Repositório RCAAP

The aim of this work is to produce and optimize the processing of carbon fibres thermoplastic matrix pre-impregnated materials (towpregs and PCT´s) using the dry powder coating equipment from our own laboratories. Pultrusion was the selected manufacturing method for processing all carbon fibres thermoplastic matrix pre-impregnated materials into composite parts. The optimization of the pultrusion processe was made by studying the influence of the most relevant processing parameters in the final properties of the produced carbon fibres thermoplastic matrix pre-impregnated materials and composites. The composite relevant mechanical properties were determined and studied. The final composites were also submitted to Scanning Electron Microscopy (SEM), optical microscopy and calcination tests. The determination of the fiber volume fraction of a composite with a high melting temperature thermoplastic polymer used as matrix was obtained comparing the results of thermogravimetric analysis (TGA) with the calcination tests.

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.

A presente invenção tem aplicação direta na indústria corticeira e refere-se a Um processo de aglomeração de granulados de cortiça, provenientes de falcas, sem Recurso à adição de aglutinantes. São obtidas formas complexas, em série, utilizando Moldes que permitem conceber a forma final sem necessidade de qualquer operação de Acabamento, ou procedimentos adicionais de desbaste.os seus campos de aplicação são Variados, considerando as diversas utilizações dos aglomerados de cortiça. Contudo, a Maior parcela deverá corresponder a:- decoração ¿ peças decorativas de formas Complexas; - isolamentos ¿ peças de pequena e média dimensão para automóveis, indústria Aeroespacial, mecanismos de refrigeração ou caldeiraria.tendo em conta que o estado da Arte atual caracteriza-se pela aglomeração prévia em formas simples com posterior Maquinação na forma final pretendida, a obtenção de peças complexas recorrendo a um Procedimento com menor número de etapas e sem geração de desperdício, constitui a Grande evolução deste processo.

This paper presents a new and efficient methodology for distribution network reconfiguration integrated with optimal power flow (OPF) based on a Benders decomposition approach. The objective minimizes power losses, balancing load among feeders and subject to constraints: capacity limit of branches, minimum and maximum power limits of substations or distributed generators, minimum deviation of bus voltages and radial optimal operation of networks. The Generalized Benders decomposition algorithm is applied to solve the problem. The formulation can be embedded under two stages; the first one is the Master problem and is formulated as a mixed integer non-linear programming problem. This stage determines the radial topology of the distribution network. The second stage is the Slave problem and is formulated as a non-linear programming problem. This stage is used to determine the feasibility of the Master problem solution by means of an OPF and provides information to formulate the linear Benders cuts that connect both problems. The model is programmed in GAMS. The effectiveness of the proposal is demonstrated through two examples extracted from the literature.

Composite materials have a wide range of application in various domains. The fact behind using composite materials is that they give the same almost strength as metal parts in presenting lesser weight. However, the plastic parts are non-biodegradable, and they lead to the polluted environment during the disposal after end-of-life of a particular part. Nowadays natural and easily recyclable composites were preferred due to environmental concerns. The major disadvantage of using natural fibre composites is that they have low strength compared to conventional glass or carbon reinforced composite. To enhance the strength of Natural-Fiber-Reinforced Plastics (NFRP) various techniques have been followed (Chemical treatment of the fibre, post-curing of the composites, sandwiching the composite, adding additives/fillers to the matrix) based on the feasibility and application of the composites. Among those techniques, adding additives to the matrix is one of the simple and effective ways to enhance the properties of the composite. A natural additive is developed in concern to the environmental impact of the composite. Two different types of the composite laminate were manufactured. One is with additive and one is without the additive. It is necessary to validate the strength of the composite with and without the additives by mechanical testing. Thus, tensile, flexural and moisture absorption tests were performed to verify the mechanical property enhancement achieved due to the use of additives. These tests help in characterizing the material to specific applications. The composite with the natural additive showed better mechanical properties. However, the moisture absorption tendency of the composite is increased as well, mainly due to the presence of additives on the surface of the composite along with the matrix.

One of the main problems with laser cutting equipment is related to the wrong setting of cutting parameters. The mismatching of these parameters leads to a loss of cut surface quality, which is hardly re-established. This loss of quality is usually related to a burr problem. Thus, this study is aimed to improve and optimize this process using a fibre laser equipment. Three important laser cutting parameters were studied in order to investigate their importance in the cut surface quality: radiation power, cutting speed and gas pressure. The different values were performed cutting a stainless steel AISI 316L and a cold rolled steel St12. Metallographic and cut surface analysis, burr and roughness measurements were carried out, supported by a Scanning Electron Microscopy and profilometry. Through the Taguchi statistical analysis model, it is possible to indicate the best set of laser cutting parameters. It was verified that the values recommended by the equipment manufacturer can be optimized, being possible to use less radiation power in the laser beam with greater speed of cut, providing a better cut surface quality, improving and optimizing the entire process.

