A new concept to determine the mass distribution of an active twist rotor blade

Abstract

In this paper a new method for an experimental determination of the mass distribution of rotor blades is presented. This mass distribution measurement method is developed for the testing of on active twist blades, but it is applicable to the mass property determination of any type of rotating blade. Usually X-ray computer tomography (CT) is used for non-destructive inspection, such as to find voids in composite components. In this research CT is used to get information regarding the spatial distribution of mass in a rotor blade. The CT-analysis of an active twist rotor blade and the implemented determination of the mass distribution are presented in this paper. Image reconstruction due to X-ray computer tomography makes possible to obtain a cross-section image of the rotor blade. Each pixel of this image has a CT-Number which is proportional to the attenuation coefficient of the material forming the blade. Due to the fact that the attenuation of X-ray is characteristic for each material, it is theoretically possible to correlate CT-Numbers with material properties. This method is ‘‘quasi’’-experimental because the attenuation coefficient for each pixel is experimentally determined and then densities are assigned to these pixels. Once that correlation is done, calculating mass properties such as total mass, mass per length, local center of mass and local moment of inertia for each cross section is possible.