Investigation of the influence factors on distortion in induction-hardened steel shafts manufactured from cold-drawn rod

In this study, the distortion of steel shafts was investigated before and after induction hardening. Several essential influencing factors in the manufacturing process chain regarding cold drawing, cutting method, notches on the shafts, and induction hardening were analyzed by design of experiment (DoE). Further necessary examinations of microstructures, hardness profile, segregation of chemical composition, and residual stress state were conducted for understanding the distortion behavior. The results of the statistical analysis of the DoE showed that the drawing process is the most important factor influencing distortion. The surface hardening depth of induction hardening is the second main factor. The relationship between inhomogeneities in the work pieces and the distortion was finally discussed

“Paisagens pedagógicas”: uma pesquisa com professores de Artes Visuais

This paper presents the thoughts around an academic research entitled pedagogical landscapes, developed between the years 2016 and 2020 at Universidade do Estado de Santa Catarina (UDESC). The research investigated the pedagogical practices and their developments among Visual Arts teachers in the region of Florianópolis (SC).  The potency of artistic and pedagogical practices permeates the present writing, as it amplifies the uncertainties and anxieties experienced by the teachers in this area which, despite the countless advances, is still understood as a mere activity in which actions have no function for the lives of the students and of people in general. Cartography, as a research method that finds its clues as it advances, reveals the concerns, desires and motivations of a teaching experience that triggers affections, as it draws intersubjective lines.Este texto apresenta as reflexões acerca de uma pesquisa acadêmica intitulada paisagens pedagógicas, desenvolvida entre os anos de 2016 e 2020 na Universidade do Estado de Santa Catarina (UDESC). A pesquisa investigou as práticas pedagógicas e seus desdobramentos junto a professores de Artes Visuais na região de Florianópolis (SC). A potência de práticas artísticas e pedagógicas de professores atravessa a escrita, amplificando as incertezas e os anseios vividos por eles nessa área de ensino que, apesar dos inúmeros avanços, ainda é compreendida como mera atividade de ações sem nenhuma função para a vida dos estudantes e das pessoas em geral. A cartografia, como método de pesquisa que vai encontrando suas pistas no decorrer do caminho, revela inquietações, desejos e motivações de uma docência que dispara afetos, traçando linhas intersubjetivas

Avaliação dos efeitos de tensões residuais através da remoção de material

The residual stresses imposed during the manufacturing process of a component are one of the main potential carriers for the appearance of distortion. In this work experiments concerning dimensional changes of bars after material removal were carried out in order to estimate the residual stress level stored as a consequence of the manufacturing route. The material removal was accomplished after each processing step. The samples were taken after five different steps of a combined colddrawing: pre-straightening, shot-blasting, cold-drawing, straightening and polishing by crossed rolls. The last step was varied according to the angles between crossed rolls: 16°, 17° and 18°. The material removal was accomplished in such a way to leave a material portion corresponding to a depth of 1/6 or 1/2 of the diameter of the bar. The cuts were done at different angular positions to characterize imposed peripheral inhomogeneities (0°, 90°, 180°, 270°). Due to the material removal, the residual stresses will be rearranged in the remaining part, which leads to the appearance of a deflection of the remaining material. This bending was used to try to estimate the residual stress levels previously present in the bars. Key words: cold-drawing, residual stress, deflection methods.As tensões residuais impostas durante o processo de manufatura de um componente são um dos maiores potenciais para o aparecimento de distorções. Neste trabalho os experimentos concentraram-se nas mudanças dimensionais de barras de aço após a remoção de material, esta remoção foi realizada objetivando-se estimar as tensões residuais presentes nas barras em conseqüência do processo de fabricação. A remoção de material foi realizada após cada etapa do processo de fabricação. As amostras foram retiradas de cinco diferentes estágios da trefilação combinada, sendo elas: pré-endireitamento, jateamento, trefilação, endireitamento e polimento por rolos cruzados (“PERC”). No último estagio houve variações no ângulo entre os rolos: 16°, 17° e 18°. As remoções de material foram realizadas de nodo a deixar uma parcela correspondente a uma profundidade de 1/6 ou ½ do diâmetro da barra. Os cortes foram realizados em diferentes posições angulares para caracterizar heterogeneidades impostas durante o processo (0°, 90°, 180°, 270°). Devido à remoção de material as tensões residuais são rearranjadas na parte restante que conduz ao aparecimento de uma deflexão do material restante. Esta deflexão foi usada para estimar os níveis de tensão residuais presente previamente nas barras. Palavras-chave: trefilação combinada, tensões residuais, métodos de deflexão

