Finite element simulation of additive manufacturing with enhanced accuracy

Tesi en modalitat de compendi de publicacionsThis thesis develops numerical methods to improve the accuracy and computational efficiency of the part-scale simulation of Additive Manufacturing (AM) (or 3D printing) metal processes. AM is characterized by multiple scales in space and time, as well as multiple complex physics that occur in three-dimensional growing-in-time geometries, making its simulation a remarkable computational challenge. To this end, the computational framework is built by addressing four key topics: (1) a Finite Element technology with enhanced stress/strain accuracy including the incompressible limit; (2) an Adaptive Mesh Refinement (AMR) strategy accounting for geometric and solution accuracies; (3) a coarsening correction strategy to avoid loss of information in the coarsening AMR procedure, and (4) a GCodebased simulation tool that uses the exact geometric and process parameters data provided to the actual AM machinery. In this context, the mixed displacement/deviatoric-strain/pressure u/e/p FE formulation in (1) is adopted to solve incompressible problems resulting from the isochoric plastic flow in the Von Mises criterion typical of metals. The enhanced stress/strain accuracy of the u/e/p over the standard and u/p FE formulations is verified in a set of numerical benchmarks in iso-thermal and non-isothermal conditions. A multi-criteria AMR strategy in (2) is used to improve computational efficiency while keeping the number of FEs controlled and without the strictness of imposing the commonly adopted 2:1 balance scheme. Avoiding this enables to use high jumps on the refinement level between adjacent FEs; this improves the mesh resolution on the region of interest and keeps the mesh coarse elsewhere. Moving the FE solution from a fine mesh to a coarse mesh introduces loss of information. To prevent this, a coarsening correction strategy presented in (3) restores the fine solution in the coarse mesh, providing computational cost reduction and keeping the accuracy of the fine mesh solution accuracy. Lastly, design flexibility is one of the main advantages of AM over traditional manufacturing processes. This flexibility is observed in the design of complex components and the possibility to change the process parameters, i.e. power input, speed, waiting pauses, among others, throughout the process. In (4) a GCode-based simulation tool that replicates the exact path travelled and process parameters delivered to the AM machiney is developed. Furthermore, the GCode-based tool together with the AMR strategy allows to automatically generate an embedded fitted cartesian FE mesh for the evolving domain and removes the challenging task of mesh manipulation by the end-user. The FE framework is built on a high-performance computing environment. This framework enables to accelerate the process-to-performance understanding and to minimize the number of trial-and-error experiments, two key aspects to exploit the technology in the industrial environment.Esta tesis tiene como objetivo desarrollar métodos numéricos para mejorar la precisión y eficiencia computacionales en simulaciones de piezas fabricadas mediante Manufactura Aditiva (MA), también conocida como Impresión 3D. La manufactura aditiva es un problema complejo que involucra múltiples fenómenos físicos, que se desarolla en múltiples escalas, y cuya geometría evoluciona en el tiempo. Para tal fin, se plantean cuatro objetivos: (1) Desarrollo de una tecnología de elementos finitos para capturar con mayor precisión tanto tensiones como deformaciones en casos en el que el material tiene comportamiento isocórico; (2) Una estrategia de adaptividad de malla (AMR), que busca modificar la malla teniendo en cuenta la geometría y los errores en la solución numérica; (3) Una estrategia para minimizar la aproximación numérica durante el engrosamiento (coarsening) de la malla, crucial en la reducción de tiempos de cómputo en casos de piezas de grandes dimensiones; y (4) Un marco de simulación basado en la lectura de ficheros GCode, ampliamente usado por maquinaria de impresión en procesos de manufactura aditiva, un formato que no sólo proporciona los datos asociados a la geometría, sino también los parámetros de proceso. Con respecto a (1), esta tesis propone el uso de una formulación mixta en desplazamientos /deformación-desviadora / presión (u/e/p), para simular la deposición de materiales con deformación inelástica isocórica, como ocurre en los metales. En cuanto a la medición de la precisión en el cálculo de las tensiones y las deformaciones, en esta tesis se realiza un amplio número de experimentos tanto en condiciones isotérmicas como no isotérmicas para establecer una comparativa entre las dos formulaciones mixtas, u/e/p y u/p. Con respecto a (2), para mejorar la eficiencia computacional manteniendo acotado el número total de elementos finitos, se desarrolla una novedosa estrategia multicriterio de refinamiento adaptativo. Esta estrategia no se restringe a mallas con balance 2:1, permitiendo así tener saltos de nivel mayores entre elementos adyacentes. Por otra parte, para evitar la pérdida de información al proyectar la solución a mallas más gruesas, se plantee una corrección en (3), que tiene como objetivo recuperar la solución de la malla fina, garantizando así que la malla gruesa conserve la precisión obtenida en la malla fina. El proceso de manufactura aditiva se distingue por su gran flexibilidad comparándolo con otros métodos tradicionales de manufactura. Esta flexibilidad se observa en la posibilidad de construir piezas de gran complejidad geométrica, optimizando propiedades mecánicas durante el proceso de deposición. Por ese motivo, (4) se propone la lectura de ficheros en formato GCode que replica la ruta exacta del recorrido del láser que realiza la deposición del material. Los ingredientes lectura de comandos escritos en lenguaje Gcode, multicriterio de adaptividad de malla y el uso de mallas estructuradas basadas en octrees, permiten capturar con gran precisión el dominio discreto eliminando así la engorrosa tarea de generar un dominio discreto ad-hoc para la pieza a modelar. Los desarrollos de esta tesis se realizan en un entorno de computación de altas prestaciones (HPC) que permite acelerar el estudio de la ejecución del proceso de impresión y por ende reducir el número de experimentos destructivos, dos aspectos clave que permiten explorar y desarrollar nuevas técnicas en manufactura aditiva de piezas industriales.Postprint (published version

