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Reuse in safety critical systems : educational use case first experiences
Get PDFIn order to maintain Europe as world leader in development of safety relevant systems one of the keys would be to join together the European industrial, academic and scientific communities. One of the main industrial challenges is that any company that wants to compete in the safety-related embedded systems market and have success in business, have to develop competent systems reducing the time to market and the cost of the development and certification. The reusability of SW components is one of the solutions in this way. The technical aspects are worked out in the ARTEMIS nSafeCer project and industrial, academic and scientific communities are working together generating new methods and tools and applying them in use cases. One of the use cases of the project is an educational one and the University of Mondragon is developing it in order to use it in the Master of Embedded Systems Courses with the objective to transfer the knowledge about how to develop safety critical and certifiable systems in an efficient way
Finite element modeling of fretting wear scars in the thin steel wires : Application in crossed cylinder arrangements
Get PDFThis paper completes a series of two papers in which a FE based methodology for the prediction wear scars in thin steel wires under fretting wear conditions is developed. In the first paper ‘Finite element modeling and experimental validation of fretting wear scars in thin steel wires’ a FE fretting wear simulation model for a common 90° crossed cylinder tribological arrangements was developed and validated. The second paper deals with modeling accurately the elliptical wear scars presented in wire rope systems, in contrast with the simpler circular wear scars presented in the 90° crossed cylinder configuration. The main parameters involved in the wear simulation (mesh size, simulation wear increments per fretting cycle and cycle jump ΔN) are calibrated to obtain the minimum computational time. An exhaustive validation methodology for elliptical wear scars is presented. The proposed model presents very good correlation with respect to the experimental results, predicting wear scars with errors less than 15%. This FE model is presented as a helpful tool for the wire rope designers in the analysis of the severity of the wear scars under different operational and constructive parameters, so that, due to the complex construction of wire ropes, the wires contact between them with different crossing angles
Evolution of residual stresses induced by machining in a Nickel based alloy under static loading at room temperature
Get PDFTensile residual stresses are very often generated on the surface when machining nickel alloys. In order to determine their influence on the final mechanical behaviour of the component residual stress stability should be considered. In the present work the evolution of residual stresses induced by machining in Inconel 718 under static loading at room temperature has been studied. An Inconel 718 disc has been face turned and specimens for tensile tests have been extracted from the disc. Then surface residual stresses have been measured by X-ray diffraction for initial state and different loading levels. Finally, a finite element model has been fitted to experimental results and the study has been extended for more loading conditions. For the studied case, it has been observed that tensile residual stresses remain stable when applying elastic loads but they increase at higher loads close to the yield stress of the material
Lanki kuadernoak = Cuadernos Lanki ; 8
No full textLos impulsores de este trabajo hemos querido acercarnos al eje sobre el que gira cualquier experiencia autogestionada y comunitaria. Por un lado, esta publicación fija la mirada en los dos actores principales que determinan cualquier experiencia de autogestión: la persona y el grupo. El sujeto y la comunidad. Por otro lado, también señala otros factores que condicionan estos procesos: el tipo de liderazgo, la cultura y los ambientes que propician la autoconfianza y la importancia de las utopías.
Las preguntas que han estado en el origen de este ensayo han sido:
¿Por qué la búsqueda del equilibrio entre el sujeto y la comunidad es una buena propuesta?
¿Se puede sostener que el sujeto crece y se hace en comunidad, y viceversa?
El paradigma de personas y comunidades que se autogestionan y cooperan, ¿es una guía interesante para abordar los desafíos de este nuevo ciclo histórico?
¿Existen en la historia de este país elementos que nos permitan afirmar que contamos con una cultura marcada por experiencias de auto-gobernanza y de auto-organización? ¿Podrían servir de inspiración?
