A study of COMSOL-based array laser ultrasound defect detection signal

An array laser ultrasound method for the detection of air holes in aluminium blocks is proposed. A two-dimensional transient laser ultrasound force-solid coupling model is established under the simulated thermoplastic mechanism using the finite element method, and the ultrasonic signal is focused by an array of sixteen cells in combination with the array technique, considering the effect of different sizes of the pores in the aluminium block model on the transmitted ultrasound signal; meanwhile, the acquired ultrasound transmission signal is analyzed in the conventional frequency domain (fast Fourier transform) as well as in the time-frequency analysis (short-time Fourier transform, continuous wavelet transform and Hilbert-Huang transform) and comparison. The results show that the array laser ultrasound model has a significant improvement for the ultrasonic signal amplitude, the amplitude and spectrum of the transmitted ultrasonic signal are different for different stomatal sizes, and the centre frequency of the ultrasonic signal is more obvious when the stomatal size is larger. The Hilbert-Huang transform is better for the ultrasonic signal processing results of different stomatal sizes among the three time-frequency analysis methods.