Yee and Tsuei (1989) developed the Modal Force Technique (MFT) as a tool for component synthesis. The approach utilizes the frequency response functions at connecting joints to predict the dynamical behavior of a synthesized system. The main difference between the MFT and the traditional impedance modeling approach is that no inversion of the frequency response functions is required for the MFT, which makes the Model Force Technique more efficient. The other major feature is that the Modal Force matrix of the synthesized system equation contains the information of both the substructure and the system modes. To determine the natural frequency and the damping of a complex mode based on the frequency response functions, the Extended Complex Mode Indication Function (Extended CMIF) technique was developed. It performs the singular value decomposition (SVD) of the Modal Force matrix at each spectral line. The peaks of the singular value plot indicate the location of the substructure modes, while the anti-peaks show the location of the system modes. This approach is simple, straightforward and can be efficiently implemented to identify complex modes.

Issue Section:
Research Papers
Topics:
Damping, Frequency response, Modeling
1.
Allemang, R. J., 1980, “Investigation of Some Multiple Input/Output Frequency Response Function Experimental Modal Analysis Techniques,” Ph.D. Dissertation, Department of Mechanical and Industrial Engineering, University of Cincinnati, OH 45221-0072.
2.
Crowley, J. R., Klosterman, A. L., Rocklin, G. T. and Void, H., 1984, “Direct Structural Modification Using Frequency Response Functions,” Proceedings of the 2nd International Modal Analysis Conference, pp. 58–65.
3.
Dowell
E. H.
,
1972
, “
Free Vibrations of an Arbitrary Structure in Terms of Component Modes
,”
ASME Journal of Applied Mechanics
, Vol.
39
, No.
3
, pp.
727
–
732
.
4.
Dowell
E. H.
,
1980
, “
Component Mode Analysis of Nonlinear and Nonconservative Systems
,”
Transactions of the ASME
, Vol.
47
, pp.
172
–
176
.
5.
Jara-Almonte, J., and Michell, L. D., February 1989, “A Proposed Method for Enhanced Eigen-Pair Extraction Using Finite Element Methods; Part I: Theory and Part II: Application,” Proceedings of 7th International Modal Analysis Conference, Vol. I, pp. 213–226.
6.
Klosterman, A. L., and Lemon, J. R., 1969, “Building Block Approach to Structural Dynamics,” ASME Publication, VIBR-30.
7.
Lin, A. C. Y., 1991, “The Extended Modal Force Technique and Its Application,” Ph.D. Dissertation, Department of Mechanical, Industrial and Nuclear Engineering, University of Cincinnati, OH 45221-0072.
8.
Shih
C. Y.
,
Tsuei
Y. G.
,
Allemang
R. J.
, and
Brown
D. L.
, October
1988
, “
Complex Mode Indication Function and its Applications to Spatial Domain Parameter Estimation
,”
Journal of Mechanical Systems and Signal Processing
, Vol.
2
, No.
4
, pp.
367
–
377
.
9.
Tongue
B. H.
, and
Dowell
E. H.
, “
Component Mode Analysis of Nonlinear, Nonconservative Systems
,”
Transactions of the ASME
, Vol.
50
, pp.
204
–
209
.
10.
Tsuei
Y. G.
,
Yea
E. K. L.
, and
Lin
A. C. Y.
, October
1991
, “
Physical Interpretation and Application of Modal Force Technique
,”
The International Journal of Analytical and Experimental Modal Analysis
, Vol.
6
, No.
4
, pp.
237
–
250
.
11.
Yee
E. K. L.
, and
Tsuei
Y. G.
, August
1989
, “
A Direct Component Modal Synthesis Method for System Dynamic Analysis
,”
AIAA Journal
, Vol.
27
, No.
8
, pp.
1083
–
1088
.
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