by artificial and real induced damage in composite laminates  Open access

     Pérez Martínez, Marco Antonio; Gil Espert, Lluis; Sanchez Romero, Montserrat; Oller Martinez, Sergio Horacio
    Composite structures
    Vol. 112, p. 169-178
    DOI: 10.1016/j.compstruct.2014.02.017
    Date of publication: 2014-06-02
    Journal article

    Read the abstract Read the abstract Access to the full text Access to the full text Open in new window  Share Reference managers Reference managers Open in new window

    This paper presents the results of an extensive experimental campaign aimed to examine the effect upon the vibration response and on the residual load-bearing capacity caused by both: isolated artificially induced interlaminar damage and low-velocity impact induced damage in composite laminates. The experimental programme included modal testing, drop-weight impact testing, ultrasonic inspection, transverse quasi-static loading testing and compression testing conducted on a set of 72 carbon fibre-reinforced composite laminated coupons. Both types of damage caused measurable changes in laminate performance, however marked divergent trends were observed. The results allowed for conclusions to be drawn regarding the adequacy of the artificial damage approach and highlighted the importance and role of other forms of degradation upon damage tolerance of laminated composites containing damage.

  • A localized mapped damage model for orthotropic materials

     Pelà, Luca; Cervera Ruiz, Miguel; Oller Martinez, Sergio Horacio; Chiumenti, Michele
    Engineering fracture mechanics
    Vol. 124-125, p. 196-216
    DOI: 10.1016/j.engfracmech.2014.04.027
    Date of publication: 2014-05-08
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    This paper presents an implicit orthotropic model based on the Continuum Damage Mechanics isotropic models. A mapping relationship is established between the behaviour of the anisotropic material and that of an isotropic one. The proposed model is used to simulate the failure loci of common orthotropic materials, such as masonry, fibre-reinforced composites and wood. The damage model is combined with a crack-tracking technique to reproduce the propagation of localized cracks in the discrete FE problem. The proposed numerical model is used to simulate the mixed mode fracture in masonry members with different orientations of the brick layers.

  • Modelización del comportamiento de estructuras mediante la teoría de homogeneización

     Quinteros, Ricardo D.
    National University of Salta
    Theses

    Read the abstract Read the abstract  Share Reference managers Reference managers Open in new window

    Esta tesis se focaliza en el análisis y desarrollo de técnicas de homogenización ad-hoc para resolver el problema de representar el comportamiento estructural de muros de mampostería, aprovechando la configuración periódica que sus materiales y distribución le confieren. Mediante estas técnicas, es posible derivar el comportamiento global de la estructura a partir del comportamiento de los materiales constituyentes (ladrillo y mortero) adoptando modelos constitutivos diferentes para cada uno de ellos. Se realizan diversos ejemplos de validación para los modelos propuestos mediante la simulación de ensayos sencillos y curvas de falla del material compuesto. Se realizan además simulaciones de estructuras de paneles de mampostería con diversas configuraciones geométricas y mecánicas, sometidos a varias tipologías de cargas, para analizar el comportamiento mediante la comparación con resultados experimentales presentes en la bibliografía y/o otros modelos desarrollados por otros autores.

  • Impact damage identification in composite laminates using vibration testing

     Pérez Martínez, Marco Antonio; Gil Espert, Lluis; Oller Martinez, Sergio Horacio
    Composite structures
    Vol. 108, p. 267-276
    DOI: 10.1016/j.compstruct.2013.09.025
    Date of publication: 2014-02
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    Due to the problems arising from impact damage in composite laminates, there is a need to develop fast, accurate, cost-effective and non-destructive testing methods to identify this type of damage at an early stage and thus enhance the service life of composite structures. This paper presents the results of an extensive experimental campaign conducted to investigate the feasibility of using vibration-based meth- ods to identify damages sustained by composite laminates due to low-velocity impacts. The experimental programme included an evaluation of impact damage resistance and tolerance according to ASTM test methods, characterisation of induced damage by ultrasonic testing and quantification of the effects on the vibration response. The damage identification involved the detection, localisation, quantification and estimation of the remaining bearing capacity. Four damage indicators based on modal parameters were assessed by comparing pristine and damaged states. The results allowed for conclusions to be drawn regarding the capability and suitability of each damage indicator, including its ability to detect impact-induced damage, its precision in determining the location of damage, its sensitivity regarding damage extent and pertinent correlations with residual bearing capacity.

    Due to the problems arising from impact damage in composite laminates, there is a need to develop fast, accurate, cost-effective and non-destructive testing methods to identify this type of damage at an early stage and thus enhance the service life of composite structures. This paper presents the results of an extensive experimental campaign conducted to investigate the feasibility of using vibration-based methods to identify damages sustained by composite laminates due to low-velocity impacts. The experimental programme included an evaluation of impact damage resistance and tolerance according to ASTM test methods, characterisation of induced damage by ultrasonic testing and quantification of the effects on the vibration response. The damage identification involved the detection, localisation, quantification and estimation of the remaining bearing capacity. Four damage indicators based on modal parameters were assessed by comparing pristine and damaged states. The results allowed for conclusions to be drawn regarding the capability and suitability of each damage indicator, including its ability to detect impact-induced damage, its precision in determining the location of damage, its sensitivity regarding damage extent and pertinent correlations with residual bearing capacity.

  • Delamination in laminated plates using the 4-noded quadrilateral QLRZ plate element based on the refined zigzag theory

     Eijo, Ariel; Oñate Ibáñez de Navarra, Eugenio; Oller Martinez, Sergio Horacio
    Composite structures
    Vol. 108, p. 456-471
    DOI: 10.1016/j.compstruct.2013.09.052
    Date of publication: 2014-02
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    A numerical method based on the Refined Zigzag Theory (RZT) to model delamination in composite laminated plate/shell structures is presented. The originality of this method is the use of 4-noded quadrilateral plate finite elements whit only seven variables per node to discretize the plate/shell geometry. The ability to capture the relative displacement between consecutive layers in fracture mode II and III is the more important advantage of this element, denoted QLRZ. A continuum isotropic damage model is used to model the mechanical behavior of the plies. The material non-lineal problem is solved with the modified Newton–Raphson method. The RZT plate theory, the QLRZ finite element and the isotropic damage model are described in this work. Also, the implicit integration algorithm is presented. The performance of the numerical model is analyzed by studying the delamination in a rectangular plate for two different laminates, using the 3D analysis as the reference solution.

