Experimental stress analysis for the elastic bending of the pretwisted rotor blades

Abstract

Dynamic tests are performed on rotating rotor blades by applying strain gages near the root ends of blades. The model blades have linear pretwist and constant cross-section along the blade span. The steady and vibratory bending strains and flapwise bending frequencies are measured for the rotating blades by changing the blade angle of attack and rotating speed. Measured results led to the following conclusions. The vibratory stresses are dependent upon the external flow characteristics. And the natural frequencies are affected not by setting angle but by rotational speed strongly. The measured frequencies are compared with the solution of Rayleigh-Ritz approximation. The measured results are in good agreement with the Rayleigh-Ritz solution even for a one term approximation.