Prediction of Friction Stir Welding effects on AA2024-T3 plates and stiffened panels using a shell-based finite element model

Manufacturing-induced effects significantly affect in-service behaviour of welded structures, such as integrally stiffened panels for aeronautic applications. Being a complex phenomenon with several variables involved, the assessment of the effects coming from welding usually relies on numerical simulations. Here, a novel shell-based finite element model is proposed to accurately simulate the transient thermal fields and stress-strain distributions resulting from friction stir welding (FSW) processes. The capability of the model to predict (i) residual stresses, (ii) material softening and (iii) geometric distortion of the welded parts is assessed by the modelling and simulation of FSW applied on aluminium integrally stiffened panels

Modelling of friction stir welding and its influence on the structural behaviour of aluminium stiffened panels

This work deals with the modelling and numerical simulation of aluminium stiffened panels, assembled by means of friction stir welding (FSW) operations, and subjected to compressive loads that can catastrophically induce buckling (global or local) unstable modes and, subsequently, overall failure. Due to their geometrical complexity, added to localized thermo-mechanical effects that typically come from joining by welding, approximation methods such as the Finite Element Method are typically used in such nonlinear analyses, having proved to be useful to designers focused on the prediction of the behaviour (before and post buckling) of such structures. Being grounded on previous contributions from the authors, the present paper aims to bring a number of innovative aspects to the current state of the art by considering in the developed models the simultaneous influence of residual stress fields, material softening effects and geometrical imperfections. Doing so, it is possible to infer about the singular and combined influence of these effects in the overall structural performance of stiffened panels, building up a useful and comprehensive methodology for design stages

Numerical simulation of the buckling behaviour of stiffened panels: Benchmarks for assessment of distinct modelling strategies

This work deals with the effective modelling and simulation of the behavior of stiffened panels, when subjected to compressive (buckling) loads. Within the Finite Element Method, two numerical strategies are compared, namely the Riks method and the displacement incremental control method, including damping effects. The capabilities and limitations of both approaches are explored for two distinct benchmarks: a panel with a blade stiffener, and a panel with a T shaped stiffener. In both cases, material (plasticity) and geometrical (large displacements) nonlinearities are considered, together with a modelling strategy based on shell elements. Following previous works of the authors, each panel accounts for initial geometric imperfections coming from friction stir welding joining operations. The paper shows a number of considerations that must be undertaken when choosing between one of the two modelling strategies. Both benchmarks involve a number of challenges from the point of view of modelling unstable structural behaviors, and therefore the proposed benchmarks can represent a valid set of case studies in the understanding of the capabilities of current numerical simulation codes

Desenvolvimentos recentes no domínio da conexão aço concreto no contexto das estruturas mistas

Este trabalho apresenta desenvolvimentos recentes sobre conexão aço-concreto para estruturas mistas. Os estudos realizados envolvem campanhas experimentais com diversos tipos de conectores de cisalhamento, utilizando-se concreto normal e concretos leves de alta resistência. A caracterização do comportamento das conexões tem sido realizada através de ensaios tipo push-out. Os resultados experimentais recentemente obtidos são comparados com resultados de outros autores. Os resultados das pesquisas que vêm sendo realizadas indicam uma boa perspectiva de utilização de novos conectores de cisalhamento no contexto das estruturas mistas de aço e concreto.This work presents recent developments on steel-concrete connection in composite structures. The accomplished studies involve experimental programs with various types of shear connectors, using normal weight, as well as lightweight concrete. The behaviour of shear connectors has been assessed through push-out tests. The experimental results recently obtained are compared with results from other authors. The results of the research programme that has been carried out in the last few years show good perspective for the use of new types of shear connectors in steel-concrete composite structures

Design and experimental analysis of a new shear connector for steel and concrete composite structures

This work presents the design of a new shear connector and the corresponding results obtained on push-out tests. This new shear connector consists on a steel rib with indented cut shape that provides resistance to longitudinal shear and prevents transversal separation between the concrete slab and the steel profile (uplift). Adding to this, the connector openings cut makes easier the arrangement of transversal reinforcement bars. The installation of the connectors is simple and requires only common welding procedure. Due to its load capacity, the indented connector is able to replace a group of stud bolts. Its structural behaviour is analyzed and compared with other existing connectors, like the stud bolt and the Perfobond. The influence of different geometrical and mechanical aspects on the ultimate load capacity and ductility is assessed. The performed studies indicate that the proposed indented connector presents a good mechanical performance, associated with constructive and economical advantages.(undefined

