This paper presents an experimental investigation into the detectability of higher-order harmonics induced by breathing cracks and their suitability as robust crack-sensitive features. Two experimental campaigns are conducted: f irst on a laboratory-scale beam under two excitation configurations (tip excitation via an electromagnetic shaker and base excitation), and subsequently on a full-scale railway wheelset axle tested under rotational bending. The results demonstrate that crack-induced higher-order harmonics can be captured through both strain and acceleration measurements, even at locations remote from the crack. Building on these observations, a recently proposed crack identification approach based on Higher-Order Transmissibility is implemented and experimentally validated. The method is shown to successfully localize cracks corresponding to depths as small as 3–5% of the axle diameter. Finally, the study highlights that higher-order harmonic contamination, primarily originating from the excitation system, may affect identification accuracy, underscoring the need to account for input nonlinearities in practical implementations.
Naghizadeh et al. (Tue,) studied this question.