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- Acrylic adhesives in the polyolefins joiningPublication . Pinto, A. M. G.; Magalhães, A. G.; Silva, Francisco J. G.; Baptista, A. P. M.The mechanical behaviour of single lap adhesive joints was characterized, using two commercial acrylic adhesives. For this purpose the surfaces were cleaned and abraded using fine grit abrasives. The effect of temperature and moisture in the mechanical strength was, also, evaluated. For this characterization, mechanical tests were carried out according procedure and geometry foreseen by ASTM D3163-01 [1] and ASTM D4501-01 [2] standards. The results show that it is possible to get good strengths without great surface preparation. The temperature and moisture effect observed don’t seem to be relevant for the mechanical behaviour.
- Adaptations of a resources system selection problem of Distributed/Agile/Virtual Enterprises for using genetic algorithmsPublication . Ávila, Paulo; Mota, Alzira; Putnik, Goran; Costa, LinoThe selection of resource systems is still a difficult matter to solve in distributed / Agile / Virtual enterprises ( D/A/V Es ) integration. Attempts to solve the resources selection problem, has originated several models and consequently different algorithms have been applied to obtain solutions. The exact algorithms have good performance (in terms of computational time) for low dimension problems. However, become ineffective as the complexity increases. Genetic algorithms are considered robust and versatile. These have been applied to complex problems in several application areas and gained popularity in innumerable research works. To improve the computational time in solving the resources selection problem, we pretend to apply a genetic algorithm. Due to the characteristics of the model, the application of this algorithm forced adjustments in the initial model. In this work, we present the adaptations performed in the study model in order to use genetic algorithms.
- Adhesion and wear behaviour of NCD coatings on Si3N4 by micro-abrasion testsPublication . Silva, Francisco J. G.; Neto, M. A.; Fernandes, A. J. S.; Costa, F. M.; Oliveira, F. J.; Silva, R. F.Nanocrystalline diamond (NCD) coatings offer an excellent alternative for tribological applications, preserving most of the intrinsic mechanical properties of polycrystalline CVD diamond and adding to it an extreme surface smoothness. Silicon nitride (Si3N4) ceramics are reported to guarantee high adhesion levels to CVD microcrystalline diamond coatings, but the NCD adhesion to Si3N4 is not yet well established. Micro-abrasion tests are appropriate for evaluating the abrasive wear resistance of a given surface, but they also provide information on thin film/substrate interfacial resistance, i.e., film adhesion. In this study, a comparison is made between the behaviour of NCD films deposited by hot-filament chemical vapour deposition (HFCVD) and microwave plasma assisted chemical vapour deposition (MPCVD) techniques. Silicon nitride (Si3N4) ceramic discs were selected as substrates. The NCD depositions by HFCVD and MPCVD were carried out using H2–CH4 and H2–CH4–N2 gas mixtures, respectively. An adequate set of growth parameters was chosen for each CVD technique, resulting in NCD films having a final thickness of 5 m. A micro-abrasion tribometer was used, with 3 m diamond grit as the abrasive slurry element. Experiments were carried out at a constant rotational speed (80 r.p.m.) and by varying the applied load in the range of 0.25–0.75 N. The wear rate for MPCVD NCD (3.7±0.8 × 10−5 m3N−1m−1) is compatible with those reported for microcrystalline CVD diamond. The HFCVD films displayed poorer adhesion to the Si3N4 ceramic substrates than the MPCVD ones. However, the HFCVD films show better wear resistance as a result of their higher crystallinity according to the UV Raman data, despite evidencing premature adhesion failure.
- Adhesively-bonded repair proposal for wood members damaged by horizontal shear using carbon-epoxy patchesPublication . Campilho, Raul; Moura, M. F. S. F. de; Ramantani, Dimitra A.; Morais, J. J. L.; Barreto, A. M. J. P.; Domingues, J. J. M. S.In this work, a repair technique with adhesively bonded carbon-epoxy patches is proposed for wood members damaged by horizontal shear and under bending loads. This damage is characterized by horizontal crack growth near the neutral plane of the wood beam, normally originating from checks and shakes. The repair consists of adhesively bonded carbon-epoxy patches on the vertical side faces of the beam at the cracked region to block sliding between the beam arms. An experimental and numerical parametric analysis was performed on the patch length. The numerical analysis used the finite element method (FEM) and cohesive zone models (CZMs), with an inverse modelling technique for the characterization of the adhesive layer. Trapezoidal cohesive laws in each pure mode were used to account for the ductility of the adhesive used. To fully reproduce the tests, horizontal damage propagation within the wood beam was also simulated. A good correlation with the experiments was found. Regarding the effectiveness of the repair, for the conditions selected for this work, a full strength recovery was achieved for the bigger value of patch length tested.
