Detection, localization, and sizing of a structural flaw in a beam based on forced response measurements – An experimental investigation

An experimental investigation has been carried out to establish an identification procedure for the detection, localization, and sizing of a flaw in a beam based on forced response measurements. The experimental setup consisted of a circular beam, which was supported by rolling bearings at both ends. The specimen beam had an artificial open flaw (transverse slit). A harmonic force of continuously varying frequency was applied to excite the beam specimen. The actual force applied to the beam was measured by a piezoelectric force transducer. Displacement responses in the horizontal and vertical directions were measured at various locations of the beam by using four proximity sensors. Time domain signals from transducers were sampled and stored in a personal computer by using a multi-channel data acquisition system. The stored data were further processed to a convenient form as required by the proposed flaw identification algorithm in frequency domain. The finite element model of the flawless beam was updated by taking the support flexibility of the beam into consideration. Resonant frequencies, amplitude, and phase information of responses were utilized in the identification algorithm for subsequent estimation of flaw parameters. Estimated flaw parameters have been found in good agreement with the measured data in different frequency ranges.