Issue 2

• Adaptive scheme for three-dimensional convection – diffusion problems

  L. Monforte, A. Pérez-Foguet

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  We present an adaptive scheme for three-dimensional convection-diffusion problems discretized by the Finite Element Method. The adaptive scheme is based on a remeshing strategy that applies a maximum volume constraint to the elements of a reference mesh. The remeshing can increase or decrease drastically the size of the elements in a single step automatically. With this strategy, the mesh quality does not deteriorate, as a consequence, the number of iterations required to solve the system of linear equations using iterative algorithms is kept constant. Two examples of very different characteristics are presented in order to analyze the proposal for a wide range of situations. The first is a three-dimensional extension of the Smolarkiewicz problem and the second is a simplified version of a point source pollutant transport problem. The results show the flexibility of the proposal. An optimal remeshing frequency, from a computational cost and accuracy of the results point of view, can be defined for both kinds of problems.

  Abstract
  We present an adaptive scheme for three-dimensional convection-diffusion problems discretized by the Finite Element Method. The adaptive scheme is based on a remeshing strategy [...]

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• Analysis of laminated beams using the natural neighbour radial point interpolation method

  S. Moreira, J. Belinha, L. Dinis, R. Jorge

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  In this work, a meshless method, “natural neighbour radial point interpolation method” (NNRPIM), is applied to the one‐dimensional analysis of laminated beams, considering the theory of Timoshenko. The NNRPIM combines the mathematical concept of natural neighbours with the radial point interpolation. Voronoï diagrams allows to impose the nodal connectivity and the construction of a background mesh for integration purposes, via influence cells. The construction of the NNRPIM interpolation functions is shown, and, for this, it is used the multiquadratic radial basis function. The generated interpolation functions possess infinite continuity and the delta Kronecker property, which facilitates the enforcement of boundary conditions, since these can be directly imposed, as in the finite element method (FEM). In order to obtain the displacements and the deformation fields, it is considered the Timoshenko theory for beams under transverse efforts. Several numerical examples of isotropic beams and laminated beams are presented in order to demonstrate the convergence and accuracy of the proposed application. The results obtained are compared with analytical solutions available in the literature.

  Abstract
  In this work, a meshless method, “natural neighbour radial point interpolation method” (NNRPIM), is applied to the one‐dimensional analysis of laminated beams, considering [...]

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• On the use of Cartesian grid finite element code in structural optimization

  E. Nadal, J. Ródenas, E. Sánchez-Orgaz, S. López-Real, J. Martí-Pellicer

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

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• Application of computational methods in the assessment of the aeroelastic response of cable supported bridges

  F. Nieto, J. Jurado, S. Hernández, I. Kusano

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  The possibilities of computational methods for assessing the response of cable supported bridges under wind action are considered in this work. The main objective is to study the possibilities of substituting wind tunnel campaigns by computer based analyses, particularly at the early design stage. The preliminary proposed design for a continuous cable-stayed bridge with two main spans of 650 m and a single box girder deck has been considered as a case study. The force coefficients of the deck cross-section have been computed and the unsteady response associated to vortex-shedding has been simulated using CFD commercial software. Furthermore, an in-house piece of software has been employed to obtain the response for flutter and buffeting phenomena adopting the hybrid approach, with that purpose the experimental flutter functions of a similar box girder deck were adopted. The computational results have been validated by comparison with similar experimental results published by other researchers. It has been verified that the set of adopted methods offers reliable results with moderate costs, therefore, the proposed approach is very suitable at the early design stage of long span bridges or at conceptual design works.

  Abstract
  The possibilities of computational methods for assessing the response of cable supported bridges under wind action are considered in this work. The main objective is to study [...]

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• The concept hyperbeam as generalization of 1-dimensional models in rod elastostatics

  S. Monleón, C. Lázaro

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  This paper is concerned with the general formulation of linear problems in rod elastostatics, and with the identification of their common formal and structural features, valid for every kinematical hypothesis. The generalized variables (section forces and generalized deformations) defining the 1-dimensional model are introduced in a consistent and natural way, through a convenient factorization of the density of complementary potential energy, for every kinematical constraint which can be expressed as a linear combination of the generalized displacements. The identification of this complementary energy function with the Hamiltonian functional of analytical mechanics allows a systematic procedure to construct the equations which rule this class of problems. In this frame, the main target is to establish the required conditions to write the rod equilibrium equations in a purely statical form (with no interplay of kinematical variables). We primarily conclude that this is possible when the kinematics of the cross-sections is constrained to a rigid body movement. As a consequence, the concept of hyperbeam is proposed in order to define those models with deformation modes beyond rigid body movements of the cross section: in them, section forces and generalized displacements are coupled in the equilibrium equations. This is related to the idea of local static indeterminacy (hyperstaticity ) and justifies the new name.

  Abstract
  This paper is concerned with the general formulation of linear problems in rod elastostatics, and with the identification of their common formal and structural features, valid [...]

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• Numerical-experimental study of the FRP-epoxy-concrete interface for reinforced structures under double shear

  M. Molina, J. Cruz, S. Oller, A. Barbat, L. Gil

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  The strengthening of concrete structures with laminates of carbon fibers CFRP (Carbon Fibers Reinforced Polymer) began in the 1980s. Nowdays, this technology is one of the most promising one because of the good mechanical properties of laminates and their easy hand-work. Laminates are bonded to the concrete structure by means of epoxy resins. The load-carrying capacity of the strengthening depends directly on the proper behavior of the interface laminate-concrete. While the concrete is capable of transferring stresses to the laminate, this one becomes in charge and collaborates to the strength mechanism of the structure. The safety factor of the reinforcement can be guaranteed if we can predict the behavior at the interface between both materials. In this work we present a pure shear test and a simulation three-dimensional to characterize the behavior of the interface between the laminate and the concrete.

  Abstract
  The strengthening of concrete structures with laminates of carbon fibers CFRP (Carbon Fibers Reinforced Polymer) began in the 1980s. Nowdays, this technology is one of the [...]

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• A proper generalized decomposition strategy for dynamic data driven application systems

  F. Masson, D. González, E. Cueto, F. Chinesta

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  Dynamic Data Driven Application Systems (DDDAS) appear as a new paradigm in the field of applied sciences and engineering, and in particular in simulation-based engineering sciences. By DDDAS we mean a set of techniques that allow the linkage of simulation tools with measurement devices for real-time control of systems and processes. DDDAS entails the ability to dynamically incorporate additional data into an executing application, and in reverse, the ability of an application to dynamically steer the measurement process. DDDAS needs for accurate and fast simulation tools making use if possible of off-line computations for limiting as possible the on-line computations. We could define efficient solvers by introducing all the sources of variability as extra-coordinates in order to solve off-line only once the model to obtain its most general solution to be then considered in on-line purposes. However, such models result defined in highly multidimensional spaces suffering the so-called curse of dimensionality. We proposed recently a technique, the Proper Generalized Decomposition (PGD), able to circumvent the redoubtable curse of dimensionality. The marriage of DDDAS concepts and tools and PGD off-line computations could open unimaginable possibilities in the field of dynamics data-driven application systems. In this work we explore some possibilities in the context of parameter estimation.

  Abstract
  Dynamic Data Driven Application Systems (DDDAS) appear as a new paradigm in the field of applied sciences and engineering, and in particular in simulation-based engineering [...]

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Issue 1

• Local and global approaches to Friction Stir Welding processes

  . testests, V. Nogué, T. Test1, . test

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017). Vol. 33, (1)

  
  

  Abstract

  This paper deals with the numerical simulation of Friction Stir Welding (FSW) processes. FSW techniques are used in many industrial applications and particularly in the aeronautic and aerospace industries, where the quality of the joining is of essential importance. The analysis is focused either at global level, considering the full component to be jointed, or locally, studying more in detail the heat affected zone (HAZ). The analysis at global (structural component) level is performed defining the problem in the Lagrangian setting while, at local level, an apropos kinematic framework which makes use of an efficient combination of Lagrangian (pin), Eulerian (metal sheet) and ALE (stirring zone) descriptions for the different computational sub-domains is introduced for the numerical modeling. As a result, the analysis can deal with complex (non-cylindrical) pin-shapes and the extremely large deformation of the material at the HAZ without requiring any remeshing or remapping tools. A fully coupled thermo-mechanical framework is proposed for the computational modeling of the FSW processes proposed both at local and global level. A staggered algorithm based on an isothermal fractional step method is introduced. To account for the isochoric behavior of the material when the temperature range is close to the melting point or due to the predominant deviatoric deformations induced by the visco-plastic response, a mixed finite element technology is introduced. The Variational Multi Scale (VMS) method is used to circumvent the LBB stability condition allowing the use of linear/linear P1/P1 interpolations for displacement (or velocity, ALE/Eulerian formulation) and pressure fields, respectively. The same stabilization strategy is adopted to tackle the instabilities of the temperature field, inherent characteristic of convective dominated problems (thermal analysis in ALE/Eulerian kinematic framework). At global level, the material behavior is characterized by a thermo-elasto- viscoplastic constitutive model. The analysis at local level is characterized by a rigid thermo-visco-plastic constitutive model. Different thermally coupled (non-Newtonian) fluid-like models as Norton-Hoff, Carreau or Sheppard-Wright, among others are tested. To better understand the material flow pattern in the stirring zone, a (Lagrangian based) particle tracing is carried out while post-processing FSW results. A coupling strategy between the analysis of the process zone nearby the pin-tool (local level analysis) and the simulation carried out for the entire structure to be welded (global level analysis) is implemented to accurately predict the temperature histories and, thereby, the residual stresses in FSW.

