Analysis and modelization of lightweight structures subjected to impact

Mechanics of Advanced Materials research group (Department of Continuum Mechanics and Structural Analysis) of the University Carlos III of Madrid (Spain) offers their experience in the analysis and modelization of high and low velocity impact behaviour of composite structures. Their research focuses on both numerical analysis and non-standard experimental methodologies)

Participation and spirit : an interview with Jorge N. Ferrer

This interview with Jorge Ferrer explores a wide number of themes, ranging from his psychology studies at the University of Barcelona and the roots of his interest in transpersonal psychology to his arrival to San Francisco and first years at the California Institute of Integral Studies (CIIS) as a doctoral student. Topics discussed include his dissertation research, the publication of his first book 'Revisioning Transpersonal Theory' (SUNY Press, 2002), the participatory turn in transpersonal psychology, his first publications in the 'Journal of Transpersonal Psychology' and debate with Ken Wilber, and the development of the participatory paradigm in more recent years. Finally, Ferrer highlights what he considers to be the main issues and debates within transpersonal psychology, as well as shares his main current interests and future projectsEsta entrevista con Jorge Ferrer explora un amplio abanico de temas, comenzando por sus estudios de licenciatura en psicología en la Universidad de Barcelona, las raíces de su interés por la psicología transpersonal, su llegada a San Francisco y sus primeros años en el CIIS y la ―Bay Area‖ como estudiante de doctorado. Los temas tratados incluyen su trabajo de tesis, la publicación de su primer libro 'Espiritualidad creativa', el giro participativo dentro de la psicología transpersonal, sus primeras publicaciones en el 'Journal of Transpersonal Psychology' y su debate con Ken Wilber, así como el desarrollo del paradigma participativo a lo largo de los últimos años. Finalmente, Ferrer destaca cuales considera que son los principales asuntos y debates en el campo de la psicología transpersonal actualmente, sus intereses principales y sus proyectos futuro

An analytical model for high velocity impacts on thin CFRPs woven laminated plates

15 pages, 12 figures.-- MSC2000 codes: Primary: 74R15; Secondary: 74M20, 74E30, 74K20, 74-05.Zbl#: Zbl 1178.74147An analytical model to study the impact process of a spherical projectile penetrating at high velocity into a carbon/epoxy plain woven laminate is developed in this work. The model is based on an energy balance, where the kinetic energy of the projectile is absorbed by the laminate by three different mechanisms: laminate crushing, linear momentum transfer and tensile fiber failure. A non-homogeneous differential equation is obtained. A subsequent simplification using regular perturbation analysis gives a closed-form solution that allows the approximative calculation of the residual velocity and hence the ballistic limit. The model is validated with the results of experimental tests in which the residual velocity is measured by means of high speed cameras.The authors are indebted to the Comisión Interministerial de Ciencia y Tecnología of Spain for the financial support of this work (Project MAT98-0273).Publicad

Effect of intrinsic defects on the thermal conductivity of PbTe from classical molecular dynamics simulations

Despite being the archetypal thermoelectric material, still today some of the most exciting advances in the efficiency of these materials are being achieved by tuning the properties of PbTe. Its inherently low lattice thermal conductivity can be lowered to its fundamental limit by designing a structure capable of scattering phonons over a wide range of length scales. Intrinsic defects, such as vacancies or grain boundaries, can and do play the role of these scattering sites. Here we assess the effect of these defects by means of molecular dynamics simulations. For this we purposely parametrize a Buckingham potential that provides an excellent description of the thermal conductivity of this material over a wide temperature range. Our results show that intrinsic point defects and grain boundaries can reduce the lattice conductivity of PbTe down to a quarter of its bulk value. By studying the size dependence we also show that typical defect concentrations and grain sizes realized in experiments normally correspond to the bulk lattice conductivity of pristine PbTe

Fast local search for fuzzy job shop scheduling

In the sequel, we propose a new neighbourhood structure for local search for the fuzzy job shop scheduling problem. This is a variant of the well-known job shop problem, with uncertainty in task durations modelled using fuzzy numbers and where the goal is to minimise the expected makespan of the resulting schedule. The new neighbourhood structure is based in changing the relative order of subsequences of tasks within critical blocks. We study its theoretical properties and provide a makespan estimate which allows to select only feasible neighbours while covering a greater portion of the search space than a previous neighbourhood from the literature. Despite its larger search domain, experimental results show that this new structure notably reduces the computational load of local search with respect to the previous neighbourhood while maintaining or even improving solution quality

Análisis técnico – económico de mezclas asfálticas con tereftalato de polietileno reciclado para la construcción de carreteras asfaltadas