  • Grup de resistència de materials i estructures a l'enginyeria

     Agelet de Saracibar Bosch, Carlos; Barbat Barbat, Horia Alejandro; Bugeda Castelltort, Gabriel; Cervera Ruiz, Miguel; Chiumenti, Michele; Oller Martinez, Sergio Horacio; Suarez Arroyo, Benjamin; Miquel Canet, Juan; Cante Teran, Juan Carlos; Hernandez Ortega, Joaquin Alberto; González Lopez, Jose Manuel; Martinez Garcia, Xavier; Escudero Torres, Cuauhtemoc; Morillo Guzman, Carlos; Huespe, Alfredo Edmundo; Carbonell Puigbo, Josep Maria; Rossi, Riccardo; Otero Gruer, Fermin Enrique; Comellas Sanfeliu, Ester; Barbu, Lucia Gratiela; Oliver Olivella, Fco. Javier
    Competitive project

     Share

  • Numerical solution of the equations of motion of multi-story buildings with severe nonlinearities

     Lopez Almansa, Francisco; Oller Martinez, Sergio Horacio
    Revista internacional de métodos numéricos para cálculo y diseño en ingeniería
    Vol. 30, num. 3, p. 194-202
    DOI: 10.1016/j.rimni.2013.06.007
    Date of publication: 2014-01-01
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    This paper presents a new algorithm for solving the equations of motion of multi-storey buildings that incorporate frictional energy dissipators as seismic protection. The behavior of the dissipators is represented by Coulomb dry friction models; they introduce severe nonlinearities in the dynamic behavior of the structure every time that the contact conditions (stick or slip) change in the dissipators. These nonlinearities complicate the resolution of the equations of motion as it usually is described by lumped masses models whose degrees of freedom are the displacements of the floors and, as the stick or slip conditions change, the degrees of freedom must be modified: for blocking conditions they are only the displacements of the storeys while under sliding conditions the displacements of the dissipators have to be also considered. In previous articles the accuracy of the proposed algorithm has been verified by comparison with experimental results; as well, the computational efficiency of the algorithm has been confirmed by comparing the required resources (in terms of computation time and of memory allocation) with those of other algorithms. The objectives of this paper are to describe in detail the numerical solution of the equations of motion and present representative examples confirming the ability of the algorithm to reproduce the dynamic behavior of buildings with friction dissipators and reporting preliminarily about the usefulness of such devices to reduce the oscillations of the structure to be protected. (C) 2013 CIMNE (Universitat Politecnica de Catalunya). Published by Elsevier Espana, S.L. All rights reserved.

  • Numerical modelling of the cyclic structural behavior of slender steel members with restrained buckling

     Castro Medina, J. C.; Lopez Almansa, Francisco; Oller Martinez, Sergio Horacio
    Revista internacional de métodos numéricos para cálculo y diseño en ingeniería
    Vol. 30, num. 4, p. 229-237
    DOI: 10.1016/j.rimni.2013.07.008
    Date of publication: 2014-01-01
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    This work presents a numerical model of the cyclic structural behavior of dissipative buckling-restrained braces, commonly used as an alternative to classical concentric braces for seismic protection of building frames and other structures. Such devices are usually composed of a slender steel core embedded in a stockiest casing that is intended to prevent its buckling when it is under compression. The casing is made either of mortar or steel, and a sliding interface is interposed between the core and the casing to prevent excessive shear stress transfer. The behavior of the steel core is described by a damage and plasticity model; the behavior of the mortar casing is described by an isotropic damage model and the sliding behavior of the interface is described by a contact penalty model. These 3 models are implemented in the Abaqus software package following an explicit formulation. In a previous article (published in an earthquake engineering journal) the model was briefly described, its ability to reproduce the cyclical behavior of buckling-restrained braces was preliminarily pointed out and their results were satisfactorily compared with those of experimental tests. The aim of this paper is to describe the model thoroughly and to present new judgments about its usefulness. (C) 2013 CIMNE (Universitat Politecnica de Catalunya). Published by Elsevier Espana, S.L.U. All rights reserved.

  • Access to the full text
    Análisis no-lineal de materiales compuestos mediante la teoría de mezclas serie-paralelo  Open access

     Martinez Garcia, Xavier; Oller Martinez, Sergio Horacio; Rastellini Canela, Fernando Gabriel
    DOI: 10.3926/oms.210
    Date of publication: 2014
    Book chapter

    Read the abstract Read the abstract Access to the full text Access to the full text Open in new window  Share Reference managers Reference managers Open in new window

    El propósito de esta obra es aportar una visión global del estado actual de la técnica y los recientes desarrollos sobre la aplicabilidad de los materiales compuestos en la obra civil y la edificación. El libro recoge una colección de trabajos de investigación de expertos nacionales e internacionales, que abordan los retos actuales y futuros en este campo, proporcionando, a través de una amplia variedad de casos de estudio, una hoja de ruta con las habilidades técnicas y los conocimientos prácticos necesarios para el empleo de materiales compuestos en nuevas aplicaciones. Los textos son –en la medida de lo posible– autocontenidos en sus partes, permitiendo una lectura acorde al interés particular de cada lector. En ellos se presentan fundamentos técnicos, resultados de investigaciones, y se revisan y compilan referencias bibliográficas actualizadas que complementan y permiten al lector adquirir un conocimiento más profundo de los temas expuestos, encaminándolo hacia posibles futuras líneas de investigación. Escrito por profesionales e investigadores con experiencia en este campo, este libro pretende ser un texto de referencia para los no iniciados en la temática y una herramienta de estudio e investigación para lectores de niveles más avanzados.

    Este libro presenta una panorámica del estado actual de los materiales compuestos y sus aplicaciones más relevantes en la obra civil y la edificación.

  • Access to the full text
    Análisis numérico de la reparación y refuerzo de estructuras con FRP  Open access

     Oller Martinez, Sergio Horacio; Molina, Maritzabel; Vielma Pérez, Juan Carlos; Martinez Garcia, Xavier; Barbat Barbat, Horia Alejandro; Nallim, Liz G.
    DOI: 10.3926/oms.210
    Date of publication: 2014
    Book chapter

    Read the abstract Read the abstract Access to the full text Access to the full text Open in new window  Share Reference managers Reference managers Open in new window

    El propósito de esta obra es aportar una visión global del estado actual de la técnica y los recientes desarrollos sobre la aplicabilidad de los materiales compuestos en la obra civil y la edificación. El libro recoge una colección de trabajos de investigación de expertos nacionales e internacionales, que abordan los retos actuales y futuros en este campo, proporcionando, a través de una amplia variedad de casos de estudio, una hoja de ruta con las habilidades técnicas y los conocimientos prácticos necesarios para el empleo de materiales compuestos en nuevas aplicaciones. Los textos son –en la medida de lo posible– autocontenidos en sus partes, permitiendo una lectura acorde al interés particular de cada lector. En ellos se presentan fundamentos técnicos, resultados de investigaciones, y se revisan y compilan referencias bibliográficas actualizadas que complementan y permiten al lector adquirir un conocimiento más profundo de los temas expuestos, encaminándolo hacia posibles futuras líneas de investigación. Escrito por profesionales e investigadores con experiencia en este campo, este libro pretende ser un texto de referencia para los no iniciados en la temática y una herramienta de estudio e investigación para lectores de niveles más avanzados.

    Este libro presenta una panorámica del estado actual de los materiales compuestos y sus aplicaciones más relevantes en la obra civil y la edificación.

  • An integrated procedure for the structural design of a composite rotor-hydrofoil of a Water Current Turbine (WCT)

     Oller Aramayo, Sergio A.; Nallim, Liz G.; Oller Martinez, Sergio Horacio
    Applied composite materials
    Vol. 20, num. 6, p. 1273-1288
    DOI: 10.1007/s10443-013-9332-9
    Date of publication: 2013-12
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    This paper shows an integrated structural design optimization of a composite rotor-hydrofoil of a water current turbine by means the finite elements method (FEM), using a Serial/Parallel mixing theory (Rastellini et al. Comput. Struct. 86:879–896, 2008, Martinez et al., 2007, Martinez and Oller Arch. Comput. Methods. 16(4):357–397, 2009, Martinez et al. Compos. Part B Eng. 42(2011):134–144, 2010) coupled with a fluid-dynamic formulation and multi-objective optimization algorithm (Gen and Cheng 1997, Lee et al. Compos. Struct. 99:181–192, 2013, Lee et al. Compos. Struct. 94(3):1087–1096, 2012). The composite hydrofoil of the turbine rotor has been design using a reinforced laminate composites, taking into account the optimization of the carbon fiber orientation to obtain the maximum strength and lower rotational-inertia. Also, these results have been compared with a steel hydrofoil remarking the different performance on both structures. The mechanical and geometrical parameters involved in the design of this fiber-reinforced composite material are the fiber orientation, number of layers, stacking sequence and laminate thickness. Water pressure in the rotor of the turbine is obtained from a coupled fluid-dynamic simulation (CFD), whose detail can be found in the reference Oller et al. (2012). The main purpose of this paper is to achieve a very low inertia rotor minimizing the start-stop effect, because it is applied in axial water flow turbine currently in design by the authors, in which is important to take the maximum advantage of the kinetic energy. The FEM simulation codes are engineered by CIMNE (International Center for Numerical Method in Engineering, Barcelona, Spain), COMPack for the solids problem application, KRATOS for fluid dynamic application and RMOP for the structural optimization. To validate the procedure here presented, many turbine rotors made of composite materials are analyzed and three of them are compared with the steel one.

