Experimental and numerical analysis of the influence of burst pressure distribution on rapid free sheet forming by vaporizing foil actuators

Vaporizing Foil Actuators (VFA) can be employed as an innovative, extremely fast sheet metal forming method. An ultimate goal in forming technologies is generally to be flexible and rely on as few part-specific tools as possible. Therefore, various realizable VFA pressure distributions were investigated with a focus on the free forming result. Fundamental experiments including laser-based dynamic velocity measurements were conducted to discuss some key forming characteristics of the process. To compare more complex pressure distributions in a well-defined way, a numerical model was built. The strain rate dependency of the blank material was identified experimentally and incorporated in the model. It is shown that there are some VFA free forming capabilities in terms of creating certain part shapes, but only to a limited degree because relevant inertial forces can be present in regions where displacements would actually be either undesirable or wanted. Potential solutions to this are given at the end

Part-optimized forming by spatially distributed vaporizing foil actuators

Electrically vaporizing foil actuators are employed as an innovative high speed sheet metal forming technology, which has the potential to lower tool costs. To reduce experimental try-outs, a predictive physics-based process design procedure is developed for the first time. It consists of a mathematical optimization utilizing numerical forming simulations followed by analytical computations for the forming-impulse generation through the rapid Joule heating of the foils. The proposed method is demonstrated for an exemplary steel sheet part. The resulting process design provides a part-specific impulse distribution, corresponding parallel actuator geometries, and the pulse generator’s charging energy, so that all process parameters are available before the first experiment. The experimental validation is then performed for the example part. Formed parts indicate that the introduced method yields a good starting point for actual testing, as it only requires adjustments in the form of a minor charging energy augmentation. This was expectable due to the conservative nature of the underlying modeling. The part geometry obtained with the most suitable charging energy is finally compared to the target geometry

Umformung mittels vaporisierender Aktuatoren: Experimente und Modellierung

Bei der dynamischen Blechumformung mittels vaporisierender Aktuatoren wird versucht die gewaltvolle Expansion einer metallischen Folie zu nutzen, die entsteht, wenn ein hoher Kondensatorentladestrom diese binnen kürzester Zeit bis in die Gasphase erhitzt. Zwar sind für diesen durchaus flexiblen Prozess einige Anwendungen und experimentelle Grundlagenuntersuchungen bekannt, einen allgemeinen makroskopischen Modellierungsansatz gab es bisher jedoch noch nicht. Deshalb werden in dieser Arbeit derartige Ansätze erarbeitet, die sowohl das physikalische Prozessverständnis erhöhen als auch eine vollständige Prozessauslegung ermöglichen. Dazu werden zwei aufeinanderfolgende Teilprozesse getrennt betrachtet; zuerst die elektrische Energieeinbringung in den Folienaktuator bis zum sogenannten Berstpunkt, dann die eigentliche mechanische Werkstückumformung. Um letztlich eine rein prediktive Berechnung zu gewährleisten, werden zunächst Experimente durchgeführt, die v. a. die Etablierung eines Aktuatorwerkstoffgesetzes ermöglichen, das jegliche Prozessparametereinflüsse auf die erreichbare Energieeinbringung widerspiegeln kann. Nach einer diesbezüglichen numerischen Analyse wird schließlich ein analytisches Modell für die Vorhersage der Energieeinbringung entwickelt. Jene Energieeinbringung bestimmt als Anfangsbedingung für die Simulation des zweiten Teilprozesses den Berst- bzw. Vaporisationsdruck. Dieser wird impulsartig auf das Blech übertragen, wodurch die u. a. dehnratenabhängige und aufgrund der Trägheit inhomogene Umformung voranschreitet. Der gasförmig expandierende Aktuator wird dabei mit einer netzfreien Partikelmethode modelliert, während die damit interagierenden Festkörper der Finite-Elemente-Methode genügen. Zuvor mittels speziellem Laser bei freier Umformung gemessene Geschwindigkeits- bzw. Verschiebungsverläufe von Stahlblechen validieren den gewählten Modellierungsansatz, womit nun ein durchgängiges Prozessmodell zur Verfügung steht. Zudem werden räumlich flexible Vaporisationsdruckverteilungen mithilfe eines weiter vereinfachten Umformmodells evaluiert und bauteilbezogen optimiert. Im Rahmen einer beispielhaften, experimentellen Umsetzung werden unter Zuhilfenahme der Analytik erstmals zwei unterschiedliche Vaporisationsbereiche - d. h. Aluminiumfolien - für die Ausformung unterschiedlicher, verbundener Bauteilhöhen parallel geschaltet. Abschließend werden noch Konzepte aufgezeigt, die zum einen die Flexibilität und zum anderen die Berechnungseffektivität des noch jungen Fertigungsverfahrens weiter steigern könnten

