Engineering structures are often subjected to fatigue loads. Monitoring the process of fatigue crack propagation as well as estimating the remaining useful life (RUL) of a structure is thus essential to prevent catastrophic failure while minimizing earlier-than-required replacement.
Autonomous, real-time, remote monitoring becomes possible with the use of smart piezoelectric transducers, alleviating the shortcomings of conventional nondestructive inspection techniques. For instance the electromechanical impedance (EMI) technique is known for its ability in damage detection and characterization.
This chapter presents a series of investigative studies to evaluate the feasibility of fatigue crack monitoring and estimation of RUL using the EMI technique. Experimental tests were conducted to study the ability of EMI technique in monitoring fatigue crack in one-dimensional laboratory-sized aluminum beams subjected to mode I fatigue loading. The experimental results demonstrated that the EMI technique is very sensitive to monitoring fatigue crack propagation in all three stages. A proof-of-concept semianalytical damage model for fatigue life estimation has been developed by incorporating the linear elastic fracture mechanics theory into the finite element model. The prediction of the model matches closely with the experiment, suggesting the possibility of replacing costly experiment in future.