Airframe active vibration-based damage detection and localization

The development of damage detection, localization and automation techniques is crucial for the successful integration of structural health monitoring technologies in rotorcraft. This study focused on the development of a nonlinear vibration spectroscopy based damage detection and localization method. A progression of damaged joint conditions was created in a prototypical stiffened aluminum plate test bed. Active vibration sources were used to excite the structure, and strain sensor rosettes were used to measure the nonlinear vibration responses induced by the damage. Using a systematic approach, response strain amplitudes were processed at the nonlinear frequency components, and the position of the damage was estimated based on maximum principal strain angle calculations from three strain rosette nodes. Accurate damage localization results were obtained for each damage condition, using relatively low force levels. Effective high frequency excitation for each localization result depended on the damage size and damping present in the system. Edge damping and losses due to sound radiation appeared to affect the localization scheme by reducing energy transmission at some frequencies, as well as reflections from the boundaries. Using developed data processing and automation routines, the technique showed promise for translation to real airframe structures.