A multibody approach with MBS SIMPACK has been used to model an isolated rotor blade. Beam models are available for BO105 and ERATO rotor for investigation, even though the focus is on BO105 with straight blade reference line to gain initial experience. The objective of the study presented in this work is to find an answer related to the question: Getting the mechanical coupling right for the flexible rotor blade with multibody dynamics? The comparison of processed BO105 fan diagrams to the comprehensive helicopter tool CAMRAD II is encouraging. In general, the generic multibody system SIMPACK seems to be capable to simulate a rotating flexible rotor blade with respect to the consideration of geometric stiffness and gyroscopic terms. Elastic couplings being of interest for a rotating flexible rotor blade comprise bending-torsion, tension-bending and tension-torsion. Here, the coupling bending-torsion is driven by mass effects in the plane of the blade cross section due to the offset between shear center and the center of gravity, whilst tension-bending and tension-torsion are activated by centrifugal force. Nevertheless, the flexible representation of the rotor blade is always limited to the structural definition within the finite element code itself. For example, the used beam model based on CBEAM and PBEAM entries in MSC.NASTRAN cannot reproduce the mechanical coupling tension-torsion and further, the beam offset definitions are not allowed with the computation of differential stiffness for the derivation of the geometric stiffness terms and need to be neglected in the related static solution. The effect of tension-torsion coupling is usually small for a conventional rotor blade, but could be included within the flexible description of SIMPACK, if provided. The comparison of natural frequencies with fan diagrams is a first step only to qualify the multibody system SIMPACK for the simulation of an elastic rotor blade model. BO105 mode shapes for nominal rotor speed are not compared to CAMRAD II reference results yet, but all information comprising the basic mode shapes from the non-rotating blade and their modal contributions and phase angles for the rotating blade is available.


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    Title :

    Using multibody dynamics for the simulation of flexible rotor blades - getting the mechanical coupling right?


    Contributors:
    Arnold, J. (author)


    Publication date :

    2009


    Size :

    7 Seiten, 6 Bilder, 5 Tabellen, 9 Quellen



    Type of media :

    Conference paper


    Type of material :

    Storage medium


    Language :

    English




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