Resumo A leishmaniose visceral (LV) é uma doença de natureza infecciosa, predominante em países de zonas tropicais. A predição de ocorrência de doenças infecciosas através da modelagem epidemiológica tem se revelado uma importante ferramenta no entendimento de sua dinâmica de ocorrência. O objetivo deste estudo foi desenvolver um modelo de previsão da incidência da LV no Maranhão usando o modelo de Média Móvel Integrada Autocorrelacionada Sazonal (SARIMA). Foram coletados os dados mensais de casos de LV através do Sistema de Informação de Agravos de Notificação (SINAN) correspondentes ao período de 2001 a 2018. O método de Box-Jenkins foi aplicado para ajustar um modelo de predição SARIMA para incidência geral e por sexo (masculino e feminino) de LV para o período de janeiro de 2019 a dezembro de 2023. Durante o período de 216 meses dessa série temporal, foram registrados 10.431 casos de LV no Maranhão, com uma média de 579 casos por ano. Em relação à faixa etária, houve maior registro no público pediátrico (0 a 14 anos). Houve predominância do sexo masculino, com 6437 casos (61,71%). Os valores do teste de Box-Pierce para incidência geral, sexo masculino e feminino reforçados pelos resultados do teste Ljung-Box sugerem que as autocorrelações de resíduos apresentam um comportamento de ruído branco. Para incidência mensal geral e por sexo masculino e feminino, os modelos SARIMA (2,0,0) (2,0,0), (0,1,1) (0,1,1) e (0,1,1) (2, 0, 0) foram os que mais se ajustaram aos dados, respectivamente. O modelo SARIMA se mostrou uma ferramenta adequada de previsão e análise da tendência de incidência da LV no Maranhão. A determinação da variação temporal e sua predição são determinantes no norteamento de medidas de intervenção em saúde.

Abstract Visceral leishmaniasis (VL) is an infectious disease predominant in countries located in the tropics. The prediction of occurrence of infectious diseases through epidemiologic modeling has revealed to be an important tool in the understanding of its occurrence dynamic. The objective of this study was to develop a forecasting model for the incidence of VL in Maranhão using the Seasonal Autoregressive Integrated Moving Average model (SARIMA). We collected monthly data regarding VL cases from the National Disease Notification System (SINAN) corresponding to the period between 2001 and 2018. The Box-Jenkins method was applied in order to adjust a SARIMA prediction model for VL general incidence and by sex (male or female) for the period between January 2019 and December 2013. For 216 months of this time series, 10,431 cases of VL were notified in Maranhão, with an average of 579 cases per year. With regard to age range, there was a higher incidence among the pediatric public (0 to 14 years of age). There was a predominance in male cases, 6437 (61.71%). The Box-Pierce test figures for overall, male and female genders supported by the results of the Ljung-Box test suggest that the autocorrelations of residual values act as white noise. Regarding monthly occurrences in general and by gender, the SARIMA models (2,0,0) (2,0,0), (0,1,1) (0,1,1) and (0,1,1) (2, 0, 0) were the ones that mostly adjusted to the data respectively. The model SARIMA has proven to be an adequate tool for predicting and analyzing the trends in VL incidence in Maranhão. The time variation determination and its prediction are decisive in providing guidance in health measure intervention.

Abstract Background: Facial nerve dysfunction is the principal postoperative complication related to parotidectomy. Objective: To test the hypothesis that the modified Sunnybrook Facial Grading System (mS-FGS) is superior to the original S-FGS in the assessment of facial nerve function following parotidectomy. Methods: Prospective, longitudinal study evaluating patients with primary or metastatic parotid neoplasms undergoing parotidectomy with facial nerve-sparing between 2016 and 2020. The subjects were assessed twice, on the first postoperative day and at the first outpatient evaluation, 20-30 days post-surgery. Facial assessments were performed using the original and modified (plus showing the lower teeth) versions of the Sunnybrook System and documented by pictures and video recordings. Intra- and inter-rater agreements regarding the assessment of the new expression were analyzed. Results: 101 patients were enrolled. In both steps, the results from the mS-FGS were significantly lower (p < 0.001). Subjects with a history of previous parotidectomy and those who underwent neck dissection had more severe facial nerve impairment. The mandibular marginal branch was the most frequently injured, affecting 68.3% of the patients on the first postoperative day and 52.5% on the first outpatient evaluation. Twenty patients (19.8%) presented an exclusive marginal mandibular branch lesion. The inter-rater agreement of the new expression assessment ranged from substantial to almost perfect. The intra-rater agreement was almost perfect (wk = 0.951). Conclusion: The adoption of the Modified Sunnybrook System, which includes evaluation of the mandibular marginal branch, increases the accuracy of post-parotidectomy facial nerve dysfunction appraisal.

