Ultrasonic Wave-based Structural Health Monitoring
Fangsen Cui, Institute of High Performance Computing, A*STAR
Structural health monitoring (SHM) plays an important role in ensuring operational safety of aerospace structures. Targeting at some common types of defects such as cracks around fastener holes, disbond in adhesive bonded joints, and cracks and delaminations in composite structures, ultrasonic wave (UW)-based SHM numerical methods are developed with advanced sensing techniques. In the first part, directed UW-based shearography is proposed to focus energy to the suspected areas using phased array transducers. The corresponding intense vibration induced by the UW-defect interaction can be characterized by the surface displacement. By illuminating the monitored structural surface with laser, shearograms from surface displacements can reveal both surface and subsurface cracks, as well as delamination of composite structures. In the second part, ultrasonic guided wave (UGW) is used for SHM of disbond in adhesive bonded joints. Compared with conventional ultrasonic bulk wave for nondestructive evaluation, UGW bears the advantages of large inspection area coverage, high sensitivity to defects, easy access to hidden parts, and integration capability with monitored structures. Lightweight and flexible comb transducers made of polyvinylidene fluoride (PVDF) are inserted into the adhesive layer of adhesively bonded joint, to generate and receive UGW signals. It is demonstrated that by selecting UGW with a specific mode-frequency combination, disbond can be in situ monitored with the change of UGW flight time.
Fangsen Cui, Institute of High Performance Computing, A*STAR
Structural health monitoring (SHM) plays an important role in ensuring operational safety of aerospace structures. Targeting at some common types of defects such as cracks around fastener holes, disbond in adhesive bonded joints, and cracks and delaminations in composite structures, ultrasonic wave (UW)-based SHM numerical methods are developed with advanced sensing techniques. In the first part, directed UW-based shearography is proposed to focus energy to the suspected areas using phased array transducers. The corresponding intense vibration induced by the UW-defect interaction can be characterized by the surface displacement. By illuminating the monitored structural surface with laser, shearograms from surface displacements can reveal both surface and subsurface cracks, as well as delamination of composite structures. In the second part, ultrasonic guided wave (UGW) is used for SHM of disbond in adhesive bonded joints. Compared with conventional ultrasonic bulk wave for nondestructive evaluation, UGW bears the advantages of large inspection area coverage, high sensitivity to defects, easy access to hidden parts, and integration capability with monitored structures. Lightweight and flexible comb transducers made of polyvinylidene fluoride (PVDF) are inserted into the adhesive layer of adhesively bonded joint, to generate and receive UGW signals. It is demonstrated that by selecting UGW with a specific mode-frequency combination, disbond can be in situ monitored with the change of UGW flight time.
