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• A State of the Art Review of the Particle Finite Element Method (PFEM)

  M. Cremonesi, A. Franci, S. Idelsohn, E. Oñate

  Archives of Computational Methods in Engineering (2020). Vol. 27, pp. 1709–1735, 2020

  
  

  Abstract

  The particle finite element method (PFEM) is a powerful and robust numerical tool for the simulation of multi-physics problems in evolving domains. The PFEM exploits the Lagrangian framework to automatically identify and follow interfaces between different materials (e.g. fluid–fluid, fluid–solid or free surfaces). The method solves the governing equations with the standard finite element method and overcomes mesh distortion issues using a fast and efficient remeshing procedure. The flexibility and robustness of the method together with its capability for dealing with large topological variations of the computational domains, explain its success for solving a wide range of industrial and engineering problems. This paper provides an extended overview of the theory and applications of the method, giving the tools required to understand the PFEM from its basic ideas to the more advanced applications. Moreover, this work aims to confirm the flexibility and robustness of the PFEM for a broad range of engineering applications. Furthermore, presenting the advantages and disadvantages of the method, this overview can be the starting point for improvements of PFEM technology and for widening its application fields.

  Abstract
  The particle finite element method (PFEM) is a powerful and robust numerical tool for the simulation of multi-physics problems in evolving domains. The PFEM exploits the Lagrangian [...]

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• Modelling 3D metal cutting problems with the particle finite element method

  J. Carbonell, . J.M.Rodríguez, E. Oñate

  Computational Mechanics (2020). Vol. 66, pp. 603–624, 2020

  
  

  Abstract

  This work presents the development of the Particle Finite Element Method (PFEM) for the modelling of 3D solid mechanics problems under cutting conditions. The study and analysis of numerical models reproducing the cut of a material is a matter of interest in several areas; namely, the improvement of the material properties, the optimization of the process and tool geometries and the prediction of unexpected failures. The analysis of bi-dimensional (2D) models is the most common approach for different reasons. Just focusing on the simulation point of view, it is the simplest procedure, the cheapest in terms of computational cost and sometimes the only feasible numerical solution. However, many industrial machining processes, such as cutting, blanking, milling and drilling have not a possible simplification to 2D models. Actually even a simple turning processes for non-orthogonal cuts can not be simplified to 2D. This work present an upgrade of the PFEM techniques in order to deal with the 3D machining problems. We present recent improvements in the finite element formulation, the meshing re-connections and the contact detection. By applying these developments the PFEM has the capability for modelling a wide range of practical machining processes. In this paper the capacity of the formulation and the accuracy of the results are analyzed and validated with some representative examples.

  Abstract
  This work presents the development of the Particle Finite Element Method (PFEM) for the modelling of 3D solid mechanics problems under cutting conditions. The study and analysis [...]

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• Análisis sismo-resistente de edificios mixtos de acero y hormigón armado

  R. Ugel, L. Pujades, N. Guerrero, R. Herrera

  Monograph Series in Earthquake Engineering (2020). MIS78

  
  

  Abstract

  In this study it was assessed the seismic behavior of framed buildings with composite structure of steel and reinforced concrete (RC) in a specific configuration formed with lower levels with RC (primary structure) and higher levels with steel (secondary structure) as structural materials for components. Levels with steel elements correspond to the higher or two higher levels of the buildings. Static and dynamic nonlinear analyses were conducted to determine the parameters of capacity, fragility and damage of structural systems. These analyses were based on criteria and methodologies such as Spectrum-Capacity, Adaptive Pushover and the Capacity Parametric Model. The difference in performance was remarkable in some models depending on rigidities and the heights of models. Fragility curves and damage indices were determined using two different methodologies in order to assert the behavior in terms of reliability and it was evidenced that in some structural systems there is a great probability of zero damage while in others predominate a high probability of reach moderate, severe or collapse damage states. In Time-History and Incremental Dynamic analysis, were used 5 real and 5 synthetic accelerograms. Numerical results show that most of the models suffer significant lateral deformations, often reaching beyond acceptable limits states from the Venezuelan normative. It was performed a experimental test of a two level frame with Steel elements in the higher level and Reinforced Concrete elements in the lower level. Another experimental test was performed on a full-scale mixed Steel-Reinforced Concrete joint. Both tests were subjected to cyclic lateral loads in order to determine its characteristics, behavior and capacity to histeretics actions in terms of stiffness degradation and damage evolution. Concerning to capacity and damage indexes, it was showed the influence of horizontal relative displacements of each level and the stiffness degradation as key parameters in determining the damage to a building. All this was revalidated with a probabilistic approach to the Damage Index. Experimental results showed very similar values in absolute and relative terms to those obtained in the numerical models. In these numerical and experimental process was used the Capacity Parametric Model (CPM) and the fragility and damage models associated with this methodology. Too achieve structural continuity at the structural joint of steel columns with reinforced concrete elements, it was evidenced that it can be used the AISC and ASCE design criteria for base-plates for steel columns

