High‐Pressure Torsion: Experiments and Modeling

The high‐pressure torsion (HPT) process has been the subject of many investigations as a new method of processing for nanostructured materials due to its ability to develop nanostructures with high‐angle grain boundaries. This chapter examines the various publications describing the experimental studies of the effect of HPT on the mechanical behaviors and alterations of microstructural features in applications to various pure and alloyed metals. Moreover, an overview of the modeling approaches developed through the last decade, considering the main advantages/limitations, is analyzed

Fractura de juntas coladas

Mestrado em Engenharia MecânicaAs juntas coladas têm actualmente um vasto campo de aplicações, que vai desde a indústria das embalagens até à exigente indústria aeronáutica. No entanto, a inexistência de critérios de dimensionamento rigorosos constitui ainda um obstáculo importante à generalização de aplicações estruturais. O objectivo principal deste trabalho foi por isso avaliar os factores que mais influenciam a resistência de juntas coladas de sobreposição. Para tal, foram realizados diversos ensaios de juntas de chapas de aço inoxidável, coladas com dois adesivos epoxídicos e com um adesivo acrílico. O programa de trabalho incluiu ensaios de fractura de modo I “Double Cantilever Beam”, ensaios de tracção de juntas de sobreposição simples, bem como ensaios de juntas de sobreposição dupla à tracção e à compressão. A espessura das chapas e os comprimentos de sobreposição foram variáveis e, em alguns casos, foram criados deliberadamente defeitos nas extremidades dos provetes. A comparação entre as simulações numéricas por Elementos Finitos e os resultados experimentais permitiu concluir que o nível de tensões de tracção nos bordos é o principal factor que afecta a resistência das juntas. Isto exige o desenvolvimento de critérios de rotura que tenham em conta a natureza local da resistência do adesivo, em virtude do pequeno volume de material sujeito às tensões críticas. Verificou-se também que, quando expressas em função do comprimento de sobreposição efectivo, descontado das fendas, as resistências eram geralmente pouco sensíveis à presença de defeitos.Adhesive joints are nowadays widely used in fields ranging from packaging to aeronautics. Nevertheless, the absence of accurate failure criteria remains an important obstacle that often prevents the use of adhesive joints in structural applications. The main objective of the present work was to evaluate the most relevant factors that affect the strength of adhesive joints. This work focused on stainless steel joints, bonded with two epoxy and one acrylic adhesives. The test programme included Mode I Double Cantilever Beam fracture tests, lap-shear tensile tests single-lap joints, as well as lapshear tensile and compressive tests on double-lap joints. The adherend thickness and joint overlap lengths were varied, while, in some cases, defects were deliberately inserted near the bondline edges. The comparison between Finite Element and experimental results showed that the strength of adhesive joints was essentially dependent on the level of nearthe- edge peel stresses. Therefore, “in-situ” strength based criteria will be necessary to predict the strength of adhesive joints, because of the small volume of material under critical stresses. If expressed in terms of effective overlaps, the joint strengths were, in general, not significantly affected by the presence of near-the-edge defects