A multi-criteria h-adaptive finite-element framework for industrial part-scale thermal analysis in additive manufacturing processes

This work presents an h-adaptive finite-element (FE) strategy to address the numerical simulation of additive manufacturing (AM) of large-scale parts. The wire-arc additive manufacturing is chosen as the demonstrative technology for its manufacturing capabilities suitable for industrial purposes. The scanning path and processing parameters of the simulation are provided via a RS-274 (GCode) file, being the same as the one delivered to the AM machine. The approach is suitable for industrial applications and can be applied to other AM processes. To identify the location in the FE mesh of the heat affected zone (HAZ), a collision detection algorithm based on the separating axis theorem is used. The mesh is continuously adapted to guarantee the necessary mesh resolution to capture the phenomena inside and outside the HAZ. To do so, a multi-criteria adaptive mesh refinement and coarsening (AMR) strategy is used. The AMR includes a geometrical criterion to guarantee the FE size within the HAZ, and a Zienkiewicz–Zhu-based a-posteriori error estimator to guarantee the solution accuracy elsewhere. Thus, the number of active FEs is controlled and mesh manipulation by the end-user is avoided. Numerical simulations comparing the h-adaptive strategy with the (reference) fixed fine meshes are performed to prove the computational cost efficiency and the solution accuracy.The financial support from the Spanish Ministry of Economy and Competitiveness, through the Severo Ochoa Programme for Centres of Excellence in R&D (CEX2018-000797-S), is gratefully acknowledged. This work has been supported by the European Union’s horizon 2020 research and innovation programme (H2020-DT-2019-1 no. 872570) under the KYKLOS 4.0 Project (An Advanced Circular and Agile Manufacturing Ecosystem based on rapid reconfigurable manufacturing process and individualized consumer preferences) and by the Ministry of Science, Innovation and Universities (MCIU) via: the PriMuS project (Printing pattern based and MultiScale enhanced performance analysis of advanced Additive Manufacturing components, ref. num. PID2020-115575RB-I00). J. Baiges gratefully acknowledges the support of the Spanish Government through the Ramón y Cajal Grant RYC-2015-17367. Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature.Peer ReviewedPostprint (published version

SÍSMICA DE REFRAÇÃO NO DOMO ESTRUTURAL DE PITANGA, RIO CLARO (SP)

