Un modelo de elementos finitos con aproximación bidimensional por capas para el análisis de estructuras multilaminares

En este trabajo se presenta un modelo de elementos finitos con una aproximación. bidimensional por capas para el análisis de estructuras multilaminares tipo placa y lámina, plana en regímenes estático y dinámico. El elemento triangular desarrollado está basado en un elemento degenerado de 3D utilizando un campo de deformaciones impuestas de cortante. Las variables a través del espesor son eliminadas utilizando una técnica de condensación de variables. Se presentan ejemplos de aplicación de la formulación propuesta.A layer-wise finite element model for the analysis of composite plate and shell structures under static and dynamic loading is presented. The triangular element used is based on. degenerate solid theory and an assumed shear strain approach. The thickness variable are eliminated using a substructuring technique. Examples of application showing the good. performance of the formulation are given.Peer Reviewe

Nonlinear analysis of orthotropic membrane and shell structures including fluid-structure interaction

In this work, membrane and shell structures with large deformations are studied. In the structural part of this work, a new methodology for the analysis of geometrically nonlinear orthotropic membrane and rotation-free shell elements is developed based on the principal fiber orientation of the material. A direct consequence of the fiber orientation strategy is the possibility to analyze initially out-of lane prestressed membrane and shell structures. Additionally, since conventional membrane theory allows compression stresses, a wrinkling algorithm based on modifying the constitutive equation is presented. The structure is modeled with finite elements emerging from the governing equations of elastodynamics. the fluid part of this work is governed by the incompressible Navier-Stokes equations, which are modeled by stabilized equal-order interpolation finite elements. Since the monolithic solution for these equations has the disadvantage that take great computer effort to solve large algebraic system of equations, the fractional step methodology is used to take advantage of the computational efficiency given by the uncoupling of the pressure from the velocity field. In addition, the generalized-time integration scheme for fluids is adapted to be used with the fractional step technique.Postprint (published version

Characterization of the Epigenetic Changes During Human Gonadal Primordial Germ Cells Reprogramming

Epigenetic reprogramming is a central process during mammalian germline development. Genome-wide DNA demethylation in primordial germ cells (PGCs) is a prerequisite for the erasure of epigenetic memory, preventing the transmission of epimutations to the next generation. Apart from DNA demethylation, germline reprogramming has been shown to entail reprogramming of histone marks and chromatin remodelling. Contrary to other animal models, there is limited information about the epigenetic dynamics during early germ cell development in humans. Here, we provide further characterization of the epigenetic configuration of the early human gonadal PGCs. We show that early gonadal human PGCs are DNA hypomethylated and their chromatin is characterized by low H3K9me2 and high H3K27me3 marks. Similarly to previous observations in mice, human gonadal PGCs undergo dynamic chromatin changes concomitant with the erasure of genomic imprints. Interestingly, and contrary to mouse early germ cells, expression of BLIMP1/PRDM1 persists in through all gestational stages in human gonadal PGCs and is associated with nuclear lysine-specific demethylase-1. Our work provides important additional information regarding the chromatin changes associated with human PGCs development between 6 and 13 weeks of gestation in male and female gonads

An accurate nonlocal bonded discrete element method for nonlinear analysis of solids: application to concrete fracture tests

The final publication is available at Springer via http://dx.doi.org/10.1007/s40571-019-00278-5.We present a numerical procedure for elastic and nonlinear analysis (including fracture situations) of solid materials and structures using the discrete element method. It can be applied to strongly cohesive frictional materials such as concrete and rocks. The method consists on defining nonlocal constitutive equations at the contact interfaces between discrete particles using the information provided by the stress tensor over the neighbor particles. The method can be used with different yield surfaces, and in the paper, it is applied to the analysis of fracture of concrete samples. Good comparison with experimental results is obtained.Peer ReviewedPostprint (author's final draft

A coupled fluid FEM-DEM technique for predicting blasting operations in tunnels

We present recent developments in the coupling of the finite element method (FEM) and the discrete element method (DEM) for the analysis of rock blasting operations in tunnels. The coupled FEM-DEM technique has been proven to be an efficient procedure for predicting the multiple fractures of rock induced by the loads generated in blasting. The coupled FEM-DEM procedure is applied in tunnel construction, as well as to gas pressure blasting pyrotechnics to break rocks for the excavation of the tunnel front. In the latter case, the effect of gas explosion is modeled by solving the equations of gas dynamics in the analysis domain using FEM. The e¿ect of gas forces in the underlying rock mass is modeled via an embedded fluid-structure interaction method. The efficiency of the coupled FEM-DEM technique is demonstrated in several examples of fracture tests and rock blasting problems related to tunnel engineering. The examples presented indicate that the combination of the DEM with simple three-node linear triangular elements (for two-dimensional problems) captures the onset of fractures and their evolution accurately, accounting for the penetration of gas in the failure domain (Zárate & Oñate, 2015; Zárate, Cornejo, & Oñate, 2018).The authors acknowledge the financial support of the Tuñel project funded by the Spanish Ministry of Science and Innovation. (2015–2019) via the subprogram CIEN (IDI-20150705) and also the support of the EZUANA project (BIA2016-78544-R), funded by the Spanish Ministry of Education and Science of Spain.Peer ReviewedPostprint (published version

Posibilidades de los métodos numéricos en obras subterráneas

Se presenta un resumen de las posibilidades de diversos métodos numéricos basados en la combinación de técnicas de elementos finitos y de partículas para la simulación de problemas típicos de obras subterráneas, tales como la excavación de túneles y la inundación de cavidades.Preprin

Formulaciones tangente y secante en análisis no lineal de vigas Cosserat

En el desarrollo de este trabajo se ha estudiado en detalle el modelo clásico de viga Cosserat, su formulación tangente y las teorías de alto orden que se puede establecer con el. El análisis se ha realizado adoptando un punto de vista general que permite comparar la eficacia de diversos sistemas de parametrización de las rotaciones incluyendo en el análisis los sistemas de alta parametrización-y de distintas formas de interpolación de las variables cinemáticas: lineal o no lineal.Postprint (published version

Lagrangian analysis of multiscale particulate flows with the particle finite element method

The final publication is available at Springer via http://dx.doi.org/10.1007/s40571-014-0012-9We present a Lagrangian numerical technique for the analysis of flows incorporating physical particles of different sizes. The numerical approach is based on the particle finite element method (PFEM) which blends concepts from particle-based techniques and the FEM. The basis of the Lagrangian formulation for particulate flows and the procedure for modelling the motion of small and large particles that are submerged in the fluid are described in detail. The numerical technique for analysis of this type of multiscale particulate flows using a stabilized mixed velocity-pressure formulation and the PFEM is also presented. Examples of application of the PFEM to several particulate flows problems are given.Peer ReviewedPostprint (published version

Advances in the DEM and coupled DEM and FEM techniques in non linear solid mechanics

Abstract In this chapter we present recent advances in the Discrete Element Method (DEM) and in the coupling of the DEM with the Finite Element Method (FEM) for solving a variety of problems in non linear solid mechanics involving damage, plasticity and multifracture situations.Preprin