Thermosonic Chladni figures for defect-selective imaging

Thermosonic patterns produced by resonant vibrations of simulated and realistic defects are experimentally observed and compared with conventional vibration Chladni figures. The patterns are interpreted on the basis of hysteretic damping model that accounts for in-plane polarization component of vibrations. The analysis and simulation results show that thermosonic Chladni figures are the patterns of dissipation of vibration energy determined by a square of the in-plane strain developed in the resonant vibrations. The difference in nodal patterns between the two types of Chladni figures is due to additional extension-compression of the material mainly in near boundary area. The contribution of various order resonance modes in single-frequency imaging is illustrated and their superposition is shown to produce a full-scale thermosonic image of a resonant defect in a wideband excitation mode.