  • Modelización numérica del comportamiento constitutivo del daño local y global y su correlación con la evolución de las frecuencias naturales en estructuras de hormigón reforzado  Open access

     Paredes Lopez, Jairo Andrés
    Universitat Politècnica de Catalunya
    Theses

    Read the abstract Read the abstract Access to the full text Access to the full text Open in new window  Share Reference managers Reference managers Open in new window

    Esta tesis surge de la necesidad de establecer un método racional y práctico para identificar, a través del cambio de las frecuencias naturales , el daño en estructuras de hormigón armado. Por lo que se desarrolla un nuevo modelo constitutivo de daño diferenciado con dos variables internas de daño utilizando una única superficie de discontinuidad para tracción, compresión y cortante; asimismo, se plantea un procedimiento numérico para el cálculo de las frecuencias naturales con sus formas modales de vibración para diferentes estados de daño de estructuras de hormigón armado; se presenta una metodología para correlacionar daño global y frecuencias naturales . Esta tesis se desarrollará en el marco del análisis de estructuras y la mecánica computacional, particularmente, del análisis de materiales compuestos utilizando la teoría de mezclas serie/paralelo. Los resultados numéricos obtenidos se han comparado con resultados experimentales y numéricos obtenidos de la literatura, se ha observado buenos ajustes de los resultados.

    Esta tesis surge de la necesidad de establecer un método racional y práctico para identificar, a través del cambio de las frecuencias naturales , el daño en estructuras de hormigón armado. Por lo que se desarrolla un nuevo modelo constitutivo de daño diferenciado con dos variables internas de daño utilizando una única superficie de discontinuidad para tracción, compresión y cortante; asimismo, se plantea un procedimiento numérico para el cálculo de las frecuencias naturales con sus formas modales de vibración para diferentes estados de daño de estructuras de hormigón armado; se presenta una metodología para correlacionar daño global y frecuencias naturales . Esta tesis se desarrollará en el marco del análisis de estructuras y la mecánica computacional, particularmente, del análisis de materiales compuestos utilizando la teoría de mezclas serie/paralelo. Los resultados numéricos obtenidos se han comparado con resultados experimentales y numéricos obtenidos de la literatura, se ha observado buenos ajustes de los resultados

    This thesis emerges from the need to establish a rational and smart method to estimate the global damage through changes on eigenfrequency of concrete structures. Therefore, a new constitutive damage model is developed with two scalar inner variables and using only one surface of discontinuity to traction, compression and shear. Additionally, a numerical process has been proposed to calculate eigenfrequencies and eigenvectors of concrete structure with different levels of damage. A methodology to correlation ship between global damage and changes on e1genfrequencies has been proposed. This thesis is based on structural analysis and computational mechanics and, particularly, on analysis of composite materials using serial/parallel mix theory. The numerical results obtained in this thesis is have been compared with experimental and numerical results obtained of literature, and can be seen a good fit.

  • Access to the full text
    Impact damage prediction in carbon fiber-reinforced laminated composite using the matrix-reinforced mixing theory  Open access

     Pérez Martínez, Marco Antonio; Martinez Garcia, Xavier; Oller Martinez, Sergio Horacio; Gil Espert, Lluis; Rastellini Canela, Fernando Gabriel; Flores, Fernando
    Composite structures
    Vol. 104, p. 239-248
    DOI: 10.1016/j.compstruct.2013.04.021
    Date of publication: 2013-10-01
    Journal article

    Read the abstract Read the abstract Access to the full text Access to the full text Open in new window  Share Reference managers Reference managers Open in new window

    The impact damage tolerance of fiber-reinforced laminated composite materials is a source of concern, mainly due to internal induced damage which causes large reductions on the strength and stability of the structure. This paper presents a procedure based on a finite element formulation that can be used to perform numerical predictions of the impact induced internal damage in composite laminates. The procedure is based on simulating the composite performance using a micro-mechanical approach named matrix-reinforced mixing theory, a simplified version of the serial/parallel mixing theory that does not require neither the iterative procedure nor the calculation of the tangent stiffness tensor. The numerical formulation uses continuum mechanics to simulate the phenomenon of initiation and propagation of interlaminar damage with no need to formulate interface elements, resulting in a computationally less demanding formulation. To demonstrate the capability of numerical procedure when applied to a low-velocity impact problem, numerical results are compared with the experimental ones obtained in a test campaign performed on 44 laminates specimens subjected to an out-of-plane and concentrated impact event, according to ASTM test method. Results are in good agreement with experimental data in terms of delamination onset and the internal spatial distribution of induced damage.

  • A numerical model of delamination in composite laminated beams using the LRZ beam element based on the refined zigzag theory

     Eijo, Ariel; Oñate Ibáñez de Navarra, Eugenio; Oller Martinez, Sergio Horacio
    Composite structures
    Vol. 104, p. 270-280
    DOI: 10.1016/j.compstruct.2013.04.035
    Date of publication: 2013-10
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    A method based on the Refined Zigzag Theory (RZT) to model delamination in composite laminated beam structures is presented. The novelty of this method is the use of one-dimensional finite elements to discretize the geometry of the beam. The key property of this beam element, named LRZ [1], is the possibility to capture the relative displacement between consecutive layers which occurs during delamination. The fracture mode that the LRZ element is capable to predict is mode II. In order to capture the relative displacement using the LRZ element it is necessary to adapt the RZT theory as presented in this paper. The mechanical properties of the layers are modeled using a continuum isotropic damage model [2]. The modified Newton-Raphson method is used for solving the non-linear problem.The RZT theory, the LRZ finite element and the isotropic damage model are described in the paper. Also, the implicit integrations algorithm is presented. The performance of the LRZ element is analyzed by studying the delamination in a beam for two different laminates, using the plane stress solution as a reference.

    A method based on the Refined Zigzag Theory (RZT) to model delamination in composite laminated beam structures is presented. The novelty of this method is the use of one-dimensional finite elements to discretize the geometry of the beam. The key property of this beam element, named LRZ [1], is the possibility to capture the relative displacement between consecutive layers which occurs during delamination. The fracture mode that the LRZ element is capable to predict is mode II. In order to capture the relative displacement using the LRZ element it is necessary to adapt the RZT theory as presented in this paper. The mechanical properties of the layers are modeled using a continuum isotropic damage model [2]. The modified Newton–Raphson method is used for solving the non-linear problem. The RZT theory, the LRZ finite element and the isotropic damage model are described in the paper. Also, the implicit integrations algorithm is presented. The performance of the LRZ element is analyzed by studying the delamination in a beam for two different laminates, using the plane stress solution as a reference.

