Repositório RCAAP

This work proposes a multi-criteria decision making model to assist in the choice of a strategic plan for a world-class company. The Balanced Scorecard (BSC) is a support tool of Beyond Budgeting that translates a company’s vision and strategy into a coherent set of performance measures. However, it does not provide help in choosing a strategic plan. The selection of a strategic plan involves multiple goals and objectives that are often conflicting and incommensurable. This paper proposes an integrated Analytic Hierarchy Process-Goal Programming (AHP-GP) approach to select such a plan. This approach comprises two stages. In the first stage, the AHP is used to evaluate the relative importance of the initiatives with respect to financial indicators/KPIs; while in the second stage a GP model incorporating the AHP priority scores is developed. The GP model selects a set of initiatives that maximizes the earnings before interest and taxes (EBIT) and minimizes the Capital Employed (CE). The proposed method was evaluated through a case study.

Today’s society is technologically advanced, the world is just a click away and our companies’ customers have easy access to all the information. Therefore, they are increasingly demanding, wanting more and better at a lower cost. Using as a case study a shipping company, a system of Customer Relationship Management (CRM) was analysed to verify what reasons led to its abandonment and to realise what to do to reverse such situation. In this industry product differentiation is practically null, so the customer’s choice comes down to price. However, customers are paying more attention to customer service, therefore companies are developing stronger relationships with them. The construction of such relationships implies data collection on the client, from which one can offer services of greater value. This may lead to partnerships and competitive advantages. Thus, the use of CRM tools is being promoted for CRM tools present themselves as a valuable asset. In the end, suggestions are presented, ranging from improvements to the existing system, to more complex suggestions, costlier or breaking with the existing mode of relationship and dialogue between company and customers, but that, in the future, will certainly translate into advantages over competing companies.

Zamak is a light-weight alloy presenting very good properties for parts not requiring high mechanical strength. Due to its low melting temperature, this alloy is perfectly suitable for complex shape parts because it is easily moulded by high-pressure die casting process. Industrial parts usually do not require perfect look but this alloy can be also suitable for aesthetic parts, requiring complex finishing processes.The challenge embraced by this work aims to optimize the injection parameters and mould configuration of a Zamak alloy aesthetic part, to be obtained through a single injected casting operation, minimizing finishing operations. In order to obtain healthy, defect-free Zamak parts with a good aesthetic appearance, it was necessary to study the problem and then try to find the best possible solution. Thus, a study was carried out about the high-pressure die casting process and corresponding parameters. Throughout the work, and in order to solve the problem, numerical simulations were carried out using the SolidCast™ software, studying the material flow into the mould and corresponding fusion lines, and empirical tests were carried out in order to correlate the results with the parameters. Changes in the mould were also performed. After the experiences, it was possible to draw some guidelines in order to achieve better results in the Zamak high-pressure die casting process of complex aesthetic parts, allowing for save time in next approaches.

Pultrusion is a versatile continuous high speed production technology allowing the production of fibre reinforced complex profiles. Thermosetting resins are normally used as matrices in the production of structural constant cross section profiles. Although only recently thermoplastic matrices have been used in long and continuous fibre reinforced composites replacing with success thermosetting matrices, the number of their applications is increasing due to their better ecological and mechanical performance. Composites with thermoplastic matrices offers increased fracture toughness, higher impact tolerance, short processing cycle time and excellent environmental stability. They are recyclable, post-formable and can be joined by welding. The use of long/continuous fibre reinforced thermoplastic matrix composites involves, however, great technological and scientific challenges since thermoplastics present much higher viscosity than thermosettings, which makes much difficult and complex the impregnation of reinforcements and consolidation tasks. [1] In this work continuous fibres reinforced thermoplastic matrix towpregs were produced using equipment developed by the Institute for Polymers and Composites (IPC). The processing of the towpregs was made by pultrusion, in a developed prototype equipment existing in the Engineering School of the Polytechnic Institute of Porto (ISEP). Different thermoplastic matrices and fibres raw-materials were used in this study to manufacture pultruded composites for commercial applications (glass and carbon fibre/ polypropylene) and for advanced markets (carbon fibre/Primospire®). To improve the temperature distribution profile in heating die, different modifications were performed. In order to optimize both processes, towpregs production and pultruded composites profiles were analysed to determine the influence of the most relevant processing parameters in the final properties. The final pultruded composite profiles were submitted to mechanical tests to obtain the relevant properties.

