Alejandro Marcos Aragón

Alejandro Marcos Aragón
Delft University of Technology | TU · Department of Precision and Microsystems Engineering (PME)

Doctor of Philosophy
Looking for new opportunities.

About

48
Publications
9,082
Reads
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856
Citations
Introduction
Development of numerical methods and their applications to the computational design and/or analysis of novel materials • composites (e.g., heterogeneous microstructures) • phononic crystals • acoustic metamaterials • origami • topology optimization • single- and multi-objective optimization • contact mechanics • fracture mechanics • multiscale mechanics • immersed boundary (fictitious domain) problems • flow and fluid-structure interaction • massively parallel scientific computing.
Additional affiliations
December 2014 - present
Delft University of Technology
Position
  • Professor (Assistant)
May 2006 - October 2010
University of Illinois, Urbana-Champaign

Publications

Publications (48)
Preprint
Quantifying the nanomechanical properties of soft-matter using multi-frequency atomic force microscopy (AFM) is crucial for studying the performance of polymers, ultra-thin coatings, and biological systems. Such characterization processes often make use of cantilever's spectral components to discern nanomechanical properties within a multi-paramete...
Article
In this work, an object‐oriented geometric engine is proposed to solve problems with discontinuities, for instance, material interfaces and cracks, by means of unfitted, immersed or enriched finite element methods. Both explicit and implicit methods, such as geometric entities and level sets, are introduced to describe configurations of discontinui...
Article
Metamaterials can display unusual and superior properties that come from their carefully designed structure rather than their composition. Metamaterials have permeated large swatches of science, including electromagnetics and mechanics. Although metamaterials hold the promise for realizing technological advances, their potential to enhance interact...
Article
Full-text available
We propose a fully immersed topology optimization procedure to design structures with tailored fracture resistance under linear elastic fracture mechanics assumptions for brittle materials. We use a level set function discretized by radial basis functions to represent the topology and the Interface-enriched Generalized Finite Element Method (IGFEM)...
Preprint
Full-text available
We propose an enriched finite element formulation to address the computational modeling of contact problems and the coupling of non-conforming discretizations in the small deformation setting. The displacement field is augmented by enriched terms that are associated with generalized degrees of freedom collocated along non-conforming interfaces or c...
Preprint
Full-text available
Finding global optima in high-dimensional optimization problems is extremely challenging since the number of function evaluations required to sufficiently explore the design space increases exponentially with its dimensionality. Furthermore, non-convex cost functions render local gradient-based search techniques ineffective. To overcome these diffi...
Article
Stress analysis is an all‐pervasive practice in engineering design. With displacement‐based finite element analysis, directly‐calculated stress fields are obtained in a post‐processing step by computing the gradient of the displacement field–therefore less accurate. In enriched finite element analysis (EFEA), which provides unprecedented versatilit...
Article
Full-text available
An immersed enriched finite element method is proposed for the analysis of phononic crystals (PnCs) with finite element (FE) meshes that are completely decoupled from geometry. Particularly, a technique is proposed to prescribe Bloch–Floquet periodic boundary conditions strongly on non-matching edges of the periodic unit cell (PUC). The enriched fi...
Preprint
Full-text available
Metamaterials are artificial structures with unusual and superior properties that come from their carefully designed building blocks -- also called meta-atoms. Metamaterials have permeated large swatches of science, including electromagnetics and mechanics. Although metamaterials hold the promise for realizing technological advances, their potentia...
Article
Full-text available
During design optimization, a smooth description of the geometry is important, especially for problems that are sensitive to the way interfaces are resolved, e.g., wave propagation or fluid-structure interaction. A level set description of the boundary, when combined with an enriched finite element formulation, offers a smoother description of the...
Article
Full-text available
Enriched finite element methods have gained traction in recent years for modeling problems with material interfaces and cracks. By means of enrichment functions that incorporate a priori behavior about the solution, these methods decouple the finite element discretization from the geometric configuration of such discontinuities. Taking advantage of...
Article
Full-text available
The Hierarchical Interface-enriched Finite Element Method (HIFEM) is a technique for solving problems containing discontinuities in the field gradient using finite element meshes that do not conform (match) the domain morphology. The method is suitable for analyzing problems with complex geometries or when such geometry is not known a priori. Contr...
Preprint
Full-text available
During design optimization, a smooth description of the geometry is important, especially for problems that are sensitive to the way interfaces are resolved, e.g., wave propagation or fluid-structure interaction. A levelset description of the boundary, when combined with an enriched finite element formulation, offers a smoother description of the d...