Maintenance function assumes a key role in today’s industry. The automotive industry is not an exception and there are strict rules to comply with. Indeed, the IATF 16949:2016 imposes the implementation of key performance indicator as a mean to control the overall manufacturing performance. This work presents a case study carried out in a multinational company related with the production of parts for the automotive industry where it was necessary to implement key performance indicators to comply with the IATF 16949: 2016 standard and a model was also created for the management of spare parts linked to the maintenance of existing equipment. The introduction of these changes forced the application of some Lean tools, with a view to improving procedures and information flows. The work was completed successfully, and key performance indicators were implemented, whose support data, which is now collected and calculated automatically on a routine basis, and the spare-parts management was validated with a view to optimization of warehouse space and at a conveniently low inventory level in this type of parts, without endangering critical equipment in production. The SMED methodology was applied, which allowed the setup time to be reduced by 11%, and the Lean 5S tool was used to organize the mould exchange activities. An OEE of more than 90% has been achieved.

This paper is a study in Reverse Logistics (RL) that aims to analyse the reverse flow of medications with expired dates, in the pharmacies of the Campania region in Italy. The main objective is to analyse the final destination of medications that are not sold and are collected in pharmacies. The analysis of how the company responsible for the collection of the medications works was made using semi-structured interviews, and a subsequent factor analysis of the collected data. The pharmacies of the main cities of this region were investigated, in order to understand their importance in this process, as well as to understand their main difficulties and challenges. A statistical analysis of the data allowed us to verify how pharmacies are accustomed to the current legislation and are aware of the importance of their role in the RL of the medications that are not sold due to expired date. It was observed that pharmacies are very satisfied with the company responsible for the collection and referral of medications and their materials to an adequate final destination. Both of them work in tune, respond well to current legislation and respect the environment.

Additive Manufacturing (AM) is a term used to group the different manufacturing processes that use various techniques, each of which is capable of producing parts made from a wide variety of materials, such as polymers, ceramics, metals, wood, among others. All these technologies allow parts manufacturing by adding successive layers of material which can be liquid, powder or wire. In order to take advantages of the geometric freedom offered by AM, Topological Optimization (TO) is usually used. TO provides the optimal distribution of material for a given request. The main objective is weight reduction, without compromising the original resistance of an existing part produced by traditional processes. Taking advantage of the freedom allowed by the AM process and conciliating it with the CAE features, which allow to simulate the parts behavior when subjected to the expected loads, a new approach methodology was drawn in order to shorten the time needed to optimize parts design for AM. A case study was developed in order to validate the methodology established. The combination of AM and TO revealed promising results, attending to the component efficiency achieved.

The automotive component industry has grown steadily in the last decade. The automation of the manufacturing processes has boosted an increase in the production rates of the components, and also contributed to a significant increase in quality. Automation has also contributed significantly to an increase in the production rate, as well as the process flexibility and reliability of the products obtained in the manufacture of spiral tubes used in control cables normally used for the operation of doors, brakes, glass handling, etc.. Currently, the manufacturing process of these components can be performed in a completely automated way, which proves the importance of automation in this sector. This work intends to present the development of a new solution for transporting conduits along an automatic production line, where several operations are carried out on the control cable spirals, namely cutting, deburring, punching of terminals at the ends and insertion of a tube starter, to sample noises during operation. An innovative transport system of the main sub-product (conduits) was developed along the line, which has a much higher reliability than previously recorded, also reducing the setup time required by 97%. The stoppages of the equipment due to problems with the conduits transportation process were also drastically reduced. The solution found is extremely simple and economical, allowing the reuse of numerous parts already used in the previous solution, with the consequent benefits in terms of resources reutilization. As an economical solution, it can be easily adaptable to other similar production processes, inducing very appreciable productivity gains.

