CDRsp - Comunicações em conferências internacionais
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- Ask not what additive manufacturing can do for youPublication . Gibson, I.The paraphrase of John F Kennedy’s famous words is for 2 purposes. Firstly it is to acknowledge that there are some people who have considered that it is a major part of their life’s work to promote Additive Manufacturing (AM) technology as primarily a selfless act. AM comprises an outstanding range of technology that should be brought to public attention as a true revolution in how we design and manufacture products. The second purpose is to show that technology development is only one part of this promotion process and that there are other ways in which we can get involved. This paper describes the author’s journey over the (approximately) 20 years since he was introduced to what was then called Rapid Prototyping (RP). It is not a catalogue of research and development projects but rather a list of activities that he has been involved in to help promote and support AM technology over these years. It will describe the conferences, activities, associations and publications that have been created to allow academics and professionals to describe and discuss their work amongst themselves and to the larger society.
- MICRO MOLD COOLING OPTIMIZATION USING A CONSTRUCTAL APPROACHPublication . Clemente, Miguel R.; Panão, Miguel R. OliveiraMold cooling is one of the most important phases in the molding cycle, comprising more than half of the total cycle time. This affects the final quality of the part and the production rate of the mold. Therefore, the design of a mold cooling channel system is essential to improve its thermal management and achieve a better control over the cycle time. The hardening of small thin wall plastic parts with complex geometries is one of the most challenging problems in the plastics injection industry, since we need to ensure quality, distortion free plastic parts. The solution lies in optimizing the cooling system, particularly the case of mold inserts with unconventional geometries compatible with the geometry of the part. Using the constructal principle, we develop a channel configuration as an umbrella for cooling a mold insert volume. This configuration includes a central channel transporting the coolant until the tip of the mold insert where a certain number of divergent channels depart performing the fluid flow return. A relation for the svelteness allows determining the channels sizes to ensure negligible local head losses, depending on the angle and number of divergent channels. Svelteness orientates the evolution of the flow towards smaller secondary channels returning the flow with higher divergent angles.
- Biomechanics modeling for functional analysis: Sheep modelPublication . Silva, Rui; Amado, Sandra; João, Filipa; Morouço, Pedro; Pascoal-Faria, Paula; Alves, Nuno; Veloso, AntónioThe aim of the present manuscript was to provide information on the suitability of using ovine as models for conducting in vivo bone tissue engineering studies, regarding the biomechanical considerations. Despite the need of knowledge of the animal model used for bone tissue research a good planning and study design is equal important. The purpose of this review is to contribute to extrapolation of reliable data for those who pretend to use the ovine model in tissue engineering and regenerative medicine.
- Cyclic plastic behaviour of 7075 aluminium alloyPublication . Nogueira, F.; Cunha, J.; Mateus, A.; Malça, C.; Costa, J. D.; Branco, R.This paper aims at studying the cyclic plastic behaviour of the 7075-T651 aluminium alloy under fully-reversed strain-controlled conditions. Tests are conducted under strain-control mode, at room temperature, in a conventional servo-hydraulic machine, from smooth samples, using the single step method, with strain amplitudes (∆ε/2) in the range ±0.5 to ±2.75%. This material has exhibited a mixed behaviour, i.e. cyclic strain-hardens at higher strain amplitudes (∆ε/2/>1.1%) and cyclic strain-softens at lower strain amplitudes (∆ε/2<1.1%). A linear relationship between the degree of cyclic strain-hardening and the strain amplitude has been established for higher strain amplitudes. Fatigue-ductility and fatigue-strength properties agree with those found in the open literature for the same loading conditions.
- Mechanical properties assessment for TPMS based scaffolds using homogenization methodsPublication . Pinheiro, J.; Castro, A. P. G.; Ruben, R. B.; Guedes, J. M.; Fernandes, P. R.The combination of computational methods with recent 3D printing technologies allows for the control of scaffolds microstructure, in order to obtain application-driven mechanical properties. Lately, geometries obtained using triply periodic minimal surfaces (TPMS) have been used to design porosity-controlled scaffolds for bone tissue engineering. The objective for this work is to assess the properties of TPMS scaffolds obtained using Schwartz P, Schwartz D and Gyroid, with different porosity levels. These properties are computed by an asymptotic homogenization method to obtain the effective permeability and stiffness. Results show that the obtained properties compare well with the properties of bone scaffolds presented in literature and obtained using different means.
