Ultrasonic phased array virtual source phase shift migration imaging of curved multilayer components

The total focusing method (TFM) represents an advanced post processing technique in phased array ultrasonic testing. However, the commonly used ray-tracing TFM is time consuming when calculating the refraction points in complex curved multilayer components. To enhance imaging efficiency while maintaining high imaging quality, this research proposes a virtual source extended non-stationary phase shift migration (VSENPSM) algorithm specifically designed for curved multilayer components. The proposed method enhances the emission energy by utilizing virtual sources, of which the number of elements is optimized through non-paraxial approximation multivariate Gaussian acoustic field simulation. Then the transmission matrix is reconstructed based on virtual source theory and extrapolated to various depths, achieving image reconstruction through cross-correlation with the reception matrix. Automatic image denoising is realized by integrating principal component analysis (PCA) with a fast and flexible denoising network (FFDNet), significantly enhancing spatial resolution and contrast resolution. The verification was performed on side-drilled holes in aluminum alloy, copper alloy and aluminum-steel explosive welding test blocks. Results show that the proposed FFDNet-VSENPSM algorithm achieve superior signal-to-noise ratio and exhibit over 6 times improvement in computational efficiency compared to the virtual source TFM (VSTFM) algorithm. This method provides a valuable reference for ultrasonic testing of curved multilayer components, demonstrating broad application prospects in industrial non-destructive evaluation.