Cover Page
Full-text available
Cover of issue 120 of the International Journal for Numerical Methods in Engineering.
Article
Full-text available
Generating matching meshes for finite element analysis is not always a convenient choice, for instance in cases where the location of the boundary is not known a priori or when the boundary has a complex shape. In such cases, enriched finite element methods can be used to describe the geometric features independently from the mesh. The Discontinuit...
Article
Full-text available
A new enriched finite element technique, named the Discontinuity-Enriched Finite Element Method (DE-FEM), was introduced recently for solving problems with both weak and strong discontinuities in 2-D. In this mesh-independent procedure, enriched degrees of freedom are added to new nodes collocated at the intersections between discontinuities and th...
Article
Full-text available
In this manuscript we thoroughly study the behavior of the virtual element method (VEM) in the context of two-dimensional linear elasticity problems for an engineering audience versed in standard FEM. Through detailed convergence studies we show the accuracy and the convergence rates recovered by VEM, and we compare them to those obtained by the h-...
Article
In this research, a universal framework for automated calibration of microscopic properties of modeled granular materials is proposed. The proposed framework aims at industrial scale applications, where optimization of the computational time step is important. It can be generally applied to all types of DEM simulation setups. It consists of three p...
Article
Full-text available
In this paper we propose a stress recovery procedure for low-order finite elements in 3-D. For each finite element, the recovered stress field is obtained by satisfying equilibrium in an average sense and by projecting the directly-calculated stress field onto a conveniently chosen space. Compared to existing recovery techniques, the current proced...
Article
Full-text available
We introduce a new methodology for modeling problems with both weak and strong discontinuities independently of the finite element discretization. At variance with the eXtendend/Generalized Finite Element Method (X/GFEM), the new method, named the Discontinuity-Enriched Finite Element Method (DE-FEM), adds enriched degrees of freedom only to nodes...
Article
Full-text available
This research aims at developing a universal methodology for automated calibration of microscopic properties of modelled granular materials. The proposed calibrator can be applied for different experimental set-ups. Two optimization approaches: (1) a genetic algorithm and (2) DIRECT optimization, are used to identify discrete element method input m...
Article
We present a structure preserving numerical algorithm for the collision of elastic bodies. Our integrator is derived from a discrete version of the field-theoretic (multisymplectic) variational description of nonsmooth Lagrangian continuum mechanics, combined with generalized Lagrange multipliers to handle inequality constraints. We test the result...
Conference Paper
The numerical modeling of phononic crystals using the finite element method requires a mesh that accurately describes the geometric features. In an optimization setting, involving shape and/or topological changes, this implies that a new matching mesh needs to be generated in every design iteration. In this paper a mesh-independent description for...
Article
Topology optimization formulations using multiple design variables per finite element have been proposed to improve the design resolution. This paper discusses the relation between the number of design variables per element and the order of the elements used for analysis. We derive that beyond a maximum number of design variables, certain sets of m...
Article
Generating matching meshes for problems with complex boundaries is often an intricate process, and the use of non-matching meshes appears as an appealing solution. Yet, enforcing boundary conditions on non-matching meshes is not a straightforward process, especially when prescribing those of Dirichlet type. By combining a type of Generalized Finite...
Article
The design of a microvascular flow network embedded in an actively-cooled polymeric material is pre-sented. A multi-objective Genetic Algorithm (GA) com-bined with the finite element method is first used to determine the quasi-optimized network configurations and provide insight into the behavior of the actively-cooled material. The objective funct...
Article
The detection phase in computational contact mechanics can be subdivided into a global search and a local detection. When potential contact is detected by the former, a rigorous local detection determines which sur-face elements come or may come in contact in the current increment. We first introduce a rigorous definition of the closest point for n...
Article
Full-text available
The last few years have seen the proliferation of measures that quantify the scientific output of researchers. Yet, most of these measures focus on productivity, thus fostering the ‘‘publish or perish’’ paradigm. This article proposes a measure that aims at quantifying the impact of research de-emphasizing productivity, thus providing scientists an...
Article
The effect of in-plane deformations on the failure response of heterogeneous adhesives with a second phase of spherical elastic particles is investigated numerically using a 3D cohesive framework. The methodology includes a new interface-enriched generalized finite element scheme for the solution of structural problems with weak discontinuities, al...
Article