Resumo Antecedentes: A disfunção do nervo facial é a principal complicação pós-operatória relacionada à parotidectomia. Objetivo: Testar a hipótese de que o sistema Sunnybrook de graduação facial modificado (mS-FGS) é superior ao S-FGS original na avaliação da função do nervo facial após parotidectomia. Métodos: Estudo longitudinal prospectivo avaliando o pós-operatório de pacientes com neoplasias parotídeas primárias ou metastáticas, submetidos à parotidectomia com preservação do nervo facial, entre 2016 e 2020. Os indivíduos foram avaliados duas vezes, no primeiro dia de pós-operatório e na primeira avaliação ambulatorial, 20-30 dias após a cirurgia. As avaliações faciais foram realizadas usando as versões original e modificada (que incluem mostrar os dentes inferiores) do sistema Sunnybrook e documentadas por fotos e vídeos. Foram adicionalmente analisadas as concordâncias intra e interexaminadoras da avaliação da nova expressão. Resultados: Cento e um pacientes foram incluídos. Em ambas as etapas, os resultados do mS-FGS foram significativamente menores (p < 0,001). Indivíduos com história de parotidectomia prévia e aqueles submetidos ao esvaziamento cervical apresentaram comprometimento mais grave do nervo facial. O ramo marginal mandibular foi o mais afetado, acometendo 68,3% dos pacientes no primeiro dia de pós-operatório e 52,5% na primeira avaliação ambulatorial. Vinte pacientes (19,8%) apresentaram lesão exclusiva do ramo marginal mandibular. A concordância interexaminadores da avaliação da nova expressão variou de substancial a quase perfeita. A concordância intraexaminador foi quase perfeita (wk = 0,951). Conclusão: A adoção do sistema Sunnybrook modificado, que inclui a análise do ramo marginal mandibular, aumenta a precisão da avaliação da disfunção do nervo facial pós-parotidectomia.

Abstract Objective: This study aims to describe bacterial and antimicrobial sensibilities in late-onset healthcare-associated infections (HAIs) with laboratory confirmation in a Neonatal Intensive Care Unit (NICU) of a public hospital in Ceará. Methods: This was a cross-sectional study conducted from January 2013 to December 2017. The bacterial types involved in late-onset HAIs, their sensitivity to antimicrobials, and their multidrug resistance were evaluated. The latter was classified according to the criteria revised by the Pan-American Health Organization as multidrug resistance (MDR), extended drug resistance (XDR), or pandrug resistance (PDR). The description of the variables was performed through proportions and frequency distribution depicted in tables. Results: Of the 427 patients with late-onset HAIs, 47 (11.0%) had bacterial infections confirmed by blood cultures, and 7 (14.9%) had infections caused by MDR bacteria. Among the types of bacteria, 26 (55.3%) were Gram-negative bacteria, and 21 (44.7%) were Gram-positive bacteria. Among the Gram-negative bacteria, 92.3% (n=24) showed resistance to more than one antimicrobial, especially to ampicillin (81.2%), cefepime (33.1%), gentamicin (19.4%), and piperacillin/tazobactam (17.2%). Among the MDR ones, three cases had Klebsiella pneumoniae, and three had Pseudomonas aeruginosa, classified as two MDR and one XDR, and three XDR, respectively. Gram-positive resistance to penicillin was the most common one (80.0%), and approximately half of the strains being resistant to oxacillin. Susceptibility was high to vancomycin (97.5%), but one microorganism was resistant to oxacillin and vancomycin. Conclusions: The emergence of MDR strains is a reality in NICUs, carrying the risk of therapeutic failure and requiring continuous prevention protocols aimed at minimizing the risks of contamination by bacteria with high morbidity and mortality.

