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Brouwers E.W.,Boeing Company | Zientek T.A.,Boeing Company | Centolanza L.R.,Aviation Development Directorate ADD
Annual Forum Proceedings - AHS International | Year: 2015

Rotor design is a compromise between hover and cruise flight. A key design variable in rotor design is the twist distribution. New rotorcraft designs require increases in hover efficiency in order to meet demanding future mission requirements. Highly twisted rotors provide improved hover performance however; also generate higher forward flight blade loads, vibratory fixed frame hub loads and ultimately fuselage vibrations. Non-linear tip twist distributions also enable hover performance improvements, but may not suffer the same forward flight loads and vibration penalties as a rotor with a high linear twist rate. In order to quantify these effects and differentiate these two approaches, testing was performed in the Boeing V/STOL Wind Tunnel (BVWT) with three rotor sets. The rotor sets differed only in twist distribution, but had otherwise similar planform, airfoils and property distributions. This paper summarizes the impact of twist on hover and cruise performance, blade loads and fixed frame vibrations on edgewise rotors. Source

Bouzakis K.-D.,Aristotle University of Thessaloniki | Bouzakis K.-D.,Fraunhofer Institute for Production Technology | Charalampous P.,Aristotle University of Thessaloniki | Charalampous P.,Fraunhofer Institute for Production Technology | And 8 more authors.
Surface and Coatings Technology | Year: 2015

During the Future Advanced Rotorcraft Drive System (FARDS) program, the Aviation Development Directorate (ADD), Aviation Applied Technology Directorate (AATD), Bell Helicopter Textron Inc., University of Toledo and the Aristotle University of Thessaloniki worked together to perform bearing coating tests. The mechanical properties of the DLC coating and its steel substrate were determined via nano-indentations and a FEM supported evaluation of the obtained results. The coating fatigue and adhesion were quantified by perpendicular and inclined impact tests respectively, coupled with appropriate finite element method (FEM) calculations. The inclined impact tests were conducted under lubricated conditions for avoiding abrasion caused by sliding friction on the coated surfaces. In this way, the coating fatigue failure during this test was mainly affected by the impact load, the material's properties and the film adhesion. The effects of these factors on the coating fatigue failure were described via an iterative FEM supported method. Using this method, the coating adhesion was estimated taking into account the exercised impact loads and the determined material properties. © 2015 Elsevier B.V.. Source

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