  Abstract
  This paper deals with the numerical simulation of Friction Stir Welding (FSW) processes. FSW techniques are used in many industrial applications and particularly in the aeronautic [...]

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• Numerical modelling of landslides in reservoirs via the Particle Finite Element Method (PFEM)

  F. Salazar, E. Oñate, R. Morán

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017). Vol. 33, (1)

  
  

  Abstract

  The paper presents the results of the application of the Particle Finite Element Method (PFEM) to the analysis of landslides in reservoirs. This is a complex phenomenon, because of the interaction between the landslide, the still water in the reservoir and the dam. PFEM combines a Lagrangian approach with the solution of the governing equations of the problem using the FEM. A mesh connecting the initial set of particles (nodes) is re-generated in every time step. Some validation cases are presented, in which PFEM results are compared with experimental data. More complex calculations have been made over the actual geometry of reservoirs taken from the cartographic information of the sites. In these cases the wave generation, its propagation and dam overtopping are reproduced. Finally, Lituya bay rock slide in which 90 × 106 tons of rocks fell on the bay, generating a huge wave that caused a maximum run-up of 524 m on the opposite shore, has been simulated in 3D. The results show that PFEM is a useful tool in risk assessment related with landslides in reservoirs as it gives a good approximation to the potential affections, thus allowing the appropriate design of protection measures.

  Abstract
  The paper presents the results of the application of the Particle Finite Element Method (PFEM) to the analysis of landslides in reservoirs. This is a complex phenomenon, because [...]

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• An algorithm for the design of a feedforward controller in canals

  J. Soler, M. Gómez, J. Rodellar

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017). Vol. 33, (1)

  
  

  Abstract

  When it is carried out any movement of a gate or another mechanism of control of a canal in free surface flow, an answer of the flow can take a lot of time in being noticed in the place of the canal takes place in which it was generated the necessity to increase or to reduce the irrigation demand, for example. Usually, the scheduled perturbations of the flow can be programmed for a future horizon. In this manner, the control action can also be programmed. This work, it shows a feedforward control algorithm that plans the gate trajectories when the demand at offtakes are programmed in a prediction horizon. The Hydraulic Influence Matrix (HIM) or matrix of sensibility of the hydrodynamic conditions in the canals to changes in the parameters of the gate trajectories is a tool that is shown very effective in the control of canals in open loop. The work defines the concept, it presents the form of to calculate and to compile the HIM starting from the complete equations of Saint-Venant in their characteristic form. Later on, it shows up an algorithm in that HIM is used: a feedforward controller algorithm so-called GoRoSo. Known the water demands at offtakes, the algorithm calculates the optimal gate trajectories in advance for a prediction horizon with the objective of keeping constant the water depth at gravity offtakes.

  Abstract
  When it is carried out any movement of a gate or another mechanism of control of a canal in free surface flow, an answer of the flow can take a lot of time in being noticed [...]

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• Comparasion of unidimensional and bidimensional flow models for earthen dam failures

  J. Soler, E. Bladé, M. Sánchez-Juny

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017). Vol. 33, (1)

  
  

  Abstract

  The development of more and more potent computers and the recent research in the field of hidroinformatics makes possible the free surface flow modelling in two dimensions caused by earthen dam failures. In this paper, the results obtained by uni-dimensional model (HEC-RAS) and two-dimensional model (CARPA) are compared. The use of the HEC-RAS software assumes the hypothesis of unidimensionality to be true, no infiltration and existence of a minimal initial flow. The comparison is made by analyzing the effect of these hypothesis in the downstream flow hydrographs. The used models reproduce the water discharge generated by a possible failure of dam number 1 of the 5th District of the Segarra-Garrigues Irrigation Project in the Ebro river basin in Spain.

  Abstract
  The development of more and more potent computers and the recent research in the field of hidroinformatics makes possible the free surface flow modelling in two dimensions [...]

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• Mandibular advancement devices in the treatment of obstructive sleep apnea syndrome

  E. Soudah, M. Bordone, A. Álvarez, J. Cobo, F. Carlos, B. Suarez

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017). Vol. 33, (1)

  
  

  Abstract

  Obstructive sleep apnea syndrome (OSAS) consists in the occurrence of recurrent episodes of airflow limitation during sleep, with undesirable consequences for the health. The phenomenon is well known from a medical point of view (prognosis, diagnosis and treatment), but there is not a methodology or analysis tools for the quantification of the clinical response using Mandibular Advancement Devices (MAD). This paper shows how combining image processing, fluid dynamics and engineering design criteria, imported from other fields, allow to establish a simple analysis method clinically useful to decide the more convenient positioning of the MAD based on the pressure or mechanical movement of the jaw. This methodology is applied to a patient suffering OSAS which the objective to evaluate the changes provoked in the upper-airways due to an innovative mandibular device.

  Abstract
  Obstructive sleep apnea syndrome (OSAS) consists in the occurrence of recurrent episodes of airflow limitation during sleep, with undesirable consequences for the health. [...]

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• Boundary conditions for gradient-enhanced models with smoothed displacements

  E. Tamayo-Mas, A. Rodríguez-Ferran

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017). Vol. 33, (1)

  
  

  Abstract

  Gradient-enhanced models based on regularised displacements are an alternative to standard models in order to simulate material failure. In this alternative formulation, mechanical displacements u coexist with smoothed displacements u˜, which are the solution of a diffusion-reaction equation. Analogously to regularised standard models, prescribing boundary conditions in this alternative formulation is an open problem. Nevertheless, imposing these conditions for the displacement field (rather than the internal state variable) seems to be easier to interpret. The goal of this work is to study the influence of these conditions: neither Dirichlet conditions (prescribed at the beginning) nor homogeneous Neumann conditions (reminiscence of standard gradient models) allow to obtain realistic numerical results, on the other hand, by means of non-homogeneous Neumann boundary conditions, these results are physically admissible. However, these conditions do not ensure volume conservation, which is an interesting property in some constitutive models. Hence, new conditions (combined conditions) are proposed. These satisfy the necessary properties for regularisation: (a) reproducibility of order 1 (u=u˜ if u is a linear field), (b) displacement smoothing along the boundary and (c) volume preservation. In this work various two-dimensional numerical tests are carried out in order to illustrate the influence of the different boundary conditions.

  Abstract
  Gradient-enhanced models based on regularised displacements are an alternative to standard models in order to simulate material failure. In this alternative formulation, mechanical [...]

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• Modeling flow through non linear coarse porous media by a finite difference scheme, with application to rockfill dams overtopping

  M. Toledo, R. Morán, H. Campos

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017). Vol. 33, (1)

  
  

  Abstract

  Flow through coarse porous media, as rockfill, gravel or sand of big size, exhibit a non linear relation between hydraulic gradient and seepage velocity. This behavior is observed when water flows over the crest of a rockfill dam, seeps into the downstream shoulder and moves through the rockfill voids. A finite difference scheme is used here to solve this problem through numerical modeling. It is implemented in the code MNLEE.RDS for solving dam overtopping problems. In addition, a procedure is provided to solve the coupled problem of flow over and through the rockfill dam. For that purpose, the concept of «law of flow exchange»is introduced.

  Abstract
  Flow through coarse porous media, as rockfill, gravel or sand of big size, exhibit a non linear relation between hydraulic gradient and seepage velocity. This behavior is [...]

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• Stability and dispersion of the problem of seismic wave propagation in 2-D using the generalized finite difference method

  F. Prieto, J. Muñoz, L. Corvinos, E. Casino, Á. Acevedo

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017). Vol. 33, (1)

  
  

  Abstract

  This paper shows the solution to the problem of seismic wave propagation in 2-D using generalized finite difference (GFD) explicit schemes. Regular and irregular meshes can be used with this method. As we are using an explicit method, it is necessary to obtain the stability condition by using the von Neumann analysis. We also obtained the star dispersion formulas for the phase velocities for the P and S waves, as well as the ones for the group velocities. As the control over the irregularity in the mesh is very important in the application of this method, we have defined an index of irregularity for the star (IIS) and another for the cloud (IIC), analyzing its relationship with the dispersion and time step used in the calculations.

  Abstract
  This paper shows the solution to the problem of seismic wave propagation in 2-D using generalized finite difference (GFD) explicit schemes. Regular and irregular meshes can [...]