Para ello hemos acudido al doctor y profesor Rafael Cristóbal; una persona que
aglutina la sabiduría precisa para centrar esta primera aproximación al tema
Radial fan simulations by computational fluid dynamics and experimental validation
Get PDFFans are commonly used to refrigerate electrical machines when air forced cooling is required. They are rather simple solutions that can considerably improve the thermal performance of electrical machines, so the fan analysis could become an important point during the thermal design of electrical machines. This paper presents an analysis by computational fluid dynamics (CFD) simulations with the goal of characterizing radial fans, used in electrical machines. Different boundary conditions and parameters that affect to CFD results are evaluated in order to get an efficient way to simulate radial fans. The main objective is to obtain the flow-pressure characteristic curve of fans and airflow velocities by CFD simulations. Finally CFD simulation results of 2 fans are experimentally validated. One of them has been analysed in a fan testing wind tunnel. And the second one has been analysed in an auto-ventilated machine
Application of a maintenance management system based on a tailored RCM
Get PDFThis paper presents the results of the application of an adapted version of the RCM (Reliability Centered Maintenance) methodology. Through its implementation, three companies of distinct industrial sectors have been capable of establishing customized preventive maintenance program, having done contributions to the autonomous maintenance. Thus, the workload of the maintenance staff has been reduced without altering equipment unavailability. The work has been also useful to establish the bases for the implementation or the improvement of a computerized maintenance management system.En este artículo se presenta el resultado de la aplicación de una versión adaptada de la metodología RCM (Reliability Centered Maintenance), mediante la cual tres empresas de distintos sectores han podido establecer un programa de mantenimiento preventivo a medida de cada caso, realizando aportaciones al mantenimiento autónomo. De esta manera han conseguido reducir la carga de trabajo de mantenimiento sin reducir la disponibilidad de las instalaciones. El trabajo realizado ha servido a dichas empresas para poder establecer las bases de la implementación o mejora de un programa de gestión del mantenimiento asistido por ordenador
Evolution of Surface Roughness in Grinding and its Relationship with the Dressing Parameters and the Radial Wear
Get PDFGrinding is a machining process specially indicated for finishing operations in hard materials, in order to obtain low surface roughness (Ra 0.1 μm to 2μm) and tight tolerances. The cutting tool is the grinding wheel which is formed by abrasive particles attached in a bond. The wear of these abrasive particles modifies significantly the roughness obtained in the workpiece. In this work, the evolution of part roughness has been continuously monitored as the grinding process progresses and the wheel gets worn. The roughness evolution is then related to different process variables such as the dressing parameters, the grinding conditions, the grinding forces and the radial wear of the wheel
User behavior shift detection in ambient assisted living environments
Get PDFIdentifying users' frequent behaviors is considered a key step to achieving real, intelligent environments that support people in their daily lives. These patterns can be used in many different applications. An algorithm that compares current behaviors of users with previously discovered frequent behaviors has been developed. In addition, it identifies the differences between both behaviors. Identified shifts can be used not only to adapt frequent behaviors, but also shifts may indicate initial signs of some diseases linked to behavioral modifications, such as depression or Alzheimer’s. The algorithm was validated using datasets collected from smart apartments where five different ADLs (Activities of Daily Living) were recognized. It was able to identify all shifts from frequent behaviors, as well as identifying necessary modifications in all cases
Thermal test procedure and analytical model calibration method for electrical machines
Get PDFIn this paper a thermal test procedure and a calibration method for lumped parameter models are presented. Analytical models provide fast thermal simulations in comparison with finite element methods (FEM) and computed fluid dynamics (CFD) simulations. Motor-CAD is a useful and easy configurable tool to simulate motor models, but the quantity of construction parameters makes difficult the calibration process of a model. This paper provides a thermal test process to test machines to calibrate analytical models. And the procedure to estimate temperatures and calculate their uncertainties is exposed. Also a calibration method is proposed to identify critical parameters on analytical models that determine thermal behaviour of the machine. Specific thermal test are designed in order to calibrate these critical parameters like the base in the test bench. Finally the calibration process is validated with 3 different but similar machines. The same analytic model with only construction differences satisfies experimental thermal tests of 3 machines
OPTIBODY: A New Structural Design Focused in Safety
Get PDFWith electric vehicles becoming more and more popular, the classic “general purpose” vehicle concept is changing to a “dedicated vehicle” concept. Light trucks for goods delivery in cities are one of the examples. The European vehicle category L7e fits perfectly in the low power, low weight vehicle requirements for an electric light truck for goods delivery. However, the safety requirements of this vehicle category are very low and their occupants are highly exposed to injuries in the event of a collision. The European Commission co-funded project OPTIBODY (Optimized Structural components and add-ons to improve passive safety in new Electric Light Trucks and Vans) is developing a new structural concept based on a chassis, a cabin a several add-ons. The add-ons will provide improved protection in case of frontal, side and rear impact. Two mains issues also considered in both the chassis and the add-ons design were the crash compatibility and the interaction with the vulnerable road users.
The OPTIBODY project has proposed frontal, side, rear and pedestrian impact tests for improving self and partner protection for this vehicle category. The OPTIBODY vehicle has been designed using this test proposal as targets and the frontal crash test simulations showed an improvement in the cabin integrity and self and partner protection. This vehicle design will provide a new modular architecture for L7e vehicles that will improve self and partner protection and reparability in case of collision