Interaction of process parameters, forming mechanisms, and residual stresses in single point incremental forming

The residual stress state of a sheet metal component manufactured by metal forming has a significant influence on the mechanical properties, and thus determines the time until the component fails, especially for dynamic loads. The origin of the resulting residual stress state of incrementally formed parts with regard to the forming mechanisms of shearing, bending, and the normal stress component is still under investigation. The relationship between the process parameters, the forming mechanisms, and the resulting residual stress state for a complex part geometry manufactured by single point incremental forming (SPIF) is presented in this publication. For this purpose, a validated numerical process model is used to analyze the influence of the step-down increment Δz for truncated cones on the characteristics of the forming mechanisms and the resulting residual stress state. For the first time the forming mechanisms are evaluated numerically on both sides of the formed component. A relationship between the process parameters, forming mechanisms, residual stresses, and the mechanical properties of an incrementally formed component is shown. Shearing-induced hardening is identified as a relevant influence on the residual stress state of cones

Controle do nematoide das galhas do tomateiro utilizando substrato de cogumelos e formulados de Nim

Orientador: Dr. Henrique da Silva Silveira DuarteCoorientadores: Drª Louise Larissa May De Mio, Dr. Sérgio Miguel MazaroTese (doutorado) - Universidade Federal do Paraná, Setor de Ciências Agrárias, Programa de Pós-Graduação em Agronomia – Produção Vegetal. Defesa : Curitiba, 31/08/2021Inclui referênciasResumo: Os nematoides das galhas (Meloidogyne spp.) podem ser considerados como os fitonematoides mais importantes para diversas culturas agrícolas, pois causam perdas médias na ordem de 25% na produtividade, são cosmopolitas, polífagos e possuem uma alta eficiência reprodutiva. O controle desses nematoides é difícil e pode demandar a integração de diversas medidas de controle. O controle de nematoides com fungos nematófagos e extratos vegetais vem ganhando destaque devido a demanda por produtos agrícolas produzidos sem agrotóxicos. Os fungos nematófagos já são utilizados comercialmente para o controle de Meloidogyne. Entretanto, somente poucas espécies desses fungos são utilizadas. Os cogumelos são espécies de fungos capazes de controlar os nematoides pela produção de substâncias nematicidas e estruturas de predação. Entretanto, a maioria dos estudos foram realizados em condições in vitro, evidenciando o efeito direto dos cogumelos sobre os nematoides. Considerando que as espécies Lentinula edodes, Macrocybe titans e Pleurotus eryngii possuem potencial de controle de M. javanica, objetivou-se no Capítulo I desse trabalho: i) verificar o potencial de produção de mudas de tomate cultivadas em substrato de cogumelo; ii) avaliar o controle de M. javanica a partir do cultivo de mudas de tomate em substrato de cogumelo; iii) verificar se a incorporação do substrato de cogumelo ao solo pode auxiliar no manejo de M. javanica em tomateiro. Além do efeito direto sobre os nematoides como estruturas de predação e produção de toxinas, os cogumelos podem afetar indiretamente os nematoides. Esse efeito indireto dos cogumelos ocorre pela indução de mecanismos de resistência das plantas aos nematoides. Assim, objetivou-se no Capítulo II desse trabalho verificar os mecanismos de resistência induzidos por L. edodes e P. eryngii contra M. javanica em plantas de tomateiros. Além dos cogumelos, os extratos vegetais podem atuar de maneira direta sobre os nematoides produzindo substâncias tóxicas. O extrato de Nim (Azadirachta indica) é rico em compostos químicos com potencial nematicida. Assim, objetivou-se no Capítulo III verificar a utilização de dois produtos comerciais a base de extrato bruto de Nim, o OpeNeem Flex e OpeNeem Plus para o controle de M. javanica em plantas de tomateiro. Os resultados obtidos no Capítulo I indicam que a produção de mudas de tomateiro em substrato de cogumelos não possui potencial de controle de M. javanica. Entretanto, a incorporação do substrato de cogumelo no substrato de cultivo de tomate em concentrações >=12,5% para os isolados LEMID-Led02, LEMID-Mti01 e LEMIDPer01 e >=25% para o isolado LEMID-Led01 reduziu o fator de reprodução do nematoide. Portanto, esta medida de controle torna-se uma ferramenta útil a ser incorporada no manejo integrado de M. javanica. No Capítulo II, os resultados apontam que as análises bioquímicas demonstraram ocorrer indução de resistência nas plantas de tomateiro pelos substratos de cogumelos, ativando as enzimas relacionadas a defesa vegetal ?