The biggest advantagein the use of thermoplastic composites is the possibility of recycling and reprocessing, which is not possible with thermosetting composites. The shorter manufacturing cycle time and lower chemical emissions are, as well, other advantages. The use of thermoplastic matrix composites creates new engineering challenges concerning the manufacturing due to their high viscisity during manufacture. For all the advantages that these materials present, it becomes useful to study and evolve the universe of composites in the direction of thermoplastics. In this work, continuous fiber thermoplastic composites were produced and transformed by pultrusion and heated compression moulding. The manufactured composites were then tested, and mechanical properties were determined and studied.

This chapter considers sandwiched composites used in aerospace applications. It discusses new developments in the types of face and core materials, production methods and joining and repair techniques. It also discusses various properties as well as their main design methods. Both existing and future applications of sandwiched composites are discussed.

In the energy management of the isolated operation of small power system, the economic scheduling of the generation units is a crucial problem. Applying right timing can maximize the performance of the supply. The optimal operation of a wind turbine, a solar unit, a fuel cell and a storage battery is searched by a mixed-integer linear programming implemented in General Algebraic Modeling Systems (GAMS). A Virtual Power Producer (VPP) can optimal operate the generation units, assured the good functioning of equipment, including the maintenance, operation cost and the generation measurement and control. A central control at system allows a VPP to manage the optimal generation and their load control. The application of methodology to a real case study in Budapest Tech, demonstrates the effectiveness of this method to solve the optimal isolated dispatch of the DC micro-grid renewable energy park. The problem has been converged in 0.09 s and 30 iterations.

The aim of this work is to produce and optimize the processing of carbon fibres thermoplastic matrix pre-impregnated materials (towpregs and PCT´s). Pultrusion and heated compression moulding were the selected manufacturing methods for processing all carbon fibres thermoplastic matrix pre-impregnated materials into composite parts. The optimization of those processes 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 method of Taguchi / DOE (Design of Experiments) was used to achieve this aim as it allowed making more rational choices of processing windows. The composite relevant mechanical properties were determined and studied. The final composites were also submitted to SEM microscopy analysis.

Historically, thermoset resins have dominated the composite industry but they start to be replaced by thermoplastics. In this study two different thermoplastic matrix carbon reinforced pre-impregnated materials were used, one produced in our laboratories (towpreg) and another obtained from coextrusion process (PCT). Carbon fibre and two different thermoplastic matrices (polypropylene and PRIMOSPIRE®) were selected for the production of the pre-impregnated materials. Heated compression moulding and pultrusion were the two manufacturing technologies used to obtain composite plates and profiles for study. The optimization of those processes 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 the final composites were submitted to Dynamic Mechanical Analysis (DMA), Scanning Electron Microscope (SEM), optical microscopy and calcination tests. The determination of the fiber volume fraction of all studied composite was obtained comparing the results of thermogravimetric analysis (TGA), SEM and calcination tests.

This paper presents an experimental study that aims to compare the practical performance of well-known metaheuristics for solving the parameter estimation problem in a dynamic systems context. The metaheuristics produce good quality approximations to the global solution of a finite small-dimensional nonlinear programming problem that emerges from the application of the sequential numerical direct method to the parameter estimation problem. Using statistical hypotheses testing, significant differences in the performance of the metaheuristics, in terms of the average objective function values and average CPU time, are determined. Furthermore, the best obtained solutions are graphically compared in relative terms by means of the performance profiles. The numerical comparisons with other results in the literature show that the tested metaheuristics are effective in achieving good quality solutions with a reduced computational effort.

Thermoplastic matrix composites are receiving increasing interest in last years. This is due to several advantageous properties and speed of processing of these materials as compared to their thermoset counterparts. Among thermoplastic composites, Long Fibre Thermoplastics (LFTs) have seen the fastest growth, mainly due to developments in the automotive sector [0, 2]. LFTs combine the (semi-)structural material properties of long (>1 cm) fibres, with the ease and speed of thermoplastic processing. This paper reports a study of a novel low-cost LFT technology and resulting composites. A patented powder-coating machine [3, 4] able to produce continuously pre-impregnated materials directly from fibre rovings and polymer powders was used to process glass-fibre reinforced polypropylene (GF/PP) towpregs. Such pre-impregnated materials were then chopped and used to make LFTs in a patented low-cost piston-blender developed by the Centre of Lightweight Structures, TUD-TNO, the Netherlands [5, 6]. The work allowed studying the most relevant towpreg production parameters and establishing the processing window needed to obtain a good quality GF/PP powder coated material. Finally, the processing window that allows producing LFTs of good quality in the piston-blender and the mechanical properties of final stamped GF/PP composite parts were also determined.

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.