São Bernardo do Campo, Brazil
São Bernardo do Campo, Brazil

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Magnabosco R.,Fundacao Educacional Inaciana FEI | Dos Santos D.C.,Fundacao Educacional Inaciana FEI | Dos Santos D.C.,Brazilian Technological Institute of Aeronautics
Journal of Materials Research and Technology | Year: 2012

This paper is based on the study of intermetallic phase formation during aging between 850 C and 950 C, for periods up to 5 min; those treatments were conducted in liquid aluminum bath, allowing fast heating of the small sized specimens. It was found that backscattered electron images could be used in the automatized routines of quantitative stereology of intermetallic phases and nitrides found in duplex and superduplex stainless steels. A measurable intermetallic phase fraction was observed just after 1 min aging in the studied temperatures, but it was not possible to distinguish sigma and chi phases from the observed intermetallic phases. Nitrides were also observed, but they were probably formed in steel manufacturing, since there was no significant influence of aging on its volume fraction. © 2012 Elsevier Editora Ltda. and Brazilian Metallurgical, Materials and Mining Association.


Donato G.H.B.,Fundacao Educacional Inaciana FEI | Bianchi M.,Fundacao Educacional Inaciana FEI
Journal of Materials Research and Technology | Year: 2012

Conventional yield criteria for ductile materials, such as Tresca and von Mises, predict that yielding is independent on the hydrostatic stress state (pressure), which means that tensile and compressive stress-strain behaviors are considered equal and are equally treated. This approach is reasonable for ductile metallic materials but sometimes inaccurate for polymers, which commonly present larger compressive yield strength, therefore being characterized as uneven. Some pressure dependent theories are available, but there is no consensus concerning the choice of the most appropriate criterion, its use and benefits. As a step in the direction of improving structural integrity practices taking advantage of unevenness, this work performs three key-activities: i) first, a critical review about existing theories and its accuracy; ii) second, a series of experiments under tension and compression including four selected polymers (PA-66, PA-6, PP, and HDPE) to assess real unevenness levels; iii) third, a numerical evaluation of the potential benefits of using modified criteria. Stress states, safety, and stiffness were evaluated for a typical application to illustrate the proposals. Mass reductions up to 39% could be achieved even with simple geometric changes, while keeping original safety and stiffness levels. © 2012 Elsevier Editora Ltda. and Brazilian Metallurgical, Materials and Mining Association.

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