-1,3-glucanase e quitinase, sendo a rota preferencial de defesa. No Capítulo III, os valores estimados de concentração efetiva de 50% de controle (CE50) de eclosão de J2's foram de 0,44 e 0,40%, e para a mortalidade dos J2's foram estimadas em 13,9 e 19,3%, respectivamente para OpeNeem Flex para OpeNeem Plus. As aplicações dos formulados OpeNeem Flex e OpeNeem Plus sobre plantas de tomateiros infestados com J2's de M. javanica não apresentou efeitos significativos sobre a altura e massa da matéria seca das plantas de tomateiros, mas resultou na redução significativa do fator de reprodução de M. javanica. As concentrações de 1,0% dos formulados de Nim reduziu o fator de reprodução de M. javanica em 48,2% para OpeNeem Flex e 59,4% para OpeNeem Plus, controle semelhante ao obtido com a Abamectina (58,8%). Assim, a aplicação de formulados obtidos de subprodutos da produção de óleo de Nim possuem potencial de controle de M. javanica em plantas de tomateiro.Abstract: Root-knot nematodes (Meloidogyne spp.) can be considered the most important plant parasitic nematodes for several agricultural crops, as they cause average losses in the order of 25% in productivity, are cosmopolitan, polyphagous and have a high reproductive efficiency. Controlling these nematodes is difficult and may require the integration of different control measures. The control of nematodes with nematophagous fungi and plant extracts has gained prominence due to the demand for agricultural products without pesticides. Nematophagous fungi are already commercially used to control Meloidogyne. However, only a few species of these fungi are used. Mushrooms are fungal species capable of controlling nematodes by producing nematicidal substances and predation structures. However, most studies were carried out under in vitro conditions, showing the direct effect of mushrooms on nematodes. Considering that the species Lentinula edodes, Macrocybe titans and Pleurotus eryngii have potential to control M. javanica, the objective of Chapter I of this study was to: i) verify the production potential of tomato seedlings cultivated in mushroom substrate; ii) evaluate the control of M. javanica from the cultivation of tomato seedlings in mushroom substrate; iii) verify if the incorporation of mushroom substrate to the soil can help in the management of M. javanica in tomato. In addition to the direct effect on nematodes, such as the formation of predation structures and toxin production, mushrooms can indirectly affect nematodes. This indirect effect of mushrooms occurs through the induction of plant resistance mechanisms to nematodes. Thus, the objective of Chapter II of this study was to verify the resistance mechanisms induced by L. edodes and P. eryngii against M. javanica in tomato plants. In addition to mushrooms, plant extracts can act directly on nematodes, producing toxic substances. Neem extract (Azadirachta indica) is rich in chemical compounds with nematicidal potential. Thus, the objective of Chapter III was to verify the use of two commercial products based on crude Neem extract, OpeNeem Flex and OpeNeem Plus, for the control of M. javanica in tomato plants. The results obtained in Chapter I indicate that the production of tomato seedlings in mushroom substrate has no potential to control M. javanica. However, the incorporation of mushroom substrate in tomato cultivation substrate at concentrations >=12.5% for the isolates LEMID-Led02, LEMID-Mti01 and LEMID-Per01 and >=25% for the isolate LEMID-Led01 reduced the reproduction factor of the nematode. Therefore, this control measure is a useful tool to be incorporated into the integrated management of M. javanica. In Chapter II, the biochemical analyzes showed that there was induction of resistance in tomato plants by mushroom substrates, with the activation of the ? -1,3-glucanase and chitinase enzymes related to plant defense, being the preferred defense pathway. In Chapter III, the estimated values of effective concentrations for 50% control (EC50) of J2's hatching were 0.44 and 0.40%, and for the mortality of J2's they were estimated at 13.9 and 19.3%, respectively for OpeNeem Flex for OpeNeem Plus. The applications of OpeNeem Flex and OpeNeem Plus formulations on tomato plants infested with M. javanica J2's did not show significant effects on height and dry matter of tomato plants but resulted in a significant reduction in the reproduction factor of M. javanica. Concentrations of 1.0% of the Neem formulations reduced the reproduction factor of M. javanica by 48.2% for OpeNeem Flex and by 59.4% for OpeNeem Plus, a control similar to that obtained with Abamectin (58.8%). Thus, the application of formulations obtained from Neem oil by-products have potential to control M. javanica in tomato plants