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• Shape Optimization of 2D parametric models based on geometric weighting and evolutionary rules

  F. Villegas, S. Gutiérrez

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017). Vol. 33, (1)

  
  

  Abstract

  This paper presents a method for shape optimization of two-dimensional models subjected to simple or multiple load cases. The optimization is performed iteratively using evolutionary rules, based on the stress level. These rules determine regions on the boundary where the material is underused or overused, the objective is that the model evolves to a minimum weight model with a high and homogeneous stress level. The evolution is performed by modifying the boundary of the model slowly. Since the boundary is defined by parametric B-spline curves, generated changes result in a smooth boundary. The main proposal of the method is that boundary modifications are given by a set of displacements that, its magnitude and direction, take into account the geometrical information of the neighborhood, unlike other methods that simply generate displacement perpendicular to the boundary. Finally, the paper presents the design of a frame bike in order to show the good performance of the method.

  Abstract
  This paper presents a method for shape optimization of two-dimensional models subjected to simple or multiple load cases. The optimization is performed iteratively using evolutionary [...]

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• Elastoplastic Analysis of Framed Structures with Interaction Surfaces Obtained for Multiple Linear Regression

  P. Vieira, W. Silva

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017). Vol. 33, (1)

  
  

  Abstract

  The ultimate limit state criteria (yielding surfaces) applied to structural designs are easier in stress resultants. There are many difficulties to generating interaction surfaces with six sectional efforts obtained through to numerical or experimental models of a space-frame analysis. The approach, in the literature, to nonlinear analysis of structures with 3D beams is use of interaction surfaces with only three combined efforts in the cross-section. Therefore, a better understanding of load types, of interactions between the six efforts and of local and global stability of structure are necessary. The interaction surfaces with three efforts are presented in planes, quadrics, more complex, or a mixture of them shapes, so that techniques which use analytical formulations with combined efforts and several section shapes are more or less complex. Multiple linear regression allows to treat the resultant efforts of several analyses for obtaining a yielding surface with the combined efforts. In this paper, the formulation to obtaining of the surfaces and their applications in the analysis of elasto-plastic frame structures are presented.

  Abstract
  The ultimate limit state criteria (yielding surfaces) applied to structural designs are easier in stress resultants. There are many difficulties to generating interaction [...]

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• Numerical simulation of turbulent air flow with dispersed droplets in cooling tower eliminators

  B. Zamora, A. Kaiser

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017). Vol. 33, (1)

  
  

  Abstract

  This work presents a numerical study on the turbulent flow of air with dispersed water droplets in separators of mechanical cooling towers. The averaged Navier-Stokes equations are discretised through a finite volume method, using the Fluent and Phoenics codes, and alternatively employing the turbulence models k − ϵ, k − ω and the Reynolds stress model, with low-Re version and wall enhanced treatment refinements. The results obtained are compared with numerical and experimental results taken from the literature. The degree of accuracy obtained with each of the considered models of turbulence is stated. The influence of considering whether or not the simulation of the turbulent dispersion of droplets is analyzed, as well as the effects of other relevant parameters on the collection efficiency and the coefficient of pressure drop. Focusing on four specific eliminators (‘Belgian wave’, ‘H1-V’, ‘L-shaped’ and ‘Zig-zag’), the following ranges of parameters are outlined: 1 ≤ Ue ≤ 5 m/s for the entrance velocity, 2 ≤ Dp ≤ 50 μm for the droplet diameter, 650 ≤ Re ≤ 8.500 for Reynolds number, and 0.05 ≤ Pi ≤ 5 for the inertial parameter. Results reached alternately with Fluent and Phoenics codes are compared. The best results correspond to the simulations performed with Fluent, using the SST k − ω turbulence model, with values of the dimensionless scaled distance to wall y+ in the range 0.2 to 0.5. Finally, correlations are presented to predict the conditions for maximum collection efficiency (100 %), depending on the geometric parameter of removal efficiency of each of the separators, which is introduced in this work.

  Abstract
  This work presents a numerical study on the turbulent flow of air with dispersed water droplets in separators of mechanical cooling towers. The averaged Navier-Stokes equations [...]

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• Efficient calculation of formation energies of kink-pairs in BCC crystals

  E. Tellechea, O. Sabri, M. Ariza

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017). Vol. 33, (1)

  
  

  Abstract

  Motion of screw dislocations in BCC materials at low temperature is believed to be related to the formation of mobile kinks on the dislocation line. Therefore, the accurate prediction of kink nucleation energies is required to fully describe mobility of screw dislocations in these materials. Studies of fundamental dislocation processes at atomic length scale are numerically and computationally intensive problems. This work studies the calculation of zero-stress formation energies of kink-pair configurations for BCC crystals. Our model for stored energy associated to a dislocation line configuration is based on the theory of discrete dislocations of Ariza and Ortiz. Its value is computed efficiently using an algorithm developed on the NVIDIA Compute Unified Device Architecture (CUDA). Results confirm those obtained using atomistic potentials and first principles calculations, and those based on the continuum theory of dislocations.

  Abstract
  Motion of screw dislocations in BCC materials at low temperature is believed to be related to the formation of mobile kinks on the dislocation line. Therefore, the accurate [...]

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• MODELO DE FUERZAS INTERATÓMICAS PARA EL GRAFENO A PARTIR DEL POTENCIAL AIREBO

  M. Ariza, C. Ventura, M. Ortiz

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017). Vol. 33, (1)

  
  

  Abstract

  Dado que las propiedades eléctricas y térmicas del grafeno están influenciadas por la presencia de defectos topológicos en el material y que éstos condicionan así las futuras aplicaciones del grafeno como material base de componentes nanoelectrónicos, es necesario disponer de un modelo de comportamiento del grafeno que permita incluir dichos defectos. En este trabajo se ha obtenido un modelo de fuerzas interatómicas a partir del potencial AIREBO (Adaptive Intermolecular Reactive Empirical Bond-Order), desarrollado por Stuart et al. [1], que incluye interacciones atómicas hasta vecinos de orden cuarto. Se presentan, tanto expresiones explícitas de las derivadas del potencial, como los valores de las constantes de fuerza. Hemos verificado que el modelo de fuerzas cumple con las simetrías del cristal y las curvas de dispersión de fonones del correspondiente modelo dinámico presentan un buen acuerdo con las obtenidas por otros autores. Además, hemos verificado que las interacciones con vecinos terceros y cuartos no modifican, ni la estructura del campo de desplazamientos alrededor de los núcleos de dislcocación, ni sus correspondientes energías de formación que se predicen a partir de la teoría discreta de dislocaciones de Ariza y Ortiz [2]. Summary In view of the influence that topological defects have on the thermal and electrical properties of graphene, and given the pivotal role that such properties play in potential applications of graphene as a building block for nano-electronic components, models of graphene behavior that allow for the consideration of such defects are of the essence. In the present work, we have obtained an atomic force-constant model from the AIREBO potential (Adaptive Intermolecular Reactive Empirical Bond-Order), of Stuart et al. [1], that accounts for interatomic interactions up to fourth neighbors. We present explicit expressions of the potential derivatives as well as the force-constant values. We have verified that the force-constant model is invariant under the crystal symmetries and that the phonondispersion curves of the corresponding dynamic model are in good agreement with those obtained by other authors. In addition, we have verified that the thirdand fourth-neighbor interactions affect neither the displacement field in the vicinity of dislocation cores nor the corresponding formation energies predicted by the theory of discrete dislocations of Ariza and Ortiz [2].

  Abstract
  Dado que las propiedades eléctricas y térmicas del grafeno están influenciadas por la presencia de defectos topológicos en el material y que éstos condicionan así las [...]

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• PUMI: UN CÓDIGO EXPLÍCITO NO ESTRUCTURADO PARA RESOLVER LAS ECUACIONES DE EULER

  R. Flores, E. Ortega, E. Oñate

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017). Vol. 33, (1)

  
  

  Abstract

  El código PUMI se ha desarrollado en CIMNE para resolver rápidamente problemas de flujo compresible alrededor de geometrías complejas. En la actualidad se llevan a cabo de manera rutinaria cálculos con mallas que contienen decenas de millones de elementos. PUMI fue diseñado específicamente para tratar problemas de esta escala usando hardware modesto; por tanto la eficiencia del código ha sido uno de los objetivos fundamentales durante su diseño. Se buscó una utilización mínima de memoria, excelente comportamiento en entornos de ejecución secuencial y escalado satisfactorio hasta un número moderado de procesos (para su uso eficiente en estaciones de trabajo multiprocesador). Para facilitar en lo posible las tareas de generación de mallas se eligió una formulación no estucturada basada en elementos finitos. El presente artículo describe los fundamentos teóricos del algoritmo así como detalles de implementación que mejoran la robustez y eficiencia del código. Summary The PUMI flow solver has been developed at CIMNE in order to address the need for fast solutions of the flow field around complex geometries. Nowadays calculations involving a number of cells on the order of tens of millions are performed routinely. PUMI was created to deal with this kind of large-scale problem using modest hardware, therefore special emphasis was placed on the computational efficiency of the code. Design guidelines where minimum memory requirement, very fast single-threaded performance as well as satisfactory parallel scaling up to a moderate number of threads (as found on current entry-level SMP workstations). In order to simplify the mesh generation activities an unstructured finite element formulation was selected. This paper describes the theoretical basis of the algorithm as well as details of the implementation that increase the robustness and efficiency of the code.

  Abstract
  El código PUMI se ha desarrollado en CIMNE para resolver rápidamente problemas de flujo compresible alrededor de geometrías complejas. En la actualidad se llevan a cabo [...]

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• Switching implicit-explicit numerical technique for nonlinear unstable structures

  J. Curiel-Sosa, D. Owen

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  Simulation problems involving non-linear materials imply in numerous cases divergence of the implicit method which use return mapping algorithms for modelling of the nonlinear response. A switching implicit-explicit numerical technique in the context of Finite Element Methods is presented in this paper. Implicit/explicit mesh partitions are not considered whatsoever. Formulation for application to nonlinear hyperelastic materials and nonlinear elastic-plastic materials is provided. Furthermore, the response of the solid subjected to large deformations is presented and is embedded in the proposed technique. Numerical tests for nonlinear problems (geometric and/or material) showed the accurateness of the technique.

  Abstract
  Simulation problems involving non-linear materials imply in numerous cases divergence of the implicit method which use return mapping algorithms for modelling of the nonlinear [...]

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• A numerical model for the simulation of precipitates dissolution of hardened aluminium alloys using neural networks

  C. Saracibar, R. López, B. Ducoeur, M. Chiumenti, B. Meester

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  The motivation of this work is the modeling of the hardening precipitate and hardness evolutions of fully hardened heat treatable aluminium alloys during friction stir welding (FSW) and/or heat treatment processes. The model used is based on the kinetics of dissolution of precipitates model for hardened aluminium alloys given by Myhr and Grong (1991). This model contains a single independent variable, the time, and a single state variable, the volume fraction of hardening precipitates. A key point of this model is the identification of the effective activation energy for precipitates dissolution and the master curve defining the model, which was given by a look-up table. The goal of this work is to find an estimation of the effective activation energy and to model the dissolution rate of hardening precipitate in aluminium alloys using neural networks, avoiding the use of look-up tables. For this purpose a new and more convenient parametrization of the master curve is defined, a neural networks class is proposed, an objective functional is defined and a variational problem including independent parameters is solved. The novel methodology has been applied to different aluminium alloys, including the AA 6005A T6, AA 7449 T79 and AA 2198 T8. Experimental tests have been carried out for those aluminium alloys in order to get the HV1 hardness after isothermal heat treatments at different temperatures and for different treatment time durations. The effective activation energy for hardening precipitates dissolution and the master curve of the model have been obtained, using different network architectures, for the aluminium alloys considered in this work.

  Abstract
  The motivation of this work is the modeling of the hardening precipitate and hardness evolutions of fully hardened heat treatable aluminium alloys during friction stir welding [...]

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• Developement of a computational tool for the analysis of reinforced concrete membrane elements

  R. Souza

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  Reinforced concrete elements subjected to membrane forces, i.e., elements subjected to in-plane shear and axial stresses are very common for modeling complex structures such as aircraft hangars, nuclear power plants, offshore oil platforms and long-span bridges. While the design of reinforcement for membrane elements is well adressed the same can not be said regarding the analysis of performance of these elements. Into this context, the present paper aims at providing a numerical tool developed in the Matlab platform, taking into account the “Modified Compression Field Theory”. In order to certificate the performance of the proposed tool, extensive numerical results were compared with experimental results available in the literature. The obtained results revealed that the proposed tool is very confident for the analysis of reinforced concrete membrane elements.

  Abstract
  Reinforced concrete elements subjected to membrane forces, i.e., elements subjected to in-plane shear and axial stresses are very common for modeling complex structures such [...]

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• Numeric validation of the cyclic behaviour of interior connections in waffle-flat-plate structures

  J. Donaire-Ávila, A. Benavent-Climent

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  Several approaches are investigated to model interior reinforced concrete waffle-flat-plate-column connections. A model is proposed that provides very good results with reasonable low computational cost. The proposed model is validated with the experimental results obtained on a 3/5 scale specimen, subjected to quasi-static in cyclic loads up to collapse. To this end, the non-linear advanced theory of reinforced concrete is applied on a three-dimensional finite element model and non-linear analysis are conducted. Both fiber and layer elements are used for the one-dimensional and bi-dimensional components respectively. The main results of the simulation were: (i) the capacity curve obtained through out a push-over analysis with displacement control, (ii) the hysteretic curves of the slab, and (iii) the crack patterns. A very good agreement is found between numerical and experimental results.

  Abstract
  Several approaches are investigated to model interior reinforced concrete waffle-flat-plate-column connections. A model is proposed that provides very good results with reasonable [...]

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• Optimum sizing of launching nose of prestressed concrete bridges

  A. Fontán, S. Hernández, A. Baldomir, J. Díaz

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  The design of the launching nose of an incrementally launched bridge determines its constructive process and, therefore, also its dimensions. The optimization of the launching nose can raise as a first step to improve the design of a launched bridge. The conventional design process of a launching nose is based on trial and error method to reduce bending moment of prestressed concrete deck at the foremost support during launch. In this way, there is no guarantee that the obtained solution is the best among all the possible solutions since they all depend on the experience and intuition of a designer, and they are also restricted by a limited number of possible iterations. Given that launched bridges constitute an important constructive typology, all the available capacities of design innovation should be incorporated, among which it can be found numerical optimization. This research work proposes an objective and rigorous formulation to optimize a launching nose of launched bridge under real constraints that a bridge designer can encounter in practice. Comparing the results obtained by conventional process and that by optimization techniques, it can be verified that some of the assumptions, considered in classical design methods of a launching nose, are not based on any theoretical foundation. This fact demonstrates the utility of numerical optimization to improve a design.

  Abstract
  The design of the launching nose of an incrementally launched bridge determines its constructive process and, therefore, also its dimensions. The optimization of the launching [...]

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• Turing patterns formation on surfaces under deformation: A total lagrangian method approach

  C. Duque-Daza, A. Ramirez, D. Garzón-Alvarado

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  In this work we have developed several numerical examples of reaction-diffusion equations with growing domain. For this purpose we have used the Schnakenberg reaction model with parameters in space Turing. Therefore numerical tests are performed on the appearance of Turing patterns on surfaces that have high deformation rate. For the solution of reaction diffusion equations is presented a solution method on surfaces in three dimensions using the finite element method under the use of the total Lagrangian formulation. The results show that the formation of Turing patterns depends on the features of surface deformation and the rate at which change in position of each point of the domain. These results can explain some phenomena of change of pattern on the surface of the skin of animals that exhibit characteristic spots.

  Abstract
  In this work we have developed several numerical examples of reaction-diffusion equations with growing domain. For this purpose we have used the Schnakenberg reaction model [...]

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• A robust optimization hybrid algorithm for solving the direct kinematics of the general Gough-Stewart platform

  E. Hernández-Martínez, S. Valdez-Peña, E. Sánchez-Soto

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  The direct kinematics problem for parallel robots can be stated as follows: given values of the joint variables, the corresponding Cartesian variable values, the pose of the end-effector, must be found. Most of the times the direct kinematics problem involves the solution of a system of non-linear equations. The most efficient methods to solve such kind of equations assume convexity in a cost function which minimum is the solution of the non-linear system. In consequence, the capacity of such methods depends on the knowledge about an starting point which neighboring region is convex, hence the method can find the global minimum. This article propose a method based on probabilistic learning about an adequate starting point for the Dogleg method which assumes local convexity of the function. The proposed method efficiently avoids the local minima, without need of human intervention or apriori knowledge, thus it shows a more robust performance than the simple Dogleg method or other gradient based methods. To demonstrate the performance of the proposed hybrid method, numerical experiments and the respective discussion are presented. The proposal can be extended to other structures of closed-kinematics chains, to the general solution of systems of non-linear equations, and to the minimization of non-linear functions.

  Abstract
  The direct kinematics problem for parallel robots can be stated as follows: given values of the joint variables, the corresponding Cartesian variable values, the pose of the [...]

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• A probabilistic formulation of optimality criteria using the principle of maximum entropy

  S. Hernández, J. Díaz, A. Baldomir, F. Pereira

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  This work reviews A. B. Templemans research in the maximum entropy principle applied to structural optimization, which consists in defining a probabilistic approach for the optimality criteria. This new reasoning does not assume aprioristically which conditions could be active in the optimum point, giving a completely rational point of view to the optimization problem. After reviewing the state of the art, a new formulation, which simplifies and improves previous methodologies, is developed. This new method turns the optimization problem into solving successively systems of equations with the same dimension as the number of design variables. Since this algorithm requires obtaining first order sensitivities, it can be considered as a new gradient method. After the theoretical description, the algorithm is tested with two examples of truss structures. Results show a good performance of the algorithm, based on comparisons with other alternatives found in the literature.

  Abstract
  This work reviews A. B. Templemans research in the maximum entropy principle applied to structural optimization, which consists in defining a probabilistic approach for the [...]

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• Efficient implementation of a semi-recursive formulation for the dynamics of large size multibody systems

  A. Hidalgo, J. Jalón

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  This article shows an efficient implementation of a dynamic semi-recursive formulation for large and complex multibody system simulations, with interesting applications in the automotive field and especially with industrial vehicles. These systems tend to have a huge amount of kinematic constraints, becoming usual the presence of redundant but compatible systems of equations. The maths involved in the solution of these problems have a high computational cost, making very challenging to achieve real-time simulations. In this article, two implementations to increase the efficiency of these computations will be shown. The difference between them is the way they consider the Jacobian matrix of the constraint equations. The first one treats this matrix as a dense one, using the BLAS functions to solve the system of equations. The second one takes into account the sparse pattern of the Jacobian matrix, introducing the sparse function MA48 from Harwell. Both methodologies have been applied on two multibody system models with different sizes. The first model is a vehicle IVECO DAILY 35C15 with 17 degrees of freedom. The second one is a semi-trailer truck with 40 degrees of freedom. Taking as a reference the standard C/C + + implementation, the efficiency improvements that have been achieved using dense matrices (BLAS) have been of 15% and 50% respectively. The results in the first model have not improved significantly by using sparse matrices, but in the second one, the times with sparse matrices have been reduced 8% with respect to the BLAS ones.

  Abstract
  This article shows an efficient implementation of a dynamic semi-recursive formulation for large and complex multibody system simulations, with interesting applications in [...]

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• On the need for the use of error-controlled finite element analyses in structural shape optimization processes with evolutionary algorithms

  J. Ródenas, G. Bugeda, J. Albelda, E. Oñate, E. Nadal

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  This work analyzes the influence of the discretization error contained in the Finite Element (FE) analyses of each design configuration proposed by the structural shape optimization algorithms over the behavior of the algorithm. The paper clearly shows that if FE analyses are not accurate enough, the final solution provided by the optimization algorithm will neither be optimal nor satisfy the constraints. The need for the use of adaptive FE analysis techniques in shape optimum design will be shown. The paper proposes the combination of two strategies to reduce the computational cost related to the use of mesh adaptivity in evolutionary optimization algorithms: (a) the use of the algorithm described by Bugeda et al. [1] which reduces the computational cost associated to the adaptive FE analysis of each geometrical configuration and, (b) the successive increase of the required accuracy of the FE analyses in order to obtain a considerable reduction of the computational cost in the early stages of the optimization process.

  Abstract
  This work analyzes the influence of the discretization error contained in the Finite Element (FE) analyses of each design configuration proposed by the structural shape optimization [...]

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  •  read

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

  F. López-Almansa, S. Oller

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  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.

  Abstract
  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 [...]

  • 0
  •  read

• Prediction of crack propagation via local constitutive models with a scheme to track the discontinuity path

  O. Manzoli

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  Estudam-se os aspectos referentes à qualidade e objetividade das respostas obtidas com as diferentes formulações (simétrica e não-simétrica) de elementos incorporados com descontinuidade forte regularizada, assim como com a abordagem contínua (distribuída), combinando-se a lei de abrandamento dependente do tamanho do elemento com um esquema de construção progressiva da trajetória de descontinuidade. O estudo é realizado com base nos conceitos de consistência cinemática e estática das formulações de elementos com descontinuidade incorporada.

  Abstract
  Estudam-se os aspectos referentes à qualidade e objetividade das respostas obtidas com as diferentes formulações (simétrica e não-simétrica) de elementos incorporados [...]

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  •  read

• Mixed optimization of power transmission structures: An application of the simulated annealing algorithm

  S. Martínez, J. París, I. Colominas, F. Navarrina, M. Casteleiro

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  A general methodology to optimize the weight of power transmission structures is presented in this article. This methodology is based on the simulated annealing algorithm defined by Kirkpatrick in the early ‘80s. This algorithm consists of a stochastic approach that allows to explore and analyze solutions that do not improve the objective function in order to develop a better exploration of the design region and to obtain the global optimum. The proposed algorithm allows to consider the discrete behavior of the sectional variables for each element and the continuous behavior of the general geometry variables. Thus, an optimization methodology that can deal with a mixed optimization problem and includes both continuum and discrete design variables is developed. In addition, it does not require to study all the possible design combinations defined by discrete design variables. The algorithm proposed usually requires to develop a large number of simulations (structural analysis in this case) in practical applications. Thus, the authors have developed first order Taylor expansions and the first order sensitivity analysis involved in order to reduce the CPU time required. Exterior penalty functions have been also included to deal with the design constraints. Thus, the general methodology proposed allows to optimize real power transmission structures in acceptable CPU time.

  Abstract
  A general methodology to optimize the weight of power transmission structures is presented in this article. This methodology is based on the simulated annealing algorithm [...]

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• Aplicación de métodos computacionales en la evaluación de la respuesta aeroelástica de puentes soportados por cables

  F. Nieto, J. Jurado, S. Hernández, I. Kusano

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  The possibilities of computational methods for assessing the response of cable supported bridges under wind action are considered in this work. The main objective is to study the possibilities of substituting wind tunnel campaigns by computer based analyses, particularly at the early design stage. The preliminary proposed design for a continuous cable-stayed bridge with two main spans of 650 m and a single box girder deck has been considered as a case study. The force coefficients of the deck cross-section have been computed and the unsteady response associated to vortex-shedding has been simulated using CFD commercial software. Furthermore, an in-house piece of software has been employed to obtain the response for flutter and buffeting phenomena adopting the hybrid approach, with that purpose the experimental flutter functions of a similar box girder deck were adopted. The computational results have been validated by comparison with similar experimental results published by other researchers. It has been verified that the set of adopted methods offers reliable results with moderate costs, therefore, the proposed approach is very suitable at the early design stage of long span bridges or at conceptual design works.

  Abstract
  The possibilities of computational methods for assessing the response of cable supported bridges under wind action are considered in this work. The main objective is to study [...]

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• Sobre la utilización de códigos de elementos finitos basados en mallados cartesianos en optimización estructural

  E. Nadal, J. Ródenas, E. Sánchez-Orgaz, S. López-Real, J. Martí-Pellicer

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

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• Análise de vigas laminadas utilizando o natural neighbour radial point interpolation method

  S. Moreira, J. Belinha, L. Dinis, R. Jorge

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  In this work, a meshless method, “natural neighbour radial point interpolation method” (NNRPIM), is applied to the one‐dimensional analysis of laminated beams, considering the theory of Timoshenko. The NNRPIM combines the mathematical concept of natural neighbours with the radial point interpolation. Voronoï diagrams allows to impose the nodal connectivity and the construction of a background mesh for integration purposes, via influence cells. The construction of the NNRPIM interpolation functions is shown, and, for this, it is used the multiquadratic radial basis function. The generated interpolation functions possess infinite continuity and the delta Kronecker property, which facilitates the enforcement of boundary conditions, since these can be directly imposed, as in the finite element method (FEM). In order to obtain the displacements and the deformation fields, it is considered the Timoshenko theory for beams under transverse efforts. Several numerical examples of isotropic beams and laminated beams are presented in order to demonstrate the convergence and accuracy of the proposed application. The results obtained are compared with analytical solutions available in the literature.

  Abstract
  In this work, a meshless method, “natural neighbour radial point interpolation method” (NNRPIM), is applied to the one‐dimensional analysis of laminated beams, considering [...]

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• El concepto de hiperviga como generalización de los modelos unidimensionales en la estática de piezas alargadas

  S. Monleón, C. Lázaro

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  This paper is concerned with the general formulation of linear problems in rod elastostatics, and with the identification of their common formal and structural features, valid for every kinematical hypothesis. The generalized variables (section forces and generalized deformations) defining the 1-dimensional model are introduced in a consistent and natural way, through a convenient factorization of the density of complementary potential energy, for every kinematical constraint which can be expressed as a linear combination of the generalized displacements. The identification of this complementary energy function with the Hamiltonian functional of analytical mechanics allows a systematic procedure to construct the equations which rule this class of problems. In this frame, the main target is to establish the required conditions to write the rod equilibrium equations in a purely statical form (with no interplay of kinematical variables). We primarily conclude that this is possible when the kinematics of the cross-sections is constrained to a rigid body movement. As a consequence, the concept of hyperbeam is proposed in order to define those models with deformation modes beyond rigid body movements of the cross section: in them, section forces and generalized displacements are coupled in the equilibrium equations. This is related to the idea of local static indeterminacy (hyperstaticity ) and justifies the new name.

  Abstract
  This paper is concerned with the general formulation of linear problems in rod elastostatics, and with the identification of their common formal and structural features, valid [...]