Este trabalho apresenta a interpretação dos ensaios de sísmica de refração executado no Alto Estrutural Domo de Pitanga., localizado entre as cidades de Rio Claro e Piracicaba, nordeste do Estado de São Paulo. Foi executada uma seção de refração sísmica com aproximadamente 14.100m de comprimento onde foram dispostos 12 conjuntos de geofones e registradores digitais. Como fontes de ondas sísmicas foram utilizadas explosões de pedreiras localizadas nas extremidades da seção. Os resultados obtidos com a interpretação tomográfica e a do método plus-minus mostrou a existência de um alto do embasamento da Bacia do Paraná localizado em 1000m e 4000 m da Pedreira Bonança, foi também detectado um grande corpo de diabásio próximo à Pedreira Stavias. O alto estrutural encontrado pode ter sido causado por esforços compressivos resultantes das intrusões básicas. Este alto pode ter elevado a coluna de sedimentos, expondo sedimentos mais antigos

ALTERATIONS IN ELECTRICAL RESISTIVITY OF SANDY SOIL IN CONTROLLED EXPERIMENT BY INFLITRATION OF STILLAGE

The sugar and alcohol sector represents one of the most profitable economic activities in Brazil, being ethanol one of the main products. Among the residues related to the production of ethanol, it is highlighted the stillage, a liquid substance generated in the approximate proportion of 13 liters for each liter of ethanol produced. This paper presents the results of a stillage infiltration experiment, in various proportions, through trenches in sandy soil, with the aim to evaluate possible alterations in electrical properties in the geological materials, in individual experiments, with 60L, 300L and 900L of effluent. The initial proportion was defined based on a standard stipulated by the Environmental Agency of the State of São Paulo, which considers the cation exchange capacity of the soil, while the other quantities were defined from ratios of 4 and 15 times higher than those defined by legislation. The experiment was monitored by means of electrical resistivity measurements by indirect means through the geophysical method of Electroresistivity. The data indicate the absence of alterations in electrical properties in the soil below the point of infiltration in the experiment for 60L of stillage. The data for infiltrations with 300L and 900L revealed a zone of low resistivity below the infiltration point, basically limited to the 1m layer of sandy soil and with tendency for lateral flow supported by the soil/rock interface. The results demonstrate that the infiltration of inorganic solutions, in a proportion inferior to the cation exchange capacity of the soil, does not perceptibly alter its electrical properties in studies using the geophysical method of Electro resistivity, whereas proportions that exceed natural absorption capacity are characterized by the geoelectric signature of low resistivity

Integração e análise de dados aerogeofísicos por meio da aplicação de técnicas de processamento digital de imagens e classificação não supervisionada : o exemplo do Greenstone Belt Rio das Velhas, quadrilátero ferrífero, MG

Afloramentos escassos e um intemperismo acentuado caracterizam o Greenstone Belt Rio das Velhas no sudeste do Brasil. Este artigo sumariza a utilização de dados aerogeofísicos de alta densidade de amostragem aplicados à exploração mineral baseado no realce e na interpretação de dados magnéticos, radiométricos e eletromagnéticos no domínio da freqüência através de métodos de processamento digital de imagens e classificação não supervionada. Os produtos gerados forneceram novos insights e uma excelente ferramenta para mapeamentos dos diferentes litotipos, melhorando o conteúdo da informação presente nos canais individuais. As imagens geofísicas foram processadas utilizando diferentes combinações. O melhor produto obtido foi a integração via IHS da amplitude e da inclinação do sinal analítico. Informações extraídas desta imagem mapeiam tanto a geologia quanto lineamentos na escalas regionais e locais. Aplicou-se a técnica de classificação não supervisionada conhecida com média K aos dados aerogeofísicos. O resultado realça litologias mapeadas por geólogos de campo na escala 1:100.000. Ela mapeia também rochas hospedeiras e diferentes domínios associados com a mineralização aurífera. Tais domínios são conhecidos por hospedar a mineralização aurífera, ilustrando a utilidade destas técnicas para enriquecer o conhecimento geológico da área estudada.Poor outcrop and deep weathering characterize the Rio das Velhas Greenstone Belt in the southeastern from Brazil. This paper summarizes the use of high-density airborne survey for mineral exploration studies based on interpretation enhancements of magnetic, radiometric and frequency domain electromagnetic data using image-processed methods and an unsupervised classification. The generated products provide new insights and an excellent tool for mapping and trace individual lithological units, improving the information content of the single geophysical channels. The geophysical images were processed using different combinations. The best product was the analytical signal amplitude and inclination integrated by IHS transformation. Information extracted from this image maps the geology and lineament patterns at both regional and local scales. The K-means technique using ten classes was also applied to the geophysical data. These results enhance the lithologies mapped by the field geologists at the 1:100.000. Also shows important host rocks and different gold mineralized geological domains. Such domains host the known gold mineralization, illustrating the utility of these techniques to improve the geological knowledge in the study area

