China
Africa
Explore chapters and articles related to this topic
Reduction and Fixation of Sacroiliac joint Dislocation by the Combined Use of S1 Pedicle Screws and an Iliac Rod
Published in Kai-Uwe Lewandrowski, Donald L. Wise, Debra J. Trantolo, Michael J. Yaszemski, Augustus A. White, Advances in Spinal Fusion, 2003
Kai-Uwe Lewandrowski, Donald L. Wise, Debra J. Trantolo, Michael J. Yaszemski, Augustus A. White
HA coating of loaded pedicle screws has been evaluated in two experimental studies. In a study focusing on the mechanical effects, 13 sheep were operated on with destabilizing laminectomies at two levels, L2-L3 and L4-L5 [44]. Two instrumentations with four pedicle screws in each were used for stabilization. Uncoated screws (stainless steel SAF 2507) or the same type of screws coated with plasma-sprayed HA were used in either the upper or the lower instrumentation in a randomized fashion. Four sheep were examined immediately after the application of the screws, three sheep at 6 weeks, and four sheep at 12 weeks. Two sheep were euthanized early due to complications. The pull-out resistance was recorded in two HA-coated and two standard screws in each animal. The maximum pull-out resistance was higher for the HA-coated screws at 0 (p < 0.02) and at 12 weeks (p < 0.01) when compared to the uncoated screws, while there was no significant difference between the groups at 6 weeks. The authors concluded that the higher pull-out resistance for HA-coated screws at 0 weeks was caused mainly
On the machinability of selective laser melted duplex stainless steels
Published in Materials and Manufacturing Processes, 2022
Karl Peter Davidson, Guy Littlefair, Sarat Singamneni
Super duplex stainless-steel grade SAF 2507 was used in this investigation in a wrought state and as produced by SLM. Powder materials used for SLM samples were supplied by Sandvik Osprey Ltd, UK as per the composition listed in Table 1, with a spherical morphology and mean particle diameter of 34.0 µm. All machining trials were based on drilling, considering the ease of producing the relatively expensive SLM samples. A two-stage experimental evaluation scheme as depicted in Fig. 1 was implemented. Initial experiments were aimed at a comparative examination of the machinability of wrought DSS against the laser melted counterparts with a specific energy density. This is then followed by an estimate of the role of energy density used in the laser melting process on the mechanism of machining, established from machining trials based on drilling experiments. Next, a comparative assessment of the machinability of as-built and solution annealed SLM samples was undertaken based on the samples produced with the optimum energy density levels ascertained form the initial experiments, with which the Archimedes densities achieved were above 98%. The power and scan speed settings associated with the laser energy densities and the machining process parameter combinations are listed in Fig. 1.