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• Esquema adaptativo para problemas tridimensionales de convección-difusión

  L. Monforte, A. Pérez-Foguet

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  We present an adaptive scheme for three-dimensional convection-diffusion problems discretized by the Finite Element Method. The adaptive scheme is based on a remeshing strategy that applies a maximum volume constraint to the elements of a reference mesh. The remeshing can increase or decrease drastically the size of the elements in a single step automatically. With this strategy, the mesh quality does not deteriorate, as a consequence, the number of iterations required to solve the system of linear equations using iterative algorithms is kept constant. Two examples of very different characteristics are presented in order to analyze the proposal for a wide range of situations. The first is a three-dimensional extension of the Smolarkiewicz problem and the second is a simplified version of a point source pollutant transport problem. The results show the flexibility of the proposal. An optimal remeshing frequency, from a computational cost and accuracy of the results point of view, can be defined for both kinds of problems.

  Abstract
  We present an adaptive scheme for three-dimensional convection-diffusion problems discretized by the Finite Element Method. The adaptive scheme is based on a remeshing strategy [...]

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• Estudio numérico-experimental de la interfaz hormigón-epoxi-FRP para una estructura reforzada sometida a doble corte

  M. Molina, J. Cruz, S. Oller, A. Barbat, L. Gil

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  The strengthening of concrete structures with laminates of carbon fibers CFRP (Carbon Fibers Reinforced Polymer) began in the 1980s. Nowdays, this technology is one of the most promising one because of the good mechanical properties of laminates and their easy hand-work. Laminates are bonded to the concrete structure by means of epoxy resins. The load-carrying capacity of the strengthening depends directly on the proper behavior of the interface laminate-concrete. While the concrete is capable of transferring stresses to the laminate, this one becomes in charge and collaborates to the strength mechanism of the structure. The safety factor of the reinforcement can be guaranteed if we can predict the behavior at the interface between both materials. In this work we present a pure shear test and a simulation three-dimensional to characterize the behavior of the interface between the laminate and the concrete.

  Abstract
  The strengthening of concrete structures with laminates of carbon fibers CFRP (Carbon Fibers Reinforced Polymer) began in the 1980s. Nowdays, this technology is one of the [...]

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  •  read

• Una estrategia basada en la descomposición propia generalizada para aplicaciones gobernadas por datos dinámicos

  F. Masson, D. González, E. Cueto, F. Chinesta

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  Dynamic Data Driven Application Systems (DDDAS) appear as a new paradigm in the field of applied sciences and engineering, and in particular in simulation-based engineering sciences. By DDDAS we mean a set of techniques that allow the linkage of simulation tools with measurement devices for real-time control of systems and processes. DDDAS entails the ability to dynamically incorporate additional data into an executing application, and in reverse, the ability of an application to dynamically steer the measurement process. DDDAS needs for accurate and fast simulation tools making use if possible of off-line computations for limiting as possible the on-line computations. We could define efficient solvers by introducing all the sources of variability as extra-coordinates in order to solve off-line only once the model to obtain its most general solution to be then considered in on-line purposes. However, such models result defined in highly multidimensional spaces suffering the so-called curse of dimensionality. We proposed recently a technique, the Proper Generalized Decomposition (PGD), able to circumvent the redoubtable curse of dimensionality. The marriage of DDDAS concepts and tools and PGD off-line computations could open unimaginable possibilities in the field of dynamics data-driven application systems. In this work we explore some possibilities in the context of parameter estimation.

  Abstract
  Dynamic Data Driven Application Systems (DDDAS) appear as a new paradigm in the field of applied sciences and engineering, and in particular in simulation-based engineering [...]

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• Optimización mixta de estructuras de transporte de energía: aplicación del algoritmo de recocido simulado

  S. Martínez, J. París, I. Colominas, F. Navarrina, M. Casteleiro

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  A general methodology to optimize the weight of power transmission structures is presented in this article. This methodology is based on the simulated annealing algorithm defined by Kirkpatrick in the early ‘80s. This algorithm consists of a stochastic approach that allows to explore and analyze solutions that do not improve the objective function in order to develop a better exploration of the design region and to obtain the global optimum. The proposed algorithm allows to consider the discrete behavior of the sectional variables for each element and the continuous behavior of the general geometry variables. Thus, an optimization methodology that can deal with a mixed optimization problem and includes both continuum and discrete design variables is developed. In addition, it does not require to study all the possible design combinations defined by discrete design variables. The algorithm proposed usually requires to develop a large number of simulations (structural analysis in this case) in practical applications. Thus, the authors have developed first order Taylor expansions and the first order sensitivity analysis involved in order to reduce the CPU time required. Exterior penalty functions have been also included to deal with the design constraints. Thus, the general methodology proposed allows to optimize real power transmission structures in acceptable CPU time.

  Abstract
  A general methodology to optimize the weight of power transmission structures is presented in this article. This methodology is based on the simulated annealing algorithm [...]

  • 0
  •  read

• Predição de propagação de fissuras através de modelos constitutivos locais e técnica de construção progressiva da trajetória de descontinuidade

  O. Manzoli

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  Estudam-se os aspectos referentes à qualidade e objetividade das respostas obtidas com as diferentes formulações (simétrica e não-simétrica) de elementos incorporados com descontinuidade forte regularizada, assim como com a abordagem contínua (distribuída), combinando-se a lei de abrandamento dependente do tamanho do elemento com um esquema de construção progressiva da trajetória de descontinuidade. O estudo é realizado com base nos conceitos de consistência cinemática e estática das formulações de elementos com descontinuidade incorporada.

  Abstract
  Estudam-se os aspectos referentes à qualidade e objetividade das respostas obtidas com as diferentes formulações (simétrica e não-simétrica) de elementos incorporados [...]

  • 0
  •  read

• Resolución numérica de las ecuaciones del movimiento de edificios de varias plantas con no linealidades severas

  F. López-Almansa, S. Oller

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  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.

  Abstract
  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 [...]

  • 0
  •  read

• Sobre la necesidad de controlar el error de discretización de elementos finitos en optimización de forma estructural con algoritmos evolutivos

  J. Ródenas, G. Bugeda, J. Albelda, E. Oñate, E. Nadal

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  This work analyzes the influence of the discretization error contained in the Finite Element (FE) analyses of each design configuration proposed by the structural shape optimization algorithms over the behavior of the algorithm. The paper clearly shows that if FE analyses are not accurate enough, the final solution provided by the optimization algorithm will neither be optimal nor satisfy the constraints. The need for the use of adaptive FE analysis techniques in shape optimum design will be shown. The paper proposes the combination of two strategies to reduce the computational cost related to the use of mesh adaptivity in evolutionary optimization algorithms: (a) the use of the algorithm described by Bugeda et al. [1] which reduces the computational cost associated to the adaptive FE analysis of each geometrical configuration and, (b) the successive increase of the required accuracy of the FE analyses in order to obtain a considerable reduction of the computational cost in the early stages of the optimization process.

  Abstract
  This work analyzes the influence of the discretization error contained in the Finite Element (FE) analyses of each design configuration proposed by the structural shape optimization [...]

  • 0
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• Implementación eficiente de una formulación semirrecursiva para la dinámica de sistemas multicuerpo de gran tamaño

  A. Hidalgo, J. Jalón

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  This article shows an efficient implementation of a dynamic semi-recursive formulation for large and complex multibody system simulations, with interesting applications in the automotive field and especially with industrial vehicles. These systems tend to have a huge amount of kinematic constraints, becoming usual the presence of redundant but compatible systems of equations. The maths involved in the solution of these problems have a high computational cost, making very challenging to achieve real-time simulations. In this article, two implementations to increase the efficiency of these computations will be shown. The difference between them is the way they consider the Jacobian matrix of the constraint equations. The first one treats this matrix as a dense one, using the BLAS functions to solve the system of equations. The second one takes into account the sparse pattern of the Jacobian matrix, introducing the sparse function MA48 from Harwell. Both methodologies have been applied on two multibody system models with different sizes. The first model is a vehicle IVECO DAILY 35C15 with 17 degrees of freedom. The second one is a semi-trailer truck with 40 degrees of freedom. Taking as a reference the standard C/C + + implementation, the efficiency improvements that have been achieved using dense matrices (BLAS) have been of 15% and 50% respectively. The results in the first model have not improved significantly by using sparse matrices, but in the second one, the times with sparse matrices have been reduced 8% with respect to the BLAS ones.

  Abstract
  This article shows an efficient implementation of a dynamic semi-recursive formulation for large and complex multibody system simulations, with interesting applications in [...]

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• Un planteamiento probabilista de los criterios optimizantes mediante el principio de la máxima entropía

  S. Hernández, J. Díaz, A. Baldomir, F. Pereira

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  This work reviews A. B. Templemans research in the maximum entropy principle applied to structural optimization, which consists in defining a probabilistic approach for the optimality criteria. This new reasoning does not assume aprioristically which conditions could be active in the optimum point, giving a completely rational point of view to the optimization problem. After reviewing the state of the art, a new formulation, which simplifies and improves previous methodologies, is developed. This new method turns the optimization problem into solving successively systems of equations with the same dimension as the number of design variables. Since this algorithm requires obtaining first order sensitivities, it can be considered as a new gradient method. After the theoretical description, the algorithm is tested with two examples of truss structures. Results show a good performance of the algorithm, based on comparisons with other alternatives found in the literature.

