Multiscale computational homogenization: review and proposal of a new enhanced-first-order method

This is a copy of the author 's final draft version of an article published in the Archives of computational methods in engineering. The final publication is available at Springer via http://dx.doi.org/10.1007/s11831-016-9205-0The continuous increase of computational capacity has encouraged the extensive use of multiscale techniques to simulate the material behaviour on several fields of knowledge. In solid mechanics, the multiscale approaches which consider the macro-scale deformation gradient to obtain the homogenized material behaviour from the micro-scale are called first-order computational homogenization. Following this idea, the second-order FE2 methods incorporate high-order gradients to improve the simulation accuracy. However, to capture the full advantages of these high-order framework the classical boundary value problem (BVP) at the macro-scale must be upgraded to high-order level, which complicates their numerical solution. With the purpose of obtaining the best of both methods i.e. first-order and second-order, in this work an enhanced-first-order computational homogenization is presented. The proposed approach preserves a classical BVP at the macro-scale level but taking into account the high-order gradient of the macro-scale in the micro-scale solution. The developed numerical examples show how the proposed method obtains the expected stress distribution at the micro-scale for states of structural bending loads. Nevertheless, the macro-scale results achieved are the same than the ones obtained with a first-order framework because both approaches share the same macro-scale BVP.Peer ReviewedPostprint (author's final draft

Las acequias de careo, un dispositivo pionero de recarga artificial de acuíferos en Sierra Nevada, España. Caracterización e inventario

Las acequias de careo constituyen uno de los primeros dispositivos para la recarga artificial de acuíferos de la Península Ibérica. Operativas desde el periodo musulmán, presentan un sistema de construcción y distribución del agua inteligente y todavía operativo en la actualidad, lo que constituye un ejemplo a tener en cuenta en la gestión hídrica. En este artículo se ha realizado una recopilación bibliográfica de su origen, modo de construcción y funcionamiento, actualizado el inventario existente, estudiado en qué contexto geológico fueron construidas y obtenido una serie de recomendaciones prácticas a tener en cuenta en el diseño y gestión de sistemas de recarga artificial superficial de acuíferos

Estudio de dispositivo de Edge Computing con acelerador hardware de redes neuronales convolucionales basado en arquitectura RISC-V

RISC-V es una arquitectura abierta emergente que está cogiendo fuerza para una gran cantidad de aplicaciones de bajo consumo e IoT. Sin embargo, con la estabilización de las extensiones base de la arquitectura, y el comienzo de comercialización de SoCs basados en RISC-V, como el Kendryte K210 (con un precio de 5 dólares), surge la cuestión de si verdaderamente el estándar abierto acaba siendo una facilidad para los desarrolladores de aplicaciones sobre la plataforma. Se han evaluado los entornos de desarrollo, el toolchain, los procesos de depuración relacionados con la placa de desarrollo Sipeed MAIX Go, así como el SDK standalone y el port de Micro Python para el K210. También se ha estudiado el pipeline de entrenamiento para el acelerador de redes neuronales convolucionales del Kendryte K210, con soporte de Tiny YOLO v2.Se ha realizado una aplicación prueba de concepto de IoT EDGE de reconocimiento de objetos basada en IA acelerada por hardware, de bajo coste y consumo energético, con la funcionalidad de cámara de seguridad capaz de distinguir en el propio dispositivo, y no en la nube, si lo que aparece en imagen es una persona o una mascota mediante detección de objetos, para reducir el número de interacciones del usuario de la aplicación. Además, se ha probado la versatilidad de la aplicación con el uso de otro modelo preentrenado para la detección de posicionamiento correcto de mascarillas en transeúntes en el contexto de la pandemia COVID-19. Finalmente, se ha analizado el rendimiento del dispositivo SiPEED Maix Go, y el uso de ancho de banda y consumo en comparación con un dispositivo ya en el mercado.A lo largo del proceso se ha constatado que la documentación para desarrolladores es escasa, los entornos de desarrollo se encuentran en un estado de poca madurez, y los procesos de depuración en ocasiones son inexistentes. Sin embargo, las capacidades de IA, el rendimiento que ofrece, el bajo consumo del dispositivo, y la reducción de uso de ancho de banda pueden resultar en un posible auge del uso de este tipo de dispositivos para IoT, así como el auge del Edge Computing y el AIoT.Este trabajo fue finalmente sometido al congreso internacional DCIS 2020 como un artículo de seis páginas de extensión con título: Developing an AI IoT application with open software on a RISC-V SoC (Anexo A).<br /

Structural analyses of orthogrid fuselage panel for integrated Ku-band SatCom antenna

The aim of this work is to describe the structural analysis of a multifunctional aircraft fuselage panel. The structure of the panel has an embedded antenna tiles. The panel consists of UniDirectional (UD) carbon fibre reinforced composite skin stiffened with ortho-grid ribs, and a transparent skin window made using UD glass fibre reinforced composite. The orthogrid structure is a structural reinforcement but also the antenna tiles support. The presented work proposes a numerical multiscale strategy. The laminate is simulated with solid elements, in order to capture the real kinematics of the material, but several laminas are condensed in a single finite element. The performance of each lamina is obtained using the Serial-Parallel (SP) mixing theory. The specific formulations developed have been very useful to identify and study the mechanical performance of these new structures and the localization of unknown and un-predicted hot-spots in the structure.Postprint (published version

