ABSTRACT One of the many benefits of additive manufacturing (AM) is to produce parts ready to assemble and use, a concept called direct digital manufacturing (DDM). This, besides the ease of manufacturing complexes geometries, creates a potential for applying the AM technology for producing small wind turbines (SWT) blades. Small wind turbines have an increasing role in the worldwide energy matrix, which can be built up by developing site-optimized and customized turbines. Customizing SWT can increase the energy harvesting potential of such machines; however, it requires flexible manufacturing procedures. The blade’s geometric complexity and flexible manufacturing are features that can benefit from the potentials of AM. This work analyses the final geometry of SWT blades manufactured by AM, assessing the scope of DDM in the SWT field. The parts length is 225 mm, the blades were manufactured by the Fused Deposition Modeling (FDM) method using a Dimension Elite machine produced by Stratasys. The geometric evaluation was performed using a CROMA coordinate measuring machine. The measurements showed good results when compared to values adopted in several studies that investigated the effects of geometric disturbances on wind turbine blades. This work affirms that AM is a powerful technology for manufacturing SWT blades in a DDM scope.

Abstract Vat photopolymerization (VP) stands out among ceramic additive manufacturing processes for its ability to print sub-100 micrometer complex features. One of the main challenges of this process is the preparation of a homogeneous and stable ceramic slurry with a high solid load and low viscosity. In this work, different dispersants and resins were tested, aiming to provide a solvent-free slurry suitable for DLP additive manufacturing. Disperbyk-111 and PEGDA 250 stood out in the tests, providing a 40 vol% ceramic slurry with no noticeable sedimentation and viscosity of 2.3 Pa.s at 30 s-1 despite the relatively high specific surface area (15 m2/g) of the 3Y-TZP powder used compared to powders usually used for VP slurries. The adsorption of Disperbyk-111 on ceramic particles surface was investigated by FTIR. Finally, ceramic bodies were 3D printed, debound and sintered at 1500 ºC for 2 h, confirming the ability to manufacture detailed dense ceramic parts.

Abstract This study characterized the morphological aspects of marine collagen - spongin (SPG) extract from marine sponges, as well as, evaluating its in vitro and in vivo biological performance. Aplysina fulva marine sponge was used for the SPG extraction. It was investigated the physicochemical and morphological properties of SPG by using scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and compared to PMMA and bovine collagen. Additionally, the SPG cytotoxicity and its influence on cell proliferation, through in vitro tests. Moreover, the in vivo biological response was investigated using an experimental model of tibial bone defect. The results demonstrated that SPG presented an irregular granular aspect, with a composition of OH, C=O, NH, CN and an amorphous profile. Also, in vitro viability results for the L929 and MC3T3 cell lines cultured with SPG extracts demonstrated normal growth in comparison to controls, except for MC3T3 viability at day 3. For in vivo analysis, using tibial bone defects in rats, SPG treated animals presented an increased rate of material resorption and higher granulation and bone formation deposition in the region of the defect, mainly after 45 days. As a conclusion, SPG was successfully extracted. The in vitro and in vivo studies pointed out that SPG samples produced an increase in L929 and MC3T3 viability and improved the performance in tibial bone defects. It can be concluded that SPG can be used as a bone graft for bone regeneration.

ABSTRACT Purpose To analyze and compare the reactions at the interface between the composite, composed of fragmented heterologous mineralized bone matrix (MOMHF) and polymethylmethacrylate (PMMA), and the rabbit’s tibias, through macroscopic evaluation and scanning electron microscopy (SEM) in different periods. Methods In this study, 12 New Zealand adult rabbits were used (E1: n = 3, E2: n = 3, E3: n = 3 and E4: n = 3). They had the right tibial defects filled with composite and were evaluated immediately after surgery and at 30, 60, 90, and 120 days. Results The composites were incorporated and integrated into the recipient beds in 100% of the cases, defined by the MOMHF osseointegration and the PMMA fibrointegration, with no sign of infection, migration, or rejection. Conclusions The behavior of the composites in the recipient beds demonstrates that these biomaterials have the potential to be used in bone defect repairs, offering, thus, better quality of life to the orthopedic patient.

