Continuous and discontinuous modelling of ductile fracture

In many metal forming processes (e.g. blanking, trimming, clipping, machining, cutting) fracture is triggered in order to induce material separation along with a desired product geometry. This type of fracture is preceded by a certain amount of plastic deformation and requires additional energy to be supplied in order for the crack to propagate. It is known as ductile fracture, as opposed to brittle fracture (as in ceramics, concrete, etc). Ductile fracture originates at a microscopic level, as the result of voids initiated at inclusions in the material matrix. These microscopic degradation processes lead to the degradation of the macroscopic mechanical properties, causing softening, strain localisation and finally the formation of macroscopic cracks. The initiation and propagation of cracks has traditionally been studied by fracture mechanics. Yet, the application of this theory to ductile fracture, where highly nonlinear degradation processes (material and geometrical) take place in the fracture process zone, raises many questions. To model these processes, continuum models can be used, either in the form of softening plasticity or continuum damage mechanics. Yet, continuous models can not be applied to model crack propagation, because displacements are no longer continuous across the crack. Hence, a proper model for ductile fracture requires a different approach, one that combines a continuous softening model with a strategy to represent cracks, i.e. displacement discontinuities. This has been the main goal of the present work. In a combined approach, the direction of crack propagation is automatically determined by the localisation pattern, and its rate strongly depends on the evolution of damage (or other internal variables responsible for the strain softening). This contrasts with fracture mechanics, where the material behaviour is not directly linked to the crack propagation criteria. Softening materials have to be supplied with an internal length, which acts as a localisation limiter, thereby ensuring the well-posedness of the governing partial differential equations and mesh independent results. For this purpose, a nonlocal gradient enhancement has been used in this work, which gives similar results to nonlocal models of an integral form. A number of numerical methods are available to model displacement discontinuities in a continuum. In the present context, we have used a remeshing strategy, since it has additional advantages when used with large strain localising material models: it prevents excessive element distortions and allows to optimise the element distriviii bution through mesh adaptivity. As a first step towards a continuum-discontinuum approach, an uncoupled damage model is used first, in which damage merely acts as a crack initiation-propagation indicator, without causing material softening. Since uncoupled models do not lead to material localisation, no regularisation is needed. Yet, uncoupled approaches can not capture the actual failure mechanisms and therefore, in general, can give reliable results only when the size of the fracture process zone is so small that its effect can be neglected. When the size of the fracture process zone is large enough, a truly combined model must be used, which is developed in the second part of this study. Due to softening, the transition from the continuous damage material to the discrete crack occurs gradually, with little stress redistribution, in contrast with the previous uncoupled approach. The gradient regularised softening behaviour is introduced in the yield behaviour of an elastoplastic material. The combined model has been applied satisfactorily to the prediction of ductile failure under shear loading conditions. Third, to be able to apply the model to more general loading conditions, the material description has been improved by introducing the influence of stress triaxiality in the damage evolution of a gradient regularised elastoplastic damage model. The model has been obtained using the continuum damage mechanics concept of effective stress. Results show how compressive (tensile) states of triaxiality may increase (decrease) the material ductility. Finally, the combined approach is applied to the modelling of actual metal forming processes, e.g. blanking, fine blanking, score forming. The gradient regularisation has been implemented in an operator-split manner, which can be very appealing for engineering purposes. To capture the large strain gradients in the localisation zones, a new mesh adaptivity criterion has been proposed. The results of the simulations are in good agreement with experimental data from literature

Single-atom control of the optoelectronic response in sub-nanometric cavities

By means of ab-initio time dependent density functional theory calculations carried out on an prototypical hybrid plasmonic device (two metallic nanoparticles bridged by a one-atom junction), we demonstrate the strong interplay between photoinduced excitation of localized surface plasmons and electron transport through the single atom. Such an interplay is remarkably sensitive to the atomic orbitals of the junction. Therefore, we show the possibility of a twofold tuning (plasmonic response and photoinduced current across the juntion) just by changing a single atom in the device.Comment: 5 pages, 5 figure

A coupled problem of heat and mass transfer applied to porous textile media surrounding the human foot

