Experimental verification of intelligent fault detection in rotor blades

The common idea of examining damage in mechanical structures through vibrat ional methods is analysed from a practical point of view. The method presen ted is based on a straightforward time domain approach and utilizes respons e signals in their purest form. Error magnification related to computationa l manipulations, e.g. FFT, or similar procedures, is avoided. The fact that the proposed method is straightforward and involves a minimum of signal pr ocessing, renders the approach attractive for use in practice, as an intell igent fault detection system. The method was applied to a clamped section of a helicopter rotor blade. Da mage was induced by a mass increase (locally added weight) and a mass reduc tion (holes drilled into the structure), respectively. The experiments show that minimal effects on fundamental eigenfrequencies are reliably detectab le without any a priori knowledge of the structure. A series of measurement s with damage locations changed successively demonstrates nicely the effect s on natural frequencies. In obtaining this result it became apparent that every case study exhibited its own individual vibrational signature which i s very desirable in a health-monitoring environment.