Abstract Additive manufacturing processes have been developed over the last decades, especially vat photopolymerization (VP) processes, due to its simplicity and speed. The objective of this paper is to characterize commercial VP resins widely used for technical applications. Thus, test specimens were printed by Digital Light Processing and subjected to tensile, compression, flexural, hardness, and inorganic composition analyses. The resin with the highest resistance and hardness (containing 0.6 vol% of inorganics load) reached 53 MPa in tension, 110 MPa in compression, 79 MPa in bending, and 82.3 Shore D, which is comparable to injected polymers. A case study was made, replacing the injected gears of a reducer by printed ones and comparing the finite element analysis with resin properties. The characterization and case study results encourage the expansion of VP processes in the manufacturing of products in several industries and service sectors, as well as the development of new composite resins.

RESUMO A manufatura aditiva (AM) tem proporcionado grande versatilidade na geometria e em materiais, permitindo que novos produtos e processos sejam criados em diversas áreas. Deposição Direta de Energia (DED) é um processo de manufatura aditiva criado em 1995 que permite a fabricação de componentes metálicos e cerâmicos com alta densidade sem a necessidade de etapas posteriores, a exemplo de sinterização ou infiltração. Este artigo objetiva o estudo do estado da arte do processo DED relacionado à cerâmica. Partindo da geração de uma linha do tempo da manufatura aditiva, que inclui os marcos relacionados à Deposição Direta de Energia, foi realizada uma revisão sistemática em que os artigos foram agrupados em 3 categorias: revestimento cerâmico, AM de cerâmica e AM de compósitos com reforços cerâmicos. Para cada categoria foram analisados, classificados e resumidos aspectos referentes às matérias primas, substratos de deposição, principais aplicações, parâmetros de processo e propriedades. A maior parte dos trabalhos referente à categoria da manufatura aditiva cerâmica está relacionada com a fabricação da alumina, sendo que propriedades já são similares às produzidas por processos convencionais de manufatura. Trabalhos recentes utilizaram a vibração ultrassônica para homogeneizar o material em processo, reduzindo trincas e melhorando as propriedades mecânicas. A categoria AM de compósitos com reforços cerâmicos tem sido empregada para criar materiais compósitos com gradiente funcional de elevada dureza, enquanto que a categoria de revestimentos cerâmicos tem sido majoritariamente utilizada para fabricação de revestimentos biocompatíveis com elevada dureza e baixa taxa de desgaste. De modo geral, é certo que o advento dessa tecnologia vai ocupar fatia importante da manufatura cerâmica.

ABSTRACT Additive manufacturing (AM) has provided huge versatility in geometry and materials, allowing new products and processes in several areas to be created. Laser Engineered Net Shaping (LENS) is an additive manufacturing process created in 1995 that allows building high-density metals and ceramics parts with no need for further operation. This manuscript aims to study the scientific literature about the process of Laser Engineered Net Shaping related to ceramics. After a systematic review, the articles were grouped into three categories: ceramic coating and AM of ceramics and AM of composites with ceramic reinforcement. Raw materials, substrates, applications, process parameters, and the obtained properties were analyzed and summarized for each group. Most of the additive manufacturing of ceramic parts are related to alumina, which present similar properties when compared to the traditionally manufactured ones. Recent works have the aid of an ultrasonic vibration to homogenize the in-process material, reduce cracks and improve mechanical properties. The additive manufacturing of composites with ceramic reinforcement has been used to create functionally graded composites materials with increased hardness, while the ceramic coating has been employed to manufacture biocompatible coating with increased hardness and low wear rate. Moreover, an additive manufacturing timeline including Laser Engineered Net Shaping landmarks is presented.

Planetary ball mills are able to perform dry and wet grinding. Most experimental analyses and computer simulations in this field are mainly about dry grinding. In order to empirically evaluate the wet grinding process, test grindings benches were manufactured, calcined alumina powder was ground, and the particle distribution analyzed. Effects of the media geometry (size and shape) on particle distribution, morphology, and phase composition of ground alumina were investigated. Smaller media leads to smaller particle size and cylindrical media provides a poor grinding performance but its product has the narrower particle size distribution. Alumina showed no phase change in the grinding tests. The experiments presented in this study can be used as an aid in the proper choice of grinding media or even to validate emerging models capable of predicting breakage in wet grinding.

ABSTRACT The structure is a component that plays an extremely important role in the equipment’s performance, it must withstand efforts without compromising the function, receive and transfer heat, dampen vibrations and position the elements, as well as promote ergonomics and aesthetics. In lightweight and precision equipment’s the raw material used must also allow thin walls, rigid, resistant and low density. The objective of the present work is the development of a synthetic granite composite for manufacturing of equipment’s structures. For this, an abundant Brazilian granite, a high strength epoxy resin and segmented carbon fibers were selected as materials. Test specimens, with maximized packing with granite gravel less than 2.0 mm were fabricated and tested for tensile strength, compression, flexural, damping, hardness, dilatometry, thermal conductivity and density. The maximized composition supported flexural stresses above 42 MPa, without fiber reinforcement and 51 MPa with carbon fiber reinforcement. The damping coefficient was about 7 times higher than cast iron, coefficient of thermal expansion of 1.4E-05 m/m.K, thermal conductivity coefficient of 1.2 W/m.K and density of 2.1 g/cm3. The developed composite showed potential for refining structures, with ease of molding of thin-walled elements, use of inserts, re-machining, providing economical manufacture of single parts, and is still able to perform the function with high damping coefficient and low weight.

Abstract Introduction Biomechanical assessment of trabecular bone microarchitecture contributes to the evaluation of fractures risk associated with osteoporosis and plays a crucial role in planning preventive strategies. One of the most widely clinical technics used for osteoporosis diagnosis by health professionals is bone dual-energy X-ray absorptiometry (DEXA). However, doubts about its accuracy motivate the introduction of congruent technical analysis such as calcaneal ultrasonometry (Quantitative Ultrasonometry - QUS). Methods Correlations between Bone Quality Index (BQI), determined by calcaneal ultrasonometry of thirty (30) individuals classified as normal, osteopenic and osteoporotic, and elastic modulus (E) and ultimate compressive strength (UCS) from axial compression tests of ninety (90) proof bodies from human vertebrae trabecular bone, which were extracted from cadavers in the twelfth thoracic region (T12), first and fourth lumbar (L1 and L4). Results Analysis of variance (ANOVA) showed significant differences for E (p = 0.001), for UCS (p = 0.0001) and BQI. Spearman’s rank correlation coefficient (rho) between BQI and E (r = 0.499) and BQI and UCS (r = 0.508) were moderate. Discussion Calcaneal ultrasonometry technique allowed a moderate estimate of bone mechanical strength and fracture risk associated with osteoporosis in human vertebrae.

Abstract Introduction Rheumatoid arthritis (RA) is a chronic, multisystem disease that involves synovial inflammation, leading to deformities, like finger ulnar deviation, pain and functional difficulties. The conservative treatment comprises orthoses, features added to the body that aims to correct deformity, reduce pain and improve functionality. In the market there are few kinetic/mobile orthosis models for correction of ulnar deviation in the fingers. However, users usually complain about increased palmar volume, presence of pressure points and functional loss, demonstrating the necessity to develop more effective orthoses. In this paper we introduce an innovative concept, of an original and articulate dynamic/kinetics orthosis, which aims to correct this finger deformity and encourage functionality. Methods Methodological procedures were divided into: Need Recognition; Specification Concept; Prototype and Validation. This paper deals with the last two stages of this research. Results A virtual orthosis prototype using CAD Solid Edge Insight™ was proposed. The orthosis developed consisted of 10 pieces, made of metal and resin with carbon fiber. Conclusion After virtual movement simulation, it was verified that the prototype allows for wrist and finger flexion/extension, the possibility of bilateral use, and provids ulnar deviation correction for the fingers. The final product is innovative and is easy to put on/off; volunteers claimed that the new prototype was satisfactory in terms of deformity correction.

Duplex stainless steels have a large number of industrial applications and may replace high cost materials, especially in chloride-containing environments like seawater in off-shore platforms due to their high mechanical properties and good corrosion resistance. The influence of the ferrite content on the performance of duplex stainless steels in these corrosive environments is not well known. For the present paper, new superduplex stainless steels with ferrite between 30 and 60% were developed and their microstructure and corrosion resistance were evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests in NaCl 3.5% (wt %) at 26°C and 78°C. The results obtained at 26°C showed that the pitting potential (Epitt) is little affected by the ferrite content, but for the materials with higher ferrite it was possible to observe an increase in the repassivation potential with a decrease in the corrosion potential and passive currents due to the presence of more resistive passive films. Tests performed at 78°C indicated a high decrease in the Epitt for all the samples, independently of the ferrite percentage, although maintaining superiority in higher ferrite content. Alloys with a 55% ferrite phase content, i.e. less dependent of Ni element, present a superior performance of corrosion resistance.

