Non-contact Measurement Techniques for Structural Health Monitoring

The application of 3D scanning laser vibrometry for visualising stress wave propagation in a specimen with a non-surface penetrating defect is presented. The results support the need for a good understanding of the 3D velocity fluctuation measurements to provide a good insight of the propagation of the stress wave over a given region. It will be shown that a full knowledge of the velocity field will facilitate an understanding on the interaction of the various wave modes with the defect in the structure. For the purpose of this paper, a flat aluminium test plate with non-surface penetrating defect will be used to illustrate the application of this form of non-contact measurement technique for this stress wave visualisation work. It will be shown that the modal content and the time-development of the incident and the scattered wave modes can be evaluated with this type of measurement technique.