Using of Modulated Thermography for Nondestructive Testing of Polymer Plates

Thermography is one of the new, fast and low-cost methods for nondestructive testing. In this method, the workpiece is subjected to heating under the modulated heat source, and the images of the process are stored by the thermal camera. In this research, the feasibility of this method was performed on a plastic cutter. The results showed that deeper and smaller defects are better identified in the image of the amplitude of the heat wave amplitude. It was also found that the quality of phase images is higher than the image of the domain and is less affected by the test conditions, such as asymmetric heating and light reflection. By optimizing the test conditions, the defects can be displayed with the use of domain images. Also, two different frequencies with a relatively high spacing of 0.5 Hz and 1 Hz were used to obtain a suitable frequency for the workpiece. Due to the appropriate heat transfer, lower frequency use in the test is recommended to provide a more appropriate time interval for detecting defects.