Abstract
Modern experimental modal analysis (EMA) methods provide a number of modal parameter solutions based upon different models, different model orders and different numerical processing of the redundant data and/or results. Evaluation of the modal parameter solutions provides a way of obtaining a single unique set of modal parameters that best represents the measured experimental data. The early portion of this chapter is a review of some of the experimental modal analysis (EMA) methods covered in detail in Chap. 10, “Experimental Modal Analysis Methods” in this handbook. This is followed by presenting a number of numerical tools that are used in connection with the EMA methods to evaluate and validate the number of modal parameters that can be estimated from a multiple input, multiple output (MIMO) set of measured data. Some tools like complex and multivariate mode indication functions (CMIF and MvMIF) can be used to determine the model order and/or number of modal frequencies that can be estimated from the experimental data. These tools can be applied independent of the EMA method that is used and are particularly useful when close or repeated modal frequencies are present in the experimental data. Additionally, various consistency diagrams, pole surface plots and modal parameter clustering methods are defined that become part of, and enhance, the EMA method used to estimate the modal parameters. Finally, the last portion of this chapter overviews methods that are primarily post processing tools to evaluate and validate the modal parameters that have been estimated. Methods include techniques for normalizing, conditioning and presenting the modal vectors, like the modal vector complexity plot (MVCP) along with techniques for using the estimated modal vectors to estimate other functions like the enhanced frequency response function (eFRF) which can be used to validate the physical validity of the estimated modal vectors. Orthogonality of modal vectors along with consistency of modal vectors, as measured by the modal assurance criterion (MAC), also falls into this category of evaluation and validation tools that are applied after the modal parameters have been estimated. The chapter finishes with a brief example of how several of the evaluation and validation tools can be combined into an autonomous modal parameter estimation method.
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Allemang, R.J., Phillips, A.W. (2022). Experimental Modal Parameter Evaluation Methods. In: Allemang, R., Avitabile, P. (eds) Handbook of Experimental Structural Dynamics. Springer, New York, NY. https://doi.org/10.1007/978-1-4614-4547-0_12
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