A novel non-destructive testing method based on local contact stiffness detection

摘要

We proposed a novel non-destructive testing (NDT) method using the local contact stiffness (LCS) as the identification parameter, which is detected by a homemade NDT system containing a self-exciting and self-sensing piezoelectric unimorph cantilever. When the cantilever is pressed in contact with a testing sample, the LCS of the sample can be obtained by tracking the contact resonance frequency of the cantilever-sample system. Finite element analysis shows that LCS is fairly sensitive to typical subsurface defects including voids, cracks, inclusions, and delamination. Experimental investigations using our homemade system indicate that this LCS-based NDT method is very effective in detecting the above-mentioned defects, especially in thin-wall structures. The LCS detection sensitivity is specially analysed and it is found that the stiffer the sample is, the stiffer the cantilever is required. We also examined the delamination detection limit and the practical lateral resolution, which are finalized to be about 2mm and better than 0.5mm, respectively. The proposed LCS-based NDT method can be regarded as a sensitive palpation method, which is very promising for subsurface defects detection in both industrial and medical diagnosis.