Heat treatments and geometries have a significant influence on the mechanical behavior of endodontic files. Finite element analyses were performed to verify the effects due to each of these parameters in NiTi files. Two designs and three NiTi atomic structures (resultant from different heat treatments) were selected for this study. The geometries of the ProTaper Next X1 and ProTaper Universal S2 files, and the structures of fully austenitic (conventional superelastic), austenite treated, and fully R-phased were used. The mechanical responses were evaluated under flexion and torsion loading conditions described by ISO 3630-1 specification. According to the results, the design of the X1 file exhibit higher flexibility in comparison to the S2 model. Under torsional loads, S2 showed higher stiffness. The structures of fully austenitic showed the least flexibility under flexion and the highest torsional stiffness. The stress levels reached for the austenitic condition were uppermost. The treated condition that resulted in a fully R-phase file usually presented a higher level of flexibility with lower stress levels, indicating a longer life in fatigue when compared to the other treatments.
6Elaine Carballo Siqueira Corrêa 7 Resumo Nas últimas décadas a crescente demanda por carros mais seguros, econômicos e menos poluentes exigiram das montadoras, siderúrgicas e comunidade científica investimentos na pesquisa e no desenvolvimento de novos materiais, tais como os aços avançados de alta resistência. Dentro deste contexto, neste trabalho foi realizada a análise da microestrutura e das propriedades mecânicas de um aço bifásico na condição inicial e submetido a tratamentos térmicos com aquecimento na região intercrítica e resfriamento brusco. Foram analisadas a proporção dos constituintes na microestrutura e as propriedades mecânicas por meio de microscopia óptica e eletrônica de varredura, de difração de raios X, dureza e de tração. Observou-se, em geral, que o aumento da temperatura intercrítica levou a uma elevação da fração de martensita e, consequentemente, influenciou de forma a aumentar os valores de dureza, resistência mecânica e diminuir a ductilidade. Palavras-chave: Aço bifásico; Tratamento intercrítico; Microestrutura; Propriedades.
INFLUENCE OF INTERCRITICAL TEMPERATURE IN THE MICROSTRUCTURE AND THE MECHANICAL PROPERTIES OF A DUAL PHASE STEEL AbstractIn recent decades the increasing demand for safer, economical and less polluting cars demanded of automakers, steelmakers and scientific community investments in research and development of new steels, such as advanced high strength steels. The aim of this work was the analysis of the microstructure and the mechanical behavior of a dual phase steel, in the initial condition and subjected to thermal processing with intercritical heating and quenching. The ferrite-martensite fraction in the material was evaluated by optical and scanning electron microscopy techniques and its influence in the mechanical properties was analyzed through hardness and tensile tests. It was observed that the increase of the intercritical temperature raised the fraction of martensite and thus led to an increase in hardness, yield strength and ultimate tensile strength and to a decrease in the elongation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.