Ultra high molecular weight polyethylene (UHMWPE) is one of the most important engineering materials owing to outstanding properties like impact strength and abrasion resistance. However, the relatively low Young´s modulus restricts some application and the use of fillers may be a suitable way to overcome this. The fillers can influence the photo stabilization of the compound, as it occurs to other polymers. Neat UHMWPE and its composites with 1 and 10% of iron ore fine were exposed to ultraviolet radiation for up to 33 days and then tested for mechanical properties. The stress-strain behaviour changed with degradation, with an evident necking and strain hardening region that was not observed before exposure, due to a reduction in entanglements density. From the tensile results, the filler may have a protection action against UV, particularly when a loading of 10% was present. Complementary analyses were performed, including X-ray diffraction, DSC and SEM.
Publicado pela ABM. Este é um artigo publicado em acesso aberto (Open Access) sob a licença Creative Commons Attribution, que permite uso, distribuição e reprodução em qualquer meio, sem restrições desde que o trabalho original seja corretamente citado.a ResumoNas diversas operações de conformação é necessária a combinação de diferentes esforços mecânicos até que sejam alcançadas a forma e as dimensões de um produto. A severidade dessas mudanças no modo de deformação pode ocasionar modificações inesperadas no comportamento mecânico de um material, restringindo o uso do mesmo em processos industriais. Considerando essa abordagem, este trabalho apresenta o estudo da conformabilidade do aço inoxidável ferrítico AISI 409 sob duas rotas de processamento mecânico, com o objetivo de analisar a evolução da resistência mecânica e da ductilidade desse aço. Neste caso, chapas do aço AISI 409 foram submetidas a uma combinação de tensões compressivacisalhante (laminação), tração e cisalhamento (de modo direto e reverso) de forma a promover mudanças severas no modo de deformação plástica. Os resultados revelaram a influência da quantidade de pré-deformação efetiva (variando de 3,88% a 16,50%), do estado inicial do material (recozido e laminado a frio), do modo de deformação plástica (laminação, tração e cisalhamento) no endurecimento e na ductilidade do aço AISI 409, exibindo ainda transientes na taxa de encruamento associados com o modo de pré-deformação em laminação a frio. Palavras-chave: Aço AISI 409; Cisalhamento; Trajetória de deformação.
The mechanical behavior of metallic materials depends on several variables, such as the material structural characteristics, the process parameters, the temperature, the strain rate and the anisotropy features due to strain paths in different metal forming operations. Considering the last one, the effect of shear direction loading on the work-hardening after the rolling/shearing loading of a ferritic stainless steel, AISI 409, was investigated in this work. The annealed AISI 409 sheets were predeformed by cold rolling up 0.19 effective strain and then sheared at three different directions: at 0°, 45° and 90° from the original rolling direction. The samples were characterized through tensile, shear and Vickers microhardness tests while the study of crystallographic texture was performed using the electron backscatter diffraction (EBSD) technique. The work-hardening behaviour of the material was analyzed considering the work-hardening rate and the Hollomon work-hardening exponent after each strain path change applied to the AISI 409 steel. The results indicated the presence of preferential crystallographic orientation and the occurrence of transients on the work-hardening rate mainly for the sample sheared at 45° from the original rolling direction due to structural arrangements assumed by the AISI 409 steel after the strain path changes.
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