Levantamento bibliométrico dos estudos com fungos nematófagos para o controle de Meloidogyne spp. e potencial de cogumelos no controle de Meloidogyne javanica

Orientador : Prof. Dr. Henrique da Silva Silveira DuarteCoorientadores : Profª Dra. Louise Larissa May de Mio, Profº Dr. Odair José Kuhn, Profº Dr. José Renato StangarlinDissertação (mestrado) - Universidade Federal do Paraná, Setor de Ciências Agrárias, Programa de Pós-Graduação em Agronomia. Defesa: Curitiba, 20/02/2017Inclui referênciasÁrea de concentração: Produção vegetalResumo: Os nematoides das galhas (Meloidogyne spp.) estão presentes em diversas partes do mundo, parasitando inúmeras espécies vegetais, dentre as quais estão incluídas muitas plantas de interesse econômico. Dentre as medidas de controle utilizadas para o manejo de Meloidogyne spp. estão os fungos nematófagos. O levantamento dos estudos referentes às interações de fungos nematófagos com Meloidogyne spp. pode fornecer informações sobre as principais espécies de fungos nematófagos, espécies de Meloidogyne alvo e as espécies de plantas hospedeiras mais estudadas no mundo. Dentre as espécies de fungos nematófagos, algumas espécies são capazes de produzir cogumelos, fato que torna o resíduo de sua produção uma possibilidade para o uso no controle de nematoides. Com base no exposto, os objetivos para a realização deste estudo foram: i) levantar informações sobre o panorama nacional e internacional das pesquisas com fungos nematófagos para o controle de Meloidogyne spp. ii) analisar o potencial de espécies de cogumelos para o controle de Meloidogyne javanica. O levantamento apontou a Índia com o maior número de publicações, seguida pelo Brasil. A frequência das publicações apresentou picos na década de 1990 e pós anos 2000. Das 189 espécies de fungos nematófagos estudadas, a espécie mais estudada foi Pochonia chlamydosporia. Os fungos nematófagos foram estudados para 9 espécies de Meloidogyne, sendo M. incognita e M. javanica as mais estudadas no mundo e no Brasil, respectivamente. A maior parte dos estudos foi realizada in vivo, no qual Solanum lycopersicum foi a espécie de planta hospedeira mais estudada. O segundo estudo avaliou as espécies de cogumelos com potencial ovicida, nematostático e nematicida. Para os testes realizados, os isolados de Lentinula edodes, Macrocybe titans e Pleurotus eryngii apresentaram potencial para o controle de M. javanica in vitro. Os cogumelos caracterizados como fungos nematófagos têm potencial para o controle de Meloidogyne javanica, o que permitirá o desenvolvimento de novas táticas de manejo para o controle de nematóides. Palavras-chave: nematoide das galhas, controle biológico, basidiomicetos.Abstract: Root-knot nematodes (Meloidogyne spp.) are present in several parts of the world, parasitizing thousands of plant species, many of economic interest. Among the control measures used for Meloidogyne spp. are nematophagous fungi. Studies with nematophagous fungi have been carried out all over the world, and the survey of studies published worldwide in the world and in Brazil can provide information on the main species of nematophagous fungi, species of Meloidogyne spp. and most studied species of host plants worldwide. Among the nematophagous fungi species, some are capable of forming mushrooms, which makes the residue of its production a possibility for nematodes control. Based on the information exposed above, the objectives of this study were: i) gather information on the national and international panorama of nematophagous fungi research for Meloidogyne spp. control.; ii) analyze the potential of mushrooms species to control Meloidogyne javanica. The survey showed that India was the country with most publications, followed by Brazil. The frequency of the publications peaked in the 1990s and after the 2000s. From the 189 species of nematophagous fungi studied, the most studied species was Pochonia chlamydosporia. These species of fungi were tested for 9 species of Meloidogyne, being Meloidogyne incognita and M. javanica the most studied in the world and in Brazil, respectively. Mushrooms characterized as nematophagous fungi have potential for Meloidogyne javanica control, which will allow the development of new nematode management strategies. Key words: root-knot nematodes, biological control, basidiomycetes