  Abstract
  This work reviews A. B. Templemans research in the maximum entropy principle applied to structural optimization, which consists in defining a probabilistic approach for the [...]

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• Solución de la cinemática directa de la plataforma Gough-Stewart general usando un algoritmo híbrido de optimización

  E. Hernández-Martínez, S. Valdez-Peña, E. Sánchez-Soto

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  The direct kinematics problem for parallel robots can be stated as follows: given values of the joint variables, the corresponding Cartesian variable values, the pose of the end-effector, must be found. Most of the times the direct kinematics problem involves the solution of a system of non-linear equations. The most efficient methods to solve such kind of equations assume convexity in a cost function which minimum is the solution of the non-linear system. In consequence, the capacity of such methods depends on the knowledge about an starting point which neighboring region is convex, hence the method can find the global minimum. This article propose a method based on probabilistic learning about an adequate starting point for the Dogleg method which assumes local convexity of the function. The proposed method efficiently avoids the local minima, without need of human intervention or apriori knowledge, thus it shows a more robust performance than the simple Dogleg method or other gradient based methods. To demonstrate the performance of the proposed hybrid method, numerical experiments and the respective discussion are presented. The proposal can be extended to other structures of closed-kinematics chains, to the general solution of systems of non-linear equations, and to the minimization of non-linear functions.

  Abstract
  The direct kinematics problem for parallel robots can be stated as follows: given values of the joint variables, the corresponding Cartesian variable values, the pose of the [...]

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• Solución en dominios cuadrados de ecuaciones de difusión-convección mediante elementos finitos estocásticos espectrales en conjunto con el método de Petrov Galerkin en contracorriente

  D. Garzón-Alvarado, A. Ramírez-Martínez, C. Daza

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  In this paper we have developed the numerical solution of two problems of diffusion-convection (DC), using the finite element method of Streamline Upwind Petrov-Galerkin (SUPG). The parameters that define the behavior of the equations are modeled as stochastic fields, specifically, are used: the convective velocity, diffusion and heat capacity as values of random type. Therefore, we have included SUPG method to DC, with dominant convection, with the stochastic spectral finite element method. Each parameter was described by Karhunen-Loève expansion, while the unknown is represented by the polynomial expansion of the chaos. The objectives of the paper are: 1. To study the influence of stochastic fields in solving problems with SUPG DC and 2. Get the solution of each expansion unknown variable. The results show the versatility of the method for solving different physical problems due to the generality of the statistical description of the solution and the richness in the representation of the areas where there is the greater variability in response. The patterns shown in the unknown uncertainty depends on the dynamics of diffusion, convective velocity and the type of solution used.

  Abstract
  In this paper we have developed the numerical solution of two problems of diffusion-convection (DC), using the finite element method of Streamline Upwind Petrov-Galerkin (SUPG). [...]

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• Diseño óptimo del pico de lanzamiento de puentes lanzados de hormigón pretensado

  A. Fontán, S. Hernández, A. Baldomir, J. Díaz

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  The design of the launching nose of an incrementally launched bridge determines its constructive process and, therefore, also its dimensions. The optimization of the launching nose can raise as a first step to improve the design of a launched bridge. The conventional design process of a launching nose is based on trial and error method to reduce bending moment of prestressed concrete deck at the foremost support during launch. In this way, there is no guarantee that the obtained solution is the best among all the possible solutions since they all depend on the experience and intuition of a designer, and they are also restricted by a limited number of possible iterations. Given that launched bridges constitute an important constructive typology, all the available capacities of design innovation should be incorporated, among which it can be found numerical optimization. This research work proposes an objective and rigorous formulation to optimize a launching nose of launched bridge under real constraints that a bridge designer can encounter in practice. Comparing the results obtained by conventional process and that by optimization techniques, it can be verified that some of the assumptions, considered in classical design methods of a launching nose, are not based on any theoretical foundation. This fact demonstrates the utility of numerical optimization to improve a design.

  Abstract
  The design of the launching nose of an incrementally launched bridge determines its constructive process and, therefore, also its dimensions. The optimization of the launching [...]

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• Un elemento de sólido con una mejora en el comportamiento del corte transversal para el tratamiento de láminas

  F. Flores, E. Oñate

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  In this work a solid finite element based on a Total Lagrangian Formulation using logarithmic strains is combined with a classical assumed strain approach of the transverse strains for thick shells. The target is to use the element for shell simulations without shear locking. The selective mass scaling technique used to avoid that the discretization across the thickness reduce the critical time in codes with explicit integration of the momentum equations is summarized. Several examples are presented showing that the element is shear-locking free, the consequences of the selective mass scaling and the possibilities of the element for the analysis of composites laminates in non-linear material regime.

  Abstract
  In this work a solid finite element based on a Total Lagrangian Formulation using logarithmic strains is combined with a classical assumed strain approach of the transverse [...]

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• Patrones de Turing sobre superficies sometidas a deformación: un acercamiento desde el método lagrangiano total

  C. Duque-Daza, A. Ramirez, D. Garzón-Alvarado

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  In this work we have developed several numerical examples of reaction-diffusion equations with growing domain. For this purpose we have used the Schnakenberg reaction model with parameters in space Turing. Therefore numerical tests are performed on the appearance of Turing patterns on surfaces that have high deformation rate. For the solution of reaction diffusion equations is presented a solution method on surfaces in three dimensions using the finite element method under the use of the total Lagrangian formulation. The results show that the formation of Turing patterns depends on the features of surface deformation and the rate at which change in position of each point of the domain. These results can explain some phenomena of change of pattern on the surface of the skin of animals that exhibit characteristic spots.

  Abstract
  In this work we have developed several numerical examples of reaction-diffusion equations with growing domain. For this purpose we have used the Schnakenberg reaction model [...]

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• Validación numérica del comportamiento cíclico de conexiones interiores en estructuras con forjados reticulares

  J. Donaire-Ávila, A. Benavent-Climent

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  Several approaches are investigated to model interior reinforced concrete waffle-flat-plate-column connections. A model is proposed that provides very good results with reasonable low computational cost. The proposed model is validated with the experimental results obtained on a 3/5 scale specimen, subjected to quasi-static in cyclic loads up to collapse. To this end, the non-linear advanced theory of reinforced concrete is applied on a three-dimensional finite element model and non-linear analysis are conducted. Both fiber and layer elements are used for the one-dimensional and bi-dimensional components respectively. The main results of the simulation were: (i) the capacity curve obtained through out a push-over analysis with displacement control, (ii) the hysteretic curves of the slab, and (iii) the crack patterns. A very good agreement is found between numerical and experimental results.

  Abstract
  Several approaches are investigated to model interior reinforced concrete waffle-flat-plate-column connections. A model is proposed that provides very good results with reasonable [...]

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• Desenvolvimento de uma ferramenta computacional para a análise de elementos de membrana em concreto estrutural

  R. Souza

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  Reinforced concrete elements subjected to membrane forces, i.e., elements subjected to in-plane shear and axial stresses are very common for modeling complex structures such as aircraft hangars, nuclear power plants, offshore oil platforms and long-span bridges. While the design of reinforcement for membrane elements is well adressed the same can not be said regarding the analysis of performance of these elements. Into this context, the present paper aims at providing a numerical tool developed in the Matlab platform, taking into account the “Modified Compression Field Theory”. In order to certificate the performance of the proposed tool, extensive numerical results were compared with experimental results available in the literature. The obtained results revealed that the proposed tool is very confident for the analysis of reinforced concrete membrane elements.

  Abstract
  Reinforced concrete elements subjected to membrane forces, i.e., elements subjected to in-plane shear and axial stresses are very common for modeling complex structures such [...]

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• Un modelo numérico para la simulación de disolución de precipitados en aleaciones de aluminio con endurecimiento utilizando redes neuronales

  C. Saracibar, R. López, B. Ducoeur, M. Chiumenti, B. Meester

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  The motivation of this work is the modeling of the hardening precipitate and hardness evolutions of fully hardened heat treatable aluminium alloys during friction stir welding (FSW) and/or heat treatment processes. The model used is based on the kinetics of dissolution of precipitates model for hardened aluminium alloys given by Myhr and Grong (1991). This model contains a single independent variable, the time, and a single state variable, the volume fraction of hardening precipitates. A key point of this model is the identification of the effective activation energy for precipitates dissolution and the master curve defining the model, which was given by a look-up table. The goal of this work is to find an estimation of the effective activation energy and to model the dissolution rate of hardening precipitate in aluminium alloys using neural networks, avoiding the use of look-up tables. For this purpose a new and more convenient parametrization of the master curve is defined, a neural networks class is proposed, an objective functional is defined and a variational problem including independent parameters is solved. The novel methodology has been applied to different aluminium alloys, including the AA 6005A T6, AA 7449 T79 and AA 2198 T8. Experimental tests have been carried out for those aluminium alloys in order to get the HV1 hardness after isothermal heat treatments at different temperatures and for different treatment time durations. The effective activation energy for hardening precipitates dissolution and the master curve of the model have been obtained, using different network architectures, for the aluminium alloys considered in this work.