  • Access to the full text
    Analysis of ultra low cycle fatigue problems with the Barcelona plastic damage model  Open access

     Martinez Garcia, Xavier; Oller Martinez, Sergio Horacio; Barbu, Lucia Gratiela; Barbat Barbat, Horia Alejandro
    International Conference on Computational Plasticity Fundamentals and Applications
    p. 352-363
    Presentation's date: 2013-09-05
    Presentation of work at congresses

    Read the abstract Read the abstract Access to the full text Access to the full text Open in new window  Share Reference managers Reference managers Open in new window

    This paper presents a plastic formulation based on the Barcelona plastic damage model capable of predicting the material failure due to Ultra Low Cycle Fatigue. This is achieved taking into account the fracture energy dissipated during the cyclic process. This approach allows the simulation of ULCF in regular cyclic tests, but also in non-regular cases such as seismic loads.

  • Access to the full text
    Stepwise advancing strategy for the simulation of fatigue problems  Open access

     Barbu, Lucia Gratiela; Oller Martinez, Sergio Horacio; Martinez Garcia, Xavier; Barbat Barbat, Horia Alejandro
    International Conference on Computational Plasticity Fundamentals and Applications
    p. 1153-1164
    Presentation's date: 2013-09-04
    Presentation of work at congresses

    Read the abstract Read the abstract Access to the full text Access to the full text Open in new window  Share Reference managers Reference managers Open in new window

    A time advance strategy for cyclic loading will be presented, applied to the fatigue formulation first proposed by [1].The coupling of both formulationsprovides a comprehensive approachto simulate high cycle fatigue problems accurately and with an important computational cost reduction. The capabilities of the proposed procedure are shown in a numerical example

    A time advance strategy for cyclic loading will be presented, applied to the fatigue formulation first proposed by [1].The coupling of both formulations provides a comprehensive approachto simulate high cycle fatigue problems accurately and with an important computational cost reduction. The capabilities of the proposed procedure are shown in a numerical example

  • Diseño óptimo multi-objetivo y ecológico de materiales con estructuras compuestas con nanotubos de carbono

     Morillo Guzman, Carlos; Lee, Dong Seop; Bugeda Castelltort, Gabriel; Oller Martinez, Sergio Horacio; Oñate Ibáñez de Navarra, Eugenio
    Congreso de Métodos Numéricos en Ingeniería
    p. 1695
    Presentation's date: 2013-06-26
    Presentation of work at congresses

     Share Reference managers Reference managers Open in new window

  • Multi-objective green design optimization of carbon nanotube composite structures

     Morillo Guzman, Carlos; Lee, Dong Seop; Bugeda Castelltort, Gabriel; Oller Martinez, Sergio Horacio; Oñate Ibáñez de Navarra, Eugenio
    International Conference on Computational Methods for Coupled Problems in Science and Engineering
    p. 1
    Presentation's date: 2013-06-19
    Presentation of work at congresses

     Share Reference managers Reference managers Open in new window

  • Computational Model of the Human Urinary Bladder  Open access

     Silva Araujo monteiro, Virginia
    Department of Strength of Materials and Structural Engineering, Universitat Politècnica de Catalunya
    Theses

    Read the abstract Read the abstract Access to the full text Access to the full text Open in new window  Share Reference managers Reference managers Open in new window

    La propuesta de una vejiga artificial es un obstáculo a trasponer. El cáncer de vejiga está entrelos casos más frecuentes de enfermedades oncológicas en Estados Unidos y Europa. Ese cánceres considerado un problema médico importante una vez que esa enfermedad presenta altastasas de re-ocurrencia, muchas veces llevando a la remoción del órgano.La solución más sofisticada para remplazar ese órgano es la vejiga ileal, que consiste en una neovejigahecha de tejido intestinal del enfermo. Desafortunadamente, esa solución presenta no soloproblemas mecánicos funcionales, descritos en la literatura como problemas de vaciado y fuga,peo también problemas de orden biológica (como ejemplo pérdida ósea, debido a la absorciónpor el intestino de substancias que necesitan ser eliminadas del organismo).A través de la solicitación de la comunidad urológica del Hospital Clínico de Barcelona y con suexperiencia en modelos numéricos para estructuras biomédicas, el Centro de MétodosNuméricos en Ingeniería (CIMNE) ha tenido la iniciativa de proporcionar actividadinvestigadora de la mecánica de la vejiga urinaria y de la simulación de interacción fluidoestructurapara reproducir el llenado y vaciado de ese órgano con la orina.La simulación de la vejiga humana por el Método de los Elementos Finitos (FEM) y un completoentendimiento de la mecánica de ese órgano y de su interacción con la orina dará la posibilidadde proponer mejora en la geometría y de analizar materiales para la solución artificial en caso deremplazamiento de la vejiga.Para lograr ese objetivo, primeramente procedemos a una revisión bibliográfica de los modelosmatemáticos del aparato urinario y un estudio comprehensivo de la fisiología y dinámica de lavejiga. Presentamos una revisión de las principales estructuras urológicas, riñón, uréter y uretra.Las estructuras anexas también son consideradas para entender las condiciones de contorno delproblema estudiado.Posteriormente, proponemos el modelo constitutivo para estudiar la vejiga urinaria humana. Elcomportamiento del musculo detrusor durante llenado y vaciado de la vejiga con orina, suhabilidad de retención de orina a baja presión debe ser correctamente representada por mediode la implementación de un modelo constitutivo no-lineal. El modelo matemático necesitarepresentar las variables mecánicas que gobiernan ese órgano, y también las propiedades de laorina. El comportamiento no-lineal de tejidos vivos es implementado y validado con ejemplos dela literatura. La propiedad quasi-incompressible de la orina y las ecuaciones Navier-Stokes sonconsideradas para análisis del fluido.Para representar la geometría de la vejiga, implementamos un modelo computacional 3D apartir de imágenes de tomografía computadorizada de un cadáver adulto. Los datos son tratadospara considerar las condiciones de contorno. Hemos construido dos modelos de malla: ummallado com tetrahedos de quatro nodos y outro mallado com elementos de membrana de tresnodos.El esquema utilizado para calcular la interacción fluido-estructura debe ser adecuado paramateriales de densidad muy parecidas. La análisis numérica de llenado y vaciado de la vejigahumana es validada con testes urodinámicos estandarizados.La parte final de la tesis, presentamos una simulación de una neo-vejiga, siendo el primer pasopara representar numéricamente materiales artificiales para remplazamiento de la vejiga

