A new approach for Y-TZP surface treatment: evaluations of roughness and bond strength to resin cemen

Objective: This study aims to evaluate the effect of sonochemical treatment on the surface of yttria-stabilized tetragonal zirconia (Y-TZP) before and after the final sintering. Material and Methods: Twenty-eight Y-TZP discs were divided into four groups (n=7), according to surface treatment: PRE: pre-sintering sonication with 30% nominal power for 15 min; POS: postsintering sonication with 30% nominal power for 15 min; JAT: air abrasion with 50-μm alumina particles; and CON: control group with no treatment. The POS and JAT groups were sintered before sonication and the PRE group after sonication. Surface roughness was analyzed using confocal microscopy, after which resin cement cylinders were placed on the surface of the Y-TZP discs and subjected to mechanical microshear bond strength test until fracture. Surface roughness and microshear bond strength values underwent ANOVA and the Tukey tests. Results: The surface roughness values for the PRE group (299.91 nm) and the POS group (291.23 nm) were not significantly different (p≥0.05), statistically, and the surface roughness value of the JAT group (925.21 nm) was higher than those of PRE and POS (p=0.007) groups. The mechanical microshear bond strength test showed that there was no statistically significant difference between the groups (p=0.08). Conclusions: Therefore, the results showed that sonochemical treatment modifies the Y-TZP surface and is similar to the well-established sandblasting surface treatment regarding the strength of the bond with the resin cement

A new approach for Y-TZP surface treatment: evaluations of roughness and bond strength to resin cemen

Objective: This study aims to evaluate the effect of sonochemical treatment on the surface of yttria-stabilized tetragonal zirconia (Y-TZP) before and after the final sintering. Material and Methods: Twenty-eight Y-TZP discs were divided into four groups (n=7), according to surface treatment: PRE: pre-sintering sonication with 30% nominal power for 15 min; POS: postsintering sonication with 30% nominal power for 15 min; JAT: air abrasion with 50-μm alumina particles; and CON: control group with no treatment. The POS and JAT groups were sintered before sonication and the PRE group after sonication. Surface roughness was analyzed using confocal microscopy, after which resin cement cylinders were placed on the surface of the Y-TZP discs and subjected to mechanical microshear bond strength test until fracture. Surface roughness and microshear bond strength values underwent ANOVA and the Tukey tests. Results: The surface roughness values for the PRE group (299.91 nm) and the POS group (291.23 nm) were not significantly different (p≥0.05), statistically, and the surface roughness value of the JAT group (925.21 nm) was higher than those of PRE and POS (p=0.007) groups. The mechanical microshear bond strength test showed that there was no statistically significant difference between the groups (p=0.08). Conclusions: Therefore, the results showed that sonochemical treatment modifies the Y-TZP surface and is similar to the well-established sandblasting surface treatment regarding the strength of the bond with the resin cement

Influência da soldagem por caldeamento na tenacidade à fratura e na resistência à fadiga de trilhos ferroviários

O transporte ferroviário é um meio de transporte já consolidado na maior parte do mundo desde o início do século XIX. Atualmente o Brasil está reiniciando a construção de novas ferrovias e novos investimentos na área surgiram. Com vista nestas novas ferrovias, estudos sobre a caracterização mecânica e de mecânica da fratura dos trilhos se faz necessária e o estudo da tenacidade do material dos trilhos é um importante fator no conhecimento das propriedades dos trilhos. As ferrovias são construídas em linhas contínuas soldadas por um processo denominado caldeamento. Este trabalho teve como objetivo estudar a influência da junta soldada no comportamento à fratura do material de trilhos ferroviários do tipo TR-57. Por meio de ensaios de tração, fadiga por flexão rotativa, impacto Charpy instrumentado e de tenacidade à fratura foi feita a caracterização do material e análise das influências da junta soldada nas características de tenacidade à fratura dinâmica aparente e de tenacidade à fratura do material dos trilhos. Os resultados mostraram que o material dos trilhos segue uma tendência de queda da tenacidade a fratura na região da junta soldada, além de mostrar que o volume de material ensaiado tem uma grande importância na escolha dos ensaios a serem realizados para a caracterizaçãoRail transportation is an already worldwide consolidated means of transportation since the beginning of 19th century. Nowadays Brazil is restarting to build new railways and investments for the area are appeared. With this new railways, studies on the mechanical and fracture mechanics characteristics of rails are needed and the rail’s material toughness is an important factor on knowing rails properties. Railways are built in continuous welded lines by a welding process called flash-butt welding. This work has as objective to study the welded joint influence on the fracture toughness of the brazilian TR-57 rails material. Using traction, rotate bending fatigue, instrumented Charpy impact and fracture toughness tests the material characterization and the welded joint influence on the apparent dynamical fracture toughness and fracture toughness of the rail’s material. The results showed that the rail’s material followed a fall tendency of the fracture toughness inside the welded joint, and also showed that the tested material volume has a major influence on choosing the tests to be used for characterizationCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES