Damage Detection in Satellite Bolted Joints

To overcome current limitations of satellite operation timelines, Operationally Responsive Space (ORS) satellites are being developed for rapid configuration and assembly. Time spent on flight qualification tests aimed at assembly verification and launch vehicle integration must be reduced to less than a week. Structural health monitoring (SHM) is seen as a possible avenue for real-time assessment of satellite integrity and qualification before launch. Embedded ultrasonics and magneto-mechanical impedance (MMI) were considered as potential candidates for diagnostics of critical system elements. Piezoelectric wafer active sensors in conjunction with an acousto-elastic SHM were used for assessment of aerospace structures with bolted joints. In the presented analysis, the acousto-elastic behavior of the joint was used as an indicator of structural integrity. Experimental results show changes in the nonlinear response of joints as a result of differing bolt torque. Localization potential of the acousto-elastic technique was demonstrated in a complex structure analogous to a typical satellite panel. The MMI method has shown utility in assessing condition of bolted joints in thin plates and a satellite structure. Experimental data reveal changes in magnitude and position of impedance peaks induced by the difference in structural loads applied to the joint. It is suggested that both the acousto-elastic and MMI methods have indicated possibilities for detecting and characterizing damage in satellite bolted joints.