Development of residual operational deflection shape for crack detection in structures

• Use of higher harmonic components of exciting frequency generated due to crack breathing.
• Operational deflection shape (ODS) at the exciting frequency and its higher harmonics.
• Proposal of novel and innovative Residual ODS (R-ODS) for crack detection.

Excitation of a cracked structure at a frequency always generates higher harmonic components of the exciting frequency due to the breathing of the crack. In this paper, the deflection of cracked structures at the exciting frequency and the second harmonic component is mapped by a new method based on the operational deflection shape (ODS) for the purpose of crack detection. While the ODS is helpful in understanding dynamic behaviour of structures and machines, it is not always possible to determine the location of cracks in structures or machines based on the ODS itself. Therefore, a new concept called residual ODS (R-ODS) has been defined for crack detection in beam-like structures. This paper presents the details of the proposed method and its results when applied to numerical and experimental examples.