Partindo da premissa que sugere que um professor é também um investigador, este artigo pretende explorar essa ‘faceta profissional’, mas a partir da experiência de alguns estudantes aquando da frequência de um mestrado profissionalizante para a docência. Para tal, e recorrendo ao programa informático MAXQDA 2018, analisamos o conteúdo de 25 relatórios de estágios de alunos do Mestrado em Educação Pré-Escolar e Ensino do 1.º Ciclo do Ensino Básico selecionados aleatoriamente, tendo atentado em elementos vários, como as temáticas educativas investigadas, as motivações subjacentes às pesquisas ou a concertação entre os pressupostos metodológicos assumidos e os objetivos de investigação definidos.No final, duas ou três considerações ganharam destaque: aqueles futuros docentes, para além de vivenciarem um momento elementar para o desenvolvimento da sua literacia investigativa, reconhecendo as várias dimensões inerentes ao processo, nem sempre são capazes de discernir a prática investigativa da prática pedagógica ou, ainda, distintos métodos de investigação.

This paper studies Optimal Intelligent Supervisory Control System (OISCS) model for the design of control systems which can work in the presence of cyber-physical elements with privacy protection. The development of such architecture has the possibility of providing new ways of integrated control into systems where large amounts of fast computation are not easily available, either due to limitations on power, physical size or choice of computing elements.

Physical vapour deposition (PVD) is a well-known technology that is widely used for the deposition of thin films regarding many demands, namely tribological behaviour improvement, optical enhancement, visual/esthetic upgrading, and many other fields, with a wide range of applications already being perfectly established. Machining tools are, probably, one of the most common applications of this deposition technique, sometimes used together with chemical vapour deposition (CVD) in order to increase their lifespan, decreasing friction, and improving thermal properties. However, the CVD process is carried out at higher temperatures, inducing higher stresses in the coatings and substrate, being used essentially only when the required coating needs to be deposited using this process. In order to improve this technique, several studies have been carried out optimizing the PVD technique by increasing plasma ionization, decreasing dark areas (zones where there is no deposition into the reactor), improving targets use, enhancing atomic bombardment efficiency, or even increasing the deposition rate and optimizing the selection of gases. These studies reveal a huge potential in changing parameters to improve thin film quality, increasing as well the adhesion to the substrate. However, the process of improving energy efficiency regarding the industrial context has not been studied as deeply as required. This study aims to proceed to a review regarding the improvements already studied in order to optimize the sputtering PVD process, trying to relate these improvements with the industrial requirements as a function of product development and market demand.

The technological evolution in the last century also required an evolution of materials and coatings. Therefore, it was necessary to make mechanical components subject to heavy wear more reliable, improving their mechanical strength and durability. Surfaces can contribute decisively to extending the lifespan of mechanical components. Chemical vapor deposition (CVD) and physical vapor deposition (PVD) technologies have emerged to meet the new requirements that have enabled a remarkable improvement in the morphology, composition and structure of films as well as an improved adhesion to the substrate allowing a greater number of diversified applications. Thin films deposition using PVD coatings has been contributing to tribological improvement, protecting their surfaces from wear and corrosion, as well as enhancing their appearance. This process can be an advantage over other processes due to their excellent properties and environmental friendly behavior, which gives rise to a large number of studies in mathematical modelling and numerical simulation, like finite element method (FEM) and computational fluid dynamics (CFD). This review intends to contribute to a better PVD process knowledge, in the fluids and heat area, using CFD simulation methods focusing on the process energy efficiency improvement regarding the industrial context with the sputtering technique.

Productivity is a key factor for companies manufacturing parts and sets to the automotive industry. Automation plays an important role in this matter, allowing development of entire manufacturing cells without the direct need of workers. Even in countries where the labour cost is relatively low, it becomes necessary to improve the level of automation applied to manufacture cells and reduce the dependence of the human labour unpredictability, also increasing the quality and reducing the costs. This case study was developed based on an industrial request in order to improve a semi-automatic cell devoted to seat suspension mat manufacturing. The original cell allows several automatic operations but it needs two workers for two specific operations not considered in the initial design. Thus, new concepts of wire feeding and manipulation were developed in order to allow a better material flow throughout the cell. The new cell was designed and built with success, allowing obtain a fully-automated system, which leads to a better productivity and reliability of the manufacturing process.

The use of hydrogen as an alternative to fossil fuels for vehicle propulsion is already a reality. However, due to its physical characteristics, storage is still a challenge. There is an innovative way, presented in this study, to store hydrogen in conventional vehicles propelled by spark-ignition reciprocating engines and fuel cells, using hydrogen as fuel; the storage of hydrogen will be at high pressure within small spheres randomly packed in a tank, like the conventional tank of fuel used nowadays in current vehicles. Therefore, the main purpose of the present study is to assess the performance of this storage system and compare it to others already applied by car manufacturers in their cars. In order to evaluate the performance of this storage system, some parameters were taken into account: The energy stored by volume and stored by weight, hydrogen leakage, and compliance with current standards. This system is safer than conventional storage systems since hydrogen is stored inside small spheres containing small amounts of hydrogen. Besides, its gravimetric energy density (GED) is threefold and the volumetric energy density (VED) is about half when compared with homologous values for conventional systems, and both exceed the targets set by the U.S. Department of Energy. Regarding the leakage of hydrogen, it complies with the European Standards, provided a suitable choice of materials and dimensions is made.

