Abstract:

During the interaction between dielectric particles and incident electromagnetic waves，Mie resonance is generated，which results in the absorption of microwave near the resonance frequency. At this time，the energy of electromagnetic field will be gathered near the dielectric particles. If there are small perturbations around the dielectric particles，such as small cracks on the reflecting surface of metal，the resonance frequency will change

obviously. The network analyzer can measure the reflection coefficient of electromagnetic wave and record the frequency change of absorption peak to obtain the information of cracks. In the experiment，cracks of different sizes are detected，and two rules can be concluded: for cracks of the same depth ( or width) ，the resonance frequency of dielectric particles decreases with the increase of crack width ( depth) ，and the change rate of resonance frequency decreases with the increase of crack width ( depth) .

Key words: dielectric particles, metal surface crack, microwave, nondestructive detection