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The ultrasonic-assisted drilling (UAD) process is a technology that applies ultrasonic vibrations in the feed direction of the drill to improve drilling conditions and productivity. In recent years, UAD has been the subject of extensive research due to its advantages over the conventional drilling (CD) process, these being reported as thrust force and torque reduction, burr height reduction, improvements in surface roughness, and hole accuracy. The results of the research also showed that these benefits do not necessarily equally occur for all drilling conditions but can vary with machining and ultrasonic conditions. In particular, it is found that the drill vibration amplitude is a key factor in determining UAD benefits. However, a critical difficulty is that the all-important matter of the drill vibration amplitude at the point of material engagement, the so-called "down-the-hole" amplitude, is not known due to inaccessibility. This difficulty, not faced, for example by the ultrasonic-assisted turning (UAT) process due to its visual access, has prevented measurement of load effects on UAD, as well as verification of analytical models of the process. In this study, a technique to measure the effect of load on drill vibration amplitude during UAD is presented. The technique is based on examining the surface of the drilled hole, where minute, oscillatory traces of the vibrating drill tip are found that correspond to drill tip vibrational amplitude. This data, when coupled with in-process laser vibration measurements at the drill chuck, as well as no load amplitude measurements, permit the effects of load on vibration amplitude to be determined. Results have shown that drilling loads cause measurable reductions in drill vibration amplitude and must be accounted for in UAD procedures. [ABSTRACT FROM AUTHOR]

Coastal environment with high interaction between nature and societies is subject to multi-hazard interaction such as landslides, flood or cliff retreat. These territories are characterized by numerous elements at risk located in valley bottoms, front sea or at the outlets of small dry watershed. The aim is to quantify the potential consequences of EaR by integrating multiple hazards exposure at various scale analyses. To quantify the element at risk, three steps have been required. First, an initial rank has been attributed to each class of element at risk at three different scales analysis. Second, the potential consequences are weighted according to environmental dimension. Third, the consequences are combined with a linear combination of criteria in GIS environment. At medium-scale analysis, element at risk highlighted is built-up areas, national road, railway, lifeline and urban centers. At large-scale analysis, consequences concern any kind of house, apartment and complex located on multiple exposure areas. At local scale, consequences concern buildings located on multiple exposure areas with one floor in mixed materials and built after 1980. Thus, this method proposes an approach with multiple scales analysis and by integrating multiple exposure areas to quantify potential consequences. With the environmental dimension in element at risk analysis, it is an intermediate step to traditional risk analysis and, more specifically multirisk analysis without considering in this case the spatial and temporal dimension of hazards. [ABSTRACT FROM AUTHOR]

The ultrasonic-assisted drilling (UAD) process is being developed due to its apparent advantages over the conventional drilling (CD) process in terms of thrust force and torque reduction and improvements in surface finish and hole accuracy. However, as with CD, heat generated during UAD might affect tool life, including damage to the cutting edges of the drill. The research reported here has two main objectives: (1) finding the best technique to measure temperatures in UAD, and (2) measure the effect of ultrasonic vibrations in heat generated in UAD. In this paper, two scenarios are used to examine five temperature measurement techniques, these being embedded thermocouples in the material, infrared (IR) sensor, IR camera, and embedding thermocouples in the drill cooling channels and surface thermocouples. It is found that embedding thermocouples in the drill cooling channels is the best and most reliable technique for measuring temperature in UAD. This method is then used to investigate the effects of ultrasonic vibrations on heat generated in UAD of aluminum 6061, alloy steel 4340, and stainless steel 316. The effect of ultrasonic vibrations on thrust force is also studied in this investigation. [ABSTRACT FROM AUTHOR]

The ultrasonic-assisted drilling (UAD) process is a technology which applies high frequency vibrations (>20 kHz) at amplitudes of 2-20 μm in the feed direction to the drill tip in order to improve machining conditions and productivity. Past work in this field is reviewed, noting the valuable foundation provided by laboratory-based research systems. This work is aimed at the development of a robust UAD module, fully compatible with computer numerical control (CNC) systems, and able to function in a production environment, describing results of drilling tests on 4340 steel. The UAD module, designed using FEA methods, with a 16- mm carbide drill, attached by shrink fit, is used to study the effects of ultrasonics on thrust force, torque, surface quality, hole size, and the microstructure of drilled 4340 steel. In order to provide a better understanding of the performance of this module, two different test scenarios were designed and the results for each were compared with the results obtained from baseline settings for conventional drilling. The results show that ultrasonic vibrations not only can reduce the average values of thrust force and torque but also can improve the surface quality of the hole. It is also found that a major increase in productivity could be achieved by using ultrasonic vibrations. Finally, the effects of ultrasonic vibrations on hardness and microstructure of the drilled hole is assessed and the results show that high frequency vibrations do not have significant effect on dimensional accuracy or on the microstructure of the drilled holes. [ABSTRACT FROM AUTHOR]

Carrier lifetime measurements were performed on crucible-grown, float-zoned, and swirl-free float-zoned silicon single crystals after annealing up to about 1000°C. In dislocation-free, crucible-grown silicon one pronounced maximum of the carrier lifetime can be found after annealing at 450°C . This gettering effect is correlated to the appearence of numerous IR-absorption bands at 80 K. The absorption coefficients of these bands depend on the oxygen concentration of the crystals and on the annealing duration. A differing number of maxima of the carrier lifetime after annealing at various temperatures can be found in dislocation-free, float-zoned silicon. These maxima are correlated to still remaining lattice defects in the crystals such as vacancy clusters of A-and B-type. Models are presented to explain the experimental findings. [ABSTRACT FROM AUTHOR]

Single crystal lamina of potassium chlorate and potassium chloride are grown from the solution in the narrow space between two parallel glass surfaces. Electron micrographs are taken at 60 and 80 keV. The monocrystalline structure is demonstrated by the diffraction of a parallel electron beam. The exact thickness of the crystals can be determined from the subsidiary maxima within the Bragg reflections in a convergent beam pattern. Other crystals are under investigation. [ABSTRACT FROM AUTHOR]

By improvement of an earlier published preparation method for producing thin single crystals soluble in water, it is possible to determine structure and absorption potentials of some reflections of KCl and NaCl crystals by a convergent beam diffraction technique. The structure potentials evaluated on the basis of the two-beam dynamical theory are found to depend on the thickness of the crystals used. The structure potentials corrected for relativistic, thermal and many-beam effects are compared with theoretical values. The measured (220)- and (420)-absorption potentials of NaCl are in good agreement with theoretical values. Radiation damage in KCl and NaCl crystals by electron beams is observed. [ABSTRACT FROM AUTHOR]