PSI - Issue 37

Aleksey Mironov et al. / Procedia Structural Integrity 37 (2022) 241–249 Aleksey Mironov, Pavel Doronkin / Structural Integrity Procedia 00 (2019) 000 – 000

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7. Discussions Analytical and experimental estimates of modal parameters change caused by seeded faults do not coincide however, it does not contradict. From one side, external factors (wind gusts) and own “noise” (electronic interference of the system) define the resolution threshold ( MPVI =0.8) of the actual SHM system of rotating blade in comparison with zero of simulated one. From other side, the estimated stress difference between two simulated faults and the difference between MPVI of the operational blade are around 1% both. Such results of research study confirm the sensitivity of OMA based SHM system to limited size damage and the opportunity to demonstrate it using the The study of damage identification of rotating blades using OMA techniques shows the issues to be overcome. Above issues includes problems of vibration measurements of rotating blades, the OMA assumption breach, operating and random factors influence and system’s resolution. The measurement problem is solved within the experimental SHM system built in operating helicopter-demonstrator. The OMA techniques added by the MP approach allow finding the optimal testing mode of blades , for the procedure of data development and for definition of the system’s sensitivity. The research stage of modal properties of the composite blade confirms sensitivity of OMA based monitoring system for detection of limited size faults in rotating blades. There are some novelties in methodological and technical solutions in this study. The piezo-films applied as dynamic deformation sensors do not require individual adjustment and allow effective technical solution of the board measurement system. Such application of deformations rather than displacements (accelerations) is also the novel for structural monitoring in aviation. Thanks to the above, the number of measurement channels was reduced several times than the number of sensors. Both the application of deformation sensors and the reduction of required measurement channels cut the cost of on-board equipment, encouraging the practical use of SHM systems on the helicopters. Application of MP approach for the SHM of rotating blades allows considering the influence of external factors on modal properties. Both technical and methodical solutions checked in the study allows practical application of structural monitoring to operating structures. Further research will go in two ways. The first considers more tests with seeded faults in helicopter’s structures to study the dependence functions and to estimate the diagnostic sensitivity of the MP to seeded faults scale. The second way will aim for automation of modal identification procedures and modal assurance criteria computation stages. Acknowledgements The paper uses materials related to the research project “The complex demonstrator of advance vibration diagnostic technology of an aircraft” within „Energy and Transport Competence Center” in cooperation wi th Central Finance and Contracting Agency of Latvia (1.2.1.1/18/A/001). References Abdelghani M., Gourst M.,. Biolchini T. (1999). On-Line Modal Monitoring of Aircraft Structures under Unknown Excitation. Mechanical Systems and Signal Processing, 13(6), 839-853. doi:10.1006/mssp.1999.1248. Brincker, R., Zhang, L.M. and Anderson, P. (2000). Modal Identification from Ambient Response using Frequency Domain Decomposition. Proc. of the 18th IMAC. San Antonio, TX, USA. Böswald, M., Schwochow J., Jelicic G., Govers Y. (2017). New Concepts for Ground and Flight Vibration Testing of Aircraft Based on Output Only Modal Analysis. IOMAC 2017 - 7th International Operational Modal Analysis Conference, Ingolstadt, Germany. Ihn J-B, F-K Chang and H. Speckmann (2001). Built-in Diagnostics for Monitoring Crack Growth in Aircraft Structures. Proc. of 4th Internat. Conf. on Damage Assessment of Structures (DAMAS) Cardiff/Wales, Key Engineering Mat., Vols. 204-205, 299-308. Janeliukstis, R., Mironovs, D. Smart Composite Structures with Embedded Sensors for Load and Damage Monitoring – a Review. Mech Compos Mater 57, No. 2, 131 – 152 (2021). operating helicopter-demonstrator. 8. Conclusions and further works