  Abstract
  In this study it was assessed the seismic behavior of framed buildings with composite structure of steel and reinforced concrete (RC) in a specific configuration formed with [...]

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• Pushover con acoplamiento de CEINCI-LAB y OpenSees

  R. Aguiar, B. Cagua, J. Pilatasig

  (2020). MIS77

  
  

  Abstract

  The static non-linear analysis allows us to know the probable seismic performance that a structure will have, this by obtaining the resistant seismic capacity curve that relates the basal shear with the lateral displacement at the top of the building and not only that, but that the sections that enter the non-linear range are determined. This information is very useful for the Structural Designer who will be able to visualize if the performance that the building is going to have is in accordance with what he expected from his design, otherwise it is time to make corrections to his design, in this way it will be you are optimizing work. For this reason, it was decided to write this work, which will undoubtedly be very useful for those students who decided to venture into nonlinear static analysis (Pushover), a rather complex subject if you want to know in depth the theory of calculus and not just program user.

  Abstract
  The static non-linear analysis allows us to know the probable seismic performance that a structure will have, this by obtaining the resistant seismic capacity curve that relates [...]

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• Numerical tools for computational design of acoustic metamaterials

  D. Roca, J. Cante, O. Lloberas-Valls, X. Oliver

  Monograph CIMNE (2020). M191

  
  

  Abstract

  The notion of metamaterials as artificially engineered structures designed to obtain specific material properties, typically unachievable in naturally occurring materials, has captured the attention of the scientific and industrial communities. Among the broad range of applications for such kind of materials, in the field of acoustics, the possibility of creating materials capable of efficiently attenuating noise in target frequency ranges is of utmost importance for a lot of industrial areas. In this context, the so-called locally resonant acoustic metamaterials (LRAMs) can play an important role, as their internal topology can be designed to exhibit huge levels of attenuation in specific frequency regions by taking advantage of internal resonance modes. With a proper, optimized topological design, LRAMs can be used, for instance, to build lightweight and thin noise insulation panels that operate in a low-frequency regime, where standard solutions for effectively attenuating the noise sources require dense and thick materials. Given the importance of the topological structure in obtaining the desired properties in acoustic metamaterials, the use of novel numerical techniques can be exploited to create a set of computational tools aimed at the analysis and design of optimized solutions. These are based on three fundamental pillars: (1) the multiscale homogenization of complex material structures in the microscale to get a set of effective properties capable of describing the material behavior in the macroscale, (2) the model-order reduction techniques, which are used to decrease the computational cost of heavy computations while still maintaining a sufficient degree of accuracy, and (3) the topology optimization methods that can be employed to obtain optimal configurations with a given set of constraints and a target material behavior. This set of computational tools can be applied to design acoustic metamaterials that are both efficient and practical, i.e. they behave according to their design specifications and can be produced easily, for instance, making use of novel additive manufacturing techniques.

  Abstract
  The notion of metamaterials as artificially engineered structures designed to obtain specific material properties, typically unachievable in naturally occurring materials, [...]

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• Innovative mathematical and numerical models for studying the deformation of shells during industrial forming processes with the Finite Element Method

  V. Mataix Ferrándiz, E. Oñate, R. Rossi

  Monograph CIMNE (2020). M190

  
  

  Abstract

  This document contains the result resulting from the work in the doctoral thesis Innovative mathematical and numerical models for studying the deformation of shells during industrial forming processes with the Finite Element Method. The objective of this thesis is to contribute to the development of finite element methods for the analysis of the stamping processes, an area of problems with a very clear industrial application. Indeed these kinds of problems involve multiple disciplines and require the understanding of different mechanical problems, being the most relevant disciplines the continuous mechanics, the plasticity, contact problems, among others, depending of the problematic of study.

  Abstract
  This document contains the result resulting from the work in the doctoral thesis Innovative mathematical and numerical models for studying the deformation of shells during [...]