La presente investigación tuvo como problema general: ¿Cuál es el resultado del análisis técnico – económico de mezclas asfálticas con tereftalato de polietileno reciclado para la construcción de carreteras asfaltadas?, el objetivo general fue: Analizar técnica y económicamente a las mezclas asfálticas con tereftalato de polietileno reciclado para la construcción de carreteras asfaltadas y la hipótesis general que se verificó fue: Del análisis técnico – económico de mezclas asfálticas con tereftalato de polietileno reciclado, se tiene que éste mejora el desempeño estructural y la durabilidad, además de no variar significativamente el costo para la construcción de carreteras asfaltadas. El método general de investigación fue el científico, el tipo de investigación fue aplicada de nivel correlacional y el diseño fue experimental. La población correspondió a 100 especímenes de mezcla asfáltica convencional y modificada con escamas PET de botellas de plástico; para la muestra no se aplicó técnica de muestreo pues comprendió a la totalidad de la población. Como conclusión principal se obtuvo que, del análisis técnico – económico de mezclas asfálticas en caliente con tereftalato de polietileno reciclado, se tiene que este incide positivamente en el desempeño estructural y durabilidad, además de no variar significativamente el costo para la construcción de carreteras asfaltadas; bajo un contenido óptimo de 1 % de escamas PET en relación al agregado fino.Tesi

Localization Method for Autonomous Vehicles by using Vertical Elements in the Environment

The goal of this work is to provide autonomous cars with an alternative method to estimate their position in the world. It focuses on those situations when the GPS signal gets imprecise, weak or even lost due to environment conditions (long tunnels, dense forests, high buildings around, etc.). By installing two Velodyne VLP-16 LiDAR devices on the top of the car, located on both front corners of the vehicle structure, it is possible to acquire a 3D representation of this environment as a point cloud. This point cloud will be analyzed in order to find thin, vertical elements, such as traffic signals, traffic lights and so on. If these elements have been previously georeferenced, this is, their coordinates have been acquired and saved, the method will try to compare and match the incoming information from the environment to the georeferenced objects, i.e., performing data association. If the detected elements match any of the georeferenced ones, the car will correct an estimate of its position in a global frame.RoboCity2030-DIH-CM, Madrid Robotics Digital Innovation Hub, S2018/NMT-4331, funded by R&D Activities Program in Comunidad de Madrid and cofunded by EU Structural Funds.Peer reviewe

The effect of low temperatures on the intermediate and high velocity impact response of CFRPs

8 pages, 13 figures.The influence of low temperature on the damage produced on CFRPs by intermediate and high velocity impacts is analyzed. Spherical projectiles were launched against different carbon fiber/epoxy laminates (tape and woven). Experimental tests were done at temperatures ranging from 25 to −150 °C. The extension of the damage was measured by C-Scan. Results show a clear dependence of damage on temperature, impact velocity and the type of the laminate.The authors are indebted to the Comisión Interministerial de Ciencia y Tecnología of Spain for financial support of this work (Project MAT98-0273). They also thank EADSCASA for assistance in C-Scan measurements.Publicad

Prediction of the behaviour of CFRPs against high-velocity impact of solids employing an artificial neural network methodology

8 pages, 9 figures.A new methodology based on artificial neural networks has been developed to study the high velocity oblique impact of spheres into CFRP laminates. One multilayer perceptron (MLP) is employed to predict the occurrence of perforation of the laminate and a second MLP predicts the residual velocity, the obliquity of trajectory of the sphere after perforation and the damage extension in the laminate. In order to train and test the networks, multiple impact cases have been generated by finite-element numerical simulation covering different impact angles and impact velocities of the sphere for a given system sphere/laminate.Publicad

Experimental analysis of fluid-filled aluminium tubes subjected to high-velocity impact

11 pages, 20 figures.Hydrodynamic ram (HRAM) is a phenomenon that occurs when a high-energy object penetrates a fluid-filled container. The projectile transfers its momentum and kinetic energy through the fluid to the surrounding structure increasing the risk of catastrophic failure and excessive structural damage. It is of particular concern in the design of wing fuel tanks for aircraft since it has been identified as one of the important factors in aircraft vulnerability. For the present work, water-filled aluminium square tubes (6063-T5) were subjected to impact by steel spherical projectiles (12.5 mm diameter) at impact velocities of 600–900 m/s. The aluminium tubes were filled at different volumes to study how an air layer inside the tank might influence the impact behaviour. The test boxes were instrumented with five strain gauges and two pressure transducers. The formation process of the cavity was recorded with a high-speed camera. This work presents the results of these tests.This research was done with the financial support of the Spanish Ministry of Education under Project reference DPI2005-06769, and of the University Carlos III of Madrid and Comunidad Autónoma de Madrid under project reference CCG07-UC3M/DPI-3395.Publicad