RESUMO
Bone drill chips that are collected during implant site preparation can be reused as autologous bone-grafting material for alveolar ridge augmentation. This study characterized five market-leading implant drill sets regarding their geometric properties and ability to produce vital bone chips. The drill geometry of each tool of five commercial implant drill sets was characterized while using optical profile projector devices and SEM. Bone chips were collected during the in vitro preparation of porcine jaw bone with the various drill sets. Produced bone chip masses were measured. The bone chips were cultured in vitro and the number of outgrown cells was determined and measurand for vitality. Furthermore, the thrust force and cutting torque were recorded to examine the mechanical loads of the manual drilling process. The tool geometry and set configuration of one out of five implant drill sets appears to be superior regarding chip mass, vitality, and thrust force. It could be proven that there is a correlation between vitality and thrust force. The thrust force is influenced by the cutting behavior of the tool, which in turn depends on the geometry of the tool. The tool geometry has an influence on the vitality of the augmentation material due to this relationship.
RESUMO
The industrial application of laser materials processing methods is still far ahead of research into the physical phenomena occurring during these processes. In particular, the effect of high temperatures on the energy coupling of laser irradiation of metals is poorly understood. However, most processes in laser materials treatment involve temperatures above the melting point or even cause evaporation. This study therefore evaluates the effect of high temperatures on the energy coupling efficiency of stainless steel experimentally for three typical laser wavelengths (515 nm, 1.07 µm, 10.6 µm). As a result, it is shown that the effect of temperature on the energy coupling efficiency depends on the wavelength. In this context the relevance of the X-point phenomenon known from the emissivity theory could be demonstrated for laser material processing. Further, the effect of a process-induced surface oxidation is analyzed. At temperatures above 650 °C the energy coupling efficiency dramatically increases to around 65% at melting point and stays at this high level even in the liquid phase.
RESUMO
Synergistic effects during hybrid laser-arc welding may cause increased process efficiencies. However, the basic interactions behind these effects are still being discussed, with some contradictory reports. In this study, particular welding parameters of interest were systematically varied to further the understanding of involved phenomena. The experimental trials are evaluated regarding their synergistic achievements in terms of process efficiency, melting efficiency and energy coupling efficiency using a factorial two-level Design-of-Experiment (DoE) approach. The results show that the growth in process efficiency can be attributed to a dramatic increase in melting efficiency whereas the energy coupling efficiency is only moderately increased. Thus, the synergistic effect is mainly caused by secondary mechanisms that change the energy usage inside the workpiece while direct interactions between the two heat sources can be excluded as a reasonable cause for increased process efficiencies. It is concluded that the different sizes of the heat sources change the heat and mass flow positively and consequently lead to a higher performance level.