Fractura interlaminar de compósitos de matriz polimérica

Os compósitos de matriz polimérica são actualmente utilizados num vasto campo de sectores de actividade, que vão desde a electrónica de grande consumo até às indústrias aeronáutica e espacial. Apesar dos progressos conseguidos, subsistem alguns obstáculos à generalização das aplicações estruturais de compósitos, associados aos elevados custos dos materiais e à complexidade do comportamento mecânico. Na realidade, devido a lacunas no conhecimento dos mecanismos de dano e de ruína, há um enorme potencial de optimização de estruturas compósitas. Um dos modos de dano mais perigoso dos laminados compósitos de alto desempenho é a delaminagem. Após inúmeros estudos publicados, estão disponíveis normas que permitem caracterizar a resistência à delaminagem de compósitos unidireccionais. Porém, na grande maioria das aplicações estruturais usam-se laminados multidireccionais e as delaminagens tendem a formar-se entre camadas de diferentes orientações. O objectivo principal deste trabalho foi por isso caracterizar a resistência à delaminagem de laminados multidireccionais, nomeadamente avaliar a influência da orientação das camadas adjacentes à delaminagem. Atendendo à importância prática das solicitações e dos materiais, foram realizados ensaios de modo I “double cantilever beam” (DCB), de modo II “end-notched flexure” (ENF) e de modo misto I+II “mixed mode bending” (MMB), em provetes vidro/epóxido e carbono/epóxido. Os provetes escolhidos tinham interfaces de delaminagem dos tipos 0/θ e θ/−θ, sendo θ variável entre 0 e 90 graus. A componente experimental foi amplamente suportada por modelação tridimensional com elementos finitos. Os resultados mostraram ser possível evitar fenómenos espúrios de dano intralaminar em ensaios de modo II. Todavia, em modo I, foi frequentemente possível medir apenas taxas críticas de libertação de energia, GIc, de iniciação. Por outro lado, verificou-se que à interface 0/0 corresponderam geralmente os menores valores de GIc e GIIc, e que a interface de delaminagem afectou mais esta última. Finalmente, em modo misto I+II, Gc variou de forma aproximadamente linear com a fracção de modo II, GII/G, embora se tenha constatado alguma ambiguidade na partição de modos em provetes carbono/epóxido.Polymer matrix composites are nowadays widely used in a vast range of applications, from consumer electronics to aircraft and aerospace industries. However, in spite of the enormous progress, the spreading of structural applications still faces obstacles associated to high material costs and complex mechanical behaviour. In fact, the present unability to master composite damage mechanics leaves an enormous potential for optimization of composite structures. Delamination is considered one of the most dangerous damage modes of high performance laminated composites. Following numerous published studies, standards are currently available for the measurement of the delamination resistance of unidirectional laminates. However, the vast majority of structural applications involves multidirectional laminates and delaminations are seen to occur between differently oriented plies. The main objective of this work was therefore to characterise the delamination resistance of multidirectional laminates. The emphasis was on evaluating the effect of the orientation of delaminating plies on toughness. In view of the practical importance of the loadings and materials, mode I “double cantilever beam” (DCB), mode II “end-notched flexure” (ENF) and mixed-mode I+II “mixed mode bending” (MMB) tests were performed on glass/epoxy and carbon/epoxy laminates. Selected specimens had delaminations in 0/θ and θ/−θ type interfaces, θ varying between 0 and 90 degrees. The experimental component was supported by extensive threedimensional finite element modelling. The results showed it was possible to avoid spurious intraply damage phenomena in mode II tests. However, it was frequently only possible to measure mode I critical strain energy release rates, GIc, for initiation. On the other hand, it was seen that the 0/0 interface had the lowest GIc and GIIc values. Moreover, the latter was more sensitive to the delamination interface. Finally, under mixed-mode I+II, Gc varied quasi linearly with the mode II ratio, GII/G, although there was some mode partitioning ambiguity in carbon/epoxy specimens

Recent Advances in Welding

Welding is a conventional joining process that has followed the recent developments in other manufacturing processes, continuing to be an extremely used and investigated process. Several technologies developed in other areas of knowledge have converged in the area of welding, allowing significant improvements in the quality of the products obtained and in the increased productivity of the processes. Although some techniques have been implemented and studied for several decades, the interest of researchers in welding has not diminished, as it can be seen through new processes that have emerged, such as Friction Stir Welding, in addition to many other notable developments in welding processes which apparently seemed to have reached their final stage of maturity. This work brings together a set of very interesting works, being a living proof that welding continues to be heavily investigated and that the developments around this manufacturing process are constantly emerging. Because the materials continue to evolve and the technology around welding also continues to develop at a very good pace, studies on the weldability of new materials and the application of new techniques and technologies to already well known welding processes does not stops happening. The editors are proud to have collected this set of works that can help scholars and researchers to broaden their knowledge in the field of welding, thus contributing to the creation of a knowledge base that allows researchers to start new investigations and achievements in the coming decades.info:eu-repo/semantics/publishedVersio

Effect of Scan Strategies and Use of Support Structures on Surface Quality and Hardness of L-PBF AlSi10Mg Parts

Additive manufacturing allows for a great degree of design freedom and is rapidly becoming a mainstream manufacturing process. However, as in all manufacturing processes, it has its limitations and specificities. Equipping engineers with this knowledge allows for a higher degree of optimization, extracting the most out of this technology. Therefore, a specific part design was devised and created via L-PBF (Laser Powder Bed Fusion) using AlSi10Mg powder. Certain parameters were varied to identify the influence on material density, hardness, roughness, residual stress and microstructures. It was found that on heat treated parts laser pattern strategy is one of the most influential aspects, showing that chessboard and stripes 67° improved outcome; average Ra roughness varied between 8–12 µm, residual stress was higher on vertical surfaces than horizontal surfaces, with the combination of support structures and stripes 67° strategies generating the lowest residual stress (205 MPa on a lateral/vertical face), hardness was non-orientation dependent and larger on samples with chessboard fabrication strategies, while microstructures were composed of α–Al dendrites surrounded by Si particles. The distribution and grain size of the microstructure is dependent on location regarding melt pool and HAZ area. Furthermore, Al–Mg oxides were encountered on the surface, along with pores generating from lack of fusion.The authors would like to acknowledge the Hypermetal Additive Manufacturing for their contribution with some additive manufactured samples and materials, as well as ONA Electro-Erosión Lda. for the use of their electro erosion cutting equipment, used for the separation of certain samples from the build plate. The Authors also would like to thanks to Rui Rocha from CEMUP, due to his sharp critical analysis of SEM results and his help in achieving the best SEM pictures. A.B.P would like to acknowledge the projects UIDB/00481/2020 and UIDP/00481/2020—FCT—Fundação para a Ciencia e a Tecnologia; and CENTRO-01-0145-FEDER-022083—Centro Portugal Regional Operational Programme (Centro2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund.info:eu-repo/semantics/publishedVersio

The influence of ACE ID and ACTN3 R577X polymorphisms on lower-extremity function in older women in response to high-speed power training

Background: We studied the influence of the ACE I/D and ACTN3 R577X polymorphisms (single or combined) on lower-extremity function in older women in response to high-speed power training. Methods: One hundred and thirty-nine healthy older Caucasian women participated in this study (age: 65.5 ± 8.2 years, body mass: 67.0 ± 10.0 kg and height: 1.57 ± 0.06 m). Walking speed (S10) performance and functional capacity assessed by the “get-up and go” (GUG) mobility test were measured at baseline (T1) and after a consecutive 12-week period of high-speed power training (40-75% of one repetition maximum in arm and leg extensor exercises; 3 sets 4–12 reps, and two power exercises for upper and lower extremity). Genomic DNA was extracted from blood samples, and genotyping analyses were performed by PCR methods. Genotype distributions between groups were compared by Chi-Square test and the gains in physical performance were analyzed by two-way, repeated-measures ANOVA. Results: There were no significant differences between genotype groups in men or women for adjusted baseline phenotypes (P > 0.05). ACE I/D and ACTN3 polymorphisms showed a significant interaction genotype-training only in S10 (P = 0.012 and P = 0.044, respectively) and not in the GUG test (P = 0.311 and P = 0.477, respectively). Analyses of the combined effects between genotypes showed no other significant differences in all phenotypes (P < 0.05) at baseline. However, in response to high-speed power training, a significant interaction on walking speed (P = 0.048) was observed between the “power” (ACTN3 RR + RX & ACE DD) versus “non-power” muscularity-oriented genotypes (ACTN3 XX & ACE II + ID)]. Conclusions: Thus, ACE I/D and ACTN3 R577X polymorphisms are likely candidates in the modulation of exercise-related gait speed phenotype in older women but not a significant influence in mobility traits.The study was developed with the aid of a research fellowship, reference number SFRH/BD/47114/2008, funded by POPH – QREN, shared by the European Social Fund and the national funds of MCTES. This work was supported in part by the Spanish Department of Health and Institute Carlos III of the Government of Spain [Spanish Net on Aging and frailty; (RETICEF)] and Economy and Competitivity Department of the Government of Spain, under grants numbered RD12/043/0002, and DEP2011-24105, respectively

New insights into a bacterial metabolic and detoxifying association responsible for the mineralization of the thiocarbamate herbicide molinate