Análise do “potencial de distorção” de barras cilíndricas de aço ABNT 1048

The residual stresses can affect positive or negatively the behavior of the mechanical components. These residual stresses also represent one of the main potentials for the distortion (which are bending and dimensional changes) in mechanical components during the manufacture. Therefore, the determination of the distribution and the control of these residual stresses in each stage of the manufacturing process is of great importance. In this work, an analysis of the variation of the residual stresses were accomplished in cold-drawed bars of AISI 1048 steel due to the manufacturing process. The bars were analyzed by X-ray diffraction and hole-drilling to characterize the residual stresses. Starting from the values of strains obtained, the hoop and longitudinal residual stresses were calculated for each tested point. With this work, a detailed view of the development of stress in the surface area of bars after the process steps was obtained. Key words: cold drawing, residual stresses, x-ray diffraction, hole-drilling.As tensões residuais podem afetar positiva ou negativamente o desempenho dos componentes mecânicos. Estas tensões residuais também representam um dos principais potenciais para a distorção (isto é empenamentos e mudanças dimensionais) em componentes mecânicos durante a manufatura. Por isso são de grande importância a determinação da distribuição e o controle destas tensões residuais em cada etapa do processo de manufatura. Neste trabalho, foram realizadas análises da variação das tensões residuais em barras trefiladas de aço ABNT 1048 em decorrência do processo de fabricação. As barras foram analisadas por difração de raios-X e hole-drilling para caracterizar as tensões residuais. A partir dos valores de deformações obtidos, foram calculadas as tensões residuais nas direções longitudinal e tangencial para cada ponto ensaiado. Com este trabalho uma visão detalhada do desenvolvimento de tensões na região superficial de barras após as etapas do processo foi obtida. Palavras-chave: trefilação, tensões residuais, difração de raios-X, método do furo cego

Evaluation of the residual stress state of 42crmo4 steel sheets in a production line

The residual stress state of a mechanical component is an important factor in its production planning and in estimates of its lifecycle since it can be responsible for geometric distortions and degradation of fatigue properties. Therefore, the development of reliable methods for non-destructively quantifying these stresses remains in the interest of most manufacturing industries; Barkhausen magnetic noise measurements have been investigated in several applications and remains a viable option. However, its effective implementation has occurred mostly in components with simple geometries and insignificant microstructural gradients; even in these cases, successful industrial adoption of the method depends on previous calibration with samples that are often difficult and costly to prepare and validate. This work aims at investigating the capability of the method of characterizing the residual stress state in a simple but generally useful application: samples of hot-rolled steel sheets collected at two different stages of processing in an industrial mechanical conformation and heat treatment plant. In this analysis Barkhausen noise measurements were compared to X-ray diffraction results, and statistical analysis tools were used to correlate the results

Microstructure and wear properties of a low carbon bainitic steel on plasma nitriding at different N2-H2 gas mixtures

For the first time, the influence of gas mixture on first damage resistance of a plasma nitrided DIN 18MnCrSiMo6-4 bainitic steel was investigated. Samples were nitrided at 500 °C with three different N2 -H2 gas mixtures, containing 5, 24, and 76 vol.% N2 . Samples were characterized concerning the resulting roughness, microstructure, compound layer’s phase composition, residual stresses in the diffusion zone, and surface hardness. Tribological ball-on-flat tests were carried out in reciprocal mode using zirconia as ball material for friction coefficient and the compound layer resistance until the first damage. The test results were evaluated statistically by analysis of variance (ANOVA). As the amount of nitrogen in the gas mixture decreases, the ε-Fe2-3(C)N content in the compound layer decreases. A γ’-Fe4 N monophasic compound layer was achieved at 5 vol.% N2 gas mixture. The diffusion zone as expected presented compressive residual stresses with the highest values near the surface. In the tribological tests, better results were obtained for 5 and 24 vol.% N2 in the gas mixture as higher amounts of γ’-Fe4 N were formed. The 76 vol.% N2 gas mixture led to a brittle behavior, due to the biphasic compound layer (γ’-Fe4 N and ε-Fe2-3(C)N) with a predominant content of ε-Fe2-3(C)N

