Processing of Lamb Wave Signals

Substantially dependent on signals captured by a sensor or sensor network, the accuracy and precision of a Lamb-wave-based damage identification approach is largely subject to the processing and interpretation of signals. Captured Lamb wave signals carry comprehensive information as to interference existing in the path of wave propagation, such as damage in the medium. All the transducers described in Chapters 3 and 4 would be able to capture Lamb wave signals, although their efficiency and precision varies. Theoretically, some changes, more or less, always occur in the captured signals when damage exists. The key is to correctly tease out these changes and then associate them with particular variations in damage parameters (e.g., presence, location, size and severity). It sounds straightforward, but many challenging problems complicate this process, because of the existence of multiple wave modes, dispersion, mode conversion, superposition of scattered waves from structural boundaries or irregularities (e.g., joints, stiffeners and openings), broadband noise and other features.