The effect of a surface treatment by Nd:YAG laser irradiation on the fatigue behavior of Ti-6Al-4V ELI was studied. Axial fatigue tests were performed to obtain S-N curves in polished and laser treated conditions. Roughness measurements and scanning electron microscopy were used to characterize the features of the modified surface. A reduction in the fatigue strength of around 35% was obtained after the laser treatment of the material surface. Although the surface roughness was in the micrometer scale, a notch effect was suggested to be the reason for the deleterious influence of the laser on the fatigue strength. The reduction in the fatigue strength obligatory demands redesign of implants for laser modified surfaces of Ti-6Al-4V alloy.

The objective of this investigation was to evaluate the influence of surface modification by femtosecond laser (with average fluence of 0.6 J/cm2 and scanning speed of 0.1 mm/s) on the fatigue resistance of Ti-6Al-4V ELI alloy. A significant reduction in the fatigue strength of the material modified by laser was observed. Residual tensile stresses generated during surface modification were negligible, presenting lower values than those found on the unmodified surface. Based on a recently developed and published prediction model, the reduction of the fatigue strength was ascribed to the surface roughness created during the laser treatment of the alloy. An evidence was that the fatigue crack nucleation occurred in the modified region, rather than at the edge of the rectangular specimens as in the untreated condition.

Nanotechnology is seeing as having potential to raise benefits to several research and application areas. Recently materials with nanostructured surfaces of nanopores, nanotubes and nanowires have become an important investigation field, since their chemical and physical properties may be substantially different from those of the corresponding substrate. In face of the necessity of assuring that such modifications are not deleterious to the mechanical behavior, the purpose of this work was to evaluate the fatigue performance of CP-Ti grade 2 with the surface modified by the formation of nanotubes on their different crystalline structures. The nanotubes layers were produced by anodic oxidation using a potential of 20V during 1h and a solution of glycerol, H2O and NaF, and analyzed by scanning electron microscopy. In order to obtain the anatase and rutile structures, annealing treatments were respectively performed at 450°C and 650°C. The axial fatigue tests were conducted in physiological solution at 37°C following the stepwise load increase approach. When compared to the material without surface modification (polished surface), the results showed that the anatase phase did not affect the fatigue response, maintaining the fracture stress in 500 MPa, whereas the rutile phase caused a decrease to 450 MPa.

Desde 2004, o CCDM realiza ensaios mecânicos em implantes ortopédicos. Os componentes mais utilizados - e conseqüentemente ensaiados - são parafusos, comumente fabricados com aço inoxidável ASTM F138, ou liga de titânio ASTM F136. O objetivo desse trabalho é avaliar os resultados referentes aos ensaios de torção em parafusos metálicos, dando um panorama das propriedades médias dos produtos ensaiados. Tais resultados provieram de material fornecido por 15 fabricantes diferentes, num total de 451 ensaios, que cobriram quase todo o espectro de parafusos utilizados em implantes: ortodontia, parafusos pediculares, parafusos para ossos corticais e esponjosos, parafusos de bloqueio e de ancoragem. A dispersão dos resultados de ângulo de ruptura é elevada. A maioria dos resultados, no entanto, apresenta valores acima do mínimo exigido pela norma ASTM F543.

Since 2004, the CCDM lab performs tests on orthopedic implants. The most used (and tested) implants are screws. These are commonly made either of austenitic stainless steel ASTM F138 or of Ti-6Al-4V alloy ASTM F136. The aim of this study was to evaluate the obtained torsion test results and to present an overview of the average product properties. The results stand for 15 different producers, and 451 samples, covering almost all the screw types utilized in implants: orthodontic, anchor and tibial nail applications, and designs for pedicular, cortical and cancellous bones. The dispersion in angle of rupture was high. Nevertheless the majority of the results lied above the minimum required by the ASTM F543 standard.