A novel pathway of molinate mineralization promoted by a defined mixed culture composed of five bacteria (named ON1 to ON5) was proposed previously. Evidence was obtained of a metabolic association between Gulosibacter molinativorax ON4T, capable of molinate breakdown, and the remaining bacteria. In the present study, the role of each isolate in that metabolic association was further explored and the possible synergistic effect of all the bacterial isolates for the stability of the mixed culture is discussed. The cleavage of the molinate thioester bond, whether occurring under aerobic or anaerobic conditions, releases ethanethiol (S-ethyl moiety) and an azepane moiety derivative, identified as azepane-1-carboxylic acid. This azepane moiety is degraded, in the presence of oxygen, by Pseudomonas strains ON1 and ON3 and G. molinativorax ON4T. Ethanethiol, which inhibits G. molinativorax ON4T, is consumed by Pseudomonas strain ON1 and Stenotrophomonas maltophilia ON2. Although a two-member mixed culture of G. molinativorax ON4T and Pseudomonas strain ON1 was able to promote the aerobic mineralization of molinate, after 20 successive transfers of the five-member mixed culture in mineral medium with molinate, none of these isolates were lost. The results obtained indicate that the whole mixed culture may have a higher fitness than the two-member culture, even when the basic degradative and cross-protection functions are assured

Mycobacterium tuberculosis associated with severe tuberculosis evades cytosolic surveillance systems and modulates IL-1β production

Genetic diversity of Mycobacterium tuberculosis affects immune responses and clinical outcomes of tuberculosis (TB). However, how bacterial diversity orchestrates immune responses to direct distinct TB severities is unknown. Here we study 681 patients with pulmonary TB and show that M. tuberculosis isolates from cases with mild disease consistently induce robust cytokine responses in macrophages across multiple donors. By contrast, bacteria from patients with severe TB do not do so. Secretion of IL-1β is a good surrogate of the differences observed, and thus to classify strains as probable drivers of different TB severities. Furthermore, we demonstrate that M. tuberculosis isolates that induce low levels of IL-1β production can evade macrophage cytosolic surveillance systems, including cGAS and the inflammasome. Isolates exhibiting this evasion strategy carry candidate mutations, generating sigA recognition boxes or affecting components of the ESX-1 secretion system. Therefore, we provide evidence that M. tuberculosis strains manipulate host-pathogen interactions to drive variable TB severities

Epidemiology of Psoriasis in Portugal: A Population-Based Study

Introduction: Psoriasis is a common, chronic, and inflammatory skin disorder with a high personal, social and economic burden and important implications for healthcare systems. The aim of this study was to provide an epidemiological characterization of individuals with psoriasis in Portugal. Material and Methods: A large observational, cross-sectional, nationwide, population-based survey study developed by the Portuguese Psoriasis Group of the Portuguese Society of Dermatology and Venereology (GPP-SPDV). A structured questionnaire was designed and applied by experienced interviewers to a random, representative sample of Portuguese individuals with psoriasis and/or psoriatic arthritis. Patients were considered to have psoriasis if they replied positively to one of the following questions: “Does any physician have ever diagnosed you with psoriasis?” or “Do you have a skin disorder characterized by scaling, reddish skin lesions located in the elbows/knees/scalp?”. Results: A total of 6381 individuals were interviewed, of which 283 met the criteria for psoriasis, corresponding to a prevalence rate of 4.4% (95% CI 3.95 – 4.98). Out of the participants that met psoriasis criteria, 24% had suggestive signs/symptoms but did not have a clinical diagnosis established and were not being monitored by a physician. Although more than 70% of participants had active disease (scaling, erythema, or pruritus) and one third had joint symptoms, only 12% were on systemic treatment. Fifty percent of participants with psoriasis (n = 139) had relevant comorbidities (most frequently depression/anxiety and cardiometabolic diseases). Sixteen percent of participants with psoriasis (n = 46) reported that psoriasis interfered with their daily activities (median impact of 5 in a 0 – 10 scale) and 12% mentioned the disease had an impact in their sexual life (median impact of 5 in a 0 – 10 scale). Conclusion: The results of this study suggest that the prevalence rate of psoriasis is likely to be high in Portugal, and several gaps exist at different levels of healthcare delivery to these patients, from diagnosis to treatment. This study provides important data for the future planning of interventions targeting the improvement of psoriasis care in Portugal