EM - Escola de Minas
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/6
Notícias
A Escola de Minas de Ouro Preto foi fundada pelo cientista Claude Henri Gorceix e inaugurada em 12 de outubro de 1876.
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Resultados da Pesquisa
Item Laser surface treatment for enhanced titanium to carbon fiber‑reinforced polymer adhesion.(2017) Palavra, Armin; Coelho, Bruno Nazário; Hosso, Jeff Th. M. de; Lima, Milton Sérgio Fernandes de; Carvalho, Sheila Medeiros de; Costa, Adilson Rodrigues daThe adhesion between carbon fiber-reinforced polymer (CFRP) and titanium parts can be improved by laser surface texturing before gluing them together. Here, a pulsed Nd:YAG laser was employed before bonding of the textured surfaces using an epoxy paste adhesive. To investigate the influence of the laser parameters, the roughness of the surfaces were characterized and correlated to the wettability, by measuring the contact angles of water droplets. Scanning electron microscope (SEM) characterization was also performed showing that under careful conditions, the fiber structure could be maintained. Tensile tests were performed to evaluate the influence of the laser treatment parameters on the joining efficiency. The lap-joint tensile strength tests presented the best results when the titanium surfaces were treated using 5.03 × 10−3 J pulses and the CFRP sample treated with 5.03 × 10−4 or 5.03 × 10−3 J or even using a virginal CFRP surface. Using a virginal CFRP surface, the critical load of fiber delamination was increased and as a consequence the tensile strength attains the highest level of 8.2 MPa.Item Erosion by solid particle impingement : experimental results with cast-iron, laser-treated surfaces.(1997) Costa, Adilson Rodrigues da; Vilar, RuiThe surfaces of cast-iron specimens have been modified by CO2 laser processing in order to enhance their hardness, providing different surfaces for wear behaviour studies. Various laser heat treatmentswere performed in order to generate distinctmicrostruc- tures. Based on previous tests, interaction time and power density usedwere 0.5 s and 0.4 kW/mm2, respectively. Alloyingwith pure Cr allowed microstructure and the chemical composition of the material to be modified in order to attain the desired properties. Chromium^iron carbides, (Cr,Fe)7C3, formed ``in situ'', during laser surface melting, by reaction with carbon of the cast iron, change the wear properties. These carbides were detected by conventional X-ray diffraction. The expected effect of a carbide-rich structure on the erosion behaviour is to decrease themass loss by erosionmechanisms. Erosion was done by SiC erosive blast impin- gement tests. In this method the SiC particles were accelerated in a compressed air stream along a nozzle and projected against the surface to be eroded. After the laser treatment, the erosion behaviour of material was evaluated by measuring the weight loss. The wear test was complemented by SEMmicrostructural observations. Experiments performed in this work show that, in erosion, the mass loss of material does not depend on hardness as proposed by the accepted tribological theories. The worst behaviour was observed for laser-treated surfaces. Embedding of erodent particles plays a decisive role in blast erosion performance of the surfaces studied.