Generating matching meshes for problems with complex boundaries is often an intricate process, and the use of non-matching meshes appears as an appealing solution. Yet, enforcing boundary conditions on non- matching meshes is not a straightforward process, especially when prescribing those of Dirichlet type. By combining a generalized finite elemen...
Data
a b s t r a c t This work discusses the computational design of microvascular polymeric materials, which aim at mimicking the behavior found in some living organisms that contain a vascular sys-tem. The optimization of the topology of the embedded three-dimensional microvascular network is carried out by coupling a multi-objective constrained genet...
Article
This article discusses an efficient implementation of tensors of arbitrary rank by using some of the idioms introduced by the recently published C++ ISO Standard (C++11). With the aims at providing a basic building block for high-performance computing, a single Array class template is carefully crafted, from which vectors, matrices, and even higher...
Article
A new generalized FEM is introduced for solving problems with discontinuous gradient fields. The method relies on enrichment functions associated with generalized degrees of freedom at the nodes generated from the intersection of the phase interface with element edges. The proposed approach has several advantages over conventional generalized FEM f...
Article
This paper describes a framework for the design of microvascular polymeric components for active cooling applications. The design of the embedded networks involves complex and competing objectives that are associated with various physical processes. The optimization tool includes a PDE solver based on advanced finite element techniques coupled to a...
Article
Full-text available
Microvascular networks show promise for applications such as self-healing, self-cooling, and structural damage sensing. Fluid-filled micro-scale channels have been investigated extensively in the field of microfluidics, but three-dimensional networks in polymeric structural materials have been achieved only recently. The purpose of microvascular ne...
Data
Microvascular networks show promise for applications such as self-healing, self-cooling, and structural damage sensing. Fluid-filled micro-scale channels have been investigated extensively in the field of microfluidics, but three-dimensional networks in polymeric structural materials have been achieved only recently. The purpose of microvascular ne...
Article
Microvascular networks show promise for applications such as self-healing, self-cooling, and structural damage sensing. Fluid-filled micro-scale channels have been investigated extensively in the field of microfluidics, but three-dimensional networks in polymeric structural materials have been achieved only recently. The purpose of microvascular ne...
Article
Biomimetic microvascular networks with complex architectures are embedded in epoxy matrices using direct-write assembly. Fluid transport in multi-generation bifurcating channels is systematically investigated and maximum flow efficiency is found to occur when Murray's law is obeyed. Nature is replete with examples of vascular networks, whose primar...
Article
Biomimetic microvascular materials are increasingly considered for a variety of autonomic healing, cooling and sensing applications. The microvascular material of interest in this work consists of a network of hollow microchannels, with diameters as small as 10 μm, embedded in a polymeric matrix. Recent advances in the manufacturing of this new cla...
Data
Biomimetic microvascular networks with complex architectures are embedded in epoxy matrices using direct-write assembly. Fluid transport in multi-generation bifurcating channels is systematically investigated and maximum flow efficiency is found to occur when Murray's law is obeyed. Nature is replete with examples of vascular networks, whose primar...
Article
A multi-objective genetic algorithm is used to design 2D and 3D microvascular networks embedded in bio-mimetic self-healing/self-cooling polymeric materials. Various objective functions and constraints are considered, ranging from flow efficiency and homogeneity to network redundancy and void volume fraction. The design variables include the networ...
Article
A general GFEM/XFEM formulation is presented to solve two-dimensional problems characterized by C 0 continuity with gradient jumps along discrete lines, such as those found in the thermal and structural analysis of heterogeneous materials or in line load problems in homogeneous media. The new enrichment functions presented in this paper allow solvi...
Conference Paper
The next generation of self-healing polymeric materials will allow multiple healing events through the integration of complex three-dimensional microvascular networks. Traditional techniques for creating these networks, such as soft lithography, do not readily scale to the third dimension. New approaches must therefore be developed to enable the fa...
Data
Full-text available
Inspired by natural examples of microvascular systems in a wide variety of living organisms, we perform the computational design of a new class of polymer-based composite materials with the unique ability to heal and/or cool in a completely autonomic fashion, i.e., without any external intervention. The design process combines graph theory to repre...
Article
This article discusses an efficient implementation of tensors of arbitrary rank that can be used as a basic building block for high-performance computing through the use of some of the C ++ paradigms introduced by the new C++11 requirements of the standard library. By using templates, an extra high-level layer can be added to the C ++ language when...

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