RESUMO Objetivo: Descrever as bactérias e sensibilidades aos antimicrobianos nas infecções relacionadas à assistência à saúde (IRAS) tardias com confirmação laboratorial em Unidade de Terapia Intensiva Neonatal (UTIN) de um hospital público do Ceará. Métodos: Estudo transversal, de janeiro de 2013 a dezembro de 2017. Foram avaliados os tipos de bactérias das IRAS tardias, a sensibilidade aos antimicrobianos e a multirresistência. Esta foi classificada segundo os critérios revisados pela Organização Pan-Americana da Saúde como MDR, ou multirresistência (multidrug resistance); XDR, ou resistência estendida (extensively drug-resistance); ou PDR, panresistência (pandrug-resistance). A descrição das variáveis foi realizada por meio de proporções e distribuição das frequências na forma de tabelas. Resultados: Dos 427 pacientes com IRAS tardias, 47 (11,0%) apresentaram infecções bacterianas confirmadas por hemoculturas, sete (14,9%) das quais foram causadas por bactérias multirresistentes. Entre os tipos de bactérias, 26 (55,3%) foram Gram-negativas e 21 (44,7%) Gram-positivas. Entre as primeiras, 92,3% (n=24) apresentaram resistências a mais de um antimicrobiano, destacando-se ampicilina (81,2%), cefepima (33,1%), gentamicina (19,4%) e piperacilina/tazobactam (17,2%). Entre as multirresistentes, três foram Klebsiella pneumoniae e três Pseudomonas aeruginosa, classificadas como duas MDR e uma XDR, e três XDR, respectivamente. A resistência das Gram-positivas à penicilina foi a mais comum (80,0%). A susceptibilidade foi alta à vancomicina (97,5%), porém uma bactéria foi resistente à oxacilina e à vancomicina. Conclusões: O aparecimento de cepas multirresistentes é uma realidade em UTIN com risco de falha terapêutica, sendo necessários protocolos contínuos de prevenção a fim de minimizar os riscos de contaminação interpessoal e ambiental por bactérias de alta morbimortalidade.

Abstract Leishmaniasis is an anthropozoonosis transmitted by vectors, with dogs being the main domestic reservoirs. Brazil is one of the countries most affected by this disease, and it has been described in humans and dogs in every region in the country. In the northern region leishmaniasis cases in humans have been described in more than 100 municipalities in the State, including the capital, Belém. This study involves two cases of canine visceral leishmaniasis in which the animals developed clinical signs compatible with the disease in urban areas in Belém, the Pará state capital. The diagnosis was confirmed via polymerase chain reaction (PCR) to detect SSUr-rDNA and kDNA of Leishmania sp. and Leishmania infantum, respectively. In one of the cases the animal died and in the other the animal underwent treatment with medicines prescribed for dogs. Through this treatment, parasitemia in the second animal has been kept under control and is being monitored through molecular tests. Previously, no canine cases had been notified from urban neighborhoods in the city of Belém, but only on the island of Cotijuba, at a distance of 29 kilometers from the city. Cases of canine and human leishmaniasis have been recorded close to the capital, Belém, which has areas of conserved vegetation and where the presence of disease vectors has been described. Thus, as has been done in several other Brazilian cities, this study uses clinical and laboratory findings to confirm the presence of autochthonous cases of canine visceral leishmaniasis in the city of Belém.