Water is an important resource for human beings, yet there are inhabited places tormented by the scarcity of it. The present study is concerned with places where, seemingly, the best way to get water is through solar distillers. These places should have, typically, high values of solar irradiation and a lack of human and economic resources to build and operate complex equipment. A set of sites scattered around the world was chosen, and then the presumed productivity and thermal efficiency that solar distillers would have if they were installed at these places was calculated. The mathematical model used with this purpose assumes steady-state operation; the values of mass of water distilled and distiller efficiency were calculated for every hour, but the results presented are annual averages. Then, an economic study was made based on local costs of construction materials for the distillers, the workforce, and the prices of water to predict the payback time of solar distillers. Finally, a study on environmental impact, particularly in terms of greenhouse gas (GHG) emissions, was made to compare reverse osmosis (RO) with solar distillation. For the sites studied, typical values of annual water output are in the range of 414 dm3/m2, for Évora, up to 696 dm3/m2, for Faya Largeau; the minimum efficiency was found for Évora, as 11.5%, and the maximum efficiency was found for Tessalit, as 15.2%. Payback times are very high, regardless of the areas of the globe where solar distillers are implanted. Regarding GHG emissions, solar distillation is preferable to RO.

Advanced coatings play an important role in a wide range of industrial applications. These coatings are commonly used in machining tools due to their high hardness and wear resistance, but also can be applied in jewellery and decorative purposes. Deposition techniques have seen a strong evolution as result of the directly related devices, control evolution and software. Several variants have been developed around the main techniques: arc evaporation and sputtering. The coatings produced present significant differences in their characteristics, namely in terms of structure, mechanical properties and surface morphology. Depending on the substrate material and application, the deposition process needs to be properly selected, providing the particular characteristics requested. This paper intends to do a critical review of the evolution of the advanced coatings deposition process, mainly focused on the Physical Vapour Deposition (PVD) process, particularly in the Magnetron Sputtering technique, which is able to produce smooth surfaces, using lower temperatures, presenting excellent mechanical and tribological properties and having very good adhesion to the main materials used as substrate.

The metal packaging industry used for food application has undergone drastic changes in the demands of its final consumers. The raw material for these packages, is a low carbon steel coated with a thin layer of tin (2,0 g/m2), also known as tinplate. The stamping process of these packages occurs at room temperature and is critically influenced by the tin transfer from the steel surface to the tool surface, mainly due to the tin softness. This problem is easily solved using lubrification but the purpose of this study will be the reduction or even absence of lubricants during the process in order to comply with costumers’ requirements. A successful way to minimize the consumption of lubricants is to use tools which are coated with PVD (Physical Vapour Deposition) advanced coatings deposited with unbalanced magnetron sputtering technique. Thin WC (Tungsten Carbide) and CrCN (Chromium Carbonitride) coatings were deposited using PVD on tool stamping steel – AISI D2. Block on ring tribological tests were performed on the coatings against tinplate counterface in order to investigate their wear performance, with particular emphasis on the material transfer (tin) phenomena during the sliding tests. The results allowed for selecting the best coating tested with a view to avoid the tin adhesion to the die.

Physical Vapour Deposition (PVD) is a process usually used for the production of advanced coatings regarding its application in several industrial and current products, such as optical lens, moulds and dies, decorative parts or tools. This process has several variants due to its strong evolution along the last decades. The process is commonly assisted by plasma, creating a particular low pressure and medium temperature atmosphere, which is responsible for the transition of atomic particles between the target and the parts to be coated into a vacuum reactor. Several parameters are directly affecting the deposition, namely the substrate temperature, pressure inside the reactor, assisting gases used, type of current, power supply, bias, substrate and target materials, samples holder and corresponding rotation, deposition time, among others. Many mathematical models have been developed in order to allow the generation of numerical simulation applications, trying to combine parameters and expect the corresponding results. Numerical simulation applications were created around the mathematical models previously developed, which can play an important role in the prediction of the coating properties and structure. This paper intends to describe the numerical simulation evolution in the last years, namely the use of Finite Elements Method (FEM) and Computational Fluid Dynamics (CFD).