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Guimarães, Portugal

Vieira G.G.,Azurem Campus | Viveiros A.,Azurem Campus | Machado J.,University of Minho
Romanian Review Precision Mechanics, Optics and Mechatronics | Year: 2015

Many different approaches have been proposed for improving energy network management. Although these diverse contributions, most approaches for clearly identifying and accurately solving the real problems remain rather inefficient. This is greatly due to the absence of use of completely integrated and sustainable models with Organizations playing fundamental rolls through the use of effective and efficient decision support tools. One such typical problem is related to the accurate identification and the precise calculation of electrical energy losses, which still remains unsolved as well as the clear specification of the critical points and segments in the networks were problems do occur. Consequently, there is still a lack of effective prioritization of actions and interventions in order to reduce those problems. Therefore, in this paper we propose a model for sustainable energy network management were the organizational element assumes a crucial function. © 2015, Editura Cefin. All rights reserved. Source


Dourado M.D.M.,Azurem Campus | de Meireles J.F.B.,Azurem Campus
Advanced Materials Research | Year: 2014

This paper proposes a simplified finite element model to represent a riveted lap joint in structural dynamic analysis field. The rivet is modeled by spring-damper elements. Several numerical models are studied with different quantities of rivets (1, 3 and 5) and spring-damper elements (4, 6, 8, 12, 16 and 20) per rivet. In parallel, samples of two aluminum material plates connected by different quantities of rivets (1, 3 and 5) are built and tested in order to be known its modal characteristics - natural frequencies and mode shapes. The purpose of the different settings is to get the best numerical riveted lap joint representation relatively to the experimental one. For this purpose a finite element model updating methodology is used. An evaluation of the best numerical riveted lap joint is carried out based on comparisons between the numerical model after updating and the experimental one. It is shown that the riveted lap joints composed by eight and twelve spring-damper elements per rivet have the best representation. A stiffness constant value k is obtained for the riveted lap joints in study. © (2014) Trans Tech Publications, Switzerland. Source


Dourado M.,Azurem Campus | Soares D.,Azurem Campus | Barbosa J.,Azurem Campus | Marques Pinho A.,Azurem Campus | And 4 more authors.
Materials Science and Engineering A | Year: 2014

Fatigue is one of the main causes of failure of structures and mechanical components, occurring due to the progressive weakening of their strength that reduces significantly their lifetime, when subjected to cyclic stresses over time. In welded components, the joints are the zones most susceptible to crack by fatigue.Therefore, the base of this study are the Metal Inert Gas/Metal Active Gas (MIG/MAG) and LASER welding manufacturing processes, focused in three main areas involved in an automotive metallic system under dynamic loads: Fatigue testing in order to prevent structural collapse; Heat Affected Zones (HAZ) characterization to evaluate the material properties modification originated by those different technologies; Reliability analysis in order to analyse the performance of the samples and to select the best connection in terms of product life cycle. For this purpose, samples representative of industrial automotive applications (long welds) have been selected to carry out this work. Two types of connected specimens were manufactured, consisting of two steel plates of different thicknesses, overlapping and welded by the MAG process (type A) or the Laser process (type B). Metallographic characterization was performed for both typologies, namely macrostructural and microstructural characterization of the weld joint, and respective HAZ. Mechanical properties were inferred by measuring and mapping microhardness variation on the neighbour of the weld joint. Fatigue tests were carried out for specimens type A and type B, using 15 samples of each type that were tested under 3 levels of stress amplitude. The samples manufactured by the Laser process show better fatigue behaviour when compared to the samples manufactured by MAG welding. The better weld joint solution is proposed in accordance with the reliability analysis of the obtained fatigue test results. © 2014 Elsevier B.V. Source

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