AN EXPLORATION OF HEALTH AND SAFETY MANAGEMENT ISSUES IN NIGERIA’S EFFORT TO INDUSTRIALIZE

All organizations have a duty of care to ensure that employees and other persons who may be affected by the company’s undertakings remain safe at all times. This paper examines the background of occupational health and safety (OHS) practices in Nigeria, and highlights the importance of mitigating the OHS challenges identified from the moral, legal, financial and other dimensions. In the Nigerian context, the need to reinforce health and safety management (HSM) issues is exemplified from the unsavory recurrent reports of plane crashes in the aviation industry, high rates of motor vehicle accidents, numerous cases of death due to poisoning in the solid mineral sector, frequent accounts of disasters in the petroleum sector arising from oil spills, pipeline vandalism as well as accidents involving petroleum tankers. More effective and efficient management of these issues is a sine qua non to the industrialization efforts of an economy. Against the background of extant HS legislation in Nigeria, some reasons for the frequent violations of OHS standards and norms by the operators were identified as bribery and corruption in the system, the ‘Nigerian Factor’, inadequate funding of monitoring institutions, low level of education of employees as well as problems of persistent unemployment in the country. While recommending ways to mitigate the OHS flaws in Nigerian institutions, the relative duties and responsibilities of stakeholders in the OHS business were identified. The paper concludes by noting the importance of a virile HSM environment to the overall economic development and industrialization of the nation

Professional and educational characteristics and geographical distribution of physical therapists in Paraná - Brazil