  Abstract
  The motivation of this work is the modeling of the hardening precipitate and hardness evolutions of fully hardened heat treatable aluminium alloys during friction stir welding [...]

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• Conmutación temporal entre técnicas numéricas implícita y explícita para simulación de estructuras no lineales inestables

  J. Curiel-Sosa, D. Owen

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  Simulation problems involving non-linear materials imply in numerous cases divergence of the implicit method which use return mapping algorithms for modelling of the nonlinear response. A switching implicit-explicit numerical technique in the context of Finite Element Methods is presented in this paper. Implicit/explicit mesh partitions are not considered whatsoever. Formulation for application to nonlinear hyperelastic materials and nonlinear elastic-plastic materials is provided. Furthermore, the response of the solid subjected to large deformations is presented and is embedded in the proposed technique. Numerical tests for nonlinear problems (geometric and/or material) showed the accurateness of the technique.

  Abstract
  Simulation problems involving non-linear materials imply in numerous cases divergence of the implicit method which use return mapping algorithms for modelling of the nonlinear [...]

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• Dimensionado en compresión en acero: el peso del pandeo

  J. Cervera, J. Ortiz, M. Vázquez, A. Aznar

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  The verification of the slender compressed members of a structure is a well formulated and codified problem. However, the non-linearity of the design process, combined with the no linearity of the physical problem requires an iterative process to define the piece that solves a given problem. This paper demonstrates an identity relationship between seemingly different problems, based on which we develop a theoretical approach and a simple procedure to determine, without iteration and with little margin for error, the piece needed for a given problem. The paper provides a statistical model to check that the provided procedure is safe and effective in the 98% of the problems in buildings —pillars and bars from trusses—. The presented approach therefore greatly facilitates decisions in this area.

  Abstract
  The verification of the slender compressed members of a structure is a well formulated and codified problem. However, the non-linearity of the design process, combined with [...]

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• Un algoritmo de contacto mortar aplicable a problemas tridimensionales

  F. Cavalieri, V. Fachinotti, A. Cardona

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  In this paper we propose a mortar algorithm for the study of contact mechanics in three dimensional elasticity problems. The projection surface used for integrating the equations is selected through a local cartesiana base defined in each contact element. In this way, some difficulties in the algorithm implementation as well as in the linearization of the equations are avoided. The proposed examples show that the algorithm satisfies the patch tests. Finally, we use the algorithm in an industrial application, the contact of an internal combustion engine valve with its seat.

  Abstract
  In this paper we propose a mortar algorithm for the study of contact mechanics in three dimensional elasticity problems. The projection surface used for integrating the equations [...]

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• Entorno geométrico eficiente para el modelado de imágenes en 3D

  M. Castilla, M. Ordóñez

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  The objective of this paper is exploring implementation of a realistic images reconstruction 3D using geometric algebra (GA). We illustrate the suitability of GA for representing structures and developing algorithms in computer graphics, especially for engineering applications as 3D images modeling. A first consequence is to propose an efficient framework model to be implemented in hardware programmable. The obtained results showed that using GA, the computations are less complex and shows as simple computations geometrical operations. The obtained model to hardware can be implemented as a next step in 3D image reconstruction. We also include the potential of GA for optimizations and highly efficient implementations.

  Abstract
  The objective of this paper is exploring implementation of a realistic images reconstruction 3D using geometric algebra (GA). We illustrate the suitability of GA for representing [...]

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• Un método de captura de choques basado en las funciones de forma para Galerkin discontinuo de alto orden

  E. Casoni, J. Peraire, A. Huerta

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  This article presents a high-order Discontinuous Galerkin method for compressible flow problems, in which is very frequent the formation of shocks. The stabilization is introduced by a new basis functions. This base has the flexibility to vary locally (within each element) between continuous polynomial functions space and a space of piecewise polynomial functions. Thus, the proposed method provides a bridge between the standard methods of high-order Discontinuous Galerkin and classical Finite Volume methods, maintaining the locality and compactness of the scheme. The variation of basis functions is automatically set according to the regularity of the solution and the stabilization is introduced by the jump operator, standard in Discontinuous Galerkin methods. Unlike the classical methods of slope limiting, the strategy here presented is very local, robust, and applies to any order of approximation. Moreover, the proposed method does not require adaptive mesh refinement techniques and it can be used with any temporal integration scheme. Several applications of the Euler equations are shown, demonstrating the validity and effectiveness of the method, especially for high orders of approximation.

  Abstract
  This article presents a high-order Discontinuous Galerkin method for compressible flow problems, in which is very frequent the formation of shocks. The stabilization is introduced [...]

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• Estabilidad de pórticos 2D en régimen elastoplástico

  M. Cacho-Pérez, P. López-Reyes, A. Lorenzana, J. Terán

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  The evaluation of the maximum level of load that any 2D framed structure can undergo, before plastic collapse or buckling, is addressed in this paper. The analytical approach, based on a beam element with elastic behaviour except on its ends, uses an incremental approach to determine when changes appear due to plastic behaviour. When the combination of axial force and bending moment in any cross-section reaches the plastic function, that section is considered to yield suddenly and relative displacements can appear because of the yielding. The model includes the traditional plastic hinge, which only considers relative rotation due to the effect of the bending moment. The sequential loading and yielding reduces the stiffness and stability of the frame, which is computed and compared with the classic plastic methods of analysis.

  Abstract
  The evaluation of the maximum level of load that any 2D framed structure can undergo, before plastic collapse or buckling, is addressed in this paper. The analytical approach, [...]

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• Una extensión del método de Nelder Mead a problemas de optimización no lineales enteros mixtos

  E. Brea

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  This article presents a new algorithm based on the Nelder-Mead simplex algorithmic method for identifying a local optimum, at least on unconstrained nonlinear mixed-integer problems. The algorithmic method, Integer Mixed Simplex Algorithm (IMSA), so called by the author, is based on a double simplex structure, which is composed of a real n -dimensional simplex structure (real simplex) and an integer n -dimensional simplex structure (integer simplex). The original Nelder-Mead operations are applied on the real simplex. Meanwhile, a novel group of operations are applied on the integer simplex. This new set of operations, together with the original Nelder-Mead operations, guarantee a new trail point at each IMSA iteration in the search of the local optimum in the integer real mixed 2n -dimensional numerical field ℝn×ℤn without the need of integer to real conversions.

  Abstract
  This article presents a new algorithm based on the Nelder-Mead simplex algorithmic method for identifying a local optimum, at least on unconstrained nonlinear mixed-integer [...]

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• Iber: herramienta de simulación numérica del flujo en ríos

  E. Bladé, L. Cea, G. Corestein, E. Escolano, J. Puertas, E. Vázquez-Cendón, J. Dolz, A. Coll

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  The recent requirements of Spanish regulations and directives, on their turn based on European directives, have led to the development of a new two dimensional open channel flow modelling tool. The tool, named Iber, combines a hydrodynamic module, a turbulence module and a sediment transport module, and is based in the finite volume method to solve the involved equations. The simulation code has been integrated in a pre-process and post-process interface based on GiD software, developed by CIMNE. The result is a flow and sediment modelling system for rivers and estuaries that uses advanced numerical schemes, robust and stable, which are especially suitable for discontinuous flows taking place in torrential and hydrologically irregular rivers.

  Abstract
  The recent requirements of Spanish regulations and directives, on their turn based on European directives, have led to the development of a new two dimensional open channel [...]

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• Integración temporal explícita con grandes pasos de tiempo de la ecuación de transmisión del calor

  P. Becker, N. Nigro, S. Idelsohn

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  We present a novel fully explicit time integration method that remains stable for large time steps, requires neither matrix inversions nor solving a system of equations and therefore allows for nearly effort-less parallelization. In this first paper the proposed approach is applied to solve conduction heat transfer problems, showing that it is stable for any time step as is the case with implicit methods but with a much lower computation time.

  Abstract
  We present a novel fully explicit time integration method that remains stable for large time steps, requires neither matrix inversions nor solving a system of equations and [...]

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• Un elemento de sólido con una mejora en el comportamiento del corte transversal para el tratamiento de láminas

  F. Flores, E. Oñate

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017).

  
  

  Abstract

  In this work a solid finite element based on a Total Lagrangian Formulation using logarithmic strains is combined with a classical assumed strain approach of the transverse strains for thick shells. The target is to use the element for shell simulations without shear locking. The selective mass scaling technique used to avoid that the discretization across the thickness reduce the critical time in codes with explicit integration of the momentum equations is summarized. Several examples are presented showing that the element is shear-locking free, the consequences of the selective mass scaling and the possibilities of the element for the analysis of composites laminates in non-linear material regime.

  Abstract
  In this work a solid finite element based on a Total Lagrangian Formulation using logarithmic strains is combined with a classical assumed strain approach of the transverse [...]

  • 0
  •  read