Abstract
Comparisons between one-dimensional and three-dimensional analyses are conducted systematically for advanced geometry blades, which have tip sweep, tip taper, and planform variations near the root with various materials and effects of boundary conditions in order to better understand the differences between the two approaches and the physics behind them. One-dimensional beam analysis is conducted using the rotorcraft comprehensive analysis system with variational asymptotical beam sectional analysis calculated two-dimensional cross-sectional properties. Three-dimensional finite element analysis is conducted using a commercial code MSC/Marc. Natural frequencies are calculated at various rotor rotational speeds, and the differences are quantified. There is very good agreement between the one-dimensional and three-dimensional analyses for free–free aluminum beams, even for a very short beam with beam length five times chord (). The one-dimensional analysis accurately captures the planform variation near the root for an aluminum beam. In general, the differences between the one-dimensional and three-dimensional analyses occur when there is coupling, either generated from geometry (tip sweep) or material (composite), especially for high-frequency modes. Without coupling, the one-dimensional analysis appears to capture free vibration characteristics of various advanced geometry beams and blades reasonably well for at least the six lowest frequency modes when the beam length is greater than 10 times chord.
Published Version
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