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• 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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• 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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• 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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• 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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• 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 [...]

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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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• 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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• 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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• 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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