RESUMO A zircônia Y-TZP é muito utilizada na confecção de coping como material estrutural para próteses odontológicas devido à sua cor branca/perolada opaca e resistência mecânica. Estas próteses são confeccionadas por usinagem com apoio de um software de CAM (Computer Aided Manufacturing), a partir de blocos prensados e pré-sinterizados. A pré-sinterização consiste em aquecer os blocos compactados a altas temperaturas, com uma taxa lenta de aquecimento até o início da formação dos pescoços entre as partículas, quando proporciona dureza/resistência e usinabilidade. Uma contradição, pois a dureza/resistência mecânica é necessária para proporcionar estabilidade as forças de corte, mas se muito duro, pode dificultar a usinagem então se deve encontrar uma faixa de compromisso de temperatura entre estabilidade e usinabilidade. Dessa forma, o objetivo do presente trabalho foi investigar a relação entre a microdureza e temperatura de pré-sinterização da zircônia Y-TZP e seu comportamento ao ser submetido à usinagem. O ensaio de microdureza foi escolhido como representante de resistência mecânica por ser não destrutivo e de resultado imediato. O pó de zircônia experimental foi submetido à prensagem uniaxial seguido de prensagem isostática a frio à 200 MPa e pré-sinterização entre 900°C e 950°C. Os blocos foram cortados e submetidos ao teste de estabilidade na usinagem e ensaio de microdureza Vickers sendo os dados submetidos ao teste de “normalidade” de Anderson-Darlin com p > 0,05. Foi utilizada ANOVA de um fator com o teste de Tukey-Kramer para verificar as diferenças entre as médias dos grupos. A investigação demonstrou que a diferença de 50°C na temperatura de pré-sinterização, acima de 900°C afetou significativamente a microdureza, contudo os tempos de patamar 2 e 4 horas não a influenciou significativamente. A maior temperatura de pré-sinterização dos grupos experimentais testados possibilitou um melhor comportamento na usinagem com o apoio de um software CAM, sendo a microdureza similar ao material comercial ZL.

ABSTRACT Y-TZP zirconia is widely used in the manufacture of coping as a structural material for dental prosthesis due to its opaque white/pearl color and mechanical strength. Dentures are made by machining with cam (computer aided manufacturing) software support, from pressed and pre-sintered blocks. Pre-sintering consists of heating the compressed blocks to high temperatures, with a slow heating rate until the neck formation among particles, when this provides hardness/strength and machinability. There is a contradiction, because the mechanical hardness/strength is necessary to provide stability to the cutting forces, but if it is very hard, machining can be difficult, therefore must be found a compromise zone of temperature between stability and machinability. In this way, the purpose of this study was to investigate the relationship between microhardness and the pre-sintering temperature of experimental Y-TZP zirconia and its behavior to be subjected to machining. The microharness testing was chosen as representative of mechanical strength once it is nondestructive and with immediate result. The experimental zirconia powder was subjected to uniaxial pressing, subsequently cold isostatic pressing of 200 MPa and pre-sintering between 900°C and 950°C. Blocks were cut and subjected to machining stability testing and vickers microhardnes testing which the data were subjected to the anderson-darlin (p > 0.05) test for “normality”. Anova's “one way” with tukey-kramer test was used to verify the differences among the means of groups. The investigation showed that the difference of 50°C in pre-sintering temperature above 900°C significantly affect the hardness, whereas 2 to 4 hour time did not significantly affect material microhardness. The highest pre-sintering temperature of the tested experimental groups enabled better performance in machining with cam software support, which provides similar microhardness to commercial ZL material.

