Theoretical and experimental investigation on natural frequency-based crack detection using a roving mass with rotary inertia

Experiment design:

Roving mass with adjustable rotary inertia.

Unadjustable roving mass.

The experiment set-up for the impact hammer test:

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Typical curves of the transfer function:

Data processing:

FRF magnitude and phase vs. frequency

Modal circle for extracting natural frequency and loss factor

Damping “carpet” plot

Circle-fit method

Modal testing: theory, practice and application (D. J. Ewins)