Vibration-based structural damage detection using FRF and modal constant curvature

This paper presents a new method for locating and quantifying damage in beam-like structures based on the modal constant curvatures and natural frequency extracted from the measurements of the Frequency Response Function (FRF). The modal constant curvature is very effective for localising the damage due to the discontinuity created near the damaged zone. However, in classical vibrational measurement techniques, the discontinuity is confounded by measurement noise. To overcome these limitations, a new index is developed by normalising the curvature of the first fourth vibration mode. The new index gives a value of 1 in the damage location with the elimination of all the values that can distort the results. In order to make the index sensitive for damage depth, quantification charts are developed based on natural frequency ratios. Numerical simulations on a cantilever beam demonstrated the high sensitivity of the proposed method, with errors of under 0.4%. Experimental tests on a cantilever beam confirmed its reliability, with errors of under 3.6%. The method's low sensitivity to disturbance makes it a robust method for locating and quantifying damage in mechanical structures.