Dynamic thermal tomography based on continuous wavelet transform for debonding detection of the high silicon oxygen phenolic resin cladding layer

Photothermal diffusion-wave imaging and thermal tomography are promising techniques for the analysis of debonding detection of the solid-propellant missile engine. In this paper, the dynamic thermal tomography based on continuous wavelet transform (CWT-DTT) was introduced to detect the defect and reconstruct the 3D (three-dimensional) visualization of the high silicon oxygen phenolic resin cladding layer. The basic principle of CWT-DTT and the tomography processing were described. Moreover, 3D thermal wave model stimulated by pulse signal was developed. The relationship between the SNR of the feature image and the scale factor of CWT was analyzed. The tomography experiment of cladding layers with simulated flat bottomed holes (FBHs) defects by CWT-DTT was carried out. The experimental results demonstrated that the measuring depth of all FBHs has a good agreement with the actual depth. Therefore, the research on CWT-DTT is of significant importance to quantitative evaluation the quality of the high silicon oxygen phenolic resin cladding layer.