Multi-scale procedure for the mechanical analysis of composite laminate structures considering mixed boundary conditions

This paper presents a multi-scale procedure for the study of flat composite structures with discontinuities. In this procedure, the structure is solved using shell elements while the laminate performance and the structural discontinuities (e.g. connections or change in the laminate thickness) are analysed with a subscale model made with solid 3D elements. The kinematics of both models are coupled following the Kirchhoff–Love theory. This coupling is used during the homogenization procedure where the characteristic behavior of the different micro-models is obtained. Periodical boundary conditions are used for the laminates whereas a combination between periodical and linear boundary conditions are used for the discontinuities. The proposed procedure allows to reproduce accurately the structure elastic behaviour, as well as the stress and strain states in regions with discontinuities, which until now could only be accurately simulated by means of expensive numerical models using volumetric solid elements.This work has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement № 101006860 (FIBRE4YARDS project) and under grant agreement № 952966 (FIBREGY project). In addition, this research work is framed within an FI doctoral grant awarded by the Generalitat de Catalunya and co-financed jointly with the European Union . These supports are gratefully acknowledged.Peer ReviewedPostprint (published version

Multiscale numerical modelling of microstructured reinforced composites

Most of the existing materials around us can be considered composite materials, since they are composed by several phases or components at certain spatial scale. The physical and chemical properties of composites, as occurs with structures composed by two or more materials, is de¿ned by the response provided by their constituents. Therefore, a good characterization of the composite requires con-sidering the performance of its components. In the last decades, several methods have been proposed with this approach to characterize composite materials, most of them based on multiscale techniques.Peer ReviewedPostprint (published version

Strategy for an efficient material non-linear multiscale analysis

As the internal microstructure of composite materials becomes more complex, multi-scale methods are gaining strength. These allow obtaining the material performance from the analysis of a representative volume element. The use of multiscale procedures is also encouraged by the increase of computational capacity. However, despite of this increase, performing a non-linear multiscale analysis of a real structure is still chimeric due to its computational cost. This work presents a strategy to conduct non-linear multiscale analysis in an efficient way. It is based in the definition of a threshold function, which is developed specifically for each micro-model using its specific strain field. The procedure allows a large reduction of the computational cost, facilitating its use by researchers and engineers without large computational means. The validity of the proposed strategy is shown with the analysis of a pultruded cantilever beam. The results obtained prove the efficiency of the method.Postprint (published version

A unified approach for high order sensitivity analysis

6th International Conference on Computer Aided Optimun Design of Structures, 2001, Bologna[Abstract] Many engineering problems require solving PDEs by means of numerical methods (type FEM/BEM) which sensivity analysis entails taking derivatives of functions defined through integration. In sizing optimization problems, the integration domains are fixed, what enables the regular use of analytical sensitivity techniques. In shape optimization problems, the integration domains are nevertheless variable. This fact causes some cumbersome difficulties [1], that have traditionally been overcome by means of finite difference approximations [2]. Three kinds of analytical approaches have been proposed for computing sensitivity derivatives in shape optimization problems. The first is based on differentiation of the final discretized equations [1]. The second is based on variation of the continuum equations [1] and on the concept of material derivative. The third is based upon the existence of a mapping that links the material space with a fixed space of reference coordinates [3]. This is not restrictive, since such a transformation in inherent to FEM and BEM implementations. In this paper, we present a generalization of the latter approach on the basis of a unified procedure for integration in manifolds. Our aim is to obtain a single, unified, compact procedure to compute arbitrarily high order directional dreivatives of the objective function and the constraints in FEM/BEM shape optimization problems. Special care has been taken on heading for easy-to-compute recurrent expressions. The proposed scheme is basically independent from the specific form of the state equations, and can be applied to both, direct and adjoint state formulations. Thus, its numerical implementation in current engineering codes is straightforward. An application example is finally presented.Xunta de Galicia; PGIDT99MAR11801Ministerio de Economía y Competitividad; TIC-98-029

High Order Shape Design Sensitivity: A Unified Approach

[Abstract] Three basic analytical approaches have been proposed for the calculation of sen- sitivity derivatives in shape optimization problems. The first approach is based on differentiation of the discretized equations [1-3]. The second approach is based on variation of the continuum equations [1,4,5] and on the concept of material deriva- tive. The third approach [6] is based upon the existence of a transformation that links the material coordinate system with a fixed reference coordinate system. This is not restrictive, since such a transformation is inherent to FEM and BEM imple- mentations. In this paper we present a generalization of the latter approach on the basis of a generic unified procedure for integration in manifolds. Our aim is to obtain a single, unified, compact expression to compute arbitrarily high order directional deriva- tives, independently of the dimension of the material coordinates system and of the dimension of the elements. Special care has been taken on giving the final results in terms of easy-to-compute expressions, and special emphasis has been made in holding recurrence and simplicity of intermediate operations. The proposed scheme does not depend on any particular form of the state equations, and can be applied to both, direct and adjoint state formulations. Thus, its numerical implementation in standard engineering codes should be considered as a straightforward process. As an example, a second order sensitivity analysis is applied to the solution of a 3D shape design optimization problem.Ministerio de Ciencia y Tecnología; TIC-94-110