Ensino através do desenvolvimento de projetos: construção de uma mini furadeira artesanal (micro retifica) / Education through project development: construction of a handmade mini drill (micro rectify)

  O ensino da engenharia deve ter como objetivo proporcionar aprendizagem significativa, contextualizada e orientada para o uso das tecnologias contemporâneas. Também deve favorecer o uso de recursos de inteligência, gerando habilidades de resolução de problemas e conduzindo projetos em vários segmentos do setor produtivo (Moura; Barbosa, 2014). Nesse contexto, o trabalho a seguir foi desenvolvido em sala de aula por estudantes de graduação em engenharia mecânica da Universidade Federal do Pará para a área de usinagem de metais, com o objetivo de obter novos conhecimentos na área de usinagem, bem como o estímulo à criação de novas tecnologias, resolvendo problemas inerentes à vida cotidiana. Essa atividade foi alcançada no protótipo de uma broca 100% artesanal e totalmente funcional, capaz de fazer furos em papelão e madeira de espessuras finas, como palitos de sorvete e compensado, com boa ergonomia e fácil manuseio.  

Influence of thermal parameters on the dendritic arm spacing and the microhardness of Al-5.5wt.%Sn alloy directionally solidified

Al-Sn alloys are widely used in tribological applications. In this study, thermal, microstructural and microhardness (HV) analysis were carried out with an Al-5.5wt.%Sn alloy ingot produced by horizontal directional transient solidification. The main parameters analyzed include the growth rate (V L) and cooling rate (T R).These thermal parameters play a key role in the microstructural formation. The dendritic microstructure has been characterized by primary dendritic arm spacing (λ1) which was experimentally determined and correlated with V L, and T R. The behavior presented by the Al-5.5wt.%Sn alloy during solidification was similar to that of other aluminum alloys, i.e., the dendritic network became coarser with decreasing cooling rates, indicating that the immiscibility between aluminum and tin does not have a significant effect on the relationship between primary dendritic arm spacing and the cooling rate. The dependence of the microhardness on V L, T R and λ1 was also analyzed. It was found that for increasing values of T R, the values of HV decrease. On the other hand, the values of HV increase with increasing values of λ1

Solidification thermal parameters and dendritic growth during the horizontal directional solidification of Al-7wt.%Si alloy

The main purpose of this work is to investigate the influence of thermal parameters such as growth rate (V L) and cooling rate (T R) on the primary dendrite arm spacings (λ1) during the horizontal transient directional solidification of Al-7wt.%Si hypoeutectic alloy. The primary dendrite spacings were measured along the length of the samples and correlated with these thermal parameters. The variation of dendrite spacings is expressed as a power law function of V L and T R given by the formulas λ1 = 55(V L)-1.1 and λ1 = 212 (T R)-0.55, respectively. A comparative study between the results of this work and those from the literature proposed to investigate these dendrite spacings during the upward and downward vertical directional solidification of Al-7wt.%Si alloy is also conducted. Finally, the experimental data are compared with some predictive dendritic models from the literature