Resumo A leishmaniose é uma antropozoonose transmitida por vetores, sendo os cães os principais reservatórios domésticos. O Brasil é um dos países mais acometidos por esta doença, sendo descrita em humanos e cães em todas as regiões do país. Na região norte casos de leishmaniose em humanos foram descritos em mais de 100 municípios do Estado, incluindo a capital, Belém. Este estudo envolve dois casos de leishmaniose visceral canina em que os animais desenvolveram sinais clínicos compatíveis com a doença em áreas urbanas de Belém, capital do estado do Pará. O diagnóstico foi confirmado pela reação em cadeia da polimerase (PCR) para detectar o SSUr-rDNA e kDNA de Leishmania sp e Leishmania infantum, respectivamente. Em um dos casos o animal veio a óbito e no outro o animal foi submetido a tratamento com medicamentos prescritos para cães. Por meio desse tratamento, a parasitemia no segundo animal foi mantida sob controle e está sendo monitorada por meio de testes moleculares. Anteriormente, nenhum caso canino havia sido notificado em bairros urbanos da cidade de Belém, apenas na ilha de Cotijuba, distante 29 quilômetros da cidade. Casos de leishmaniose canina e humana foram registrados próximo à capital, Belém, que possui áreas de vegetação conservada e onde foi descrita a presença de vetores de doenças. Assim, como tem sido registrado em várias outras cidades brasileiras, este estudo utiliza achados clínicos e laboratoriais para confirmar a presença de casos autóctones de leishmaniose visceral canina na cidade de Belém.

RESUMO: Avaliou-se a composição química do colostro de ovinos Santa Inês, leite refrigerado (zero a 240 horas) e leite congelado por até 70 dias. Os resultados de composição química (gordura, proteína, caseína, lactose, extrato seco total e desengordurado) e contagem de células somáticas do colostro (CCS) foram apresentados de forma descritiva. Os resultados da composição química, CCS e da contagem bacteriana total (CBT) do leite refrigerado e congelado foram avaliados em delineamento inteiramente casualizado. As repetições foram os dias de coleta do leite e os tratamentos os tempos em que o leite foi refrigerado e congelado. A comparação das médias de qualidade do leite resfriado e congelado foi realizada pelo teste de Tukey, com probabilidade de 5,0 %. O colostro de ovinos Santa Inês apresentou alto teor de proteína e gordura, demonstrando ser uma grande fonte de nutrientes para a nutrição de cordeiros. O leite de ovelha Santa Inês pode ser armazenado sob refrigeração por até 240 horas sem alterações da composição química. O leite congelado de ovelhas Santa Inês pode ser armazenado por até 70 dias, contudo ocorre alteração da composição química, principalmente nos teores de gordura. A refrigeração e o congelamento são alternativas que agregam valor ao leite de ovelhas Santa Inês, porém, mais estudos com estes métodos de preservação, são necessários para maior garantia de qualidade.

ABSTRACT: The chemical composition of Santa Inês sheep colostrum was evaluated, as well as chilled milk (zero to 240 hours) and frozen milk for up to 70 days. Results of chemical composition (fat, protein, casein, lactose, total and degreased dry extract) and colostrum somatic cell count (SCC) were presented descriptively. The results of chemical composition and SCC and total bacterial count (TBC) of chilled and frozen milk were evaluated in a completely randomized design, the repetition of milk collection days and the treatments of the times when the milk was chilled and frozen. The comparison of the quality averages of chilled and frozen milk was performed by Tukey test, with a probability of 5.0 %. Santa Inês sheep colostrum showed high protein and fat content, demonstrating a high source of nutrients for lamb nutrition. Santa Inês sheep’s milk can be stored for up to 240 hours without changes in chemical quality. Frozen milk from Santa Inês ewes for up to 70 days minus fat content; however, this form of milk preservation is viable. Refrigeration and freezing are alternatives that add value to the milk of Santa Inês ewes, but studies with previous preservation methods are necessary for greater quality assurance.