Mechanical and optical properties of conventional restorative glass-ionomer cements - a systematic review

Objectives To perform a systematic review of test methodologies on conventional restorative glass-ionomer cement (GIC) materials for mechanical and optical properties to compare the results between different GICs. Material and Methods Screening of titles and abstracts, data extraction, and quality assessments of full-texts were conducted in search for in vitro studies on conventional GICs that follow the relevant specifications of ISO standards regarding the following mechanical and optical properties: compressive strength, flexural strength, color, opacity and radiopacity. Sources The Latin American and Caribbean Health Sciences (LILACS), Brazilian Bibliography of Dentistry (BBO) databases from Latin-American and Caribbean System on Health Sciences Information (BIREME) and PubMed/Medline (US National Library of Medicine - National Institutes of Health) databases were searched regardless of language. Altogether, 1146 in vitro studies were selected. Two reviewers independently selected and assessed the articles according to pre-established inclusion/exclusion criteria. Among all the properties investigated, only one study was classified as being of fair quality that tested compressive strength and was included. It was observed that many authors had not strictly followed ISO recommendations and that, for some properties (diametral tensile strength and microhardness), there are no guidelines provided. Conclusions It was not possible to compare the results for the mechanical and optical properties of conventional restorative GICs due to the lack of standardization of studies

Mechanical and optical properties of conventional restorative glassionomer cements - a systematic review

Objectives: To perform a systematic review of test methodologies on conventional restorative glass-ionomer cement (GIC) materials for mechanical and optical properties to compare the results between different GICs. Material and Methods: Screening of titles and abstracts, data extraction, and quality assessments of full-texts were conducted in search for in vitro studies on conventional GICs that follow the relevant specifications of ISO standards regarding the following mechanical and optical properties: compressive strength, flexural strength, color, opacity and radiopacity. Sources: The Latin American and Caribbean Health Sciences (LILACS), Brazilian Bibliography of Dentistry (BBO) databases from Latin-American and Caribbean System on Health Sciences Information (BIREME) and PubMed/Medline (US National Library of Medicine - National Institutes of Health) databases were searched regardless of language. Altogether, 1146 in vitro studies were selected. Two reviewers independently selected and assessed the articles according to pre-established inclusion/exclusion criteria. Among all the properties investigated, only one study was classified as being of fair quality that tested compressive strength and was included. It was observed that many authors had not strictly followed ISO recommendations and that, for some properties (diametral tensile strength and microhardness), there are no guidelines provided. Conclusions: It was not possible to compare the results for the mechanical and optical properties of conventional restorative GICs due to the lack of standardization of studies

Análise da rugosidade superficial de barras de aço SAE 1045 após torneamento

Neste trabalho foram investigadas as influências de alguns dos principais fatores do torneamento sobre oacabamento da superfície e a rugosidade de uma peça torneada. Foram analisadas barras de aço SAE 1045torneadas em um torno controle numérico computadorizado (CNC), com auxílio da técnica de Planejamentode experimentos (DOE) para formar trinta e duas diferentes combinações de fatores, analisar suas interaçõese sua influência no acabamento de cada amostra. Os fatores de usinagem investigados foram: (1) avanço, (2)velocidade de corte, (3) raio de quina, (4) ângulo de saída e (5) região de medição da rugosidade. Por meiodo DOE foram realizadas duas análises fatoriais: a primeira avaliou a influência dos cinco fatores na rugosidademédia, representada por Ra, e a segunda avaliou a eficácia de cada conjunto de fatores em obter o acabamentoalvo. Para isso, foi criado um índice que relaciona a rugosidade teórica de cada processo com a rugosidademedida pelo rugosímetro. Os resultados mostraram que o avanço e o raio de quina possuem elevadoefeito padronizado em ambas as análises. Porém, enquanto a aplicação de um menor avanço (ou maior raiode quina) produziu superfícies com baixa Ra, por outro lado também prejudicou a eficácia do torneamento,pois contribuiu para obtenção de uma rugosidade significativamente maior que a rugosidade teórica. Já ofator velocidade de corte foi benéfico ao processo em ambas as análises. Não foi encontrada relevância daregião de medição da rugosidade sobre a rugosidade média, Ra.Palavras-chave: Acabamento, rugosidade, torneamento, SAE 1045