Simulation of lamb wave propagation and interaction with defects using commercially available software

摘要

Structural Health Monitoring (SHM) consists of the continuous process of damage detection in an engineering component using built-in transducers and any resultant intervention to preserve structural integrity. It is a multidisciplinary field in terms of the technology involved as well as the diverse applications. Good SHM systems are considered those that combine a high sensitivity to defects and a low density of sensors.ududUltrasonic guided waves have the ability to propagate long distances with minimal attenuation making them particularly interesting in SHM applications. Using the baseline subtraction approach, the signal from a defect free structure is compared to the actual monitoring signal in order to detect and characterize defects.ududThere are many scientific publications on low frequency guided waves for SHM purposes and the interaction between guided wave fundamental modes and defects is also well documented. There are, however, a very limited number of studies on high order modes. High frequency guided waves may enable the detection of smaller cracks relative to conventional low frequency guided waves systems. The main difficulty at high frequency is the co-existence of several modes with different velocities.ududThis study investigates the advantages of high frequency guided waves relative to low frequency to detect cracks at their initiation. Thus the scattering around a through-thickness hole is studied with a view to develop a highly sensitive SHM method.udud2D and 3D finite element models of a 305 mm × 305 mm × 1.6 mm aluminum plate were used to determine the scattering of cracks on the circumference of a throughthickness hole in the middle of the plate. Crack properties such as orientation, length and depth were studied in order to characterize the crack using the received signals. A subset of the finite element simulations was validated against experimental results. The experimental setup comprised a classic contact piezoelectric transducer bonded on the side of the plate and a laser Doppler vibrometer for the detection. Input signals centered at 100 kHz and 4 MHz were used in simulations and experiments for low and high frequency studies respectively.