ABSTRACT Background: American cutaneous leishmaniasis is a commonly neglected, vector-borne tropical parasitic disease that is a major public health concern in Brazil. Leishmania (Viannia) braziliensis is the main species associated with the disease. Accurate diagnosis is based on epidemiological surveillance, clinical assessment, and laboratory testing. Leishmania (V.) braziliensis has been detected in several wild and synanthropic mammals. Their epidemiological role has not been entirely elucidated. This study aimed to assess potential L. braziliensis infections in asymptomatic domestic animals, by molecular and serological testing in endemic areas, in the metropolitan region of Recife. Methods: Blood samples and conjunctival fluids were collected from 232 animals (canids, felids, equines, and caprines) for the detection of L. braziliensis using molecular tests (conventional and real-time polymerase chain reaction [PCR and qPCR]). For immunological detection, blood samples from 115 dogs were assessed using enzyme-linked immunosorbent assay. Results: Real-time quantitative PCR showed positive results for blood and conjunctival samples in all investigated species. The results of the blood and conjunctival samples were 68.2% and 26.9% in Canis familiaris, 100% and 41.7% in Felis catus, 77.3% and 30.8% in Equus caballus/Equus asinus, and 50% and 33.3% in Capra hircus samples, respectively. Conclusions: Results from this study adds valuable information to our understanding of the role of asymptomatic domestic animals, L. braziliensis life cycle, and American cutaneous leishmaniasis in Northeast Brazil.

Abstract Welding operations are one of the most important operations during pipeline construction and most are still carried out manually with SMAW. The challenges associated with the automation of orbital welding are related to several variables, including the weld pool behavior in vertical and overhead positions, monitoring of parameters and metal transfer, bevel preparation and orbital welding head control. In order to achieve a 360º orbital root pass with GTAW process, this study was focused on evaluating the influence of the arc voltage control (AVC) system for pulsed current process, the bevel geometry and filler wire insertion technique on the welding process and weld bead. Experiments were carried out using 16” ASTM A36 pipes with ½” wall thickness and an automated orbital welding head. The results show that the AVC control must be appropriate for the current mode applied (pulsed or constant) in order to avoid arc length oscillation. Also, the counterboring operation during the bevel preparation increases the amount of material of the groove land and promotes less penetration. Regarding the metal transfer, the continuous bridge transfer mode is recommended for automated orbital GTAW welding and this is achieved with an appropriate AVC control method and filler wire positioning.

Resumo Os aditivos aromatizantes têm grande importância tecnológica para a indústria de alimentos. Contudo, poucas são as informações quanto as propriedades toxicológicas desses microingredientes, especialmente, em nível celular. No presente estudo avaliou-se, sobre as células meristemáticas de raízes de Allium cepa L., a toxicidade de um aditivo sintético líquido de aroma e sabor de chocolate, fabricado e amplamente comercializado em todo Brasil, e exportado para outros países da América do Sul. As concentrações de aromatizante avaliadas foram 100,00; 50,00; 25,00; 1,00; 0,50 e 0,25 µL/L, onde a maior concentração estabelecida foi cem vezes menor que a sugerida comercialmente para uso. Com base na interpretação dos resultados, a concentração 100 µL/L reduziu substancialmente a divisão celular dos meristemas nas 24 e 48 horas de exposição. As concentrações 100,00 a 0,50 µL/L demonstraram número significativo de prófases em detrimento as outras fases da divisão celular, indicando ação aneugênica, e induziram número significativo de alterações celulares, com ênfase a micronúcleos, broto nucleares e quebras cromossômicas. Nas condições de análises estabelecidas, com exceção a concentração 0,25 µL/L, o aromatizante de chocolate causou citotoxicidade, genotoxicidade e mutagenicidade aos meristemas radiculares.

Abstract Flavoring additives are of great technological importance for the food industry. However, there is little information regarding the toxicological properties of these micro-ingredients, especially at the cellular level. The present study used meristematic root cells of Allium cepa L. to evaluate the toxicity of a liquid, aroma and flavor synthetic chocolate additive, manufactured and widely marketed throughout Brazil and exported to other countries in South America. The flavoring concentrations evaluated were 100.00; 50.00; 25.00; 1.00; 0.50 and 0.25 µL/L, where the highest concentration established was one-hundred times lower than that commercially suggested for use. The concentration 100 µL/L substantially reduced cell division of meristems within 24- and 48-hours exposure. Concentrations from 100.00 to 0.50 µL/L resulted in a significant number of prophases to the detriment of the other phases of cell division, indicating an aneugenic activity, and induced a significant number of cellular changes, with emphasis on micronuclei, nuclear buds and chromosomal breaks. Under the established analysis conditions, with the exception of concentration 0.25 µL/L, the flavoring of chocolate caused cytotoxicity, genotoxicity and mutagenicity to root meristems.