Effect of preheating during laser metal deposition on the properties of laminated bending dies

Metal-laminated tooling provides a fast and cheap manufacturing concept. In this study, laser metal deposition (LMD) is used for reducing and eliminating the stair step effect in a metal-laminated bending die. Preheating could decrease the undesired residual stresses in additive manufacturing, thus a systematical analysis of the effect of preheating of the laminae on the surface quality and mechanical properties of the bending die is performed. Ferritic steel sheets (S355 MC) with a thickness of 2 mm are laser cut and stacked up to manufacture the laminated bending die with a radius of 6 mm. The sheets are joined and the stair steps are filled with LMD with stainless steel powder 316L-Si. The initial temperature of the tool sheets (substrates), beside room temperature, is elevated up to 300 °C. The effect of the preheating on the surface roughness, shape deviation, hardness, and residual stresses of the die are investigated. The mean height of the surface increases by 59% at elevated temperatures. However, the tensile residual stress parallel to the weld direction at the middle of the deposited area decreases only around 25%. The functionality of the forming tools manufactured by this method is proven by bending of DC06 and HC380LA sheets

Gemini NIFS survey of feeding and feedback processes in nearby Active Galaxies: I - Stellar kinematics

We use the Gemini Near-Infrared Integral Field Spectrograph (NIFS) to map the stellar kinematics of the inner few hundred parsecs of a sample of 16 nearby Seyfert galaxies, at a spatial resolution of tens of parsecs and spectral resolution of 40 km/s. We find that the line-of-sight (LOS) velocity fields for most galaxies are well reproduced by rotating disk models. The kinematic position angle (PA) derived for the LOS velocity field is consistent with the large scale photometric PA. The residual velocities are correlated with the hard X-ray luminosity, suggesting that more luminous AGN have a larger impact in the surrounding stellar dynamics. The central velocity dispersion values are usually higher than the rotation velocity amplitude, what we attribute to the strong contribution of bulge kinematics in these inner regions. For 50% of the galaxies, we find an inverse correlation between the velocities and the $h_3$ Gauss-Hermitte moment, implying red wings in the blueshifted side and blue wings in the redshifted side of the velocity field, attributed to the movement of the bulge stars lagging the rotation. Two of the 16 galaxies (NGC 5899 and Mrk 1066) show an S-shape zero velocity line, attributed to the gravitational potential of a nuclear bar. Velocity dispersion maps show rings of low-$\sigma$ values (50-80 km/s) for 4 objects and "patches" of low-sigma for 6 galaxies at 150-250 pc from the nucleus, attributed to young/ intermediate age stellar populations.Comment: To be published in MNRA