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Nonlinear Guided Waves for Fatigue Crack Detection in a Steel Joint

YU LEE, YE LU, WING KONG CHIU, IMAN SALEHI

Abstract


Higher capacity and faster rail transport systems are in demand due to population and economic growth which imposes a greater possibility of fatigue failure in railways. This paper presents an experimental study of nonlinear guided wave-based fatigue crack identification in a steel joint subjected to tensile fatigue loadings. The steel joint is considered as a section of a railway bogie, which is a vital component of the train holding the axles, suspension and brakes, and is located at a stress concentration area of the structure. The second symmetric mode (S1) of Lamb waves was selected as the input signal and excited by piezoelectric transducers which were installed on the top surface of the joint. The sensing paths were aligned perpendicularly to and at various distances away from the crack. When the waves interacted with the crack, higher harmonics were produced owing to contact acoustic nonlinearity (CAN). A nonlinear index based on the second harmonic characteristics is exploited to define the nonlinearity. The finding from this experiment indicated that there was a significant change in nonlinearity at the stage of crack initiation and crack growth. Therefore, nonlinear guided waves offer the feasibility in detecting fatigue crack in steel joint.


DOI
10.12783/shm2019/32178

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