Abstract The objective of this study was to evaluate the influence of drying treatment on the characteristics physical, chemical, technological properties and bioactive of turmeric flour. The flour was obtained from the drying of rhizomes in a forced air circulation oven at temperatures of 45, 55, 65 and 75 °C. The analyzes performed were: pH, instrumental color, microstructure, granulometry, water and oil absorption indices, water solubility indices, and antioxidant activity. The characteristics of the flours significantly affected were moisture, protein, lipid and ash contents. The antioxidant capacity with the DPPH radical, for flour at the drying temperature of 45 °C, presented the highest value 36.55 Mmol Trolox g-1, and 7686.32 Mmol FeSO4 g-1 the FRAP radical at 65 °C.The phenolic content varied according to the solvent applied to obtain the extract, the mean values of total phenolic compounds for each temperature were: 0.419, 0.332, 0.316, 0.283 mg GAEa 100 g-1for temperatures 45, 55, 65 and 75°C respectively. Water solubility index (WSI) and oil absorption index ranged from 12.45 g g-1 to 11.78 g g-1 and from 2.54 g g-1 to 2.49 g g-1, respectively, for temperatures of 45 °C and 75 °C. The results of the present study indicated that temperature influences the physicochemical and technological properties of turmeric flour.

ABSTRACT This study was conducted to characterize the transmission cycle of the tegumentary leishmaniasis (TL) in an old colonization area at Pernambuco State, Brazil. The aims were to identify autochthonous cases, sandflies fauna, domestic animals as possible reservoir hosts and the Leishmania species involved in this endemic area. A total of 168 suspected human cases of TL and 272 domestic animals (canine, feline, equine, goat, and sheep) were included. The sandflies were captured and identified by species. Patients were predominantly male and the average age was 37+18.1 years old. Of 85 patients who had skin lesions, 25.6% of them had direct positive smears for TL and 34 isolates were identified as Leishmania (Viannia) braziliensis. The confirmation for TL diagnosed by molecular detection (PCR) was almost three times more sensitive than the direct test [p < 0.001; PR = 2.72] associated with clinical examination. The Kappa test on PCR between two different specimens, biopsy, and skin lesion swab was 60.8% (p < 0.001). More than 200 specimens of sandflies (80 males and 159 females) were captured and identified as Lutzomyia whitmani (99.6%) and Lu. evandroi (0.4%). The detection of L. (V.) braziliensis by Real-Time PCR in the blood of a captured fed female was positive in 59.3% of Lu. whitmani. Of the 272 domestic animals included, 61.76% were male (n = 168). Thirty-six animals (13.2%) had lesions compatible with TL (34 dogs, 1 cat and 1 sheep) and 3 of them, all dogs, had lesions on the snout, showing destruction of cartilage and mucosa. The study suggests the participation of domestic animals as possible reservoirs. However, further studies are necessary to better understand the transmission cycle and take recommended measures in order to control the disease.

Neste trabalho apresentamos uma atividade de baixo custo que visa a investigação da força de arrasto, que atua na geometria de um disco, através das oscilações amortecidas de um sistema massa-mola. Utilizando discos de papelão de diferentes raios e controlando a massa do sistema oscilatório, mantendo-a fixa, estudamos a influência da variação exclusiva da magnitude da força de arrasto na dinâmica desse sistema, por meio da variação do raio do disco, mantendo todos os outros parâmetros acessíveis do sistema fixos. A técnica de vídeo-análise é utilizada para rastrear o movimento do sistema, levando o estudante a investigar e a extrair conclusões acerca da dependência funcional da força de atrito viscosa com o raio do disco, bem como a obter a constante elástica da mola e uma estimativa para a espessura dos discos.