Este estudio tuvo como objetivo conocer el perfil de los fisioterapeutas paranaenses en el año de 2015, sus características sociodemográficas, tendencias en la formación y el mercado de trabajo, en una investigación cuantitativa de carácter transversal. La muestra fue compuesta por 377 fisioterapeutas, de los 11272 inscritos en el Consejo Profesional en el año de 2015, que respondieron a un cuestionario estructurado disponible en línea. Los resultados mostraron que los fisioterapeutas de Paraná se constituyen predominantemente por jóvenes de 21 a 40 años (el 81,7%), del sexo femenino (el 77,7%), y se concentran en la macrorregión de Curitiba (el 53,6%). La gran parte se graduó en los últimos diez años (el 59,9%) y posee postgrado lato sensu (el 73,7%), sin embargo, pocos poseen maestría o doctorado. La gran parte (el 82,8%) trabaja exclusivamente con la profesión, en un único empleo (el 53,3%), en institución privada (el 59,2%), como autónomos (el 55,7%), con carga horaria de más de ocho horas diarias (el 35,5%). Con relación el área de actuación, el 68,7% trabajan en más de un área, siendo la Traumatología y la Ortopedia las que presentan el número de profesionales actuantes más grande (el 59,9%), después de la Neurofuncional (el 41,1%) y de la Respiratoria (el 38,7%). La gran parte de los profesionales tienen ingreso mensual entre el piso salarial y cuatro mil reales (el 42,9%). Así, fue posible plantear el perfil del fisioterapeuta de Paraná en 2015, vislumbrando la identidad de la profesión en el estado y la proyección de tendencias futuras, lo que posibilitará las instituciones de enseñanza superior y las entidades representativas de la categoría la creación de estrategias futuras para la formación y la regulación del mercado de trabajo.Este estudo teve como objetivo conhecer o perfil dos fisioterapeutas paranaenses no ano de 2015, suas características sociodemográficas, tendências na formação e mercado de trabalho, em uma pesquisa quantitativa de caráter transversal. A amostra foi composta por 377 fisioterapeutas, dos 11272 inscritos no Conselho Profissional no ano de 2015, que responderam a um questionário estruturado disponível on-line. Os resultados mostraram que os fisioterapeutas do Paraná constituem-se predominantemente por jovens de 21 a 40 anos (81,7%), do sexo feminino (77,7%), e se concentram na macrorregião de Curitiba (53,6%). A maioria graduou-se nos últimos dez anos (59,9%) e possui pós-graduação lato sensu (73,7%), porém poucos possuem mestrado ou doutorado. A maioria (82,8%) trabalha exclusivamente com a profissão, em um único emprego (53,3%), em instituição privada (59,2%), como autônomos (55,7%), com carga horária de mais de oito horas diárias (35,5%). Com relação a área de atuação, 68,7% trabalham em mais de uma área, sendo Traumato-ortopedia a que apresenta o maior número de profissionais atuantes (59,9%), seguida da Neurofuncional (41,1%) e da Respiratória (38,7%). A maioria dos profissionais tem renda mensal entre o piso e quatro mil reais (42,9%). Assim, foi possível traçar o perfil do fisioterapeuta do Paraná em 2015, vislumbrando a identidade da profissão no estado e a projeção de tendências futuras, o que possibilitará às instituições de ensino superior e às entidades representativas da categoria a criação de estratégias futuras para formação e a regulação do mercado de trabalho.This study aimed to know the profile of physical therapists of Paraná in 2015, their sociodemographic characteristics, education tendencies and labor market. This is a quantitative cross-sectional research. The sample was comprised of 377 physical therapists, from the 11,272 professionals subscribed to the Professional Council in 2015, who answered a structured questionnaire available online. The results showed that physical therapists from Paraná are mostly young, aging from 21 to 40 years (81.7%), women (77.7%) and are concentrated in the macro-region of Curitiba (53.6%). The majority has graduated in the last ten years (59.9%) and has a specialization degree (73.7%); however, only a few are masters or PhDs. Most of the therapists (82.8%) work exclusively with their profession, having a single job (53.3%), at a private institution (59.2%), are self-employed (55.7%), having a daily workhour of eight hours (35.5%). Regarding the field of expertise, 68.7% work in more than one area, being Trauma and Orthopedic the one that presents the highest number of professionals (59.9%), followed by Neurofunctional (41.1%) and Respiratory (38.7%) areas. Most of the professionals have a monthly income between the minimum wage and 4,000 Reais (42.9%). Therefore, it was possible to outline the profile of physical therapists in Paraná in 2015, detecting the profession’s identity in the state and the projection of future tendencies, which will enable to the higher education institutions and category representation agencies the creation of future strategies for the designing and regulation of the labor market

Post-Mortem diagnosis of dementia by informant interview.

The diagnosis of normal cognition or dementia in the Brazilian Brain Bank of the Aging Brain Study Group (BBBABSG) has relied on postmortem interview with an informant. Objectives:To ascertain the sensitivity and specificity of postmortem diagnosis based on informant interview compared against the diagnosis established at a memory clinic. Methods:A prospective study was conducted at the BBBABSG and at the Reference Center for Cognitive Disorders (RCCD), a specialized memory clinic of the Hospital das Clínicas, University of São Paulo Medical School. Control subjects and cognitively impaired subjects were referred from the Hospital das Clínicas to the RCCD where subjects and their informants were assessed. The same informant was then interviewed at the BBBABSG. Specialists' panel consensus, in each group, determined the final diagnosis of the case, blind to other center's diagnosis. Data was compared for frequency of diagnostic equivalence. For this study, the diagnosis established at the RCCD was accepted as the gold standard. Sensitivity and specificity were computed. Results:Ninety individuals were included, 45 with dementia and 45 without dementia (26 cognitively normal and 19 cognitively impaired but non-demented). The informant interview at the BBBABSG had a sensitivity of 86.6% and specificity of 84.4% for the diagnosis of dementia, and a sensitivity of 65.3% and specificity of 93.7% for the diagnosis of normal cognition. Conclusions:The informant interview used at the BBBABSG has a high specificity and sensitivity for the diagnosis of dementia as well as a high specificity for the diagnosis of normal cognition

A InSURgência continua

InSURgência: revista de direitos e movimentos sociais. Brasília: IPDMS; PPGDH/UnB; Lumen Juris, vol. 1, n. 2, julho-dezembro de 2015, p. 1-5