    La propuesta de una vejiga artificial es un obstáculo a trasponer. El cáncer de vejiga está entre los casos más frecuentes de enfermedades oncológicas en Estados Unidos y Europa. Ese cáncer es considerado un problema médico importante una vez que esa enfermedad presenta altas tasas de re-ocurrencia, muchas veces llevando a la remoción del órgano. La solución más sofisticada para remplazar ese órgano es la vejiga ileal, que consiste en una neovejiga hecha de tejido intestinal del enfermo. Desafortunadamente, esa solución presenta no solo problemas mecánicos funcionales, descritos en la literatura como problemas de vaciado y fuga, peo también problemas de orden biológica (como ejemplo pérdida ósea, debido a la absorción por el intestino de substancias que necesitan ser eliminadas del organismo). A través de la solicitación de la comunidad urológica del Hospital Clínico de Barcelona y con su experiencia en modelos numéricos para estructuras biomédicas, el Centro de Métodos Numéricos en Ingeniería (CIMNE) ha tenido la iniciativa de proporcionar actividad investigadora de la mecánica de la vejiga urinaria y de la simulación de interacción fluidoestructura para reproducir el llenado y vaciado de ese órgano con la orina. La simulación de la vejiga humana por el Método de los Elementos Finitos (FEM) y un completo entendimiento de la mecánica de ese órgano y de su interacción con la orina dará la posibilidad de proponer mejora en la geometría y de analizar materiales para la solución artificial en caso de remplazamiento de la vejiga. Para lograr ese objetivo, primeramente procedemos a una revisión bibliográfica de los modelos matemáticos del aparato urinario y un estudio comprehensivo de la fisiología y dinámica de la vejiga. Presentamos una revisión de las principales estructuras urológicas, riñón, uréter y uretra. Las estructuras anexas también son consideradas para entender las condiciones de contorno del problema estudiado. Posteriormente, proponemos el modelo constitutivo para estudiar la vejiga urinaria humana. El comportamiento del musculo detrusor durante llenado y vaciado de la vejiga con orina, su habilidad de retención de orina a baja presión debe ser correctamente representada por medio de la implementación de un modelo constitutivo no-lineal. El modelo matemático necesita representar las variables mecánicas que gobiernan ese órgano, y también las propiedades de la orina. El comportamiento no-lineal de tejidos vivos es implementado y validado con ejemplos de la literatura. La propiedad quasi-incompressible de la orina y las ecuaciones Navier-Stokes son consideradas para análisis del fluido. Para representar la geometría de la vejiga, implementamos un modelo computacional 3D a partir de imágenes de tomografía computadorizada de un cadáver adulto. Los datos son tratados para considerar las condiciones de contorno. Hemos construido dos modelos de malla: un mallado con tetrahedos de cuatro nodos y otro mallado con elementos de membrana de tres nodos. El esquema utilizado para calcular la interacción fluido-estructura debe ser adecuado para materiales de densidad muy parecidas. El análisis numérico de llenado y vaciado de la vejiga humana es validada con tests urodinámicos estandarizados. La parte final de la tesis, presentamos una simulación de una neo-vejiga, siendo el primer paso para representar numéricamente materiales artificiales para remplazamiento de la vejiga.

    The proposal of an artificial bladder is still a challenge to overcome. Bladder cancer is among the most frequent cases of oncologic diseases in United States and Europe. It is considered a major medical problem once this disease has high rates of reoccurrence, often leading to the extirpation of this organ. The most refined solution to replace this organ is the ileal bladder, which consists of a neobladder made of the patient’s intestinal tissue. Unfortunately this solution presents not only functional mechanical problems, described on the literature as voiding and leaking problems, but also biological ones (i.e. bone loss, given the absorption by the intestine of substances that should be eliminated from the organism). Urged by the urological community of the Hospital Clinic de Barcelona and backgrounded by its experience in the numerical simulation of biomedical structures, the Center of Numerical Methods in Engineering (CIMNE) had the initiative to provide the research of the mechanics of the urinary bladder and the simulation of fluid structure interaction (FSI) to account for the filling and voiding of this organ with urine. The Finite Element Method (FEM) simulation of the real bladder and the comprehensive understanding of the mechanics of this organ and its interaction with urine will give the possibility to propose geometrical improvements and study suitable materials for an artificial solution to address the cases on which the bladder needs to be removed. To reach this goal, first we proceeded to the bibliographic review of mathematical models of the urinary apparatus and to a comprehensive study of the physiology and dynamics of the bladder. A review of the major urological structures, kidney, ureter and urethra, takes place. To consider boundary conditions other surrounding structures to the urinary system are also studied. In the second part of the thesis, we propose the numerical model to study the human urinary bladder. The behavior of the detrusor muscle during filling and voiding of the bladder with urine and its ability to promote the storage of urine under low pressure need to be accurately represented, requiring the implementation of a non-linear constitutive model. The mathematical model needs to be capable to simulate the mechanical variables that govern this organ and the properties of the urine. The nonlinear behavior of living tissues is implemented and validated with examples from the literature. The quasi-incompressibility property of urine and the navierstokes equations for the fluid are taken into account. The geometry of the bladder needs to be taken into account, and the implementation of a 3D computational model obtained from the computerized tomography of a cadaver male adult is considered. The data has been treated to consider boundary conditions. Two models have been conceived: one meshed with four nodes tetrahedral and another meshed with shell elements. FSI must work for the simulation of filling and voiding of the bladder. Due to the close densities of the materials the scheme used to solve fluid-structure needs to be carefully selected. The proposed numerical model and the filling and voiding analysis are finally validated with standardized urodynamic tests. The final part of the thesis, the simulation of a neobladder is presented, being the first step to simulate numerically artificial materials for bladder replacement.

  • A four-noded quadrilateral element for composite laminated plates/shells using the refined zigzag theory

     Eijo, Ariel; Oñate Ibáñez de Navarra, Eugenio; Oller Martinez, Sergio Horacio
    International journal for numerical methods in engineering
    Vol. 95, num. 8, p. 631-660
    DOI: 10.1002/nme.4503
    Date of publication: 2013-05-20
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    A new bilinear four-noded quadrilateral element (called quadrilateral linear refined zigzag) for the analysis of composite laminated and sandwich plates/shells based on the refined zigzag theory is presented. The element has seven kinematic variables per node. Shear locking is avoided by introducing an assumed linear shear strain field. The performance of the element is studied in several examples where the reference solution is the 3D finite element analysis using 20-noded hexahedral elements.

    A new bilinear four-noded quadrilateral element (called quadrilateral linear refined zigzag) for the analysis of composite laminated and sandwich plates/shells based on the refined zigzag theory is presented. The element has seven kinematic variables per node. Shear locking is avoided by introducing an assumed linear shear strain field. The performance of the element is studied in several examples where the reference solution is the 3D finite element analysis using 20-noded hexahedral elements.

  • Robust design optimisation of advance hybrid (fiber–metal) composite structures

     Lee, Dong Seop; Morillo Carbonell, Carlos; Oller Martinez, Sergio Horacio; Bugeda Castelltort, Gabriel; Oñate Ibáñez de Navarra, Eugenio
    Composite structures
    Vol. 99, p. 181-192
    DOI: 10.1016/j.compstruct.2012.11.033
    Date of publication: 2013-05
    Journal article

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • MODELO ANALÍTICO NUMÉRICO PARA EL ESTUDIO Y OPTIMIZACIÓN DE PLACAS GRUESAS LAMINADAS

     Rango, Rita-Fernanda
    Universidad Nacional de Salta (UNSa)- Argentina.
    Theses

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Analytical and numerical analysis of human dental occlusal contact

     Bastos de Souza, FLAVIA; Casas, Estevam; Oller Martinez, Sergio Horacio
    Computer methods in biomechanics and biomedical engineering
    Vol. 16, num. 5, p. 495-503
    DOI: 10.1080/10255842.2011.627328
    Date of publication: 2013
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    The knowledge of contact forces in teeth surfaces during mastication or para-functional movements can help to understand processes related to friction and wear of human dental enamel. The development of a numerical model for analysis of the occlusal contact between two antagonistic teeth is proposed, which includes three basic steps: the characterisation of the surface roughness, its homogenisation using an assumed distribution function and the numerical determination of the resulting forces. Finite element strain results for the main different asperities are statistically combined, deriving the predicted macroscopic behaviour of the interface. Axisymmetric and 3D numerical models with an elasto-plastic constitutive law are used to simulate micro-indentations and micro-contacts, respectively. The contact is allowed to occur locally in planes not necessarily parallel to the surface's mean plane, a problem for which there is no analytical solution. The three identified parameters, homogenised surface hardness (3.68 GPa), surface yield stress (3.08 GPa) and static friction coefficient (0.23), agree with the experimental values reported in the literature.