- Thermal analysis of an extrusion system of a 3-D bioprinterPublication . Ribeiro G.S.; Silva J.V.L.; Freitas D.; Bartolo P.; Almeida, Henrique de Amorim; Silveira Z.C.This work presents a finite element thermal analysis of a 3-D bioprinter desktop based on Fused Deposition Modeling (FDM) with applications on tissue engineering, designed by the Centre for Rapid and Sustainable Product Development - Leiria, Portugal. The purpose of this work it is compare three possibilities of temperature control of the machine during the extrusion process, considering the use of a biodegradable polyester (Polycaprolactone - PCL) as raw material. The first two configurations simulate approaches typically adopted in an attempt to keep the polymer as close as possible to 80 °C and prevent its premature solidification at a critical point. The third configuration considers a hypothetical material substitution to enhance thermal conductivity. The results indicate that the first two configurations are not sufficient to achieve total control of the polymer temperature. However, the third configuration show a significant potential to improve the thermal control of the extrusion process.
- Numerical study on injection parameters optimization of thin wall and biodegradable polymers partsPublication . Santos, Cyril; Mendes, A; Carreira, P.; Mateus, Artur; Malça, C.Nowadays, the molds industry searches new markets, with diversified and added value products. The concept associated to the production of thin walled and biodegradable parts mostly manufactured by injection process has assumed a relevant importance due to environmental and economic factors. The growth of a global consciousness about the harmful effects of the conventional polymers in our life quality associated with the legislation imposed, become key factors for the choice of a particular product by the consumer. The target of this work is to provide an integrated solution for the injection of parts with thin walls and manufactured using biodegradable materials. This integrated solution includes the design and manufacture processes of the mold as well as to find the optimum values for the injection parameters in order to become the process effective and competitive. For this, the Moldflow software was used. It was demonstrated that this computational tool provides an effective responsiveness and it can constitute an important tool in supporting the injection molding of thin-walled and biodegradable parts.
- A method for automatic detection of rectangular regions of interest in arbitrary imagesPublication . Martins-Ferreira, Nelson; Ferreira, Lino; Pascoal-Faria, Paula; Cruz, Luis A. da Silva; Assunção, Pedro; Alves, NunoThis paper presents a computational method to extract optimum rectangular Regions of Interest (RoI) in images with an associated saliency map. Although saliency maps provide an individual relevance measure for each pixel, to find the sub-image (i.e., rectangular region) that contains the set of the most relevant pixels requires an optimisation procedure to define the boundaries of the best RoI. This is achieved by the method devised in the paper, by following an approach based on balancing the amount of relevant information that is included and excluded from the RoI. The results show that such method is capable of finding the most relevant rectangular RoI and thus to extract the optimum sub-images according to the relevance measure given by a generic saliency map. Since the method is not tied to any particular type of images, it finds application in quite different fields, such as salient object extraction and processing in industry and surveillance, image compression using attention modelling, biomedical imaging, etc.
- Finite element analysis of a human temporomandibular joint disc: Preliminary resultsPublication . Gomes, Sara; Ângelo, David; Pascoal-Faria, Paula; Mateus, Artur; Alves, NunoThe temporomandibular joint (TMJ) is an important joint that plays a paramount role during the mandibular movement. TMJ disc is an essential component in the normal TMJ, interposed between the mandibular condyle and temporal fossa with the following functions: it distributes the intra-articular load, stabilizes the joints during translation and decreases the wear of the articular surface. The mechanical behaviour study of this element is therefore essential to provide alternative solutions when its replacement becomes essential. The aim of this study is to present a preliminary three dimensional mechanical model to study the stresses distributions at TMJ disc and to provide an efficient tool as an alternative to experimental preclinical studies. The human mandibular condyle, the TMJ disc and the temporal fossa were considered to build the finite element model; additionally, two types of connections were used between the disc and the bone simulating the retrodiscal tissue and lateral pterygoid muscle: frictionless and bonded. At this stage, the elastic behaviour of materials was taken into account. Results show that the computed von Mises stresses are in accordance with previous studies.
- Micro-cooling constructal design: An application to mold inserts thermal managementPublication . Clemente, Miguel R.; Panão, Miguel R.; Pascoal-Faria, Paula; Alves, NunoMold thermal performance has a direct influence on part properties, quality and defects, and mold productivity. Through additive manufacturing, inserts can be developed with features that respect the necessary high complex geometries the part requires and that increase thermal performance. Constructal design is explored as a design tool to produce guidelines for cooling channels development.
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