There have been many attempts in the literature to model human thermoregulation systems in order to predict central temperature and other heat stress indicators (see [3, 9], among many others). These models depend on a wide range of variables, including individual characteristics, surrounding textile and environmental factors. The main objective of this work is to formulate a stable, realistic and versatile 2-D mathematical model describing the heat transfer of the human foot (bare foot and foot surrounded by textile materials). The novelty, but also the difficulty , lies on the theoretical multiphysics that models the textile as a porous media, involving energy transport but also mass transport of liquid water, water vapour and gas, including evaporation phenomena. The numerical solution to the global problem involves a segregated algorithm and fixed point techniques for the nonlinearities jointly with finite elements spatial discretizations. Implementation has been performed through commercial software COMSOL TM Multiphysics

Some aspects of lubrication in heavy regimes: thermal effects, stability and turbulence

In this work, a combination of numerical methods applied to thermohydrodynamic lubrication problems with cavitation is presented. It should be emphasized the difficulty of the nonlinear mathematical coupled model involving a free boundary problem, but also the simplicity of the algorithms employed to solve it. So, finite element discretizations for the hydrodynamic and thermal equations combined with upwind techniques for the convection terms and duality methods for nonlinear features are proposed. Additionally, a model describing the movement of the shaft is provided. Considering the shaft as a rigid body this model will consist of an ODE system relating acceleration of the center of gravity and external and pressure loads. The numerical experiments of mechanical stability try to clarify the position of the neutral stability curve. Finally, a rotating machine for ship propulsion involving both axial and radial bearings operating with nonconventional lubricants (seawater to avoid environmental pollution) is analyzed by using laminar and turbulent inertial flows

Datasets for transcriptomics, q-proteomics and phenotype microarrays of polyphosphate metabolism mutants from Escherichia coli

Indexación: Scopus.Author acknowledges Fondecyt Grants 1120209, 1121170 and Anillo ACT-1107Here, we provide the dataset associated with our research article on the polyphosphate metabolism entitled, “Multi-level evaluation of Escherichia coli polyphosphate related mutants using global transcriptomic, proteomic and phenomic analyses”. By integrating different omics levels (transcriptome, proteome and phenome), we were able to study Escherichia coli polyphosphate mutant strains (Δppk1, Δppx, and Δppk1-ppx). We have compiled here all datasets from DNA microarrys, q-proteomic (Isotope-Coded Protein Labeling, ICPL) and phenomic (Phenotype microarray) raw data we have obtained in all polyP metabolism mutants.http://www.sciencedirect.com/science/article/pii/S2352340917300860?via%3Dihu

The New Control and Interlock System for the SPS Main Power Converters

The Control and Interlock System (CIS) of the SPS main power converters was designed in the mid-70s and became increasingly difficult to maintain. A new system based on Programmable Logic Controllers has been developed by an external contractor in close collaboration with CERN. The system is now operational and fully integrated in the SPS/LEP control infrastructure. The CIS is the first major contracted industrial solution used to control accelerator equipment directly involved in the production of particle beams at CERN. This paper gives an overview of the SPS main power converter installation and describes both the contractual and technical solution adopted for the CIS. It first explains how the system was specified and how the contractual relationship was defined to respect CERNs purchasing rules and the operational requirements of the SPS accelerator. The architectural design of the new system is presented with special emphasis on how the conflict between safety and availability has been addressed

Control and interlock system for the SPS main power converters

The control and interlock system of the main power converters was 20 years old and needed to be replaced. In order to face the shrinking resources of CERN, it was decided to adopt, as far as possible, standard industrial solutions and to contract out the development of the new system to industry. A tender was sent to European firms and the contract was awarded to GTD, a Spanish Engineering Firm, in May 1997. The SPS accelerator restarted in March 98 with the new Control and Interlock System

Role of Prolactin in the Recovered T-Cell Development of Early Partially Decapitated Chicken Embryo

