Automated calculation of the internal structure and the natural frequencies of helicopter rotor blades with regard to automated rotor blade optimization

Abstract

With regard to an automated multidisciplinary optimization process an automated modeling and calculation of the structural properties of helicopter rotor blades was aspired. For this purpose, a program for structural rotor blade modelling based on rotor blade cross-sections was developed. This process is implemented as three successive steps. First, the CAD cross-section geometry is generated on the basis of a geometry template. Based on this, a structural model is generated and the structural properties are calculated with DLR inhouse tool SaMaRA. Finally, the natural frequencies are calculated using a beam model according to Houbolt & Brooks. To investigate the internal structure of a given outer blade geometry, the sensitivity of structural parameter variations was carried out. For this purpose, a uniform shaped rotor blade based on a selected cross-sectional topology in the aerodynamic blade region was considered. The performed parame-ter study considers the effects of different parameter intervals on the structural properties and the resulting natural frequencies.