Linear and Nonlinear Methods for Detecting Cracks in Beams

This paper presents experimental results from the vibration of a polycarbonate beam containing a crack that opens and closes dudng vibration. Several techniques were employed to detect and locate the crack making use of the nonlinearity. “Harmonic mode shapes” proved to be more sensitive to damage than conventional mode shapes. Instantaneous f requency and timefrequency methods also showed clear signatures for the crack. The results indicate that nonlinearities may provide increased capabilities for structural damage detection and location.