Browsing by Issue Date, starting with "2019-04-09"
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- Direct Digital Manufacturing in the Context of a Circular EconomyPublication . Fonseca, Diana A.; Simões, FábioAdditive manufacturing technologies have evolved from prototype to part production. Coupling this shift with organizational transformations evolved rapid prototyping industry into Direct Digital Manufacturing (DDM) industry. Any evolution in production systems is now, more than ever before, dependent on sustainability principles. The development of the DDM industry must be guided by these principles, taking the chance it offers to change the production paradigm. Circular Economy (CE) is a shift in the production and resource management model, and one of the ways to work towards sustainability. Coupling DDM with CE principles is thus contributing to change industrial production to a more sustainable one. This paper intends to relate DDM technologies with CE principles, to identify aspects where DDM is contributing to CE, as well as aspects that should be explored further for that purpose. It is observed that DDM can enable optimization of material and energy usage, modify logistics towards de-localized production and recycling and enable prolonged lifespan of products through better access to spare parts, for instance. It is also observed that DDM has good potential to shift materials usage towards natural materials, especially in a context of consumer or local community production, but not so much within the current industrial context. Education is shown to play a pivotal role, since incorporating circular economy principles in educational contexts should spark a shift in consumer perspectives, modifying demand and hence, industrial production.
- Sheep Gait Biomechanics and the Assessment of Musculoskeletal Conditions: A Systematic ReviewPublication . Silva, Rui; Dimas, Ivo Santos; Fernandez, Justin W.; Alves, Nuno; Morouço, Pedro; Maurício, Ana Colette; Veloso, António; Sandra, AmadoIn recent years, sheep have been reported as the ideal animal model to study osteoporosis, hence it is important to identify instruments, tools and ideal parameters needed to assess the effects of different treatments. In previous studies conducted in other animal models with osteoporosis, the most common parameters used for evaluation concerned primarily bone properties, such as the dual X-ray absorptiometry. However, biomechanical gait analysis as an integrative functional parameter and a non-invasive method, will be an important tool in research and clinical applications. This research review was performed using the PubMed database and included studies related to sheep with outcome measures concerning functional performance assessed during gait in vivo; and excluded studies related with cardiovascular disease and sperm properties, which include other animal species, with outcomes not related with functional locomotor evaluation. Only studies related with bone properties were analyzed. The most frequent and relevant included parameters were the following: mean peak vertical ground force reaction, gait cycle and stance/swing phase duration, percentage of stance/swing phase in a gait cycle, stride length and the stifle joint angles during a gait cycle. Gait biomechanical parameters have been established for the assessment of some clinical orthopedic condition using sheep models but not currently for osteoporosis.
- A Computer Tool for 3D Shape Recovery of FruitsPublication . Gaspar, Miguel; Pascoal-Faria, Paula; Amado, Sandra; Alves, NunoCharacterizing a fruit’s mechanical behavior is an important step towards reducing economic losses due to bruising. Several 3D scanning technologies allow to obtain the external geometry of a fruit, but no easily accessible tools exist for the acquisition of the geometry of internal structures such as the core. We propose a low-cost destructive method for tomographic reconstruction of a fruit from scanned slices. A method for overcoming the difficulties in registering the different images is also presented.
- The Exploitation of Polymer Based Nanocomposites for Additive Manufacturing: A Prospective ReviewPublication . Khan, Imran; Kamma-Lorger, Christina S.; Mohan, Saeed D.; Mateus, Artur; Mitchell, GeoffreyAdditive manufacturing (AM) is a well-known technology for making real three dimensional objects, based on metal, ceramic and plastic material used for various applications. The aim of this review is to explore and offer an insight in to the state of the art polymer based nanocomposites in to additive manufacturing applications. In context to this, the developing efforts and trends in nanocomposites development particularly for additive manufacturing processes were studied and summed up. The scope and limitations of nanocomposites into Stereolithography, selective laser sintering and fused deposition modeling was explored and highlighted. The review highlights widely accepted nanoparticles for range of applications including mechanical, electrical, flame retardance and crossing over into more biological with the use of polymer matrices. Acquisition of functional parts with limitations in regard to printing is highlighted. Overall, the review highlights successes, limitations and opportunities that the union of AM and polymer based nanocomposites can bring to science and technology.