Análise experimental de um conector de cisalhamento em chapa de aço endentada para estruturas mistas de aço e concreto

Este trabalho apresenta o projeto e os resultados de ensaios tipo push-out de um novo conector de cisalhamento constituído por uma chapa de aço endentada. O conector proposto possui saliências e reentrâncias trapezoidais que proporcionam resistência ao cisalhamento longitudinal e previnem a separação transversal entre o perfil metálico e a laje de concreto (uplift). Além disso, as aberturas no conector facilitam a disposição das barras de armadura. A capacidade da conexão pode ser variada em função tanto da armadura transversal ao conector como da resistência do concreto. A instalação dos conectores é simples, podendo ser feita com solda comum, sem a necessidade de equipamentos especiais no canteiro de obras. Devido à sua resistência última, um conector em chapa endentada pode substituir um número significativo de conectores tipo pino com cabeça (stud). O comportamento do novo conector foi analisado e comparado com o de conectores existentes, no caso o Perfobond e o stud, no que se refere à capacidade última e à ductilidade da conexão, avaliando a influência de diversas características geométricas e mecânicas. Os estudos realizados indicam que o conector em chapa endentada proposto apresenta um comportamento adequado associado a diversas vantagens construtivas e econômicas

Clinical, dermoscopic and histopathological evaluation of the Meyerson nevus: case report

O nevo de Meyerson ocorre quando uma rara erupção eczematosa focal e transitória surge ao redor de lesões melanocíticas. O mesmo fenômeno também foi observado em lesões não melanocíticas. O caso relatado é o de um doente masculino, 25 anos, que há dois meses notara surgimento de eritema e prurido, circundando dois nevos, localizados no abdome. As lesões eram atípicas à dermatoscopia e procedeu-se à excisão cirúrgica dos dois nevos. O exame histopatológico revelou nevos melanocíticos compostos displásicos, envolvidos por espongiose e vesículas intraepidérmicas. O presente relato sugere que o fenômeno de Meyerson não modifica as características dermatoscópicas dos nevos.Meyerson nevi occur whenever a rare focal and transitory eczematous eruption arises around melanocytic lesions. The same phenomenon has also been observed in non-melanocytic lesions as well. Herein we report the case of a 25 year old, male patient, who had noticed, two months before, the arising of a pruriginous and erithematous halo around two nevi localized on his abdomen. The lesions were found to be atypical on dermoscopic examination and he was submitted to surgical excision of both nevi. Histopathological examination revealed displastic compound melanocytic nevi, surrounded by intraepidermical vesicles and spongiosis. Present report suggests that Meyerson phenomenon does not seem to alter dermoscopic features of nevi

Drosophilidae (Diptera) associados a fungos: uso diferenciado de recursos em áreas antrópicas e de Mata Atlântica