In this work we present a low-cost activity that aims to investigate the drag force, which acts on the geometry of a disc, through the damped oscillations of a mass-spring system. Using cardboard disks of different radii and controlling the mass of the oscillatory system, keeping it fixed, we studied the influence of the exclusive variation of the magnitude of the drag force on the dynamics of this system, by varying the radius of the disk, keeping all the others fixed system accessible parameters. The video analysis technique is used to track the movement of the system, leading the student to investigate and draw conclusions about the functional dependence of the viscous frictional force with the radius of the disk, as well as to obtain the spring elastic constant and an estimate for the thickness of the disks.

ABSTRACT The Oil and gas exploration is one of the most strategic industrial sectors in the Brazilian economy. The discovery of deep water reserves adds more difficulty to the already problematic use of materials in equipment in extremely corrosive environments. With the objective of increasing the service life of the equipment, and consequently reducing the cost of maintenance and preventing against environmental catastrophes, it is common to use CRA claddings via welding processes, in which the nickel superalloy coatings stand out via the PTA welding process. In this context, the operation of internal cladding of risers becomes extremely complex due to the operational and metallurgical requirements imposed by the application. The present work aims at the development and empirical evaluation of the internal cladding procedure of risers with Nickel-based superalloy 625 via PTA welding process. From tests of cladding on plate, satisfactory preliminary parameters were reached for the performance of internal cladding tests on risers. From the adaptation of the welding parameters, comparative analyzes of three different procedures were carried out, with different weaving amplitude. Visual analysis and inspections were carried out via penetrating liquid and radiography, confirming the welding quality of all procedures performed. Still, proving the metallurgical quality of the developed procedures, analysis of chemical composition was carried out via EDX, presenting satisfactory results. Finally, a financial comparison of the process was elaborated, showing comparatively the consumption of powder and gas, and the time needed for internal cladding.

Abstract Numerous GMAW processes have appeared for one-pass welding of medium to high thickness. This concept originated in the 1980s with the T.I.M.E. technique and the 1990s and 2000s saw the emergence of Rapid Arc, Rapid Melt and Buried Arc techniques. These processes did not include any special control features, but rather parameter combinations to improve bead geometry. A new interpretation of the factors that are critical to achieving high performance GMAW (penetration) is presented herein. Tests with a voltage controlled power source with inductance control and the Rapid Arc process were conducted on bead-on-plate for high speed videography. Later, validation tests were conducted on butt joints, with the technique developed, with and without groove on AISI 1020, 3/8” thick steel plates. The power source may be of voltage control but has to provide a dynamic response able to sustain a metastable equilibrium of the molten pool applying the semi-keyhole technique. The technique developed was able to weld, in a single pass, 3/8” thick butt joint steel plates. The results showed that a power source, to achieve the GMAW buried arc condition, only needs to provide dynamic characteristics able to maintain the molten pool in a metastable equilibrium.

This study analyzed the average temperature value of the metallic droplets and weldpool of the Pulsed GMAW welding process using 309L-Si electrode as the addition metal. The study was based on the formulation and evaluation of pulsed waves, starting from the equation of energy constant (or detachment constant), and waveforms from two commercial welding sources, that were evaluated and reproduced. The technique of filming by high speed infrared radiation was used for evaluation. The results point to a higher droplet temperature for a lower intensity of pulse current, due to longer dwell time at this level, and also revealing that a longer time in the base phase may be responsible for a further heating of the fusion pool.

Abstract: Recent profusion of advanced GMAW process variants impairs understanding of the nature of each one, with the arc rotation technique among them. This paper’s objective is investigating influences of wire-electrode rotation over metal transfer mode and melting rate. A bead on plate experimental matrix was performed and electrical signals acquired in synchronicity with high speed videography. Impacts of electrode rotation were observed on welding voltage and current, whereby rotation speed exerts marked influence. Droplet short-circuiting frequency was affected, culminating in free-flight transfer mode for higher rotation speeds. Increase of melting rate was observed for lower electrical power, indicating efficiency enhancement of the process. Moreover, arc rotation proved to expand controllability of the thermal development of the workpiece. Results are supported by videothermography.