- Characterization of Biocompatible Poly(Ethylene Glycol)-Dimethacrylate Hydrogels for Tissue EngineeringPublication . Lopes, João; Fonseca, Rita; Viana, Tânia; Fernandes, Cristiana; Morouço, Pedro; Moura, Carla; Biscaia, SaraTissue Engineering depends on broadly techniques to regenerate tissues and/or organ functions. To do so, tailored polymeric and/or hydrogel scaffolds may be used to ensure the appropriate regeneration. Hydrogels are suitable materials for constructing cell-laden matrices as they can be produced with incorporation of cells and rapidly cross-linked in situ through photopolymerisation reactions. Measurement of the polymerization degree, as well as resistance to compression and water retention are fundamental tests to evaluate the characteristics of hydrogels. In this work, free-radical polymerisation of poly(ethylene glycol)-dimethacrylate (PEGDMA) in UV light was assessed. Several hydrogels with different photoinitiator and water contents were produced to evaluate their influence on hydrogels behaviour. Experiments showed that variations on water and photoinitiator content induce changes in the physical and chemical behaviour of hydrogels. As it was found, water content prevents polymerisation to occur and reduces the mechanical properties of hydrogels weakening them. Furthermore, differences were found in varying water content from 15 to 30%, since this increase turned hydrogels more fragile and increase their stabilization time for water retention.
- Rosin Based Composites for Additive ManufacturingPublication . Sousa, Dora; Biscaia, Sara; Viana, Tânia; Gaspar, Miguel Belbut; Mahendra, Vidhura; Mohan, Saeed D.; Mateus, Artur; Mitchell, GeoffreyRosins are the non-volatile exudates of pine resins with hydrophobic characteristics that are widely used as a precursor for many industrial applications. In this paper we discuss the nature, process and its applications as a matrix for a composite material for additive manufacturing. The composite material has been tailored to chemical and mechanical properties with respect to their applications.
- Polyethylene and the Nucleating Agent: Dibenzylidene Sorbitol, a Neutron Scattering StudyPublication . Mitchell, Geoffrey R.; Pratumshat, Supatra; Olley, RobertDibenzylidene Sorbitol is a very effective clarification additive for isotactic polypropylene. It is not effective with polyethylene although recent studies have shown that it can act as an effective nucleating and directing agent. We employ small-angle neutron scattering measurements to more fully understand the behavior of dibenzylidene sorbitol in a polyethylene matrix. The small-aangle neutron scattering clearly shows that the disappearance of the DBS fibrils is concentration dependent and for 2% DBS the midpoint of the dissolution is at 145°C and for 1% is ~ 20°C lower.
- Industry 4.0 - Digital Twin Applied to Direct Digital ManufacturingPublication . Vitorino, João; Ribeiro, Eliseu; Silva, Rúben; Santos, Cyril; Carreira, Pedro; Mitchell, Geoffrey; Mateus, ArturMarinha Grande is a city in Leiria’s district, Portugal. Marinha Grande is known as the moulding city, influenced by the glass, plastic and rapid manufacturing industry. Its history comes from the 18th century with the first glass factory. In order to improve technological development in the local industry, Centre for rapid and sustainable product development (CDRsp) was established in 2007. With that historical know-how and data-based moulding manufacturing, this work goal is to link that data with today’s technology, implementing the Industry 4.0. That information would be stored in a Cloud-Based Design and Manufacturing (CBDM) as well as the real-time operational data. Accessing to that cloud, the design and production engineers can work together to digitally create a product without having to stop the machinery. To implement these concepts, this paper suggests a Digital Twin (DT) to take advantage of the historical information allied to the existent industrial machinery. It suggests a digital twin of a robotic arm with an additive or hybrid manufacturing tool, printing big parts (e.g. garden benches or urban furniture) with reused materials such as tire, cork, wood or stone pow loads.
- High Efficiency Cooling and Heating Channels for Injection MouldingPublication . Freitas, Paulo; Santos, Cyril; Carreira, Pedro; Mateus, ArturFor many years traditional injection moulding has been the norm for obtaining polymer based products, and yet this cycle still shows potential for improvement. This paper will encompass the potential in the thermal part of the cycle, by introducing a novel approach to conventional tubular cooling designs, empowered by additive technologies this reiterates what’s being known as conformal cooling. Different geometries and techniques are compared to determine the optimal cross section layout of the fluid channels and inner surface of the moulding parts. If the cooling achieved is sufficiently fast the crystallographic growth of the material can be manipulated to obtain specific properties observable in the mesoscale. This however can be transversely applied in other heat exchanging structures in future studies.
- Rosin Product ReviewPublication . Mahendra, VidhuraRosin is the non-volatile exudate of pine resin with hydrophobic characteristics that are widely used and modified as a precursor for many industrial applications such as paints, inks and adhesives. The review paper discusses the rosin, its nature, processing, production material development for green science. The composite materials have been designed and tailored with respect to desired applications to offer a potential replacement of petrochemical use. Rosin consists of different resin acids that can undergo isomerisation at elevated temperatures and interchange its form, which, can be used as a rigid building block to manipulate their mechanical properties and crystallisation behaviours. Modified rosin epoxy binders have been recognised as materials with resistance to a wide variety of chemical conditions that can be used to fabricate a variety of reinforced constructions. Rosin has been employed in foam making in addition to composite material, depicting its ability as a crosslinker.
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