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• Towards the Virtual Wind Tunnel for civil engineering applications

  R. Zorrilla, E. Oñate, R. Rossi

  Monograph CIMNE (2020). M189

  
  

  Abstract

  This monograph develops a numerical tool (the Virtual Wind Tunnel, VWT) for the reso-lution of problems involving fluid flow around structures. Due to the limitations that traditional methods may have in this context, the VWT is based on the use of fixed mesh technologies (CutFEM-type) combined with an implicit representation of the embedded bodies. One of the main contributions of the monograph is the use of such fixed mesh methods to solve lightweight thin-walled structures problems. Hence, two embedded formulations capable of representing the flow around bodies with and without internal volume are proposed. The first one results in a simpler implementation and lower computational effort but can only represent a slip behavior of the wall. The second one gets rid of such limitation by including a Nitsche imposition of the Navier-slip condition, thus allowing modelling any wall behavior as a wall law would do. The applicability range of the VWT includes the fluid–structure i nteraction problem (FSI). To that purpose an improvement for the boundary condition imposition of the FM-ALE algorithm mesh motion problem is also proposed. Moreover, the implementation, which has been conceived to be easily extended to any other coupled problem, is also treated. The validation of the technologies within the VWT includes multiple theoretical test cases as well as feasible industrial applications. Among these, the FSI analysis of a 4-point tent during a strong wind episode deserves to be highlighted as it showcases the achievement of the initial objective of the monograph.

  Abstract
  This monograph develops a numerical tool (the Virtual Wind Tunnel, VWT) for the reso-lution of problems involving fluid flow around structures. Due to the limitations that [...]

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• Partitioned analysis of coupled mechanical systems

  C. Felippa, K. Park, C. Farhat

  Computer Methods in Applied Mechanics and Engineering (2001). Vol. 190 (24-25), pp. 3247-3270

  
  

  Abstract

  This is a tutorial article that reviews the use of partitioned analysis procedures for the analysis of coupled dynamical systems. Attention is focused on the computational simulation of systems in which a structure is a major component. Important applications in that class are provided by thermomechanics, fluid–structure interaction and control–structure interaction. In the partitioned solution approach, systems are spatially decomposed into partitions. This decomposition is driven by physical or computational considerations. The solution is separately advanced in time over each partition. Interaction effects are accounted for by transmission and synchronization of coupled state variables. Recent developments in the use of this approach for multilevel decomposition aimed at massively parallel computation are discussed.  

  Abstract
  This is a tutorial article that reviews the use of partitioned analysis procedures for the analysis of coupled dynamical systems. Attention is focused on the computational [...]

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• Parametrized variational principles for linear electromagnetodynamics

  C. Felippa, J. Schuler

  (1993). Coupled structural, thermal, phase-change and electromagnetic analysis for superconductors, vol. 2

  
  

  Abstract

  Two families of parametrized mixed variational principles for linear electromagnetody-namics are constructed. The first family is applicable when the current density distribution is known a priori. Its six independent fields are magnetic intensity and flux density, magnetic potential, electric intensity and flux density and electric potential. Through appropriate spe-cialization of parameters the first principle reduces to more conventional principles proposed in the literature. The second family is appropriate when the current density distribution and a conjugate Lagrange multiplier field are adjoined, giving a total of eight independently varied fields. In this case it is shown that a conventional variational principle exists only in the time-independent (static) case. Several static functionais with reduced number of varied fields are presented. The application of one of these principles to construct finite elements with current prediction capabilities is illustrated with a numerical example.

  Abstract
  Two families of parametrized mixed variational principles for linear electromagnetody-namics are constructed. The first family is applicable when the current density distribution [...]

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• Top-down derivation of doubly asymptotic approximations for structure - fluid interaction analysis

  C. Felippa

  (1968). Proceedings of the Second International Symposium on Innovative Numerical Analysis in Applied Engineering Sciences

  
  

  Abstract

  This paper focuses on a class of transient response problems in which a flexible structure is submerged in an acoustic fluid satisfying the three-dimensional wave equation. The structure is discretized by finite element methods while the external fluid is modelled by boundary integral techniques resulting in the appearance of a grid of boundary elements on the 'wet' structural surface.

  Abstract
  This paper focuses on a class of transient response problems in which a flexible structure is submerged in an acoustic fluid satisfying the three-dimensional wave equation. [...]

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