Rapid detection for the surface and hidden crack of solid propellant motor charge using laser arrays scanning thermography (LAsST)

Laser arrays scanning thermography (LAsST) was introduced to detect the surface and hidden cracks of solid propellant motor charge. A series of simulated surface cracks of solid propellant charge was prepared and detected by LAsST. The thermal-wave response signal is reconstructed by truncation pseudo-static matrix reconstruction (TC-PSMR), and then, the thermal image sequence similar to the impulse response is reconstructed. The principle of characteristic extraction algorithms [such as Fast Fourier transform (FFT), principal component analysis (PCA), and partial least squares regression (PLSR)] are introduced and employed to obtain the feature images from the thermal-wave response. The morphological matrix is used to denoise the processed image. The experimental results demonstrated that the defects of the PLSR image and FFT phase image are more obvious, and the image noise after morphological matrix processing is significantly reduced. Meanwhile, the LAsST approach can enable rapid detection for the surface and hidden cracks of solid propellant motor charge.