  • Computational model of the human urinary blader

     Monteiro, Virginia; Oñate Ibáñez de Navarra, Eugenio; Oller Martinez, Sergio Horacio
    Date of publication: 2013
    Book

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    The proposal of an artificial bladder is still a challenge to overcome. Bladder cancer is among the most frequent cases of oncologic diseases in United States and Europe. It is considered a major medical problem once this disease has high rates of reoccurrence, often leading to the extirpation of this organ. The most refined solution to replace this organ is the ileal bladder, which consists of a neobladder made of the patient’s intestinal tissue. Unfortunately this solution presents not only functional mechanical problems, described on the literature as voiding and leaking problems, but also biological ones (i.e. bone loss, given the absorption by the intestine of substances that should be eliminated from the organism). Urged by the urological community of the Hospital Clinic de Barcelona and backgrounded by its experience in the numerical simulation of biomedical structures, the Center of Numerical Methods in Engineering (CIMNE) had the initiative to provide the research of the mechanics of the urinary bladder and the simulation of fluid structure interaction (FSI) to account for the filling and voiding of this organ with urine. The Finite Element Method (FEM) simulation of the real bladder and the comprehensive understanding of the mechanics of this organ and its interaction with urine will give the possibility to propose geometrical improvements and study suitable materials for an artificial solution to address the cases on which the bladder needs to be removed. To reach this goal, first we proceeded to the bibliographic review of mathematical models of the urinary apparatus and to a comprehensive study of the physiology and dynamics of the bladder. A review of the major urological structures, kidney, ureter and urethra, takes place. To consider boundary conditions other surrounding structures to the urinary system are also studied. In the second part of the thesis, we propose the numerical model to study the human urinary bladder. The behavior of the detrusor muscle during filling and voiding of the bladder with urine and its ability to promote the storage of urine under low pressure need to be accurately represented, requiring the implementation of a non-linear constitutive model. The mathematical model needs to be capable to simulate the mechanical variables that govern this organ and the properties of the urine. The nonlinear behavior of living tissues is implemented and validated with examples from the literature. The quasi-incompressibility property of urine and the navierstokes equations for the fluid are taken into account. The geometry of the bladder needs to be taken into account, and the implementation of a 3D computational model obtained from the computerized tomography of a cadaver male adult is considered. The data has been treated to consider boundary conditions. Two models have been conceived: one meshed with four nodes tetrahedral and another meshed with shell elements. FSI must work for the simulation of filling and voiding of the bladder. Due to the close densities of the materials the scheme used to solve fluid-structure needs to be carefully selected. The proposed numerical model and the filling and voiding analysis are finally validated with standardized urodynamic tests. The final part of the thesis, the simulation of a neobladder is presented, being the first step to simulate numerically artificial materials for bladder replacement.

  • Characterization of mechanical properties of biological tissue: application to the FEM analysis of the urinary bladder

     Oñate Ibáñez de Navarra, Eugenio; Bellomo, Facundo J.; Monteiro, Virginia; Oller Martinez, Sergio Horacio; Nallim, Liz G.
    Date of publication: 2013
    Book chapter

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    This text presents an approach for the mechanical behavior of soft biological tissue using the finite elements method and a general constitutive model. Specifically we analyze the mechanical behavior of a urinary bladder starting from a procedure for obtaining the mechanical characterization of the biological tissue. Bladder tissue is modelled as a composite material formed by soft matrix reinforced with preferentially oriented fibres. In the first part of the text we present a procedure for identifying the mechanical properties of biological tissue main constituents by an inverse method. Then this information is used for the numerical simulation of the mechanical behavior of the bladder within the FEM. The formulation can be applied to various types of biological tissues, both in the field of material characterization, and in the numerical simulation of the tissue biomechanical behavior.

  • An inverse approach for the mechanical characterisation of vascular tissues via a generalised rule of mixtures

     Bellomo, Facundo; Oller Martinez, Sergio Horacio; Nallim, Liz G.
    Computer methods in biomechanics and biomedical engineering
    Vol. 15, num. 12, p. 1257-1262
    DOI: 10.1080/10255842.2011.585976
    Date of publication: 2012-12
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    Mechanical factors such as stresses and strains play a major role in the growth and remodelling of soft biological tissues. The main constituents of tissue undergo different processes reacting to mechanical stimulus. Thereby, the characterisation of growth and remodelling requires an accurate estimation of the stresses and strains of their main components. Many soft tissues can be considered as composite materials and can be analysed using an appropriate rule of mixtures. Particularly, arterial tissue can be modelled as an isotropic soft matrix reinforced with preferentially oriented collagen fibres. An inverse approach to obtain the mechanical characterisation of each main component is proposed in this work. The procedure is based on a rule of mixtures raised in a finite deformation framework and generalised to include kinematics and compatibility equations for serial–parallel behaviour. This methodology allows obtaining the stress–strain relationship of the components fitting experimental data.

  • Modelo de degradación diferenciada para materiales compuestos

     Quinteros, Ricardo D.; Oller Martinez, Sergio Horacio; Nallim, Liz G.
    Congreso Argentino de Mecánica Computacional
    p. 1591-1606
    Presentation's date: 2012-11-16
    Presentation of work at congresses

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    En este trabajo se presenta la formulación y validación de un modelo de degradación elástica diferenciado. El modelo propuesto permite degradar en forma diferenciada la parte volumétrica y desviadora del comportamiento constitutivo del material y está basado en una generalización del modelo de degradación simple de Kachanov. De esta manera, el modelo resulta especialmente apropiado para simular el comportamiento de materiales friccionales. En particular, este modelo se aplica a los materiales componentes de una mampostería de ladrillos homogeneizada mediante una técnica particular ad hoc¸ que permite su tratamiento como material compuesto anisótropo, partiendo de las características geométricas y mecánicas de los materiales constituyentes. Para el tratamiento de la anisotropía, se usa la técnica de mapeo de espacios a través del concepto de espacio isótropo ficticio. La metodología planteada brinda una gran potencia de simulación pudiéndose también utilizar, si fuera necesario, otras formulaciones constitutivas diferentes para el comportamiento de los materiales componentes de la mampostería. El modelo constitutivo propuesto, junto con la técnica de homogeneización se implementa en un programa general de elementos finitos. Finalmente, se muestran los resultados obtenidos en ejemplos simples de validación del modelo y luego se presentan ejemplos de aplicación que muestran la respuesta no lineal del compuesto y su comparación con resultados publicados por otros autores.

