TY - GEN
T1 - Numerical and Experimental Study on the Modal Characteristics of a Rotor Test Rig
AU - Heuschneider, Verena
AU - Berghammer, Florian
AU - Hajek, Manfred
N1 - Publisher Copyright:
© 2021, The Society for Experimental Mechanics, Inc.
PY - 2021
Y1 - 2021
N2 - A Mach scaled 85 kW rotor test rig for the investigation of Dynamic Stall on highly loaded helicopter rotor blades up to a diameter of 1.80 m and a tip speed up to 220 m/s is built at the Institute of Helicopter Technology, Technical University of Munich. The current state is the complete assembly of the drive train components including the engine cradle, wind tunnel adaptor, rotor shaft, and bearings as well as strain gauge load cells. To ensure a safe entry into service and operation at the nominal rotor speeds between 40 and 50 Hz, we develop a numerical finite element model of the test rig structure in order to study its dynamic characteristics. The numerical analysis results show critical eigenmodes at 44.21 and 54.98 Hz, modes 5 and 6. By means of a complementary experimental modal analysis on the steel frame structure natural frequencies, mode shapes, and damping characteristics of the critical modes are identified. The measurement results for three different excitation points and their synthetization prove the identification of ten eigenmodes between 0 and 70 Hz, which mainly emerge from the wind tunnel adaptor. Modes 6 and 7 have eigenfrequencies that are in and critically close to the nominal speed range, 46.97 and 54.88 Hz. They match with the numerically calculated eigenfrequencies but show different mode shapes, as the Modal Assurance Criterion (MAC) values for the comparison of numerical and experimental model convey. As closer investigations show, the numerical eigenfrequencies have a tendency to higher values from the fifth mode onwards.
AB - A Mach scaled 85 kW rotor test rig for the investigation of Dynamic Stall on highly loaded helicopter rotor blades up to a diameter of 1.80 m and a tip speed up to 220 m/s is built at the Institute of Helicopter Technology, Technical University of Munich. The current state is the complete assembly of the drive train components including the engine cradle, wind tunnel adaptor, rotor shaft, and bearings as well as strain gauge load cells. To ensure a safe entry into service and operation at the nominal rotor speeds between 40 and 50 Hz, we develop a numerical finite element model of the test rig structure in order to study its dynamic characteristics. The numerical analysis results show critical eigenmodes at 44.21 and 54.98 Hz, modes 5 and 6. By means of a complementary experimental modal analysis on the steel frame structure natural frequencies, mode shapes, and damping characteristics of the critical modes are identified. The measurement results for three different excitation points and their synthetization prove the identification of ten eigenmodes between 0 and 70 Hz, which mainly emerge from the wind tunnel adaptor. Modes 6 and 7 have eigenfrequencies that are in and critically close to the nominal speed range, 46.97 and 54.88 Hz. They match with the numerically calculated eigenfrequencies but show different mode shapes, as the Modal Assurance Criterion (MAC) values for the comparison of numerical and experimental model convey. As closer investigations show, the numerical eigenfrequencies have a tendency to higher values from the fifth mode onwards.
KW - Experimental modal analysis
KW - Finite element model
KW - Impact excitation
KW - Modal Assurance Criterion
KW - Rotor test rig
KW - Structural dynamics
UR - http://www.scopus.com/inward/record.url?scp=85120430902&partnerID=8YFLogxK
U2 - 10.1007/978-3-030-47717-2_33
DO - 10.1007/978-3-030-47717-2_33
M3 - Conference contribution
AN - SCOPUS:85120430902
SN - 9783030477165
T3 - Conference Proceedings of the Society for Experimental Mechanics Series
SP - 315
EP - 321
BT - Topics in Modal Analysis and Testing, Volume 8 - Proceedings of the 38th IMAC, A Conference and Exposition on Structural Dynamics, 2020
A2 - Dilworth, Brandon
A2 - Mains, Michael
PB - Springer
T2 - 38th IMAC, A Conference and Exposition on Structural Dynamics, 2020
Y2 - 10 February 2020 through 13 February 2020
ER -