Although different experimental approaches have suggested certain regulation of the mammalian immune system by the neuroendocrine system, the precise factors involved in the process are largely unknown. In previous reports, we demonstrated important changes in the thymic development of chickens deprived of the major neuroendocrine centers by the removal of embryonic prosencephalon at 33-38 hr of incubation (DCx embryos) (Herradón et al., 1991; Moreno et al., 1995). In these embryos, there was a stopping of T-cell maturation that resulted in an accumulation of the most immature T-cell subsets (CD4-CD8- cells and CD4-CD81o cells) and, accordingly, in decreased numbers of DP (CD4+CD8+) thymocytes and mature CD3+TcRαβ + cells, but not CD3+TcRγδ lymphocytes. In the present work, we restore the thymic histology as well as the percentage of distinct T-cell subsets of DCx embryos by supplying recombinant chicken prolactin, grafting of embryonic pituitary gland, or making cephalic chick-quail chimeras. The recovery was not, however, whole and the percentage of CD3+TcRαβ thymocytes did not reach the normal values observed in 17-day-old control Sham-DCx embryos. The results are discussed on the basis of a key role for prolactin in chicken T-cell maturation. This hormone could regulate the transition of DN (CD4-CD8-) thymocytes to the DP (CD4+CD8+) cell compartment through its capacity for inducing IL-2 receptor expression on the former

The Key Role Transferring Knowledge of Nuclear España, The Spanish Nuclear Society Magazine

The magazine of the Spanish Nuclear Society (SNE), “Nuclear España” is a scientific-technical publication with almost thirty years of uninterrupted edition and more than 300 numbers published. Their pages approach technical subjects related to the nuclear energy, as well as the activities developed by the SNE, especially in national and international meetings. The main part of the magazine is composed by articles written by known specialist of the energy industry. One of the top goals of the magazine is to help on transferring the knowledge from the generation that built the nuclear power plants in Spain and the new generation of professionals that have started its nuclear career in the last years. Each number is monographic, trying to cover as many aspects on an issue as it is possible, with collaborations from the companies, the research centers and universities that helps to have complementary points of view. On the other hand the articles help to deep in the issue´s topic, broadening the view of the readers about the nuclear field and helping to share knowledge across the industry. The news section of the Magazine picks up the actuality of the sector as a whole. The editorial section reflects the opinion of the SNE Governing Board and the Magazine Committee on the subjects of interest in this field. On the other hand, the monthly interview sets out the professional outstanding opinions. With a total of eleven numbers per year, three of them have a noticeable international character: the one dedicated to the operative experiences on the Spanish and European nuclear power plants, the monographic issue devoted tothe Annual Meeting of the SNE and the international issue, which covers the last activities of the Spanish industry in international projects. Both first are bilingual issues (Spanish-English), whereas the international edition is published completely in English. Besides its diffusion through all the members of the SNE, the Magazine is distributed, in the national scope, to companies and organisms related to the nuclear power, universities, research centers, representatives of the Central, Autonomic and Local Administrations, mass media and communication professionals. It is also sent to the utilities and research centers in Europe, United States, South America and Asia

A systematic overview of dental methods for age assessment in living individuals: from traditional to artificial intelligence-based approaches

Dental radiographies have been used for many decades for estimating the chronological age, with a view to forensic identification, migration flow control, or assessment of dental development, among others. This study aims to analyse the current application of chronological age estimation methods from dental X-ray images in the last 6 years, involving a search for works in the Scopus and PubMed databases. Exclusion criteria were applied to discard off-topic studies and experiments which are not compliant with a minimum quality standard. The studies were grouped according to the applied methodology, the estimation target, and the age cohort used to evaluate the estimation performance. A set of performance metrics was used to ensure good comparability between the different proposed methodologies. A total of 613 unique studies were retrieved, of which 286 were selected according to the inclusion criteria. Notable tendencies to overestimation and underestimation were observed in some manual approaches for numeric age estimation, being especially notable in the case of Demirjian (overestimation) and Cameriere (underestimation). On the other hand, the automatic approaches based on deep learning techniques are scarcer, with only 17 studies published in this regard, but they showed a more balanced behaviour, with no tendency to overestimation or underestimation. From the analysis of the results, it can be concluded that traditional methods have been evaluated in a wide variety of population samples, ensuring good applicability in different ethnicities. On the other hand, fully automated methods were a turning point in terms of performance, cost, and adaptability to new populationsOpen Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. This work has received financial support from Consellería de Cultura, Educación e Ordenación Universitaria (accreditation 2019–2022 ED431G-2019/04 and Group with Growth Potential ED431B 2020–2022 GPC2020/27) and the European Regional Development Fund (ERDF), which acknowledges the CiTIUS-Research Center in Intelligent Technologies of the University of Santiago de Compostela as a Research Center of the Galician University SystemS