  • Numerical modeling of a cervical spine discectomy

     Comellas Sanfeliu, Ester; Oller Martinez, Sergio Horacio; Poblete, José; Berenguer, Joan; Prats-Galino, Alberto
    Congreso Argentino de Mecánica Computacional
    p. 3811-3826
    Presentation's date: 2012-11-16
    Presentation of work at congresses

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    Cervical spine discectomy is a relatively common medical procedure which entails the surgical removal of a herniated intervertebral disc which is then replaced with an adequate prosthesis. Surgeons rely on their expertise to minimize the damage induced on the adjacent vertebrae and discs during this invasive procedure in order to reduce the patient's postsurgical distress. A typical cervical spine discectomy has been modelled and tested using the Finite Element Method (FEM) with the intention of contributing to better elucidate its immediate physical consequences on the vertebrae and intervertebral discs. Internal stresses, strains and damage levels can be obtained through the use of FE models, which can prove useful in improving surgical procedures or tailoring them to the need of particular patients. To this aim, a model of four cervical vertebrae with their corresponding discs has been built. Spinal ligaments, zygapophyseal joints and uncovertebral joints have also been included. The vertebrae have been modelled using a damage model whilst the intervertebral discs and ligaments have been treated as separate hyperelastic materials. Also, the nucleus and the annulus of the discs have been di erentiated. The problem has been solved following non-linear large deformation theory and considering prestress in the ligaments. The model's accuracy has been assessed through comparison of previously published results for di erent spinal movements (N. Kallemeyn et al., Med Eng Phys, 32(5):482-489 (2010)). Then, the model has been numerically tested for a load case representative of the discectomy procedure.

  • Access to the full text
    Modelling viscoelastic behaviour of carbón nanotube-reinforced thermo-plastics  Open access

     Otero Gruer, Fermin Enrique; Oller Martinez, Sergio Horacio; Martinez Garcia, Xavier; Salomon, Ramon Omar
    Congreso Argentino de Mecánica Computacional
    p. 1571-1590
    Presentation's date: 2012-11-15
    Presentation of work at congresses

    Read the abstract Read the abstract Access to the full text Access to the full text Open in new window  Share Reference managers Reference managers Open in new window

    Carbon nanotubes (CNTs), since their discovery by Lijima (S. Lijima, Nature, 354:56-58 (1991)), are considered a new generation of reinforcement. Their "nano" size structure makes them potentially free of defects, which provides them with excellent physical properties. There are two main nanotube types: single wall nanotubes (SWCNTs), which are made of a single wall tube; and multiwall nanotubes (MWCNTs), which consist in several concentric walls, one inside the other. A key factor for the reinforcement efficiency in a composite it is the interface bonding between the CNTs and the matrix. This work presents a new constitutive model to predict the mechanical performance of composites made of a thermo-plastic matrix reinforced with CNTs. The model takes into account explicitly the mechanical contribution of the interface between the matrix and the CNTs (F. Otero et. al., Comp Structures, 94:2920-2930 (2012)). The constitutive model is based in the mixing theory, which obtains the composite performance from the response of each constituent component, each one simulated with its own constitutive law. The model has been implemented into an in-house FEM code: PLCd. As an application example, this code is used to predict the mechanical properties of a straight beam with different material configurations. In this case, a viscoelastic constitutive model is proposed for the polymeric matrix. The viscous response within the elastic range of the materials is studied. This response shows a high capacity of energy dissipation in composites reinforced with MWCNTs.

  • Simulación numérica del crecimiento hipertrófico de tejidos biológicos

     Bellomo, Facundo; Oller Martinez, Sergio Horacio; Nallim, Liz G.
    Congreso Argentino de Mecánica Computacional
    p. 1465-1476
    Presentation's date: 2012-11-15
    Presentation of work at congresses

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    El crecimiento de los tejidos biológicos blandos tiene un papel fundamental en una serie de procesos normales y patológicos de gran incidencia en la salud humana. Algunos de los factores que regulan estos procesos en los tejidos biológicos son fundamentalmente mecánicos, de allí la importancia del estudio de estos fenómenos en el marco de una formulación que permita estimar los campos de tensión y deformación, así como la interrelación con los fenómenos de crecimiento. En general, los modelos de crecimiento publicados hasta la fecha consideran el estímulo mecánico para el crecimiento a partir de las tensiones instantáneas a que está sometido el tejido en un determinado instante. Estos modelos, sin embargo, no resultan adecuados para el caso del crecimiento hipertrófico de tejidos biológicos blandos. El proceso de hipertrofia consiste en un incremento en el volumen del tejido, que se genera cuando las fibras dañadas del mismo son reparadas y por lo tanto esta asociado al daño que sufren las mismas. Este proceso es el responsable del crecimiento del tejido muscular, de allí la importancia de su estudio con miras a su aplicación en el estudio de metodologías de entrenamiento de alto rendimiento y patologías relacionadas con la hipertrofia muscular, como por ejemplo la hipertrofia cardiaca. Para la modelación del tejido se propone el empleo de un modelo constitutivo basado en la teoría de mezclas generalizada considerando crecimiento isótropo. En el modelo el crecimiento es controlado por una variable interna de daño reversible que constituye el estímulo mecánico para la reparación de las fibras del tejido. La capacidad de reparación del tejido y el crecimiento hipertrófico asociado dependerán, a su vez, de la capacidad del metabolismo para llevar adelante estos procesos. Esto se tiene en cuanta en el modelo a través de una variable de disponibilidad biológica. Finalmente, se presentan ejemplos de validación que permiten demostrar que el modelo resulta adecuado para el estudio del crecimiento hipertrófico, considerando la acción simultánea de los campos biológico y mecánico.

  • Regularización de la energía de fractura utilizando un modelo de fisura distribuida de Hillerborg y daño isotrópico mediante un método sin malla de puntos finitos

     Pérez Pozo, Luis; Valdivia, Fernado; Oller Martinez, Sergio Horacio
    Congreso Argentino de Mecánica Computacional
    p. 1737-1747
    Presentation's date: 2012-11-15
    Presentation of work at congresses

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    El fenómeno de fractura en materiales heterogéneos cuasi-frágiles ha sido estudiado extensivamente con modelación numérica basada en el Método de Elementos Finitos (MEF), mostrando dependencias en la orientación y tamaño de la malla en los resultados. Es por eso que el uso de técnicas sin malla junto con modelos de fisura distribuida surgen como alternativas a estas dependencias. En este trabajo, un modelo de fisura distribuida aplicado al fenómeno de daño isotrópico mediante un método sin malla de Puntos Finitos es presentado. Se propone el uso de una longitud geométrica dada por la dirección de los esfuerzos principales en reemplazo de una longitud característica, la cual se basa en el modelo de Fisura Ficticia de Hillerborg. El criterio de fluencia de Rankine y un esquema iterativo incremental de Newton-Raphson son usados para predecir el comportamiento no-lineal en la zona fracturada del material.

  • Simulación numérica del flujo de un tramo fluvial con una turbina de paso situada en su lecho y los efectos en el comportamiento de su lámina libre

     Oller Aramayo, Sergio A.; Bateman Pinzon, Allen; Nallim, Liz G.; Oller Martinez, Sergio Horacio
    Congreso Argentino de Mecánica Computacional
    p. 519-528
    Presentation's date: 2012-11-14
    Presentation of work at congresses

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    Las turbinas de paso o WCT (Water Current Turbines) abren nuevas y mayores posibilidades, con grandes ventajas en cuanto al aprovechamiento hidroeléctrico. Éstas evitan las construcciones de costosas presas y reducen considerablemente el impacto medioambiental que producen otras soluciones de aprovechamiento energético. Pero a su vez esta solución plantea una serie de nuevos retos tecnológicos, debido a sus diseños sin todavía ningún tipo de estandarización y pocos antecedentes en su utilización. Además, a todo esto hay que agregar la complejidad que añade el estudio del comportamiento del flujo del río donde deben instalarse. El modelo que se analiza en el presente trabajo representa un tramo fluvial con una turbina de paso axial situada en su lecho. Dicho modelo se analiza mediante la técnica de simulación numérica CFD (Computational Fluid Dynamics) y la turbina de paso se representa introduciendo en el cauce del río un bloque constituido por un medio continuo poroso para representar las perturbaciones que esta introduce y sus intercambios energéticos con el flujo del cauce. En este artículo se analizan las velocidades alcanzadas en las distintas zonas del río, presiones, líneas de corriente, y el comportamiento de la lámina libre que resulte de la presencia de la turbina representada a través de un bloque de medio poroso. Con este trabajo se estudia un eslabón importante en la cadena de desarrollos necesarios para el diseño y factibilidad de aplicación y puesta en marcha de una turbina de paso que está actualmente en desarrollo por los autores. (Oller et al., Revista Iberoamericana de Ingeniería Mecánica, Vol.16 Nº1 pp. 03-16 (2012)).