Os esforços de corte durante o torneamento de tarugos de alumina à verde e sua correlação com aspectos superficiais da peça foram estudados em condições experimentais. A correlação entre a força de usinagem e a taxa de remoção de material é um parâmetro importante na definição do projeto de produtos cerâmicos, já que, parâmetros inadequados produzem danos superficiais inaceitáveis na peça. O presente estudo analisou os esforços de corte obtidos durante o torneamento de peças de alumina com 99,8% de pureza no seu estado verde e monitorou a influência da profundidade de corte nestes; utilizando-se ferramentas de corte de cermet sob condições constantes de usinagem. Os esforços de corte foram relacionados com os acabamentos superficiais, desgastes nas ferramentas e temperaturas das ferramentas durante a usinagem. Verificou-se que a profundidade de corte não afetou consideravelmente a qualidade das superfícies. Entretanto, ensaios preliminares para seleção das condições de corte, mostraram que velocidades de corte e avanços inadequados geram danos à superfície da peça. Assim, a melhor condição de corte foi a de maior profundidade de corte, 1,0 mm, uma vez que, com profundidades de corte menores aumenta-se o número de passes necessários para remoção do sobre material da peça, o que inevitavelmente leva a maior desgaste da ferramenta, maior força de usinagem e pior acabamento superficial. Destaca-se que a alumina em seu estado verde apresentou elevado efeito abrasivo sobre a ferramenta durante o torneamento. A sinterização da peça produzida na melhor condição de corte indicou que a qualidade do acabamento na superfície verde foi mantida.

In experimental conditions, cutting forces were studied during turning of green alumina billets, including their correlation with surface aspects of the workpiece. The correlation between cutting power and the removal rate are important parameters for defining the design of ceramic products, since inadequate parameters can produce excessive surface damage to the workpiece. This study examined the forces obtained during turning of alumina workpieces with 99.8% purity in their green state, by means of a three-point dynamometer, evaluating the cutting, feed and depth forces, using a cermet tool under constant machining conditions. Variables were compared with the forces, including surface finish, tool wear and temperature during machining. In the study, it was found that the depth of cut had no significant effect on the surface quality, and the cutting speed and feed influencing the finish. However, preliminary tests for selecting the cutting conditions showed that unsuitables cutting speeds and feeds generate severe damage to the workpiece surface. The best condition was 1.00 mm depth of cut, and the forces increasedfor with each pass performed, with the feed force the variable with greatest increases in relation to the cutting and depth forces, and wear of the cutting tool directly influenced the surface finish, generated by the highly abrasive nature of the alumina particles of the green compact. It is emphasized that the alumina in its green state showed high abrasive effect on the cutting tool during the turning process and the surface finishing of the green workpiece had a direct influence on the sintered workpiece.

This study presents an innovative and original biomaterial designed to substitute for articular cartilage and mimic its mechanical behavior, including elastic cushioning and the characteristics of fiber-reinforced gel. The material was composed of polyurethane and bioglass microfiber 45S5. It was designed to present a tribological surface to the cartilage of the tibial plateau, and to convert over a functional gradient to an osteointegrable region for self-anchorage to the subchondral bone. The biomaterial samples showed no toxicity and promoted cell spreading. Subsequent in vivo studies in rabbits demonstrated the formation of a rigid structure similar to bone trabeculae in the distal region of the tribological surface of the implant. The tribological surface of the proximal region showed a fibrocartilaginous tissue with highly vascularized chondrocytes, thus validating the proposed concept for the design of the implant incorporating a functional gradient and auto-stability.

Cerâmicas avançadas para aplicações estruturais estão presentes em componentes de engenharia submetidos a solicitações complexas. Tal combinação única de propriedades torna essas cerâmicas solução sem paralelo para seleção de materiais em casos especiais. Uma seleção de materiais não pode contudo ser feita independentemente da escolha de processos de fabricação, forma e custo. A determinação de uma metodologia para a avaliação do grau de confiança dos componentes cerâmicos sinterizados é tão importante quanto as técnicas de seleção e de processamento. Este trabalho apresenta as tendências recentes na aplicação de cerâmicas estruturais avançadas, na conformação a frio por prensagem isostática e moldagem por processos de injeção, a elaboração de uma metologia para avaliação de desempenho e escolha de processos de corformação relacionados com propriedades mecânicas, microestrutura e desgaste por atrito sem lubrificante.

Advanced ceramics for structural applications are present in engineering parts subjected to complex solicitations. Such unique combination of properties makes these ceramics the unique solution for material selection in special cases. However a material selection cannot be made independently of the choice of manufacturing processes, shape and cost. The determination of a methodology for the evaluation of the sintered ceramic parts reliability is as important as the selection and processing techniques. This work presents the recent trends in the structural advanced ceramics application, the cold forming isostatic pressing and injection processes molding, the elaboration of a methodology for the performance evaluation and choice of forming processes related with the mechanical properties, microstructure and unlubricated sliding wear.