Manufacturing of artificial sub-surface cracks to investigate non-linear features of electro-mechanical impedance measurements

Review of Structural Health Monitoring Methods Regarding a Multi-Sensor Approach for Damage Assessment of Metal and Composite Structures

“…Advancement might yield, e.g., the inclusion of nonlinear features such as higher harmonic response, due to contact acoustic nonlinearity. This would allow limiting the possible damage types to damages that have the potential to produce higher harmonic oscillation (all types of cracks) or not [16,18,64].…”

“…SHM methods can, on the one hand, be classified into active methods, i.e., the observed structure is excited and its response to it measured (e.g., guided waves method [5][6][7][8]), and passive methods, i.e., operational loads or damage initiation directly cause the measured signal (e.g., acoustic emission [9]). On the other hand, SHM methods can also be classified as static methods, i.e., when static states are evaluated (e.g., neutral axis method [10] or electrical impedance tomography methods [11][12][13][14]), and as dynamic methods, i.e., when dynamic events are evaluated over time (e.g., electromechanical impedance method [2,[15][16][17][18]). However, damage cannot be measured directly.…”