  • Análisis dinámico de placas laminadas mediante macro-elementos usando teoría trigonométrica de deformación por corte

     Rango, Rita F.; Nallim, Liz G.; Oller Martinez, Sergio Horacio
    Congreso Argentino de Mecánica Computacional
    p. 1379-1398
    Presentation's date: 2012-11-14
    Presentation of work at congresses

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    En este trabajo se incorpora la cinemática correspondiente a una Teoría Trigonométrica de Deformación por Corte (TSDT) a macro-elementos enriquecidos, los cuales fueron formulados originalmente por los autores para el análisis de placas delgadas. En esta teoría se emplean funciones trigonométricas, definidas en la variable del espesor y dependientes del mismo, que incorporan una variación sinusoidal de los desplazamientos a lo largo del espesor y verifican la condición de tensiones de corte nulas en las superficies superior e inferior del laminado y la compatibilidad de desplazamientos en el plano en las superficies interlaminares. Por otro lado, se evita el bloqueo por cortante y no se requiere de un factor de corrección por corte. Las relaciones constitutivas entre tensiones y deformaciones cortantes se satisfacen en cada lámina o capa. El macro-elemento formulado constituye un elemento finito jerárquicamente enriquecido con polinomios de Gram-Schmidt que, a su vez, es mapeado utilizando el concepto de isoparametría en coordenadas naturales. Así, la superficie de una placa se discretizaría con una malla de macro-elementos que a diferencia de elementos finitos clásicos, no requieren densificar el mallado. La formulación obtenida se emplea en este trabajo para el análisis dinámico de placas gruesas laminadas, considerando diferentes condiciones de contorno. Los resultados numéricos obtenidos con la presente formulación muestran una buena correlación con resultados publicados por otros autores. Además, se pueden realizar con facilidad estudios paramétricos y llevar a cabo procesos de optimización.

  • Advanced composite material simulation

     Oller Martinez, Sergio Horacio
    Congreso Argentino de Mecánica Computacional
    p. 11
    Presentation's date: 2012-11-13
    Presentation of work at congresses

     Share Reference managers Reference managers Open in new window

  • The Quadrants Method: a procedure to evaluate the seismic performance of existing buildings

     Vielma Pérez, Juan Carlos; Martínez, Y; Barbat Barbat, Horia Alejandro; Oller Martinez, Sergio Horacio
    World Conference on Earthquake Engineering
    p. 1-9
    Presentation's date: 2012-09-25
    Presentation of work at congresses

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    In this work a new simple procedure for the evaluation of the seismic performance is formulated. It combines the results of non-linear static analysis with a specific Limit State defined by inter-storey drift-based damage threshold and the seismic demand obtained from the inelastic design spectrum. With both values it is possible to define four zones in the capacity curve which characterizes four different seismic performances. The procedure is used to evaluate two reinforced concrete framed buildings, the first one consist in a typical lowrise building designed according to current Venezuelan codes; the second one is a four-storey building designed according to older code, whose had been damaged by fire. Results shown both cases do not meet the Quadrants Method criterion then they need to be redesigned. Redesigned buildings were submitted to a non-linear dynamic analysis, representative of three hazard levels associated with three Limit States. These redesigned buildings met all the objectives associated with the hazard levels, showing the efficiency of the method for the rapid evaluation of the seismic performance of existing buildings.

  • Study and prediction of the mechanical performance of a nanotube-reinforced composite

     Otero Gruer, Fermin Enrique; Martinez Garcia, Xavier; Oller Martinez, Sergio Horacio; Salomon, Ramon Omar
    Composite structures
    Vol. 94, num. 9, p. 2920-2930
    DOI: 10.1016/j.compstruct.2012.04.001
    Date of publication: 2012-09
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    Carbon nanotubes (CNTs) have been regarded as ideal reinforcements for high-performance composites. A key factor for the reinforcement efficiency is the interface bonding between the CNTs and the matrix. This paper presents a new constitutive model to predict the mechanical performance of composites made with CNTs. The model takes into account explicitly the performance of the interface between the matrix and the CNTs. The formulation developed is based in the mixing theory. It divides the composite in matrix and in a new material result of coupling the CNTs with the interface. The relation defined between interface and CNTs assumes that the load is transferred to the nanotubes along their ends and that in the central part the CNTs can develop their full strength. The composite non-linear behavior results from the non-linearities of its constituents. In case of interface damage, it also becomes non-linear the law defined to couple the interface with the CNTs. After describing the formulation, it is validated studying the elastic response of several composites made with different types of CNTs reinforcements. The non-linear behavior provided by the formulation is also studied. In both cases the numerical results are compared with experimental data showing good agreement.

  • A comparative mechanical analysis of the effect caused by artificial and real induced interlaminar damage in composite laminates

     Pérez Martínez, Marco Antonio; Gil Espert, Lluis; Oller Martinez, Sergio Horacio
    International Conference on Experimental Mechanics
    p. 403-404
    Presentation's date: 2012-07-24
    Presentation of work at congresses

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • A tool for the identification of low R.C. structures damage levels

     Paredes, Jairo Andrés; Baños, J.; Oller Martinez, Sergio Horacio; Barbat Barbat, Horia Alejandro; Martinez Garcia, Xavier
    World Congress on Computational Mechanics
    Presentation's date: 2012-07-09
    Presentation of work at congresses

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Non-destructive evaluation of low velocity impact damage in composite laminates using dynamic response

     Pérez Martínez, Marco Antonio; Gil Espert, Lluis; Oller Martinez, Sergio Horacio
    International Conference on Mechanics of Nano, Micro and Macro Composite Structures
    Presentation's date: 2012-06-19
    Presentation of work at congresses

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • A constitutive model for tissue adaptation: necrosis and stress driven growth

     Bellomo, Facundo; Armero, Francisco; Nallim, Liz G.; Oller Martinez, Sergio Horacio
    Mechanics research communications
    Vol. 42, num. SI, p. 51-59
    DOI: 10.1016/j.mechrescom.2011.11.007
    Date of publication: 2012-06
    Journal article

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Low environmental impact composite structure design optimisation using robust multi-objective optimisation platform

     Morillo Carbonell, Carlos; Lee, Dong Seop; Bugeda Castelltort, Gabriel; Oller Martinez, Sergio Horacio; Oñate Ibáñez de Navarra, Eugenio
    International Conference on Mechanics of Nano, Micro and Macro Composite Structures
    p. 1-2
    Presentation's date: 2012-06
    Presentation of work at congresses

    View View Open in new window  Share Reference managers Reference managers Open in new window