This study investigates the Drosophilidae species associated to fruiting bodies of fungi in forested and anthropized environments of the Atlantic Rain Forest Biome, in south and southeastern Brazil. We collected samples of imagoes flying over and emerging from fruiting bodies of species of five fungi families, in six collection sites. We obtained 18 samples, from which emerged 910 drosophilids of 31 species from the genera Drosophila Fallen, 1823, Hirtodrosophila Duda, 1923, Leucophenga Mik, 1886, Mycodrosophila Oldenberg, 1914, Scaptomyza Hardy, 1849, Zaprionus Coquillett, 1901 and Zygothrica Wiedemann, 1830. The Drosophila species collected on fungi, as well as Zaprionus indianus Gupta, 1970, had previously been recorded colonizing fruits, demonstrating their versatility in resource use. Most of these species belong to the immigrans-tripunctata radiation of Drosophila. Our records expands the mycophagous habit (feeding or breeding on fungi) to almost all species groups of this radiation in the Neotropical region, even those supposed to be exclusively frugivorous. Assemblages associated to fungi of forested areas were more heterogeneous in terms of species composition, while those associated to fungi of anthropized areas were more homogeneous. The drosophilids from anthropized areas were also more versatile in resource use.Foi realizado um estudo das espécies de Drosophilidae associadas aos corpos de frutificação de fungos em ambientes florestais e antrópicos no Bioma Mata Atlântica, no sul e sudeste do Brasil. Foram realizadas coletas de adultos sobrevoando e emergindo de corpos de frutificação de espécies de fungos de cinco famílias, em seis pontos de coleta. Foram obtidas 18 amostras, onde foram coletados 910 indivíduos de 31 espécies, pertencentes aos gêneros Drosophila Fallen, 1823, Hirtodrosophila Duda, 1923, Leucophenga Mik, 1886, Mycodrosophila Oldenberg, 1914, Scaptomyza Hardy, 1849, Zaprionus Coquillett, 1901 e Zygothrica Wiedemann, 1830. As espécies de Drosophila coletadas, assim como Zaprionus indianus Gupta, 1970, já haviam sido registradas em frutos, evidenciando sua versatilidade na utilização dos recursos. A maioria destas espécies pertence à radiação immigrans-tripunctata de Drosophila. Em espécies desta radiação que habitam regiões temperadas, a micofagia é amplamente difundida; nossos registros (de sítios de alimentação e oviposição em fungos) expandem este hábito para quase todos os grupos de espécies desta radiação na região Neotropical, mesmo aquelas que se supunham ser exclusivamente frugívoras. As assembléias colonizadoras dos corpos de frutificação variaram entre as espécies de fungos e com o tipo de ambiente em que eles se desenvolviam, onde as espécies de drosofilídeos generalistas utilizam os fungos em ambientes mais degradados.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Apoio da Universidade Federal do Rio Grande do Su

Seguimento a Longo Prazo da Ablação de Arritmias Ventriculares com Origem na Câmara de Saída Ventricular Baseada em Mapeamento Não Contacto por Balão Multi-Elétrodos

Introduction: The outflow tract (OT) regions of the ventricles are a common location of origin for idiopathic ventricular arrhythmias (VA). Non-contact mapping (NCM) with a multi-electrode balloon catheter Ensite-Array enables three-dimensional reconstruction of the geometry of the cardiac chambers and accurate mapping of the propagation map, based on a single beat analysis, facilitating the ablation and contributing procedure success. Objective: Assessment of the feasibility and long-term outcomes following NCM-guided OT VA ablation. Methods: Single center retrospective analysis of patients admitted for symptomatic OT VA ablation. Demographic and clinical characteristics of patients, procedure data and long-term outcomes were assessed. Results: Fifty-eight patients (79.3% female, age 43.9±17.6 years) were considered, 89.7% without structural heart disease. In 85.7% of the cases left ventricle ejection fraction (LVEF) was preserved (LVEF≥50%), 8.6% had mild systolic dysfunction (LVEF 40%-49%) and 5.7% had moderate systolic dysfunction (LVEF 30%-39%). Twenty-four-hour Holter recording documented sustained VA episodes in 12.1% of the patients, non-sustained VA in 31.0%, and >10 000 premature ventricular complex (PVC)/24 h in 56.9%, with an ECG suggesting right ventricular OT origin in 84.5%. There was total elimination of PVC in 87.9% cases and a significant reduction in 3.4%. During a mean follow-up of 5.5 years, 87.9% patients remained asymptomatic without medication, 12.1% underwent re-ablation due to symptomatic PVC recurrence, and two cases underwent a third successful intervention. Conclusion: Non-contact mapping-guided multi-electrode balloon catheter VA ablation is a highly effective and safe procedure, with a low rate of long-term recurrence.info:eu-repo/semantics/publishedVersio

Avaliação do desempenho de um conector de cisalhamento em chapa dentada para estruturas mistas de aço e concreto

Este trabalho apresenta uma avaliação do comportamento de um conector de cisalhamento em chapa dentada, denominado Crestbond, para sistemas de pisos mistos, a partir dos resultados de 40 ensaios push-out. Avalia-se a capacidade de carga da conexão, sua ductilidade e os modos de colapso observados, considerando-se o efeito de diversas variáveis. Os resultados demonstram que o conector proposto apresenta um comportamento adequado, com alta rigidez para cargas de serviço e boa ductilidade em estado limite último, constituindo uma alternativa a conectores de cisalhamento como o stud bolt e o Perfobond