- Advanced techniques for estimation of the tensile fracture toughness of adhesive jointsPublication . Campilho, R.D.S.G.; Banea, M.D.; da Silva, L.F.M.Adhesive bonding has become more efficient in the last few decades due to the adhesives developments, granting higher strength and ductility. As a result, adhesives are being increasingly used in industries such as the automotive, aerospace and construction. Thus, it is highly important to predict the strength of bonded joints to assess the feasibility of joining during the fabrication process of components (e.g. due to complex geometries) or for repairing purposes. When using the Finite Element Method with advanced propagation laws, the tensile (Gnc) and shear (Gsc) fracture toughness of adhesive joints must be determined with accuracy. Several conventional methods to obtain Gnc and Gsc exist in the literature, mainly based on Linear Elastic Fracture Mechanics (LEFM). The J-integral technique is accurate to measure these parameters for adhesives with high ductility. In this work, the J-integral is used to obtain Gnc by the Double-Cantilever Beam (DCB) test. An optical measurement method is developed for the evaluation of the crack tip opening and adherends rotation at the crack tip during the test, supported by a Matlab® sub-routine for the automated extraction of these quantities. As output of this work, an optical method that allows an easier and quicker extraction of the parameters to obtain Gnc than the available methods is proposed (by the J-integral technique) and some results are presented regarding joints with different geometry and adherend material.
- Advanced Thermoplastic Carbon Fibre Reinforced Pultruded CompositesPublication . Novo, P. J.; Silva, João; Nunes, J. P.; Marques, A. T.The aim of this work is to optimize the production of new continuous carbon fibers reinforced thermoplastic matrix pre-impregnated materials (towpregs) continuously processed by dry deposition of polymer powders in a new equipment developed by the Institute for Polymers and Composites (IPC). The processing of the produced towpregs by pultrusion, in a developed prototype equipment existing in the Engineering School of the Polytechnic Institute of Porto (ISEP), was also optimized. Two different thermoplastic matrices were studied: one for commercial applications (polypropylene) and another for advanced markets (Primospire®). The optimization was made by studying the influence of the most relevant processing parameters in the final properties of the produced towpregs and composites. The final pultruded composite profiles were submitted to mechanical tests in order to obtain relevant properties.
- Agile Project Management: A Communicational Workflow ProposalPublication . Loiro, Carina; Castro, Helio; Ávila, Paulo; Cruz-Cunha, Maria Manuela; Putnik, Goran D.; Ferreira, LuísEmbracing agility brings change to companies and everyone involved, so people have a fundamental role in project development. It is essential that teams have a good communication, motivation and concern about quality and client satisfaction, Agile Manufacturing is using Agile Project Management to provide the right team to performance difficult tasks and achieve goals. This paper proposes a team that deals with Agile Project Management, named as AGILE team, composed by a product owner, a team leader and team members, and a communication workflow proposal concerning the conjunction of 3 momentums (requirements analyze, planning and design) along the Agile Project Management. The proposed model is being implemented in a lightening manufacturing company in a very early stage.
- An algorithm of a costing system for electroplatingPublication . Pires, António; Ferreira, Fábio; Ávila, Paulo; Mota, AlziraBusinesses are increasingly competitive and rigorous and it is essential the existence of a strong, effective and realistic costing system. Decisions taken on the basis of the costing are very important, they can make the difference between success and failure of the organization. This paper explains the construction of an initial algorithm that aims to calculate the costs associated with electroplating of metal articles, in a specific company. This work can act as a possible guide for the construction of the costing system algorithms in this type of industry.
- An analysis about the resources selection process in agile/virtual enterprisesPublication . Pires, António; Putnik, Goran; Ávila, PauloWe intend in the context of this work, to do an analysis on studies, literary revisions and mainly on existent models, in the universe of virtual enterprises resources selection, in order to allow us to put on perspective, in a sustainable way, new slopes to be incorporated that contributes to an improvement of the whole global process. This analysis for the A/VE was focused in several areas and basic slopes for the whole global process of the problem in question, namely in terms of the pre-selection phases and requisites; selection phases, requisites and methods; mathematical models, used tools and other important areas. There were incorporated the decision process of create an A/VE project and the requisites of the process principal phases. We approach the essential aspects for the work that is intended to develop, such as the integration of the existent models with the tasks plan (PT) of the product, namely if there are contemplated the eformulation and evaluation of the PT, and other important characteristics such as the weighting of resources and the incorporation of the value concept in the existent models, being that in our opinion an integration of a methodology of the type of Value Analysis will be able to incorporate surplus values in all this process. Conclusions were withdrawn on the whole global process, pointing to gaps and limitations and trying to do an approach which allows to sinthetize and put in perspective an efficient analysis of the whole extent of the problem in question.
- An Approach About the Value Analysis MethodologyPublication . Pires, António; Ávila, PauloThe markets globalization requires enterprises to continually investing in innovation, competitiveness and excellence. It is important to create a value culture in organizations, through methods such as Value Analysis (VA). We pretend to enhance the relevance of the value concept and the creation of a value culture in the organizations, in order to foment and increment their success. In this paper we intend to provide a better knowledge of value analysis and suggest possible ways of its application. These allow us to put on perspective in a sustainable way new slopes to be incorporated that contributes to increase surplus values in the enterprises.